U.S. patent application number 11/489916 was filed with the patent office on 2007-02-22 for distributed energy resources.
Invention is credited to Peter B. Evans, Steven E. Schumer.
Application Number | 20070043549 11/489916 |
Document ID | / |
Family ID | 37590761 |
Filed Date | 2007-02-22 |
United States Patent
Application |
20070043549 |
Kind Code |
A1 |
Evans; Peter B. ; et
al. |
February 22, 2007 |
Distributed energy resources
Abstract
An improved method for analyzing power systems; in particular,
power systems that may incorporate distributed energy resources
(DER), that provides a thorough determination of the potential for
network performance improvement that DER could provide, independent
of non-network benefits DER could provide. The method incorporates
an Energynet dataset simulating the power system, integrating
transmission and distribution elements together and capable of
evaluating the impacts of additions of real energy sources and/or
reactive energy sources anywhere in the network. Such energy source
additions are evaluated for their impact on a broad set of
performance measures. The specific DER projects that would realize
that potential improvement in network performance are characterized
as an Optimal DER Portfolio. Network performance improvement
attributable to the Optimal DER Portfolio is quantified in
engineering and financial terms.
Inventors: |
Evans; Peter B.; (Los Altos
Hills, CA) ; Schumer; Steven E.; (Santa Clara,
CA) |
Correspondence
Address: |
FENWICK & WEST LLP
SILICON VALLEY CENTER
801 CALIFORNIA STREET
MOUNTAIN VIEW
CA
94041
US
|
Family ID: |
37590761 |
Appl. No.: |
11/489916 |
Filed: |
July 19, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10666209 |
Sep 17, 2003 |
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11489916 |
Jul 19, 2006 |
|
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60411836 |
Sep 18, 2002 |
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Current U.S.
Class: |
703/18 |
Current CPC
Class: |
Y02E 60/00 20130101;
G06F 30/367 20200101; Y04S 40/22 20130101; Y04S 40/20 20130101;
H02J 2203/20 20200101; Y02E 60/76 20130101; H02J 3/381
20130101 |
Class at
Publication: |
703/018 |
International
Class: |
G06F 17/50 20060101
G06F017/50 |
Claims
1. A method for analyzing an electric power transmission and
distribution network for assessing impacts and benefits of
distributed energy resources (DER) for the electric power
transmission and distribution network, to provide indication of the
extent to which the transmission-level resources and
distribution-level resources impact on each other, and of the
merits of remedying deficiencies near their network locations, the
method comprising: simulating the electric power transmission and
distribution network with a mathematical model as an Energynet in
which transmission voltage-level elements and distribution
voltage-level elements are integrated within the mathematical
model; and incorporating models of distributed energy resources at
a plurality of network locations and voltage levels within the
simulated network for analyzing resultant effects.
2. A method for assessing impacts and benefits of distributed
energy resources (DER) for an electric power transmission and
distribution network, the method comprising: adding models for real
energy sources, reactive energy sources, and combined real and
reactive energy sources to modeled network locations in selected
combinations; and evaluating alternative combinations of the
additions for their ability to improve selected characteristics of
network stability, or voltage security, or reduction of real and
reactive power losses, or deferral of conventional network
modifications.
3. A method for assessing the potential impacts and benefits of
distributed energy resources (DER) for an electric power
transmission and distribution network, comprising: adding to a
network model a set of models of real and reactive energy sources
for resultant improvement in network performance, independent of
other considerations; characterizing the set of added energy
sources as a performance portfolio of individual projects for
distributed energy resources, including dispatchable demand
reduction, capacitive elements, and power generation; and
evaluating the economic value of improvements in network
performance derived from proposed projects based on their
similarity to the projects in the performance portfolio.
4. The method of claim 3, further comprising: identifying the
proposed projects that most closely resemble projects in the
performance portfolio; and selectively implementing the identified
proposed projects for their beneficial economic or environmental
impact and their beneficial performance improvement.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit under 35 U.S.C. .sctn.
120 as a divisional application of Ser. No. 10/666,209 filed on
Sep. 17, 2003, by P. B. Evans.
FIELD OF THE INVENTION
[0002] The present invention relates generally to power
transmission and distribution systems or networks, and more
particularly to such power networks that may incorporate
distributed energy resources.
BACKGROUND OF THE INVENTION
Prior Art
[0003] Distributed energy resources, or DER, may include power
generation capacity located at customer sites and/or located near
load centers. This is sometimes referred to in the art as
"distributed generation" to distinguish it from central station
generation, which is prevailing in the art.
[0004] It is increasingly understood in the art that reduction of
demand upon command from the system operator, sometimes referred to
as "dispatchable demand reduction" or load shedding, is in some
respects an alternative to adding incremental generating capacity.
The capacity, or energy source, represented by dispatchable demand
reduction is, by definition, located at customer sites.
Dispatchable demand reduction thus may be considered DER.
[0005] DER may also include the capacitors, reactive energy sources
that provide reactive power capacity, and that are located at
various points within either the transmission system or the
distribution system as part of conventional practice in the art. It
should be noted that in this description we use the term capacity
with two meanings depending on context. Capacitors may have a
certain capacity value or capicitance and energy sources provide
added capacity to the network, either as real power, e.g., a
generator, or reactive power, e.g., a capacitor bank.
[0006] The potential for distributed energy resources to augment
traditional central-station power generation approaches is widely
discussed within and outside the power industry. However, the prior
art includes no methodology that thoroughly assesses and values the
potential benefits of DER. Specifically, current methods fail to
thoroughly assess and value the potential benefits of DER to
transmission or distribution (T&D) systems themselves. Such
benefits are to be considered distinct from potential benefits of
DER to customers or the environment.
[0007] Making Connections: Case Studies of Interconnection Barriers
and their Impact on Distributed Generation Projects, Alderfer,
Eldrige, and Stars, NREL/SR-20028053, May 2000, is one of many
references in the art that acknowledges the potential for DER (in
this case power generation at the energy customer's site) to
provide benefits to customers. Such customer benefits may include
increased reliability or reduced energy costs. Making Connections
also acknowledges the potential for DER to provide benefits for the
environment. These environmental benefits might include production
of electric power at higher levels of efficiency (thus, reduced
fuel use) or reduced environmental impacts through the use of
advanced or renewable technologies.
[0008] However, Making Connections makes no reference to the
potential for DER to provide benefits to T&D systems per se,
over and above the potential benefits of DER for customers and the
environment.
[0009] Where impacts of DER on T&D systems are considered,
current methods do not provide a means to assess the potential
benefits of DER to such T&D systems.
[0010] PIER Strategic Program--Strategic Distributed Energy
Resources Research Assessment Interim Report, Arthur D. Little,
P600-01-016, August 2001, considers grid impacts of DER at length.
However, this report considers grid impacts of DER as a looming
problem that may have to be dealt with if the level of penetration
of DER is great enough. The report's literal characterization of
the DER grid impacts issue is "Would a high penetration of DER have
an adverse impact on the T&D system?" The report does not
anticipate the affirmative use of DER as a means to improve
performance of the T&D network.
[0011] Where DER is considered to have potential benefits for
transmission and distribution systems, current methods fail to
provide a thorough assessment and valuation of the potential
benefits.
[0012] "The Energy Web," by Steve Silberman, Wired Magazine, Sep.
7, 2001, describes an "Energy Web" with diversified resources close
to customers managed by intelligent agents throughout the network.
This infrastructure would have less environmental impact and
provide more choices to customers. Silberman certainly implies that
there could be grid benefits as well. However, Silberman offers no
means for thoroughly determining what those benefits might be.
[0013] There is a need for a method to thoroughly assess and value
the potential benefits of DER to transmission or distribution
(T&D) systems themselves. Such a method should be analytically
defensible. Also, such a method should quantify such benefits
objectively, distinct from potential benefits of DER to customers
or the environment.
[0014] The lack of an analytical basis for purported engineering
and economic benefits of DER to T&D systems prevents sound
business decision-making and policy-making that could facilitate
the implementation of DER. If the potential T&D benefits of DER
were objectively established, greater opportunities for the
deployment of DER would emerge. DER projects could be deployed to
provide direct benefits to customers, direct benefits to the
environment, and also direct benefits to the T&D systems. With
T&D benefits established independent of customer and
environmental benefits, those projects that more than one set of
benefits could be identified.
[0015] Regulations affecting industrial facilities and the
practices relating to interconnection of devices to T&D systems
have been developed over time, for the most part without
anticipation or consideration of the possible widespread deployment
of DER. These regulations and practices may now, without specific
intent, represent barriers to DER projects. This topic is the
primary focus of Making Connections. However, removal of barriers
to broader deployment of DER is a daunting problem for regulatory
authorities, network operators and DER practitioners. A clear
demonstration of the benefits of DER to T&D systems would
provide greater motivation for network operators and other
stakeholders to engage in the reformation of these barriers. Also,
a determination of which barriers have the greatest impact on the
DER projects having the most potential benefits for the system
would provide a basis for targeting these reformation efforts.
[0016] T&D system analysis and planning methods in the art have
significant limitations in making a thorough assessment of the
potential benefits of DER to a given T&D network.
[0017] Traditional transmission system analysis methods in the art
do not directly consider the related distribution systems. As a
result, traditional approaches prohibit direct assessment of the
extent to which transmission level problems arise from problems in
the distribution system. Moreover, traditional approaches thus also
prohibit direct assessment of the extent to which transmission
level problems that may arise from problems in the distribution
system are best mitigated at the distribution level, e.g. with
DER.
[0018] Likewise, as noted below, distribution system analysis
methods in the art do not directly consider the transmission
network. As a result, traditional distribution analysis approaches
prohibit direct assessment of the extent to which distribution
level problems arise from problems in the transmission system.
Traditional approaches thus also prohibit direct assessment of the
extent to which distribution level problems that may arise from
problems in the transmission system are best mitigated at the
distribution level.
[0019] Methods and analytical tools for characterizing the
conditions of high-voltage transmission systems and identifying
problems therein are well known in the art. Some of these methods
and analytical tools are described in U.S. Pat. No. 5,594,659 to
Schleuter and U.S. Pat. No. 5,796,628 to Chiang. A common class of
analytical methods is referred to in the art as "power flow"
techniques.
[0020] There have also been recent advances in these methods. Of
particular interest are analytical tools that use analytical
methods to determine optimal transmission network control variable
settings to minimize losses or power costs, as well as tools that
use analytical methods to identify locations for reactive capacity
additions. Another area of recent interest is tools that analyze a
system's proximity to voltage collapse, or its voltage stability
security. Schleuter's Method for Performing a Voltage Stability
Security Assessment for a Region of an Electric Power Transmission
System is an example of recent voltage security analytics. Chiang's
Dynamic Method for Preventing Voltage collapse in Electrical Power
Systems is another. These are discussed further below.
[0021] Methods and analytical tools for characterizing the
conditions of distribution systems and identifying problems therein
are also well known in the art. Some of these tools also use power
flow methods. These tools have been enhanced recently with the
development of the capability to consider unbalanced three-phase
flow. These tools are thus well-suited to perform detailed design
of distribution feeders with DER.
[0022] However, distribution system analysis methods in the art
consider distribution circuits or feeders individually rather than
as part of a network. As a result, traditional approaches prohibit
direct assessment of the extent to which problems arising on one
distribution feeder may affect, or be caused by, or may be best
remedied on other distribution feeders.
[0023] Thus, by treating transmission and distribution systems
independently, and by treating distribution feeders individually,
conventional methods in the art effectively prevent considering
whether network deficiencies observed at the transmission level may
be more effectively remedied by DER interconnected at
distribution-level voltages. Thus, the prior art presents
significant limitations to a thorough assessment of the potential
benefits of DER to a given T&D network.
[0024] Traditional analysis and planning of either transmission or
distribution systems typically considers only changes in
transmission or distribution elements--e.g. new lines, or new
transformers, or reconfigurations or new settings for control
variables, or in some cases new reactive capacity additions--as the
means to improve network performance.
[0025] Where non-wires alternatives are considered, a class of
alternatives, i.e., dispatchable demand reduction, reactive
capacity, or generation, may be considered alone. Traditional
methods do not include consideration of these alternatives
interchangeably to achieve a certain outcome. In addition,
traditional methods do not consider the broad set of impacts such
alternatives may have. In particular, DER is often seen as a way to
gain incremental energy or capacity, but using DER to improve
system stability or even reduce losses is often not considered.
[0026] Thus, conventional approaches in the art, by failing to
consider a broad set of DER alternatives and broad set of factors
impacted by DER, cannot provide a comprehensive assessment of the
potential benefits of DER to T&D systems.
[0027] Conventional approaches prohibit direct assessment of the
extent to which non-wires alternatives such as power generation
embedded within the network or dispatchable demand reduction,
particularly those placed in the distribution portion of the
network, could be used improve overall network performance, such as
stability or voltage security.
[0028] These approaches also prohibit direct assessment of the
extent to which such non-wires alternatives, particularly those
placed in the distribution portion of the network, could be used to
augment, defer, or avoid conventional network additions,
particularly in the transmission portion of the network.
[0029] Neither the Chiang method or the Schleuter method deal
directly with the question of the extent to which problems in a
transmission system are the result of problems in the associated
distribution system. Also, neither deals directly with the question
of whether mitigating problems close to their source in the
distribution system may be more effective than mitigating them at
the transmission level. Chiang's method is demonstrated using
transmission-only datasets, consistent with conventional practice
in the art. Even though Schleuter notes that voltage instability
problems can arise in both distribution systems and in transmission
systems, his method does not provide any means for taking into
account voltage instability problems in the distribution system. In
fact, Schleuter's method excludes those instability problems that
arise in distribution systems from consideration. Schleuter's
method focuses exclusively on transmission systems and mathematical
models of transmission systems.
[0030] Neither Chiang's method or Schleuter's method anticipates
consideration of instability problems in distribution systems in
the analysis of instability problems in transmission system. Also,
neither anticipates any analysis to assess the degree to which
instability problems in the transmission system arise from or are
exacerbated by instability problems in the distribution system.
Also, neither anticipates consideration of the extent to which
mitigation of instability problems in the distribution system could
also mitigate instability problems in the transmission system.
[0031] Neither Chiang's method or Schleuter's method anticipates
the analysis of transmission and distribution integrated together
as a single network to assess and/or remedy instability problems in
the network overall. Also, neither anticipates consideration of the
relative merits of mitigating instability problems in the
distribution system rather than (or in addition to) mitigating them
in the transmission system.
[0032] Schleuter's method is a voltage stability assessment method
only. It does not provide a means to determine whether additions of
real or reactive capacity within the system analyzed could mitigate
the problems identified and improve voltage stability and system
security.
[0033] Chiang's method provides the means to make a stability
assessment on a near-term look-ahead basis (specifically 25 minutes
ahead) based on anticipated loads. The method provides "load margin
measures" or measures of the system's ability to withstand
deviations from forecast load and generation conditions based on
forecast voltage profiles. The method also anticipates operating
responses including the addition of power generating capacity or
load sheds to maintain stability in those areas of the system
identified by the method as becoming weak.
[0034] Chiang's method does consider operational responses to
predicted voltage collapse conditions; however, this method is
designed to guide operational responses given the short (25 minute)
predictive window. These responses would presumably be limited to
deployment of existing load shed, generation or reactive capacity
opportunities. Chiang's method does not address the question of how
generation, load sheds, and reactive capacity, considered as
interchangeable alternatives, could be embedded anywhere in the
network on a planning basis to achieve the greatest improvement in
network performance. Given a method to determine those additions of
real and reactive capacity throughout the T&D network that
would achieve the greatest operational improvement, Chiang's method
could be used to guide operation or dispatch of that embedded
capacity.
[0035] U.S. Pat. No. 5,422,561 to Williams, et. al., describes a
control strategy for reactive power capacity (switchable
capacitors) installed in a power circuit that serves customer loads
to control both customer voltage and reactive power flow in the
circuit. The objective of the strategy is to increase generator
efficiency by reducing the reactive power generators must provide,
and to reduce losses and improve throughput capability of the
circuit.
[0036] U.S. Pat. No. 5,760,492 to Kanoi et. al., describes a
control strategy for real power capacity (distributed generation)
installed on a distribution feeder. The objective of Kanoi's
strategy is to operate distributed generation units on the feeder
to achieve a certain operating condition on the feeder.
[0037] The Williams strategy is based on the premise, accepted in
the art, that reactive capacity close to the customer load is more
effective than reactive capacity provided by a remote power
generation source. Kanoi notes that widely varying conditions in
lower voltage-level distribution systems, particularly where
distributed generation units are present, make it difficult to
control power quality merely by controlling voltage and reactive
power at the transmission level.
[0038] However, both the Williams and Kanoi control strategies
focus on individual lines of a power system. In neither case are
the lines in question considered as part of a larger network
comprised of many similar and dissimilar lines. The Williams
strategy considers the impact of switching capacitors in a line
with multiple voltages, where those voltages could represent
transmission and distribution levels. But it does not contemplate
the impact of switching capacitors throughout the network on
conditions throughout the network. The Kanoi strategy considers the
impact of dispatching generating units in a distribution line on
the conditions of that line, its associated step-down transformer
and its associated transmission line. It does not contemplate the
impact of dispatching distributed generation units embedded
throughout the network on conditions throughout the network.
[0039] Thus, in a limited way, both the Williams strategy and the
Kanoi strategy acknowledge that problems in a transmission system
may be the result problems in the distribution system, or that
problems in a transmission system may be best mitigated in the
distribution system. However, because both strategies focus on
individual lines, not the network, neither is capable of addressing
the extent to which problems observed in the transmission system
are the accumulation of problems in the distribution system.
Further, neither is capable of assessing the extent to which
problems observed at either the transmission or distribution level
are best mitigated at the distribution level, e.g. using DER.
[0040] Both the Williams and Kanoi strategies are operational
strategies. In the case of Williams, the strategy focuses on the
switching of existing capacitors to achieve certain types of
operational improvements on the circuit. In the case of Kanoi, the
strategy focuses on dispatching of distributed generation to
achieve certain types of operational conditions on the distribution
line and at its associated step-down transformer. Neither strategy
considers where on a planning basis reactive capacity (in the case
of the Williams strategy) or real capacity (in the case of the
Kanoi strategy) should be located to provide the greatest benefit
for the line in question. Further, neither considers where reactive
or real capacity, as the case may be, should be placed within a
broader network to provide the greatest benefit for the
network.
[0041] Both strategies are examples of the practice in the art of
considering a single class of embedded capacity and a narrow set of
performance criteria. In the case of Williams, reactive capacity is
managed to increase generator efficiency, reduce losses, and
improve throughput capability of the circuit in question. In the
case of Kanoi, real capacity is managed to achieve a given set of
conditions on the distribution line and at the step-down
transformer, specifically voltage levels. The Williams strategy
does not consider real capacity (load sheds) or real and reactive
power together (embedded generation) as additional means to improve
performance of the circuit. The Kanoi strategy does not consider
reactive capacity (capacitors) or load sheds as additional means to
improve performance. The Williams strategy does not consider the
impacts of adding or removing reactive capacity on the stability or
voltage security of the circuit. The Kanoi strategy considers
voltage, but not reactive power requirements or reactive power
flows.
[0042] Because both strategies focus on an individual line, neither
can address the question of the extent to which problems observed
in a transmission system are the result of problems observed in the
associated distribution system.
[0043] Because both strategies are limited to a single line and a
single class of capacity, neither can address the broader question
of whether mitigating network problems close to their source in the
distribution system may be a more effective means of mitigating
problems observed at the transmission level.
[0044] Most importantly, neither strategy can address the question
of how generation, load sheds, and reactive capacity, considered as
interchangeable alternatives, could be embedded anywhere in the
broad network to achieve the greatest improvement in network
performance.
[0045] U.S. Pat. No. 5,684,710 to Ehlers describes the remote
control of loads, specifically the restoration of power following
an outage and the detection of outages. Again, Ehler's method does
not consider any impacts beyond the distribution system, and does
not consider any management of loads alone or in concert with other
forms of DER for the purpose of enhancing network performance.
[0046] U.S. Pat. No. 5,414,640 to Seem describes dispatchable
demand reduction as an element in a power system. However. Seem's
method considers dispatchable demand reduction only as a means to
reduce energy consumption, not to as a means to improve T&D
network performance. His method does not envision taking into
account impacts on the transmission system or the coordination of
the installation or operation of demand reduction with power
generation and/or reactive capacity in the power system.
[0047] U.S. Pat. No. 4,208,593 to Sullivan describes controllable
electrical demand (or dispatchable demand management) in the art as
selective disconnection of loads at specified levels of aggregate
load. Sullivan describes a method and system for controlling
electrical demand that overcomes disadvantages in the prior art
arising from failures of the control system. Sullivan's method also
introduces the capability to control demand on the basis of time as
well as aggregate load. Again, Sullivan's method does not
anticipate the use of dispatchable demand reduction as a way to
improve network performance.
[0048] U.S. Pat. No. 5,278,772 to Knupp describes a method for
determining the operating profile, or dispatch, of multiple power
generation units in a power system. However, under Knupp's method
power generation units are dispatched based on their operating
costs only. No consideration is given to the impact the operation
of these units may have on network performance, and the dispatch of
these units to improve network performance is not anticipated.
[0049] In Integrated Assessment of Dispersed Energy Resource
Deployment (C. Marnay, R. Blanco, K. S. Hamachi, C. P. Kawaan, J.
C. Osborn, F. J. Rubio, LBNL-46082, June 2000), the authors looked
at the impacts of DER on the power system. However, the bulk of
their study focused on the customer drivers for DER in an effort to
develop a way to predict customer adoption. The implication is that
DER adoption decisions are made by customers on their own without
any knowledge or acknowledgement of the impacts on the grid. These
customer decisions are thus something for the network operator to
guess at and react to, hence the value of a predictive model. The
study does not anticipate an assessment by the network operator of
the types of DER projects that enhance network performance and/or
the development of incentives to actively encourage such
projects.
[0050] The study acknowledges that the "optimal" penetration of DER
will require improved economic signals from the network operator to
the customers, and states the need to compute such signals, but
goes no further.
[0051] While the study acknowledged that distributed generation on
a distribution feeder can have impacts at the transmission level,
no attempt was made to evaluate the impacts of DER implemented at
the distribution level on the transmission level, or to assess the
potential for improving network performance through interactions
between feeders.
[0052] Two generator additions were simulated on a single
distribution feeder, analyzed as an isolated facility. The results
showed that these additions could reduce losses and correct
instances of overvoltage and undervoltage.
[0053] This analysis considered the distribution feeder as a
standalone facility; it did not consider or anticipate a method or
approach where the distribution feeder was incorporated with other
feeders and transmission facilities in a larger network. This
study's approach therefore could not consider how these additions
could affect conditions at the transmission level or elsewhere in
the network, nor could it directly assess the merits of capacity
additions on the feeder vs. capacity additions at the transmission
level or elsewhere in the network.
[0054] This work was performed as a demonstration of a particular
software package's suitability for such analysis, not as a
demonstration of a methodology to assess the potential for a
variety of DER devices (generation, dispatchable load sheds, and
capacitors) to achieve an overall improvement in power quality and
losses in an integrated T&D network.
[0055] In Applications Guide: Distribution Capacity Planning With
Distributed Resources, EPRI, TR-11468, January, 2000, EPRI
characterizes the conventional assessment of DER benefits as the
cost of a planned network upgrade that is avoided or deferred by
DER capacity, less the cost of that DER capacity. EPRI points out
that the limitation of this approach is that the "planned" network
upgrade to be avoided or deferred was identified without
consideration of DER in the plan.
[0056] The Area Investment Strategy Model developed by EPRI for
assessing the benefits of DER involves analysis to determine if DER
can be incorporated in distribution to minimize the overall cost of
capacity required to serve customers. Again, this method focuses
the distribution system alone. It also considers DER as a source of
incremental capacity only; it does not consider DER as a means to
improve system stability or voltage security.
[0057] A further limitation of such an approach is that the utility
is not the decision-maker for DER projects sponsored by a customer
or third party. Moreover, a utility cannot make an informed
economic evaluation of customer-sponsored DER projects. The utility
cannot determine the value the customer places on the project's
customer benefits, particularly as these benefits may include such
intangibles as energy cost certainty, independence, or peace of
mind. The utility also cannot know the actual DER technology costs
the customer has been quoted. Thus, a conclusion under the EPRI
methodology that DER additions result in a least cost solution is
at best incomplete, and might be incorrect. The EPRI method is not
capable of assessing or quantifying the stand-alone benefits of DER
to the T&D system.
[0058] A thorough assessment of the network benefits of DER
requires an evaluation that goes beyond a distribution planning
area by itself, or, for that matter, beyond the transmission system
by itself. It also requires the consideration of a broad set of
factors that DER may affect. A more efficient approach to DER
planning is for the utility to determine the potential benefits DER
could provide to the utility's system as described, and the nature
of projects that would deliver those benefits, independently of
customer considerations. Then the utility has the means to promote
projects having similar characteristics among its customers (and
discourage dissimilar projects). The utility then also has the
ability to identify those projects that customers will not pursue
but whose value to the system justifies utility investment.
[0059] In conclusion, we are aware of no method in the prior art of
analyzing T&D networks that provides a thorough, objective
assessment of the potential benefits DER may provide to a T&D
network. This is due in part to the apparent absence of methods in
the prior art that provide a means to directly observe the extent
to which problems at the transmission level are caused by or
exacerbated by problems at the distribution level (and vice versa).
Among other things, this prevents the direct observation of the
merit of remedying problems throughout the network close to where
they occur, particularly at the distribution level, such as with
DER.
[0060] The absence of a method that provides a thorough, objective
assessment of the potential benefits of DER is also due in part to
the apparent absence of methods in the prior art that
simultaneously consider a variety of potential DER additions or
that appropriately consider the range of impacts of DER.
[0061] The absence of a method that provides a thorough, objective
assessment of the potential network benefits of DER is also due in
part to the apparent absence of methods in the prior art that
consider the potential network benefits of DER independently of the
other potential benefits of DER.
[0062] We are also not aware of any method in the prior art that
identifies a specific, theoretical set of DER projects that will
improve or maximize performance of the subject T&D network.
Further, we are aware of no method that identifies such projects
for the purpose of guiding policies, identifying consequential
barriers to beneficial projects, or designing DER incentives that
share value rather than shift costs to non-participants.
[0063] Accordingly, one object of the present invention is to
provide a method for providing a thorough assessment of the
potential benefits DER may provide to a T&D network. Such
benefits may include performance improvement such as the reduction
in electrical losses, improvement in system stability and/or power
quality. These benefits could also include the deferral or
avoidance of system additions that would otherwise be required to
reliably serve load.
[0064] A further object of the present invention is to provide a
method for providing a thorough assessment of the potential
benefits DER may provide to a T&D network that considers a
variety of DER alternatives interchangeably, not generation,
capacitors, or load sheds alone.
[0065] This object and the prior object overcome a significant
drawback of the prior art in thoroughly assessing the potential
T&D benefits of DER that arises from the practice of
considering classes of DER individually and/or considering a narrow
set of performance measures.
[0066] A further object of the present invention is to provide a
method for analyzing the T&D network, including but not limited
to providing a thorough and objective assessment of the potential
benefits DER may provide to a T&D network, that includes a
means to directly observe the extent to which problems at the
transmission level are caused by or exacerbated by problems on any
given distribution feeder (and vice versa).
[0067] A further object of the present invention is to provide a
method for analyzing the T&D network, including but not limited
to providing a thorough, objective assessment of the potential
benefits DER may provide to a T&D network, that includes a
means to directly consider the merits of remedying problems close
to where they occur, whether in the distribution system or in the
transmission system, including possibly using DER to remedy
problems anywhere in the network.
[0068] This object and the prior object overcome a significant
drawback in the prior art, particularly as it relates to assessing
the benefits of DER to a T&D network, that arises from the
analysis of transmission independently of distribution, and
vice-versa, and the analysis of distribution feeders
individually.
[0069] A further object of the present invention is to provide a
method for analyzing the T&D network, including the
incorporation of DER within the network, that facilitates the
evaluation of how these elements should operate and interact under
a variety of network conditions.
[0070] A further object of the present invention is to provide a
method for providing an objective measure of the potential benefits
DER may provide to a T&D network, where such measure is
independent of non-network considerations such as DER benefits for
customers or the environment.
[0071] This object enables decision-making relative to T&D
network matters, including the design of DER incentives based on
network benefits, without the distortion of non-network
considerations.
[0072] A further object of the present invention is to provide a
method for quantifying the potential benefits DER could provide a
given network, in both engineering and economic or financial
terms.
[0073] Quantifying potential T&D network benefits of DER in
economic terms enables the transfer of the value associated with
such network benefits between stakeholders. This could include, for
example, financial incentives for DER projects based on a sharing
of the network value such projects create rather than simply
shifting costs from one set of customers to another.
[0074] A further object of the present invention is to provide a
method for characterizing the specific DER projects that realize or
approach the potential benefits DER may provide to a T&D
network. This characterization would include where within the
network particular types of DER would make the greatest
contribution.
[0075] A thorough, objective assessment of the potential benefits
of DER to a T&D network along with knowledge of the nature of
projects that achieve those benefits would be of significant
economic value to T&D network operators, generally utilities.
Such information may reveal the potential for substantial savings
in losses, improvements in power quality and/or stability, or the
opportunity to defer or avoid costly network improvements.
[0076] Such an assessment of potential DER benefits, and the
specific projects that would provide them, is of great value to a
utility if determined objectively, independent of non-network
considerations. A utility cannot accurately incorporate customer
economics in its planning, nor can it unilaterally implement
purported "least cost" solutions if they include customer-sponsored
projects. Using the method of this invention a utility can quantify
the potential benefits of DER for its system, and devise incentives
that share that value with third parties to encourage beneficial
DER projects and capture at least a portion of that potential
value.
[0077] An objective assessment of the potential benefits of DER to
a T&D network and knowledge of the nature of projects that
achieve those benefits would permit the identification of those
barriers that have the greatest impact on the DER projects with the
greatest potential T&D benefit. This knowledge in turn would
permit the development of high-impact, targeted policy initiatives
to promote beneficial DER.
[0078] The method of this invention also has substantial economic
value to developers of DER projects and vendors of DER
technologies. By identifying an additional set of benefits, an
additional beneficiary, and/or additional revenue sources for DER
projects, and by facilitating policies that remove barriers to DER
projects, this invention opens new markets for DER projects and DER
technologies.
[0079] The means to analyze the integrated T&D network, with
DER incorporated within the network, under a variety of conditions,
would have great value to network operators and other stakeholders.
The means to analyze the integrated T&D network, with DER
incorporated within the network, under a variety of conditions,
would permit, for example, identification of DER projects that make
the greatest contribution to load-carrying capability of the
overall network under peak load conditions, and an operating plan
for those projects to provide other benefits under non-peak load
conditions. This type of analysis is essential to realizing the
potential of such concepts as those described in the Wired Magazine
article above.
[0080] A method for analyzing the T&D network, including
providing an objective assessment of the potential benefits DER may
provide to a T&D network, that includes a means to directly
observe the extent to which problems at the transmission level are
caused by or exacerbated by problems on any given distribution
feeder (and vice versa) would have substantial value to network
operators by identifying the root causes of problems contributing
to substandard network performance.
[0081] A method for analyzing the T&D network, including
providing an objective assessment of the potential benefits DER may
provide to a T&D network, that includes a means to directly
consider the merits of remedying problems, where such problems may
arise either at the transmission level or at the distribution
level, at either the transmission level or at the distribution
level would have substantial value to network operators in
identifying additional solutions for remedying network problems,
solutions that may be more effective and/or less costly to
implement.
[0082] Such methods also have substantial economic value to
developers of DER projects and vendors of DER technologies. An
expansion of the understanding of the areas where DER projects may
represent potential solutions to network problems would open new
markets for DER projects and technologies.
[0083] Further objects and advantages of this invention will become
apparent from consideration of the drawings and ensuing
description.
SUMMARY OF THE INVENTION
[0084] The features and advantages described in the specification
are not all inclusive and, in particular, many additional features
and advantages will be apparent to one of ordinary skill in the art
in view of the drawings, specification, and claims. Moreover, it
should be noted that the language used in the specification has
been principally selected for readability and instructional
purposes, and may not have been selected to delineate or
circumscribe the inventive subject matter.
[0085] The present invention provides an improved method for
analyzing power systems; in particular, power systems that may
incorporate DER. A method according to one embodiment of the
present invention provides a thorough determination of the
potential for network performance improvement that DER could
provide. The method also determines the potential for network
performance improvement that DER could provide independently and
distinct from other benefits DER may provide. The method also
quantifies the network performance improvement in engineering and
financial terms, and identifies and characterizes the specific DER
projects that would realize that potential improvement in network
performance.
[0086] This methodology incorporates several distinguishing
features:
[0087] First, the T&D network is analyzed as a single
"Energynet," encompassing distribution as well as transmission
elements and with embedded distributed energy resources (DER) at
all voltage levels. This overcomes drawbacks in prior methods by
providing a means to directly observe the extent to which problems
at the transmission level are caused by or exacerbated by problems
on any given distribution feeder (and vice versa). This also
overcomes drawbacks in prior methods by permitting direct
evaluation of network additions implemented close to the sources of
problems whether in the distribution system or the transmission
system. It also overcomes drawbacks of prior methods by permitting
planning, design, and operation decisions for the entire Energynet
that take into account the interaction of all elements across the
entire network.
[0088] Second, the method evaluates multiple classes of DER for
their impacts on multiple aspects of network performance--factors
affecting stability and power quality in addition to losses or the
ability to displace network upgrades. This overcomes drawbacks of
prior methods by permitting a more thorough assessment of the
impact and potential benefits of DER. This is of particular
interest when evaluating potential DER additions where their
differences in loss reduction may be small, but they may contribute
very differently to stability and power quality.
[0089] Third, this methodology introduces the notion of an
"optimal" portfolio of DER projects, or the Optimal DER Portfolio.
This theoretical portfolio is developed and optimized purely from
the standpoint of its network benefits. That is, this portfolio is
not influenced by other considerations for DER such as customer
benefits or environmental benefits. The Optimal DER Portfolio
feature overcomes several limitations of prior methods and provides
new information and benefits as discussed below.
[0090] The network benefits attributable to the Optimal DER
Portfolio represent the greatest potential DER has to improve
network performance consistent with the conditions and limitations
incorporated in the method.
[0091] The individual projects of the Optimal DER Portfolio are the
projects that, if implemented in the subject network, would yield
the greatest improvement in network performance.
[0092] The Optimal DER Portfolio is not a plan to implement, but a
guide for utilities to better manage their power systems.
[0093] The network benefits the Optimal DER Portfolio projects
would provide--that is, network benefits of DER assessed according
to the method of this invention--are distinct from, and additive
to, benefits of DER projects other than network benefits. The
Optimal DER Portfolio thus enables a determination of real DER
projects that combine network benefits with other benefits such as
benefits to an end-use customer, and thus might be developed at a
lower cost to the utility. The Optimal DER Portfolio also enables a
determination of those projects that would benefit the system only,
and thus must be developed by the utility.
[0094] Because the network benefits provided by the Optimal DER
Portfolio are distinct from other potential benefits of DER, the
Optimal DER Portfolio offers an objective means for identifying,
quantifying, and pricing network benefits of DER. Further, it is
ideally suited for formulating policies to promote the development
of real DER projects based on their potential for direct
enhancement of network performance. The Optimal DER Portfolio also
is ideal for formulating pricing, tariffs, or financial incentives
based on sharing of the value of DER's system benefits with DER
developers rather than cost shifting.
[0095] The Optimal DER Portfolio projects can also be used to guide
policies to promote greater deployment of DER that benefits the
T&D network. Identifying the specific projects that provide the
greatest network benefits permits, in turn, identification of the
most consequential barriers to those projects. These barriers,
then, are the ones with the most impact on T&D network
improvement and reasonably should receive the most targeted
attention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0096] FIG. 1 is a Venn diagram illustrating one purpose of a
method according to one embodiment of the present invention.
[0097] FIG. 2 is a flowchart illustrating the creation of an
Energynet dataset according to one embodiment of the present
invention
[0098] FIG. 3 is a flowchart illustrating the process for
identifying the DER capacity additions that underlie that set of
DER projects that provide the maximum potential for improvement in
network performance according to one embodiment of the present
invention.
[0099] FIG. 4 is a flowchart illustrating the process for
characterizing DER capacity additions as Optimal DER Portfolio
projects according to one embodiment of the present invention.
[0100] FIG. 5 is a flowchart illustrating the process of
quantifying the network benefits provided by the Optimal DER
Portfolio projects according to one embodiment of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0101] The Figures and the following description relate to
preferred embodiments of the present invention by way of
illustration only. It should be noted that from the following
discussion, alternative embodiments of the methods disclosed herein
will be readily recognized as viable alternatives that may be
employed without departing from the principles of the claimed
invention.
[0102] FIG. 1 is a Venn diagram illustrating one purpose of a
method according to one embodiment of the present invention;
specifically the determination of potential network benefits of DER
as distinct from benefits of DER for customers or environmental
benefits of DER, and the specific DER projects that provide such
grid benefits.
[0103] Space 102 represents those DER projects that provide
benefits to end-use electricity customers. These benefits might be
reduced energy cost or increased reliability. Space 102 is
characteristic of the customers served by the T&D network.
Methods for identifying the DER projects in Space 102 and the
potential benefits of these projects are well-known in the art.
[0104] Space 104 represents those DER projects that provide
benefits to the environment. These benefits might be reduced
emissions, or greater fuel-use efficiency, or use of a waste for
fuel. Space 104 is characteristic of the technologies available for
deployment within the T&D network. Methods for identifying the
DER projects represented in Space 104 are well known in the
art.
[0105] Space 106 represents those DER projects that provide
benefits to the performance of the T&D network. These benefits
might be reduced losses, improved stability or voltage security,
improved power quality, improved load-serving capability, or the
opportunity to forego or defer improvements to the network that
would otherwise be required to adequately serve loads. The
potential network benefits achieved and the specific DER projects
that achieve them are characteristic of the T&D network itself.
According to one embodiment of the present invention, a method
concerns itself in part with assessing the magnitude and value of
the potential network benefits DER projects in Space 106 represent,
and identifying nature of those projects--the Optimal DER Portfolio
projects.
Preparing the Energynet Datasets
[0106] A method according to one embodiment of the present
invention overcomes significant drawbacks of previous T&D
network analysis methods, particularly as they relate to assessing
the network impact or potential network benefits of DER, by
performing mathematical simulation of the subject network using a
dataset that combines transmission and distribution elements and
their interconnection together, as a single integrated network.
This simulated network has the capability to incorporate additions
of real capacity, reactive capacity, and real and reactive capacity
together as real and reactive energy sources, e.g., generators,
capacitors, dispatchable demand, and the like, embedded within the
network at either distribution or transmission voltage levels, as
needed. We refer to a network so described as an Energynet and such
a dataset as an Energynet dataset.
[0107] According to one embodiment of the present invention, real
capacity or energy source, reactive capacity or energy source, and
real and reactive capacity or energy source together may represent
dispatchable demand reductions, capacitors, generators and the
like. Accordingly, the Energynet may also refer to a transmission
and distribution system, combined as a single network that
incorporates dispatchable demand reduction, capacitors, and
generation, all of which may be analyzed and managed as an
integrated system.
[0108] According to one embodiment of the present invention, the
Energynet dataset would include the following: For the transmission
portion of the subject network, generating stations interconnected
at transmission voltage level(s), impedances and interconnections
of transformers and transmission lines, impedances of loads
interconnected at transmission voltage level(s), and sources of
reactive power such as synchronous voltage condensers and capacitor
banks. For the distribution portion of the subject network, the
Energynet dataset would include impedances of distribution
transformers, transmission-to-distribution stepdown transformers,
impedances of distribution lines, impedances of loads
interconnected at distribution voltage level(s), the
interconnection of lines and transformers, and sources of reactive
reserves such as synchronous voltage condensers and capacitor
banks. The distribution portion of the system would also include
generating stations interconnected at distribution voltage
level(s), taking into consideration their capacity to provide
reactive power, loads that may be curtailed by the network operator
on demand, and interconnections such as those on looped
distribution radials that may be switched, along with the switch
positions normally used under different operating conditions.
[0109] The use of such an Energynet dataset overcomes many of the
disadvantages of traditional analysis methods used for transmission
systems or distribution systems, in particular their disadvantages
as they relate to assessing the impact of DER. Analysis using an
Energynet dataset permits the direct observation of the extent to
which problems at the transmission level of the network arise from
or are exacerbated by problems at the distribution level (and vice
versa). Analysis using an Energynet dataset also permits direct
analysis of the merits of remedying problems at either the
transmission or the distribution level with changes at either
level; in particular, the merits of DER additions at the
distribution level to remedy problems of the overall network.
[0110] FIG. 2 is a flowchart illustrating the creation of an
Energynet dataset set of network conditions according to one
embodiment of the present invention. An Energynet dataset so
created would specific to a given set of network conditions, e.g.
Summer Peak in a given year, as represented by Block 202.
[0111] According to one embodiment of the present invention,
creating this Energynet dataset begins with an existing dataset
incorporating the elements of the transmission system that may be
read and interpreted by a commercially-available "load flow"
computer program traditionally used in the art for analyzing
transmission systems. Elements of the distribution feeders of the
subject network are then added to the dataset as described below.
In general, utilities or transmission system operators have such
transmission load flow datasets available as they are commonly used
in the art for transmission planning. In Block 204 such a
transmission load flow dataset consistent with the conditions to be
analyzed is secured.
[0112] As represented by Block 206, in some cases utilities may
also have impedances of loads and elements of their distribution
feeders available in a compatible dataset format for combination
with the transmission dataset. In Block 2012 these distribution
data are evaluated by one skilled in the art to ensure the
conditions they represent are consistent with the network
conditions to be analyzed and the conditions represented by the
transmission dataset. For example, one skilled in the art would
exercise ordinary judgment to ensure that the distribution-level
data chosen for incorporation in an Energynet dataset that begins
with a Summer Peak transmission dataset represent conditions that
are consistent with the Summer Peak conditions reflected in the
transmission data.
[0113] If impedances of the loads and elements of the distribution
feeders are not directly available, information from engineering
design documents and operational records such as SCADA records,
circle charts, and operational records obtained in Block 208 can be
used by those skilled in the art to derive the distribution element
and load impedances needed to develop the Energynet dataset, as in
Block 2010.
[0114] The following describes the process in Block 2010 in more
detail: [0115] Impedances of the transmission-to-distribution
stepdown transformers under the conditions to be modeled may be
determined from recorded circle charts. [0116] Individual feeder
currents under the conditions to be modeled may be taken from SCADA
records. [0117] The total impedance of each feeder can be
calculated from this information. [0118] The impedance of the
elements of each feeder may then be then calculated from
engineering design records for the feeder (e.g. line length and
construction and details of other feeder elements). [0119] The each
feeder's total load impedance can then be derived as the difference
between the calculated total impedance and the feeder element
impedance. [0120] Impedances of individual loads on a given feeder
can be estimated using transformer ratings taken from engineering
records.
[0121] Again, in Block 2012 one skilled in the art ensures that the
operational records used to calculate the feeder element and load
impedances are consistent with the network conditions to be
analyzed and the conditions represented by the transmission
dataset.
[0122] In Block 2014 the interconnection of distribution elements
and the normal switch settings for the switchable looped radial
feeders are obtained from engineering and operational records and
verified by one skilled in the art to be consistent with the
network conditions to be analyzed. For example, for an Energynet
dataset depicting Summer Peak conditions, one skilled in the art
would use judgment to ensure that switch positions are modeled as
appropriate for those conditions.
[0123] In Block 2016 the available distribution element and load
impedances and interconnections are incorporated in the
transmission dataset, according to the means of the particular load
flow program selected for analyzing the dataset for adding or
appending data to a dataset.
[0124] It should be noted that commercially-available load flow
programs are traditionally used in the art for analyzing
transmission systems. Accordingly, the addition to a transmission
load flow dataset of information representing distribution feeders
may represent the addition of a large number of new elements into
the dataset and/or dramatically increase the total number of
elements in the dataset. It may be burdensome to add these data,
and the new elements may increase the computational complexity of
analyzing this Energynet dataset. A method according to an
alternative embodiment of the present invention that is appropriate
for an analysis that focuses primarily on DER capacity additions
may involve incorporating in the Energynet dataset only the
distribution feeders that are likely sites for DER. This could
allow the exclusion of secondary distribution feeders and/or the
exclusion of those feeders serving primarily or only residential
areas. The potential for on-site generation at residences and the
opportunity evaluate and improve the operation of all the
distribution portions of the network suggests some drawbacks of
excluding portions of the network from the Energynet
simulation.
[0125] It should also be noted that incorporating distribution and
transmission elements in a single Energynet dataset increases the
potential for the presence of elements with very low impedances,
such as short lines, and/or elements having very different
impedances in close proximity. These considerations may introduce
challenges for some existing load flow programs designed primarily
to analyze transmission systems, and/or some programs may be unable
to distinguish between valid data and errors. In Block 2018 those
skilled in the art use judgment to combine elements to eliminate
problematic low impedance elements without affecting the overall
results, or use the operational features of the selected load flow
program to adjust the error-checking features or the performance
parameters of the program to facilitate solutions with the added
distribution data or to change the precision the program uses to
identify acceptable solutions.
[0126] According to one embodiment of the present invention, the
Energynet dataset, once constructed, is analyzed using a computer
programmed with one or more load flow programs similar to those
traditionally used in the art for analyzing transmission systems.
Load flow programs are used initially to characterize the condition
of the Energynet "as found," or prior to any changes according to
the method. Load flow programs are also used to evaluate the impact
on the condition of the Energynet of any changes to the Energynet;
in particular, the addition of DER capacity anywhere in the network
as described below.
[0127] Given the availability of a variety of
commercially-available load flow programs in the art, the selection
of the program to be used may impact the format required for the
Energynet dataset, its contents, and the types of adjustments
required in Block 2018. Alternatively, a new format may be
developed specifically for a new load-flow program developed
according to one embodiment of the present invention.
[0128] Block 2020, the result of the foregoing process, is an
Energynet dataset that represents the subject network under the
selected conditions and that is compatible with the selected load
flow program.
[0129] In Block 302, analysis of the resulting Energynet dataset of
Block 2020 using the selected load flow program yields a
characterization of the integrated transmission and distribution
network under the conditions selected for analysis as a "base
case," i.e. before the addition of DER capacity.
[0130] Such load flow tools will characterize the power flows,
losses, voltage profile, and power factor within the integrated
transmission and distribution network represented by the Energynet
dataset, in this case before the addition of any DER.
[0131] Some analysis tools known in the art have the capability to
evaluate (not just characterize) the voltage profile of the network
being analyzed and/or determine the proximity to voltage collapse
or the voltage security of the network. If such analysis tools are
applied to an Energynet dataset according to one embodiment of the
present invention, results will include an evaluation of the
voltage profile and/or the proximity to voltage collapse or voltage
security across the transmission and distribution portions of the
integrated network represented by the Energynet dataset.
[0132] According to one embodiment of the present invention,
several Energynet datasets are developed, each representing the
subject network under a different set of conditions. Different
Energynet datasets for different system conditions may be prepared
by making appropriate modifications to one Energynet dataset that
incorporates transmission and distribution elements prepared as
described above.
Developing DER Capacity Additions
[0133] A method according to one embodiment of the present
invention provides the ability to determine the potential
improvement in network performance available through deployment of
DER by evaluating potential additions of real power generating
capacity, reactive capacity, or real and reactive capacity
together, interchangeably as potential DER capacity additions to
improve network performance. According to one embodiment of the
present invention, such DER capacity additions may be applied
anywhere within the Energynet, at any voltage, in any
combination.
[0134] According to one embodiment of the present invention,
potential additions to the Energynet of such DER capacity are
evaluated for their ability to improve network performance. Such
DER capacity additions are evaluated for their impact on a variety
of factors, including reducing losses, improving power quality and
improving system stability and voltage security.
[0135] According to one embodiment of the present invention,
additions of real and reactive power together represent power
generators with synchronous condensers. Additions of real power
alone represent dispatchable demand reductions. Additions of
reactive power alone represent capacitors.
[0136] The method of the present invention thus permits a
comprehensive evaluation of all the possibilities in terms of DER
capacity additions, as well as the interplay between them, and
permits consideration of the impact of different potential DER
additions on a broad set of network performance criteria.
[0137] FIG. 3 is a flowchart illustrating this process According to
one embodiment of the present invention.
[0138] According to one embodiment of the present invention the
evaluation of the impact of particular DER capacity additions is
performed by comparison, in Block 3010, of network performance with
the DER capacity additions (Block 308) with network performance
without those DER capacity additions (Block 302) using the selected
analytical tools.
[0139] In Block 306 alternative DER capacity additions, or
combinations of additions of real capacity, reactive capacity,
and/or real and reactive capacity together are formulated and
incorporated into the Energynet model by one skilled in the
art.
[0140] Under an alternative embodiment of the present invention,
one skilled in the art formulates proposed DER capacity additions
to improve system performance in an ad hoc fashion. This process is
similar to the process described as background art by Schleuter for
identifying system improvements in the system planning of
transmission systems; however, in this case the potential
improvements are expanded to include real and reactive capacity at
locations within either the distribution or transmission portions
of the network.
[0141] Under another alternative embodiment of the method of the
present invention, proposed DER capacity additions are formulated
by or with the assistance of software tools known in the art having
the capability to determine where additional real or reactive
capacity is needed based on an analysis of the network
condition.
[0142] In Block 308 the condition of the updated Energynet model is
re-assessed using the selected load flow tools. In Block 3010 the
results are evaluated by comparison with the Energynet conditions
prior to the addition of such DER capacity additions. According to
one embodiment of the present invention, these results are
evaluated to determine if the DER capacity additions result in
reduced losses, improved power quality, and improved network
stability and voltage security.
[0143] Under an alternative embodiment of the present invention the
updated Energynet datasets are evaluated using analytical tools
known in the art to directly evaluate voltage security, or
proximity to voltage collapse, such that DER capacity additions may
be evaluated directly for the improvement in voltage security they
offer.
[0144] Other analytical tools may provide more revealing
comparisons of Energynet conditions and illustrate with greater
precision the changes in Energynet conditions resulting from the
DER capacity additions.
[0145] According to one embodiment of the present invention, the
foregoing process of formulating DER capacity additions in Block
306 and assessing their impact in Blocks 308 and 3010 is repeated
until it appears to one skilled in the art in Block 3014 that
further DER additions will not yield meaningful performance
improvement based on the observation of successive sets of
results.
[0146] In Block 3012 DER capacity additions that do not improve
Energynet performance are revised or reversed.
[0147] It is reasonable to expect that any and all additions of
real capacity within the Energynet may be shown to yield an
improvement in performance due to the reduction in losses. Thus, in
Block 304 external limits are placed on potential additions of new
real capacity, either in the form of additions of dispatchable
demand reduction or in the form of new generating capacity.
Additions of dispatchable demand reductions may be limited based on
an assessment of the types of customers represented in the
Energynet model; particularly the willingness of such customers to
provide such dispatchable demand reductions, as determined through
past practice by one experienced in the art. Additions of new
generating capacity are limited by an assessment of the technical
limits of the distribution feeders represented in the Energynet
model to accommodate such new generating capacity, as determined by
one knowledgeable in the art.
[0148] Following an evaluation of a variety of alternative DER
capacity additions as described above, Block 3016 results in a set
of additions of real capacity, reactive capacity, and real and
reactive capacity together that, based on an evaluation of
alternatives, yields the greatest reduction in losses, improvement
in power quality, and improvement in network stability and voltage
security.
[0149] It should be noted that a transmission system, even a
relatively large one, realistically must consider only a small
number of potential additional generating plants. However, even a
small T&D network represented as an Energynet may have a great
many potential DER capacity additions that must be considered and
evaluated for the network benefits they provide. Accordingly, the
iterative process from Block 306 through either Block 3012 or 3014
and back may be laborious.
[0150] Network analysis tools in the art may exist or emerge with
the capability to determine with greater precision the locations in
the network where such DER capacity additions will reduce losses,
improve power quality, and/or improve system stability and voltage
security. Such tools used within a method according to one
embodiment of the present invention will yield results having
greater accuracy and repeatability more quickly.
Characterization of DER Capacity Additions as DER Projects
[0151] According to one embodiment of the present invention, the
set of DER capacity additions determined in Block 3014, as real
capacity additions, reactive capacity additions, and additions of
real and reactive capacity together, are now characterized as
specific DER projects in an Optimal DER Portfolio.
[0152] As further described below, these DER projects may be
characterized in terms of their type, size, location within the
network, operating profile under varying network conditions, and
when they must be added to the network to match anticipated changes
in network conditions.
[0153] FIG. 4 is a flowchart of this process According to one
embodiment of the present invention.
[0154] According to one embodiment of the present invention,
additions of real and reactive power together (Block 406) represent
power generators with synchronous condensers. Additions of real
power capacity alone (Block 402) represent dispatchable demand
reductions (Block 408). Additions of reactive capacity (Block 404)
represent capacitors.
[0155] In an alternative embodiment of the present invention,
additions of real power capacity alone (Block 402) may also
represent power generators with inverters.
[0156] In Blocks 4010 and 4012 DER capacity additions are
aggregated or disaggregated as appropriate to match the sizes of
capacitors and generating units, respectively, known to be
available.
[0157] In Block 4016, the Energynet dataset is updated to reflect
such aggregation or disaggregation, and a determination is made in
Block 4018 by one skilled in the art, using the selected analytical
tools as described above, of whether such aggregation or
disaggregation yields network performance that is acceptably close
to the performance achieved before such aggregation or
disaggregation. In Block 4020 revisions are made as
appropriate.
[0158] In Block 4022 this process yields a list of generators,
capacitors, and dispatchable demand reductions, or load sheds, that
are demonstrated to yield the greatest improvement in the
performance of the subject network, specifically as reduced losses,
improved power quality, and improved system stability or voltage
security. These generators, capacitors, and dispatchable demand
reductions are individually characterized in terms of their size
and their interconnection point within the network.
[0159] It should be noted that this list of projects, developed as
described, is demonstrated to yield the greatest improvement in
network performance only under a single set of conditions.
[0160] Under the preferred embodiment of the present invention
Energynet datasets are prepared a variety of different system
conditions according to the process described above and illustrated
in FIG. 2. In addition, different sets of capacity additions that
achieve the greatest network performance improvement under the
different sets of conditions are developed according to the process
described above and illustrated in FIG. 3.
[0161] Alternatively, a single set of DER capacity additions
developed as described above is tested under different system
conditions and adapted if necessary to achieve a high level of
improvement in network performance.
[0162] In Block 4022, differences in the various DER capacity
additions developed for the various system conditions, or, the
adaptations to the single set of DER capacity additions for
different conditions, are reflected in the Optimal DER Portfolio as
follows: [0163] Different real capacity additions under different
system conditions represent dispatch schemes for dispatchable
demand reductions in the Optimal DER Portfolio. [0164] Different
reactive capacity additions may be accommodated to some extent by
variable or switchable capacitors in the Optimal DER Portfolio.
[0165] Different real and reactive capacity additions together may
be accommodated to some extent in dispatch schemes for generators
in the Optimal DER Portfolio.
[0166] Under a preferred embodiment of the present invention, one
or more Energynet datasets are prepared to reflect system
conditions in the future, particularly incorporating load growth,
as described above and illustrated in FIG. 2. Next, sets of DER
capacity additions that achieve the greatest network performance
improvement under those future conditions are developed as
described above and illustrated in FIG. 3. Next, these DER capacity
additions are characterized as Optimal DER Portfolio projects, as
described above and illustrated in FIG. 4. In Block 4024 those
additional Optimal Portfolio DER projects that must be added to
accommodate future conditions are identified, along with when they
must be operational.
[0167] The result, in Block 4026, is the Optimal DER Portfolio for
the subject network. This Optimal DER Portfolio is a list of DER
projects, specifically dispatchable demand reduction, capacitors,
and generation. These projects are characterized in terms of their
size, location in the network, operating profile, and when they
must be operational. These projects offer the greatest potential
for network performance improvement given the conditions and
limitations of the analysis.
[0168] Quantification of Network Benefits Attributable to Optimal
DER Portfolio Projects
[0169] According to one embodiment of the present invention, the
value of the potential network benefits yielded by the Optimal DER
portfolio is determined. FIG. 5 is a flowchart illustrating this
process.
[0170] In Block 502 the condition of the Energynet with and without
the Optimal DER Portfolio projects is compared using the selected
analytical tools.
[0171] According to one embodiment of the present invention, the
improvement in system stability and voltage security is evaluated
qualitatively by one skilled in the art by observing the voltage
profiles in the Energynet load flow results with and without the
Optimal DER Portfolio projects.
[0172] According to another embodiment of the present invention,
the improvement in system stability and voltage security is
assessed more rigorously by performing stability studies upon the
Energynet datasets with and without the Optimal DER Portfolio
projects using methods well known in the art.
[0173] According to yet another embodiment of the present
invention, an analytical tool with the capability to directly
assess voltage security or proximity to voltage collapse is used.
This permits a direct measurement of the change in voltage security
or the change in proximity to voltage collapse by comparing the
Energynet with and without the Optimal DER Portfolio projects.
[0174] In Block 504 the aggregate reduction in real power losses
attributable to the Optimal DER Portfolio projects is readily
observable from the results from Block 502. In Block 506 the
aggregate reduction in reactive power losses attributable to the
Optimal DER Portfolio projects is readily observable from the
results from Block 502.
[0175] According to one embodiment of the present invention,
Energynet datasets corresponding to different network conditions
are prepared as described above. Thus, the variation in network
performance improvement achieved by the Optimal DER Portfolio
projects under different network conditions may be assessed by
comparing results for Energynet datasets corresponding to those
different network conditions with and without the Optimal DER
Portfolio projects, incorporating the operational adjustments and
dispatch schemes developed in Block 4022.
[0176] In Block 508 the increase in the network's load-serving
capability attributable to the Optimal DER Portfolio projects is
evaluated. According to one embodiment of the present invention,
the increase in load-serving capability of the Energynet
attributable to the Optimal DER Portfolio projects is determined by
increasing loads in the Energynet datasets with and without the
Optimal DER Portfolio projects to the point of overload, according
to conventional method in the art.
[0177] Under another embodiment of the present invention, the
increase in load-serving capability of the Energynet attributable
to the Optimal DER Portfolio projects is assessed by comparing the
performance of the Energynet using datasets reflecting expected
future conditions, with load growth, with the Optimal DER Portfolio
projects on one hand and, on the other hand, with network
improvements otherwise contemplated to accommodate these expected
future conditions.
[0178] According to one embodiment of the present invention, any of
these assessments of the Energynet performance with and without the
Optimal Portfolio projects are also made for groups of Optimal DER
Portfolio projects or individual projects from the Optimal
Portfolio. It should be noted that because the impact of elements
of the network may be closely coupled, it does not necessarily
follow that the performance improvement attributable to the Optimal
Portfolio as a whole equals the sum of the performance improvement
attributable to groups of Optimal Portfolio projects or individual
projects.
[0179] According to one embodiment of the present invention, the
network performance improvement attributable to the Optimal DER
Portfolio projects is now assessed in financial terms.
[0180] In Block 5010, according to one embodiment of the present
invention reductions in real power losses attributable to the
Optimal DER Portfolio projects are valued based on the spot market
value of the energy gained.
[0181] In Block 5012, according to one embodiment of the present
invention reductions in reactive power losses attributable to the
Optimal DER Portfolio projects are valued based on the cost of
capacitors that would be required to provide the same amount of
reactive power.
[0182] In Block 5014 according to one embodiment of the present
invention increases in the load-serving capability of the Energynet
attributable to the Optimal DER Portfolio projects are valued based
on the cost of traditional network additions, such as wires and
transformers, that would be required to serve the same load. Under
another embodiment of the method of the present invention increases
in the load-serving capability of the Energynet attributable to the
Optimal DER Portfolio projects are valued based on the market value
of reserves that are effectively created.
[0183] Increases in system stability or voltage security are not
directly priced, but are indirectly reflected in the value
associated with reduced real and reactive power losses and
increased load-serving capability.
REFERENCE NUMERALS
[0184] 102 DER with customer benefits [0185] 104 DER projects with
environmental benefits [0186] 106 DER projects with network
benefits [0187] 202 selection of network conditions for analysis
[0188] 204 transmission dataset [0189] 206 determination of
availability of impedances of loads and elements of distribution
feeders from compatible dataset [0190] 208 engineering and
operational data [0191] 2010 derivation of impedances of loads and
elements of distribution feeders derived from engineering and
operational data [0192] 2012 evaluation to ensure consistency of
distribution data and transmission data [0193] 2014 incorporation
and verification of distribution element interconnections and
switch positions [0194] 2016 incorporation of distribution
impedance data with transmission data [0195] 2018 adjustments to
combined dataset [0196] 2020 Energynet dataset representing subject
network under the selected conditions [0197] 302 characterization
of integrated transmission and distribution network under the
conditions selected for analysis before addition of DER. [0198] 304
external limits on real capacity additions [0199] 306 formulation
and incorporation of alternative DER capacity additions [0200] 308
reassessment of dataset with DER additions [0201] 3010 comparison
of Energynet performance with base case [0202] 3012 revision of DER
capacity additions that do not improve Energynet performance [0203]
3014 determination if further DER additions will yield meaningful
performance improvement [0204] 3016 DER capacity additions yielding
the greatest evaluated reduction in losses, improvement in power
quality, and improvement in network stability and voltage security.
[0205] 402 real capacity DER additions representing dispatchable
demand reduction [0206] 404 reactive capacity DER additions
representing capacitors [0207] 406 DER additions of real and
reactive power capacity together representing power generators
[0208] 408 dispatchable demand reduction DER projects [0209] 4010
aggregation or disaggregation of reactive capacity additions into
for DER projects matching available capacitors [0210] 4012
aggregation or disaggregation of additions of real and reactive
capacity together into DER projects matching available power
generators [0211] 4014 provisional Optimal DER Portfolio projects
[0212] 4016 update of Energynet dataset for aggregated or
disaggregated capacity [0213] 4018 determination of any significant
impacts of aggregation or disaggregation on Energynet performance
[0214] 4020 appropriate revisions to Energynet dataset and capacity
additions [0215] 4022 operational adjustments and dispatch schemes
for Optimal DER Portfolio projects [0216] 4024 DER projects to
accommodate future conditions [0217] 4026 final Optimal DER
Portfolio for the subject network [0218] 502 comparison of
Energynet condition with and without the Optimal DER Portfolio
projects [0219] 504 determination of aggregate reduction in real
power losses attributable to the Optimal DER Portfolio projects
[0220] 506 determination of aggregate reduction in reactive power
losses attributable to the Optimal DER Portfolio projects [0221]
508 determination of increase in the network's load-serving
capability attributable to the Optimal DER Portfolio projects
[0222] 5010 valuation of reductions in real power losses
attributable to Optimal DER Portfolio projects [0223] 5012
valuation of reductions in reactive power losses attributable to
Optimal DER Portfolio projects [0224] 5014 valuation of increase in
network's load-serving capability attributable to Optimal DER
Portfolio projects [0225] 5016 engineering and economic valuation
of network benefits attributable to Optimal DER Portfolio
projects
[0226] As indicated above, Space 106 of FIG. 1 represents those DER
projects that provide benefits to the performance of the T&D
network. The set of DER projects represented by Space 106 is
distinct from the set of DER projects represented by Space 104,
those projects with environmental benefits. The set of DER projects
represented by Space 106 is distinct from the set of DER projects
represented by Space 102, those projects with benefits for
customers.
[0227] There may be, and likely are, DER projects that benefit the
subject T&D network and also benefit either the environment,
customers, or both. In operation, an objective identification of
those DER projects that benefit the T&D network, apart from the
influence of customer or environmental considerations according to
the method of this invention, is a necessary precursor to
identifying those projects that share that attribute with other
benefits.
[0228] The method of the present invention involves the preparation
of an Energynet dataset, as described above and illustrated in FIG.
2. The Energynet dataset for the subject T&D network is an
integrated mathematical representation of integrated transmission
and distribution elements and their interconnection, with the
capability to incorporate additions of real capacity, reactive
capacity, and real and reactive capacity together at any point in
the network. Block 2020 of FIG. 2 represents the Energynet dataset
for the subject T&D network for a particular set of
conditions.
[0229] In operation, the use of such an Energynet dataset overcomes
many of the disadvantages of traditional analysis methods used for
transmission systems or distribution systems, in particular their
disadvantages as they relate to assessing the impact of DER.
Analysis using an Energynet dataset permits the direct observation
of the extent to which problems at the transmission level arise
from or are exacerbated by problems at the distribution level (and
vice versa), and the merits of remedying problems at either the
transmission or the distribution level with changes at either
level; in particular, the merits of DER additions at the
distribution level to remedy problems of the overall network.
[0230] According to one embodiment of the present invention, the
Energynet dataset, once constructed, is analyzed using a suitably
programmed computer incorporating commercially-available "load
flow" programs traditionally used in the art for analyzing
transmission systems. These tools are used initially to
characterize the condition of the Energynet "as found," or prior to
any changes according to the method. These tools are also used to
evaluate the impact on the condition of the Energynet of any
changes to the Energynet; in particular, the addition of DER
capacity anywhere in the network as described below.
[0231] In Block 302, analysis of the resulting Energynet dataset of
Block 2020 using load flow tools yields a characterization of the
integrated transmission and distribution network under the
conditions selected for analysis.
[0232] Such load flow tools will characterize the power flows,
losses, voltage profile, and power factor within the integrated
transmission and distribution network represented by the Energynet
dataset, in this case before the addition of any DER.
[0233] Some power system analysis tools may have the capability to
evaluate (not just characterize) the voltage profile of the network
being analyzed and/or determine the proximity to voltage collapse
or voltage security of the network being analyzed. If such analysis
tools are applied to an Energynet dataset according to the method
of this invention, results will include an evaluation of the
voltage profile and/or the proximity to voltage collapse or voltage
security across the transmission and distribution portions of the
integrated network represented by the Energynet dataset.
[0234] In operation, one benefit of the method of this invention is
that load flow results from an Energynet dataset will reveal the
extent to which deficiencies known at the transmission level are
actually the accumulation of deficiencies at the distribution
level, as well as reveal new deficiencies within the distribution
portion of the network that only reveal themselves through this
type of analysis.
[0235] Further, evaluation of the load flow results for the
integrated Energynet dataset by those skilled in the art may
identify different settings for control variables that will yield
improved network performance.
[0236] Developing several Energynet datasets representing the
integrated network under a variety of conditions (or alternatively,
developing Energynet datasets for different system conditions by
modifying one Energynet dataset) permits the observation of the
conditions of the entire network under changing circumstances.
This, in turn, permits the development of control schemes and
procedures that more thoroughly respond to conditions throughout
the network. This also readily permits an evaluation of the merits
of automated network controls, more comprehensive monitoring of
network conditions, and more sophisticated demand management
schemes.
[0237] Because the Energynet dataset includes representations of
any looped distribution feeders with switchable connections, The
Energynet dataset provides the means to readily evaluate the merits
of switching the feeders serving particular loads under different
operating conditions.
[0238] In operation, use of the Energynet dataset prepared as
described above and represented by Block 2020 to develop a set of
DER capacity additions as described above and represented by Block
3014 permits a comprehensive evaluation of all the possibilities in
terms of DER capacity additions, as well as the interplay between
them, in all parts of the subject network, and permits
consideration of the impact of different potential DER additions on
a broad set of network performance criteria.
[0239] As described above, potential DER capacity additions include
additions of real capacity, additions of reactive capacity, and
additions of real capacity together with reactive capacity. These
are evaluated as interchangeable alternatives.
[0240] Alternative DER capacity additions are evaluated for their
impact on losses in the subject network, but also for their impact
on factors affecting power quality and network stability or voltage
security. In practice, small differences in the DER capacity
additions considered may affect their impact on these other
factors.
[0241] The method of the present invention may be carried out with
any one of a number of commercially-available transmission network
analysis tools known in the art. The minimum requirement is that
they be capable of characterizing the Energynet dataset under a
given set of conditions. However, the enormous range of
possibilities and flexibility inherent in alternative DER capacity
additions places new demands on these tools--demands that are not
evident in traditional transmission system analysis.
[0242] Network analysis tools capable of detecting and quantifying
differences between many different sets of DER capacity additions,
particularly in terms of their impact on network stability and
voltage security, will yield better results more quickly when
applied under the methodology of this invention.
[0243] According to one embodiment of the present invention, the
set of DER capacity additions determined in Block 3014, as real
capacity additions, reactive capacity additions, and real and
reactive capacity additions together, are characterized as specific
DER projects in an Optimal DER Portfolio, as described above. The
result, in Block 4026, is the Optimal DER Portfolio for the subject
network.
[0244] The Optimal DER Portfolio is a list of DER projects,
specifically dispatchable demand reduction, capacitors, and
generation. These projects are characterized in terms of their
size, location in the network, and when they must be operational.
They are also characterized in terms of how they should operate
under different conditions. This set of projects offer the greatest
potential for network performance improvement given the conditions
and limitations of the analysis.
[0245] This element in the method of the present invention may not
add to the overall potential network benefits determined to be
available through the implementation of DER. In practice, knowledge
of the particular DER projects that would realize these benefits
characterized as described above, makes the result far more
useful.
[0246] If generating projects similar to those in the Optimal DER
Portfolio are developed by third parties, the method of the present
invention provides information on the operating profile required
for those units to permit them to make the greatest contribution to
network performance under varying system conditions. This
information informs the utility as to the degree of control of a
third-party the utility can benefit from and what the contractual
terms between the utility and the project sponsor should be.
[0247] The Optimal DER Portfolio includes dispatchable demand
response specified for particular locations in the network. In
addition, these specifications change for different network
conditions. This information goes far beyond the present basis in
the art for developing demand response programs. This information
would permit a utility to design a demand response program that
could request demand reductions in specific locations under
specific conditions to yield the most benefit to system
performance, in addition to or instead of simple energy demand
reduction. Such programs could be both less invasive for customers
and more valuable to utilities.
[0248] The Optimal DER Portfolio also includes specifications for
reactive capacity additions in specific locations within the
network under various conditions. Utilities may use this
information to conclude that there is value in more flexible
reactive capacity devices.
[0249] It is conceivable that an Energynet dataset could be used in
an operating setting, with loads input from monitors on the system,
to manage programs of this sort.
[0250] The projects in the Optimal DER Portfolio are sufficiently
characterized to determine the interconnection and regulatory
requirements they would be required to satisfy. While the prime
movers for the generating facilities are not specified, one skilled
in the art can determine what might be appropriate given the
operating profile of each project.
[0251] These projects are, according to the method of this
invention, the projects that can realize the greatest contribution
to network performance. It follows, then, that the interconnection
requirements of these projects and the permitting requirements for
these projects are the requirements that are the most consequential
from the standpoint of improving network performance.
[0252] The Optimal DER Portfolio projects may be used to identify
those consequential requirements. Once identified, these
requirements are readily evaluated by those skilled in the art for
the barriers they may represent to these projects. A reasonable way
to orient policies and initiatives intended to remove barriers to
the implementation of DER is to focus on barriers having the
greatest impacts on the set of projects that has the greatest
potential to benefit network performance.
[0253] According to one embodiment of the present invention, the
value of the potential network benefits yielded by the Optimal DER
portfolio is determined in engineering and monetary terms as
described above and illustrated in FIG. 5.
[0254] As described above, in Block 508 the increase in the
network's load-serving capability attributable to the Optimal DER
Portfolio projects is evaluated. This information could be used by
a utility to identify planned network improvements, specifically
new transmission and distribution lines that may be deferred or
avoided through expanded deployment of DER projects similar to
those in the Optimal DER portfolio. The Energynet dataset and the
method of the present invention provides a convenient means to
analyze different combinations of network additions and DER
projects for their impact across the network on a variety of
factors.
[0255] The monetary value of the avoided real and reactive power
losses and increased load-serving capability attributable to the
Optimal DER Portfolio represents an incremental source of economic
support for DER projects. Many utilities and public service
commissions have implemented financial incentives to promote
development of distributed generation, and even more commonly,
demand response. While these programs are perceived to benefit all
customers, the linkage is not rigorous. It remains possible that
some portion of these programs is essentially funded by shifting
the cost to non-participating customers.
[0256] The value of the network benefits the Optimal DER Portfolio
projects is the financial quantification of incremental network
benefits that demonstrably accrue to all customers on the network
if projects similar to these are developed. Thus, financial
incentives for DER may be developed based on the sharing of this
value. Such financial incentives would demonstrably benefit the
network operator, the project participants, and non-participating
customers.
[0257] Because the Optimal DER Portfolio projects are characterized
in such detail, financial incentives designed around the potential
value they represent may be highly targeted. For example, using a
method according to one embodiment of the present invention, a
utility may determine that a generating unit of a certain size,
interconnected at a particular voltage level in a particular
location within the network, with a particular operating profile
and with a certain level of control by the utility is worth a
certain dollar amount to the network.
[0258] It should be noted that the network benefits attributable to
the Optimal DER Portfolio are, in general, attributable to the
portfolio as a whole. If the impacts of the units are closely
coupled, it may not be valid to allocate these benefits to
individual projects. The values allocable to individual projects,
if properly assessed, may not be as great as the whole. However, it
should be apparent in the application of the methodology of this
invention, which projects have the greatest impact. It may also be
possible for one skilled in the art to judge a reasonable share of
the total benefit attributable to individual projects or groups of
projects. Finally, incentives designed to share value rather than
give it away entirely, permit some margin for error.
[0259] The method of the present invention characterizes the
improvements in network stability and voltage security, and by
inference the improvement in power quality, attributable to the
Optimal DER Portfolio. As the art advances, means to assign
monetary value to improvements in network stability or power
quality may gain acceptance. It is conceivable that at some point
these considerations could be incorporated directly in
value-sharing incentives promoting DER that benefits the
network.
[0260] The methods employed could be further used for the following
purposes: [0261] Simulation of the Energynet under a great variety
of load conditions to determine appropriate operational responses
for embedded DER to maintain optimum network conditions. These
results could be used to: [0262] design network control and
feedback requirements for DER [0263] establish contractual control
provisions between the network operator and DER operators [0264]
Assessment of the benefits of more extensive network monitoring,
particularly at the distribution level, and the use of feedback
such monitoring would provide. [0265] Assessment of the benefits of
automated switching capability, to allow switching of loads from
one feeder to another during operation to maintain network
performance. [0266] Quantification of the potential for overall
efficiency and power quality gains through active management of the
network, particularly at the distribution voltage level. [0267]
Assessment of the potential for distribution-connected DER to defer
or avoid transmission-level network additions.
[0268] Analysis of the network as integrated transmission and
distribution, and the use of transmission analysis tools for such
an integrated network represent significant departures from current
practice. Moreover, analysis of T&D networks as integrated
networks, combining transmission and distribution elements, and
with provision for embedded DER, for assessing the potential for
network performance improvement using DER, for determining
operating protocols for DER and other network elements, and for
other purposes, overcomes significant disadvantages of the prior
art.
[0269] Analysis using an integrated network model allows the direct
observation of the degree to which problems observed at the
transmission level are actually the accumulation of problems at the
distribution level, or vice versa. Analysis of the incorporation of
DER in the network using an integrated network model allows the
direct observation of the merits of mitigating network problems in
a decentralized fashion close to their source, rather than in an
aggregated fashion at the transmission level, perhaps far from
their source.
[0270] Analysis of potential DER additions using a network model
integrating transmission and distribution under different network
conditions permits demonstration of how network conditions affect
the entire network and how DER operational profiles must be
tailored or managed to maintain network performance. Analysis of a
network using an integrated model permits direct demonstration of
the effects across the network and potential merits of switching
loads between looped distribution feeders as one tool for enhancing
network performance.
[0271] While particular embodiments and applications of the present
invention have been illustrated and described herein, it is to be
understood that the invention is not limited to the precise
construction and components disclosed herein and that various
modifications, changes, and variations may be made in the
arrangement, operation, and details of the methods and apparatuses
of the present invention without departing from the spirit and
scope of the invention as it is defined in the appended claims.
* * * * *