CN109361235A - The alternate Power balance control method of three-phase cascaded H-bridges photovoltaic DC-to-AC converter - Google Patents

The alternate Power balance control method of three-phase cascaded H-bridges photovoltaic DC-to-AC converter Download PDF

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CN109361235A
CN109361235A CN201811254697.XA CN201811254697A CN109361235A CN 109361235 A CN109361235 A CN 109361235A CN 201811254697 A CN201811254697 A CN 201811254697A CN 109361235 A CN109361235 A CN 109361235A
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voltage
phase
bridge unit
actual value
sequence
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CN109361235B (en
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张兴
毛旺
赵涛
胡玉华
王付胜
戴之强
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Hefei University of Technology
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    • H02J3/383—
    • 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
    • H02J3/26—Arrangements for eliminating or reducing asymmetry in polyphase networks
    • H02J3/385—
    • 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
    • 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
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/50—Arrangements for eliminating or reducing asymmetry in polyphase networks

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Abstract

The invention discloses a kind of alternate Power balance control methods of three-phase cascaded H-bridges photovoltaic DC-to-AC converter, and the purpose is to solve the problems, such as that three-phase cascaded H-bridges photovoltaic DC-to-AC converter DC side photovoltaic module input power imbalance causes grid-connected current to distort.This method includes (1) total DC voltage control, for realizing that the total DC voltage of H-bridge unit tracks its total maximum power point voltage and obtains system active current command value；(2) current on line side controls, and can be realized the independent control of watt current and reactive current and generates three-phase inverter modulation wave signal；(3) alternate Power balance control, the actual value of every phase total voltage is set to track its command voltage by voltage between phases adjuster, the regulatory factor for obtaining every phase total voltage corrects inverter modulation wave signal with this, and distributes H-bridge unit output mode accordingly, to realize alternate Power balance control.This method can preferably adapt to various operating conditions, and inhibit alternate power unbalanced in a big way.

Description

The alternate Power balance control method of three-phase cascaded H-bridges photovoltaic DC-to-AC converter
Technical field
The present invention relates to a kind of alternate Power balance control methods of three-phase cascaded H-bridges photovoltaic DC-to-AC converter, belong to cascade connection type light Lie prostrate inverter power Balance route technical field.
Background technique
Parallel network power generation is and environmental-friendly and be concerned since it provides clean energy resource.In face of how to improve photovoltaic System effectiveness reduces the problems such as cost of electricity-generating, cascaded H-bridges multi-electrical level inverter due to its modularization easily expands, system effectiveness height, The advantages such as grid-connected current total harmonic distortion (THD) is small and have become a hot topic of research.In addition, cascaded H-bridges multi-electrical level inverter is each The characteristics of power cell needs independent DC power supply, conforms exactly to photovoltaic module power generation, so that the MPPT of single photovoltaic module Control is possibly realized, and further increases the generating efficiency of system.Therefore, cascaded H-bridges multi-electrical level inverter is in photovoltaic power generation grid-connecting There is unique advantage in.
Although the power cells at different levels of three-phase cascaded H-bridges photovoltaic DC-to-AC converter can be controlled by independent MPPT and improve photovoltaic hair The efficiency of electricity, but be illuminated by the light, the extraneous factors such as temperature and photovoltaic module degree of aging influence, each photovoltaic module is input to inversion The power of device is different, leads to the alternate unbalanced power of three-phase, so that grid-connected current be caused to distort.Therefore, in order to guarantee three-phase grade Join stable operation of the H bridge photovoltaic DC-to-AC converter between intensity of illumination and photovoltaic module under mismatch condition, takes certain alternate Power balance control has engineering significance outstanding.
For this purpose, domestic and foreign scholars have done much in terms of the alternate Power balance control of three-phase cascaded H-bridges photovoltaic DC-to-AC converter Research.Such as IEEE document " Control and modulation scheme for a cascaded H-Bridge in 2012 multi-level converter in large scale photovoltaic systems”Townsend C D, Summers T J, Betz R E, " IEEE Energy Conversion Congress and Exposition ", 2012, Pp.3707-3714 (" control of cascaded H-bridges multi-level converter and modulator approach applied to large-scale photovoltaic system ", " IEEE Energy conversion conference and fair ", 2012 3707-3714 pages) article propose it is a kind of based on fundamental wave zero sequence injection phase Between equalization methods, but this method can only realize alternate Power balance control in linear modulator zone, and Balance route range is smaller.
Such as IEEE document " Power Balance of Cascaded H-Bridge Multilevel in 2016 Converters for Large-Scale Photovoltaic Integration”Y Yu,G Konstantinou,B Hredzak and V G.Agelidis, " IEEE Transactions on Power Electronics ", 2016,31 (1), 292-303 (" the cascaded H-bridges multi-level converter Power balance control applied to large-scale photovoltaic system ", " IEEE journal-electricity Power electronic journal " the 1st 292-303 pages of the phase of volume 31 in 2016) it proposes and a kind of third-harmonic zero-sequence voltage is added based on fundamental wave zero sequence Alternate equalization methods, expand the range of alternate power equalization, but when the modulation degree of some H bridge is greater than 1.15, this method without Method realizes alternate power equalization.
In conclusion existing alternate Power balance control method is main for three-phase cascaded H-bridges photovoltaic DC-to-AC converter There are the following problems:
(1) the alternate equalization methods based on fundamental wave zero sequence injection can improve three-phase cascaded H-bridges photovoltaic to a certain extent The unbalanced problem of alternate power of inverter, but adjustable range is smaller, when alternate serious uneven, system cannot stablize fortune Row.
(2) the alternate equalization methods of third-harmonic zero-sequence voltage are added although to expand the model of alternate power equalization based on fundamental wave zero sequence It encloses, but when some H-bridge unit output power is too big so that when its modulation degree is greater than 1.15, it is equal that this method cannot achieve alternate power Weighing apparatus, is not able to satisfy all operating conditions of three-phase cascaded H-bridges photovoltaic DC-to-AC converter.
Summary of the invention
The problem to be solved in the present invention is exactly to overcome the limitation of above scheme, for three-phase cascaded H-bridges photovoltaic DC-to-AC converter Alternate power is unbalanced to cause grid-connected current to distort this problem, proposes a kind of alternate power of three-phase cascaded H-bridges photovoltaic DC-to-AC converter Balance control method.This method can preferably adapt to various operating conditions, be not only able to achieve three-phase cascaded H-bridges photovoltaic DC-to-AC converter compared with Stable operation in a wide range of, and it is able to achieve the maximal power tracing of each H-bridge unit.
To solve technical problem of the invention, the present invention provides a kind of alternate power of three-phase cascaded H-bridges photovoltaic DC-to-AC converter Balance control method, the three-phase cascaded H-bridges photovoltaic DC-to-AC converter include A, B, C three-phase, and every phase is by N number of with photovoltaic module H-bridge unit and inductance LSComposition, which is characterized in that this control method include total DC voltage control, current on line side control and Alternate Power balance control, steps are as follows:
Step 1, total DC voltage control
Step 1.1, the DC voltage of each H-bridge unit in A, B, C three-phase is sampled respectively and passes through 100Hz trap Device filtering, obtains the DC voltage actual value of each H-bridge unit and is denoted as VPVAi,VPVBi,VPVCi, wherein ABC indicates inversion The three-phase circuit of device, i.e. A phase, B phase, C phase, i=1,2,3...N；Sampling three-phase network voltage actual value is simultaneously denoted as Vgrid_A, Vgrid_B,Vgrid_C, sampling three-phase power network current actual value is simultaneously denoted as Igrid_A,Igrid_B,Igrid_C, wherein ABC indicates inverter Three-phase circuit, i.e. A phase, B phase, C phase；
Step 1.2, it by carrying out MPPT maximum power point tracking control to H-bridge unit DC side each in A, B, C three-phase, obtains The DC voltage instruction value of each H-bridge unit, is denoted as V respectivelyPVAi *,VPVBi *,VPVCi *, wherein ABC indicates the three of inverter Circuitry phase, i.e. A phase, B phase, C phase, i=1,2,3...N；
Step 1.3, by voltage regulator, the instruction value of electric network active electric current is calculatedIts calculating formula are as follows:
Wherein, KVPFor voltage regulator proportionality coefficient, KVIFor voltage regulator integral coefficient, s is Laplace operator,For the sum of the DC voltage actual value of every mutually N number of H-bridge unit, For the sum of the DC voltage instruction value of every mutually N number of H-bridge unit；
Step 2, current on line side controls
Step 2.1, to the three-phase power grid voltage actual value V sampled in step 1.1grid_A,Vgrid_B,Vgrid_CCarry out locking phase Obtain electric network voltage phase θ and mains frequency ω；It is by synchronous rotating angle that the three phase network sampled in step 1.1 is electric It is compacted actual value Vgrid_A,Vgrid_B,Vgrid_CThe network voltage active component V being converted under rotating coordinate systemdIt is idle with network voltage Component Vq；The power network current actual value I that will be sampled in step 1.1 by synchronous rotating anglegrid_A,Igrid_B,Igrid_CTurn Change the power network current active component I under rotating coordinate system intodWith power network current reactive component Iq；
Network voltage active component VdWith network voltage reactive component VqCalculating formula are as follows:
Power network current active component IdWith power network current reactive component IqCalculating formula are as follows:
Step 2.2, if grid-connected inverters referenced reactive current valueIt is 0, passes through watt current adjuster and idle electricity respectively D axis PI regulated value E is calculated in throttle regulatordWith q axis PI regulated value Eq, calculating formula is respectively as follows:
Wherein, KiPFor watt current adjuster proportionality coefficient, KiIFor reactive current adjuster integral coefficient；
Step 2.3, the network voltage active component V obtained according to step 2.1d, network voltage reactive component Vq, power grid electricity Flow active component Id, power network current reactive component Iq, d axis PI regulated value E obtained in network voltage frequencies omega and step 2.2dWith Q axis PI regulated value Eq, d shaft voltage controlling value U is calculateddWith q shaft voltage controlling value Uq, it is shown below:
Wherein, LSFor filter inductance；
Step 2.4, d shaft voltage controlling value U step 2.3 obtaineddWith q shaft voltage controlling value UqIt is sat by synchronous rotary The inverse transformation of mark system obtains inverter three-phase modulations wave signal V under natural system of coordinatesra,Vrb,Vrc, calculating formula are as follows:
Step 3, alternate Power balance control
Step 3.1, the DC voltage actual value V of each H-bridge unit obtained according to step 1.1PVAi,VPVBi,VPVCiWith The DC voltage instruction value V for each H-bridge unit that step 1.2 obtainsPVAi *,VPVBi *,VPVCi *, every phase total voltage is calculated Equalizing coefficient Coefficient_A, Coefficient_B, Coefficient_C, be shown below:
Wherein,For the sum of the DC voltage actual value of every mutually N number of H-bridge unit,For the sum of the DC voltage instruction value of every mutually N number of H-bridge unit, i=1,2,3...N；
Step 3.2, by voltage between phases adjuster, the regulatory factor Factor_A of every phase total voltage is calculated, Factor_B, Factor_C, calculating formula are as follows:
Wherein KVP_PhaseFor voltage between phases adjuster proportionality coefficient, KiI_PhaseFor voltage between phases adjuster integral coefficient；
Step 3.3, the inverter three-phase modulations wave signal V obtained according to step 2.4ra,Vrb,VrcIt is obtained with step 3.2 Revised three-phase modulations wave signal is calculated in regulatory factor Factor_A, Factor_B, the Factor_C of every phase total voltageIts calculating formula are as follows:
Step 3.4, according to the DC voltage actual value V of each H-bridge unit sampled in step 1.1PVAi,VPVBi, VPVCiWith the DC voltage instruction value of each H-bridge unit obtained in step 1.2It is calculated every A H-bridge unit DC voltage error amount △ VAi,△VBi,△VCi, calculating formula are as follows:
Wherein, i=1,2,3...N；
Step 3.5, by the DC voltage error amount △ V of the N number of H-bridge unit of A phase obtained in step 3.4AiAccording to numerical value Size carries out ascending order arrangement, and difference sequence j=1 is held up in electricity consumption, and 2,3...N are labeled, then according to voltage error sequence The DC voltage actual value V of number j to its corresponding N number of H-bridge unitPVAiSequence is re-started, is obtained after N number of A phase sorts DC voltage actual value is simultaneously denoted as VAj；According to the step identical as A phase, the reality of the DC voltage after N number of B phase sorts is obtained It is worth and is denoted as VBj；According to the step identical as A phase, obtains the DC voltage actual value after N number of C phase sorts and be denoted as VCj；
Step 3.6, the DC voltage actual value V after the N number of sequence of A phase according to obtained in step 3.5AjBy inverter A Phase modulation wave signalIt is divided into N number of voltage range, judges current inverter A phase modulation wave signalLocating voltage range Ka, Wherein A phase voltage section KaIt is defined asKa=1,2,3...N；According to the step identical as A phase, Judge current inverter B phase modulation wave signalLocating voltage range Kb, wherein B phase voltage section KbIt is defined asKb=1,2,3...N；According to the step identical as A phase, current inverter C phase modulating wave is judged SignalLocating voltage range Kc, wherein C phase voltage section KcIt is defined as
Step 3.7, according to current inverter three-phase modulations wave signalPolarity, three phase network electric current is practical Value Igrid_A,Igrid_B,Igrid_CDirection and three-phase voltage section Ka,Kb,KcDetermine each mutually N number of H-bridge unit in ABC three-phase Output mode, specifically, the output mode of the N number of H-bridge unit of A phase is shown in step 3.8, the output mode of the N number of H-bridge unit of B phase is shown in step The output mode of the rapid N number of H-bridge unit of 3.9, C phase is shown in 3.10；
Step 3.8, according to current inverter A phase modulation wave signalPolarity, A phase power network current actual value Igrid_A's Direction and A phase voltage section KaDetermine the output mode of the N number of H-bridge unit of A phase, specific:
DC voltage actual value V after sequenceAjForH-bridge unit run on "+ 1 " level mode, and be denoted asDC voltage actual value V after sequenceAjForH-bridge unit run on level "0" mode, and be denoted asRow DC voltage actual value V after sequenceAjForH-bridge unit run on PWM mode, the H-bridge unit of PWM output mode Modulation wave voltage VPWMCalculating formula is as follows:
DC voltage actual value V after sequenceAjForH-bridge unit run on "+1 " level mould Formula, and be denoted asDC voltage actual value V after sequenceAjForH-bridge unit run on level "0" mode, and be denoted asDC voltage actual value V after sequenceAjForH-bridge unit run on PWM mode, the modulation wave voltage V of the H-bridge unit of PWM output modePWMCalculating formula is as follows:
DC voltage actual value V after sequenceAjForH-bridge unit run on " -1 " electricity It is flat-die type powdered, and be denoted asDC voltage actual value V after sequenceAjForH-bridge unit run on level "0" mode, and be denoted asDC voltage actual value V after sequenceAjForH-bridge unit run on PWM mode, the modulation wave voltage V of the H-bridge unit of PWM output modePWMCalculating formula is as follows:
DC voltage actual value V after sequenceAjForH-bridge unit run on "- 1 " level mode, and be denoted asDC voltage actual value V after sequenceAjForH-bridge unit run on level "0" mode, and be denoted asRow DC voltage actual value V after sequenceAjForH-bridge unit run on PWM mode, the H bridge list of PWM output mode The modulation wave voltage V of memberPWMCalculating formula is as follows:
Step 3.9, according to current inverter B phase modulation wave signalPolarity, B phase power network current actual value Igrid_B's Direction and B phase voltage section KbDetermine the output mode of the N number of H-bridge unit of B phase, specific:
DC voltage actual value V after sequenceBjForH-bridge unit run on "+ 1 " level mode, and be denoted asDC voltage actual value V after sequenceBjForH-bridge unit run on level "0" mode, and be denoted asSequence DC voltage actual value V afterwardsBjForH-bridge unit run on PWM mode, the H-bridge unit of PWM output mode Modulate wave voltage VPWMCalculating formula is as follows:
DC voltage actual value V after sequenceBjForH-bridge unit run on "+1 " electricity It is flat-die type powdered, and be denoted asDC voltage actual value V after sequenceBjForH-bridge unit run on level "0" mode, and be denoted asDC voltage actual value V after sequenceBjForH-bridge unit run on PWM Mode, the modulation wave voltage V of the H-bridge unit of PWM output modePWMCalculating formula is as follows:
DC voltage actual value V after sequenceBjForH-bridge unit run on " -1 " level Mode, and be denoted asDC voltage actual value V after sequenceBjForH-bridge unit run on level "0" mode, and be denoted asDC voltage actual value V after sequenceBjForH-bridge unit run on PWM Mode, the modulation wave voltage V of the H-bridge unit of PWM output modePWMCalculating formula is as follows:
DC voltage actual value V after sequenceBjForH-bridge unit run on "- 1 " level mode, and be denoted asDC voltage actual value V after sequenceBjForH-bridge unit run on level "0" mode, and be denoted asSequence DC voltage actual value V afterwardsBjForH-bridge unit run on PWM mode, the H-bridge unit of PWM output mode Modulate wave voltage VPWMCalculating formula is as follows:
Step 3.10, according to current inverter C phase modulation wave signalPolarity, C phase power network current actual value Igrid_C's Direction and C phase voltage section KcDetermine the output mode of the N number of H-bridge unit of C phase, specific:
DC voltage actual value V after sequenceCjForH-bridge unit run on "+1 " Level mode, and be denoted asDC voltage actual value V after sequenceCjForH-bridge unit run on level "0" mode, and be denoted asSequence DC voltage actual value V afterwardsCjForH-bridge unit run on PWM mode, the H-bridge unit of PWM output mode Modulate wave voltage VPWMCalculating formula is as follows:
DC voltage actual value V after sequenceCjForH-bridge unit run on "+1 " level Mode, and be denoted asDC voltage actual value V after sequenceCjForH-bridge unit run on level "0" mode, and be denoted asDC voltage actual value V after sequenceCjForH-bridge unit run on PWM Mode, the modulation wave voltage V of the H-bridge unit of PWM output modePWMCalculating formula is as follows:
DC voltage actual value V after sequenceCjForH-bridge unit run on " -1 " electricity It is flat-die type powdered, and be denoted asDC voltage actual value V after sequenceCjForH-bridge unit run on level "0" mode, and be denoted asDC voltage actual value V after sequenceCjForH-bridge unit run on PWM mode, the modulation wave voltage V of the H-bridge unit of PWM output modePWMCalculating formula is as follows:
DC voltage actual value V after sequenceCjForH-bridge unit run on " -1 " Level mode, and be denoted asDC voltage actual value V after sequenceCjForH-bridge unit run on level "0" mode, and be denoted asSequence DC voltage actual value V afterwardsCjForH-bridge unit run on PWM mode, the H-bridge unit of PWM output mode Modulate wave voltage VPWMCalculating formula is as follows:
Compared with prior art, the alternate Power balance control of a kind of three-phase cascaded H-bridges photovoltaic DC-to-AC converter disclosed by the invention Method realizes three-phase cascaded H-bridges photovoltaic DC-to-AC converter Power balance control, its advantages under the conditions of alternate unbalanced power It is embodied in:
1, alternate Power balance control method adjustable range proposed by the present invention is wider, can satisfy and adapt to three-phase cascade The various unbalanced operating conditions of H bridge photovoltaic DC-to-AC converter.
2, alternate Power balance control method physical significance proposed by the present invention is clear, simple, is easy to Project Realization.
Detailed description of the invention
Fig. 1 is three-phase cascaded H-bridges photovoltaic DC-to-AC converter main circuit topology block diagram.
Fig. 2 is three-phase cascaded H-bridges photovoltaic DC-to-AC converter master control structural block diagram.
Fig. 3 is the alternate Power balance control block diagram of three-phase cascaded H-bridges photovoltaic DC-to-AC converter.
Fig. 4 is inverse using three-phase cascaded H-bridges photovoltaic when traditional alternate method for balancing powers under the extremely uneven operating condition of illumination Become device grid-connected current waveform.
Fig. 5 be under the extremely uneven operating condition of illumination using three-phase cascaded H-bridges photovoltaic DC-to-AC converter when control method of the present invention simultaneously Net current waveform.
Specific embodiment
In order to make the objectives, technical solutions, and advantages of the present invention clearer, with reference to the accompanying drawings and embodiments, right Present invention work further clearly and completely describes.
Fig. 1 is three-phase of embodiment of the present invention cascaded H-bridges photovoltaic DC-to-AC converter topological structure, including A, B, C three-phase, and every phase is by N A H-bridge unit and inductance L with photovoltaic moduleSComposition, H-bridge unit is by four set of power switches at each H bridge direct current Side is independently-powered by photovoltaic module, and photovoltaic module nominal working conditions are the intensity of illumination 1000W/m at 25C ° of temperature2Under most High-power voltage is 30.59V, and every piece of photovoltaic module is connected by 18.8mF capacitor with each H-bridge unit, and every phase passes through 1.8mH inductance LSIt is connected to power grid.
Control figure of the invention is as shown in Fig. 2, include that total DC voltage control, current on line side control and alternate power are equal Weighing apparatus control three parts.
Step 1, total DC voltage control
Step 1.1, the DC voltage of each H-bridge unit in A, B, C three-phase is sampled respectively and passes through 100Hz trap Device filtering, obtains the DC voltage actual value of each H-bridge unit and is denoted as VPVAi,VPVBi,VPVCi, wherein ABC indicates inversion The three-phase circuit of device, i.e. A phase, B phase, C phase, i=1,2,3...N；Sampling three-phase network voltage actual value is simultaneously denoted as Vgrid_A, Vgrid_B,Vgrid_C, sampling three-phase power network current actual value is simultaneously denoted as Igrid_A,Igrid_B,Igrid_C, wherein ABC indicates inverter Three-phase circuit, i.e. A phase, B phase, C phase.
DC voltage actual value in the present embodiment, by taking three H-bridge units of every phase as an example, when each H-bridge unit is initial For VPVA1=VPVA2=VPVA3=30.59V, VPVB1=VPVB2=VPVB3=30.59V, VPVC1=VPVC2=VPVC3=30.59V.
Step 1.2, step 1.2, by carrying out MPPT maximum power point tracking to H-bridge unit DC side each in A, B, C three-phase Control, obtains the DC voltage instruction value of each H-bridge unit, is denoted as V respectivelyPVAi *,VPVBi *,VPVCi *, wherein ABC indicates inverse The three-phase circuit of change device, i.e. A phase, B phase, C phase, i=1,2,3...N.
In the present embodiment, initial time, each H-bridge unit works under rated condition, obtains the direct current of each H-bridge unit Side voltage instruction value is In t=0.6s, the intensity of illumination of three H-bridge units of A phase is reduced to 800W/ respectively m2、800W/m2、500W/m2, the intensity of illumination of three H-bridge units of B phase is reduced to 800W/m respectively2、800W/m2、500W/m2, C The intensity of illumination of three H-bridge units of phase is reduced to 400W/m2, the DC voltage instruction value for obtaining each H-bridge unit is
Step 1.3, by voltage regulator, the instruction value of electric network active electric current is calculatedIts calculating formula are as follows:
Wherein, KVPFor voltage regulator proportionality coefficient, KVIFor voltage regulator integral coefficient, s is Laplace operator,For the sum of the DC voltage actual value of every mutually N number of H-bridge unit, For the sum of the DC voltage instruction value of every mutually N number of H-bridge unit.Voltage regulator Proportional coefficient KVPWith voltage regulator integration system Number KVIIt is designed according to conventional gird-connected inverter, in the present embodiment, KVP=2, KVI=20.
Step 2, current on line side controls
Step 2.1, to the three-phase power grid voltage actual value V sampled in step 1.1grid_A,Vgrid_B,Vgrid_CCarry out locking phase Obtain electric network voltage phase θ and mains frequency ω；It is by synchronous rotating angle that the three phase network sampled in step 1.1 is electric It is compacted actual value Vgrid_A,Vgrid_B,Vgrid_CThe network voltage active component V being converted under rotating coordinate systemdIt is idle with network voltage Component Vq；The power network current actual value I that will be sampled in step 1.1 by synchronous rotating anglegrid_A,Igrid_B,Igrid_CTurn Change the power network current active component I under rotating coordinate system intodWith power network current reactive component Iq。
Network voltage active component VdWith network voltage reactive component VqCalculating formula are as follows:
Power network current active component IdWith power network current reactive component IqCalculating formula are as follows:
Step 2.2, if grid-connected inverters referenced reactive current valueIt is 0, respectively by watt current adjuster and idle D axis PI regulated value E is calculated in current regulatordWith q axis PI regulated value Eq, calculating formula is respectively as follows:
Wherein, KiPFor watt current adjuster proportionality coefficient, KiIFor reactive current adjuster integral coefficient.KiPAnd KiIIt presses More solito gird-connected inverter is designed, in the present embodiment, KiP=4, KiI=20.
Step 2.3, the network voltage active component V obtained according to step 2.1d, network voltage reactive component Vq, power grid electricity Flow active component Id, power network current reactive component Iq, d axis PI regulated value E obtained in network voltage frequencies omega and step 2.2dWith Q axis PI regulated value Eq, d shaft voltage controlling value U is calculateddWith q shaft voltage controlling value Uq, it is shown below:
Wherein, LSFor filter inductance.
Step 2.4, d shaft voltage controlling value U step 2.3 obtaineddWith q shaft voltage controlling value UqIt is sat by synchronous rotary The inverse transformation of mark system obtains inverter three-phase modulations wave signal V under natural system of coordinatesra,Vrb,Vrc, calculating formula are as follows:
Step 3, alternate Power balance control
The alternate Power balance control is as shown in Figure 3.
Step 3.1, the DC voltage actual value V of each H-bridge unit obtained according to step 1.1PVAi,VPVBi,VPVCiWith The DC voltage instruction value V for each H-bridge unit that step 1.2 obtainsPVAi *,VPVBi *,VPVCi *, every phase total voltage is calculated Equalizing coefficient Coefficient_A, Coefficient_B, Coefficient_C, be shown below:
Wherein,For the sum of the DC voltage actual value of every mutually N number of H-bridge unit,For the sum of the DC voltage instruction value of every mutually N number of H-bridge unit, i=1,2,3...N.
Step 3.2, by voltage between phases adjuster, the regulatory factor Factor_A of every phase total voltage is calculated, Factor_B, Factor_C, calculating formula are as follows:
Wherein KVP_PhaseFor voltage between phases adjuster proportionality coefficient, KiI_PhaseFor voltage between phases adjuster integral coefficient.Phase Between voltage regulator Proportional coefficient KVP_PhaseWith voltage between phases adjuster integral coefficient KiI_PhaseAccording to conventional gird-connected inverter into Row designs, in the present embodiment, KVP_Phase=6, KiI_Phase=40.
Step 3.3, the inverter three-phase modulations wave signal V obtained according to step 2.4ra,Vrb,VrcIt is obtained with step 3.2 Revised three-phase modulations wave signal is calculated in regulatory factor Factor_A, Factor_B, the Factor_C of every phase total voltageIts calculating formula are as follows:
Step 3.4, according to the DC voltage actual value V of each H-bridge unit sampled in step 1.1PVAi,VPVBi, VPVCiWith the DC voltage instruction value of each H-bridge unit obtained in step 1.2It is calculated every A H-bridge unit DC voltage error amount △ VAi,△VBi,△VCi, calculating formula are as follows:
Wherein, i=1,2,3...N.
Step 3.5, by the DC voltage error amount △ V of the N number of H-bridge unit of A phase obtained in step 3.4AiAccording to numerical value Size carries out ascending order arrangement, and difference sequence j=1 is held up in electricity consumption, and 2,3...N are labeled, then according to voltage error sequence The DC voltage actual value V of number j to its corresponding N number of H-bridge unitPVAiSequence is re-started, is obtained after N number of A phase sorts DC voltage actual value is simultaneously denoted as VAj；According to the step identical as A phase, the reality of the DC voltage after N number of B phase sorts is obtained It is worth and is denoted as VBj；According to the step identical as A phase, obtains the DC voltage actual value after N number of C phase sorts and be denoted as VCj。
Step 3.6, the DC voltage actual value V after the N number of sequence of A phase according to obtained in step 3.5AjBy inverter A Phase modulation wave signalIt is divided into N number of voltage range, judges current inverter A phase modulation wave signalLocating voltage range Ka, Wherein A phase voltage section KaIt is defined asKa=1,2,3...N；According to the step identical as A phase, Judge current inverter B phase modulation wave signalLocating voltage range Kb, wherein B phase voltage section KbIt is defined asKb=1,2,3...N；According to the step identical as A phase, current inverter C phase modulating wave is judged SignalLocating voltage range Kc, wherein C phase voltage section KcIt is defined asKc=1,2, 3...N。
Step 3.7, according to current inverter three-phase modulations wave signalPolarity, three phase network electric current is practical Value Igrid_A,Igrid_B,Igrid_CDirection and three-phase voltage section Ka,Kb,KcDetermine each mutually N number of H-bridge unit in ABC three-phase Output mode, specifically, the output mode of the N number of H-bridge unit of A phase is shown in step 3.8, the output mode of the N number of H-bridge unit of B phase is shown in step The output mode of the rapid N number of H-bridge unit of 3.9, C phase is shown in 3.10.
Step 3.8, according to current inverter A phase modulation wave signalPolarity, A phase power network current actual value Igrid_A's Direction and A phase voltage section KaDetermine the output mode of the N number of H-bridge unit of A phase, specific:
DC voltage actual value V after sequenceAjForH-bridge unit run on "+ 1 " level mode, and be denoted asDC voltage actual value V after sequenceAjForH-bridge unit run on level "0" mode, and be denoted asRow DC voltage actual value V after sequenceAjForH-bridge unit run on PWM mode, the H-bridge unit of PWM output mode Modulation wave voltage VPWMCalculating formula is as follows:
DC voltage actual value V after sequenceAjForH-bridge unit run on "+1 " electricity It is flat-die type powdered, and be denoted asDC voltage actual value V after sequenceAjForH-bridge unit run on level "0" mode, and be denoted asDC voltage actual value V after sequenceAjForH-bridge unit run on PWM mode, the modulation wave voltage V of the H-bridge unit of PWM output modePWMCalculating formula is as follows:
DC voltage actual value V after sequenceAjForH-bridge unit run on " -1 " level Mode, and be denoted asDC voltage actual value V after sequenceAjForH-bridge unit run on level "0" mode, and be denoted as DC voltage actual value V after sequenceAjForH-bridge unit run on PWM mode, the H-bridge unit of PWM output mode Modulate wave voltage VPWMCalculating formula is as follows:
DC voltage actual value V after sequenceAjForH-bridge unit run on "- 1 " level mode, and be denoted asDC voltage actual value V after sequenceAjForH-bridge unit run on level "0" mode, and be denoted asRow DC voltage actual value V after sequenceAjForH-bridge unit run on PWM mode, the H-bridge unit of PWM output mode Modulation wave voltage VPWMCalculating formula is as follows:
Step 3.9, according to current inverter B phase modulation wave signalPolarity, B phase power network current actual value Igrid_B's Direction and B phase voltage section KbDetermine the output mode of the N number of H-bridge unit of B phase, specific:
DC voltage actual value V after sequenceBjForH-bridge unit run on "+ 1 " level mode, and be denoted asDC voltage actual value V after sequenceBjForH-bridge unit run on level "0" mode, and be denoted asSequence DC voltage actual value V afterwardsBjForH-bridge unit run on PWM mode, the H-bridge unit of PWM output mode Modulate wave voltage VPWMCalculating formula is as follows:
DC voltage actual value V after sequenceBjForH-bridge unit run on "+1 " level Mode, and be denoted asDC voltage actual value V after sequenceBjForH-bridge unit run on level "0" mode, and be denoted asDC voltage actual value V after sequenceBjForH-bridge unit run on PWM mode, the modulation wave voltage V of the H-bridge unit of PWM output modePWMCalculating formula is as follows:
DC voltage actual value V after sequenceBjForH-bridge unit run on " -1 " electricity It is flat-die type powdered, and be denoted asDC voltage actual value V after sequenceBjForH-bridge unit run on level "0" mode, and be denoted asDC voltage actual value V after sequenceBjForH-bridge unit run on PWM mode, the modulation wave voltage V of the H-bridge unit of PWM output modePWMCalculating formula is as follows:
DC voltage actual value V after sequenceBjForH-bridge unit run on "- 1 " level mode, and be denoted asDC voltage actual value V after sequenceBjForH-bridge unit run on level "0" mode, and be denoted asSequence DC voltage actual value V afterwardsBjForH-bridge unit run on PWM mode, the H-bridge unit of PWM output mode Modulate wave voltage VPWMCalculating formula is as follows:
Step 3.10, according to current inverter C phase modulation wave signal Vr * cPolarity, C phase power network current actual value Igrid_C Direction and C phase voltage section KcDetermine the output mode of the N number of H-bridge unit of C phase, specific:
DC voltage actual value V after sequenceCjForH-bridge unit run on "+ 1 " level mode, and be denoted asDC voltage actual value V after sequenceCjForH-bridge unit run on level "0" mode, and be denoted asSequence DC voltage actual value V afterwardsCjForH-bridge unit run on PWM mode, the H-bridge unit of PWM output mode Modulate wave voltage VPWMCalculating formula is as follows:
DC voltage actual value V after sequenceCjForH-bridge unit run on "+1 " electricity It is flat-die type powdered, and be denoted asDC voltage actual value V after sequenceCjForH-bridge unit run on level "0" mode, and be denoted asDC voltage actual value V after sequenceCjForH-bridge unit run on PWM Mode, the modulation wave voltage V of the H-bridge unit of PWM output modePWMCalculating formula is as follows:
DC voltage actual value V after sequenceCjForH-bridge unit run on " -1 " electricity It is flat-die type powdered, and be denoted asDC voltage actual value V after sequenceCjForH-bridge unit run on level "0" mode, and be denoted as DC voltage actual value V after sequenceCjForH-bridge unit run on PWM mode, the H-bridge unit of PWM output mode Modulate wave voltage VPWMCalculating formula is as follows:
DC voltage actual value V after sequenceCjForH-bridge unit run on "- 1 " level mode, and be denoted asDC voltage actual value V after sequenceCjForH-bridge unit run on level "0" mode, and be denoted asSequence DC voltage actual value V afterwardsCjForH-bridge unit run on PWM mode, the H-bridge unit of PWM output mode Modulate wave voltage VPWMCalculating formula is as follows:
Fig. 4 is under the extremely uneven operating condition of illumination, inverse using three-phase cascaded H-bridges photovoltaic when traditional alternate method for balancing powers Becoming device grid-connected current waveform, the current total harmonic distortion (THD) of A phase, B phase, C phase is respectively 11.56%, 7.64%, 5.58%, Three-phase grid electric current Severe distortion.
Fig. 5 is under the extremely uneven operating condition of illumination, simultaneously using three-phase cascaded H-bridges photovoltaic DC-to-AC converter when control method of the present invention Net current waveform, the electric current THD of A phase, B phase, C phase are respectively 1.25%, 1.34%, 1.78%, compared to traditional control method, Control method of the present invention substantially improves grid-connected current quality.

Claims (1)

1. a kind of alternate Power balance control method of three-phase cascaded H-bridges photovoltaic DC-to-AC converter, the three-phase cascaded H-bridges photovoltaic inversion Device includes ABC three-phase, and every phase is by N number of H-bridge unit with photovoltaic module and inductance LSComposition, which is characterized in that this controlling party Method includes total DC voltage control, current on line side control and alternate Power balance control, and steps are as follows:
Step 1, total DC voltage control
Step 1.1, the DC voltage of each H-bridge unit in A, B, C three-phase is sampled respectively and passes through the filter of 100Hz trapper Wave obtains the DC voltage actual value of each H-bridge unit and is denoted as V respectivelyPVAi,VPVBi,VPVCi, wherein A, B, C distinguish table Show the three-phase circuit of inverter, i.e. A phase, B phase, C phase, i=1,2,3...N；Sampling three-phase network voltage actual value is simultaneously remembered respectively For Vgrid_A,Vgrid_B,Vgrid_C, sampling three-phase power network current actual value is simultaneously denoted as I respectivelygrid_A,Igrid_B,Igrid_C；
Step 1.2, it by carrying out MPPT maximum power point tracking control to H-bridge unit DC side each in A, B, C three-phase, obtains each The DC voltage instruction value of H-bridge unit, is denoted as V respectivelyPVAi *,VPVBi *,VPVCi *；
Step 1.3, by voltage regulator, the instruction value of electric network active electric current is calculatedIts calculating formula are as follows:
Wherein, KVPFor voltage regulator proportionality coefficient, KVIFor voltage regulator integral coefficient, s is Laplace operator,The sum of the DC voltage actual value of N number of H-bridge unit respectively in A, B, C three-phase,The sum of the DC voltage instruction value of N number of H-bridge unit respectively in A, B, C three-phase；
Step 2, current on line side controls
Step 2.1, to the three-phase power grid voltage actual value V sampled in step 1.1grid_A,Vgrid_B,Vgrid_CCarry out locking phase acquisition Electric network voltage phase θ and mains frequency ω；It is by synchronous rotating angle that the three-phase power grid voltage sampled in step 1.1 is real Actual value Vgrid_A,Vgrid_B,Vgrid_CThe network voltage active component V being converted under rotating coordinate systemdWith network voltage reactive component Vq；The power network current actual value I that will be sampled in step 1.1 by synchronous rotating anglegrid_A,Igrid_B,Igrid_CIt is converted into Power network current active component I under rotating coordinate systemdWith power network current reactive component Iq；
Network voltage active component VdWith network voltage reactive component VqCalculating formula are as follows:
Power network current active component IdWith power network current reactive component IqCalculating formula are as follows:
Step 2.2, if grid-connected inverters referenced reactive current valueIt is 0, passes through watt current adjuster and reactive current tune respectively Device is saved, d axis PI regulated value E is calculateddWith q axis PI regulated value Eq, calculating formula is respectively as follows:
Wherein, KiPFor watt current adjuster proportionality coefficient, KiIFor reactive current adjuster integral coefficient；
Step 2.3, the network voltage active component V obtained according to step 2.1d, network voltage reactive component Vq, power network current has Function component Id, power network current reactive component Iq, d axis PI regulated value E obtained in network voltage frequencies omega and step 2.2dWith q axis PI regulated value Eq, d shaft voltage controlling value U is calculateddWith q shaft voltage controlling value Uq, it is shown below:
Wherein, LSFor filter inductance；
Step 2.4, d shaft voltage controlling value U step 2.3 obtaineddWith q shaft voltage controlling value UqBy synchronous rotating frame Inverse transformation obtains inverter three-phase modulations wave signal V under natural system of coordinatesra,Vrb,Vrc, calculating formula are as follows:
Step 3, alternate Power balance control
Step 3.1, the DC voltage actual value V of each H-bridge unit obtained according to step 1.1PVAi,VPVBi,VPVCiAnd step The DC voltage instruction value V of 1.2 obtained each H-bridge unitsPVAi *,VPVBi *,VPVCi *, the equal of every phase total voltage is calculated Weigh coefficient Coefficient_A, Coefficient_B, Coefficient_C, is shown below:
Wherein,For the sum of the DC voltage actual value of every mutually N number of H-bridge unit,For the sum of the DC voltage instruction value of every mutually N number of H-bridge unit, i=1,2,3...N；
Step 3.2, by voltage between phases adjuster, regulatory factor Factor_A, the Factor_B of every phase total voltage is calculated, Factor_C, calculating formula are as follows:
Wherein KVP_PhaseFor voltage between phases adjuster proportionality coefficient, KiI_PhaseFor voltage between phases adjuster integral coefficient；
Step 3.3, the inverter three-phase modulations wave signal V obtained according to step 2.4ra,Vrb,VrcThe every phase obtained with step 3.2 Revised three-phase modulations wave signal is calculated in regulatory factor Factor_A, Factor_B, the Factor_C of total voltageIts calculating formula are as follows:
Step 3.4, according to the DC voltage actual value V of each H-bridge unit sampled in step 1.1PVAi,VPVBi,VPVCi With the DC voltage instruction value V of each H-bridge unit obtained in step 1.2PVAi *,VPVBi *,VPVCi *, each H bridge is calculated Unit DC voltage error amount △ VAi,△VBi,△VCi, calculating formula are as follows:
Wherein, i=1,2,3...N；
Step 3.5, by the DC voltage error amount △ V of the N number of H-bridge unit of A phase obtained in step 3.4AiAccording to numerical values recited Ascending order arrangement is carried out, and difference sequence j=1 is held up in electricity consumption, 2,3...N are labeled, then according to j pairs of voltage error sequence number The DC voltage actual value V of its corresponding N number of H-bridge unitPVAiSequence is re-started, the DC side after N number of A phase sorts is obtained Voltage actual value is simultaneously denoted as VAj；According to the step identical as A phase, obtains the DC voltage actual value after N number of B phase sorts and remember For VBj；According to the step identical as A phase, obtains the DC voltage actual value after N number of C phase sorts and be denoted as VCj；
Step 3.6, the DC voltage actual value V after the N number of sequence of A phase according to obtained in step 3.5AjInverter A phase is adjusted Wave signal processedIt is divided into N number of voltage range, judges current inverter A phase modulation wave signalLocating voltage range Ka, wherein A phase voltage section KaIt is defined asKa=1,2,3...N；According to the step identical as A phase, judgement Current inverter B phase modulation wave signalLocating voltage range Kb, wherein B phase voltage section KbIt is defined asKb=1,2,3...N；According to the step identical as A phase, current inverter C phase modulating wave is judged SignalLocating voltage range Kc, wherein C phase voltage section KcIt is defined asKc=1,2, 3...N；
Step 3.7, according to current inverter three-phase modulations wave signalPolarity, three phase network current actual value Igrid_A,Igrid_B,Igrid_CDirection and three-phase voltage section Ka,Kb,KcDetermine the defeated of each mutually N number of H-bridge unit in ABC three-phase Mode out, specifically, the output mode of the N number of H-bridge unit of A phase is shown in step 3.8, the output mode of the N number of H-bridge unit of B phase is shown in step The output mode of the N number of H-bridge unit of 3.9, C phases is shown in 3.10；
Step 3.8, according to current inverter A phase modulation wave signalPolarity, A phase power network current actual value Igrid_ADirection And A phase voltage section KaDetermine the output mode of the N number of H-bridge unit of A phase, specific:
(1)Igrid_A> 0
DC voltage actual value V after sequenceAjForH-bridge unit run on "+1 " level Mode, and be denoted asDC voltage actual value V after sequenceAjForH-bridge unit run on level "0" mode, and be denoted asSequence DC voltage actual value V afterwardsAjForH-bridge unit run on PWM mode, the H-bridge unit of PWM output mode Modulate wave voltage VPWMCalculating formula is as follows:
(2)Igrid_A≤0
DC voltage actual value V after sequenceAjForH-bridge unit run on "+1 " level mode, And it is denoted asDC voltage actual value V after sequenceAjForH-bridge unit run on level "0" mode, and be denoted asDC voltage actual value V after sequenceAjForH-bridge unit run on PWM mode, the modulation wave voltage V of the H-bridge unit of PWM output modePWMCalculating formula is as follows:
(3)Igrid_A> 0
DC voltage actual value V after sequenceAjForH-bridge unit run on " -1 " level mode, And it is denoted asDC voltage actual value V after sequenceAjForH-bridge unit run on level "0" mode, and be denoted asDC voltage actual value V after sequenceAjForH-bridge unit run on PWM Mode, the modulation wave voltage V of the H-bridge unit of PWM output modePWMCalculating formula is as follows:
(4)Igrid_A≤0
DC voltage actual value V after sequenceAjForH-bridge unit run on " -1 " level Mode, and be denoted asDC voltage actual value V after sequenceAjForH-bridge unit run on level "0" mode, and be denoted asRow DC voltage actual value V after sequenceAjForH-bridge unit run on PWM mode, the H-bridge unit of PWM output mode Modulation wave voltage VPWMCalculating formula is as follows:
Step 3.9, according to current inverter B phase modulation wave signalPolarity, B phase power network current actual value Igrid_BDirection And B phase voltage section KbDetermine the output mode of the N number of H-bridge unit of B phase, specific:
(1)Igrid_B> 0
DC voltage actual value V after sequenceBjForH-bridge unit run on "+1 " level Mode, and be denoted asDC voltage actual value V after sequenceBjForH-bridge unit run on level "0" mode, and be denoted asSequence DC voltage actual value V afterwardsBjForH-bridge unit run on PWM mode, the H-bridge unit of PWM output mode Modulate wave voltage VPWMCalculating formula is as follows:
(2)Igrid_B≤0
DC voltage actual value V after sequenceBjForH-bridge unit run on "+1 " level mode, and It is denoted asDC voltage actual value V after sequenceBjFor's H-bridge unit runs on level "0" mode, and is denoted asDC voltage after sequence Actual value VBjForH-bridge unit run on PWM mode, the modulation wave voltage V of the H-bridge unit of PWM output modePWMIt calculates Formula is as follows:
(3)Igrid_B> 0
DC voltage actual value V after sequenceBjForH-bridge unit run on " -1 " level mode, and It is denoted asDC voltage actual value V after sequenceBjFor H-bridge unit run on level "0" mode, and be denoted asDC side electricity after sequence It is compacted actual value VBjForH-bridge unit run on PWM mode, the modulation wave voltage V of the H-bridge unit of PWM output modePWMMeter Formula is as follows:
(4)Igrid_B≤0
DC voltage actual value V after sequenceBjForH-bridge unit run on " -1 " level Mode, and be denoted asDC voltage actual value V after sequenceBjForH-bridge unit run on level "0" mode, and be denoted asSequence DC voltage actual value V afterwardsBjForH-bridge unit run on PWM mode, the H-bridge unit of PWM output mode Modulate wave voltage VPWMCalculating formula is as follows:
Step 3.10, according to current inverter C phase modulation wave signalPolarity, C phase power network current actual value Igrid_CDirection And C phase voltage section KcDetermine the output mode of the N number of H-bridge unit of C phase, specific:
(1)Igrid_C> 0
DC voltage actual value V after sequenceCjForH-bridge unit run on "+1 " level Mode, and be denoted asDC voltage actual value V after sequenceCjForH-bridge unit run on level "0" mode, and be denoted asSequence DC voltage actual value V afterwardsCjForH-bridge unit run on PWM mode, the H-bridge unit of PWM output mode Modulate wave voltage VPWMCalculating formula is as follows:
(2)Igrid_C≤0
DC voltage actual value V after sequenceCjForH-bridge unit run on "+1 " level mode, and It is denoted asDC voltage actual value V after sequenceCjFor's H-bridge unit runs on level "0" mode, and is denoted asDC voltage after sequence Actual value VCjForH-bridge unit run on PWM mode, the modulation wave voltage V of the H-bridge unit of PWM output modePWMIt calculates Formula is as follows:
(3)Igrid_C> 0
DC voltage actual value V after sequenceCjForH-bridge unit run on " -1 " level mode, and It is denoted asDC voltage actual value V after sequenceCjFor H-bridge unit run on level "0" mode, and be denoted asDC side electricity after sequence It is compacted actual value VCjForH-bridge unit run on PWM mode, the modulation wave voltage V of the H-bridge unit of PWM output modePWMMeter Formula is as follows:
(4)Igrid_C≤0
DC voltage actual value V after sequenceCjForH-bridge unit run on " -1 " level Mode, and be denoted asDC voltage actual value V after sequenceCjForH-bridge unit run on level "0" mode, and be denoted asSequence DC voltage actual value V afterwardsCjForH-bridge unit run on PWM mode, the H-bridge unit of PWM output mode Modulate wave voltage VPWMCalculating formula is as follows:
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