CN104393598A - Frequency-adaptation improved resonant control method for active power filter - Google Patents

Abstract

The invention discloses a frequency-adaptation improved resonant control method for an active power filter. Through changing the central frequency of a resonant controller in real time through a phase-locked loop, the disadvantage of narrow frequency adaptation range of an existing control method is overcame, and the frequency adaptation range is improved; according to the actual configuration, through arranging an improved resonant controller or an improved quasi resonant controller in a circuit controller, the resonant control effect is kept, and the system stability is improved; the controller is directly designed at a discrete domain, and accordingly the error due to converting to the discrete domain from a continuous domain is avoided.

Description

A kind of frequency self-adaption modified model resonance control method of Active Power Filter-APF

Technical field

The invention belongs to Active Power Filter-APF Current Control Technology field, more specifically say, relate to a kind of frequency self-adaption modified model resonance control method of Active Power Filter-APF.

Background technology

Along with the develop rapidly of power electronic technology, the application of nonlinear load result in the harmonic pollution problems of electrical network, in order to solve the day by day serious harmonic problem of electrical network, have developed a large amount of Active Power Filter-APFs.But in order to improve the harmonic compensation precision of Active Power Filter-APF, Current Control Technology becomes a study hotspot.

Chinese invention patent " a kind of parallel type quasi-proportional resonance active power filter and control method " (publication number: 103683292A) discloses the accurate proportional resonant control method of a kind of frequency self-adaption based on phase-locked loop, the method adopts the accurate ratio resonant controller of simple zero, controller high band can introduce 90 ° of delayed phase to system, reduce the stability of system, and limit the raising of system bandwidth.Chinese invention patent " the accurate proportional resonant control method of parallel connection type active electric filter and control system " (publication number: 102931660A) discloses a kind of accurate proportional resonant control method of frequency self-adaption of continuous domain, when adopting DSP (Digital Signal Processing) to realize, need to carry out sliding-model control by different discretization method to parameter, can error be introduced, affect controller's effect.Chinese invention patent " active power filter selective harmonic compensation control method " (publication number: 103427419A) discloses a kind of active power filter selective harmonic compensation control method of the self-adapting resonance controller based on control frequency adjustment, the frequency adaptation scope of the method is narrower, only has 0.5Hz.

Summary of the invention

The object of the invention is to overcome the deficiencies in the prior art, a kind of frequency self-adaption modified model resonance control method of Active Power Filter-APF is provided, frequency adaptation scope can be increased, thus ensure, when frequency wide region changes, still can keep resonance control effects.

For achieving the above object, the frequency self-adaption modified model resonance control method of a kind of Active Power Filter-APF of the present invention, is characterized in that, comprise the following steps:

(1), PLL phase-locked loop module is according to line voltage u _gget phase angle θ and the angular frequency of line voltage ₀;

(2), abc-dq0 coordinate transformation module according to phase angle θ, by line voltage u _gfrom abc coordinate system transformation to the voltage u dq0 coordinate system _gd, u _gq, u _g0, simultaneously by three level VSI ac-side current i ₁from abc coordinate system transformation to the current i dq0 coordinate system _1d, i _1q, i ₁₀;

(3) output active current set-point, is calculated with neutral current set-point

DC voltage control module is by the set-point of three level VSI DC voltage and voltage u between three level VSI-positive bus-bar and neutral point _dc1do to differ from again and voltage u between three level VSI negative busbar and neutral point _dc2differ from, the difference obtained is carried out PI control, obtains active current set-point simultaneously by voltage u between three level VSI positive bus-bar and neutral point _dc1and voltage u between negative busbar and neutral point _dc2differ from, the difference obtained is carried out PI control, obtains neutral current set-point

(4), Harmonic currents detection module is by load current i _lcarry out discrete Fourier transform (DFT) and obtain harmonic current i _ldh, i _lqh, i _l0h;

(5), current control module calculates and exports controlled quentity controlled variable u _d, u _q, u ₀

(5.1), calculating current Δ i _d: by active current set-point with harmonic current i _ldhsummation again with current i _1ddiffer from, obtain ${\mathrm{\Δi}}_d=i_d^{*}+i_{\mathrm{Ldh}}-i_{1d};$

(5.2), calculating current Δ i _q: by harmonic current i _lqhwith current i _1qdiffer from, obtain Δ i _q=i _lqh-i _1q;

(5.3), calculating current Δ i ₀: by neutral current set-point with harmonic current i _l0hsummation again with current i ₁₀differ from, obtain ${\mathrm{\Δi}}_0=i_0^{*}+i_{L0h}-i_{10};$

(5.4), current control module is according to above-mentioned angular frequency ₀, by the Δ i calculated _d, Δ i _q, Δ i ₀be sent to resonant controller and PI controller successively, obtain exporting controlled quentity controlled variable u _d, u _q, u ₀;

(6), voltage feed-forward control module is by described for step (2) voltage u _gd, u _gq, u _g0and the output controlled quentity controlled variable u described in step (5.4) _d, u _q, u ₀superpose, obtain controlled quentity controlled variable V _d, V _q, V ₀;

(7), dq0-abc coordinate transformation module according to above-mentioned phase angle θ, by the controlled quentity controlled variable V described in step (6) _d, V _q, V ₀from dq0 coordinate system transformation to the controlled quentity controlled variable V abc coordinate system _a, V _b, V _c;

(8), the controlled quentity controlled variable V of SPWM module according to step (7) _a, V _b, V _cobtain corresponding switch controlling signal, then control with this switch controlling signal three level VSI each IGBT open shutoff.

Goal of the invention of the present invention is achieved in that

The frequency self-adaption modified model resonance control method of Active Power Filter-APF of the present invention, changes the centre frequency of resonant controller in real time by phase-locked loop, this overcome the defect that existing control method frequency adaptation scope is narrower, improve the scope of frequency adaptation; In the configuration of reality, by adding modified model resonant controller or modified model quasi resonant control in circuit controller, resonance control effects can be kept like this, the stability of system can be improved again.

Meanwhile, the frequency self-adaption modified model resonance control method of Active Power Filter-APF of the present invention also has following beneficial effect:

(1), improvement is made for existing frequency close limit self-adapting resonance control method, control method of the present invention can change the centre frequency of resonant controller in real time based on phase-locked loop, thus ensure, when frequency wide region changes, still can keep the effect that resonance controls.

(2), modified model resonant controller has two zero point, can increase the phase margin of Active Power Filter-APF, thus improves the stability of Active Power Filter-APF.

(3), the present invention is directly in discrete domain design, C language can be adopted to programme, dsp chip realizes, implement simple and easy.

Accompanying drawing explanation

Fig. 1 is the control block diagram of Active Power Filter-APF;

Fig. 2 is the flow chart of the frequency self-adaption modified model resonance control method of Active Power Filter-APF of the present invention;

Fig. 3 is the theory diagram of DC voltage control module;

Fig. 4 is the theory diagram of current control module;

Fig. 5 is the theory diagram of modified model resonant controller;

Fig. 6 is the theory diagram of modified model quasi resonant control;

Fig. 7 is under mains frequency rated condition, adopts method of the present invention to Active Power Filter-APF compensation effect analogous diagram;

Fig. 8 is under mains frequency surging condition, adopts or does not adopt method of the present invention to Active Power Filter-APF compensation effect analogous diagram.

Embodiment

Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described, so that those skilled in the art understands the present invention better.Requiring particular attention is that, in the following description, when perhaps the detailed description of known function and design can desalinate main contents of the present invention, these are described in and will be left in the basket here.

Embodiment

Fig. 1 is the control block diagram of Active Power Filter-APF.

In the present embodiment, as shown in Figure 1, Active Power Filter-APF comprises main circuit and controls two parts, wherein, is control section below the dotted portion of Fig. 1.

Main circuit part is made up of three level VSI 1, LCL filter 2, nonlinear load 3.Three level VSI 1 is connected with electrical network by LCL filter 2, and nonlinear load 3 is directly connected with electrical network, thus constitutes the main circuit of a complete Active Power Filter-APF.

Control section comprises: PLL phase-locked loop module 4, abc-dq0 coordinate transformation module 5, DC voltage control module 6, Harmonic currents detection module 7, current control module 8, voltage feed-forward control module 9, dq0-abc coordinate transformation module 10, SPWM module 11, constitute the control section of Active Power Filter-APF.

Fig. 2 is the flow chart of the frequency self-adaption modified model resonance control method of Active Power Filter-APF of the present invention.

In the present embodiment, as shown in Figure 2, a kind of frequency self-adaption modified model resonance control method of Active Power Filter-APF, comprises the following steps:

S1, PLL phase-locked loop module is according to line voltage u _gget phase angle θ and the angular frequency of line voltage ₀;

S2, abc-dq0 coordinate transformation module according to phase angle θ, by line voltage u _gfrom abc coordinate system transformation to the voltage u dq0 coordinate system _gd, u _gq, u _g0, simultaneously by three level VSI ac-side current i ₁from abc coordinate system transformation to the current i dq0 coordinate system _1d, i _1q, i ₁₀;

S3, calculating export active current set-point with neutral current set-point

In the present embodiment, as shown in Figure 3, DC voltage control module is by the set-point of three level VSI DC voltage for the theory diagram of DC voltage control module and voltage u between three level VSI-positive bus-bar and neutral point _dc1do to differ from again and voltage u between three level VSI negative busbar and neutral point _dc2differ from, the difference obtained is carried out PI control, obtains active current set-point simultaneously by voltage u between three level VSI positive bus-bar and neutral point _dc1and voltage u between negative busbar and neutral point _dc2differ from, the difference obtained is carried out PI control, obtains neutral current set-point

S4, Harmonic currents detection module are by load current i _lcarry out discrete Fourier transform (DFT) and obtain harmonic current i _ldh, i _lqh, i _l0h;

S5, current control module calculate and export controlled quentity controlled variable u _d, u _q, u ₀

S5.1), calculating current Δ i _d: by active current set-point with harmonic current i _ldhsummation again with current i _1ddiffer from, obtain ${\mathrm{\Δi}}_d=i_d^{*}+i_{\mathrm{Ldh}}-i_{1d};$

S5.2), calculating current Δ i _q: by harmonic current i _lqhwith current i _1qdiffer from, obtain Δ i _q=i _lqh-i _1q;

S5.3), calculating current Δ i ₀: by neutral current set-point with harmonic current i _l0hsummation again with current i ₁₀differ from, obtain ${\mathrm{\Δi}}_0=i_0^{*}+i_{L0h}-i_{10};$

S5.4), current control module is according to above-mentioned angular frequency ₀, by the Δ i calculated _d, Δ i _q, Δ i ₀be sent to resonant controller and PI controller successively, obtain exporting controlled quentity controlled variable u _d, u _q, u ₀;

In the present embodiment, current control module is directly in discrete domain design, as shown in Figure 4, in the present invention, current control module comprises modified model resonant controller corresponding to 6,12,18,24 subharmonic or modified model quasi resonant control and PI controller, in the diagram, and n=d, q, 0;

In the present embodiment, the transfer function that modified model resonant controller adopts is:

$H_h\left(z\right)=\frac{Y_h\left(z\right)}{X_h\left(z\right)}=\frac{K_{\mathrm{ih}}{(z-1)}^2}{z^2-2\cos \left({\mathrm{\ω}}_h{T}_s\right)z+1}$

Wherein, K _ihbe the integral parameter that h subharmonic is corresponding, ω _hcentered by frequency, and ω _h=h ω ₀, ω _hfollowed by angular frequency ₀change, h is harmonic number, T _sfor the sampling time;

And the transfer function that modified model quasi resonant control adopts is:

$H_h^{\′}\left(z\right)=\frac{Y_h^{\′}\left(z\right)}{X_h^{\′}\left(z\right)}=\frac{K_{\mathrm{ih}}^{\′}{(z-1)}^2}{z^2-{2e}^{-{\mathrm{\ω}}_h\mathrm{\ζ}{T}_s}\cos \left({\mathrm{\ω}}_h\sqrt{1-{\mathrm{\ζ}}^2}{T}_s\right)z+e^{-2{\mathrm{\ω}}_h\mathrm{\ζ}{T}_s}}$

Wherein, K ' _ihfor the integral parameter that h subharmonic is corresponding, ω _hcentered by frequency, and ω _h=h ω ₀, ω _hfollowed by angular frequency ₀change, h is harmonic number, T _sfor the sampling time, ζ is damping coefficient;

And the transfer function that PI controller adopts is:

$\mathrm{PI}\left(z\right)=K_P(1+\frac{K_{I}z}{z-1})$

Wherein, K _pfor scale parameter, K _ifor integral parameter.

For above-mentioned two kinds of resonant controller, as shown in Figure 5 and Figure 6, wherein, the parameter of resonant controller is with centre frequency ω to its concrete theory diagram _hchange, and ω _h=h ω ₀, therefore also follow angular frequency ₀change, thus realize the frequency adaptation of resonant controller.

The voltage u that step S2 calculates by S6, voltage feed-forward control module _gd, u _gq, u _g0and the output controlled quentity controlled variable u calculated in step S5 _d, u _q, u ₀superpose, obtain controlled quentity controlled variable V _d, V _q, V ₀;

S7, dq0-abc coordinate transformation module is according to above-mentioned phase angle θ, the controlled quentity controlled variable V obtained by step S6 _d, V _q, V ₀from dq0 coordinate system transformation to the controlled quentity controlled variable V abc coordinate system _a, V _b, V _c;

S8, SPWM module is according to controlled quentity controlled variable V _a, V _b, V _cobtain corresponding switch controlling signal, and according to this control signal control each IGBT of three level VSI open shutoff.

Fig. 7 is under mains frequency rated condition, adopts method of the present invention to Active Power Filter-APF compensation effect analogous diagram.

In the present embodiment, be load current, APF offset current and power network current after compensating from top to down in Fig. 7 (a); It is the rear power network current spectrogram of load current and compensation in Fig. 7 (b); As can be seen from the figure, resonant controller loses compensation ability to more than 19 times harmonic waves, and quasi resonant control can carry out limited compensation to 23 and 25 subharmonic, has wider compensation bandwidth than resonant controller.Load current resultant distortion rate (THD) is 29%, and power network current resultant distortion rate (THD) after compensating is if adopting resonance to control is 6.6%, and adopting quasi-resonance to control is 4.4%.

Fig. 8 is under mains frequency surging condition, adopts or does not adopt method of the present invention to Active Power Filter-APF compensation effect analogous diagram.

In the present embodiment, in Fig. 8, (a) is simulation waveform figure when not adopting patent of the present invention.As can be seen from the figure, when 0.1s, mains frequency steps to 55Hz from 50Hz, and power network current waveform is obviously deteriorated, and the compensation effect of Active Power Filter-APF is obviously deteriorated.

In Fig. 8, (b) is simulation waveform figure when adopting patent of the present invention.As can be seen from the figure, when 0.1s, mains frequency steps to 55Hz from 50Hz, and power network current waveform has no change, and the compensation effect of Active Power Filter-APF recovers in two grid cycle.

In Fig. 8, (c) is simulation waveform figure when adopting patent of the present invention.As can be seen from the figure, when 0.1s, mains frequency steps to 45Hz from 50Hz, and power network current waveform has no change, and the compensation effect of Active Power Filter-APF recovers in two grid cycle.

The mains frequency accommodation can finding out this control method by Fig. 8 (b) and Fig. 8 (c) at least can to mains frequency ± 5Hz.

Although be described the illustrative embodiment of the present invention above; so that those skilled in the art understand the present invention; but should be clear; the invention is not restricted to the scope of embodiment; to those skilled in the art; as long as various change to limit and in the spirit and scope of the present invention determined, these changes are apparent, and all innovation and creation utilizing the present invention to conceive are all at the row of protection in appended claim.

Claims (3)

1. a frequency self-adaption modified model resonance control method for Active Power Filter-APF, is characterized in that, comprise the following steps:

(1), PLL phase-locked loop module is according to line voltage u _gget phase angle θ and the angular frequency of line voltage ₀;

(2), abc-dq0 coordinate transformation module according to phase angle θ, by line voltage u _gfrom abc coordinate system transformation to the voltage u dq0 coordinate system _gd, u _gq, u _g0, simultaneously by three level VSI ac-side current i ₁from abc coordinate system transformation to the current i dq0 coordinate system _1d, i _1q, i ₁₀;

(3) output active current set-point, is calculated with neutral current set-point

DC voltage control module is by the set-point of three level VSI DC voltage and voltage u between three level VSI-positive bus-bar and neutral point _dc1do to differ from again and voltage u between three level VSI negative busbar and neutral point _dc2differ from, the difference obtained is carried out PI control, obtains active current set-point simultaneously by voltage u between three level VSI positive bus-bar and neutral point _dc1and voltage u between negative busbar and neutral point _dc2differ from, the difference obtained is carried out PI control, obtains neutral current set-point

(4), Harmonic currents detection module is by load current i _lcarry out discrete Fourier transform (DFT) and obtain harmonic current i _ldh, i _lqh, i _l0h;

(5), current control module calculates and exports controlled quentity controlled variable u _d, u _q, u ₀

(5.1), calculating current Δ i _d: by active current set-point with harmonic current i _ldhsummation again with current i _1ddiffer from, obtain $\mathrm{\Δ}{i}_d=i_d^{*}+i_{\mathrm{Ldh}}-i_{1d};$

(5.2), calculating current Δ i _q: by harmonic current i _lqhwith current i _1qdiffer from, obtain Δ i _q=i _lqh-i _1q;

(5.3), calculating current Δ i ₀: by neutral current set-point with harmonic current i _l0hsummation again with again with current i ₁₀differ from, obtain $\mathrm{\Δ}{i}_0=i_0^{*}+i_{L0h}+i_{10};$

(5.4), current control module is according to above-mentioned angular frequency ₀, by the Δ i calculated _d, Δ i _q, Δ i ₀be sent to resonant controller and PI controller successively, obtain exporting controlled quentity controlled variable u _d, u _q, u ₀;

(6), voltage feed-forward control module is by described for step (2) voltage u _gd, u _gq, u _g0and the output controlled quentity controlled variable u described in step (5.4) _d, u _q, u ₀superpose, obtain controlled quentity controlled variable V _d, V _q, V ₀;

(7), dq0-abc coordinate transformation module according to above-mentioned phase angle θ, by the controlled quentity controlled variable V described in step (6) _d, V _q, V ₀from dq0 coordinate system transformation to the controlled quentity controlled variable V abc coordinate system _a, V _b, V _c;

(8), the controlled quentity controlled variable V of SPWM module according to step (7) _a, V _b, V _cobtain corresponding switch controlling signal, then control with this switch controlling signal three level VSI each IGBT open shutoff.

2. frequency self-adaption modified model resonance control method according to claim 1, is characterized in that, described current control module comprises modified model resonant controller and PI controller;

The transfer function of described modified model resonant controller is:

$H_h\left(z\right)=\frac{Y_h\left(z\right)}{X_h\left(z\right)}=\frac{K_{\mathrm{ih}}{(z-1)}^2}{z^2-2\cos \left({\mathrm{\ω}}_h{T}_s\right)z+1}$

Wherein, K _ihbe the integral parameter that h subharmonic is corresponding, ω _hcentered by frequency, and ω _h=h ω ₀, ω _hfollowed by angular frequency ₀change, T _sfor the sampling time;

The transfer function of described PI controller is:

$\mathrm{PI}\left(z\right)=K_P(1+\frac{K_{I}z}{z-1})$

Wherein, K _pfor scale parameter, K _ifor integral parameter.

3. frequency self-adaption modified model resonance control method according to claim 2, is characterized in that, described modified model resonant controller can replace with modified model quasi resonant control;

The transfer function of described modified model quasi resonant control is:

$H_h^{\′}\left(z\right)=\frac{Y_h^{\′}\left(z\right)}{X_h^{\′}\left(z\right)}=\frac{K_{\mathrm{ih}}^{\′}{(z-1)}^2}{z^2-2e^{-{\mathrm{\ω}}_h\mathrm{\ζ}{T}_s}\cos \left({\mathrm{\ω}}_h\sqrt{1-{\mathrm{\ζ}}^2}{T}_s\right)z+e^{-2{\mathrm{\ω}}_h\mathrm{\ζ}{T}_s}}$

Wherein, K ' _ihfor the integral parameter that h subharmonic is corresponding, ω _hcentered by frequency, and ω _h=h ω ₀, ω _hfollowed by angular frequency ₀change, h is harmonic number, T _sfor the sampling time, ζ is damping coefficient.