U.S. patent application number 13/346532 was filed with the patent office on 2012-05-03 for ac power systems for renewable electrical energy.
This patent application is currently assigned to AMPT, LLC. Invention is credited to Anatoli Ledenev, Robert M. Porter.
Application Number | 20120104864 13/346532 |
Document ID | / |
Family ID | 40567717 |
Filed Date | 2012-05-03 |
United States Patent
Application |
20120104864 |
Kind Code |
A1 |
Porter; Robert M. ; et
al. |
May 3, 2012 |
AC Power Systems for Renewable Electrical Energy
Abstract
A renewable electrical energy power system is provided with
aspects and circuitry that can optimize operation of a DC-AC
inverter. Alternative electrical energy sources may include solar
cells and solar panels. In various embodiments, the system may
include solar panel maximum power point independent inverter input
optimization photovoltaic power control circuitry, inverter
efficiency optimized converter control circuitry, inverter voltage
input set point converter output voltage control circuitry,
inverter sweet spot converter control circuitry, photovoltaic
inverter duty cycle switch control circuitry, substantially power
isomorphic photovoltaic inverter input control circuitry, and
substantially power isomorphic photovoltaic inverter duty cycle
control circuitry. With previously explained converters, inverter
control circuitry or photovoltaic power converter functionality
control circuitry configured as inverter sweet spot converter
control circuitry can achieve extraordinary efficiencies with
substantially power isomorphic photovoltaic capability at 99.2%
efficiency or even only wire transmission losses.
Inventors: |
Porter; Robert M.;
(Wellington, CO) ; Ledenev; Anatoli; (Fort
Collins, CO) |
Assignee: |
AMPT, LLC
Fort Collins
CO
|
Family ID: |
40567717 |
Appl. No.: |
13/346532 |
Filed: |
January 9, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12682882 |
Apr 13, 2010 |
8093756 |
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PCT/US2008/060345 |
Apr 15, 2008 |
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13346532 |
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PCT/US2008/057105 |
Mar 14, 2008 |
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12682882 |
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60980157 |
Oct 15, 2007 |
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60982053 |
Oct 23, 2007 |
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60986979 |
Nov 9, 2007 |
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60980157 |
Oct 15, 2007 |
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60982053 |
Oct 23, 2007 |
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60986979 |
Nov 9, 2007 |
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Current U.S.
Class: |
307/82 |
Current CPC
Class: |
Y02E 10/56 20130101;
Y04S 10/123 20130101; H02M 2001/0077 20130101; Y02P 80/20 20151101;
H02J 3/381 20130101; H02J 3/38 20130101; Y10S 136/293 20130101;
H02J 3/00 20130101; H02J 13/0003 20130101; H02J 3/385 20130101;
H02J 2300/26 20200101; Y02E 40/70 20130101 |
Class at
Publication: |
307/82 |
International
Class: |
H02J 3/00 20060101
H02J003/00 |
Claims
1. An inverter optimized renewable electrical energy power system
comprising: at least one alternative electrical energy source
having a DC photovoltaic output; at least one photovoltaic DC-DC
power converter responsive to said DC photovoltaic output and
having a photovoltaic DC converter output; a DC-AC inverter
responsive to said photovoltaic DC converter output; reactive
inverter input optimization photovoltaic power control circuitry;
and a photovoltaic AC power output responsive to said photovoltaic
DC-AC inverter.
2. An inverter optimized renewable electrical energy power system
as described in claim 1 wherein said reactive inverter input
optimization photovoltaic power control circuitry comprises solar
panel maximum power point independent inverter input optimization
photovoltaic power control circuitry.
3. An inverter optimized renewable electrical energy power system
as described in claim 1 wherein said reactive inverter input
optimization photovoltaic power control circuitry comprises
inverter efficiency optimized converter control circuitry.
4. An inverter optimized renewable electrical energy power system
as described in claim 1 wherein said reactive inverter input
optimization photovoltaic power control circuitry comprises
inverter voltage input set point converter output voltage control
circuitry.
5. An inverter optimized renewable electrical energy power system
as described in claim 4 wherein said inverter voltage input set
point converter output voltage control circuitry comprises inverter
sweet spot converter control circuitry.
6. An inverter optimized renewable electrical energy power system
as described in claim 5 wherein said inverter sweet spot converter
control circuitry comprises photovoltaic inverter duty cycle switch
control circuitry.
7. An inverter optimized renewable electrical energy power system
as described in claim 3 wherein said inverter efficiency optimized
converter control circuitry comprises substantially power
isomorphic photovoltaic inverter input control circuitry.
8. An inverter optimized renewable electrical energy power system
as described in claim 7 wherein said substantially power isomorphic
photovoltaic inverter input control circuitry comprises
substantially power isomorphic photovoltaic inverter duty cycle
control circuitry.
9. An inverter optimized renewable electrical energy power system
as described in claim 3 wherein said inverter efficiency optimized
converter control circuitry comprises inverter efficiency optimized
converter control circuitry selected from a group consisting of: at
least about 97% efficient photovoltaic conversion circuitry, at
least about 97.5% efficient photovoltaic conversion circuitry, at
least about 98% efficient photovoltaic conversion circuitry, at
least about 98.5% efficient photovoltaic conversion circuitry, at
least about 97% up to about 99.2% efficient photovoltaic conversion
circuitry, at least about 97.5% up to about 99.2% efficient
photovoltaic conversion circuitry, at least about 98% up to about
99.2% efficient photovoltaic conversion circuitry, at least about
98.5% up to about 99.2% efficient photovoltaic conversion
circuitry, at least about 97% up to about wire transmission loss
efficient photovoltaic conversion circuitry, at least about 97.5%
up to about wire transmission loss efficient photovoltaic
conversion circuitry, at least about 98% up to about wire
transmission loss efficient photovoltaic conversion circuitry, and
at least about 98.5% up to about wire transmission loss efficient
photovoltaic conversion circuitry.
10. An inverter optimized renewable electrical energy power system
as described in claim 1 wherein said at least one alternative
electrical energy source comprises at least one solar cell.
11. An inverter optimized renewable electrical energy power system
as described in claim 1 wherein said at least one alternative
electrical energy source comprises a plurality of electrically
connected solar panels.
12. An inverter optimized renewable electrical energy power system
as described in claim 1 wherein said photovoltaic DC-DC power
converter comprises at least one multimodal photovoltaic DC-DC
power converter and further comprises multimodal converter
functionality control circuitry.
13. An inverter optimized renewable electrical energy power system
as described in claim 1 and furthering comprising dynamically
reactive internal output limited photovoltaic power control
circuitry.
14. An inverter optimized renewable electrical energy power system
as described in claim 1 and further comprising inverter sourced
photovoltaic power conversion output control circuitry.
15. An inverter optimized renewable electrical energy power system
as described in claim 1 further comprising inverter coordinated
photovoltaic power conversion control circuitry.
16. An inverter optimized renewable electrical energy power system
as described in claim 1 and further comprising a solar power
conversion comparator that indicates a solar energy parameter of a
first power capability as compared to a second power
capability.
17. An inverter optimized renewable electrical energy power system
as described in claim 1 and further comprising soft transition
photovoltaic power conversion control circuitry.
18. An inverter optimized renewable electrical energy power system
as described in claim 1 wherein said reactive inverter input
optimization photovoltaic power control circuitry comprises
photovoltaic inverter duty cycle switch control circuitry.
19. An inverter optimized renewable electrical energy power system
as described in claim 1 and further comprising an AC power grid
interface to which said AC power output supplies power.
20. An inverter optimized renewable electrical energy power system
as described in claim 1 wherein said DC-AC inverter comprises a
high voltage DC-AC solar power inverter.
21. An inverter optimized renewable electrical energy power system
as described in claim 20 wherein said photovoltaic AC power output
comprises a three phase photovoltaic AC power output.
Description
[0001] This application is a continuation of, and claims benefit of
and priority to, U.S. patent application Ser. No. 12/682,882, filed
Apr. 13, 2010, which is the National Stage of International Patent
Application No. PCT/US2008/060345, filed Apr. 15, 2008, which
claims priority to and the benefit of U.S. Provisional Application
No. 60/980,157, filed Oct. 15, 2007, and claims priority to and the
benefit of U.S. Provisional Application No. 60/982,053, filed Oct.
23, 2007, and claims priority to and the benefit of U.S.
Provisional Application No. 60/986,979, filed Nov. 9, 2007, and is
a continuation of, and claims benefit of and priority to,
International Patent Application No. PCT/US2008/057105, filed Mar.
14, 2008, which claims priority to and the benefit of U.S.
Provisional Application No. 60/980,157, filed Oct. 15, 2007, and
claims priority to and the benefit of U.S. Provisional Application
No. 60/982,053, filed Oct. 23, 2007, and claims priority to and the
benefit of U.S. Provisional Application No. 60/986,979, filed Nov.
9, 2007, each said application hereby incorporated herein by
reference in its entirety.
TECHNICAL FIELD
[0002] This invention relates to the technical field of alternative
energy, specifically, methods and apparatus for creating electrical
power from some type of alternative energy source to make it
available for use in a variety of applications. Through perhaps
four different aspects, the invention provides techniques and
circuitry that can be used to harvest power at high efficiency from
an alternative energy source such as a solar panel, or a sea of
strings of panels so that this power can be provided for AC use,
perhaps for transfer to a power grid or the like. These four
aspects can exist perhaps independently and relate to: 1)
controlling electrical power creation with an inverter, 2)
operating an inverter at its maximal efficiency even when a solar
panel's maximum power point would not be at that level, 3)
protecting an inverter, and even 4) providing a system that can
react and assure operation for differing components and perhaps
even within code limitations or the like.
BACKGROUND
[0003] Renewable electrical energy that is electrical energy
created from alternative sources such as those that are
environmentally compatible and perhaps sourced from easily
undisruptively available sources such as solar, wind, geothermal or
the like is highly desirable. Considering, but not limiting, the
example of solar power this is almost obvious. For years, solar
power has been touted as one of the most promising for our
increasingly industrialized society. Even though the amount of
solar power theoretically available far exceeds most, if not all,
other energy sources (alternative or not), there remain practical
challenges to utilizing this energy. In general, solar power
remains subject to a number of limitations that have kept it from
fulfilling the promise it holds. In one regard, it has been a
challenge to implement in a manner that provides adequate
electrical output as compared to its cost. The present invention
addresses an important aspect of this in a manner that
significantly increases the ability to cost-effectively permit
solar power to be electrically harnessed so that an AC output may
be a cost-effective source of electrical power whether it be
provided for internal use or for public comsumption, such as
feedback to a grid or the like.
[0004] Focusing on solar power as it may be applied in embodiments
of the invention, one of the most efficient ways to convert solar
power into electrical energy is through the use of solar cells.
These devices create a photovoltaic DC current through the
photovoltaic effect. Often these solar cells are linked together
electrically to make a combination of cells into a solar panel or a
PV (photovoltaic) panel. PV panels are often connected in series to
provide high voltage at a reasonable current. Voltage, current, and
power levels may be provided at an individual domestic level, such
as for an individual house or the like. Similarly, large arrays of
many, many panels may be combined in a sea of panels to create
significant, perhaps megawatt outputs to public benefit perhaps as
an alternative to creating a new coal burning power plant, a new
nuclear power plant, or the like.
[0005] Regardless of the nature of the combination, the output
(perhaps of a solar cell or a solar panel, or even combinations
thereof) is then converted to make the electrical power most usable
since the power converters often employed can use high voltage
input more effectively. This converted output is then often
inverted to provide an AC output as generally exists in more
dispersed power systems whether at an individual domestic or even a
public level. In a first stage in some systems, namely, conversion
of the alternative source's input to a converted DC, conventional
power converters sometimes even have at their input handled by an
MPPT (maximum power point tracking) circuit to extract the maximum
amount of power from one or more or even a string of series
connected panels. One problem that arises with this approach,
though, is that often the PV panels act as current sources and when
combined in a series string, the lowest power panel can limit the
current through every other panel. In a second stage in some
systems, namely the inversion function to transform the DC into AC,
another problem can be that operation of the conversion at maximum
power point (MPP) can be somewhat incompatible with or at least
suboptimal for an inverter. Prior to the present invention, it was
widely seen that it was just an inherent characteristic that needed
to be accepted and that the MPP conversion function was so
electrically critical that it was generally accepted as a control
requirement that made suboptimization at the inverter level merely
a necessary attribute that was perhaps inherent in any
converted-inverted system. Perhaps surprisingly, prior to this
invention, the goal of optimizing both the MPP conversion function
while also optimizing the inversion function was just not seen as
an achievable or perhaps at least significant goal. The present
invention proves that both such goals can not only be achieved, but
the result can be an extraordinarily efficient system.
[0006] In understanding (and perhaps defending) the perceived
paramount nature of an MPP operation, it may be helpful to
understand that, in general, solar cells historically have been
made from semiconductors such as silicon pn junctions. These
junctions or diodes convert sunlight into electrical power. These
diodes can have a characteristically low voltage output, often on
the order of 0.6 volts. Such cells may behave like current sources
in parallel with a forward diode. The output current from such a
cell may be a function of many construction factors and, is often
directly proportional to the amount of sunlight. The low voltage of
such a solar cell can be difficult to convert to power suitable for
supplying power to an electric power grid. Often, many diodes are
connected in series on a photovoltaic panel. For example, a
possible configuration could have 36 diodes or panels connected in
series to make 21.6 volts. With the shunt diode and interconnect
losses in practice such panels might only generate 15 volts at
their maximum power point (MPP). For some larger systems having
many such panels, even 15 volts may be too low to deliver over a
wire without substantial losses. In addition, typical systems today
may combine many panels in series to provide voltages in the 100's
of volts in order to minimize the conduction loss between the PV
panels and a power converter. Electrically, however, there can be
challenges to finding the right input impedance for a converter to
extract the maximum power from such a string of PV panels.
Naturally, the input usually influences the output. Input variances
can be magnified because, the PV panels usually act as current
sources and the panel producing the lowest current can sometimes
limit the current through the whole string. In some undesirable
situations, weak panels can become back biased by the remainder of
the panels. Although reverse diodes can be placed across each panel
to limit the power loss in this case and to protect the panel from
reverse breakdown, there still can be significant variances in the
converted output and thus the inverted input. In solar panel
systems, problems can arise due to: non-uniformity between panels,
partial shade of individual panels, dirt or accumulated matter
blocking sunlight on a panel, damage to a panel, and even
non-uniform degradation of panels over time to name at least some
aspects. These can all be considered as contributing to the
perception that a varying inverted input was at least practically
inevitable. Just the fact that a series connection is often desired
to get high enough voltage to efficiently transmit power through a
local distribution to a load, perhaps such as a grid-tied inverter
has further compounded the aspect. In real world applications,
there is also frequently a desire or need to use unlike types of
panels without regard to the connection configuration desired
(series or parallel, etc.). All of this can be viewed as
contributing to the expectation of inevitability relative to the
fact that the inverter input could not be managed for optimum
efficiency.
[0007] In in previous stat-of-the-art system, acceptable efficiency
has been at relatively lower levels (at least as compared to the
present invention). For example, in the article by G. R. Walker, J.
Xue and P. Sernia entitled "PV String Per-Module Maximum Power
Point Enabling Converters" those authors may have even suggested
that efficiency losses were inevitable. Lower levels of efficiency,
such as achieved through their `enhanced` circuitries, were touted
as acceptable. Similarly, two of the same authors, G. R. Walker and
P. Sernia in the article entitled "Cascaded DC-DC Converter
Connection of Photovoltaic Modules" suggested that the needed
technologies would always be at an efficiency disadvantage. These
references even include an efficiency vs. power graph showing a
full power efficiency of approximately 91%. With the high cost of
PV panels operation through such a low efficiency converter it is
no wonder that solar power has been seen as not yet readily
acceptable for the marketplace. The present invention shows that
this need not be true, and that much higher levels of efficiency
are in fact achievable.
[0008] Another less understood problem with large series strings of
PV panels may be with highly varying output voltage, the inverter
stage driving the grid my need to operate over a very wide range
also lowering its efficiency. It may also be a problem if during
periods of time when the inverter section is not powering the grid
that the input voltage to this stage may increase above regulatory
limits. Or conversely, if the voltage during this time is not over
a regulatory limit then the final operational voltage may be much
lower than the ideal point of efficiency for the inverter. In
addition, there may be start-up and protection issues which add
significant cost to the overall power conversion process. Other
less obvious issues affecting Balance of System (BOS) costs for a
solar power installation are also involved. Thus, what at least one
aspect of electrical solar power needs is an improvement in
efficiency in the conversion stage of the electrical system. The
present invention provides this needed improvement.
DISCLOSURE OF THE INVENTION
[0009] As mentioned with respect to the field of invention, the
invention includes a variety of aspects, which may be combined in
different ways. The following descriptions are provided to list
elements and describe some of the embodiments of the present
invention. These elements are listed with initial embodiments,
however it should be understood that they may be combined in any
manner and in any number to create additional embodiments. The
variously described examples and preferred embodiments should not
be construed to limit the present invention to only the explicitly
described systems, techniques, and applications. Further, this
description should be understood to support and encompass
descriptions and claims of all the various embodiments, systems,
techniques, methods, devices, and applications with any number of
the disclosed elements, with each element alone, and also with any
and all various permutations and combinations of all elements in
this or any subsequent application.
[0010] In various embodiments, the present invention discloses
achievements, systems, and different initial exemplary control
functionalities through which one may achieve some of the goals of
the present invention. Systems provide for inverter controlled
systems of photovoltaic conversion, high efficiency renewable
energy creation, inverter protection designs, and even dynamically
reactive conversion systems.
[0011] Some architectures may combine a PV panel with MPP and even
a dual mode power conversion circuitry to make what may be referred
to as a Power Conditioner (PC) element. Converters may have a
topology such as the initial examples shown in FIGS. 10A and 10B;
these are discussed in more detail in the priority applications. As
discussed below, the Power Conditioners may be combined in series
or parallel or any combination of series/parallel strings and even
seas of panels that largely or even always produce their full
output. Even differing types of panels, differing types of
converters, and differing types of inverters may be combined.
[0012] In embodiments, this invention may permit in inverter to
produce its maximum power thereby harvesting more total energy from
the overall system. Interestingly, this may exist even while a
converter alters its acceptance of alternative power to maintain an
MPP. Embodiments may be configured so that the output may be a
higher voltage AC output (for example, 400V or more). Additionally,
configurations may allow for an easy to administer inverter
protection, perhaps even with or without feedback elements.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 shows a block diagram of a conversion system
according to one embodiment of the invention for a single
representative solar source.
[0014] FIG. 2 shows a schematic of a sea of interconnected strings
of panels according to one embodiment of the invention.
[0015] FIG. 3 shows a plot of a current and voltage relationship
for a representative solar panel.
[0016] FIG. 4 shows a plot of a power and voltage relationship for
a similar panel.
[0017] FIG. 5 shows an embodiment of the invention with series
connected panels and a single grid-tied inverter configuration.
[0018] FIGS. 6A and 6B show plots of solar panel output operational
conditions for differing temperatures and output paradigms.
[0019] FIG. 7 shows a plot of converter losses by topology and
range for a traditional approach considered for a converter element
as may be used in embodiments of the present invention.
[0020] FIG. 8 shows a plot of combined sweet spot, protective, and
coordinated process conditions according to one operational
embodiment of the invention.
[0021] FIG. 9 shows a prior art system with a grid-tied
inverter.
[0022] FIGS. 10A and 10B show two types of dual mode power
conversion circuits such as might be used in embodiments of the
invention.
MODE(S) FOR CARRYING OUT THE INVENTION
[0023] As mentioned above, the invention discloses a variety of
aspects that may be considered independently or in combination with
others. Initial understanding begins with the fact that one
embodiment of a renewable electrical energy AC power system
according to the present invention may combine any of the following
concepts and circuits including: an inverter controlled system to
at least some extent, a maximal efficiency inverter operational
capability, a protected inverter alternative AC energy system, a
dynamically reactive photovoltaic system, and an engineered code
compliant alternative energy system. Aspects may include a very
high efficiency photovoltaic converter, a multimodal photovoltaic
converter, slaved systems, and even output voltage and/or output
current protected system. Each of these should be understood from a
general sense as well as through embodiments that display initial
applications for implementation. Some initial benefits of each of
these aspects are discussed individually and in combination in the
following discussion as well as how each represents a class of
topologies, rather than just those initially disclosed.
[0024] FIG. 1 shows one embodiment of a renewable electrical energy
power system illustrating the basic conversion and inversion
principles of the present invention. As shown, it involves an
alternative electrical energy source (1) (here indicated by
nomenclature as a solar energy source) feeding into a photovoltaic
DC-DC power converter (4) providing a converted output to a DC-AC
inverter (5) that may perhaps ultimately interface with a grid
(10). As may be appreciated, the alternative electrical energy
source (1) may be a solar cell, a solar panel, or perhaps even a
string of panels. Regardless, the alternative electrical energy
source (1) may create an output such as a DC photovoltaic output
(2). This DC photovoltaic output (2) may be established as a DC
photovoltaic input (3) to the DC-DC power converter (4). Similarly,
the DC-DC power converter (4) may create an output such as a DC
photovoltaic output (6). This DC photovoltaic output (6), or more
generally photovoltaic DC converter output, may be established as
an inverter input (29) to the DC-AC inverter (5). Ultimately, the
DC-AC inverter (5) may act to invert the converted DC and create an
AC output such as a photovoltaic AC power output (30) which may be
be established an an input to a grid (10), a domestic electrical
system, or both, or some other power consuming device or thing.
[0025] The DC-DC power converter (4) may have its operation
controlled by a capability generally indicated as converter
functionality control circuitry (8). As one of ordinary skill in
the art should well appreciate, this converter functionality
control circuitry (8) may be embodied as true circuitry hardware or
it may be firmware or even software to accomplish the desired
control and would still fall within the meaning of a converter
functionality control circuitry (8). Similarly, the DC-DC power
converter (4) should be considered to represent photovoltaic DC-DC
power conversion circuitry. In this regard it is likely that
hardware circuitry is necessary, however combinations of hardware,
firmware, and software should still be understood as encompassed by
the circuitry term.
[0026] The DC-AC inverter (5) may also have its operation
controlled by inverter control circuitry (38) that likewise may be
embodied as true circuitry hardware or it may be firmware or even
software to accomplish the desired control and would still fall
within the meaning of an inverter controlling step or an inverter
control circuitry (38).
[0027] As illustrated in FIG. 1, the various elements may be
connected to each other. Direct connection is but one manner in
which the various elements may be responsive to each other, that
is, some effect in one may directly or indirectly cause an effect
or change in another. For example, while there could be a
connection between the inverter control circuitry (38) and the
converter functionality control circuitry (8), effects can occur
and responsiveness can exist even without the connection. In fact,
in a preferred embodiment, no such direct connection is used as the
effect can be cause even without such a connection.
[0028] Sequencing through the schematic diagram, it can be
understood that the DC-DC power converter (4) may act to convert
its input and thus provide a converted DC photovoltaic output (6)
which may serve as an input to the DC-AC inverter (5) which may be
of a variety of designs. This DC-AC inverter (5) may serve as one
way to accomplish the step of inverting the DC power into an
inverted AC (7) such as a photovoltaic AC power output (7) that can
be used by, for example, a power grid (10) through some connection
termed an AC power grid interface (9). In this manner the system
may create a DC photovoltaic output (6) which may be established as
an input to some type of DC-AC inverter (5). This step of inverting
an input should be understood as encompassing and creation of any
substantially alternating signal from any substantially
unidirectional current flow signal even if that signal is not
itself perfectly, or even substantially, steady.
[0029] As shown in FIGS. 2 and 5, individual alternative electrical
energy sources (1) (here shown as solar energy sources--whether at
a cell, panel, or module level) may be combined to create a series
of electrically connected sources. Such combinations may be
responsive through either series or parallel connections. As shown
in FIGS. 2 and 5, the connected plurality may form a string of
electrically connected items, perhaps such as a string of
electrically connected solar panels (11). As shown in FIG. 2, each
of these strings may themselves be a component to a much larger
combination perhaps forming a photovoltaic array (12) or even a sea
of combined solar energy sources. By either physical or electrical
layout, certain of these cells, panels, or strings may be adjacent
in that they may be exposed to somewhat similar electrical,
mechanical, environmental, solar exposure (or insolative)
conditions. In situations where large arrays or seas are provided,
it may be desirable to include a high voltage DC-AC solar power
inverter perhaps with a three phase high voltage inverted AC
photovoltaic output as schematically illustrated in FIG. 2.
[0030] As illustrated for an electrically serial combination,
output may be combined so that their voltages may add whereas their
currents may be identical. Conversely, electrically parallel
combinations may exist. FIGS. 2 and 5 illustrate embodiments that
are connected to accomplish serially combining or serially
connecting items such as the converted DC photovoltaic outputs (6)
to create a converted DC photovoltaic input to a DC-AC inverter
(5). As shown, these serial connections may be of the converted DC
photovoltaic outputs (6) which may then create a converted DC
photovoltaic output (13) which may serve as a converted DC
photovoltaic input (14) to some type of photovoltaic DC-AC inverter
(5) or other load. Again, each alternative electrical energy source
(1) may be a solar source such as at the cell, panel, string, or
even array level. As would be well understood, parallel connections
and the step of parallel connecting converters or their outputs
could be accomplished as well.
[0031] As mentioned above, circuitry and systems can be configured
to extract as much power as possible from an alternative electrical
energy source (1); this is especially applicable for a solar power
source or sources where insolation can be variable from source to
even adjacent source. Electrically, this may be accomplished by
achieving operation to operate at one or more solar cell, panel, or
string's maximum power point (MPP) by MPP circuitry or maximum
power point tracking (MPPT). Thus, in embodiments, a solar power
system according to the invention may include an MPPT control
circuit with a power conversion circuit. It may even include range
limiting circuitry as discussed later.
[0032] This aspect of maximum power point is illustrated by
reference to FIGS. 3 and 4 and the Maximum Power Point Tracking
(MPPT) circuit may be configured to find the optimum point for
extracting power from a given panel or other alternative electrical
energy source (1). As background, it should be understood that a
panel such as may be measured in a laboratory may exhibit the
voltage and current relationships indicated in FIG. 3. Current in
Amps is on the vertical axis. Voltage in volts is on the horizontal
axis. If one multiplies the voltage times the current to derive
power this is shown in FIG. 4. Power is now on the vertical axis.
The goal of an embodiment of an MPPT circuit as used here may be to
apply an appropriate condition to a panel such that the panel may
operate to provide its peak power. One can see graphically that the
maximum power point on this panel under the measurement conditions
occurs when the panel produces approximately 15 volts and 8
amperes. This may be determined by a maximum photovoltaic power
point converter functionality control circuitry (15) which may even
be part or all of the modality of operation of the converter
functionality control circuitry (8). In this fashion, the converter
or the step of converting may provide a maximum photovoltaic power
point modality of photovoltaic DC-DC power conversion or the step
of maximum photovoltaic power point converting. This may be
accomplished by switching and perhaps also by duty cycle switching
at the converter or even inverter level and as such the system may
accomplish maximum photovoltaic power point duty cycle switching or
the step of maximum photovoltaic voltage determinatively duty cycle
switching.
[0033] As one skilled in the art would appreciate, there are
numerous circuit configurations that may be employed to derive MPP
information. Some may be based on observing short circuit current
or open circuit voltage. Another class of solutions may be referred
to as a Perturb and Observe (P&O) circuit. The P&O methods
may be used in conjunction with a technique referred to as a "hill
climb" to derive the MPP. As explained below, this MPP can be
determined individually for each source, for adjacent sources, of
for entire strings to achieve best operation. Thus a combined
system embodiment may utilize individually panel (understood to
include any source level) dedicated maximum photovoltaic power
point converter functionality control circuitries (16).
[0034] Regardless of whether individually configured or not, in one
P&O method, an analog circuit could be configured to take
advantage of existing ripple voltage on the panel. Using simple
analog circuitry it may be possible to derive panel voltage and its
first derivative (V'), as well as panel power and its first
derivative (P'). Using the two derivatives and simple logic it may
be possible to adjust the load on the panel as follows:
TABLE-US-00001 TABLE 1 V' Positive P' Positive Raise Panel Voltage
V' Positive P' Negative Lower Panel Voltage V' Negative P' Positive
Lower Panel Voltage V' Negative P' Negative Raise Panel Voltage
[0035] There may be numerous other circuit configurations for
finding derivatives and logic for the output, of course. In
general, a power conditioner (17) may include power calculation
circuitry, firmware, or software (21) which may even be
photovoltaic multiplicative resultant circuitry (22). These
circuitries may act to effect a result or respond to an item which
is analogous to (even if not the precise mathematical resultant of
a V*I multiplication function) a power indication. This may of
course be a V*I type of calculation of some power parameters and
the system may react to either raise or lower itself in some way to
ultimately move closer to and eventually achieve operation at an
MPP level. By provided a capability and achieving the step of
calculating a photovoltaic multiplicative power parameter, the
system can respond to that parameter for the desired result.
[0036] In many traditional systems, such an MPP operation is often
performed at a macro level, that is for entire strings or the
entire alternative electrical energy source network. As explained
herein, his is one aspect that can contribute to less than optimal
efficiency. Often many traditional systems derive MPP at a front
end or by some control of the DC-AC inverter (5). Thus, by altering
the inverter's power acceptance characteristics, an alteration of
the current drawn or other parameter, and thus the total power
created, can be altered to pull the maximum from the alternative
electrical energy sources (1). Whether at the front of the inverter
or not, of course, such an alteration would vary the input to the
DC-AC inverter (5) and for this reason as well as the fact that
insolation varies, it had come to be expected that inverters would
always necessarily experience a variation in input and thus the
more important goal of operation at an MPP level would not permit
operation at the best efficiency input level for the inverter. The
present invention shows that this is not true.
[0037] FIG. 9 illustrates one type of photovoltaic DC-AC inverter
(5) that may be used. Naturally as may be appreciated from the
earlier comments enhanced inverters that need not control MPP may
be used. In one aspect of the invention, the inverter may have its
input controlled at an optimal level. For example, a separate
control input could be used so that the input voltage is at a most
optimal level, perhaps such as a singular sweet spot or the like as
illustrated by the bold vertical line in FIG. 8. Interestingly and
as explained in more detail below, this may be accomplished by the
present invention in a manner that is independent of the MPP level
at which the converter operates. Finally, as shown, the inverter
may be connected to some type of AC power grid interface (9).
[0038] Another aspect of the invention is the possibility of the
inverter controlling the output of the converter. Traditionally,
the inverter has been viewed as a passive recipient of whatever the
converter needs to output. In sharp contrast, embodiments of the
present invention may involve having the DC-AC inverter (5) control
the output of the DC-DC converter (4). As mentioned in more detail
below, this may be accomplished by duty cycle switching the DC-AC
inverter (5) perhaps through operation of the inverter control
circuitry (38). This duty cycle switching can act to cause the
output of the DC-DC converter (4) (which itself may have its own
operation duty cycle switched to achieve MPP operation) to alter by
load or otherwise so that it is at precisely the level the DC-AC
inverter (5) wants. As mentioned above, this may be achieved by a
direct control input or, for preferred embodiments of the invention
may be achieved by simply alter an effect until the converter's DC
photovoltaic output (6) and thus the inverter input (29) are as
desired. This can be considered as one manner of photovoltaic
inverter sourced converting within such a system. With this as but
one example of operation, it should be understood that, in general,
a control may be considered inverter sourced or derived from
conditions or functions or circuitry associated with the DC-AC
inverter (5) and thus embodiments of the invention may include
inverter sourced photovoltaic power conversion output control
circuitry within or associated with the inverter control circuitry
(38).
[0039] In embodiments, an important aspect of the above control
paradigm can be the operation of the inverter to control its own
input at an optimal level. For example, it is known that inverter
often have a level of voltage input at which the inverter achieves
its inverting most efficiently. This is often referred to as the
inverter input sweet spot and it is often associated with a
specific voltage level for a specific inverter. By providing the
action of photovoltaic inverter sourced controlling operation,
embodiments may even provide a set point or perhaps substantially
constant voltage output as the inverter input (29) and thus
embodiments may have a substantially constant power conversion
voltage output or may also achieve the step of substantially
constant voltage output controlling of the operation of the system.
An inverter voltage input set point may be so established, and
embodiments may include inverter voltage input set point converter
output voltage control circuitry to manage the step of inverter
voltage input set point controlling of the operation of the
system.
[0040] As mentioned above, a surprising aspect of embodiments of
the invention may be the fact that inverter input may be maintained
independent of and even without regard to a separately maintained
MPP level of operation. Thus, inverter optimum input can exist
while simultaneously maintaining MPP level of conversion
functionality. As but one example, embodiments can include
independent inverter operating condition converter output control
circuitry or the step of independently controlling an inverter
operating condition perhaps through the photovoltaic DC-DC
converter or the photovoltaic DC-DC power converter (4). As
mentioned aboe in embodiments, this can be achieved through duty
cycle switching of both the photovoltaic DC-DC power converter (4)
and the DC-AC inverter (5). In this manner, embodiments may include
the step of maximum power point independently controlling the
inverter input voltage. For solar panels, systems may have solar
panel maximum power point independent inverter input voltage
control circuitry (38). This circuitry may be configured for an
optimal level and thus embodiment may have solar panel maximum
power point independent inverter input optimization photovoltaic
power control circuitry. Generally there may be a solar panel
maximum power point independent power conversion output or even the
step of solar panel maximum power point independently controlling
of the operation of the system.
[0041] An aspect of operational capability that afford advantage is
the capability of embodiments of the invention to accommodate
differing operating conditions for various solar sources or panels.
As shown in FIGS. 6A and 6B, voltages of operation for maximum
power point can vary based upon not just changes in insolation but
also whether the solar source is experiencing hot or cold
temperature conditions. By permitting MPP to be accommodated
through control apart from any voltage constraint, embodiments
according to the invention may provide expansive panel capability.
This may even be such that the converter is effectively a full
photovoltaic temperature voltage operating range photovoltaic DC-DC
power converter whereby it can operate at MPP voltages as high as
that for the MPP in a cold temperature of operation as well as the
MPP voltages as low as that for the MPP in a hot temperature of
operation. Thus, as can be understood from FIGS. 6A and 6B, systems
can provide solar energy source open circuit cold voltage
determinative switching photovoltaic power conversion control
circuitry and solar energy source maximum power point hot voltage
determinative switching photovoltaic power conversion control
circuitry. It can even achieve full photovoltaic temperature
voltage operating range converting. This may be accomplished
through proper operation of the switch duty cycles and systems may
thus provide solar energy source open circuit cold voltage
determinatively duty cycle switching and solar energy source
maximum power point hot voltage determinatively duty cycle
switching.
[0042] Further, viewing hot and cold voltages as perhaps the
extreme conditions, similarly it can be understood how the system
may accommodate varying amount of insolation and thus there may be
provided insolation variable adaptive photovoltaic converter
control circuitry that can extract MPP--even while maintaining an
optimal inverter input--whether a panel is partially shaded, even
if relative to an adjacent panel. Systems and their duty cycle
switching may be adaptable to the amount of insolation and so the
step of converting may be accomplished as insolation variably
adaptively converting. This can be significant in newer technology
panels such as cadmium-telluride solar panels and especially when
combining outputs from a string of cadmium-telluride solar panels
which can have broader operating voltages.
[0043] Of significant importance is the level of efficiency with
which the entire system operates. This is defined as the power
going out over the power coming in. A portion of the efficiency
gain is achieved by using switching operation of transistor
switches, however, the topology is far more significant in this
regard. Specifically, by the operation of switches and the like as
discussed above, the system can go far beyond the levels of
efficiency previously thought possible. It can even provide a
substantially power isomorphic photovoltaic DC-DC power conversion
and substantially power isomorphic photovoltaic DC-AC power
inversion that does not substantially change the form of power into
heat rather than electrical energy by providing as high as about
99.2% efficiency. This can be provided by utilizing substantially
power isomorphic photovoltaic converter and inverter functionality
and a substantially power isomorphic photovoltaic converter and
inverter and by controlling operation of the switches so that there
is limited loss as discussed above. Such operation can be at levels
of from 97, 97.5, 98, 98.5 up to either 99.2 or essentially the
wire transmission loss efficiency (which can be considered the
highest possible).
[0044] The combined abilities to operate the inverter at its most
efficient, sweet spot while simultaneously operating the panels at
their MPP aids in these efficiency advantages. While in prior art
efficiency was sometimes shown to be less than 91%, this
combination can accomplish the needed function while operating even
above 98% and at levels as high as only those experiencing wire
transmission losses. Efficiencies of about 99.2% can be achieved.
When connected to a solar panel or an array of solar panels this
efficiency difference can be of paramount importance. Embodiments
having a constant voltage input to the inverter can thus be
considered as having substantially power isomorphic photovoltaic
inverter input control circuitry. When embodiments accomplish this
through duty cycle switching for the inverter, such embodiments can
be considered as having substantially power isomorphic photovoltaic
inverter duty cycle control circuitry or as providing the step of
substantially power isomorphically duty cycle switching the
photovoltaic DC-AC inverter. The ability to set a constant input
regardless of MPP needs allows the inverter controller to optimize
the input for the inverter and so serve as inverter efficiency
optimized converter control circuitry or provide the step of
inverter efficiency optimization controlling of the operation of
the system. Of course in embodiments where optimization is
determined by operating at the point of maximum efficiency, or the
sweet spot, the system can be understood as including inverter
sweet spot control circuitry or even as inverter sweet spot
converter control circuitry (46) when this is accomplished through
the converter's output. Generally, it can also be considered as
providing the step of inverter sweet spot controlling of the
operation of the system. The inverter sweet spot operation
capability can also be slaved to other functions (as discussed
later) and thus the inverter sweet spot control circuitry can be
slaved inverter sweet spot control circuitry or as providing the
step of slavedly controlling sweet spot operation of the
photovoltaic DC-AC inverter.
[0045] Considering the converter (as discussed in more detail in
the priority applications), one aspect that contributes to such
efficiency is the fact that minimal change of stored energy during
the conversion process. As shown in FIG. 6, such embodiments may
include a parallel capacitance and a series inductance. These may
be used to store energy at least some times in the operation of
converting. It may even be considered that full energy conversion
is not accomplished, only the amount of conversion necessary to
achieve the desired result.
[0046] Also contributing to the overall system efficiency advantage
in some embodiments can be the use of electrically connecting
panels in a series string so the current through each power
conditioner (PC) (17) output may be the same but the output voltage
of each PC may be proportional to the amount of power its panel
makes together with an MPP per panel capability. Consider the
following examples to further disclose the functioning of such
series connected embodiments. Examine the circuit of FIG. 5 and
compare it to panels simply connected in series (keep in mind that
the simple series connection may have a reverse diode across it).
First, assume there are four panels in series each producing 100
volts and 1 amp feeding an inverter with its input set to 400
volts. This gives 400 watts output using either approach. Now
consider the result of one panel making 100 volts and 0.8 amps
(simulating partial shading--less light simply means less current).
For the series connection the 0.8 amps flows through each panel
making the total power 400.times.0.8=320 watts. Now consider the
circuit of FIG. 6. First, the total power would be 380 watts as
each panel is making its own MPP. And of course the current from
each Power Conditioner must be the same as they are after all still
connected in series. But with known power from each PC the voltage
may be calculated as:
3V+0.8V=400 volts, where V is the voltage on each full power
panel.
[0047] Thus, it can be seen that in this embodiment, three of the
panels may have 105.3 volts and one may have 84.2 volts.
[0048] Further, in FIG. 5 it can be understood that in some
embodiments, an additional benefit may be derived from the
inclusion of individual MPP per panel power control. In such
embodiments, a power block may be considered as a group of PV
panels with power conversion and MPP per panel configurations. As
such they may adapt their output as needed to always maintain
maximum power from each and every power block.
[0049] The advantage of this type of a configuration is illustrated
from a second example of MPP operation. This example is one to
illustrate where one panel is shaded such that it can now only
produce 0.5 amps. For the series connected string, the three panels
producing 1 amp may completely reverse bias the panel making 0.5
amps causing the reverse diode to conduct. There may even be only
power coming from three of the panels and this may total 300 watts.
Again for an embodiment circuit of invention, each PC may be
producing MPP totaling 350 watts. The voltage calculation would
this time be:
3V+0.5V=400 volts
[0050] This, in this instance, the three panels may have a voltage
of 114.2 volts and the remaining one may have half as much, or 57.1
volts. These are basic examples to illustrate some advantages. In
an actual PV string today there may be many PV panels in series.
And usually none of them make exactly the same power. Thus, many
panels may become back biased and most may even produce less than
their individual MPP. As discussed below, such configurations can
also be configured to include voltage limits and/or protection
perhaps by setting operational boundaries. Importantly, however,
output voltage can be seen as proportional to PV panel output power
thus yielding a better result to be available to the DC-AC inverter
(5) for use in its inversion. Now, when the DC-AC inverter (5) is
also able to be operated at its sweet spot, it can efficiently
invert the individualized MPP energy pulled from the sea of panels
or the like for the overall system efficiency gains mentioned.
[0051] An interesting, and perhaps even surprising aspect of the
invention is that the DC-AC inverter (5) can be coordinated with
the photovoltaic DC-DC converter (4). Embodiments can have inverter
coordinated photovoltaic power conversion control circuitry (45) or
can provide the step of inverter coordinated converting or inverter
coordinated controlling of the operations. As mentioned this can be
direct or indirect. As shown in FIG. 1, there could be a direct
connection from the inverter control circuitry (38) to the
converter functionality control circuitry (8), however, in
preferred embodiments, no such direct connection may be needed.
Specifically, and for only one example, by simply controlling its
duty cycle to maintain a sweet spot input, the DC-AC inverter (5)
can cause the photovoltaic DC-DC converter (4) to alter its
operation as it simply tries to maintain its duty cycle to maintain
MPP. This indirect control is still considered as providing
photovoltaic converter output control circuitry, and even more
specifically, as providing photovoltaic converter output voltage
control circuitry (32) because it causes the step of controlling a
photovoltaic DC-DC converter output (also referred to as the DC
photovoltaic output (2)) of the photovoltaic DC-DC converter (4),
and even more specifically, as providing the step of controlling a
photovoltaic DC-DC converter voltage output of the photovoltaic
DC-DC converter (4).
[0052] While in theory or in normal operation the described
circuits work fine, there can be additional requirements for a
system to have practical function. For example the dual mode
circuit (described in more detail in the priority applications)
could go to infinite output voltage if there were no load present.
This situation can actually occur frequently. Consider the
situation in the morning when the sun first strikes a PV panel
string with power conditioners (17). There may be no grid
connection at this point and the inverter section may not draw any
power. In this case the power conditioner (17) might in practical
terms increase its output voltage until the inverter would break.
The inverter could have overvoltage protection on its input adding
additional power conversion components or, the power conditioner
may simply have its own internal output voltage limit. For example
if each power conditioner (17) could only produce 100 volts maximum
and there was a string of ten PCs in series the maximum output
voltage would be 1000 volts. This output voltage limit could make
the grid-tied inverter less complex or costly and is illustrated in
FIG. 6A as a preset overvoltage limit. Thus embodiments can present
maximum voltage determinative switching photovoltaic power
conversion control circuitry and maximum photovoltaic voltage
determinative duty cycle switching (as shown in FIG. 6A as the
preset overvoltage limit). This can be inverter specific and so an
additional aspect of embodiments of the invention can be the
inclusion of inverter protection schemes. The operation over the
potentially vast ranges of temperatures, insolations, and even
panel conditions or characteristics can cause such significant
variations in voltage and current because when trying to maintain
one parameter (such as sweet spot voltage or the like), some of
these variations can cause another parameter (such as output
current or the like) to exceed an inverter, building code, or
otherwise acceptable level. Embodiments of the present invention
can account for these aspects as well and may even provide this
through the DC-DC power converter (4) and/or the DC-AC inverter (5)
thus including inverter protection photovoltaic power conversion
control circuitry (33) at either or both levels. Considering
output, input, voltage and current limitations as initial examples,
it can be understood that embodiments can provide the steps of
providing photovoltaic inverter protection power conversion control
and even controlling a limited photovoltaic converter current
output through operation of the photovoltaic DC-DC converter (4).
These may be configured with consideration of maximum inverter
inputs and converter outputs so there can be included maximum
inverter input converter output control circuitry (37), maximum
inverter voltage determinative switching photovoltaic power
conversion control circuitry, or also the step of controlling a
maximum inverter input converter output. As alluded to above, each
of these more generic types of capabilities and elements as well as
others can be provided in a slaved manner so that either they
themselves are subservient to or dominant over another function and
thus embodiments can provide slaved photovoltaic power control
circuitry (34). As sometimes indicated in FIG. 1, such slaved
photovoltaic power control circuitry (34) (as well as various other
functions as a person of ordinary skill would readily understand)
can be provided at either the photovoltaic DC-DC power converter
(4), the DC-AC inverter (5), or both, or elsewhere. These can
include converter current output limited photovoltaic power control
circuitry, converter voltage output limited photovoltaic power
control circuitry, or the like. Thus, embodiments can have slaved
photovoltaic inverter protection control circuitry, or more
specifically, slaved photovoltaic current level control circuitry
or slaved photovoltaic voltage level control circuitry, or may
provide the steps of slavedly providing photovoltaic inverter
protection control of the photovoltaic DC-AC inverter (5), slavedly
controlling current from the photovoltaic DC-DC converter (4), or
the like. Considering such voltage and current limits, it can be
understood that system may more generally be considered as
including photovoltaic boundary condition power conversion control
circuitry and as providing the step of photovoltaic boundary
condition power conversion control. Thus, as illustrated in FIGS.
6A, 6B, and 8, boundary conditions may be set such as the
overcurrent limit and the overvoltage limit. And the DC-AC inverter
(5), the photovoltaic DC-DC converter (4), and/or either or both of
their control circuitries may serve as photovoltaic boundary
condition converter functionality control circuitry, may achieve a
photovoltaic boundary condition modality of photovoltaic DC-DC
power conversion, and may accomplish the step of controlling a
photovoltaic boundary condition of the photovoltaic DC-DC
converter.
[0053] In the above example of a maximum output current limit, it
should be understood that this may also be useful as illustrated in
FIG. 6A as a preset overcurrent limit. This is less straightforward
and is related to the nature of a PV panel. If a PV panel is
subjected to insufficient light its output voltage may drop but its
output current may not be capable of increasing. There can be an
advantage to only allowing a small margin of additional current.
For example, this same 100 watt panel which has a 100 volt maximum
voltage limit could also have a 2 amp current limit without
limiting its intended use. This may also greatly simplify the
following grid tied inverter stage. Consider an inverter in a large
installation which may need a crowbar shunt front end for
protection. Such could be provided in addition to duty cycle
control or the like. If the output of a PC could go to 100 amps the
crowbar would have to handle impractical currents. This situation
would not exist in a non PC environment as a simple PV panel string
could be easily collapsed with a crowbar circuit. This current
limit circuit may only be needed with a PC and it may be easily
achieved by duty cycle or more precisely switch operation control.
Once a current limit is included another BOS savings may be
realized. Now the wire size for interconnect of the series string
of PCs may be limited to only carry that maximum current limit.
Here embodiments can present maximum photovoltaic inverter current
converter functionality control circuitry, inverter maximum current
determinative switching, photovoltaic inverter maximum current
determinative duty cycle switch control circuitry, and photovoltaic
inverter maximum current determinatively duty cycle switching or
the like.
[0054] One more system problem may also be addressed. In solar
installations it may occur on rare conditions that a panel or field
of panels may be subjected to more than full sun. This may happen
when a refractory situation exists with clouds or other reflective
surfaces. It may be that a PV source may generate as much as 1.5
times the rated power for a few minutes. The grid tied inverter
section must either be able to operate at this higher power (adding
cost) or must somehow avoid this power. A power limit in the PC may
be the most effective way to solve this problem. In general,
protection of the DC-AC inverter (5) can be achieved by the
photovoltaic DC-DC converter (4) as an inverter protection modality
of the photovoltaic DC-DC power conversion or as inverter
protection converter functionality control circuitry. In
maintaining inverter sweet spot input, such circuitry can also
provide desirable inverter operating conditions, thus embodiments
may include photovoltaic inverter operating condition converter
functionality control circuitry. There may also be embodiments that
have small output voltage (even within an allowed output voltage
range). This may accommodate an inverter with a small energy
storage capacitor. The output voltage may even be coordinated with
an inverter's energy storage capability.
[0055] As mentioned above, certain aspect may be slaved to
(subservient) or may slave other aspects (dominant). One possible
goal in switching for some embodiments may include the maximum
power point operation and sweet spot operational characteristics
discussed above as well as a number of modalities as discussed
below. Some of these modalities may even be slaved such that one
takes precedence of one or another at some point in time, in some
power regime, or perhaps based on some power parameter to achieve a
variety of modalities of operation. There may be photovoltaic duty
cycle switching, and such may be controlled by photovoltaic duty
cycle switch control circuitry (again understood as encompassing
hardware, firmware, software, and even combinations of each). With
respect to the DC-AC inverter (5), there may be more generally the
slaved photovoltaic power control circuitry (34) mentioned above,
slaved inverter operating condition control circuitry, slaved
photovoltaic voltage level control circuitry and even the steps of
slavedly controlling voltage from the photovoltaic DC-DC converter
(4) or slavedly controlling operation of the photovoltaic DC-DC
converter (4).
[0056] Another aspect of some embodiments of the invention can be
protection or operation of components or the DC-AC inverter (5) so
as to address abrupt changes in condition. This can be accomplished
through the inclusion of soft transition photovoltaic power
conversion control circuitry (35) or the step of softly
transitioning a photovoltaic electrical parameter or more
specifically even softly transitioning a converted photovoltaic
power level electrical parameter. Thus, another mode of operation
may be to make a value proportional (in its broadest sense) to some
other aspect. For example, there can be advantages to making
voltage proportional to current such as to provide soft start
capability or the like. Thus embodiments may be configured for
controlling a maximum photovoltaic output voltage proportional to a
photovoltaic output current at least some times during the process
of converting a DC input to a DC output. In general, this may
provide soft transition photovoltaic power conversion control
circuitry (35). Focusing on voltage and current as only two such
parameters, embodiments can include ramped photovoltaic current
power conversion control circuitry, ramped photovoltaic voltage
power conversion control circuitry, or the steps of ramping (which
be linear or may have any other shape) a photovoltaic current
level, ramping a photovoltaic voltage level, or the like. One of
the many ways in which such soft transition can be accomplished can
be by making one parameter proportional to another. For example,
embodiments can include photovoltaic output voltage-photovoltaic
output current proportional control circuitry (39) or can provide
the step of controlling a photovoltaic output voltage proportional
to a photovoltaic output current.
[0057] Further, embodiments of the system may include duty cycle
control or switch operation that can be conducted so as to achieve
one or more proportionalities between parameters perhaps such as
the initial examples of maximum voltage output and current output
or the like. Further, not only can any of the above by combined
with any other of the above, but each may be provided in a slaved
manner such that consideration of one modality is secondary to or
dominant over that of another modality.
[0058] As mentioned above one technique of some control activities
can be through the use of duty cycle switching or the like.
Switches on either or both of the photovoltaic DC-DC power
converter (4) or the DC-AC inverter (5) can be controlled in a
variable duty cycle mode of operation such that frequency of
switching alters to achieve the desired facet. The converter
functionality control circuitry (8), perhaps providing the step of
maximum photovoltaic power point duty cycle switching of a
photovoltaic DC-DC converter, or the inverter control circuitry
(38) may serve as photovoltaic duty cycle switch control circuitry.
The duty cycle operations and switching can achieve a variety of
results, from serving as photovoltaic transformation duty cycle
switching, to photovoltaic impedance transformation duty cycle
switching, to photovoltaic input control duty cycle switching, to
photovoltaic output duty cycle switching, to photovoltaic voltage
duty cycle switching, to photovoltaic current duty cycle switching,
to soft transition duty cycle switching, to photovoltaic
optimization duty cycle switching, to other operations. The
photovoltaic inverter duty cycle switch control circuitry (31) may
even act to provide the step of maximum photovoltaic voltage
determinatively duty cycle switching the DC-AC inverter (5).
[0059] A variety of results have been described above. These may be
achieved by simply altering the duty cycle of or switches affected
by the switches. These can be accomplished based on thresholds and
so provide threshold triggered alternative mode, threshold
determinative, threshold activation, or threshold deactivation
switching photovoltaic power conversion control circuitry. A burst
mode of operation perhaps such as when nearing a mode alteration
level of operation may be provided and at such times frequency can
be halved, opposing modes can be both alternated, and level can be
reduced as a change become incipient. This can be transient as
well. In these manners burst mode switching photovoltaic power
conversion control circuitry and burst mode switching can be
accomplished, as well as transient opposition mode photovoltaic
duty cycle switch control circuitry and even the step of
transiently establishing opposing switching modes.
[0060] As discussed in more detail in the priority applications,
there may be a variety of modes of operation of a photovoltaic
DC-DC power converter (4). These may include modes of increasing
and, perhaps alternatively, decreasing photovoltaic load impedance,
the output, or otherwise. Systems according to embodiments of the
invention may combine inverter aspects with a photovoltaic DC-DC
power converter (4) that serves as a multimodal photovoltaic DC-DC
power converter perhaps controlled by multimodal converter
functionality control circuitry (26) in that it has more than one
mode of operation. These modes may include, but should be
understood as not limited to, photovoltaic output increasing and
photovoltaic output decreasing, among others. In general, the
aspect of multimodal activity encompasses at least processes where
only one mode of conversion occurs at any one time.
[0061] Thus, a power conditioner (17) may provide at least first
modality and second modality photovoltaic DC-DC power conversion
circuitry, DC-DC power converter, or DC-DC power conversion in
conjunction with the inverter capabilities discussed herein. By
offering the capability of more than one mode of operation (even
though not necessarily utilized at the same time), or in offering
the capability of changing modes of operation, the system may
accomplish the step of multimodally operating. Similarly, by
offering the capability of controlling to effect more than one mode
of conversion operation (again, even though not necessarily
utilized at the same time), or in controlling to change modes of
operation, the system may accomplish the step of multimodally
controlling operation of a photovoltaic DC-DC power converter (4)
or a DC-AC inverter (5).
[0062] Embodiments may include a photovoltaic DC-DC power converter
(4) that has even two or more modes of operation and thus may be
considered a dual mode power conversion circuit or dual mode
converter. The dual mode nature of this circuit may embody a
significant benefit and another distinction may be that most DC/DC
converters are often intended to take an unregulated source and
produce a regulated output. In this invention, the input to the
DC/DC converter is regulated either up or down--and in a highly
efficient manner--to be at the PV panel MPP. The dual mode nature
of the converter may also serve to facilitate an effect caused by
the inverter's operation even without a direct connection. Of
course, such modes of operation can be adapted for application with
respect to the inverter's duty cycle switching as well.
[0063] As mentioned above, the PCs and photovoltaic DC-DC power
converters (4) may handle individual panels. They may be attached
to a panel, to a frame, or separate. Embodiments may have
converters physically integral to such panels in the sense that
they are provided as one attached unit for ultimate installation.
This can be desirable such as when there are independent operating
conditions for separate solar sources, and even adjacent solar
sources to accommodate variations in insolation, condition, or
otherwise. Each panel or the like may achieve its own MPP, and may
coordinate protection with all others in a string or the like.
[0064] As may be understood, systems can include an aspect of
reacting to operational conditions to which elements are subjected.
This can occur in a dynamic fashion so that as one condition
changes, nearly instantly a reaction to control appropriately is
caused. They can also react to installation conditions and can
react to the particular elements. This can make installation
easier. For example, if connected to differing types of solar
panels, differing age or condition elements, differing types of
converters, or even differing types of inverters, some embodiments
of the invention can automatically act to accommodate the element,
to stay within code, or to otherwise act so that regardless of the
overall system or the overall dissimilarity, an optimal result can
be achieved. Again this dynamically reactive control feature can be
configured at either or both the photovoltaic DC-DC power converter
(4) or the DC-AC inverter (5). At either location, embodiments can
provide dynamically reactive internal output limited photovoltaic
power control circuitry (42) it can also provide the step of
dynamically reactively controlling an internal output or even
dynamically reactively converting. Both of these features, or even
any other dynamically reactive capability, can be slaved either
dominantly or subserviently. Thus, embodiments of the invention can
provide slaved dynamically reactive photovoltaic power control
circuitry or the step of slavedly dynamically reactively
controlling an aspect of the system. This could include slavedly
dynamically reactively controlling an internal output through
operation of the photovoltaic DC-DC converter (4).
[0065] The aspect of addressing an external as well as an internal
output can be helpful to meeting code or other requirements when
there is no way to know what type of panel or other component the
system is hooked to. In situations where an internal signal
(perhaps such as the signal transmitting power from a rooftop
collection of panels to a basement inverter grid connection) is not
permitted to exceed a specified level of voltage, current, or
otherwise needs to meet limitations on existing wiring or circuit
breakers or the like, embodiments can provide the dynamically
reactive control as code compliant dynamically reactive
photovoltaic power control circuitry (41). It may also provide the
step of code compliantly dynamically reactively controlling an
internal output. This can occur through operation of the
photovoltaic DC-DC converter (4), the DC-AC inverter (5), or
otherwise. Of course this code complaint feature can be slaved to
take dominance over other features such as MPP activity, sweet spot
activity, boundary condition activity, or the like. In this manner
embodiments can provide slaved code compliant dynamically reactive
photovoltaic power control circuitry or can provide the step of
slavedly code compliantly dynamically reactively controlling
internal output, perhaps through operation of the photovoltaic
DC-DC converter (4) or otherwise. Beyond code compliance, it can be
readily understood how the general feature of a dynamically
reactive control can act to permit connection to existing or
dissimilar sources as well. Thus whether by programming, circuitry,
or other configuration, embodiments can provide dynamically
multisource reactive photovoltaic power control circuitry (43) or
may provide the step of multisource dynamically reactively
controlling internal output, perhaps through operation of the
photovoltaic DC-DC converter (4). Of course this can all be
accomplished while maintaining the inverter input at an optimum
level in appropriate circumstances and thus embodiments can include
reactive inverter input optimization photovoltaic power control
circuitry.
[0066] As the invention becomes more accepted it may be
advantageous to permit comparison with more traditional
technologies or operating conditions. This can be achieved by
simple switch operation whereby traditional modes of operation can
be duplicated or perhaps adequately mimicked to permit a
comparison. Thus, for a solar focus, embodiments may include a
solar power conversion comparator (44) that can compare first and
second modes of operation, perhaps the improved mode of an
embodiment of the present invention and a traditional, less
efficient mode. This comparator may involve indicating some solar
energy parameter for each. In this regard, the shunt switch
operation disable element may be helpful. From this a variety of
difference can be indicated, perhaps: solar power output, solar
power efficiency differences, solar power cost differences, solar
power insolation utilization comparisons, and the like. Whether
through software or hardware or otherwise, embodiments can include
an ability to function with a first power capability and a second
power capability. These may be traditional and improved
capabilities, perhaps such as a traditional power conversion
capability and an improved power conversion capability or a
traditional power inversion capability and an improved power
inversion capability. The inverter control circuitry (38) or the
converter functionality control circuitry (8) or otherwise can be
configured to achieve either or both of these first and second
capabilities. As one example, the inverter can act to achieve an
input voltage that would have been seen without the features of the
present invention and thus embodiments can provide an off-maximum
efficiency inverter input voltage control (47) or may act to
provide the step of controlling inverter input voltage off a
maximum efficiency level. In instances where the improved
embodiment achieves inverter sweet spot operation capability,
embodiments may act to compare the steps of traditionally power
inverting a DC photovoltaic input and sweet spot input inverting a
DC photovoltaic input. Any of these can provide a user any type of
output to inform the user for comparison with other systems.
[0067] By the above combinations of these concepts and circuitry,
at least some of the following benefits may be realized: [0068]
Every PV panel may produce its individual maximum power. Many
estimates today indicate this may increase the power generated in a
PV installation by 20% or even more. [0069] The grid tied inverter
may be greatly simplified and operate more efficiently. [0070] The
Balance of System costs for a PV installation may be reduced.
[0071] The circuitry, concepts and methods of various embodiments
of the invention may be broadly applied. It may be that one or more
PCs per panel may be used. For example there may be
non-uniformities on a single panel or other reasons for harvesting
power from even portions of a panel. It may be for example that
small power converters may be used on panel segments optimizing the
power which may be extracted from a panel. This invention is
explicitly stated to include sub panel applications.
[0072] This invention may be optimally applied to strings of
panels. It may be more economical for example to simply use a PC
for each string of panels in a larger installation. This could be
particularly beneficial in parallel connected strings if one string
was not able to produce much power into the voltage the remainder
of the strings is producing. In this case one PC per string may
increase the power harvested from a large installation.
[0073] This invention is assumed to include many physical
installation options. For example there may be a hard physical
connection between the PC and a panel. There may be an
interconnection box for strings in which a PC per string may be
installed. A given panel may have one or more PCs incorporated into
the panel. A PC may also be a stand-alone physical entity.
[0074] All of the foregoing is discussed at times in the context of
a solar power application. As may be appreciated, some if not all
aspects may be applied in other contexts as well. Thus, this
disclosure should be understood as supporting other applications
regardless how applied.
[0075] As can be easily understood from the foregoing, the basic
concepts of the present invention may be embodied in a variety of
ways. It involves both solar power generation techniques as well as
devices to accomplish the appropriate power generation. In this
application, the power generation techniques are disclosed as part
of the results shown to be achieved by the various circuits and
devices described and as steps which are inherent to utilization.
They are simply the natural result of utilizing the devices and
circuits as intended and described. In addition, while some
circuits are disclosed, it should be understood that these not only
accomplish certain methods but also can be varied in a number of
ways. Importantly, as to all of the foregoing, all of these facets
should be understood to be encompassed by this disclosure.
[0076] The discussion included in this application is intended to
serve as a basic description. The reader should be aware that the
specific discussion may not explicitly describe all embodiments
possible; many alternatives are implicit. It also may not fully
explain the generic nature of the invention and may not explicitly
show how each feature or element can actually be representative of
a broader function or of a great variety of alternative or
equivalent elements.
[0077] Again, these are implicitly included in this disclosure.
Where the invention is described in device-oriented terminology,
each element of the device implicitly performs a function.
Apparatus claims may not only be included for the devices and
circuits described, but also method or process claims may be
included to address the functions the invention and each element
performs. Neither the description nor the terminology is intended
to limit the scope of the claims that will be included in any
subsequent patent application.
[0078] It should also be understood that a variety of changes may
be made without departing from the essence of the invention. Such
changes are also implicitly included in the description. They still
fall within the scope of this invention. A broad disclosure
encompassing both the explicit embodiment(s) shown, the great
variety of implicit alternative embodiments, and the broad methods
or processes and the like are encompassed by this disclosure and
may be relied upon when drafting the claims for any subsequent
patent application. It should be understood that such language
changes and broader or more detailed claiming may be accomplished
at a later date. With this understanding, the reader should be
aware that this disclosure is to be understood to support any
subsequently filed patent application that may seek examination of
as broad a base of claims as deemed within the applicant's right
and may be designed to yield a patent covering numerous aspects of
the invention both independently and as an overall system.
[0079] Further, each of the various elements of the invention and
claims may also be achieved in a variety of manners. Additionally,
when used or implied, an element is to be understood as
encompassing individual as well as plural structures that may or
may not be physically connected. This disclosure should be
understood to encompass each such variation, be it a variation of
an embodiment of any apparatus embodiment, a method or process
embodiment, or even merely a variation of any element of these.
Particularly, it should be understood that as the disclosure
relates to elements of the invention, the words for each element
may be expressed by equivalent apparatus terms or method
terms--even if only the function or result is the same.
[0080] Such equivalent, broader, or even more generic terms should
be considered to be encompassed in the description of each element
or action. Such terms can be substituted where desired to make
explicit the implicitly broad coverage to which this invention is
entitled. As but one example, it should be understood that all
actions may be expressed as a means for taking that action or as an
element which causes that action. Similarly, each physical element
disclosed should be understood to encompass a disclosure of the
action which that physical element facilitates. Regarding this last
aspect, as but one example, the disclosure of a "converter" should
be understood to encompass disclosure of the act of
"converting"--whether explicitly discussed or not--and, conversely,
were there effectively disclosure of the act of "converting", such
a disclosure should be understood to encompass disclosure of a
"converter" and even a "means for converting" Such changes and
alternative terms are to be understood to be explicitly included in
the description.
[0081] Any patents, publications, or other references mentioned in
this application for patent or its list of references are hereby
incorporated by reference. Any priority case(s) claimed at any time
by this or any subsequent application are hereby appended and
hereby incorporated by reference. In addition, as to each term used
it should be understood that unless its utilization in this
application is inconsistent with a broadly supporting
interpretation, common dictionary definitions should be understood
as incorporated for each term and all definitions, alternative
terms, and synonyms such as contained in the Random House Webster's
Unabridged Dictionary, second edition are hereby incorporated by
reference. Finally, all references listed in the List of References
or other information statement filed with or included in the
application are hereby appended and hereby incorporated by
reference, however, as to each of the above, to the extent that
such information or statements incorporated by reference might be
considered inconsistent with the patenting of this/these
invention(s) such statements are expressly not to be considered as
made by the applicant(s).
[0082] Thus, the applicant(s) should be understood to have support
to claim and make a statement of invention to at least: i) each of
the power source devices as herein disclosed and described, ii) the
related methods disclosed and described, iii) similar, equivalent,
and even implicit variations of each of these devices and methods,
iv) those alternative designs which accomplish each of the
functions shown as are disclosed and described, v) those
alternative designs and methods which accomplish each of the
functions shown as are implicit to accomplish that which is
disclosed and described, vi) each feature, component, and step
shown as separate and independent inventions, vii) the applications
enhanced by the various systems or components disclosed, viii) the
resulting products produced by such systems or components, ix) each
system, method, and element shown or described as now applied to
any specific field or devices mentioned, x) methods and apparatuses
substantially as described hereinbefore and with reference to any
of the accompanying examples, xi) the various combinations and
permutations of each of the elements disclosed, xii) each
potentially dependent claim or concept as a dependency on each and
every one of the independent claims or concepts presented, and
xiii) all inventions described herein. In addition and as to
computerized aspects and each aspect amenable to programming or
other programmable electronic automation, the applicant(s) should
be understood to have support to claim and make a statement of
invention to at least: xiv) processes performed with the aid of or
on a computer as described throughout the above discussion, xv) a
programmable apparatus as described throughout the above
discussion, xvi) a computer readable memory encoded with data to
direct a computer comprising means or elements which function as
described throughout the above discussion, xvii) a computer
configured as herein disclosed and described, xviii) individual or
combined subroutines and programs as herein disclosed and
described, xix) the related methods disclosed and described, xx)
similar, equivalent, and even implicit variations of each of these
systems and methods, xxi) those alternative designs which
accomplish each of the functions shown as are disclosed and
described, xxii) those alternative designs and methods which
accomplish each of the functions shown as are implicit to
accomplish that which is disclosed and described, xxiii) each
feature, component, and step shown as separate and independent
inventions, and xxiv) the various combinations and permutations of
each of the above.
[0083] With regard to claims whether now or later presented for
examination, it should be understood that for practical reasons and
so as to avoid great expansion of the examination burden, the
applicant may at any time present only initial claims or perhaps
only initial claims with only initial dependencies. The office and
any third persons interested in potential scope of this or
subsequent applications should understand that broader claims may
be presented at a later date in this case, in a case claiming the
benefit of this case, or in any continuation in spite of any
preliminary amendments, other amendments, claim language, or
arguments presented, thus throughout the pendency of any case there
is no intention to disclaim or surrender any potential subject
matter. Both the examiner and any person otherwise interested in
existing or later potential coverage, or considering if there has
at any time been any possibility of an indication of disclaimer or
surrender of potential coverage, should be aware that in the
absence of explicit statements, no such surrender or disclaimer is
intended or should be considered as existing in this or any
subsequent application. Limitations such as arose in Hakim v.
Cannon Avent Group, PLC, 479 F.3d 1313 (Fed. Cir 2007), or the like
are expressly not intended in this or any subsequent related
matter.
[0084] In addition, support should be understood to exist to the
degree required under new matter laws--including but not limited to
European Patent Convention Article 123(2) and United States Patent
Law 35 USC 132 or other such laws--to permit the addition of any of
the various dependencies or other elements presented under one
independent claim or concept as dependencies or elements under any
other independent claim or concept. In drafting any claims at any
time whether in this application or in any subsequent application,
it should also be understood that the applicant has intended to
capture as full and broad a scope of coverage as legally available.
To the extent that insubstantial substitutes are made, to the
extent that the applicant did not in fact draft any claim so as to
literally encompass any particular embodiment, and to the extent
otherwise applicable, the applicant should not be understood to
have in any way intended to or actually relinquished such coverage
as the applicant simply may not have been able to anticipate all
eventualities; one skilled in the art, should not be reasonably
expected to have drafted a claim that would have literally
encompassed such alternative embodiments.
[0085] Further, if or when used, the use of the transitional phrase
"comprising" is used to maintain the "open-end" claims herein,
according to traditional claim interpretation. Thus, unless the
context requires otherwise, it should be understood that the term
"comprise" or variations such as "comprises" or "comprising", are
intended to imply the inclusion of a stated element or step or
group of elements or steps but not the exclusion of any other
element or step or group of elements or steps. Such terms should be
interpreted in their most expansive form so as to afford the
applicant the broadest coverage legally permissible.
[0086] Finally, any claims set forth at any time are hereby
incorporated by reference as part of this description of the
invention, and the applicant expressly reserves the right to use
all of or a portion of such incorporated content of such claims as
additional description to support any of or all of the claims or
any element or component thereof, and the applicant further
expressly reserves the right to move any portion of or all of the
incorporated content of such claims or any element or component
thereof from the description into the claims or vice-versa as
necessary to define the matter for which protection is sought by
this application or by any subsequent continuation, division, or
continuation-in-part application thereof, or to obtain any benefit
of, reduction in fees pursuant to, or to comply with the patent
laws, rules, or regulations of any country or treaty, and such
content incorporated by reference shall survive during the entire
pendency of this application including any subsequent continuation,
division, or continuation-in-part application thereof or any
reissue or extension thereon.
* * * * *