CN1411118A - Current transformer DC side voltage closed loop control method of active power filter and system - Google Patents

Abstract

Current transformer DC side voltage closed-loop control method of active power filter characterizes in a selective harmonic detect method, which will get two-phase coordinate system current after detecting the N time of harmonic active or reactive DC component and through delay compensated angle variable matrix, and to deduct DC side voltage adjust signal to make the compensate current signal contain a certain basic wave active current component, in which, adjust signal is the difference between the given value of the current transformer DC side capacitance voltage and feed back value of the side capacitance voltage adjusted by an adjuster.

Description

The current transformer dc voltage closed loop control method and the system of Active Power Filter-APF

Technical field

The current transformer dc voltage closed-loop policy and the system of Active Power Filter-APF belong to the Active Power Filter-APF technical field.

Background technology

Along with the development of power electronic technology, power electronic equipment is widely used, and being become by its harmonic pollution in electric power net that causes is on the rise.Active Power Filter-APF is subject to people's attention as a kind of device that mains by harmonics is effectively compensated.

The Active Power Filter-APF system is made up of the two large divisions, as shown in Figure 1, i.e. and instruction current computing circuit and offset current generation circuit (offset current generation circuit is made of current tracking control circuit, drive circuit and three parts of main circuit).

By among Fig. 1 as can be seen offset current generation circuit be important part in the parallel connection type active electric filter.Offset current generation circuit is made up of voltage type PWM current transformer (main circuit) and corresponding driving circuit thereof, current tracking control circuit.In order to guarantee that it has good offset current trace performance, must be a suitable value with the voltage control of current transformer dc bus capacitor.

In field of power electronics, the conventional method of controlling for dc voltage is that the electric capacity for DC side provides an independent DC power supply again, generally realizes by a diode rectifier circuit.Though this method can reach the purpose of control dc capacitor voltage, need set up circuit kit in addition, thereby increase the complexity of whole system, cost, loss of system or the like have also been increased.

In the system of Active Power Filter-APF realizes, only need be for the control of dc capacitor voltage by main circuit is just suitably controlled and can have been realized.To dc voltage U _DcControl realize in conjunction with offset current generation circuit by DC control part in the instruction current computing circuit.Because dc capacitor voltage control detects link in conjunction with harmonic current and finishes, therefore along with the improvement of harmonic current detecting method, the dc capacitor voltage control method also has difference.

I based on instantaneous reactive power theory _p, i _qDc capacitor voltage control circuit schematic diagram such as Fig. 2 of harmonic detecting method.Among the figure, U _DcrBe the set-point of capacitance voltage, U _DcfBe the value of feedback of capacitance voltage, the difference of two amounts becomes conditioning signal Δ i through a pi regulator _p(offset current reference value real component), its be added to DC component i of instantaneous active current of first-harmonic _pOn, the process computing is at compensating current signal i _Ah, i _Bh, i _ChIn comprise certain fundamental active current.Offset current generation circuit is according to i _hProduce offset current i _cInject electrical network, make to comprise certain fundamental active current component in the offset current, thereby make the DC side and the AC side positive energy exchange of the current transformer of APF, U _DcBe adjusted to set-point.

Adopt traditional i _p, i _qHarmonic detecting method, digital controller can produce time of delay, and method itself is to compensating time of delay, changing for electric current has obvious time lag, can't respond the quick variation of harmonic current, thereby can't realize the real-Time Compensation of harmonic wave.Though rely on the dc bus capacitor control of harmonic current detection can accomplish the result who controls, because the detection real-time of harmonic current is the important step that guarantees the Active Power Filter-APF compensation characteristic, so dc bus capacitor control also needs change thereupon.

Summary of the invention

The object of the present invention is to provide a kind of not only can compensating digits formula controller delay time but also can be controlled at dc capacitor voltage the current transformer dc voltage closed loop control method and the system of the Active Power Filter-APF of an appropriate value.

For digital controller, need the operation time of at least one sampling period Δ T, the output of PWM inverter simultaneously also needs a Δ T time to set up voltage.Like this, from the current sample to the harmonic compensation, there is the time of delay of a Δ T at least.In time of delay Δ T, establishing the first-harmonic angular frequency is ω, and nth harmonic has rotated through in this Δ T

Δθ＝n·ω·ΔT＝2nπfΔT(rad)，

If not to compensating this time of delay, then rotation transformation C and its inverse transformation C ^-1It no longer is identical transformation.When serious, the compensation of certain harmonic wave even can form positive feedback.For example for 11 subharmonic, at power frequency f=50Hz, time of delay, 11 subharmonic rotated 3.454rad in this 1ms, near 180 ° during 1ms.Like this, after detecting 11 subharmonic, not only can not eliminate this subharmonic during harmonic compensation, form positive feedback on the contrary.As seen, in the detection of harmonic current, the compensation of time of delay is crucial.Hope simply reduces time of delay by the raising of hardware computational speed, can only make the price of APF become expensive more.This method is carrying out adding Δ θ angle in order to the compensating delay time in transformation matrix when two-phase rotates to the conversion of two-phase static coordinate.This method is calculated easy, practical.

The present invention proposes a kind of closed loop control method based on the dc capacitor voltage on the selective harmonic electric current detecting method that adds predictive compensation.

By the three-phase circuit instantaneous reactive power theory as can be known, three-phase circuit instantaneous active power p and instantaneous reactive power q are defined as p=ei _p, q=ei _qP and i _p, q and i _qBetween differ coefficient e.When the sinusoidal symmetry of three-phase voltage, $e=\sqrt{3}E,$ Be constant.So p and i _p, q and i _qBe directly proportional.

According to the three-phase instantaneous reactive power theory each phase instantaneous reactive power and active power definition are obtained: $p_a=3e_a^{2}p/A---q_a=e_a(e_b-e_c)q/A$ $p_b={3e}_b^{2}p/A---q_b=e_b(e_c-e_a)q/A......\left(1\right)$ $p_c=3e_c^{2}p/A---q_c=e_c(e_a-e_b)q/A$

A=(e wherein _a-e _b) ²+ (e _b-e _c) ²+ (e _c-e _a) ²

Obtain by formula (1):

p _a+p _b+p _c＝p (2)

q _a+q _b+q _c＝0

By formula (2) as can be known, the instantaneous reactive power sum of each phase is zero.Though the instantaneous reactive power of independent a certain phase is non-vanishing, the summation of three-phase is zero, and this shows that instantaneous reactive power just exchanges between three-phase.Therefore, for Active Power Filter-APF, instantaneous reactive power can not cause the energy exchange between its AC side and the DC side.By formula (2) as can be known, each phase instantaneous active power sum equals three-phase circuit instantaneous active power p.That is to say that for Active Power Filter-APF, if do not consider the loss of each several part, the instantaneous active power of AC side will all be delivered to DC side, i.e. instantaneous active power p is depended in the energy exchange of AC side and DC side.

On physical significance, this moment, the capacitor C of DC side was an energy-storage travelling wave tube, so should be that the active power of power supply is charged to capacitor C.Therefore, we know to capacitor charging be the instantaneous active power of AC side, but and do not know the fundametal compoment or the harmonic component of active current.Because in order the harmonic component in the source current not to be introduced, so should adopt the fundametal compoment of the active current in the power supply to charge as far as possible to capacitor.Therefore, the conditioning signal of dc voltage has been added on the fundametal compoment of active current, comprise certain active current fundametal compoment in the feasible offset current that produces, and the purpose of this active current fundametal compoment is exactly to charge to capacitor.Thereby reached the purpose of DC voltage control.

For selective harmonic detection method and traditional i _p, i _qMethod also has some differences on DC voltage control.In traditional method, this direct voltage conditioning signal △ i _pBe to be added on the DC component of the instantaneous active current of first-harmonic, that is, $I_h^{\text{'}}=I-I_f^{\text{'}},$ $I_f^{\text{'}}=I_f+{\mathrm{\Δi}}_p,$ So $I_h^{\text{'}}=I-I_f-{\mathrm{\Δi}}_p$ 。Because direct voltage conditioning signal △ i _pShould be the meritorious amount of direct current of a first-harmonic, and in the selective harmonic detection method, be the DC component I of each harmonic through LPF _h, rather than the DC component of first-harmonic.So as shown in Figure 3, in the selective harmonic detection method, control is changed a little for DC side.Be in order to make compensating current signal i equally _Ah, i _Bh, i _ChIn comprise certain fundamental active current, therefore the direct voltage conditioning signal is deducted after detecting compensating current signal, that is, $I_h^{\text{'}}=I_h-{\mathrm{\Δi}}_p.$

Method proposed by the invention is characterised in that: it is a kind of at the DC component i that detects the meritorious and reactive current of N subharmonic _Pn, i _QnAfter, again through having added the special transformation Matrix C of delay compensation angle △ θ _{△ θ}To obtain two-phase coordinate system current i _{α n}, i _{β n}After, therefrom deduct dc voltage conditioning signal △ i again _pSo that compensating current signal i _An, i _Bn, i _CnIn contain the method for certain fundamental active current, be that a kind of selective harmonic that is based upon the delay prediction compensation detects the DC side voltage control method on the basis, wherein direct voltage conditioning signal △ i _pBe current transformer dc capacitor voltage set-point U _DcrWith above-mentioned capacitance voltage value of feedback U _DcfPoor, obtain through a pi regulator again, it contains following steps successively:

(1) phase voltage e _aAfter frequency multiplier N frequency multiplication by phase-locked loop and just, cosine generation circuit obtains and e _aSynchronous sinusoidal signal sinn ω t and corresponding cosine signal COSn ω t, thus transformation matrix C obtained _n: $C_n=\left[\begin{array}{cc}-\sin \mathrm{n\ωt}& \cos \mathrm{n\ωt}\\ \cos \mathrm{n\ωt}& \sin \mathrm{n\ωt}\end{array}\right];$

(2) three-phase current i _a, i _b, i _cThrough 3s/2R (three phase static coordinate system/two-phase rotating coordinate system) conversion, be transformed into the current i of static α, β two phase coordinate systems _α, i _β: $\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]=C_{32}\·\left[\begin{array}{c}{i}_a\\ i_b\\ i_c\end{array}\right],$ C ₃₂It is transformation matrix;

(3) biphase current i _α, i _βThrough transformation matrix C _nDraw the meritorious and reactive current component of the each harmonic electric current under the two-phase rotating coordinate system: $\left[\begin{array}{c}{i}_{\mathrm{pn}}\\ i_{\mathrm{qn}}\end{array}\right]=C_n\·\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]=C_n\·C_{32}\·\left[\begin{array}{c}{i}_a\\ i_b\\ i_c\end{array}\right];$

(4) the meritorious and reactive current component i of each harmonic _Pn, i _QnDraw the DC component i of the meritorious and reactive current of N subharmonic through low pass filter LPF filtering _Pn, i _QnAgain through adding the special transformation Matrix C of offset angle Δ θ _{Δ θ}Obtain the current i under two phase coordinate systems _{α n}, i _{β n}: $\left[\begin{array}{c}{i}_{\mathrm{\αn}}\\ i_{\mathrm{\βn}}\end{array}\right]=C_{\mathrm{\Δ\θ}}\·\left[\begin{array}{c}{\stackrel{-}{i}}_{\mathrm{pn}}\\ {\stackrel{-}{i}}_{\mathrm{qn}}\end{array}\right]={\left[\begin{array}{cc}-\sin (\mathrm{n\ωt}+\mathrm{\Δ\θ})& \cos (\mathrm{n\ωt}+\mathrm{\Δ\θ})\\ \cos (\mathrm{n\ωt}+\mathrm{\Δ\θ})& \sin (\mathrm{n\ωt}+\mathrm{\Δ\θ})\end{array}\right]}^{-1}\·\left[\begin{array}{c}{\stackrel{-}{i}}_{\mathrm{pn}}\\ {\stackrel{-}{i}}_{\mathrm{qn}}\end{array}\right];$

Wherein, Δ θ=n ω Δ T; Δ T is the time interval of compensation;

(5) obtain U _Dcr, U _DcfDifference obtain dc voltage conditioning signal Δ i through pi regulator _p

(6) negative feedback stack is obtained the compensating signal of N subharmonic current under two phase coordinate systems and is: $i_{\mathrm{\αn}}^{\text{'}}=i_{\mathrm{\αn}}-C_1^{-1}\·\left[\begin{array}{c}{\mathrm{\Δi}}_p\\ {\mathrm{\Δi}}_q\end{array}\right],{\mathrm{\Δi}}_q=0$ $i_{\mathrm{\βn}}^{\text{'}}=i_{\mathrm{\φn}}-C_1^{-1}\·\left[\begin{array}{c}{\mathrm{\Δi}}_p\\ {\mathrm{\Δi}}_q\end{array}\right],{\mathrm{\Δi}}_q=0;$

(7) finally draw the N subharmonic current compensating signal i that contains the fundamental active current component _An, i _Bn, i _Cn: $\left[\begin{array}{c}{i}_{\mathrm{an}}\\ i_{\mathrm{bn}}\\ i_{\mathrm{cn}}\end{array}\right]=C_{23}\·\left[\begin{array}{c}{i}_{\mathrm{\αn}}^{\text{'}}\\ i_{\mathrm{\βn}}^{\text{'}}\end{array}\right],$

Carry out in digital signal processor DSP step (2)-(7).

Method proposed by the invention is characterised in that: want the multiple harmonic of parallel detection simultaneously when needs compensate a plurality of appointment subharmonic, again the current component i of each all required subharmonic _{α n}, i _{β n}Add up respectively separately, obtain all harmonic waves and, therefrom deduct the dc voltage conditioning signal again, thereby obtain the compensating signal of the multiple harmonic under two phase coordinate systems.

System proposed by the invention is characterised in that, it contains: the Hall element that links to each other with load, signal processing unit and DSP successively, the pulse-width modulation circuit PWM that links to each other with digital quantity output among the DSP and respectively with DSP in the Intelligent Power Module IPM module that links to each other with power supply of DC voltage control output.

Emulation experiment proves: it has reached intended purposes.

Description of drawings

Fig. 1. the system architecture diagram of Active Power Filter-APF.

Fig. 2. comprise the i of DC voltage control link _p-i _qHarmonics detection circuit.

Fig. 3. comprise the selective harmonic testing circuit of DC voltage control link.

Fig. 4. comprise the selective harmonic testing circuit of the compensation of delay of DC voltage control link.

Fig. 5. add the circuit system theory diagram of DC side control.

Fig. 6. main program flow chart.

Fig. 7. the program flow chart of offset angle Δ θ module.

Fig. 8 .CONSR modular structure figure.

Fig. 9 .SBCONSR modular structure figure.

Figure 10 .LPF modular program FB(flow block).

Figure 11 .REVSR modular structure figure.

Figure 12 .WAVE modular program FB(flow block).

Figure 13. dc voltage suppresses the modular program FB(flow block).

Figure 14. DC voltage control analogous diagram (U _Dc=750V).

Figure 15. the simulation result of selective harmonic detection method (detecting) since 0.06 second:

(1) dc capacitor voltage waveform;

(2) detect all harmonic current waveforms;

(3) current transformer APF load waveform;

(4) source current waveform.

Figure 16. dc voltage conditioning signal Δ i _pOscillogram.

Figure 17. the harmonic wave forms that utilization selective harmonic detection method obtains:

(1) the 5th harmonic wave;

(2) the 7th subharmonic;

(3) the 11st subharmonic;

(4) the 13rd subharmonic.

Embodiment

Aspect the hardware circuit realization, adopt the digital signal processor TMS320F240PQA of Texas Instruments,, compensate the computing of current command signal with its CPU as the instruction current computing circuit, the IPM module adopts the MIG150Q6C of Toshiba, and systematic schematic diagram as shown in Figure 4.The assembly language directive of TMS320F240PQA special use is adopted in program composition.

The software main program flow chart as shown in Figure 5.According to functional structure it is divided into seven submodules.Offset angle Δ θ module, CONSR module, SBCONSR module, LPF module, REVSR module, DC voltage control module, WAVE module.

Offset angle Δ θ module

This module is the calculating caused time delay of compensation owing to digital controller.Flow chart as shown in Figure 7.

The inlet: time of delay Δ T

Outlet: the θ angle that has added offset angle Δ θ time of delay

The CONSR module

This module adopts principle of vector control, and three-phase current signal is transformed on the rotational coordinates.Wherein need to call the SBCONSR module, flow chart as shown in Figure 8.

Inlet: three-phase current signal and corresponding θ angle thereof

Outlet: the current signal of two-phase rotating coordinate system

Annotate: 1.IU_AD, IV_AD, IW_AD are external variable for the three-phase electricity flow valuve through obtaining after the A/D sampling.

The SBCONSR module

For realizing the subfunction of two rectangular coordinate system conversions under the same plane.Flow chart as shown in Figure 9.

Inlet: the angle between coordinate in rectangular coordinate system A and rectangular coordinate system A and the rectangular coordinate system B

Outlet: the coordinate in rectangular coordinate system B

The LPF module

Realize digitized low-pass filtering, leach DC component wherein.See shown in Figure 10.

Inlet: the input current of current time k, last is output current, time constant filter T and the sampling time Δ t of k-1 constantly

Outlet: DC component

The DC voltage control module

Realization is for the control of dc voltage.Flow chart as shown in figure 13.

Inlet: the dc capacitor voltage detected value of APF and dc voltage set point

Outlet: the conditioning signal of dc voltage under the two-phase rest frame

The REVSR module

This module earlier is transformed to the DC component the two-phase rotating coordinate system under the signal under the two-phase rest frame, again it is transformed to basic voltage vectors under the space vector coordinate system with.Wherein need to call the SBCONSR module, flow chart as shown in figure 11.

Inlet: current dc component signal under the two-phase rotating coordinate system and θ angle

Outlet: two adjacent basic vector and the amplitudes thereof that voltage vector resolves into

The WAVE module

This module adopts five sections method for generation of principle, PWM of space vector, utilizes DSP internal proprietary hardware and order to generate the PWM waveform.Flow chart as shown in figure 12.

Inlet: two adjacent basic vector and the amplitudes thereof that sense of current parameter and voltage vector resolve into

Outlet: PWM ripple generation signal

Annotate:

1.DIR_SET be sense of current parameter, 0 for just, 1 for negative.

2.VECTX0, VECTX1 is the two adjacent basic vectors that voltage vector resolves into.

3.VAMPX0, VAMPX1 is the amplitude of the two adjacent basic vectors that decomposite of voltage vector.

4.VABASE, VBBASE, VRBASE be respectively space vector coordinate system A, B, C coordinate.

5.ACTR, CMPR1, CMPR2 be the specified register in the task manager (EV) of DSP, is used for the generation of means of space vector representation PWM ripple.

In the electric power system that contains nonlinear elements, have harmonic wave and produce.We take mode in parallel with the active filter connecting system, and the CPU board program begins initialization.The two-phase load current of electric power system is sampled into DSP by the AD passage, begins biphase current is carried out harmonic analysis.Because electric power system is a three-phase balanced system, can obtain an other phase current according to the known biphase current of the former reason of three-phase equilibrium, then three-phase current is changed through 3S/2S (three phase static coordinate system/two-phase rest frame), be changed to the static coordinate system of two-phase, carrying out 2S/2R (two-phase rest frame/two-phase rotating coordinate system) again changes, then leach wherein DC component by LPF, the angle delta θ of compensation to be added computing herein, Δ θ angle is obtained by the PLL sampling, after adding offset angle, then the DC component in the two-phase rotating coordinate system is changed to and obtain the harmonic current signal in the space vector coordinate system.Certain dc voltage is set, and the voltage actual value and the set point that detect the DC side of APF in real time compare, and difference obtains the DC adjustment signal through pi regulator, and the process inverse transformation obtains the voltage control conditioning signal under the two-phase rest frame.At this moment, the harmonic current signal that detects is deducted the DC voltage control conditioning signal be compensated current signal, and then the space vector of this compensating current signal is exported with the form of PWM ripple.The PWM ripple of output is used for driving the IPM module, produces to be used for the electric current of compensation harmonic.Concrete compensation capacity is by the power output decision of IPM module.Thus, both can reach the purpose of compensation harmonic, in compensation harmonic, compensate again, reach the purpose of real-Time Compensation because the calculating of digital controller is delayed time.

Proved above judgement by Computer Simulation, concrete condition is seen Figure 14-Figure 17.Simulation software adopts matlab6.0.Figure 14 is the DC voltage control analogous diagram.Emulation explanation DC side voltage control method can reach dc capacitor voltage and be controlled at given numerical value.Figure 15 is a system harmonics current compensation analogous diagram.The emulation explanation is when DC voltage control arrives given voltage, use the selection subharmonic detection method that adds predictive compensation can detect the harmonic wave of system, and can compensate, compensation dry straight can be eliminated the harmonic wave of the selection of required compensation substantially.Figure 16 is the conditioning signal analogous diagram of DC voltage control.Emulation explanation has the conditioning signal of DC voltage control really, and in voltage control after designated value, along with the fluctuation of voltage, still can voltage still be controlled on the given voltage by the voltage control of DC side.Figure 17 is 5,7,11,13 subharmonic that comprise detected appointment under the selection subharmonic detection method that adds predictive compensation of DC voltage control time.This new method that has DC voltage control of emulation explanation can detect really specifies inferior harmonic wave.

The emulation experiment proof adopts the new method of invention can accomplish the voltage control of needed DC side really, and can reach the result of compensation harmonic really through the Active Power Filter-APF after the DC voltage control.

Claims (3)

1. the current transformer dc voltage closed loop control method of Active Power Filter-APF contains the active current i based on instantaneous reactive power theory _p, reactive current i _qThe step that harmonic wave detects is characterized in that: it is a kind of at the DC component i that detects the meritorious and reactive current of N subharmonic _Pn, i _QnAfter, again through having added the special transformation Matrix C of delay compensation angle Δ θ _{Δ θ}To obtain two-phase coordinate system current i _{α n}, i _{β n}After, therefrom deduct dc voltage conditioning signal Δ again _IpSo that compensating current signal i _An, i _Bn, i _CnIn contain the method for certain fundamental active current, be that a kind of selective harmonic that is based upon the delay prediction compensation detects the DC side voltage control method on the basis, wherein direct voltage conditioning signal Δ _IpBe current transformer dc capacitor voltage set-point U _DcrWith above-mentioned capacitance voltage value of feedback U _DcfPoor, obtain through a pi regulator again, it contains following steps successively:

(1) phase voltage e _aAfter frequency multiplier N frequency multiplication by phase-locked loop and just, cosine generation circuit obtains and e _aSynchronous sinusoidal signal sin n ω t and corresponding cosine signal cosn ω t, thus transformation matrix C obtained _n: $C_n=\left[\begin{array}{cc}-\sin \mathrm{n\ωt}& \cos \mathrm{n\ωt}\\ \cos \mathrm{n\ωt}& \sin \mathrm{n\ωt}\end{array}\right];$

(2) three-phase current i _a, i _b, i _cThrough 3S/2R (three phase static coordinate system/two-phase rotating coordinate system) conversion, be transformed into the current i of static α, β two phase coordinate systems _α, i _β: $\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]=C_{32}\·\left[\begin{array}{c}{i}_a\\ i_b\\ i_c\end{array}\right],$ C ₃₂It is transformation matrix;

(3) biphase current i _α, i _βThrough transformation matrix C _nDraw the meritorious and reactive current component of the each harmonic electric current under the two-phase rotating coordinate system: $\left[\begin{array}{c}{i}_{\mathrm{pn}}\\ i_{\mathrm{qn}}\end{array}\right]=C_n\·\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]=C_n\·C_{32}\·\left[\begin{array}{c}{i}_a\\ i_b\\ i_c\end{array}\right];$

(4) the meritorious and reactive current component i of each harmonic _Pn, i _QnDraw the DC component i of the meritorious and reactive current of N subharmonic through low pass filter LPF filtering _Pn, i _Qn, again through adding the special transformation Matrix C of offset angle Δ θ _{Δ θ}Obtain the current i under two phase coordinate systems _{α n}, i _{β n}: $\left[\begin{array}{c}{i}_{\mathrm{\αn}}\\ i_{\mathrm{\βn}}\end{array}\right]=C_{\mathrm{\Δ\θ}}\·\left[\begin{array}{c}{\stackrel{-}{i}}_{\mathrm{pn}}\\ {\stackrel{-}{i}}_{\mathrm{qn}}\end{array}\right]={\left[\begin{array}{cc}-\sin (\mathrm{n\ωt}+\mathrm{\Δ\θ})& \cos (\mathrm{n\ωt}+\mathrm{\Δ\θ})\\ \cos (\mathrm{n\ωt}+\mathrm{\Δ\θ})& \sin (\mathrm{n\ωt}+\mathrm{\Δ\θ})\end{array}\right]}^{-1}\·\left[\begin{array}{c}{\stackrel{-}{i}}_{\mathrm{pn}}\\ {\stackrel{-}{i}}_{\mathrm{qn}}\end{array}\right];$

Wherein, Δ θ=n ω Δ T; Δ T is the time interval of compensation;

(5) obtain U _Dcr, U _DcfDifference obtain dc voltage conditioning signal Δ i through pi regulator _p

(6) negative feedback stack is obtained the compensating signal of N subharmonic current under two phase coordinate systems and is: ${i_{\mathrm{\αn}}^{\text{'}}=i}_{\mathrm{\αn}}-C_1^{-1}\·\left[\begin{array}{c}{\mathrm{\Δi}}_p\\ {\mathrm{\Δi}}_q\end{array}\right],{\mathrm{\Δi}}_q=0$ $i_{\mathrm{\βn}}^{\text{'}}=i_{\mathrm{\φn}}-C_1^{-1}\·\left[\begin{array}{c}{\mathrm{\Δi}}_p\\ {\mathrm{\Δi}}_q\end{array}\right],{\mathrm{\Δi}}_q=0;$

(7) finally draw the N subharmonic current compensating signal i that contains the fundamental active current component _An, i _Bn, i _Cn: $\left[\begin{array}{c}{i}_{\mathrm{an}}\\ i_{\mathrm{bn}}\\ i_{\mathrm{cn}}\end{array}\right]=C_{23}\·\left[\begin{array}{c}{i}_{\mathrm{\αn}}^{\text{'}}\\ i_{\mathrm{\βn}}^{\text{'}}\end{array}\right],$

Carry out in digital signal processor DSP step (2)-(7).

2. the current transformer dc voltage closed loop control method of Active Power Filter-APF according to claim 1, it is characterized in that: when needs compensate a plurality of appointment subharmonic, want the multiple harmonic of parallel detection simultaneously, again the current component i of each all required subharmonic _{α n}, i _{β n}Add up respectively separately, obtain all harmonic waves and, therefrom deduct the dc voltage conditioning signal again, thereby obtain the compensating signal of the multiple harmonic under two phase coordinate systems.

3. Active Power Filter-APF current transformer dc voltage closed loop control method according to claim 1 and the system that proposes, it is characterized in that, it contains: the Hall element that links to each other with load, signal processing unit and DSP successively, the pulse-width modulation circuit PWM that links to each other with digital quantity output among the DSP and respectively with DSP in the Intelligent Power Module IPM module that links to each other with power supply of DC voltage control output.

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