CN103457272A - Method for controlling capacitance-split-type three-phase four-wire static synchronous compensator - Google Patents

Abstract

The invention relates to a method for controlling a capacitance-split-type three-phase four-wire static synchronous compensator. The method includes the steps that a fundamental wave active current component in a load current is detected, and voltage stabilizing control on a direct current side and voltage equalizing control on the direct current side are achieved on a voltage outer loop; the load current ILabc subtracts the fundamental wave positive sequence active current component ILfabc to obtain a tracking instruction of a current inner-loop double-loop controller, and the tracking instruction of the current inner-loop double-loop controller subtracts a current generated by the static synchronous compensator to obtain a deviation current; the deviation current is input into the current inner-loop double-loop controller, a system dynamic response speed is improved through an inner loop PI controller in the current inner-loop double-loop controller; the current tracking accuracy is improved through an outer loop repetitive controller in the current inner-loop double-loop controller. The current inner-loop double-loop controller achieves current control in the mode that the inner loop PI controller is embedded in the outer loop repetitive controller.

Description

A kind of electric capacity Split type three-phase four-wire system STATCOM control method

Technical field

The present invention relates to the static synchroballistic control method in the electric power quality reactive power compensation, particularly relate to a kind of electric capacity Split type three-phase four-wire system STATCOM control method.

Background technology

In recent years, along with social fast development, the user is more and more higher to the requirement of the quality of power supply, and in power distribution network, the large capacity impact asymmetric load such as arc furnace, rolling mill, electric railway has brought great pollution to electrical network, and this will have influence on normal, the safe operation of power consumption equipment.STATCOM is as a kind of advanced person, the desirable reactive power compensator of performance, can the effective compensation reactive power, improve the quality of power supply.Compare traditional Static Var Compensator (SVC), STATCOM has better dynamic responding speed and significant economic benefit, thereby is widely used.

Wider topological structure position phase separation structure and three-phase four-wire system four bridge arm structures are used in the reactive power compensation of threephase load asymmetric system, but this configuration switches device is more, cost is too high, for the low capacity occasion, three-phase four-wire system electric capacity Split type structure, the hardware less investment, cost is low, has more commercial application value.Yet adopt at present maximum control methods mostly to be the two closed loop control methods based on the PI controller, this method has higher dynamic responding speed, but the limited bandwidth of PI controller, to idle, harmonic wave etc., periodically the signal trace performance is undesirable, and stable state accuracy is not high.

Summary of the invention

Follow the tracks of dynamic property and stable state accuracy problem for electric capacity Split type three-phase four-wire system STATCOM, the present invention proposes a kind of electric capacity Split type three-phase four-wire system STATCOM control method, comprise the following steps:

S1: the instruction current detection, detect the load current I of the static synchronous compensation circuit of an electric capacity Split type three-phase four-wire system _labcmiddle fundamental positive sequence active current component I _lfabc, simultaneously, outer voltage controls by regulation loop PI controller and grading ring PI controller voltage stabilizing control and the Pressure and Control that realize the static synchronous compensation circuit DC side of described electric capacity Split type three-phase four-wire system;

S2: described load current I _labcdeduct described fundamental positive sequence active current component I _lfabcas the trace command of current inner loop dual-loop controller, the trace command of described current inner loop dual-loop controller deducts the electric current that in the static synchronous compensation circuit of described electric capacity Split type three-phase four-wire system, STATCOM occurs and obtains the deviation electric current;

S3: the described deviation electric current produced in S2 is inputted to described current inner loop dual-loop controller, in described current inner loop dual-loop controller, encircle the PI controller, improve the system dynamic responding speed; By described current inner loop dual-loop controller outer-loop repetitive controller, improve the current tracking precision; Wherein, the mode that described current inner loop dual-loop controller adopts described interior ring PI controller to be embedded in described outer shroud repetitive controller realizes.

As preferably, step S1 further comprises:

Described electric capacity Split type three-phase four-wire system STATCOM circuit comprises distribution system, described STATCOM and load, and it is equivalent to three independently single-phase semi-bridge inversion circuit; Described STATCOM structure adopts the LCL filter;

In the instruction current detection, described regulation loop PI controller, by the difference of feedback regulation DC voltage reference value and DC voltage actual value, is realized the voltage stabilizing of the first DC bus capacitor and the second DC bus capacitor is controlled; Described grading ring PI controller, according to the positive negativity of the voltage difference of the first DC bus capacitor described in circuit and described the second DC bus capacitor, produces a zero sequence adjusting current-order i of opposite direction with it _0refafter, carry out three-dimensional dq0/abc rotational coordinates inverse transformation and obtain the abc three-phase instruction current that comprises zero-sequence component, by described zero-sequence current being carried out to the Pressure and Control of FEEDBACK CONTROL realization to described the first DC bus capacitor and described the second DC bus capacitor.

As preferably, step S3 further comprises, described deviation electric current by described current inner loop dual-loop controller, regulate after output valve and the switch command of feedforward component stack as edge grid bipolar transistor in STATCOM.

As preferably, described feedforward component is distribution system voltage.

As preferably, shown in step S3, the transfer function of described repetitive controller is: $C_{\mathrm{im}}\left(z\right)=\frac{c\left(z\right)}{e\left(z\right)}=\frac{1}{1-Q\left(z\right)z^{-N}}$

Q in formula (z) is for strengthening the extension filter of system robustness, and e is error signal, and N is the internal mold step-length, and c (z) is the control signal of internal mold output, and the error signal e of repetitive controller (z) is:

$e\left(z\right)=\frac{(1-Q\left(z\right)z^{-N})(1-P\left(z\right))}{1-z^{-N}(Q\left(z\right)-z^{k}S\left(z\right)P\left(z\right))}{i}_r\left(z\right)$

In formula, i _rfor reference signal, S (z) is low pass filter, z ^kfor phase compensator, P (z) is the discretization model that the interior ring after described interior ring PI controller is proofreaied and correct is controlled transfer function:

$P\left(z\right)=\frac{G_{\mathrm{LCL}}\left(z\right)\·G_{\mathrm{PI}}\left(z\right)}{1+G_{\mathrm{LCL}}\left(z\right)\·G_{\mathrm{PI}}\left(z\right)}$

In formula, G _lCL(s) transfer function of LCL filter:

$G_{\mathrm{LCL}}\left(s\right)=\frac{1}{({\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HDA0000370995610000031.png,HDA0000370995610000052.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="2013103740728100003DEST\_PATH\_IMAGE002.png,HDA0000370995610000022.png"\; state="\{\{state\}\}">L</figure-callout>}}_2+L_s)s+R}$

In formula, L _sfor electrical network equivalent inductance, L ₁for net side filter inductance, L ₂for inverter side filter inductance, the equiva lent impedance that R is described LCL filter circuit, described interior ring PI controller transfer function is:

k in formula _p, K _ibe respectively proportionality coefficient and the integral coefficient of PI controller;

Wherein, described auxiliary compensator Q (z) gets the constant that is less than 1, and described low pass filter S (z) adopts second order filter, described phase compensator z ^kthe phase delay of comprehensive P (z) and S (z) is chosen.

The present invention, owing to adopting above technical scheme, makes it compared with prior art, has following advantage and good effect:

1) a kind of electric capacity Split type three-phase four-wire system STATCOM control method provided by the invention, the double loop control that is applied to electric capacity division three-phase four-wire system STATCOM of design combines the advantage of repetitive controller and conventional PI control device, improved the bandwidth of controller, can respond fast current-order, there is higher stable state accuracy.

2) a kind of electric capacity Split type three-phase four-wire system STATCOM control method provided by the invention, outer voltage realizes the Pressure and Control of DC bus capacitor and the voltage stabilizing control of electric capacity.

The accompanying drawing explanation

Fig. 1 is electric capacity Split type three-phase four-wire system STATCOM topological structure;

Fig. 2 is three-phase four-wire system STATCOM equivalence single-phase grid-connection inverter circuit

The Pressure and Control that Fig. 3 is split capacitor;

Fig. 4 is the electric capacity Split type three-phase four-wire system STATCOM control method based on dual-loop controller;

Fig. 5 is Double Loop Control System;

The nyquist plot that Fig. 6 is H (z);

Fig. 7 a is the front asymmetric load electric current of compensation;

Fig. 7 b is system power waveform after the double loop control compensation;

Fig. 8 is system power aberration rate after the double loop control compensation;

Fig. 9 a be the experimental prototype current waveform and and mutual relation of electric voltage;

Fig. 9 b be the experimental prototype current waveform and and mutual relation of electric voltage;

Figure 10 experimental prototype current distortion rate;

Figure 11 is that a kind of electric capacity Split type three-phase four-wire system STATCOM provided by the invention is controlled method

Flow chart.

Wherein: U _sa, U _sb, U _scbe respectively the abc axle component of line voltage;

T _a1, T _a2, T _b1, T _b2, T _c1, T _c2for switching device IGBT (Insulated Gate Bipolar Transistor), i.e. insulated gate bipolar transistor;

U _dcreffor DC voltage reference value, U _dcfor DC voltage actual value, C _dc1be the first DC bus capacitor, C _dc2it is the second DC bus capacitor;

I _eerA, I _eerB, I _eerCbe respectively deviation electric current abc axle component;

I _lfd, I _lfq, I _lf0be respectively fundamental positive sequence active current component I _lfabcdo d, q, 0 axle component that the dq0/abc inverse transformation obtains;

LPF is low pass filter.

Embodiment

Further illustrate the present invention with specific embodiment with reference to the accompanying drawings.

Referring to the accompanying drawing that the embodiment of the present invention is shown, hereinafter the present invention will be described in more detail.Yet the present invention can be with many multi-form realizations, and should not be construed as the restriction of the embodiment be subject in this proposition.On the contrary, it is abundant and complete open in order to reach proposing these embodiment, and makes those skilled in the art understand scope of the present invention fully.

Below in conjunction with drawings and Examples, the present invention is described in detail.

As accompanying drawing 1-5, shown in 11, a kind of electric capacity Split type three-phase four-wire system STATCOM control method, comprise the following steps:

S1: the instruction current detection, detect the load current I of the static synchronous compensation circuit of an electric capacity Split type three-phase four-wire system _labcmiddle fundamental active current component I _lfabc, simultaneously, outer voltage 2 is controlled and is realized the capacitance voltage stabilizing of the static synchronous compensation circuit DC side of electric capacity Split type three-phase four-wire system is controlled and capacitor voltage equalizing control by regulation loop PI controller 21 and grading ring PI controller 22.

An electric capacity Split type three-phase four-wire system STATCOM circuit as shown in Figure 1, comprising: distribution system 11, STATCOM 12 and load 13.Adopt the LCL filter in this circuit, had than the better performance of single inductance filter, can take into account low-band gain and high band decay.In figure, C is filter capacitor, and introducing capacitive branch is in order to high fdrequency component, to provide low impedance path.L ₁for net side filter inductance, form parallel circuits with C the switching device ripple component is shunted.L ₂for the inverter side filter inductance.The rush of current brought in order to reduce capacitive branch, the passive damping resistance R of series connection on capacitive branch _dincrease capacitive reactance.

Known referring to accompanying drawing 1, the STATCOM of electric capacity Split type three-phase four-wire system is a non-coupled system that three-phase is separate, it can be equivalent to three independently single-phase semi-bridge inversion circuit, its grid-connected equivalent inverter circuit as shown in Figure 2, u in figure _ifor inverter bridge output AC voltage, u _sfor line voltage, L _sfor electrical network equivalent inductance, L ₁for net side filter inductance, R ₁for L ₁equivalent resistance, L ₂for inverter side filter inductance, R ₂for L ₂equivalent resistance, C is filter capacitor, R _dfor capacitive branch resistance.

From accompanying drawing 2, the static synchronous compensation circuit of electric capacity Split type three-phase four-wire system can equivalence become three independently single-phase semi-bridge inversion circuit, and each is independent of each other between mutually, therefore can realize that the three-phase under the abc coordinate system independently controls.The control structure of A, B, C three-phase is identical, and adopt two Closed-loop Cascade control structures of outer voltage and current inner loop dual-loop controller: outer voltage is DC side regulation loop and grading ring, in order to realize DC side total voltage balance and split capacitor electric voltage equalization.The current inner loop dual-loop controller is the transient current feedback control loop, and in order to carry out the instruction current tracking, as shown in Figure 5, concrete grammar has concrete elaboration in step S2 and S3 to the overall control block diagram hereinafter.

According to the basic principle of LCL filter, can regard the LCL circuit as: L ₁after branch road and capacitive branch C parallel connection again with L ₂series connection, i ₁be exactly L ₁branch road and capacitive branch are to i ₂shunting.The filter Mathematical Modeling is as follows:

Total series impedance:

$X_s={\mathrm{<figure-callout\; id="2"\; label="sL"\; filenames="2013103740728100003DEST\_PATH\_IMAGE002.png,HDA0000370995610000022.png"\; state="\{\{state\}\}">sL</figure-callout>}}_2+R_2+{\mathrm{<figure-callout\; id="1"\; label="X\; L"\; filenames="HDA0000370995610000031.png,HDA0000370995610000052.png"\; state="\{\{state\}\}">X</figure-callout>}}_{L_{}}---\left(1\right)$

Net side inductance L ₁with capacitive branch, there is divided relation in C, so current on line side i ₁for

${\mathrm{<figure-callout\; id="1"\; label="i"\; filenames="HDA0000370995610000031.png,HDA0000370995610000052.png"\; state="\{\{state\}\}">i</figure-callout>}}_1=\frac{u_i}{X_s}\&times;\frac{X_C}{X_C+X_{L_1}}---\left(2\right)$

Inverter circuit output voltage u _ito current on line side i ₁transfer function G (s) be

$G\left(s\right)=\frac{i_1}{u_i}---\left(3\right)$

Generally, the equivalent resistance of inductance is less, for simplifying the analysis it is ignored here, brings formula (1), (2) into formula (3), can obtain:

$G\left(s\right)=\frac{R_d\mathrm{Cs}+1}{L_1{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="2013103740728100003DEST\_PATH\_IMAGE002.png,HDA0000370995610000022.png"\; state="\{\{state\}\}">L</figure-callout>}}_2{\mathrm{<figure-callout\; id="3"\; label="Cs"\; filenames="HDA0000370995610000021.png,HDA0000370995610000022.png"\; state="\{\{state\}\}">Cs</figure-callout>}}^3+({\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HDA0000370995610000031.png,HDA0000370995610000052.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+L_2){\mathrm{<figure-callout\; id="2"\; label="R\; d\; Cs"\; filenames="2013103740728100003DEST\_PATH\_IMAGE002.png,HDA0000370995610000022.png"\; state="\{\{state\}\}">R</figure-callout>}}_d{\mathrm{Cs}}^{}{}^2+({\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HDA0000370995610000031.png,HDA0000370995610000052.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+L_2)s}---\left(4\right)$

From formula (4), the transfer function of LCL filter is third-order system, but considers that its low-frequency range and single inductor models approach, so adopt the transfer function of single inductance to replace the LCL model, wherein R is the circuit equiva lent impedance.

$G_{\mathrm{LCL}}\left(s\right)=\frac{1}{({\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HDA0000370995610000031.png,HDA0000370995610000052.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="2013103740728100003DEST\_PATH\_IMAGE002.png,HDA0000370995610000022.png"\; state="\{\{state\}\}">L</figure-callout>}}_2+L_s)s+R}---\left(5\right)$

Conventional PI control device transfer function is

k in formula _p, K _ibe respectively proportionality coefficient, the integral coefficient of PI controller.So just can obtain the closed loop transfer function, of current inner loop dual-loop controller under conventional PI control:

$G_1\left(s\right)=\frac{G_{\mathrm{LCL}}\left(s\right)\&CenterDot;G_{\mathrm{PI}}\left(s\right)}{1+G_{\mathrm{LCL}}\left(s\right)\&CenterDot;G_{\mathrm{PI}}\left(s\right)}---\left(6\right)$

The instruction current detection is the important component part of three-phase four-wire system STATCOM control system, to idle and real-time accuracy of detection unsymmetrical current, is the important prerequisite of assurance device compensation effect.

As shown in accompanying drawing 4-5, in the instruction current detection, regulation loop PI controller is by feedback regulation DC voltage reference value U _dcrefwith DC voltage actual value U _dcdifference, make voltage stabilization; Grading ring PI controller is according to first division capacitance voltage U in circuit _dc1with the second split capacitor voltage U _dc2poor positive negativity, produce a zero sequence adjusting current-order i of opposite direction with it _0refafter, carry out three-dimensional dq0/abc rotational coordinates inverse transformation and obtain the three-phase instruction current that comprises zero-sequence component, by zero-sequence current being carried out to the Pressure and Control of FEEDBACK CONTROL realization to split capacitor.The detection of instruction current is generally and adopts sample circuit to realize.

S2: described load current I _labcdeduct described fundamental positive sequence active current component I _lfabcas the trace command of current inner loop dual-loop controller 3, the trace command of current inner loop dual-loop controller 3 deducts the electric current I that STATCOM occurs _cabcdeviation electric current (the I obtained _eerA, I _eerB, I _eerC).

Load current I _labcin contain positive sequence asymmetrical component, negative phase-sequence asymmetrical component, zero-sequence component and harmonic component.Here detect the positive sequence real component I of 50Hz _lfabc, then with load current I _labcdo after differing from the trace command of the summation of the reactive current component, negative phase-sequence asymmetrical component and the harmonic component that obtain positive sequence as the current inner loop dual-loop controller.

S3: by the deviation electric current (I produced in S2 _eerA, I _eerB, I _eerC) the interior ring of input current dual-loop controller 3, encircle PI controller 32 in current inner loop dual-loop controller 3, improve the system dynamic responding speed; By current inner loop dual-loop controller 3 outer-loop repetitive controllers 31, improve the current tracking precision; Wherein, current inner loop dual-loop controller 3 adopts dual-loop controller, and the conventional PI control device is embedded in repetitive controller and forms dual-loop controller.

As shown in Figure 5, deviation electric current (I _eerA, I _eerB, I _eerC) output valve after current inner loop dual-loop controller 3 is regulated and the switch command 4 of corresponding feedforward component stack as edge grid bipolar transistor in described STATCOM.Here adopt line voltage (U _sa, U _sb, U _sc) as the feedforward component, be conducive to improve the dynamic property of system and reduce the impact to DC side while boosting.

Because interior ring control component is mainly alternating current component, therefore traditional PI controller can't meet steady-state tracking precision, need here the current inner loop controller is improved to improve the current inner loop control precision.Repetitive controller based on internal model principle, remarkable for the Rejection of Cyclic Disturbances effect, there is very high stable state accuracy.But repetitive controller is to take power frequency period, as step-length, error signal is regulated to correction, causes dynamic process longer, and dynamic response is slower.And aforesaid PI control method can be carried out summary responses to error, dynamic responding speed is much better than and repeats to control, but stable state accuracy can not be satisfactory.For guarantee that precision that current inner loop is followed the tracks of improves the response speed of system simultaneously, in the present invention, the PI controller is embedded in repetitive controller, form dual-loop controller.The PI controller, as interior ring, utilizes its fast-response, to improve the system dynamic responding speed; Repetitive controller, as outer shroud, utilizes its disturbance rejection, to improve the stable state accuracy of system.Because outer shroud only need be revised by Cycle by Cycle on the basis of interior ring tracking error, so adjustment process can shorten.So both meet the fast-response of control system, improved again the tracking accuracy of system.

In repetitive controller, be added to the input signal of controlled device except deviation signal, the past control deviation that also superposeed, this past control deviation was the control deviation in upper this moment of one-period.The deviation when last time is moved is reflected to now, and be added to controlled device and controlled together with current deviation, this control mode, deviation repeats to be used, and is called and repeats to control.Through the tracking accuracy that control can improve system afterwards greatly that repeats in several cycles, improve system quality.This control method is not only applicable to the tracking cycle input signal, can suppress PERIODIC INTERFERENCE yet.

The dual-loop controller structure as shown in Figure 5.I _rfor reference signal, e is error signal, i _2rfor the reference signal after overcompensation, S (z) is low pass filter, z ^kfor phase compensator, u _sfor the system voltage feed-forward signal, G (z) is controlled object, and the repetitive controller internal model structure is suc as formula shown in (7) here, and Q in formula (z) is for strengthening the filter of system robustness, and N is the internal mold step-length.The PI controller, as interior ring, is responsible for current-order is responded fast; Repetitive controller, as outer shroud, carries out the Cycle by Cycle correction to the tracking error of encircling in PI.Because outer shroud only need be revised on the basis of interior ring tracking error, so adjustment process can shorten.So both guarantee the response speed of system, guaranteed again the stable state accuracy of system.

The transfer function of repetitive controller 31:

$C_{\mathrm{im}}\left(z\right)=\frac{c\left(z\right)}{e\left(z\right)}=\frac{1}{1-Q\left(z\right)z^{-N}}---\left(7\right)$

Wherein c (z) is the control signal of internal mold output.

From above-mentioned control block diagram, the error signal e of repetitive controller 31 (z) is:

$e\left(z\right)=\frac{(1-Q\left(z\right)z^{-N})(1-P\left(z\right))}{1-z^{-N}(Q\left(z\right)-z^{k}S\left(z\right)P\left(z\right))}{i}_r\left(z\right)---\left(8\right)$

In formula, P (z) is the interior ring after PI proofreaies and correct in formula (6) and controls transfer function G ₁(s) discretization model:

$P\left(z\right)=\frac{G_{\mathrm{LCL}}\left(z\right)\&CenterDot;G_{\mathrm{PI}}\left(z\right)}{1+G_{\mathrm{LCL}}\left(z\right)\&CenterDot;G_{\mathrm{PI}}\left(z\right)}---\left(9\right)$

For the repetitive controller in accompanying drawing 5, according to minimum gain theory, in order to guarantee the system stability convergence, necessarily require auxiliary compensator Q (z), low pass filter S (z), phase compensator z ^kmeet || H (z) ||=|| Q (z)-z ^ks (z) P (z) ||<1.Therefore, auxiliary compensator Q (z) can get the constant that is less than 1, gets 0.95 in the present embodiment.S (z) adopts second order filter, phase compensator z ^kchoose must comprehensive P (z) and the phase delay of S (z), get z in the present embodiment ⁷.

Stability for the verification dual-loop controller, the substitution actual parameter, draw the nyquist plot of H (z) as shown in Figure 6, the pursuit path of H (z) is all the time in unit circle, and also has certain distance at medium and low frequency segment distance unit circle, illustrative system is stable, and leaves enough stability margins.

Below a kind of electric capacity Split type three-phase four-wire system STATCOM control method provided by the invention is specifically verified:

In order to verify correctness and the validity of the electric capacity Split type three-phase four-wire system STATCOM control method based on dual-loop controller, provide the emulation reference for the actual experimental prototype of building simultaneously, utilize MATLAB/SIMULINK to carry out simulation study to static synchronous compensator system, and control method proposed by the invention and traditional PI control strategy are compared, the parameter of artificial circuit is as shown in table 1.

Table 1 three-phase four-wire system STATCOM artificial circuit parameter

Before compensation, system power is that the asymmetric load electric current is as shown in accompanying drawing 7a.Accompanying drawing 7b is that the current inner loop dual-loop controller adopts the rear system power waveform of compensation under double loop control.As seen from the figure, after the current inner loop dual-loop controller adopts double loop control, the system power quality obviously improves, and obviously shorten stabilization time.After compensation, as shown in Figure 8, after the current inner loop dual-loop controller adopts double loop control, stable state accuracy obviously improves the system power aberration rate, and harmonic component obviously reduces, and system power resultant distortion rate (THD) is reduced to 3.13%, thereby has improved current quality.

In order to verify the validity of this paper put forward the methods, according to the Topology Structure Design three-phase four-wire system STATCOM experimental prototype of Fig. 1, its every experiment parameter and simulation are same, as shown in table 1.The experimental provision master controller adopts the system of DSP+FPFA, wherein adopt main control chip DSP as main control chip, adopt the TMS320F28335DSP chip to make its main operational and controlling of sampling, FPFA adopts the CycloneEP1C12Q24017N fpga chip as the dual port RAM parallel data processing.Experimental record adopts the Fluke power quality analyzer, accompanying drawing 9a and accompanying drawing 9b obtain by function-Scope in instrument, abscissa is chronomere's millisecond, ordinate is voltage/current, the V/A of unit, that has recorded STATCOM sends current waveform and phase relation, and given current effective value instruction is: A phase 50A, B phase 40A, C phase 30A; Figure 10 obtains by the function in instrument-humorous wave energy, and its abscissa is harmonic number, and ordinate is the percentage (with reference to Fig. 8) with respect to fundametal compoment, apparatus measures to current distortion rate be 3.1%.By accompanying drawing 9a, 9b, 10 is known, adopts double loop control after-current tracking accuracy to significantly improve, and the current waveform distortion obviously reduces, and electric current resultant distortion rate is reduced to 3.1%, has effectively improved the quality of grid-connected current.

Above-mentioned disclosed be only specific embodiments of the invention, this embodiment is only that clearer explanation the present invention is used, and limitation of the invention not, the changes that any person skilled in the art can think of, all should drop in protection range.

Claims (5)

1. an electric capacity Split type three-phase four-wire system STATCOM control method, is characterized in that, comprises the following steps:

S1: the instruction current detection, detect the load current I of the static synchronous compensation circuit of an electric capacity Split type three-phase four-wire system _labcmiddle fundamental positive sequence active current component I _lfabc, simultaneously, outer voltage controls by regulation loop PI controller and grading ring PI controller voltage stabilizing control and the Pressure and Control that realize the static synchronous compensation circuit DC side of described electric capacity Split type three-phase four-wire system;

S2: described load current I _labcdeduct described fundamental positive sequence active current component I _lfabcas the trace command of current inner loop dual-loop controller, the trace command of described current inner loop dual-loop controller deducts the electric current that in the static synchronous compensation circuit of described electric capacity Split type three-phase four-wire system, STATCOM occurs and obtains the deviation electric current;

S3: the described deviation electric current produced in S2 is inputted to described current inner loop dual-loop controller, in described current inner loop dual-loop controller, encircle the PI controller, improve the system dynamic responding speed; By described current inner loop dual-loop controller outer-loop repetitive controller, improve the current tracking precision; Wherein, the mode that described current inner loop dual-loop controller adopts described interior ring PI controller to be embedded in described outer shroud repetitive controller realizes.

2. a kind of electric capacity Split type three-phase four-wire system STATCOM control method as claimed in claim 1, is characterized in that, shown in step S1 further comprise:

Described electric capacity Split type three-phase four-wire system STATCOM circuit comprises distribution system, described STATCOM and load, and it is equivalent to three independently single-phase semi-bridge inversion circuit; Described STATCOM structure adopts the LCL filter;

In the instruction current detection, described regulation loop PI controller, by the difference of feedback regulation DC voltage reference value and DC voltage actual value, is realized the voltage stabilizing of the first DC bus capacitor and the second DC bus capacitor is controlled; Described grading ring PI controller, according to the positive negativity of the voltage difference of the first DC bus capacitor described in circuit and described the second DC bus capacitor, produces a zero sequence adjusting current-order i of opposite direction with it _0refafter, carry out three-dimensional dq0/abc rotational coordinates inverse transformation and obtain the abc three-phase instruction current that comprises zero-sequence component, by described zero-sequence current being carried out to the Pressure and Control of FEEDBACK CONTROL realization to described the first DC bus capacitor and described the second DC bus capacitor.

3. the electric capacity Split type three-phase four-wire system STATCOM control method based on dual-loop controller as claimed in claim 1, it is characterized in that, step S3 further comprises, described deviation electric current by described current inner loop dual-loop controller, regulate after output valve and the switch command of feedforward component stack as edge grid bipolar transistor in STATCOM.

4. a kind of electric capacity Split type three-phase four-wire system STATCOM control method as claimed in claim 3, described feedforward component is distribution system voltage.

5. a kind of electric capacity Split type three-phase four-wire system STATCOM control method as claimed in claim 1, is characterized in that, shown in step S3, the transfer function of described repetitive controller is: $C_{\mathrm{im}}\left(z\right)=\frac{c\left(z\right)}{e\left(z\right)}=\frac{1}{1-Q\left(z\right)z^{-N}}$

Q in formula (z) is for strengthening the extension filter of system robustness, and e is error signal, and N is the internal mold step-length, the control signal that c (z) exports for internal mold, for the error signal e (z) of repetitive controller is:

$e\left(z\right)=\frac{(1-Q\left(z\right)z^{-N})(1-P\left(z\right))}{1-z^{-N}(Q\left(z\right)-z^{k}S\left(z\right)P\left(z\right))}{i}_r\left(z\right)$

In formula, i _rfor reference signal, S (z) is low pass filter, z ^kfor phase compensator, P (z) is the discretization model that the interior ring after described interior ring PI controller is proofreaied and correct is controlled transfer function:

$P\left(z\right)=\frac{G_{\mathrm{LCL}}\left(z\right)\&CenterDot;G_{\mathrm{PI}}\left(z\right)}{1+G_{\mathrm{LCL}}\left(z\right)\&CenterDot;G_{\mathrm{PI}}\left(z\right)}$

In formula, G _lCL(s) transfer function of LCL filter:

$G_{\mathrm{LCL}}\left(s\right)=\frac{1}{(L_1+L_2+L_s)s+R}$

In formula, L _sfor electrical network equivalent inductance, L ₁for net side filter inductance, L ₂for inverter side filter inductance, the equiva lent impedance that R is described LCL filter circuit, described interior ring PI controller transfer function is:

k in formula _p, K _ibe respectively proportionality coefficient and the integral coefficient of PI controller;

Wherein, described auxiliary compensator Q (z) gets the constant that is less than 1, and described low pass filter S (z) adopts second order filter, described phase compensator z ^kthe phase delay of comprehensive P (z) and S (z) is chosen.

Images