CN106099971B - Improve control method and system of the single-phase photovoltaic inverter to the adaptability of light current net - Google Patents
Improve control method and system of the single-phase photovoltaic inverter to the adaptability of light current net Download PDFInfo
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- Y02E10/563—Power conversion electric or electronic aspects for grid-connected applications
Abstract
Description
Technical field
The present invention relates to a kind of digital control method of single-phase photovoltaic grid-connected inverter and systems, particular by structure phase Position adjuster come realize net side active damping control, adaptability of the inverter to light current net can be effectively improved, in electric network impedance Wide scope changes still reliable grid connection, meets Grid-connection standards.
Background technology
It is the distributed generation system of representative as one of the major way of renewable energy utilization using wind energy and solar energy, Can dominate existing power grid economical operation and, increasingly increase using proportion in electric system.With distribution Power grid quantity, the increase of grid-connected power and distributing position it is extensive, power grid increasingly shows the characteristic of light current net：Power grid Impedance be can not ignore, and be changed with power system operating mode.This electric network impedance variation characteristic will lead to inverter control system Loop gain variation, it is even unstable that oscillation occurs in grid-connected inverters electric current.
Wherein, single-phase photovoltaic grid-connected inverter is because of its smaller size smaller, cheap price and relatively flexible portability and group Net characteristic is increasingly favored by family, business and small hydropower station.Single-phase photovoltaic grid-connected inverter is limited by its volume and cost System, grid-connected power is generally in 5kW hereinafter, switching frequency is 20kHz or so, frequently with LC type net side filters.
Fig. 1 is the structure chart of existing single-phase photovoltaic inverter control system, including DC power supply 1, inverter bridge 2, LC filtering Device 3, public electric wire net 4, current controller 5, PWM generators 6.Wherein, inverter 2 is by 1~T4 of switch transistor T and sustained diode 1 ~D4 is formed；LC filters are by filter inductance LoWith filter capacitor CoComposition；Public electric wire net is by electric network impedance Zg and network voltage source Vg is formed；CS1For inductive current iLSensor；VS1For grid entry point voltage vPCCSensor.HvAnd HiRespectively grid entry point voltage vPCC With inductive current iLHardware sampling processing circuit equivalent transfer function, generally low-pass first order filter, according to HvAnd HiIt obtains simultaneously Site voltage feedback signal vPCC_ofWith inductor current feedback signal iL_of.Current controller 5 is collected grid-connected using sensor Point voltage vPCC_ofGrid entry point voltage-phase θ is obtained by software phase-lock loop SPLL, with inductive current benchmark I*Inductance is constituted together The reference i of electric currentL_ref；At the same time, the reference i of electric currentL_refWith the collected inductive current i of sensorL_ofCarry out closed loop tune Section, specific control process will be illustrated in conjunction with Fig. 2.It is humorous in order to inhibit net side filter and public electric wire net impedance to form LCL Shake spike, and current controller 5 introduces grid entry point voltage vPCC_ofFeedforward Decoupling realizes active damping control.
Fig. 2 is the control block diagram of single-phase inverter shown in FIG. 1, wherein GdTo use digital control introduced sampling Delay and PWM modulation delay, generally 1.5 sampling period Ts；ZLo、ZCoIt is respectively filter inductance, filter capacitor and electricity with Zg Net impedance；Kpwm is bridge gain.It can be seen that inductive current refers to iL_refSubtract inductor current feedback signal iL_ofIt obtains Inductive current error signal, the error signal pass through adjuster GiAfterwards, with grid entry point voltage feedback signal vPCC_ofIt is added, jointly Constitute modulated signal vm；The modulated signal passes through PWM generators, obtains the drive signal of each switching tube of inverter bridge, and then obtain To inverter output voltage Vab, by adjusting inverter output voltage VabMake inductive current iLTrack inductive current reference iL_ref。
From figure 2 it can be seen that due to feedforward path low-pass filter HvDelay and digital control delay GdPresence, and Site voltage feedback signal vPCC_ofWith grid entry point voltage vPCCAnd modulated signal vmWith inverter bridge output voltage VabBetween exist Phase delay, especially high band section retards are even more serious, therefore are using grid entry point voltage feedback signal vPCC_ofFeedforward When carrying out active damping control, resonance inhibition will be affected, and change in mains impedance, even result in overcurrent etc. and delay Machine phenomenon.
Invention content
In view of the above-mentioned problems, the object of the present invention is to provide a kind of raising single-phase photovoltaic inverters to the adaptability of light current net Control method and system, the control method is by grid entry point voltage feedback signal vPCC_ofCurrent regulation is superimposed to after being handled The output of device, compensating sampling and control postpone, and realize to the phasing of grid entry point voltage feedback signal, improve unidirectional photovoltaic Inverter is to the adaptability of light current net, to realize the inverter stable operation off the net in light current.
In order to solve the above technical problems, a kind of technical solution that the present invention uses is：
A kind of raising single-phase photovoltaic inverter includes the following steps the control method of the adaptability of light current net：
S1, the voltage feedback signal v for obtaining grid entry pointPCC_ofWith inductive current iL_of, voltage feedback signal vPCC_ofAdopt It is respectively H that sample, which postpones transmission function,v, inductive current iL_ofSampling delay transmission function be Hi；
S2, by feedback signal iL_ofSubstitute into the adjusted signal V of current regulatorr1；
S3, by feedback signal vPCC_ofSubstitute into the adjusted signal V of phase regulatorr2；
S4, by Vr1And Vr2Addition obtains modulated signal vm, and PWM generators are sent into, generate the PWM of each switching tube of inverter Drive signal.
Preferably, in step S1, the voltage feedback signal v is obtained by voltage sensorPCC_of；
And/or
The inductive current i is obtained by current sensorL_of。
Preferably, step S2 includes：
S21, according to the voltage feedback signal vPCC_ofElectric network voltage phase θ is obtained, further according to the electric network voltage phase θ and current reference benchmark I*, inductive current is obtained by following formula (1) and refers to iL_ref,
iL_ref=I*×sin(θ) (1)；
Inductive current is referred to i by S22, according to the following formula (2)L_refWith inductor current feedback signal iL_ofSubtract each other, through overcurrent The adjusted signal v of adjusterr1,
vr1=Gi×(iL_ref-iL_of) (2)。
Preferably, step S3 includes：
S31, grid entry point voltage feedback signal vPCC_ofBy phase adjusted function Gv1(s), obtain output signal vPCC_LL, Gv1(s)As shown in following formula (3),
Wherein, Kp1For phase adjusted function gain,For phase adjusted function initial angular frequency,For phase adjusted letter Number terminates angular frequency, and α ＜ 1, s are Laplace operator；
S32, grid entry point voltage feedback signal vPCC_ofBy gain compensation function Gv2(s), obtain output signal vPCC_fund, Gv2(s)As shown in following formula (5),
Wherein, KrFor gain compensation function Gv2(s)Frequency-selecting bandwidth factor, ωnFor gain compensation function Gv2(s)Frequency-selecting angular frequency Rate, Kp2For gain compensation function Gv2(s)Gain；
S33, according to output signal vPCC_LLAnd vPCC_fund, phase regulator output signal V is obtained by following formula (7)r2,
Vr2=vPCC_LL+vPCC_fund (7)。
It is highly preferred that in step S31, output signal v is obtained by following formula (4)PCC_LL,
VPCC_LL=GvlXVPCC_of (4)
In step S32, output signal v is obtained by following formula (6)PCC_fund,
vPCC_fund=Gv2×vPCC_of (6)。
The another technical solution that the present invention uses is：
A kind of single-phase photovoltaic inverter that improves to the control system of the adaptability of light current net, including：
Voltage sample module, the voltage feedback signal v for obtaining grid entry pointPCC_of；
Current sampling module, the current feedback signal i for obtaining grid entry pointL_of；
Current controller, for according to voltage feedback signal vPCC_ofObtained electric network voltage phase θ and current reference base Quasi- I*It obtains inductive current and refers to iL_ref, and inductive current is referred into iL_refWith inductor current feedback signal iL_ofSubtract each other, passes through The adjusted signal v of current regulationr1；
PWM generators, the PWM drive signal for generating each switching tube of inverter；
The control system further includes：
Phase regulator, for grid entry point voltage feedback signal vPCC_ofCarry out the adjusted signal V of phasingr2；
The current controller is additionally operable to Regulate signal vr1With the Regulate signal Vr2It is superimposed to obtain modulated signal vm And it is sent into the PWM generators.
Preferably, the phase regulator includes：
First phase adjustment module, for grid entry point voltage feedback signal vPCC_ofIt carries out phase adjusted and obtains output letter Number vPCC_LL；
Second phase adjustment module, for grid entry point voltage feedback signal vPCC_ofIt carries out gain compensation and obtains output letter Number vPCC_fund；
Computing module is used for vPCC_LLAnd vPCC_fundIt is added adjusted signal Vr2。
The present invention uses above scheme, has the following advantages that compared with prior art：Without increasing additional voltage or electricity Flow sensor can inhibit net side LCL type resonance spikes；When electric network impedance wide range changes, control system still can protect It is fixed to keep steady, and keeps higher sine degree.The control method is by grid entry point voltage feedback signal vPCC_ofIt is superimposed to after being handled The output of current regulator, compensating sampling and control postpone, and realize to the phasing of grid entry point voltage feedback signal, improve Unidirectional photovoltaic DC-to-AC converter is to the adaptability of light current net, to realize the inverter stable operation off the net in light current.
Description of the drawings
Fig. 1 is the control system schematic diagram of existing single-phase photovoltaic inverter.
Fig. 2 is the control block diagram of existing single-phase photovoltaic inverter.
Fig. 3 is the control system schematic diagram of the single-phase photovoltaic inverter of the present invention.
Fig. 4 is the flow chart using control method provided by the present invention.
Fig. 5 is the experimental waveform figure using existing control method.
Fig. 6 is the experimental waveform figure using control method of the present invention.
Specific implementation mode
The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, so that advantages and features of the invention energy It is easier to be understood by the person skilled in the art.
With reference to shown in Fig. 3, a kind of raising single-phase photovoltaic inverter of the invention to the control system of the adaptability of light current net, Including voltage sample module, current sampling module, DC power supply 1, inverter bridge 2, LC filters 3, public electric wire net 4, current control Device 5, PWM generators 6, phase regulator 7.Wherein, voltage uses module by grid entry point voltage vPCCSensor VS1And grid entry point Voltage vPCCSampling processing circuit HvComposition, current sampling module is by inductive current iLSensor CS1With inductive current iLAt sampling Manage circuit composition, wherein HvAnd HiGenerally low-pass first order filter, according to HvAnd HiRespectively obtain grid entry point voltage feedback signal vPCC_ofWith inductor current feedback signal iL_of；Inverter 2 is by switch transistor T1~T4And sustained diode1~D4Composition；LC is filtered Device 3 is by filter inductance LoWith filter capacitor CoComposition；Public electric wire net 4 is by electric network impedance ZgWith network voltage source VgComposition；iL_of；θ To use voltage feedback signal vPCC_ofObtained grid entry point voltage-phase；I*For inductive current benchmark；iL_refFor inductive current With reference to；GiFor current regulator, generally use proportional plus integral control strategy.Current controller 5, for according to electric network voltage phase θ and current reference benchmark I*It obtains inductive current and refers to iL_ref, and inductive current is referred into iL_refBelieve with inductor current feedback Number iL_ofSubtract each other, by the adjusted signal v of current regulationr1；PWM generators 6, the PWM for generating each switching tube of inverter Drive signal；Phase regulator 7, for grid entry point voltage feedback signal vPCC_ofCarry out the adjusted signal V of phasingr2； Current controller is additionally operable to Regulate signal vr1With Regulate signal Vr2It is superimposed to obtain modulated signal vmAnd it is sent into PWM generators.
Specifically, phase regulator 7 includes：
First phase adjustment module Gv171, for grid entry point voltage feedback signal vPCC_ofProgress phase adjusted obtains defeated Go out signal vPCC_LL；
Second phase adjustment module Gv272, for grid entry point voltage feedback signal vPCC_ofProgress gain compensation obtains defeated Go out signal vPCC_fund；
Computing module 73 is used for vPCC_LLAnd vPCC_fundIt is added adjusted signal Vr2。
Control with reference to the raising single-phase photovoltaic inverter that shown in Fig. 4, above-mentioned control system uses to the adaptability of light current net Method processed, includes the following steps：
A kind of raising single-phase photovoltaic inverter includes the following steps the control method of the adaptability of light current net.
S1, the voltage feedback signal v for obtaining grid entry pointPCC_ofWith inductive current iL_of, voltage feedback signal vPCC_ofAdopt It is respectively H that sample, which postpones transmission function,v, inductive current iL_ofSampling delay transmission function be Hi。
S2, by feedback signal iL_ofSubstitute into the adjusted signal V of current regulatorr1, specially：
S21, according to the voltage feedback signal vPCC_ofElectric network voltage phase θ is obtained, further according to the electric network voltage phase θ and current reference benchmark I*, inductive current is obtained by following formula (1) and refers to iL_ref,
iL_ref=I*×sin(θ) (1)；
Inductive current is referred to i by S22, according to the following formula (2)L_refWith inductor current feedback signal iL_ofSubtract each other, through overcurrent The adjusted signal v of adjusterr1,
vr1=Gi×(iL_ref-iL_of) (2)。
S3, by feedback signal vPCC_ofSubstitute into the adjusted signal V of phase regulatorr2, specifically,
S31, grid entry point voltage feedback signal vPCC_ofBy phase adjusted function G shown in following formula (3)v1(s), by following formula (4) output signal v is obtainedPCC_LL,
VPCC_LL=Gv1×vPCC_of (4)
Wherein, Kp1For phase adjusted function gain,For phase adjusted function initial angular frequency,For phase adjusted letter Number terminates angular frequency, and α ＜ 1, s are Laplace operator；
S32, grid entry point voltage feedback signal vPCC_ofBy gain compensation function G shown in following formula (5)v2(s), by following formula (6) output signal v is obtainedPCC_fund,
vPCC_fund=Gv2×vPCC_of (6)
Wherein, KrFor gain compensation function Gv2(s)Frequency-selecting bandwidth factor, ωnFor gain compensation function Gv2(s)Frequency-selecting angular frequency Rate, Kp2For gain compensation function Gv2(s)Gain；
S33, according to output signal vPCC_LLAnd vPCC_fund, phase regulator output signal V is obtained by following formula (7)r2,
Vr2=vPCC_LL+vPCC_fund (7)。
S4, by Vr1And Vr2Addition obtains modulated signal vm, and PWM generators are sent into, generate the PWM of each switching tube of inverter Drive signal.vmCalculation formula such as following formula (8),
vm=vr1+vr2 (8)。
Comparative illustration, the example are carried out to the control method of control method in the prior art and the present invention with an example Major parameter it is as follows：
1 voltage V of DC power supplyin=360V；
4 voltage V of public electric wire netg=230V；
Rated power Po=3000W；
Switching frequency fs=20kHz；
Filter inductance Lo=1.56mH；
Filter inductance Co=4.7 μ F；
Grid entry point voltage signal sampling modulate circuit transmission function
Inductor current signal over-sampling modulate circuit transmission function
Public electric wire net voltage is simulated using Programmable AC Power Source, sets network voltage as Vg=230V, sine degree are good； Using tandem electric inductance come simulating grid impedance.Result is as follows under different control methods：
The experimental waveform figure of existing control method used by existing control system shown in FIG. 1 is as shown in Figure 5.Wherein The experimental waveform of Fig. 5 (a), 5 (b), 5 (c) respectively when electric network impedance is 0.8mH, 2.0mH, 3.6mH.Due to sampling and control The presence of delay is made, grid entry point voltage feedforward control method in the prior art fails preferably to carry out active damping control, inverse Becoming device output current wave, there are the higher-orders of oscillation, and overcurrent may be triggered when serious, causes delay machine phenomenon
The experimental waveform figure of control method used by control system of the present invention shown in Fig. 3 is as shown in Figure 6.Wherein Fig. 6 (a), the experimental waveform of 6 (b), 6 (c) respectively when electric network impedance is 0.8mH, 2.0mH, 3.6mH.Very due to phase regulator The good sampling that compensates for postpones with control, and grid entry point voltage feedforward control method preferably carries out active damping control, and inverter is defeated Go out current waveform without the higher-order of oscillation.Therefore when electric network impedance changes from 0.8mH to 3.6mH, the equal the operation is stable of inverter, effectively Demonstrate the practicability of control method of the present invention.
The above embodiments merely illustrate the technical concept and features of the present invention, is a kind of preferred embodiment, and purpose exists It cans understand the content of the present invention and implement it accordingly in person skilled in the art, the protection of the present invention can not be limited with this Range.Equivalent transformation or modification made by all Spirit Essences according to the present invention, should all cover protection scope of the present invention it It is interior.
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| 基于改进锁相环的单相光伏并网逆变器研制;杨恢宏等;《电力电子技术》;20110731;第45卷(第7期);第11-13页 * |
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