NZ712076B2 - Single phase inverters cooperatively controlled to provide one, two, or three phase unipolar electricity - Google Patents
Single phase inverters cooperatively controlled to provide one, two, or three phase unipolar electricity Download PDFInfo
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- NZ712076B2 NZ712076B2 NZ712076A NZ71207612A NZ712076B2 NZ 712076 B2 NZ712076 B2 NZ 712076B2 NZ 712076 A NZ712076 A NZ 712076A NZ 71207612 A NZ71207612 A NZ 71207612A NZ 712076 B2 NZ712076 B2 NZ 712076B2
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- output terminal
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- input terminal
- switch
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- 230000005611 electricity Effects 0.000 title description 4
- 239000003990 capacitor Substances 0.000 claims abstract description 93
- 238000004146 energy storage Methods 0.000 claims description 6
- 230000002457 bidirectional effect Effects 0.000 claims description 5
- 238000004891 communication Methods 0.000 description 50
- 238000010248 power generation Methods 0.000 description 41
- 238000000034 method Methods 0.000 description 27
- 238000010586 diagram Methods 0.000 description 12
- 230000006870 function Effects 0.000 description 12
- 238000006243 chemical reaction Methods 0.000 description 10
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- 229910002601 GaN Inorganic materials 0.000 description 7
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- 238000005516 engineering process Methods 0.000 description 7
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 7
- 229910010271 silicon carbide Inorganic materials 0.000 description 7
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- 238000007689 inspection Methods 0.000 description 4
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- 230000003247 decreasing effect Effects 0.000 description 2
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- 150000002500 ions Chemical class 0.000 description 2
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- 230000003287 optical effect Effects 0.000 description 2
- 230000007704 transition Effects 0.000 description 2
- 238000011144 upstream manufacturing Methods 0.000 description 2
- 230000004913 activation Effects 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
- H02J2300/22—The renewable source being solar energy
- H02J2300/24—The renewable source being solar energy of photovoltaic origin
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/381—Dispersed generators
-
- H02J3/383—
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
- H02M1/007—Plural converter units in cascade
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
- H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/493—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode the static converters being arranged for operation in parallel
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/539—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency
- H02M7/5395—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency by pulse-width modulation
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
Abstract
Disclosed is a power converter unit (102) includes a direct current ("DC") to DC converter (104). The DC to DC converter (104) comprises a positive input terminal (110), a negative input terminal (112), a first capacitor (522), a first coil (504), a first switch (506), a second switch (508), a second capacitor (536), a positive DC output terminal (116) and a negative DC output terminal (118). An input terminal of the first capacitor (522) is connected to the positive input terminal (110) and an output terminal of the first capacitor (522) is connected to the negative input terminal (112). An input terminal of the first coil (504) is connected to the input terminal of the first capacitor (522). An input terminal of the first switch (506) is connected to an output terminal of the first coil (504) and an output terminal of the first switch (506) is connected to the negative input terminal (112). An input terminal of the second switch (508) is connected to the output terminal of the first coil (504). An input terminal of the second capacitor (536) is connected to an output terminal of the second switch (508) and an output terminal of the second capacitor (536) is connected to the negative input terminal (112). The positive DC output terminal (116) is connected to the input terminal of the second capacitor (536) and the negative DC output terminal (118) is connected to the output terminal of the second capacitor (536). The power converter unit (102) also includes a unipolar power converter (106). The unipolar power converter (106) comprises a second coil (510), a third switch (512), a fourth switch (514), a third coil (516), a third capacitor (518) and a unipolar power output terminal (120). An input terminal of the second coil (510) is connected to the input terminal of the second capacitor (536). An input terminal of the third switch (512) is connected to an output terminal of the second coil (510). An input terminal of the fourth switch (514) is connected to the output terminal of the second capacitor (536) and an output terminal of the fourth switch (514) is connected to an output terminal of the third switch (512). An input terminal of the third coil (516) is connected to the output terminal of the third switch (512) and the output terminal of the fourth switch (514). An input terminal of the third capacitor (518) is connected to an output terminal of the third coil (516) and an output terminal of the third capacitor (518) is connected to the input terminal of the fourth switch (514). The unipolar power output terminal (120) is connected to the input terminal of the third capacitor (518). The power converter unit (102) also includes a controller (107) coupled to the first, second, third, and fourth switches (506, 508, 512, 514), wherein the controller (107) is configured to control the operation of each switch to generate a positive DC voltage at the positive DC output terminal (116), a negative DC voltage at the negative DC output terminal (118), and a unipolar power output at the unipolar power output terminal (120). d capacitor (536), a positive DC output terminal (116) and a negative DC output terminal (118). An input terminal of the first capacitor (522) is connected to the positive input terminal (110) and an output terminal of the first capacitor (522) is connected to the negative input terminal (112). An input terminal of the first coil (504) is connected to the input terminal of the first capacitor (522). An input terminal of the first switch (506) is connected to an output terminal of the first coil (504) and an output terminal of the first switch (506) is connected to the negative input terminal (112). An input terminal of the second switch (508) is connected to the output terminal of the first coil (504). An input terminal of the second capacitor (536) is connected to an output terminal of the second switch (508) and an output terminal of the second capacitor (536) is connected to the negative input terminal (112). The positive DC output terminal (116) is connected to the input terminal of the second capacitor (536) and the negative DC output terminal (118) is connected to the output terminal of the second capacitor (536). The power converter unit (102) also includes a unipolar power converter (106). The unipolar power converter (106) comprises a second coil (510), a third switch (512), a fourth switch (514), a third coil (516), a third capacitor (518) and a unipolar power output terminal (120). An input terminal of the second coil (510) is connected to the input terminal of the second capacitor (536). An input terminal of the third switch (512) is connected to an output terminal of the second coil (510). An input terminal of the fourth switch (514) is connected to the output terminal of the second capacitor (536) and an output terminal of the fourth switch (514) is connected to an output terminal of the third switch (512). An input terminal of the third coil (516) is connected to the output terminal of the third switch (512) and the output terminal of the fourth switch (514). An input terminal of the third capacitor (518) is connected to an output terminal of the third coil (516) and an output terminal of the third capacitor (518) is connected to the input terminal of the fourth switch (514). The unipolar power output terminal (120) is connected to the input terminal of the third capacitor (518). The power converter unit (102) also includes a controller (107) coupled to the first, second, third, and fourth switches (506, 508, 512, 514), wherein the controller (107) is configured to control the operation of each switch to generate a positive DC voltage at the positive DC output terminal (116), a negative DC voltage at the negative DC output terminal (118), and a unipolar power output at the unipolar power output terminal (120).
Description
SINGLE PHASE INVERTERS COOPERATIVELY CONTROLLED TO
PROVIDE ONE, TWO, OR THREE PHASE UNIPOLAR ELECTRICITY
RELATED PATENT APPLICATIONS
The present application is a divisional of New Zealand Patent application No.
625048 filed on 20 November 2012. The entire contents of the New Zealand Patent
Application No. 625048 are incorporated herein by reference.
FIELD OF THE INVENTION
The present invention relates generally to electrical power conversion, and more
specifically to the conversion of direct current (DC) power to alternating current (AC) power.
BACKGROUND
Large power generation systems may provide megawatt class power generation
capacity. Various large power generation system configurations may be used, including
mirrors for focusing sunlight intensely on a small solar panel or collection of panels. In
another large power generation system, there may be many thousands, even millions of
photovoltaic panels employed. The panels may be electronically controlled to provide
efficient power conversion and safe operation. A variety of apparatus and methods may be
used to convert the DC power of a photovoltaic panel into AC power which may be provided
to a load. Examples of conversion equipment include microinverters, inverters, and array
converters.
As conversion efficiencies have improved, both for sunlight to DC electrical current
and DC electrical current to AC power, capital costs have become increasingly important.
The cost of installation and materials, for example the connectors and wiring between panels
and between a string of panels and a consolidated distribution point, may be significantly
increased by power generation systems employing a large number of panels. In some
configurations, the solar panels may be connected in a series-parallel arrangement, providing
a powerful DC signal to a remotely located inverter system. Such a configuration may have
several disadvantages. For example, extra wiring and connectors may be required between
the solar panels and the inverter system, which may add both material and labor costs, as well
as add transmission power losses. Also, an inverter controlling a string of solar panels may
operate at a condition that maximizes the power provided by the entire string, which may
result in sub-optimizing the power delivered by each individual panel, and therefore the
power delivered by the entire string. Microinverters may be connected to each panel and may
control a given panel to that panel's maximum power delivery condition, but the use of
individual microinverters to provide a three phase electrical output may lead to increased cost
and complexity of the microinverters and the power generation system. Single phase
inverters may have an increased complexity due to their requirement to provide both positive
and negative voltage signals, and may increase the number of switches and other components
comprising a power generation system.
SUMMARY
The systems, methods, and devices of the various embodiments provide single phase
inverters that may be cooperatively controlled to provide one, two, or three phase unipolar
electricity. In the various embodiments, cost of manufacturing and install.at ion may be
reduced by the various embodiments while providing efficient power conversion. In an
embodiment a solar panel may be connected to a DC to DC converter and a unipolar power
converter, and the DC to DC converter may control the solar panel to a maximum power
conversion condition. In an embodiment, the unipolar power converter output may be a
single phase signal approximating a desired voltage waveform and frequency, offset from the
ground electrical potential such that the voltage output signal may be always positive, thus
"unipolar''. The unipolar power output of each string of solar panels may be connected to a
dedicated, predetermined phase of a load, such as a three phase grid system. The DC output
of a DC to DC converter may be connected in parallel with other DC to DC converters and
other unipolar converters. A unipolar converter may receive DC power from its respective
DC to DC converter, or from one or more of the other DC to DC converters electrically
connected in parallel.
In an embodiment, the DC and unipolar output of a string of solar panels may be
connected to certain input terminals of a combiner enclosure. The combiner enclosure may
adjust the voltage of the electrical power to match that of an electrically connected load , for
example an electrical grid. The combiner enclosure may also interconnect the DC lines. In the
various embodiments the combiner enclosure may include a controller and other means for
detecting unsafe conditions, such as electrical arcing or an upstream system failure.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated herein and constitute part of
this specification, illustrate exemplary aspects of the invention, and, together with the general
description given above and the detailed description given below, serve to explain features of
the invention.
FIG. l is a component block diagram of an embodiment power generation system.
is a component block diagram of another embodiment power generation
system.
is a component block diagram of a third embodiment power generation
system.
is a component block diagram of a fourth embodiment power generation
system.
is a component block diagram of a fifth embodiment power generation
system.
is a component block diagram of a sixth embodiment power generation
system.
FIG . 5 is circuit diagram of an embodiment power converter unit.
is a graph of a three phase power output.
is a graph of a two phase power output.
is a graph relating time, voltage, current, and switching periods.
is a graph relating individual power and total power outputs over time.
is a process flow diagram illustrating an embodiment method for power
converter unit control.
is a process flow diagram illustrating another embodiment method for
power converter unit control.
is a process flow diagram illustrating an embodiment method for power
converter unit activation.
is a process flow diagram illustrating an embodiment combiner enclosure
control method.
DETAILED DESCRIPTION
The various embodiments will be described in detail with reference to the
accompanying drawings. Wherever possible, the same reference numbers will be used
throughout the drawings to refer to the same or like parts. References made to particular
examples and implementations arc for illustrative purposes, and arc not intended to limit the
scope of the invention or the claims.
The word "exemplary" is used herein to mean "serving as an example, instance, or
illustration." Any implementation described herein as "exemplary" is not necessarily to be
construed as preferred or advantageous over other implementations.
The various embodiments are described herein using the example of a photovoltaic
or solar panel as a DC input. This example is useful for describing the various components
and functionality of the embodiment devices, systems, and methods. However, the
embodiment s and the scope of the claims are not limited to such a configuration unless
specifically recited. Describing the embodiments in terms of other potential applications
would be unnecessary and repetitive. Thus, the terms "solar panel" or "photovoltaic panel"
are used herein to refer generally to any form DC input which the embodiments could be
applied, and is not intended to limit the scope of the claims unless specifically recited.
In the industry a symmetrical two phase system may often be referred to as an
"Edison" system or a "single phase" system because the two phases are split in a residence
power panel and the two phases each distributed as a single phase. For clarity and
consistency, herein "single phase" means one phase and "two phase" means an Edison or
symmetrical two phase system.
The systems, methods, and devices of the various embodiments provide single phase
inverters that may be cooperatively controlled to provide one, two, or three phase unipolar
electricity. In the various embodiments, cost of manufacturing and installation may be
reduced while providing efficient power conversion. In an embodiment, a solar panel may be
connected to a DC to DC converter and a unipolar power converter. The DC to DC converter
may control the solar panel to a maximum power conversion condition. The unipolar power
converter output may be a single phase signal approximating a desired voltage waveform and
frequency, offset from the ground electrical potential such that the voltage output signal may
be always positive, thus "unipolar". The unipolar power output of each string of solar panels
may be connected to a dedicated, predetermined phase of a load, such as a three phase grid
system. The DC output of a DC to DC converter may be connected in parallel with other DC
to DC converters and other unipolar converters. A unipolar converter may receive DC power
from its respective DC to DC converter, or from one or more of the other DC to DC
converters electrically connected in parallel.
In an embodiment, the DC and unipolar output of a string of solar panels may be
connected to certain input terminals of a combiner enclosure. The combiner enclosure may
adjust the voltage of the electrical power to match that of an electrically connected load, for
example an electrical grid. The combiner enclosure may also interconnect the DC lines. In the
various embodiments the combiner enclosure may include a controller and other means for
detecting un safe conditions, such as electrical arcing or an upstream system failure.
FIG . 1 illustrates an embodiment single phase power generation system 100. Phase
A 132 may be comprised of a power converter unit ("PCU") 102. The PCU 102 may be
comprised of a DC to DC converter 104 electrically connected with a unipolar power
converter I 06 and a controller 107. Additional components of the PCU 102 are discussed
below. The PCU 102 may be comprised of one enclosure containing the DC to DC converter
104, the unipolar power converter 106, and the controller 107. In an alternative embodiment,
the PCU 102 may comprise a separate enclosure each for the DC to DC converter 104, the
unipolar power converter 106, and the controller 107. The DC to DC converter 104 may be
connected to a photovoltaic panel ("PV") 108 by lines 110 and 112. In operation, the DC to
DC converter 104 may receive positive electrical current on line 110 from the PV 108, and
line 112 may act as an electrical return line to complete the circuit between the DC to DC
converter 104 and the PV 108 In operation, the DC to DC converter 104 may boost the
voltage received from the PV 108 to a DC voltage of a value of at least the peak to peak value
of a unipolar voltage expected from the unipolar power converter 106 plus an offset voltage
value, for example ten volts (10V) DC. The unipolar power converter 106 may receive a DC
signal from the DC to DC converter 104 via an internal connection. The controller 107 may
monitor and control the operation of the DC to DC converter 104 and the unipolar power
converter 106.
The PCU 102 may be electrically connected to a combiner enclosure 114 by three
lines: a positive fixed voltage DC line 116, a negative fixed voltage DC line 118, and a
unipolar power line 120. In an embodiment, the three lines 116, 118, and 120 may be encased
within an outer sheath 122 and form a single cable that may form a three-wire interconnect
ion from the PCU 102 to the combiner enclosure 114. The DC lines 116 and 1 18 may
provide a positive and a negative DC line referred to herein after as a "link" 124 and the
voltage between the two lines 116, 118 as a "Vlink." The controller 11 07 of the PCU 102
may contain a communication module to inject communication signals into the link 124 or
receive communication signals from the link 124. In an alternative embodiment, the
communication module may transmit and/or receive communication signals via other
communication channel s (e.g., via wireless or wired network connections) in addition to, or
in place of, communication signals injected into/received from the link 124.
DC lines 116 and 118 may be connected to a capacitor C1 128. The capacitor C1
128 may be a large capacitor or any other energy storage device, such as a bidirectional
battery charger. The capacitor C1 128 may absorb transients, for example 120Hz artifacts,
that may occur. The capacitor C1 128 may be a low frequency capacitor of a few hundred
microfarads, such as an electrolytic capacitor. Output A may be the output of the unipolar
power line 120 which may be a single phase signal approximating a desired voltage
waveform and frequency, offset from the ground electrical potential such that the voltage
output signal may be always positive, thus "unipolar." Output Vo may be the DC output of
DC lines 116 and 118.
A controller 142 within the combiner enclosure 1 14 may monitor DC lines 116 and
118 via lines A and B, respectively. The controller 142 may contain a programmable
controller or processor 144, a memory 146, and a communication module 148. The
programmable controller 144 may allow the controller 142 to perform logic operations,
perform control operations, perform monitoring operations, and perform communication
operations in response to information stored in the memory 146. The lines A, B, and C may
be coupled to the programmable controller 144 such that signals from the programmable
controller 144 may be sent and/or received via the lines A, B, and C. The controller 142 may
control the operation of relay 126 via control line C. As an example, relay 126 may be a
single MOSFET, though any known type of technology capable of performing a switching
function, including relays, transistors, bi-polar transistors, insulated-gate bipolar transistors
(IGBTs), silicon carbide or gallium nitride transistors, thyristors, series connected MOSFETs,
thyristor emulators, and diodes in series with JGBTs may be used. The controller 142 may
contain a communication module 148 coupled to the programmable controller 144 to inject
communication signals into the link 124 or receive communication signals from the link 124
via lines A or B. In this manner, controller 107 of the PCU 102 may communicate with the
controller 142 of the combiner enclosure 114. Communication between the controllers 107
and 142 may include reporting power provided, PV 108 voltage or current, status of the
unipolar power converter 106, and receiving commands to enable or disable the unipolar
power converter 106. In an alternative embodiment, the communication module 148 may
transmit and/or receive communication signals via other communication channels (e.g., via
wireless or wired network connections) in addition to, or in place of, communication signals
injected into/received from the link 124.
The controller 142 may have anti-islanding capabilities and may detect arc faults on
the link 124 by monitoring line A and/or B. In operation, if an arc fault is detected on the link
124, the unipolar power line 120 may be disconnected by opening the relay 126. The
controller 107 in the PCU 102 may detect the disconnection of the unipolar power line 120,
and may stop the DC to DC converter 104, and may disconnect the PCU 102 from the link
124. The controller 142 within the combiner enclosure 114 may discharge the link 124. In
some embodiments, restart may be allowed only upon human inspection and intervention.
Having a centralized, possibly redundant, arc fault detection and anti-islanding may lower the
overall cost per unit and increase the overall safety of the single phase power generation
system 100.
illustrates an embodiment single phase power generation system 200 similar
to the single phase power generation system 100 illustrated in with the addition of
multiple PVs 108A, 108B, and 108C and multiple PCUs 102A, 102B, and 102C. Phase A
132 of single phase power generation system 200 may comprise a set of PVs such as 108A,
108B, and 108C and PCUs 102A, 102B, and 102C. While discussed in relation to three PVs
108A, 108B, and 108C and three PCUs 102A, 102B, and 102C, the power generation system
200 need not be limited to three PV and PCU pairs, and for additional power capacity, an
unlimited number of PV plus PCU sets may be added. Each PCU 102A, 102B, and 102C may
be similar to the PCU 102 discussed above with reference to Each PCU 102A, 102B,
and 102C may comprise a DC to DC converter 104A, 104B, and 104C, a unipolar power
converter 106A, 106B, and 106C, and a controller 107A, l07B, and l07C, respectively. Each
PV 108A, 108B, and 108C, may be connected to the DC to DC converter 104A, 104B, or
104C of its respective PCU 102A, 102B or 102C by lines 110A, 110B, 110C, 112A, 112B,
and 112C, respectively.
Each PCU 102A, 102B, and 102C may be electrically connected to a combiner
enclosure 114 by three lines: a positive fixed voltage DC line l16A, 116B, and l16C, a
negative fixed voltage DC line 118A, 118B, and 118C, and a unipolar power line 120A,
120B, and 120C. All common lines may be electrically connected inside the combiner
enclosure 114. Each positive fixed voltage DC line 116A, 116B, and 116C may be connected
in parallel together. Each negative fixed voltage DC line 118A, 118B, and 118C may be
connected in parallel together. In this manner all positive fixed voltage DC lines l16A, 116B,
and 116C connected in parallel and all negative fixed voltage DC lines 118A, 118B, and
118C may form the link 124. The controllers 107A, 107B, and 107C of each PCU 102A,
102B, and 102C may contain a communication module to inject communication signals into
the link 124 or receive communication signals from the link 124.
In an alternative embodiment, only one PCU 102A of the string of PCUs 102A,
102B, and 102C may be physically connected to the combiner enclosure 114. The combiner
enclosure 114 may be a single unit. However, it may be desirable or required by code or
regulation to keep the DC (116A, 116B, l16C, 118A, 118B, and 118C) and unipolar power
lines (120A, 120B, and 120C) separate. In an alternative embodiment, the DC lines l16A,
116B, 116C, 118A, 118B, and 118C may go into one enclosure and the unipolar power lines
120A, 120B, and 120C into another enclosure. In an embodiment, the number of PCUs in
parallel may be Limited, for example not to exceed fifteen PCUs in parallel due to wire
limitations, and additional plant-level power capacity may be added by another set of PVs
plus PCUs connected in parallel to the combiner enclosure 114. In another embodiment,
various subset collections of the plant's DC lines may be separated to avoid a single-point
failure, such that substantially the same number of modules may be electrically connected in
each phase in a single group of DC lines and each pair of DC lines may be connected to a
separate storage device.
As discussed above with reference to FIG . I, the link 124 may be connected to a
capacitor C1 128. The capacitor C1 128 may be a large capacitor or any other energy storage
device, such as a bidirectional battery charger. The capacitor C1 128 may absorb transients,
for example 120Hz artifacts, that may occur. The capacitor C1 128 may be a low frequency
capacitor of a few hundred microfarads, such as an electrolytic capacitor. Output A may be
the output of the unipolar power lines 120A, 120B, and 120C connected in parallel, which
may be a single phase signal approximating a desired voltage waveform and frequency, offset
from the ground electrical potential such that the voltage output signal may be always
positive, thus "unipolar." Output Vo may be the DC output of the link 124.
A controller 142 within the combiner enclosure 114 may monitor the link 124 via
lines A and B, respectively. Controller 142 may contain a programmable controller or
processor 144, a memory 146, and a communication module 148. The programmable
controller 144 may allow the controller 142 to perform logic operations, perform control the
operations, perform monitoring operations, and perform communication operations in
response to information stored in the memory 146. The lines A, B, and C may be coupled to
the programmable controller 144 such that signals from the programmable controller 144
may be sent or received via the lines A, B, and C. The controller 142 may control the
operation of relay 126 via control line C. As an example, relay 126 may be a single
MOSFET, though any known type of technology capable of performing a switching function,
including relays, transistors, bi-polar transistors, insulated-gate bipolar transistors (JGBTs),
silicon carbide or gallium nitride transistors, thyristors, series connected MOSFETs, thyristor
emulators, and diodes in series with IGBTs may be used. The controller 142 may contain a
communication module 148 coupled to the programmable controller 144 to inject
communication signals into the link 124 or receive communication signals from the link 124
via lines A or B. In this manner, controllers 107A, 107B, and 107C of the PCUs 102A, 102B,
and 102C may communicate with the controller 142 of the combiner enclosure 114 and with
each other. Communication between the controllers 107A, 107B, l07C, and 142 may include
reporting power provided, PV 108A, 108B, and/or 108C voltage or current, status of the
unipolar power converters 106A, 106B, and/or 106C, and receiving commands to enable or
disable the unipolar power converters 106A, 106B, and/or 106C.
The controller 142 may have anti-islanding capabilities and may detect arc faults on
the Link 124 by monitoring line A and/or B. In operation, if an arc fault is detected on the
link 124, the unipolar power lines 120A, 120B, and 120C may be disconnected by opening
the relay 126. The controllers 107A, 107B, and/or 107C in the PCUs 102A, 102B, and/or
102C may detect the disconnection of the unipolar power Lines 120A, 120B, and/or 120C,
and may stop the DC to DC converters 104A, 104B, and/or 104C, and may disconnect the
PCUs 102A, 102B, and/or 102C from the link 124. The controller 142 within the combiner
enclosure l 14 may discharge the link 124. In some embodiments restart may be allowed only
upon human inspection and intervention. Having a centralized, possibly redundant, arc fault
detection and anti-islanding may lower the overall cost per unit and increase the overall
safety of the single phase power generation system 200.
illustrates a two phase power generation system 300A comprised of Phase
A 132 discussed above with reference to combined with another PV 108D and PCU
l02D set, herein denominated Phase B 134. Phase B 134 may be comprised of a PV 1080
connected to the PCU 102D by lines 110D and 112D. PCU 102D may be comprised of a DC
to DC converter 104D, a unipolar power converter 106D, and a controller 107D. The PV
108D and PCU 102D of Phase B 134 may operate in a manner similar to that of Phase A 132
discussed above with reference to
Each PCU 102 and 102D may be electrically connected to a combiner enclosure
114 by three lines: a positive fixed voltage DC line 116 and l16B, a negative fixed voltage
DC line 118 and l18B, and a unipolar power Line 120 and 120D. The positive fixed voltage
DC lines 116 and 1160 may be connected together. Each negative fixed voltage DC line 118
and 118D may be connected together. In this manner all positive fixed voltage DC lines 116
and 116D connected together and all negative fixed voltage DC lines 118 and 118D
connected together may form the link 124. The controllers 107 and 107D of each PCU 102
and 102D may contain a communication module to inject communication signals into the link
124 or receive communication signals from the link 124.
As discussed above with reference to the link 124 may be connected to a
capacitor C1 128. The capacitor C1 128 may be a large capacitor or any other energy storage
device, such as a bidirectional battery charger. The capacitor C1 128 may absorb transients,
for example 120Hz artifacts, that may occur. The capacitor C1 128 may be a low frequency
capacitor of a few hundred microfarads, such as an electrolytic capacitor. Output A may be
the output of the unipolar power line 120, which may be a single phase signal approximating
a desired voltage waveform and frequency, offset from the ground electrical potential such
that the voltage output signal may be always positive, thus "unipolar." Output B may be the
output of the unipolar power line 120D, which may be a single phase signal approximating a
desired voltage waveform and frequency, offset from the ground electrical potential such that
the voltage output signal may be always positive, thus "unipolar." Output Vo may be the DC
output of the link 124.
A controller 142 within the combiner enclosure 114 may monitor the l ink 124 via
lines A and B, as discussed above with reference to Controller 142 may contain a
programmable controller or processor 144, a memory 146, and a communication module 148.
The programmable controller 144 may allow the controller 142 to perform logic operations,
perform control the operations, perform monitoring operations, and perform communication
operations in response to information stored in the memory 146. The lines A, B, C, and D
may be coupled to the programmable controller 144 such that signals from the programmable
controller 144 may be sent or received via the lines A, B, C, and D. The controller 142 may
control the operation of relay 126 via control line C and the operation of relay 126D via
control line D. As an example, relays 126 and 126D may be a single MOSFET, though any
known type of technology capable of performing a switching function, including relays,
transistors, bi-polar transistors, insulated-gate bipolar transistors (IGBTs), silicon carbide or
gallium nitride transistors, thyristors, series connected MOSFETs, thyristor emulators, and
diodes in series with IGBTs may be used. The controller 142 may contain a communication
module 148 coupled to the programmable controller 144 to inject communication signals into
the Link 124 or receive communication signals from the link 124 via lines A or B. In this
manner, controllers 107 and 107D of the PCUs 102 and 102D may communicate with the
controller 142 of the combiner enclosure 114 and with each other. Communication between
the controllers 107, 1070, and 142 may include reporting power provided, PV 108 and/or
108D voltage or current, status of the unipolar power converters 106 and/or 106D, and
receiving commands to enable or disable the unipolar power converters 106 and/or 106D.
The controller 142 may have anti-islanding capabilities and may detect arc faults on
the link 124 by monitoring line A and/or B. In operation, if an arc fault is detected on the link
124, the unipolar power lines 120 and/or 120D may be disconnected by opening the relay 126
and/or relay 126D. The controller 107 in the PCU 102 may detect the disconnection of the
unipolar power line 120, and may stop the DC to DC converter 104, and may disconnect the
PCU 102 from the link 124. The controller 107D in the PCU 102D may detect the
disconnection of the unipolar power line l20D, and may stop the DC to DC converter l04D,
and may disconnect the PCU 1020 from the link 124. The controller 142 within the combiner
enclosure l 14 may discharge the link 124. In some embodiments restart may be allowed only
upon human inspection and intervention. Having a centralized, possibly redundant, arc fault
detection and anti-islanding may lower the overall cost per unit and increase the overall
safety of the single phase power generation system 300.
illustrates a two phase power generation system 300B similar to two phase
power generation system 300A discussed above with reference to , except that rather
than two PVs 108 and 108D each connected to a PCU 102 and 102D, respectively, a single
PV 108 is associated with electronics interfaces for the two phases, Phase A 132 and Phase B
134. In the two phase power generation system 300B, Phase A 132 may be comprised of PV
108 connected to the PCU 102 by lines 110 and 112 and Phase B 134 may be comprised of
PV 108 connected to the PCU 102D by lines 110D and 112D. The two phase power
generation system 3008 may operate in a manner similar to two phase power generation
system 300A discussed above with reference to .
illustrates a three phase power generation system 400A that may be
comprised of Phase A 132 and Phase B 134 discussed above with reference to ,
combined with another PV 108E and PCU 102E set, herein denominated Phase C 136. Phase
C 136 may be comprised of a PV 108E connected to the PCU 102E by lines 110E and 112E.
PCU 102E may be comprised of a DC to DC converter 104E, a unipolar power converter
106E, and a controller 107E. The PV 108E and PCU 102E of Phase C 134 may operate in a
manner similar to that of Phase A 1 32 and Phase B 134 discussed above with reference to
.
Each PCU 102, 102D, and 102E may be electrically connected to a combiner
enclosure 114 by three lines: a positive fixed voltage DC line 116, l16D, and 116E, a
negative fixed voltage DC line 118, 118D, and 118E, and a unipolar power line 120, 120D,
and 120E. The positive fixed voltage DC lines 116, l16D, and 116E may be connected
together in parallel. Each negative fixed voltage DC line 118, 118D, and 118E may be
connected together in parallel. In this manner all positive fixed voltage DC lines 116, 116D,
116E connected together and all negative fixed voltage DC lines 118, l18D, and 118E
connected together may form the link 124. The controllers 107, 107D, and 107E of each PCU
102, 102D, and 102E may contain a communication module to inject communication signals
into the link 124 or receive communication signals from the link 124.
As discussed above with reference to FIG. l , the link 124 may be connected to a
capacitor C1 128. The capacitor C1 128 may be a large capacitor or any other energy storage
device, such as a bidirectional battery charger. The capacitor C1 128 may absorb transients,
for example 120Hz artifacts, that may occur. The capacitor C1 128 may be a low frequency
capacitor of a few hundred microfarads, such as an electrolytic capacitor.
Output A may be the output of the unipolar power line 120, which may be a single
phase signal approximating a desired voltage waveform and frequency, offset from the
ground electrical potential such that the voltage output signal may be always positive, thus
"unipolar." Output B may be the output of the unipolar power line 120D, which may be a
single phase signal approximating a desired voltage waveform and frequency, offset from the
ground electrical potential such that the voltage output signal may be always positive, thus
"unipolar." Output C may be the output of the unipolar power line 120E, which may be a
single phase signal approximating a desired voltage waveform and frequency, offset from the
ground electrical potential such that the voltage output signal may be always positive, thus
''unipolar." Output Vo may be the DC output of the link 124.
A controller 142 within the combiner enclosure 114 may monitor the link 124 via
lines A and B, as discussed above with reference to The controller 142 may contain a
programmable controller or processor 144, a memory 146, and a communication module 148.
The programmable controller 144 may allow the controller 142 to perform logic operations,
perform control the operations, perform monitoring operations, and perform communication
operations in response to information stored in the memory 146. The lines A, B, C, D, and E
may be coupled to the programmable controller 144 such that signals from the programmable
controller 144 may be sent or received via the lines A, B, C, D, and E. The controller 142
may control the operation of relay 126 via control line C, the operation of relay 1260 via
control line D, and the operation of relay 126E via control line E. As an example, relays 126,
126D, and 126E may be a single MOSFET , though any known type of technology capable of
performing a switching function, including relays, transistors, bi-polar transistors, insulated-
gate bipolar transistors (IGBTs), silicon carbide or gallium nitride transistors, thyristors,
series connected MOSFETs, thyristor emulators, and diodes in series with IGBTs may be
used. The controller 142 may contain a communication module 148 coupled to the
programmable controller 144 to inject communication signals into the link 124 or receive
communication signals from the link 124 via lines A or B. In this manner, controllers 107,
1070, and 107E of the PCUs 102, 102D, and 102E may communicate with the controller 142
of the combiner enclosure 1 14 and with each other. Communication between the controllers
107, 107D, 107E, and 142 may include reporting power provided, PV 108, 108D, and/or
108E voltage or current, status of the unipolar power converters 106, 1060, and/or 106E, and
receiving commands to enable or disable the unipolar power converters 106, 106D, and/or
106E.
The controller 142 may have anti-islanding capabilities and may detect arc faults on
the link 124 by monitoring line A and/or B. In operation, if an arc fault is detected on the link
124, the unipolar power lines 120, 1200, and/or 120E may be disconnected by opening the
relay 126, 126D, and/or relay 126E. The controller 107 in the PCU 102 may detect the
disconnection of the unipolar power line 120, and may stop the DC to DC converter 104, and
may disconnect the PCU 102 from the link 124. The controller 107D in the PCU 102D may
detect the disconnection of the unipolar power line 1200, and may stop the DC to DC
converter 1040, and may disconnect the PCU 102D from the link 124. The controller 107E in
the PCU 102E may detect the disconnection of the unipolar power line 120E, and may stop
the DC to DC converter 104£, and may disconnect the PCU 102E from the link 124. The
controller 142 within the combiner enclosure 114 may discharge the link 124. In some
embodiments restart may be allowed only upon human inspection and intervention. Having a
centralized, possibly redundant, arc fault detection and anti-islanding may lower the overall
cost per unit and increase the overall safety of the single phase power generation system 400.
The output of DC-DC converters 104, 1040, and 104E may be electrically
connected in parallel and may function to set a target voltage to regulate their respective PVs,
108, 108D, and 108E as the DC-DC converter input voltage. As a result each DC-DC
converter 104, 104D, and 104E may operate at constant power if its respective PV 108,
108D, and 108E insolation and temperature conditions do not change. The output of the
DC-DC converters 104, 104D, and 104E provide the input power to the unipolar power
converters 106, 106D, and 106E. If for any reason, there may be more input power to the
unipolar power converters 106, 106D, and 106E than may be desirable to deliver on the
outputs (for instance safety limit for output FETs or plant level limitation), then all associated
DC-DC converters 104, 104D, and 104E may limit their output power. In an embodiment
this may be done by controlling the DC-DC converters 104, 104D, and 104E so as to limit the
link 124 voltage Vlink to a value corresponding to the maximum power needed from the
plant.
A three phase output may be output from the combiner enclosure 114. The
minimum voltage may be offset by a voltage value Voffset, above the negative voltage at
lines 112, 112D, 112E, 118, 118D, and 118E. In some embodiments Voffset may be ten
volts. A neutral voltage point may be connected to the corresponding neutral line of a grid
system. Likewise Phase A terminal, Phase B, and Phase C output from combiner enclosure
114 may be connected to corresponding phase lines of the grid.
illustrates a three phase power generation system 400B similar to three
phase power generation system 400A discussed above with reference to , except that
rather than three PVs 108, 108D, and 108E each connected to a PCU 102, 102D, and 102E,
respectively, a single PV 108 is associated with electronics interfaces for the three phases,
Phase A 132, Phase B 134, and Phase C 136. In the three phase power generation system
400B, Phase A 132 may be comprised of PV 108 connected to the PCU 102 by lines 110 and
112, Phase B 134 may be comprised of PV 108 connected to the PCU 102D by lines 110D
and 112D, and Phase C 136 may be comprised of PV 108 connected to the PCU 102E by
lines 110E and 112E. The three phase power generation system 400B may operate in a
manner similar to three phase power generation system 400A discussed above with reference
to .
illustrates the components of an embodiment PCU 102 as discussed above
with reference to Capacitors 502 and 536, a coil 504, and switches 506 and 508 may
form the boost-type DC to DC converter 104. Line 110 may be connected to a positive input
terminal 526 of the DC to DC converter 104 and line 112 may be connected to a
negative input terminal 528 of the DC to DC converter 104. An input terminal of the
capacitor 502 and an input terminal of the coil 504 may be connected to the positive input
terminal 526. An output terminal of the coil 504 may be connected to an input terminal of
switch 508 and an input terminal of switch 506. Switches 506 and 508 may be single
MOSFETs, though any known type of technology capable of performing a switching
function, including relays, transistors, bi-polar transistors, insulated-gate bipolar transistors
(IGBTs), silicon carbide or gallium nitride transistors, thyristors, series connected MOSFETs,
thyristor emulators, and diodes in series with IGBTs may be used. Additionally, switches 506
and 508 may be different types of switches. In an alternative embodiment, switch 506 may be
a diode though this example configuration may result in a lower component cost it may also
result in some sacrifice in efficiency.
An output terminal of switch 508 may be connected to an input terminal of capacitor
536 and to positive DC output terminal 530. Positive DC output terminal 530 may be
connected to positive fixed voltage DC line 116. The capacitor 536 may be a high frequency
capacitor, for example a few microfarad capacitor and may filter high frequency switching
artifacts. The output terminal of capacitor 502, output terminal of switch 506, and the output
terminal of capacitor 536 may be connected to the negative input terminal 528. Additionally,
the output terminal of capacitor 502, output terminal of switch 506, the output terminal of
capacitor 536, and the negative input terminal 528 may be connected to negative DC output
terminal 532. The negative DC output terminal 532 may be connected to negative fixed
voltage DC line 118.
Coils 510 and 516, switches 512 and 514, and a capacitor 518 may form the
unipolar power converter 106. An input terminal of coil 510 may be connected to the input
terminal of capacitor 536, the output terminal of switch 508, and the positive DC output
terminal 530. An output terminal of coil 510 may be connected to an input terminal of switch
512. Switch 512 may be a single MOSFET, though any known type of technology capable of
performing a switching function, including relays, transistors, bi-polar transistors,
insulated-gate bipolar transistors (IGBTs), silicon carbide or gallium nitride transistors,
thyristors, series connected MOSFETs, thyristor emulators, and diodes in series with TGBTs
may be used. An output terminal of switch 512 may be connected to an input terminal of coil
516 and an output terminal of switch 514. Switch 514 may be a single MOSFET, though any
known type of technology capable of performing a switching function, including relays,
transistors, bi-polar transistors, insulated-gate bipolar transistors (IGBTs), silicon carbide or
gallium nitride transistors, thyristors, series connected MOSFETs, thyristor emulators, and
diodes in series with IGBTs may be used. In an alternative embodiment, switch 514 may be a
diode. An output terminal of switch 512 and an output terminal of switch 514 may be
connected together to form a single output terminal. Connected together in this manner,
switch 512 and 514 may form a half bridge circuit. The output terminal of switch 512 and
output terminal of switch 514 may be connected together to form a single output terminal
which may be connected to an input terminal of coil 516.
An output terminal of coil 516 may be connected to an input terminal of capacitor
518 and to unipolar power output terminal 534. Unipolar power output terminal 534 may be
connected to unipolar power line 120. An output terminal of capacitor 518 may be connected
to an input terminal of switch 514, the output terminal of capacitor 502, the output terminal of
switch 506, the output terminal of capacitor 536, the negative input terminal 528, and to
negative DC output terminal 532. Capacitor 518 may enable high frequency decoupling of
the unipolar power converter 106 from a power system to which the unipolar power converter
106 may be coupled.
The controller 107 may provide control signals to the control gates of switches 506,
508, 512, and 514 via control lines A, B, C, and D, respectively. The controller 107 may
comprise a plurality of output terminals, each of which may be operated independently.
Control lines A, B, C, and D may be connected to the control gates of switches 506, 508, 512,
and 514, respectively. Controller 107 may contain a programmable controller or processor
520, a memory 522, and a communication module 524. The programmable controller 520
may perform logic operations, perform control operations, perform monitoring operations,
and perform communication operations in response to information stored in the memory 522.
The lines A, B, C, and D may be coupled to the programmable controller 520 such that
signals from the programmable controller 520 may be sent or received via the lines A, B, C,
and D. The lines A, B, C, and D may be coupled to the programmable controller 520 such
that signals from the programmable controller 520 control the operation of switches 506, 508,
512, and 514, respectively. In an embodiment, the programmable controller 520 may control
the operation of switches 506 and 508 such that the DC to DC converter 104 has a high
switching frequency, for example 30 KHz. Communication module 524 may enable the
programmable controller 520 to send and receive information via lines connected to the
positive DC output terminal 530, the negative DC output terminal 532, and the unipolar
power output terminal 534, and/or via other communication channels (e.g., via wireless or
wired network connections).
illustrates the phase relationships between the three phases A 602, B 604, and
C 606. illustrates the phase relationship for a two phase system, for example 180
degrees, between two phases A 702 and B 704.
illustrates an example of the result of the conversion of a pulse width
modulated pulse which may be translated into a pulse amplitude modulated (PAM) current
pulse by the PCU 102 as discussed above with reference to The short duration
roughly rectangular voltage pulses 802 may represent the voltage on the drain side of switch
506. The pulse width 808 may approximate the pulse width of the signal from the controller
107 via line A and the period 810 may be the switching period of the PCU 102. The rounded
half wave rectified sine wave 804 may be the output of the PCU 102 at unipolar power output
terminal 534 to line A, depending on the status of the control signals from controller 107 and
the status of the switches 512 and 514. The capacitor 536 may act with the coils 510 and 516
and capacitor 518 as a reconstruction filter to create the rounded half wave rectified sine
wave 804. The triangle waveform 806 illustrates the variation of the current which may occur
through a PV 108 connected to the PCU 102 during the same time period, and shows the
effect the coil 504 and capacitor 536 may have in maintaining a relatively constant PV 108
current, independent of the relatively large pulse width modulated current pulses created by
the reconstruction filter.
illustrates the relationship between the individual power curves of a group of
five PCUs connected in parallel in a single phase power generation system and the total
power curve of the five PCU single phase power generation system for a given period of
time. While discussed in terms of a five PCU single phase power generation system, an
unlimited number of PCU's may be connected in parallel. As discussed above, a PV may be
connected to a PCU, and an unlimited number of PCUs may be connected in parallel, such
that the outputs of each PCU may be joined in parallel to comprise a single phase of power.
As solar light begins to be incident upon the PVs, the power available from each PV may be
less than that PV's maximum power. During a low power condition (such as during the
morning sunrise), each unipolar power converter of the group of five PCU's may operate at an
inefficient condition if all unipolar power converters were placed in operation at once. To
improve efficiency, at a first period of time, from time 914 to 916, a first PCU's unipolar
power converter may be activated, thereby providing power to the load per that first PCU's
power curve 902. As the DC-DC bus voltage (thereby power available) continues to
increase, for a time period 916 to 918, a second PCU 's unipolar power converter may be
enabled, also increasing its power as illustrated by power curve 904 as the DC-DC bus
voltage, hence power available, increases. Total power to the load 924 may be the combined
power of the first and second PCU's unipolar power converters for the second period of time,
from time 916 to 918. Subsequent PCU 's may be activated as power increases. A third PCU's
unipolar power converter may be activated in a third time period from time 918 to 920,
thereby providing its power illustrated by power curve 906. A fourth PCU 's unipolar power
converter may be activated in a fourth time period from time 920 to 922, thereby providing
its power illustrated by power curve 908. After time 922 a fifth PCU's unipolar power
converter may be activated, thereby providing its power illustrated by power curve 910.
In an embodiment each subsequent PCU's unipolar power converter may be enabled
at a certain DC-DC voltage before the previously enabled PCU's unipolar power converter
has reached its maximum efficiency condition 912. As illustrated in all units may
have the same point of maximum efficiency 912, though in operation a given PCU's unipolar
power converter may have a different maximum efficiency point than another PCU's unipolar
power converter. As the DC-DC voltage continues to increase, more and more PCU 's
unipolar power converters may be enabled, each before a previous such unit has attained its
maximum efficiency condition in order to provide a smooth transition. Correspondingly, as
each PCU's unipolar power converter is enabled, the total (combined) power for the system
may increase, as illustrated by the individual power curves 902, 904, 906, 908, and 910 at
each corresponding transition (trigger) point 914, 916, 918, 920, and 922 respectively,
reflected in the total power curve 924.
In an alternative embodiment each PCU's unipolar power converter may be
configured to begin operation at a unique DC-DC bus voltage value (trigger value), thereby
creating the staggered enablement effect illustrated in In another alternative
embodiment, the unipolar power converter of the PCU physically closest to a combiner
enclosure may be the first to be enabled, then the next closest and so on. This strategy may
provide an efficiency improvement by minimizing the connecting wire lengths, hence
resistive losses. In a still further alternative embodiment, a control strategy may rotate the
assigned trigger voltages amongst the PCU's such that no one unipolar power converter may
be operated more overall hours than any other unipolar power converter. In this manner,
damage to a unipolar power converter resulting from more use than other unipolar power
converters may be avoided. In the various embodiments, the assigned trigger points may be
changed at any interval, such as each operating day.
The embodiments illustrated in may also be employed when full insolation
may be available, but when the load, for example a grid, may not demand the entire available
output. As the load demand decreases the number of activated unipolar power converters
may be decreased according to a predetermined schedule. As the load demand may later
increase, additional unipolar power converters may be re-enabled. As an example,
decreasing approach may be used at the end of the day as solar insolation decreases during
sun set.
The maximum power needed from the plant may be determined by the curve 924
illustrated in FIG 9. This may correspond to operating the boost in maximum voltage mode:
if the link voltage Vlink is greater than the target limit, the MPPT target may be disabled and
the unipolar power converter input power may be reduced by some amount (the input voltage
target is increased such that the panel current and power decreases). If later the DC Mink 109
voltage Vlink goes lower, then the input target voltage to the unipolar power converter may
be increased gradually until it reaches MPP voltage and the MPPT operation may resume.
In an alternative embodiment, power may be demanded of the system in excess of
that provided by controlling all available PCU's and their associated unipolar power
converters to their maximum efficiency condition. In response the unipolar power converters
may be controlled to a higher power configuration at the sacrifice of some efficiency until
such time as all unipolar power converters reach their predetermined maximum power
condition. As an example, the maximum efficiency point for the PVs connected to the PCUs
may be at approximately 150 watts, and the maximum power allowed may be 240 watts. The
maximum power may be the maximum the electronics can support, or it may be a
predetermined value beyond which damage may result.
In an embodiment, if the unipolar power converter of a given PCU is not working
(for example, is stopped due to a fault), the incoming power from that PCU 's corresponding
DC-DC converter and the other PCUs' DC-DC converters may be provided to the other
unipolar power converters of the other PCUs of the same phase, enabled according to their
assigned trigger voltage.
In the various embodiments less than all DC-DC converters may be connected in
parallel. In the various embodiments unipolar power converters may be active at any given
moment. As the power requirement of a load, for example a power grid, may be less than the
full power available from the plant, or the input power available may be enabled below that
required for peak output power, some portion of unipolar power converters may not be
enabled, thereby allowing each operating unipolar power converter to operate at its own peak
efficiency.
illustrates an embodiment method 1000 for generating a positive DC
voltage, a negative DC voltage, and a unipolar power output with a PCU. As an example the
PCU may be the PCU 102 described above with reference to FIGs. 1 and 5. The method
1000 may be implemented by the controller 107 of a PCU 102. At block 1002 the controller
107 may open and close DC to DC converter switches to generate a positive DC voltage and
a negative DC voltage. As an example, the controller 107 may open and close switches 506
and 508 of the DC to DC converter 104 to generate a positive DC voltage and a negative DC
voltage. At block 1004 the controller 107 may open and close unipolar power converter
switches to generate a unipolar power output. As an example, the controller 107 may open
and close switches 512 and 514 to generate a unipolar power output.
illustrates an embodiment method 1100 for generating a modulated DC
output and an AC output with a PCU. As an example the PCU may be the PCU 102 described
above with reference to FIGs. 1 and 5. The method 1000 may be implemented by the
controller 107 of a PCU 102. At block 1002 the controller 107 may open and close DC to DC
converter switches to generate a modulated DC output. As an example, the controller 107
may open and close switches 506 and 508 of the DC to DC converter 104 to generate a
modulated DC output. At block 1104 the controller 107 may open and close unipolar power
converter switches to convert the modulated DC output to an AC output. As an example, the
controller 107 may open and close switches 512 and 514 to convert the modulated DC output
to an AC output.
illustrates an embodiment method 1200 for operating a power generation
system comprising a plurality of PCUs connected in parallel. As an example, the power
generation system may be the power generation system 200 described above with reference
to The method 1100 may be implemented by the controller 142 of the combiner
enclosure 114. At block 1202 the controller 142 may activate a first PCU. As an example
the controller 142 may activate PCU 102A via a communication signal on lines 116A and/or
118A. At determination block 1204 the controller 142 may monitor the output of the first
PCU to determine if the output of the first PCU has reached a trigger value. A trigger value
may be any value, such as a voltage value or a maximum power level. If the trigger value is
not reached (i.e., determination block 1204 = "No"), the controller 142 may continue to
monitor the output of the first PCU. lf the trigger value is reached (i.e., determination block
1204 = "Yes"), at block 1206 the controller 142 may activate a second PCU. As an example,
the controller 142 may activate a second PCU 102B via a communication signal on lines
116B and/or 118B.
FIG . 13 illustrates an embodiment method 1300 for controlling the operation of a
combiner enclosure to prevent the flow of unipolar power to a unipolar power output As an
example, the combiner enclosure may be the combiner enclosure 114 of power generation
system 100 described above with reference to The method 1300 may be implemented
by the controller 142 of the combiner enclosure 114. At block 1302 the controller 142 may
open a relay to prevent the flow of unipolar power to the unipolar power output. As an
example, controller 142 may open relay 126 via a control signal on line C. At block 1304 the
controller 142 may send a signal to the PCU. As an example, the controller 142 may send a
signal to the PCU 102 via lines 116 and/or 118. As an example, the signal from the controller
142 to the PCU 102 may be an indication to stop the generation of unipolar power at the PCU
102. At block 1306 the controller 142 may receive a signal from the PCU 102. As an
example, the controller 142 may receive a signal from the PCU 102 via lines 116 and/or 118.
As an example, the signal from the PCU 102 may be an indication that the PCU 102 has
stopped generating unipolar power.
The various embodiments described herein may be useful for controlling any source
of direct current and converting the direct current to three phase alternating current. Examples
of direct current sources include solar panel, wind turbine, battery, geothermal, tidal,
hydroelectric, thermoelectric and piezoelectric power systems. For the purpose of discussion,
the example of a solar system embodiment is used as an example for describing the
functioning and capabilities of the various embodiments. However, one skilled in the art
would recognize that the circuits and processes described herein may be applied to other
direct current sources as well. Accordingly, the scope of the claims should not be limited to
solar power applications except as expressly recited in the claims.
The foregoing method descriptions and the process flow diagrams are provided
merely as illustrative examples and are not intended to require or imply that the steps of the
various aspects must be performed in the order presented. As will be appreciated by one of
skill in the art the order of steps in the foregoing aspects may be performed in any order.
Words such as "thereafter," "then," "next,” etc. are not intended to limit the order of the
steps; these words arc simply used to guide the reader through the description of the methods.
Further, any reference to claim elements in the singular, for example, using the articles "a,"
"an" or "the" is not to be construed as limiting the element to the singular.
The various illustrative logical blocks, modules, circuits, and algorithm steps
described in connection with the aspects disclosed herein may be implemented as electronic
hardware, computer software, or combinations of both . To clearly illustrate this
interchangeability of hardware and software, various illustrative components, blocks,
modules, circuits, and steps have been described above generally in terms of their
functionality. Whether such functionality is implemented as hardware or software depends
upon the particular application and design constraints imposed on the overall system. Skilled
artisans may implement the described functionality in varying ways for each particular
application, but such implementation decisions should not be interpreted as causing a
departure from the scope of the present invention.
The hardware used to implement the various illustrative logics, logical blocks,
modules, and circuits described in connection with the aspects disclosed herein may be
implemented or performed with a general purpose processor, a digital signal processor (DSP),
an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or
other programmable logic device, discrete gate or transistor logic, discrete hardware
components, or any combination thereof designed to perform the functions described herein.
A general-purpose processor may be a microprocessor , but, in the alternative, the processor
may be any conventional processor, controller, programmable controller, microcontroller, or
state machine. A processor may also be implemented as a combination of computing devices,
e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or
more microprocessors in conjunction with a DSP core, or any other such configuration.
Alternatively, some steps or methods may be performed by circuitry that is specific to a given
function.
In one or more exemplary aspects, the functions described may be implemented in
hardware, software, firmware, programmable logic arrays, or any combination thereof. If
implemented in software, the functions may be stored on or transmitted over as one or more
instructions or code on a computer-readable medium. The steps of a method or algorithm
disclosed herein may be embodied in a processor-executable software module executed
which may reside on a tangible non-transitory computer-readable medium or processor-
readable medium. Non-transitory computer-readable and processor-readable media may be
any available media that may be accessed by a computer or processor. By way of example,
and not limitation, such non-transitory computer-readable media may comprise RAM, ROM,
EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic
storage devices, or any other medium that may be used to carry or store desired program code
in the form of instructions or data structures and that may be accessed by a computer. Disk
and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile
disc (DVD), floppy disk, and blu-ray disc where disks usually reproduce data magnetically,
while discs reproduce data optically with lasers. Combinations of the above should also be
included within the scope of computer-readable media. Additionally, the operations of a
method or algorithm may reside as one or any combination or set of codes and/or instructions
on a non-transitory processor-readable medium and/or computer-readable medium, which
may be incorporated into a computer program product.
The preceding description of the disclosed embodiments is provided to enable any
person skilled in the art to make or use the present invention. Various modifications to these
embodiments will be readily apparent to those skilled in the art, and the generic principles
defined herein may be applied to other embodiments without departing from the spirit or
scope of the invention. Thus, the present invention is not intended to be limited to the
embodiments shown herein but is to be accorded the widest scope consistent with the
following claims and the principles and novel features disclosed herein.
Claims (12)
1. An apparatus comprising a power converter unit, wherein the power converter unit comprises: a direct current ("DC") to DC converter comprising: a positive input terminal; a negative input terminal; a first capacitor, wherein an input terminal of the first capacitor is connected to the positive input terminal and an output terminal of the first capacitor is connected to the negative input terminal; a first coil, wherein an input terminal of the first coil is connected to the input terminal of the first capacitor; a first switch, wherein an input terminal of the first switch is connected to an output terminal of the first coil and an output terminal of the first switch is connected to the negative input terminal; a second switch, wherein an input terminal of the second switch is connected to the output terminal of the first coil; a second capacitor, wherein an input terminal of the second capacitor is connected to an output terminal of the second switch and an output terminal of the second capacitor is connected to the negative input terminal; a positive DC output terminal connected to the input terminal of the second capacitor; and a negative DC output terminal connected to the output terminal of the second capacitor; a unipolar power converter comprising: a second coil, wherein an input terminal of the second coil is connected to the input terminal of the second capacitor; a third switch, wherein an input terminal of the third switch is connected to an output terminal of the second coil; a fourth switch, wherein an input terminal of the fourth switch is connected to the output terminal of the second capacitor and an output terminal of the fourth switch is connected to an output terminal of the third switch; a third coil, wherein an input terminal of the third coil is connected to the output terminal of the third switch and the output terminal of the fourth switch; a third capacitor, wherein an input terminal of the third capacitor is connected to an output terminal of the third coil and an output terminal of the third capacitor is connected to the input terminal of the fourth switch; and a unipolar power output terminal connected to the input terminal of the third capacitor; and a controller coupled to the first, second, third, and fourth switches, wherein the controller is configured to control the operation of each switch to generate a positive DC voltage at the positive DC output terminal, a negative DC voltage at the negative DC output terminal, and a unipolar power output at the unipolar power output terminal.
2. The apparatus of claim 1, wherein the controller is a processor, the power converter unit further comprising a memory coupled to the processor, wherein the processor is configured with processor-executable instructions to perform operations comprising: opening and closing the first and second switches to generate the positive DC voltage at the positive DC output terminal and a negative DC voltage at the negative DC output terminal; and opening and closing the third and fourth switch to generate a unipolar power output at the unipolar power output terminal.
3. The apparatus of claim 1 or claim 2, the controller is a processor, the power converter unit further comprising a memory coupled to the processor, wherein the processor is configured with processor-executable instructions to perform operations comprising: opening and closing the first and second switches to generate a modulated DC output; and opening and closing the third and fourth switches to convert the modulated DC output into an alternating current ("AC") output at the unipolar power output terminal.
4. The apparatus of any one of claims 1 to 3, wherein the power converter unit is connected to a combiner enclosure that is connected to the positive DC output terminal, the negative DC output terminal, and the unipolar power output terminal.
5. The apparatus of claim 4, wherein the combiner enclosure further comprises: a relay connected configured to prevent flow of unipolar power to the unipolar power output terminal when opened; a memory; and a processor coupled to the memory and the relay, wherein the processor is configured with processor-executable instructions to perform operations comprising opening the relay to prevent the flow of unipolar power to the unipolar power output.
6. The apparatus of claim 4 or claim 5, wherein the combiner enclosure further comprises an energy storage device connected between the positive DC output terminal and the negative DC output terminal.
7. The apparatus of claim 6, wherein the energy storage device is one of a capacitor or a bidirectional battery charger.
8. The apparatus of any one of claims 1 to 7, wherein the positive input terminal and the negative input terminal are connected to a DC source.
9. The apparatus of claim 8, wherein the DC source is a photovoltaic panel.
10. The apparatus of any one of claims 1 to 9, wherein the power converter unit is one of a plurality of power converter units connected in parallel, and wherein the controller is further configured to: activate a first power converter unit of the plurality of power converter units; determine that an output of the first power converter unit has reached a trigger value; and activate a second power converter unit of the plurality of power converter units upon the output of the first power converter unit reaching the trigger value.
11. The apparatus of claim 10, wherein the trigger value is a voltage value.
12. The apparatus of claim 10 or claim 11, wherein the second power converter unit is activated upon the first power converter unit reaching the trigger value without a reduction in the output of the first power converter unit.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US201161562191P | 2011-11-21 | 2011-11-21 | |
US61/562,191 | 2011-11-21 | ||
NZ625048A NZ625048B2 (en) | 2011-11-21 | 2012-11-20 | Single phase inverters cooperatively controlled to provide one, two, or three phase unipolar electricity |
Publications (2)
Publication Number | Publication Date |
---|---|
NZ712076A NZ712076A (en) | 2017-03-31 |
NZ712076B2 true NZ712076B2 (en) | 2017-07-04 |
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