CN104518651B - Light current three-phase LCL type combining inverter current harmonics off the net suppresses control method - Google Patents

Light current three-phase LCL type combining inverter current harmonics off the net suppresses control method Download PDF

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CN104518651B
CN104518651B CN201410508269.0A CN201410508269A CN104518651B CN 104518651 B CN104518651 B CN 104518651B CN 201410508269 A CN201410508269 A CN 201410508269A CN 104518651 B CN104518651 B CN 104518651B
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CN104518651A (en
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李巍巍
许树楷
朱喆
陈俊
黎小林
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Research Institute of Southern Power Grid Co Ltd
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Power Grid Technology Research Center of China Southern Power Grid Co Ltd
Research Institute of Southern Power Grid Co Ltd
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Abstract

The present invention is that a kind of light current three-phase LCL type combining inverter current harmonics off the net suppresses control method, and step is current sensor detection capacitance current i 1. using filter capacitor and inductanceCxWith grid-connected current iL2x, gather and carry out coordinate transform and obtain feedback signal iC_of_mAnd iL2_of_m；2. public grid-connected point voltage v is detected using grid voltage sensorpccx, gather and carry out coordinate transform and obtain sampled signal vpcc_of_m, by vpcc_of_mSend into line voltage pre-filtering block Gpcc_pfObtain vpcc_f_m；3. by vpcc_f_mSend into voltage feed-forward control function Gpcc_fdObtain feed-forward signal vpcc_fd_m；4. according to iL2_of_mAnd iref_m, calculate error signal e1m：5. controller is to e1mClosed loop is carried out, i is obtainedC_of_mReference signal iC_ref_m；Error signal e2m=iC_ref_m+vpcc_fd_m‑iC_of_m；6. utilize e2m, generate the pwm control signal of converter bridge switching parts pipe.The present invention solves the instability problem of light current combining inverter off the net, and can suppress the grid-connected current harmonic wave that line voltage produces, and during unbalanced power supply, inverter still can be to the electric current of electrical network injection balance.

Description

Light current three-phase LCL type combining inverter current harmonics off the net suppresses control method
Technical field
The invention belongs to the control technology field of combining inverter, (grid short circuit capacity in the case of referring to light current net Less, containing larger internal impedance) a kind of suppression line voltage control method that grid-connected current waveform quality is affected.
Background technology
In actual electric network, line voltage in addition to fundamental frequency component, also containing harmonic wave and unbalanced component.Line voltage Fundametal compoment can affect the harmonic component of the phase place of grid-connected current, line voltage that grid-connected current can be caused to distort, line voltage Unbalanced component can cause the imbalance of three-phase grid electric current.In order to ensure that combining inverter exports the waveform matter of grid-connected current Amount, generally suppresses impact of the line voltage to grid-connected current using the method for control.
Fig. 1 is the structure chart of three-phase LCL type combining inverter.LCL type combining inverter includes DC source 1, inverter bridge 2, LCL filter 3, public electric wire net 4, controller 5 and feedforward module 6.Wherein, inverter bridge 2 is by switching tube S1～S6With it is continuous Stream diode D1～D6Composition；LCL filter 3 is by filter inductance L1, L2Constitute with filter capacitor C.Hi1And Hi2Respectively detect Capacitance current and filter inductance L2Grid-connected current sensor, Hv2For network voltage detection sensor.
In the structure of fig. 1, to the input grid-connected current instruction of controller 5 and Jing current sensor Hi2Obtain flowing through filtering Inductance L2Grid-connected current.The three-phase current that detection is obtained is carried out coordinate transform and (is changed by abc coordinate systems by controller 5 first To α β coordinate systems), the electric network voltage phase information for then being obtained according to phaselocked loop provides the command value of grid-connected current, eventually passes Grid-connected current closed-loop control and feedforward module 6 realize that grid-connected current suppresses to the tracking harmonic of command value.
Herein, the controller 5 and feedforward module 6 of combining inverter are specifically described.It is tied to through abc coordinates After the conversion of α β coordinate systems, controller 5 carries out closed loop control, detection sensor H in α axles and β axles respectivelyv2Detect electrical network electricity Pressure, and try to achieve its phase angle θm(all subscript m=α, β herein), electric network voltage phase angle θmInstruct what is provided to have with grid-connected current Valid value I*Actual command value i of grid-connected current is constituted togetherref_m。iref_mWith current sensor Hi2The grid-connected current signal of detection Subtract each other, the error signal for obtaining sends into actuator Gi, its output signal is used as current sensor Hi1The capacitance current that detection is returned The command value of signal, the voltage feed-forward control signal v that their error signal is exported with feedforward module 6g_fd_mSend after addition Enter in pulse width modulation (Pulse Width Modulation, PWM) device, obtain the control signal of 2 each switching tube of inverter bridge.
However, in the construction shown in fig. 1, utility network 4 is processed as voltage source, is not considered engineering reality Utility network internal impedance Z in bordergImpact.Therefore, for the larger light current of electrical network internal impedance such as remote districts of electrical network end Net situation, can not effectively suppress light current electrical network electricity off the net using the controller 5 and feedforward module 6 in structure shown in Fig. 1 Impact of the pressure to grid-connected current waveform quality, resulting even in combining inverter cannot steady operation.
The content of the invention
It is an object of the invention to provide a kind of light current three-phase LCL type combining inverter current harmonics off the net suppresses controlling party Method.The control method considers utility network internal impedance ZgImpact, in the case of solving light current net, electrical network internal impedance ZgCause Three-phase LCL type combining inverter instability problem；In the case of light current net is ensured while combining inverter steady operation, can be with Effectively suppress impact of the line voltage to grid-connected current waveform quality.
A kind of light current three-phase LCL type combining inverter current harmonics off the net that the present invention is provided suppresses control method, the party Method comprises the steps：
1) using the current sensor H of capacitance currenti1Detection capacitance current iCx, gather and carry out coordinate transform and obtain electricity Capacitance current feedback signal iC_of_m；Using the current sensor H of filter inductancei2Detection grid-connected current iL2x, gather and carry out coordinate Conversion, obtains grid-connected current feedback signal iL2_of_m；Wherein, subscript x represents a, b, c three-phase, m represent α axles in α β coordinate systems, Beta -axis component；
2) using the voltage sensor H of line voltagev2Detect public grid-connected point voltage vpccx, gather and carry out coordinate transform Obtain public grid entry point voltage sampling signal vpcc_of_m, by vpcc_of_mSend into line voltage pre-filtering block Gpcc_pfCalculate To vpcc_f_m；
3) by vpcc_f_mSend into voltage feed-forward control function Gpcc_fdIt is calculated voltage feed-forward control signal vpcc_fd_m；
4) according to current feedback signal iL2_of_mAnd its reference signal iref_m, error signal e is calculated using Formulas I1m：
e1m=iref_m-iL2_of_m (1)
5) controller is to error signal e1mClosed-loop process is carried out, capacitor current feedback signal i is obtainedC_of_mReference signal iC_ref_m；Using Formula II error signal e2m；
e2m=iC_ref_m+vpcc_fd_m-iC_of_m (2)
6) utilize error signal e2m, generate the pwm control signal for obtaining controlling converter bridge switching parts pipe；
7) controller judges whether to receive fault-signal；If it is, shutdown, otherwise, proceeds to step 1).
The control method that the present invention is provided sends into line voltage pre-filtering block by the sample information by line voltage Calculated, and the result of calculation for obtaining is feedovered into controller by certain functional relationship, can be with effectively solving light current net In the case of, electrical network internal impedance ZgThe combining inverter instability problem for causing, suppresses line voltage to grid-connected current waveform quality Impact.In a word, the control method can improve the stability in the case of combining inverter accesses light current net, improve networking power Factor, it is ensured that grid-connected current waveform quality is good, is still capable of achieving inverter flat to electrical network injection when three-phase power grid voltage is uneven The electric current of weighing apparatus.
Description of the drawings
Fig. 1 is the structural representation of existing typical three-phase LCL type combining inverter；
Fig. 2 be the present invention provide control method a kind of specific embodiment flow chart, x=a in figure, b, c, m= α, β；
Fig. 3 is the structural representation of the three-phase LCL type combining inverter using control method shown in Fig. 2；
Fig. 4 is the block diagram of the three-phase LCL type combining inverter shown in Fig. 3, in figure, m=α, β；
Fig. 5 is the G in the line voltage prefilter 7 shown in Fig. 4pcc_pfStructure realize schematic diagram, wherein, R1,R2 And RnThe respectively corresponding resonant element of line voltage each harmonic component, Kf_1,Kf_2And Kf_nRespectively each time of line voltage is humorous The proportionality coefficient of wave component.
Fig. 6 is that the structure of the three-phase LCL type combining inverter shown in Fig. 4 realizes schematic diagram；
Specific embodiment
The invention will be further described with specific embodiment below in conjunction with the accompanying drawings.
As shown in Fig. 2 control method provided by the present invention comprises the steps：
1) using the current sensor H of capacitance currenti1Detection capacitance current iCx, gather and carry out coordinate transform and obtain electricity Capacitance current feedback signal iC_of_m；Using the current sensor H of filter inductancei2Detection grid-connected current iL2x, gather and carry out coordinate Conversion, obtains grid-connected current feedback signal iL2_of_m；Wherein, subscript x represents a, b, c three-phase, m represent α axles in α β coordinate systems, Beta -axis component；
2) using the voltage sensor H of line voltagev2Detection PCC point voltage vpccx, gather and carry out coordinate transform and obtain Public grid entry point voltage sampling signal vpcc_of_m, by vpcc_of_mSend into line voltage pre-filtering block Gpcc_pfIt is calculated vpcc_f_m；
3) by vpcc_f_mSend into voltage feed-forward control function Gpcc_fdIt is calculated voltage feed-forward control signal vpcc_fd_m；
4) according to current feedback signal iL2_of_mAnd its reference signal iref_m, error signal e is calculated using Formulas I1m：
e1m=iref_m-iL2_of_m (1)
5) controller is to error signal e1mClosed-loop process is carried out, capacitor current feedback signal i is obtainedC_of_mReference signal iC_ref_m；Using Formula II error signal e2m；
e2m=iC_ref_m+vpcc_fd_m-iC_of_m (2)
6) utilize error signal e2m, generate the pwm control signal for obtaining controlling converter bridge switching parts pipe；
7) controller judges whether to receive fault-signal；If it is, shutdown, otherwise, proceeds to step 1).
As shown in figure 3, above-mentioned control method is realized by increasing line voltage pre-filtering block 7 in the controller 5. Controller 5, feedforward module 6 and line voltage pre-filtering block 7 are realized by microprocessor, and microprocessor can be adopted With digital signal processing chips such as DSP or ARM.
Microprocessor collection voltages sensor Hv2The voltage signal and current sensor H of outputi1And Hi2The electric current letter of output Number, the pwm signal of six switching tubes of control inverter bridge 2 is produced after the relative program computing in microprocessor.
Fig. 4 is the block diagram of the three-phase LCL type combining inverter shown in Fig. 3.Wherein, GiFor regulating error device, generally adopt Use proportional-integral controller.GinvFor the gain of inverter bridge 2, vinv_mFor 2 output voltage of inverter bridge.k1,k2And k3Respectively electric capacity Electric current iCm, grid-connected current iL2mWith line voltage vgpccDownsampling factor, its size depend on A/D sampling A/D chips, according to sampling system Number k1、k2And k3Respectively obtain capacitor current feedback signal iC_of_m, grid-connected current feedback signal iL2_of_mWith PCC point line voltages Sampled signal vpcc_of_m。ZL1,ZCAnd ZL2Respectively filter inductance L1, filter capacitor C and filter inductance L2Impedance.Gpcc_pfFor Line voltage pre-filtering function, Gpcc_fdFor voltage feed-forward control function, vpcc_fd_mTo gather before calculated line voltage Feedback signal.
iref_mFor grid-connected current feedback signal iL2_of_mReference signal, e1mIt is the error signal obtained according to Formulas I.e1m Jing regulating error device GiAfter obtain capacitor current feedback signal iC_of_mReference signal iC_ref_m, reference signal iC_ref_m, electric capacity Current feedback signal iC_of_mWith voltage feed-forward control signal vpcc_fd_mMeridional II obtains error signal e2m, using error signal e2m, the pwm control signal of control 2 switching tube of inverter bridge can be generated, that is, obtains 2 output voltage v of inverter bridgeinv_m。vinv_mJing Grid-connected current i is obtained after LCL filter 3L2m。
As shown in figure 5, when implementing the line voltage pre-filtering block in Fig. 4, first to sending into the pre-filtering PCC point voltage sampled signals v of modulepcc_of_mThe extraction of each component of degree n n is carried out, v is obtainedp1_m、vp1_mAnd vpn_mDeng.To extract The each component of degree n n v for arrivingp1_m、vp1_mAnd vpn_mDeng being multiplied by COEFFICIENT K respectivelyf_1、Kf_2And Kf_n, obtain each time after pre-filtering Component vp1_f_m、vp1_f_mAnd vpn_f_mDeng.By vp1_f_m、vp1_f_mAnd vpn_f_mEtc. adding up, line voltage pre-filtering mould is obtained Final output signal v of blockpcc_f_m。
As shown in fig. 6, when implementing the square frame shown in Fig. 4, increasing a pll controller 8, its effect is to ensure Grid-connected current iL2mWith line voltage vpccmSame phase, their phase angle are θm.According to phase angle θm, the sine in microcontroller What table and grid-connected current were instructed is effectively worth to grid-connected current iL2mReference signal iref_m。

Claims (1)

1. a kind of light current three-phase LCL type combining inverter current harmonics off the net suppresses control method, it is characterised in that the method bag Include following steps：
1) using the current sensor H of capacitance currenti1Detection capacitance current iCx, gather and carry out coordinate transform and obtain capacitance current Feedback signal iC_of_m；Using the current sensor H of filter inductancei2Detection grid-connected current iL2x, coordinate transform is gathered and is carried out, is obtained To grid-connected current feedback signal iL2_of_m；Wherein, subscript x represents a, b, c three-phase, and m represents α axles in α β coordinate systems, β axles point Amount；
2) using the voltage sensor H of line voltagev2Detect public grid-connected point voltage vpccx, gather and carry out coordinate transform and obtain Public grid entry point voltage sampling signal vpcc_of_m, by vpcc_of_mSend into line voltage pre-filtering block Gpcc_pfIt is calculated vpcc_f_m；
3) by vpcc_f_mSend into voltage feed-forward control function Gpcc_fdIt is calculated voltage feed-forward control signal vpcc_fd_m；
4) according to current feedback signal iL2_of_mAnd its reference signal iref_m, error signal e is calculated using formula (1)1m：
e1m=iref_m-iL2_of_m (1)
5) controller is to error signal e1mClosed-loop process is carried out, capacitor current feedback signal i is obtainedC_of_mReference signal iC_ref_m；Using formula (2) error signal e2m；
e2m=iC_ref_m+vpcc_fd_m-iC_of_m (2)
6) utilize error signal e2m, generate the pwm control signal for obtaining controlling converter bridge switching parts pipe；
7) controller judges whether to receive fault-signal；If it is, shutdown, otherwise, proceeds to step 1)；
2) above-mentioned steps specifically include following steps：
21) using the voltage sensor H of line voltagev2Detection PCC point voltage vpccx, gather and carry out coordinate transform and obtain PCC Point voltage sampled signal vpcc_of_m, by vpcc_of_mSend into line voltage pre-filtering block Gpcc_pf；
22) in line voltage pre-filtering block Gpcc_pfIn, first to vpcc_of_mHarmonic component extraction is carried out, electrical network electricity is obtained Corresponding harmonic component v of pressurep1_m, vp2_mAnd vpn_m；
23) by the Voltage Harmonic component v for obtainingp1_m, vp2_mAnd vpn_mProportional coefficient K is corresponded to etc. being multiplied byf_1,Kf_2And Kf_nDeng And sum up, obtain line voltage prefilter Gpcc_pfOutput signal vpcc_f_m。
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CN105529724A (en) * 2015-09-23 2016-04-27 镇江长河电力技术有限公司 Current tracking control method suitable for SVG dynamic reactive compensation device
CN106300354B (en) * 2016-09-21 2018-09-28 南京航空航天大学 A kind of adaptive voltage feed-forward control compensation method of grid-connected converter
CN109687754B (en) * 2019-01-30 2020-07-24 东北电力大学 Self-adaptive three-phase L C L grid-connected inverter control method

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