U.S. patent application number 15/800268 was filed with the patent office on 2018-04-05 for systemic optimization of photovoltaic apparatus.
This patent application is currently assigned to SunPower Corporation. The applicant listed for this patent is SunPower Corporation. Invention is credited to Robert Batten, Ravindranath Naiknaware.
Application Number | 20180097360 15/800268 |
Document ID | / |
Family ID | 60255823 |
Filed Date | 2018-04-05 |
United States Patent
Application |
20180097360 |
Kind Code |
A1 |
Batten; Robert ; et
al. |
April 5, 2018 |
SYSTEMIC OPTIMIZATION OF PHOTOVOLTAIC APPARATUS
Abstract
A photovoltaic system may include a first photovoltaic component
having local power optimization functionality to process power at a
first level, a second photovoltaic component to process power at a
second level, and optimization logic to command the first
photovoltaic component to accommodate system-level power
optimization. The first component may be reconfigurable to
accommodate the system-level optimization. The entire system may be
dynamically reconfigured to continuously operate at the highest
overall level of system efficiency.
Inventors: |
Batten; Robert; (Tualatin,
OR) ; Naiknaware; Ravindranath; (Portland,
OR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SunPower Corporation |
San Jose |
CA |
US |
|
|
Assignee: |
SunPower Corporation
San Jose
CA
|
Family ID: |
60255823 |
Appl. No.: |
15/800268 |
Filed: |
November 1, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13005482 |
Jan 12, 2011 |
9819182 |
|
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15800268 |
|
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61294464 |
Jan 12, 2010 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02J 3/383 20130101;
Y04S 10/123 20130101; Y02E 40/70 20130101; Y10T 307/707 20150401;
H02J 3/38 20130101; H02J 1/102 20130101; H02J 1/08 20130101; H02J
3/381 20130101; Y02E 10/56 20130101; H02J 13/0075 20130101; H02J
2300/24 20200101; Y04S 40/126 20130101; H02J 1/10 20130101 |
International
Class: |
H02J 1/10 20060101
H02J001/10; H02J 3/38 20060101 H02J003/38 |
Claims
1.-46. (canceled)
47. A process for system-level optimization of a photovoltaic
system comprising: operating a decision engine at a microprocessor,
the decision engine configured to consider optimum power
configuration information for a plurality of local power optimizers
of a photovoltaic system, the decision engine configured to
consider optimum power configuration information for one or more
centralized inverters; updating the optimum power configuration
information for the plurality of local power optimizers; and
updating the optimum power configuration information for one of
more centralized inverters, wherein the decision engine is remote
from the one or more centralized inverters and is remote from the
plurality of local power optimizers.
48. The process of claim 47 further comprising: sending updated
power configuration information for the plurality of local power
optimizers or the one or more centralized inverters or both to a
gateway, the gateway configured to communicate with the plurality
of local power optimizers or the one or more centralized inverters
or both.
49. The process of claim 48 further comprising: at the decision
engine, determining operating points of one or more of the local
power optimizers from the plurality of local power optimizers.
50. The process of claim 47 wherein each of the local power
optimizers of the plurality of local power optimizers is at a
microinverter coupled to one or more strings of photovoltaic
cells.
51. The process of claim 47 wherein the local power optimizers are
connected in a reconfigurable manner such that the local power
optimizers may be connected to each other in series for one
configuration and may be connected to each other in parallel for a
second configuration.
52. The process of claim 48 wherein the microprocessor is
configured and positioned to communicate to the gateway via the
Internet.
53. The process of claim 48 wherein the gateway or the
microprocessor or both are configured and positioned to be in
communication with a pyranometer.
54. The process of claim 47 further comprising: considering demand
side management information at the microprocessor, the demand side
management information indicative of ongoing operation of a power
grid being supplied by the photovoltaic system.
55. A computer storage device containing instructions stored
thereon, the instructions when run by a microprocessor, cause the
microprocessor to carry out a process comprising: operating a
decision engine, the decision engine configured to consider optimum
power configuration information for a plurality of local power
optimizers of a photovoltaic system, the decision engine configured
to consider optimum power configuration information for one or more
centralized inverters; updating the optimum power configuration
information for the plurality of local power optimizers; and
updating the optimum power configuration information for one of
more centralized inverters, wherein the decision engine is remote
from the one or more centralized inverters and is remote from the
plurality of local power optimizers.
56. The computer storage device of claim 55 where the instructions
also cause the microprocessor to perform steps comprising: sending
updated power configuration information for the plurality of local
power optimizers or the one or more centralized inverters or both
to a gateway, the gateway configured to communicate with the
plurality of local power optimizers or the one or more centralized
inverters or both.
57. The computer storage device of claim 56 where the instructions
also cause the microprocessor to perform steps comprising: at the
decision engine, determining voltage operating points of one or
more of the local power optimizers from the plurality of local
power optimizers.
58. The computer storage device of claim 55 wherein each of the
local power optimizers of the plurality of local power optimizers
is at a microinverter coupled to one or more strings of
photovoltaic cells.
59. The computer storage device of claim 55 wherein the local power
optimizers are connected in a reconfigurable manner such that the
local power optimizers may be connected to each other in series for
one configuration and may be connected to each other in parallel
for a second configuration.
60. The computer storage device of claim 56 wherein the
microprocessor is configured and positioned to communicate to the
gateway via the Internet.
61. The computer storage device of claim 56 wherein the gateway or
the microprocessor or both are configured and positioned to be in
communication with a pyranometer.
62. The computer storage device of claim 55 where the instructions
also cause the microprocessor to perform steps comprising:
considering demand side management information at the
microprocessor, the demand side management information indicative
of ongoing operation of a power grid being supplied by a
photovoltaic system.
63. A computer microprocessor configured to carry out a process
comprising: operating a decision engine, the decision engine
configured to consider optimum voltage configuration information
for a plurality of local power optimizers of a photovoltaic system,
the decision engine configured to consider optimum voltage
configuration information for one or more centralized inverters;
updating the optimum configuration information for the plurality of
local power optimizers; and updating the optimum configuration
information for one of more centralized inverters, wherein the
decision engine is remote from the one or more centralized
inverters and is remote from the plurality of local power
optimizers.
64. The computer microprocessor of claim 63 where the
microprocessor is also configured to perform steps comprising:
sending updated configuration information for the plurality of
local power optimizers or the one or more centralized inverters or
both to a gateway, the gateway configured to communicate with the
plurality of local power optimizers or the one or more centralized
inverters or both.
65. The computer microprocessor of claim 64 where the
microprocessor is also configured to perform steps comprising: at
the decision engine, determining operating points of one or more of
the local power optimizers from the plurality of local power
optimizers.
66. The computer microprocessor of claim 63 wherein each of the
local power optimizers of the plurality of local power optimizers
is at a microinverter coupled to one or more strings of
photovoltaic cells.
67. The computer microprocessor of claim 63 wherein the local power
optimizers are connected in a reconfigurable manner such that the
local power optimizers may be connected to each other in series for
one configuration and may be connected to each other in parallel
for a second configuration.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 13/005,482, which was filed on Jan. 12, 2011 and is entitled
Systemic Optimization of Photovoltaic Apparatus. The '482
application claims priority from U.S. Provisional Patent
Application Ser. No. 61/294,464 titled Systemic Optimization of
Solar Arrays filed Jan. 12, 2010.
BACKGROUND
[0002] Photovoltaic (PV) systems typically include components
having local power optimization features. For example, PV panels
may be equipped with local power optimizers that perform DC-to-DC
conversion with maximum power point tracking (MPPT) to keep the
panel operating at its peak power level. Likewise, a centralized
inverter may also include an MPPT algorithm that is designed to
optimize the operating level of the PV array as seen from the
inverter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] FIG. 1 illustrates a generalized embodiment of a PV system
according to some inventive principles of this patent
disclosure.
[0004] FIG. 2 illustrates a generalized embodiment of a PV
component according to some inventive principles of this patent
disclosure.
[0005] FIG. 3 illustrates an example embodiment of a PV
installation according to some inventive principles of this patent
disclosure.
[0006] FIG. 4 illustrates an example embodiment of a PV component
according to some inventive principles of this patent
disclosure.
[0007] FIG. 5 illustrates an example embodiment of a PV system
capable of system-level optimization according to some inventive
principles of this patent disclosure.
[0008] FIG. 6 illustrates an example embodiment of a PV system
using string-level power optimizers to implement system-level
optimization according to some inventive principles of this patent
disclosure.
[0009] FIG. 7 illustrates another example embodiment of a PV system
using string-level power optimizers to implement system-level
optimization according to some inventive principles of this patent
disclosure.
[0010] FIG. 8 illustrates an example embodiment of a PV panel
having sub-strings that can be reconfigured according to some
inventive principles of this patent disclosure.
DETAILED DESCRIPTION
Systemic Optimization
[0011] As discussed above, photovoltaic (PV) systems typically
include components having local power optimization features.
However, having a component that is locally optimized from its own
perspective may not actually cause the entire system to operate at
overall peak efficiency. Moreover, uncoordinated local optimization
may fail to take into account real world effects such as
temperature changes, shading issues, panel mismatches, and inverter
efficiency curves.
[0012] For example, a PV array may have several strings of PV
panels where each panel includes a local power optimizer. The
combined outputs from the locally optimized panels may provide a
certain voltage and current to a centralized inverter. Depending on
its efficiency curve, however, the inverter may be operating
substantially below its peak efficiency level. According to some
inventive principles of this patent disclosure, the operating
points of the local power optimizers may be moved away from their
local maximum points to provide a combined voltage and current that
enable the centralized inverter to operate at a higher efficiency
level. Depending on the implementation details, a large increase in
the efficiency of the inverter may more than compensate for smaller
efficiency reductions at the panels.
[0013] This is just one example of the inventive principles of this
patent disclosure which involve a systemic approach to power
optimization wherein the operation of components at multiple levels
are adjusted to provide better overall system-level optimization.
This patent disclosure includes numerous example methods and
apparatus for illustrating the systemic power optimization
principles. The inventive principles, however, are not limited to
these examples. Moreover, the inventive principles may be combined
to provide additional synergistic solutions.
[0014] FIG. 1 illustrates a generalized embodiment of a PV system
according to some inventive principles of this patent disclosure.
The embodiment of FIG. 1 includes one or more first PV components
10 having local power optimization functionality (LPO) 12 to
process power at a first level L1. One or more second photovoltaic
components 14 process power at a second level L2. The second
photovoltaic components 14 may also include local power
optimization functionality (LPO) 16. Power may flow in either
direction between levels L1 and L2 is shown by arrow 11. Power may
also flow in either direction between levels L1 and L2 and any
other levels or apparatus that may exist as shown by arrows 13 and
15.
[0015] The levels may be implemented with any suitable arrangement
of PV apparatus such as cells, strings of cells within a panel,
panels, strings of panels, inverters, etc. For example, in some
embodiments, the first level may be implemented as a panel level,
while the second level is implemented as a centralized inverter
level. Another example may include three levels in which cells,
panels and inverters each form a level. Thus, the inventive
principles are not limited to any specific number or configuration
of levels.
[0016] The system also includes optimization logic 18 to command
one or more of the first photovoltaic components 10 and/or one or
more of the second photovoltaic components 14 to accommodate
system-level power optimization. The optimization logic may
coordinate the operation of the local power optimization
functionality of the first and second photovoltaic components.
Although shown with two levels, the system may include any number
of levels.
[0017] When used in the context of a PV component, the term
"system-level" refers to any level that is higher or more
widespread than the level of the component. For example, a
panel-level power optimizer may include remote processing
functionality to accommodate system-level optimization. Such
system-level optimization may operate on the string level, array
level, etc.
[0018] In some embodiments, one or more of the components 14, 16,
etc., may be capable of reconfiguring themselves to alter their
operation as described in more detail below. Thus, the optimization
logic 18 may include logic to command any of the photovoltaic
components to reconfigure themselves if they are capable.
[0019] FIG. 2 illustrates a generalized embodiment of a PV
component 22 according to some inventive principles of this patent
disclosure. The embodiment of FIG. 2 may be suitable for use as any
of the PV components shown in FIG. 1 and includes a power train 24,
local power optimization functionality 26 arranged to control the
power train, and remote command processing functionality 28 to
accommodate system-level power optimization. The remote command
processing functionality 28 may be adapted to adjust the operation
of the local power optimization functionality 26 in response to a
remote command from, for example, the optimization logic 18 shown
in FIG. 1.
[0020] The local power optimization functionality 26 may include
local MPPT functionality, and the remote command processing
functionality 28 may be adapted to modify the functionality of the
local MPPT functionality in response to commands received from,
e.g., the optimization logic 18 shown in FIG. 1. For example, the
functionality may be modified by adjusting or overriding
parameters.
[0021] The power train 24 may be reconfigurable. For example, if
the PV component is implemented as a cell-level component, the
power train may include a bypass device such as a bypass diode or
transistor that may be used to bypass a cell having a low output,
e.g., because of being shaded, broken, hot, etc. A bypass device
may also be used to improve efficiency when no power conditioning
is needed. For example, if all of the cells in a panel and/or
panels in an array are in good operating condition and subject to
the same high level of radiation, e.g., full sunlight, bypass mode
may be used for all devices to reduce or eliminate power losses due
to local power processing.
[0022] Alternatively, the power train may be reconfigurable through
one or more switches or an entire switching matrix that enables PV
cells, panel sub-strings, panels or strings of panels to be
re-connected in series or parallel in response to a remote
command.
[0023] In some embodiments, the remote command processing
functionality 28 may include phase shedding functionality. For
example, in an embodiment having multi-phase DC-DC converters, one
or more phases may be dropped to reduce control losses when
operating lower power levels.
[0024] An example of a generalized embodiment of a method for
operating a multi-level photovoltaic system according to the
inventive principles of this patent disclosure includes: (1)
operating a photovoltaic system having a first photovoltaic
component to process power at a first level and a second
photovoltaic component to process power at a second level, and (2)
dynamically configuring at least one of the first and second
photovoltaic components. Although described in the context of two
levels, a multi-level photovoltaic system according to the
inventive principles of this patent disclosure may include any
suitable number of levels.
[0025] The dynamic configuring may be in response to one or more
environmental conditions such as temperature, shading, wind
exposure and airflow. The dynamic configuring may also be in
response to one or more other system components. For example, the
dynamic configuring may occur in response to installation of the
one or more other system components, in response to normal
operation of the system, and/or to aging of one or more components.
As another example, the dynamic configuring may be in response to
demand side management commands received from a utility.
[0026] In some embodiments, the dynamic configuring may include
calculating efficiencies for different configurations, and
selecting the most efficient of the different configurations. Some
additional examples of dynamic configuring are as follows:
bypassing a local power optimizer, overriding the local MPPT
functionality of a component, and/or reconnecting one or more
components, as between series or parallel connections.
[0027] Another example of a generalized embodiment of a method for
operating a photovoltaic system according to the inventive
principles of this patent disclosure includes: (1) determining an
environmental condition of the photovoltaic system, (2) correlating
the determined environmental condition to historical measurements
of the system, and (3) optimizing the operation of the system in
response to the historical measurements.
[0028] Optimizing the operation of the system may include
calibrating one or more components. In some embodiments, the
environmental condition may include a meteorological condition, and
the historical measurements may include meteorological data.
[0029] The environmental condition may also include a
forward-looking meteorological condition, and optimizing the
operation of the system may include anticipating a reduction in
system power in response to the forward-looking meteorological
condition. In such a case, the anticipated reduction in system
power may be communicated to the utility that operates the grid to
which the PV system may be connected.
Implementation Techniques
[0030] The following techniques may be used for implementing the
general methods, systems and components described above, but the
inventive principles are not limited to these techniques.
[0031] According to some inventive principles of this patent
disclosure, designing system level monitoring and control into a PV
system may enable it to achieve better efficiency and increased
power output. The more areas of control that are available to the
system, the more possibilities are available for optimization. The
following are some example embodiments of hardware and
optimizations at various system levels starting with the cell level
and working back to the grid.
[0032] This generally assumes that there is a central control
system that has communication with all the parts of the PV system,
but the inventive principles are not limited to systems having
these conditions.
[0033] At the cell level, methods to bypass cells having low output
due to shading, breakage, high operating temperature, etc, include
the use of bypass diodes and transistors, specifically, FETs. A
DC-DC converter may also be used at each cell to improve the
capacity for system-level optimization.
[0034] At the panel substring level, breaking the panel up into
more substrings and performing DC-DC conversion at the substring
level may provide finer granularity for shading/mismatch control.
The use of local substring DC-DC converters may enable optimization
at the panel sub-string or panel level through the use of phase
shedding as a function of power handled.
[0035] Optimization at the panel sub-string or panel level may also
enable the use of full bypass (of the local power optimizers) if
the entire system is operable at the maximum efficiency without the
local power optimizers. This may occur, for example, if the entire
system is operating under close to ideal conditions, e.g., no
shadowing, close matching of cells and panels, ideal tilt,
significant insolation, etc.
[0036] Another potential benefit of the use of optimization at the
panel sub-string or panel level is that the output current and
voltage may be controlled to optimize the input voltage to a
centralized inverter. This may be implemented at the system level
to determine the inverter voltages and at what operating point the
system is most efficient, taking into account the efficiencies of
all the components of the system, e.g., at the panel level, string
level and inverter level.
[0037] The most efficient operating point may be determined as
follows. A system-level unit calculates possible efficiencies and
selects the most efficient to set the system to the optimal point.
The system level unit maintains a record of historical operating
conditions and can infer the ideal shading and temperature
variations over time and predict optimal points to avoid large
system upsets under changing conditions. The system level unit may
also communicate with a database to monitor weather forecasts and
seasonal conditions. Under large mismatch conditions, the system
level unit can turn off various sub-systems in an attempt to
increase the overall power output. It may also monitor panels that
have been turned off to determine when to turn them back on.
[0038] The system level unit may also use internal shading models
to predict when one or more units may be out of large mismatch
conditions and producing adequate power again by using data from
the operating conditions of previous days. In a situation where a
unit is off, the system may periodically turn the unit on to see if
it is back to normal. Storing this information as a function of
time may also provide information on which to base operations for
subsequent days. In units that have a buck or boost feature, the
system may tell the unit when to change mode, e.g., use boost mode
where a fraction of the strings are subject to heavy shading.
[0039] Optimization at the string level may be facilitated with
hardware installed in combiner boxes. String level MPPT units may
be combined for strings that become heavily shaded (from design
software analysis). When the voltage drops on these strings, they
may be switched from a parallel string combination to a series
string combination. This may allow a simpler buck style design
while still providing the advantages of a voltage boosting system.
This may also allow more flexibility with the inverter input
voltage, thereby allowing the system to run at more optimal points.
Moreover, many of the advantages described in the context of
optimization at the panel sub-string or panel level may also apply
to systems having optimization at the string level. A system level
command for operation may be useful, and adaptive phase shedding at
this level may also be a useful addition for increased
efficiency.
[0040] Optimizations at the inverter level may be implemented by
controlling the system voltage to take advantage of the inverter
maximum efficiency operating points. A variety of typically
competing constraints may be accommodated as follows. The maximum
bypassed system open circuit voltage (Voc) may need to be under a
predetermined limit, e.g., 600V/1000V over the entire operating
temperature range. Thus, this constraint may determine the maximum
number of panels in a string.
[0041] The inverter may also have a minimum input voltage limit.
This may set the minimum voltage ratio for a buck converter which,
in turn, relates to the total amount of shading a single string can
tolerate before dropping out.
[0042] The inverter may additionally have an upper limit on the MPP
voltage. This essentially may determine the bypass mode, maximum
panel MPP voltage for the string.
[0043] The above constraints may limit the operating range for the
system as well as how much shading can be tolerated. This, in turn,
may restrict the range throughout which the system can adjust the
system voltage for maximum inverter efficiency, especially under
shading conditions. Thus, the inventive principles enable the
balancing of tradeoffs between inverter efficiency and losing power
from good panels that are located in shaded strings.
[0044] According to some additional inventive principles of this
patent disclosure, system optimization may also be implemented at
the design phase for additional effectiveness. Optimization at the
design level may involve an analysis of shading which may be based
on an understanding of system shading and what effect it has on
performance over daily and annual time frames. Some of the shading
related factors that may be considered at the design level may
include the following: panel placement which includes position on
roof, installation angle, and orientation, choice of per panel
power optimizers, string wiring choices, choice of brand of
inverter, choice of number and size of inverters, return on
investment (ROI) on panels including an in-depth analysis with
appropriate software and information.
[0045] Optimization at the design level may involve modeling of
local heating effects caused by factors including: systems at site
such as heating ventilation and air conditioning (HVAC) units,
differences in wind exposure, differences in mounting styles,
volume of air under panel, air flow under the panel, etc.
[0046] Optimization at the design level may further involve an
analysis of tilt mismatches including having panels at different
tilts that do not match. The use of panel-level power optimizers,
however, may correct for tilt mismatches.
[0047] Optimization at the design level may further involve an
analysis based on system equipment choices. An analysis of the
panel choice may include factors such as initial panel cost, panel
ROI, and shading and temperature considerations. An analysis of the
inverter choice may include factors such as the panel type,
temperature variations, component sizing as discussed above, and
choice of panel optimizers. An analysis of the power optimizer
choice may include factors such as whether a power optimizer
provides any additional degrees of freedom in system design that
can result in increased efficiency.
Implementation Examples
[0048] FIG. 3 illustrates an example embodiment of a PV
installation according to some inventive principles of this patent
disclosure. The embodiment of FIG. 3 includes a PV array having
strings of series-connected PV panels 30 which, in turn, are
connected in parallel to form a DC bus V+,V-. Each of the PV panels
30 includes local power optimization functionality 32 and a local
communication module 33. A centralized inverter 34 converts the DC
power from the array to AC for feeding to a utility grid.
Irradiation and other weather sensors 38 provide real-time
meteorological data. Optimization logic 42 provides centralized
control for system-level optimization. The inverter, sensors and
logic include communication modules 36, 40 and 44, respectively,
which may communicate with each other, as well as the communication
modules 33 in the PV panels. The communication modules may use any
suitable communication medium and protocol.
[0049] FIG. 4 illustrates an example embodiment of a PV component
46 suitable for use as one of the PV panels 30 shown in FIG. 3, as
well as a string-level or other PV component according to some
inventive principles of this patent disclosure. The embodiment of
FIG. 4 includes a local panel-level, string-level or other level
power optimizer 48 having a power train 50. The power train is
reconfigurable such that it operates at maximum efficiency at
various power levels. This may be accomplished through various
strategies such as phase dropping or switching the converter into a
burst mode. The appropriate decision for configuring the power
train may be made locally using sense and control circuit 52.
However, as shown in FIG. 4, the communication module 56 may
receive remote commands for the optimum configuration of the power
train for system-wide optimization of the PV array. Any suitable
data transmission medium 58 such as wired, wireless, or power-line
communications (PLC) may be used to enable the communication module
56 to communicate with the other system components.
[0050] FIG. 5 illustrates an example embodiment of a PV system
capable of system-level optimization according to some inventive
principles of this patent disclosure. A PV array 60 may include PV
cells and/or strings of cells, PV panels or strings of PV panels,
etc., having communication modules 62 arranged for direct or mesh
communications through a gateway 64. One or more centralized
inverters 66 include communication modules 68 which also
communicate through the gateway 64. One or more pyranometers and/or
other weather station data sources 70 also include communication
modules 72 that communicate through the gateway 64.
[0051] Data from the array, inverter(s) and data sources may be
transmitted through the Internet or other suitable network and
stored on servers 74. The historical data obtained from the data
sources along with demand side management information 76 from a
smart-grid operator, historical meteorological data and localized
weather forecast information 78 may be used to determine the
optimum operation of the entire array. This may be accomplished,
for example, by using optimization logic 80 such as an intelligent
decision engine (or inference engine) running on a relatively high
performance remote computer. The computer may implement a decision
matrix that may contain optimum configuration information for each
of the local power optimizers in the PV array 60, as well as the
centralized inverter(s) 66. The optimum configuration information
may be updated continuously to enable an intelligent PV array
coordinating system to continuously operate at the optimum overall
efficiency.
[0052] In the embodiment of FIG. 5, the optimization logic is
remote from the PV components, that is, the optimization logic is
not embedded in any of the PV components. For example, the database
server 74 may be off-site from the array. Thus, the optimization
logic may determine operating points or modifications to the
parameters of one or more local power optimizers, or configuration
information for some or all of the PV components, then send the
operating points, parameters or configuration data back to the
components through the gateway or other communication
arrangement.
[0053] FIG. 6 illustrates an example embodiment of a PV system
using string-level power optimizers to implement system-level
optimization according to some inventive principles of this patent
disclosure. The embodiment of FIG. 6 may be used to implement, for
example, the array 60 and inverter(s) 66 shown in FIG. 5. In the
embodiment of FIG. 6, PV panels 82 are arranged in series-connected
strings S1, S2, . . . SN, each of which is interfaced to a DC bus
V+,V- through a local power optimizer 84. Each of the local power
optimizers includes a communication module 86. A centralized
inverter 88 also includes a communication module 90.
[0054] FIG. 7 illustrates another example embodiment of a PV system
using string-level power optimizers to implement system-level
optimization according to some inventive principles of this patent
disclosure. The embodiment of FIG. 7 is similar to the embodiment
of FIG. 6, but an array of smart switches S1-S5 enable the strings
to be re-connected in series or parallel configurations to
accommodate a wider variety of operating conditions, especially
non-ideal conditions. For example, the strings may normally be
configured for parallel operation under near-ideal irradiation and
other weather conditions. If any of the panels and/or strings
become shadowed, broken, aged, or otherwise have a reduced power
output, the strings may be re-connected in series to maintain a
minimum output voltage level. This may be beneficial, for example,
if the centralized inverter 88 requires a minimum input voltage to
maintain a high level of efficiency.
[0055] The smart switches S1-S5 may be triggered, for example, by
remote commands that are transmitted to the local communication
module 86 from centralized optimization logic.
[0056] FIG. 8 illustrates an example embodiment of a PV panel
having sub-strings that can be reconfigured for increasing the
efficiency of a PV array under non-ideal conditions according to
some inventive principles of this patent disclosure. The embodiment
of FIG. 8 includes a PV panel 92 having strings 94 of PV cells that
can be re-connected in any parallel/series combination through
switching matrix 96. A local power optimizer 98 includes a
communication module 100 to receive commands from centralized
control logic to enable the power optimizer to control the
switching matrix. In some embodiments, the switching matrix and
local power optimizer may be embedded directly inside the PV panel.
The PV panel illustrated in FIG. 8 may itself be connected to the
rest of a PV array in series or parallel, or it may be flexibly
reconnected with additional switches as shown in FIG. 7.
Additional Implementation Techniques
[0057] An additional implementation technique according to some
inventive principles of this patent disclosure involves the
correlation of the entire historical measurements of the array
(which may include all local MPPT device measurements, as well as
central inverter data measurements) to the granular solar
irradiation and temperature measurements available at on-site
weather stations. This may allow optimum operation of the entire PV
array at the currently measured weather conditions. In addition,
the correlation can take into consideration calendar-based time
frames such as day of the year, season, month, etc. Measuring
granular solar irradiation and temperature may act as a reference
for the calibration of each of the panels, as well as local MPPT
devices and a centralized inverter.
[0058] According to some additional inventive principles of this
patent disclosure, if an MPPT device's power train is designed to
be scalable, it may be possible to re-configure the MPPT device to
the specific brand, wattage, etc. of panels to be used at the
installation site through the communication capabilities built into
the system. Thus, the power-train may not need to be designed for a
specific wattage. Having an appropriately scaled power train may
allow optimum match of the MPPT device to the panel, thus providing
most optimum efficiency. Furthermore, cellular efficiency
enhancements such as phase dropping under reduced irradiation from
the rated conditions may be accomplished through the use of
pre-determined tables which may be loaded into the MPPT module, or
which may be served by the centralized server based on optimally
determined weather and time-of-year conditions.
[0059] Some additional implementation techniques according to the
inventive principles of this patent disclosure relate to the
reconfigurable power train architecture allowing on-site
configuration of the local power optimizer for optimum efficiency
by allowing matching to the specific solar panel being installed
through the communication capability, thus simplifying inventory
management as well as manufacturing logistics. If the local power
optimizer is embedded within the solar panel, this can be
accomplished by configuring the module during solar panel
integration.
[0060] Some additional implementation techniques according to the
inventive principles of this patent disclosure relate to the aging
of components. MPPT devices and/or a central inverter may undergo
drastic perturbations over multiple years of operation during which
their efficiency curves may change erratically and may
significantly vary from one module to another. In addition, they
may periodically see varied temperatures, increased panel mismatch,
increased module-to-module mismatch, etc. Correlating this
information to the irradiation data (including possibly
temperature, and time-of-year) may enable dynamic determination of
newer operating framework to be loaded into the MPPT modules or
served by the centralized server through the communication
capabilities.
[0061] Any of these additional inventive techniques may be applied
to systems that utilize micro-inverters to replace DC wiring with
AC wiring. These additional inventive techniques may also be
applied to module sub-string as well as individual cell levels of
abstraction.
[0062] As used herein, the term functionality includes some
structure. For example, in some embodiments, monitoring
functionality may be realized with an all-hardware implementation
that includes digital and/or analog hardware. In other embodiments,
the monitoring functionality may essentially be realized as a
software solution, but such an implementation still includes a
hardware platform on which the software runs.
[0063] The inventive principles of this patent disclosure have been
described above with reference to some specific example
embodiments, but these embodiments can be modified in arrangement
and detail without departing from the inventive concepts. Such
changes and modifications are considered to fall within the scope
of the following claims.
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