CN104578861A - Microgrid multi-inverter parallel-control method based on frequency division virtual complex impedance - Google Patents

Abstract

The invention discloses a microgrid multi-inverter parallel-control method based on frequency division virtual complex impedance, which is suitable for a multi-inverter parallel-control system with a nonlinear load for a low-voltage microgrid. The microgrid multi-inverter parallel-control method comprises the following steps: performing frequency division on a line current by virtue of a band pass filter by adopting a robust droop control strategy of resistance equivalent output impedance, simultaneously multiplying a fundamental current by a virtual complex impedance containing a resistance-capacitance component, designing that each parallel connection inverter output impedance is resistive in a fundamental band; and respectively multiplying each high-frequency current by different virtual inductive impedances, indicating that a harmonic frequency band inverter output impedance is inductive so as to be limited by the robust droop control strategy of resistance equivalent output impedance, so that the influence of a high-frequency harmonic current to inverter parallel-control is avoided. According to the microgrid multi-inverter parallel-control method, the defect of a conventional method is overcome, and good control effect is achieved in the multi-inverter parallel-control system with the nonlinear load for the low-voltage microgrid.

Description

A kind of micro-capacitance sensor multi-inverter parallel control method based on the virtual complex impedance of frequency division

Technical field

The present invention relates to a kind of micro-capacitance sensor multi-inverter parallel control method based on the virtual complex impedance of frequency division, belong to distributed power generation and electric and electronic technical field.

Background technology

In order to solve the technical barrier of distributed power source access electrical network, the electric power system scholars that are correlated with propose the concept of micro-capacitance sensor.Micro-capacitance sensor consists of the network interconnection decline source, energy conversion device and local load of distribution, can teaching display stand control, the Partial discharge system of protect and manage.In micro-capacitance sensor, great majority distribution declines source all by inverter interface incoming transport bus, thus defines a kind of multi-inverter parallel running environment.

The key difficulties problem of low-voltage micro-capacitance sensor when islet operation be line resistance much larger than circuit induction reactance, and which kind of droop control method of embody rule, depends on inverter output impedance and line impedance sum, i.e. the characteristic of the equivalent output impedance of inverter.In addition, if during low-voltage micro-capacitance sensor band nonlinear load, can produce harmonic current in circuit, the harmonic current how reducing even to eliminate nonlinear load generation runs the impact produced on low-voltage micro-capacitance sensor multi-inverter parallel, become study hotspot and difficult point.

Content related with the present patent application mainly contains following several sections of documents in the prior art:

Document one is Zhang Qinghai, Luo An, Chen Yandong, Peng Chuwu, Peng from being better than submission on May 4th, 2012, in June, 2014 is published in " shunt chopper output impedance analysis and the voltage control strategy " of " electrotechnics journal " the 29th on volume the 6th phase one literary composition.This article is when analyzing low-voltage micro-capacitance sensor multi-inverter parallel control strategy, propose a kind of voltage control strategy based on virtual complex impedance, in the virtual complex impedance of introducing, include virtual resistance and virtual induction reactance simultaneously: virtual resistance makes resistive component in inverter output impedance increase; Virtual induction reactance is negative value, the inductive component reduced in inverter output impedance.Finally make inverter equivalent output impedance present pure resistive characteristic, and obtain good experiment effect in the experiment of low-voltage micro-capacitance sensor band pure resistive loads.But if change pure resistive loads in experiment into nonlinear load, then have harmonic wave and produce, the control method that this article proposes will limitation.

Document two is that the people such as Peng Ziqiang, Luo An, Chen Yandong contributed on May 17th, 2013, is published in " the multi-inverter parallel control strategy based on frequency division virtual resistance " of " electric power network technique " the 37th on volume o. 11th one literary composition in November, 2013.This article, for the multi-inverter parallel system of low-voltage micro-capacitance sensor band nonlinear load, proposes a kind of multi-inverter parallel control strategy of frequency division virtual resistance.This article, by introducing larger virtual resistance to fundamental current, realizes inverter output impedance and presents ohmic characteristic, but compared with the virtual complex impedance proposed in document one, can not change the perceptual weight in inverter output impedance; In addition, the processing method of this article to all the other each higher harmonic currents is identical with fundamental current, and the inverter output impedance that harmonic wave frequency range can be made so corresponding still presents resistive, and in reference voltage and reference current amount, the impact of harmonic current still exists.

Documents three is Hunan University in the Chinese patent CN102842921B that on September 28th, 2012 applies for, on July 9th, 2014 authorizes, and which discloses a kind of micro-capacitance sensor multi-inverter parallel voltage control method of robust power droop control.For the every platform inverter in micro-capacitance sensor, robust power droop control device is adopted to calculate and synthesize inverter output reference voltage; By introducing the virtual complex impedance containing resistive component and induction reactance component, adopt the many loop voltags control method controlled based on virtual impedance and quasi-resonance PR, make inverter output impedance under power frequency condition in purely resistive, thus realize the operation of micro-capacitance sensor multi-inverter parallel and power-sharing, and enhance the robustness of the micro-capacitance sensor parallel system logarithm value error of calculation, parameter drift, noise jamming etc.But method involved by this patent is obvious to the multi-inverter parallel control system implementation result under linear load condition, whether is applicable to the low-voltage micro-capacitance sensor multi-inverter parallel control system being with nonlinear load, analyzes and researches.

Documents four is that Hunan University is in the Chinese patent CN103227581B that on May 10th, 2013 applies for, on January 22nd, 2014 authorizes, which disclose a kind of inverter parallel harmonic circulating current suppressing method of harmonic wave droop control, comprise harmonic wave droop control, power droop control and voltage control.Harmonic wave droop control converts frequency division by fast Fourier FFT and detects harmonics power, according to harmonic wave droop characteristic, calculates the harmonics reference voltage that inverter exports; Power droop control calculates first-harmonic reference voltage; Both synthesis as inverter output reference voltage, thus reduce inverter output voltage distortion effectively, suppress inverter m-Acetyl chlorophosphonazo circulation, realize power and accurately distribute.Method involved by this patent also adopts harmonic wave droop control respectively for each high order harmonic component while adopting power droop control to fundametal compoment; While calculating first-harmonic reference voltage, also need to calculate each harmonic reference voltage, finally again this tittle is superposed.Like this, the amount of calculation of implementation procedure is comparatively large, and the complexity of calculation procedure is bound to, and influential system is quick, real-time response.

In sum, what solve in prior art that harmonic current in low-voltage micro-capacitance sensor controls inverter parallel preferably affects this technical barrier.

Summary of the invention

For the deficiencies in the prior art, the invention provides a kind of micro-capacitance sensor multi-inverter parallel control method based on the virtual complex impedance of frequency division.

Technical scheme of the present invention is as follows:

A kind of micro-capacitance sensor multi-inverter parallel control method based on the virtual complex impedance of frequency division, each distributed generation unit main circuit comprises micro-source, H-bridge inverter circuit, LC filter circuit, described micro-source, H-bridge inverter circuit, LC filter circuit connect in turn, be connected to ac bus finally by connection line through switch, ac bus is connected to nonlinear load; Droop control part adopts the robust droop control strategy of resistive equivalent output impedance; By band pass filter to line current frequency division, extract each primary current, different virtual complex impedances is multiplied by respectively to fundamental current and each high-frequency current;

The concrete steps of the method are:

1) in the starting point in each sampling period, processor is by micro-source output voltage U _dc, filter capacitor voltage u _c, filter inductance current i _l, line current i _ocarry out respectively sampling and process;

2) according to two umber of beats value power calculation algorithms, by filter capacitor voltage u _c, filter inductance current i _lcalculate active power mean value P and reactive power mean value Q;

3) according to the robust droop control principle of resistive equivalent output impedance, discrete Fourier transform DFT is utilized to calculate filter capacitor voltage u _cat the effective value U of one-period _c, floating voltage amplitude reference value E ^*deduct U _c, the difference obtained is multiplied by COEFFICIENT K, then deducts the product of active power mean value P and droop control coefficient n, and its difference, through integral operation, obtains reference voltage amplitude E; Reactive power mean value Q and droop control Coefficient m long-pending, adds idler angular frequency reference value ω ^*, itself and be reference voltage angular frequency;

4) PLL phase-locked loop is to filter capacitor voltage u _cphase-locked, obtain starting phase angle φ; According to reference voltage amplitude E, reference voltage angular frequency and starting phase angle φ, the reference voltage u before the virtual complex impedance of frequency division is introduced in synthesis ^* _ref;

5) line current i _oextract respectively through band pass filter and obtain fundamental current i _o1, 3 subharmonic current i _o3and h subharmonic current i _oh;

6) fundamental current i _o1, 3 subharmonic current i _o3and h subharmonic current i _ohbe multiplied by corresponding virtual complex impedance R respectively ₁-sL ₁, sL ₃and sL _hafterwards, and it is as subtrahend, u ^* _refas minuend, carry out subtraction, the difference of operation result is Voltage loop reference voltage u _ref;

7) Voltage loop reference voltage u _ref, filter capacitor voltage u _c, micro-source output voltage U _dc, filter inductance current i _linput voltage and input current controller, regulates through outer voltage current inner loop, obtains modulation wave signal D;

8) modulation wave signal D and triangular carrier carry out bipolar modulation, draw the duty cycle signals of switching tube, through Drive Protecting Circuit, control opening and shutoff of H-bridge inverter circuit switching tube.

The control method of this programme for line resistance in low-voltage micro-capacitance sensor much larger than the feature of circuit induction reactance, virtual complex impedance simultaneously containing resistance capacitive component is adopted to fundamental current, designing each shunt chopper output impedance in fundamental frequency section is resistive, and such inverter output impedance and line impedance sum will present obvious resistive; During inverter parallel band nonlinear load, high-frequency harmonic electric current can be produced in circuit, each high-frequency current is multiplied by different virtual induction reactance respectively, then the output impedance of harmonic wave frequency range inverter is inductive, robust droop control strategy by resistive equivalent output impedance limited, thus avoids the impact that high-frequency harmonic electric current controls inverter parallel.

Preferred according to the present invention, described step 2) in, two umber of beats value power calculation algorithms, its computing formula is:

$\left\{\begin{array}{c}P=\frac{U_{\mathrm{ck}}{I}_{\mathrm{Lk}}+U_{c(k+1)}{I}_{L(k+1)}-\cos \left(\frac{2\mathrm{\π}}{N}\right)[U_{\mathrm{ck}}{I}_{L(k+1)}+U_{c(k+1)}{I}_{\mathrm{Lk}}]}{2{\sin }^2\left(\frac{2\mathrm{\π}}{N}\right)}\\ Q=\frac{U_{\mathrm{ck}}{I}_{L(k+1)}-U_{c(k+1)}{I}_{\mathrm{Lk}}}{2\sin \left(\frac{2\mathrm{\π}}{N}\right)}\end{array}\right.---\left(i\right);$

Wherein, N is the ratio in power frequency period and sampling period, U _ck, U _{c (k+1)}be respectively kth, a k+1 sampling instant filter capacitor voltage magnitude, I _lk, I _{l (k+1)}be respectively kth, a k+1 sampling instant filter inductance current amplitude.

The present invention adopts as above computational methods, utilizes the real-time rated output of front and back two umber of beats value of voltage, electric current, reduces computation delay, improve the dynamic property of parallel system.

Preferred according to the present invention, described step 3) in, the computing formula of reference voltage amplitude E and reference voltage angular frequency is:

$\left\{\begin{array}{c}E=\frac{1}{s}[K(E^{*}-U_c)-\mathrm{nP}]\\ \mathrm{\ω}={\mathrm{\ω}}^{*}+\mathrm{mQ}\end{array}\right.---\left(\mathrm{ii}\right);$

Wherein, s is complex frequency.

Preferred according to the present invention, described step 4) in, introduce the reference voltage u before the virtual complex impedance of frequency division ^* _refcomputing formula is:

$u_{\mathrm{ref}}^{*}=\sqrt{2}E\sin (\mathrm{\ωt}+\mathrm{\φ})---\left(\mathrm{iii}\right).$

, described step 5 preferred according to the present invention) in the transfer function of band pass filter be:

$i_{\mathrm{oh}}=\frac{2\mathrm{\ξh}{\mathrm{\ω}}_{0}s}{s^2+2\mathrm{\ξh}{\mathrm{\ω}}_{0}s+h^2{{\mathrm{\ω}}_0}^2}{i}_o---\left(\mathrm{iv}\right);$

Wherein, ξ is damping coefficient, ω ₀for first-harmonic angular frequency, h is principal wave harmonic wave number of times, and s is complex frequency.

Preferred according to the present invention, described step 6) in, Voltage loop reference voltage u _refcomputing formula be:

$u_{\mathrm{ref}}=u_{\mathrm{ref}}^{*}-(R_1-s{L}_1)i_{o1}-\underset{h=\mathrm{3,5},...}{\mathrm{\Σ}}s{L}_h{i}_{\mathrm{oh}}---\left(v\right);$

Wherein, s is complex frequency.

The present invention adopts as above computational methods, and fundamental current is multiplied by the virtual complex impedance simultaneously containing resistance capacitive component, each shunt chopper output impedance is resistive in fundamental frequency section, adapts to low-voltage micro-capacitance sensor multi-inverter parallel control system Electric parameter characteristics; Each high-frequency current is multiplied by different virtual induction reactance respectively, then the output impedance of harmonic wave frequency range inverter is inductive.

Preferred according to the present invention, described step 7) in, Voltage loop reference voltage u _refwith filter capacitor voltage u _cdifference through the modulation of PI controller, export inner ring current reference value i _ref, discrete adjustment formula is:

$\left\{\begin{array}{c}\mathrm{\Δu}\left(k\right)=u_{\mathrm{ref}}\left(k\right)-u_c\left(k\right)\\ i_{\mathrm{ref}}\left(k\right)=i_{\mathrm{ref}}(k-1)+K_p*(\mathrm{\Δu}\left(k\right)-\mathrm{\Δu}(k-1))+\mathrm{\Δu}\left(k\right)*\frac{T_c}{K_i}\end{array}\right.---\left(\mathrm{vi}\right);$

Wherein, K _pand K _ibe respectively proportionality coefficient and the integral coefficient of pi regulator; T _cfor the sampling period.

I _refwith filter inductance current i _ldifference, be multiplied by L/T _c, add u _c, be finally multiplied by d/U _dc, just obtain modulation wave signal D.The discrete formula of the modulation wave signal D that track with zero error exports is as follows:

$D\left(k\right)=\frac{d}{U_{\mathrm{dc}}}[u_c\left(k\right)+\frac{L}{T_c}(i_{\mathrm{ref}}\left(k\right)-i_L\left(k\right))]---\left(\mathrm{vii}\right);$

In formula, d is the index of modulation, and L is filter inductance value, T _cfor the sampling period, i _reffor exporting inner ring current reference value, D (k) is the calculated value of the modulation wave signal D of a kth sampling instant, u _ck () is the u of a kth sampling instant _csampled value, i _refk () is the i of a kth sampling instant _refsampled value, i _lk () is the i of a kth sampling instant _lsampled value.

Preferred according to the present invention, described step 7) in, in the specific formula for calculation of modulation wave signal D, the span of d is 0.95 ~ 1.0.

The present invention adopts electric current and voltage double loop control, and outer voltage adopts PI to control, and current inner loop adopts track with zero error, can to outside disturbance response speed faster and control procedure without overshoot.

Beneficial effect of the present invention:

Compared with prior art, the beneficial effect that the present invention has is:

1, by band pass filter to line current frequency division, extract each primary current, respectively different virtual impedances is multiplied by each primary current: the virtual complex impedance of capacitance-resistance is adopted to fundamental current, makes the output impedance of fundamental frequency section inverter be resistive, is applicable to low-voltage micro-capacitance sensor multi-inverter parallel and controls; Adopt virtual induction reactance to all the other individual harmonic currents, make the output impedance of harmonic wave frequency range inverter be inductive, the robust droop control method by resistive equivalent output impedance limited, and all eliminates the impact of harmonic current in final reference voltage and reference current.

2, two umber of beats value power meter algorithms are adopted, utilize the real-time rated output of front and back two umber of beats value of voltage, electric current, reduce computation delay, a large amount of processor memory space is eliminated in numeric field, lower quantization error, calculating are simply, for dynamic change, only need a sampling period just can recover actual value, improve the dynamic property of parallel system.

3, apply dead-beat control method in current inner loop controls, can to outside disturbance response speed faster and control procedure without overshoot.

Accompanying drawing explanation

Fig. 1 is the micro-capacitance sensor multi-inverter parallel Control system architecture schematic diagram based on the virtual complex impedance of frequency division of band nonlinear load of the present invention;

Fig. 2 is the micro-capacitance sensor multi-inverter parallel control method schematic diagram that the present invention is based on the virtual complex impedance of frequency division;

Fig. 3 is the present invention two umber of beats value power calculation algorithms schematic diagram;

Fig. 4 is electric current and voltage control block diagram of the present invention.

Embodiment

Below in conjunction with embodiment and Figure of description, technology contents of the present invention is described in detail, but is not limited thereto.

Fig. 1 is the micro-capacitance sensor multi-inverter parallel Control system architecture schematic diagram based on the virtual complex impedance of frequency division of band nonlinear load, each distributed generation unit main circuit comprises micro-source, H-bridge inverter circuit, LC filter circuit, described micro-source, H-bridge inverter circuit, LC filter circuit connect in turn, be connected to ac bus finally by connection line through switch, ac bus is connected to nonlinear load.

Fig. 2 is the micro-capacitance sensor multi-inverter parallel control method schematic diagram based on the virtual complex impedance of frequency division.Droop control part adopts the robust droop control strategy of resistive equivalent output impedance, by band pass filter to line current frequency division, extract each primary current: for line resistance in low-voltage micro-capacitance sensor much larger than the feature of circuit induction reactance, virtual complex impedance simultaneously containing resistance capacitive component is adopted to fundamental current, designing each shunt chopper output impedance in fundamental frequency section is resistive, and such inverter output impedance and line impedance sum will present obvious resistive; During inverter parallel band nonlinear load, high-frequency harmonic electric current can be produced in circuit, each high-frequency current is multiplied by different virtual induction reactance respectively, then the output impedance of harmonic wave frequency range inverter is inductive, robust droop control strategy by resistive equivalent output impedance limited, thus avoids the impact that high-frequency harmonic electric current controls inverter parallel.In rated output link, adopt two umber of beats value power calculation algorithms, utilize the real-time rated output of front and back two umber of beats value of voltage, electric current, reduce computation delay, improve the dynamic property of parallel system.Adopt electric current and voltage double loop control, outer voltage adopts PI to control, and current inner loop adopts track with zero error, can to outside disturbance response speed faster and control procedure without overshoot.

Embodiment 1,

Elaborate the realization of the micro-capacitance sensor multi-inverter parallel control method based on the virtual complex impedance of frequency division below, the concrete steps of the method are:

1) in the starting point in each sampling period, processor is by micro-source output voltage U _dc, filter capacitor voltage u _c, filter inductance current i _l, line current i _ocarry out respectively sampling and process;

2) according to two umber of beats value power calculation algorithms, by filter capacitor voltage u _c, filter inductance current i _lcalculate active power mean value P and reactive power mean value Q;

3) according to the robust droop control principle of resistive equivalent output impedance, discrete Fourier transform DFT is utilized to calculate filter capacitor voltage u _cat the effective value U of one-period _c, floating voltage amplitude reference value E ^*deduct U _c, the difference obtained is multiplied by COEFFICIENT K, then deducts the product of active power mean value P and droop control coefficient n, and its difference, through integral operation, obtains reference voltage amplitude E; Reactive power mean value Q and droop control Coefficient m long-pending, adds idler angular frequency reference value ω ^*, itself and be reference voltage angular frequency;

4) PLL phase-locked loop is to filter capacitor voltage u _cphase-locked, obtain starting phase angle φ; According to reference voltage amplitude E, reference voltage angular frequency and starting phase angle φ, the reference voltage u before the virtual complex impedance of frequency division is introduced in synthesis ^* _ref;

5) line current i _oextract respectively through band pass filter and obtain fundamental current i _o1, 3 subharmonic current i _o3and h subharmonic current i _oh;

6) fundamental current i _o1, 3 subharmonic current i _o3and h subharmonic current i _ohbe multiplied by corresponding virtual complex impedance R respectively ₁-sL ₁, sL ₃and sL _hafterwards, and it is as subtrahend, u ^* _refas minuend, carry out subtraction, the difference of operation result is the reference voltage u of Voltage loop _ref;

7) Voltage loop reference voltage u _ref, filter capacitor voltage u _c, micro-source output voltage U _dc, filter inductance current i _linput voltage and input current controller, regulates through outer voltage current inner loop, obtains modulation wave signal D;

8) modulation wave signal D and triangular carrier carry out bipolar modulation, draw the duty cycle signals of switching tube, through Drive Protecting Circuit, control opening and shutoff of H-bridge inverter circuit switching tube.

Embodiment 2,

A kind of micro-capacitance sensor multi-inverter parallel control method based on the virtual complex impedance of frequency division according to embodiment 1, further, described step 2) in, the concrete formula of active power mean value P and reactive power mean value Q is:

$\left\{\begin{array}{c}P=\frac{U_{\mathrm{ck}}{I}_{\mathrm{Lk}}+U_{c(k+1)}{I}_{L(k+1)}-\cos \left(\frac{2\mathrm{\π}}{N}\right)[U_{\mathrm{ck}}{I}_{L(k+1)}+U_{c(k+1)}{I}_{\mathrm{Lk}}]}{2{\sin }^2\left(\frac{2\mathrm{\π}}{N}\right)}\\ Q=\frac{U_{\mathrm{ck}}{I}_{L(k+1)}-U_{c(k+1)}{I}_{\mathrm{Lk}}}{2\sin \left(\frac{2\mathrm{\π}}{N}\right)}\end{array}\right.---\left(i\right);$

Wherein, N is the ratio in power frequency period and sampling period, U _ck, U _{c (k+1)}be respectively kth, a k+1 sampling instant filter capacitor voltage magnitude, I _lk, I _{l (k+1)}be respectively kth, a k+1 sampling instant filter inductance current amplitude.

As shown in Figure 3, Fig. 3 is two umber of beats value power calculation algorithms schematic diagrames.Below two umber of beats value power calculation algorithms are derived in detail.

If filter capacitor voltage u in time domain _cwith filter inductance current i _lexpression formula be respectively u _c(t)=U _csin (ω ₀t+ φ), i _l(t)=I _lsin (ω ₀t+ φ _l), ω ₀for first-harmonic angular frequency, U _c, I _lbe respectively voltage and current amplitude, φ _lfor current phase angle.To u in time domain _c(t)=U _csin (ω ₀t+ φ) sampling, then a kth sampled value is designated as u _ck (), has:

$u_c\left(k\right)=U_{\mathrm{ck}}\sin (k\frac{2\mathrm{\π}}{N}+\mathrm{\φ})=U_{\mathrm{ck}}\cos \mathrm{\φ}\sin \left(k\frac{2\mathrm{\π}}{N}\right)+U_{\mathrm{ck}}\sin \mathrm{\φ}\cos \left(k\frac{2\mathrm{\π}}{N}\right)---\left(\mathrm{vii}\right);$

Wherein, N is the ratio in power frequency period and sampling period.

From formula (VIII),

$u_c(k+1)=U_{c(k+1)}\cos \mathrm{\φ}\sin \left((k+1)\frac{2\mathrm{\π}}{N}\right)+U_{c(k+1)}\sin \mathrm{\φ}\cos \left((k+1)\frac{2\mathrm{\π}}{N}\right)---\left(\mathrm{ix}\right);$

Further, can obtain:

$\left[\begin{array}{c}{u}_c\left(k\right)\\ u_c(k+1)\end{array}\right]=\left[\begin{array}{cc}\sin \left(k\frac{2\mathrm{\π}}{N}\right)& \cos \left(k\frac{2\mathrm{\π}}{N}\right)\\ \sin \left((k+1)\frac{2\mathrm{\π}}{N}\right)& \cos \left((k+1)\frac{2\mathrm{\π}}{N}\right)\end{array}\right]\left[\begin{array}{cc}{U}_{\mathrm{ck}}& \cos \mathrm{\φ}\\ U_{c(k+1)}& \sin \mathrm{\φ}\end{array}\right]---\left(x\right);$

Definition S _k=sin (2 π k/N), T _k=cos (2 π k/N), order

$\left[\begin{array}{c}{u}_c\left(k\right)\\ u_c(k+1)\end{array}\right]=\left[\begin{array}{cc}{S}_k& T_k\\ S_{k+1}& T_{k+1}\end{array}\right]\left[\begin{array}{cc}{U}_{\mathrm{ck}}& \cos \mathrm{\φ}\\ U_{c(k+1)}& \sin \mathrm{\φ}\end{array}\right]=V_k\left[\begin{array}{cc}{U}_{\mathrm{ck}}& \cos \mathrm{\φ}\\ U_{c(k+1)}& \sin \mathrm{\φ}\end{array}\right]---\left(\mathrm{xi}\right);$

Then have

$\left[\begin{array}{cc}{U}_{\mathrm{ck}}& \cos \mathrm{\φ}\\ U_{c(k+1)}& \sin \mathrm{\φ}\end{array}\right]=V_k^{-1}\left[\begin{array}{c}{u}_c\left(k\right)\\ u_c(k+1)\end{array}\right]---\left(\mathrm{xii}\right);$

Wherein for matrix V _kinverse matrix, further can be in the hope of:

$V_k^{-1}=\left[\begin{array}{cc}\sin (2\mathrm{\πk}/N)-\frac{\cos (2\mathrm{\π}/N)\cos (2\mathrm{\πk}/N)}{\sin (2\mathrm{\π}/N)}& \frac{\cos (2\mathrm{\πk}/N)}{\sin (2\mathrm{\π}/N)}\\ \cos (2\mathrm{\πk}/N)+\frac{\cos (2\mathrm{\π}/N)\sin (2\mathrm{\πk}/N)}{\sin (2\mathrm{\π}/N)}& \frac{\sin (2\mathrm{\πk}/N)}{\sin (2\mathrm{\πk}/N)}\end{array}\right]---\left(\mathrm{xiii}\right);$

According to formula (xii), can be derived from equally

$\left[\begin{array}{cc}{I}_{\mathrm{Lk}}& \cos {\mathrm{\φ}}_L\\ I_{L(k+1)}& \sin {\mathrm{\φ}}_L\end{array}\right]=V_k^{-1}\left[\begin{array}{c}{i}_L\left(k\right)\\ i_L(k+1)\end{array}\right]---\left(\mathrm{xiv}\right);$

Formula (xii) and formula (xiv) are substituted into traditional active power and reactive power calculation expression formula, following two umber of beats value rating formulas can be obtained:

$\left\{\begin{array}{c}P=\frac{U_{\mathrm{ck}}{I}_{\mathrm{Lk}}+U_{c(k+1)}{I}_{L(k+1)}-\cos \left(\frac{2\mathrm{\π}}{N}\right)[U_{\mathrm{ck}}{I}_{L(k+1)}+U_{c(k+1)}{I}_{\mathrm{Lk}}]}{2{\sin }^2\left(\frac{2\mathrm{\π}}{N}\right)}\\ Q=\frac{U_{\mathrm{ck}}{I}_{L(k+1)}-U_{c(k+1)}{I}_{\mathrm{Lk}}}{2\sin \left(\frac{2\mathrm{\π}}{N}\right)}\end{array}\right.---\left(i\right);$

Wherein, U _ck, U _{c (k+1)}be respectively kth, a k+1 sampling instant filter capacitor voltage magnitude, I _lk, I _{l (k+1)}be respectively kth, a k+1 sampling instant filter inductance current amplitude.

Can find out according to formula (I), N is definite value, sin (2 π/N), T _k=cos (2 π/N) is definite value, the size of active power and reactive power only just can be calculated according to the amplitude information of front and back two beat voltage, electric current, eliminate a large amount of processor memory spaces in numeric field, quantization error reduces, and calculates and greatly simplifies.For dynamic change, only need a sampling period just can recover actual value.

Embodiment 3,

A kind of micro-capacitance sensor multi-inverter parallel control method based on the virtual complex impedance of frequency division according to embodiment 1, further, described step 3) in, the concrete calculating formula of reference voltage amplitude E and reference voltage angular frequency is:

$\left\{\begin{array}{c}E=\frac{1}{s}[K(E^{*}-U_c)-\mathrm{nP}]\\ \mathrm{\ω}={\mathrm{\ω}}^{*}+\mathrm{mQ}\end{array}\right.---\left(\mathrm{ii}\right);$

Wherein, s is complex frequency.

Embodiment 4,

A kind of micro-capacitance sensor multi-inverter parallel control method based on the virtual complex impedance of frequency division according to embodiment 1, further, described step 4) in, u ^* _refcomputing formula be:

$u_{\mathrm{ref}}^{*}=\sqrt{2}E\sin (\mathrm{\ωt}+\mathrm{\φ})---\left(\mathrm{iii}\right).$

Embodiment 5,

A kind of micro-capacitance sensor multi-inverter parallel control method based on the virtual complex impedance of frequency division according to embodiment 1, further, described step 5) in, the transfer function of band pass filter is:

$i_{\mathrm{oh}}=\frac{2\mathrm{\ξh}{\mathrm{\ω}}_{0}s}{s^2+2\mathrm{\ξh}{\mathrm{\ω}}_{0}s+h^2{{\mathrm{\ω}}_0}^2}{i}_o---\left(\mathrm{iv}\right);$

Wherein, ξ is damping coefficient, ω ₀for first-harmonic angular frequency, h is principal wave harmonic wave number of times, and s is complex frequency.

Embodiment 6,

A kind of micro-capacitance sensor multi-inverter parallel control method based on the virtual complex impedance of frequency division according to embodiment 1, further, described step 6) in, u _refspecific formula for calculation be:

$u_{\mathrm{ref}}=u_{\mathrm{ref}}^{*}-(R_1-s{L}_1)i_{o1}-\underset{h=\mathrm{3,5},...}{\mathrm{\Σ}}s{L}_h{i}_{\mathrm{oh}}---\left(v\right);$

Wherein, s is complex frequency.

Embodiment 7,

As shown in Figure 4, Figure 4 shows that electric current and voltage control block diagram.Adopt electric current and voltage double loop control, outer voltage adopts PI to control, and current inner loop adopts track with zero error, can to outside disturbance response speed faster and control procedure without overshoot.

A kind of micro-capacitance sensor multi-inverter parallel control method based on the virtual complex impedance of frequency division according to embodiment 1, further, described step 7) in, Voltage loop reference voltage u _refwith filter capacitor voltage u _cdifference through the modulation of PI controller, export inner ring current reference value i _ref, discrete adjustment formula is:

$\left\{\begin{array}{c}\mathrm{\Δu}\left(k\right)=u_{\mathrm{ref}}\left(k\right)-u_c\left(k\right)\\ i_{\mathrm{ref}}\left(k\right)=i_{\mathrm{ref}}(k-1)+K_p*(\mathrm{\Δu}\left(k\right)-\mathrm{\Δu}(k-1))+\mathrm{\Δu}\left(k\right)*\frac{T_c}{K_i}\end{array}\right.---\left(\mathrm{vi}\right);$

In formula, K _pand K _ibe respectively proportionality coefficient and the integral coefficient of pi regulator; T _cfor the sampling period.

I _refwith filter inductance current i _ldifference, be multiplied by L/T _c, add u _c, be finally multiplied by d/U _dc, just obtain modulation wave signal D.The discrete formula of the modulation wave signal D that track with zero error exports is as follows:

$D\left(k\right)=\frac{d}{U_{\mathrm{dc}}}[u_c\left(k\right)+\frac{L}{T_c}(i_{\mathrm{ref}}\left(k\right)-i_L\left(k\right))]---\left(\mathrm{vii}\right);$

In formula, d is the index of modulation, and L is filter inductance value, T _cfor the sampling period, i _reffor exporting inner ring current reference value, D (k) is the calculated value of the modulation wave signal D of a kth sampling instant, u _ck () is the u of a kth sampling instant _csampled value, i _refk () is the i of a kth sampling instant _refsampled value, i _lk () is the i of a kth sampling instant _lsampled value.

Embodiment 8,

A kind of micro-capacitance sensor multi-inverter parallel control method based on the virtual complex impedance of frequency division according to embodiment 7, further, consider sampling error and control precision, d value is 0.97.

Claims (8)

1. the micro-capacitance sensor multi-inverter parallel control method based on the virtual complex impedance of frequency division, each distributed generation unit main circuit comprises micro-source, H-bridge inverter circuit, LC filter circuit, described micro-source, H-bridge inverter circuit, LC filter circuit connect in turn, be connected to ac bus finally by connection line through switch, ac bus is connected to nonlinear load; Droop control part adopts the robust droop control strategy of resistive equivalent output impedance; By band pass filter to line current frequency division, extract each primary current, different virtual complex impedances is multiplied by respectively to fundamental current and each high-frequency current; The concrete steps of the method are:

1) in the starting point in each sampling period, processor is by micro-source output voltage U _dc, filter capacitor voltage u _c, filter inductance current i _l, line current i _ocarry out respectively sampling and process;

2) according to two umber of beats value power calculation algorithms, by filter capacitor voltage u _c, filter inductance current i _lcalculate active power mean value P and reactive power mean value Q;

3) according to the robust droop control principle of resistive equivalent output impedance, discrete Fourier transform DFT is utilized to calculate filter capacitor voltage u _cat the effective value U of one-period _c, floating voltage amplitude reference value E ^*deduct U _c, the difference obtained is multiplied by COEFFICIENT K, then deducts the product of active power mean value P and droop control coefficient n, and its difference, through integral operation, obtains reference voltage amplitude E; Reactive power mean value Q and droop control Coefficient m long-pending, adds idler angular frequency reference value ω ^*, itself and be reference voltage angular frequency;

4) PLL phase-locked loop is to filter capacitor voltage u _cphase-locked, obtain starting phase angle φ; According to reference voltage amplitude E, reference voltage angular frequency and starting phase angle φ, the reference voltage u before the virtual complex impedance of frequency division is introduced in synthesis ^* _ref;

5) line current i _oextract respectively through band pass filter and obtain fundamental current i _o1, 3 subharmonic current i _o3and h subharmonic current i _oh;

6) fundamental current i _o1, 3 subharmonic current i _o3and h subharmonic current i _ohbe multiplied by corresponding virtual complex impedance R respectively ₁-sL ₁, sL ₃and sL _hafterwards, and it is as subtrahend, u ^* _refas minuend, carry out subtraction, the difference of operation result is Voltage loop reference voltage u _ref;

7) Voltage loop reference voltage u _ref, filter capacitor voltage u _c, micro-source output voltage U _dc, filter inductance current i _linput voltage and input current controller, regulates through outer voltage current inner loop, obtains modulation wave signal D;

8) modulation wave signal D and triangular carrier carry out bipolar modulation, draw the duty cycle signals of switching tube, through Drive Protecting Circuit, control opening and shutoff of H-bridge inverter circuit switching tube.

2. the micro-capacitance sensor multi-inverter parallel control method based on the virtual complex impedance of frequency division according to claim 1, is characterized in that, described step 2) in two umber of beats value power calculation algorithms, computing formula is:

$\left\{\begin{array}{c}P=\frac{U_{\mathrm{ck}}{I}_{\mathrm{Lk}}+U_{c(k+1)}{I}_{L(k+1)}-\cos \left(\frac{2\mathrm{\π}}{N}\right)[U_{\mathrm{ck}}{I}_{L(k+1)}+U_{c(k+1)}{I}_{\mathrm{Lk}}]}{2{\sin }^2\left(\frac{2\mathrm{\π}}{N}\right)}\\ Q=\frac{U_{\mathrm{ck}}{I}_{L(k+1)}-U_{c(k+1)}{I}_{\mathrm{Lk}}}{2\sin \left(\frac{2\mathrm{\π}}{N}\right)}\end{array}\right.---\left(i\right);$

Wherein, N is the ratio in power frequency period and sampling period, U _ck, U _{c (k+1)}be respectively kth, a k+1 sampling instant filter capacitor voltage magnitude, I _lk, I _{l (k+1)}be respectively kth, a k+1 sampling instant filter inductance current amplitude.

3. a kind of micro-capacitance sensor multi-inverter parallel control method based on the virtual complex impedance of frequency division according to claim 1, is characterized in that, described step 3) in, the computing formula of reference voltage amplitude E and reference voltage angular frequency is:

$\left\{\begin{array}{c}E=\frac{1}{s}[K(E^{*}-U_c)-\mathrm{nP}]\\ \mathrm{\ω}={\mathrm{\ω}}^{*+\mathrm{mQ}}\end{array}\right.---\left(\mathrm{ii}\right);$

Wherein, s is complex frequency.

4. a kind of micro-capacitance sensor multi-inverter parallel control method based on the virtual complex impedance of frequency division according to claim 1, is characterized in that, described step 4) in, introduce the reference voltage u before the virtual complex impedance of frequency division ^* _refcomputing formula is:

$u_{\mathrm{ref}}^{*}=\sqrt{2}E\sin (\mathrm{\ωt}+\mathrm{\φ})---\left(\mathrm{iii}\right).$

5. a kind of micro-capacitance sensor multi-inverter parallel control method based on the virtual complex impedance of frequency division according to claim 1, is characterized in that, described step 5) in the transfer function of band pass filter be:

$i_{\mathrm{oh}}=\frac{2\mathrm{\ξh}{\mathrm{\ω}}_{0}s}{s^2+2\mathrm{\ξh}{\mathrm{\ω}}_{0}s+h^2{{\mathrm{\ω}}_0}^2}{i}_o---\left(\mathrm{iv}\right);$

Wherein, ξ is damping coefficient, ω ₀for first-harmonic angular frequency, h is principal wave harmonic wave number of times, and s is complex frequency.

6. a kind of micro-capacitance sensor multi-inverter parallel control method based on the virtual complex impedance of frequency division according to claim 1, is characterized in that, described step 6) in, Voltage loop reference voltage u _refcomputing formula be:

$u_{\mathrm{ref}}=u_{\mathrm{ref}}^{*}-(R_1-s{L}_1)i_{o1}-\underset{h=\mathrm{3,5},...}{\mathrm{\Σ}}s{L}_h{i}_{\mathrm{oh}}---\left(v\right);$

Wherein, s is complex frequency.

7. a kind of micro-capacitance sensor multi-inverter parallel control method based on the virtual complex impedance of frequency division according to claim 1, is characterized in that, described step 7) middle Voltage loop reference voltage u _refwith filter capacitor voltage u _cdifference through the modulation of PI controller, export inner ring current reference value i _ref, discrete adjustment formula is:

$\left\{\begin{array}{c}\mathrm{\Δu}\left(k\right)=u_{\mathrm{ref}}\left(k\right)-u_c\left(k\right)\\ i_{\mathrm{ref}}\left(k\right)=i_{\mathrm{ref}}(k-1)+K_p*(\mathrm{\Δu}\left(k\right)-\mathrm{\Δu}(k-1))+\mathrm{\Δu}\left(k\right)*\frac{T_c}{K_i}\end{array}\right.---\left(\mathrm{vi}\right);$

Wherein, K _pand K _ibe respectively proportionality coefficient and the integral coefficient of pi regulator; T _cfor the sampling period;

I _refwith filter inductance current i _ldifference, be multiplied by L/T _c, add u _c, be finally multiplied by d/U _dc, just obtain modulation wave signal D, the discrete formula of the modulation wave signal D that track with zero error exports is as follows:

$D\left(k\right)=\frac{d}{U_{\mathrm{dc}}}[u_c\left(k\right)+\frac{L}{T_c}(i_{\mathrm{ref}}\left(k\right)-i_L\left(k\right))]---\left(\mathrm{vii}\right);$

In formula, d is the index of modulation, and L is filter inductance value, T _cfor the sampling period, i _reffor exporting inner ring current reference value, D (k) is the calculated value of the modulation wave signal D of a kth sampling instant, u _ck () is the u of a kth sampling instant _csampled value, i _refk () is the i of a kth sampling instant _refsampled value, i _lk () is the i of a kth sampling instant _lsampled value.

8. a kind of micro-capacitance sensor multi-inverter parallel control method based on the virtual complex impedance of frequency division according to claim 7, it is characterized in that, described step 7) in modulation wave signal D specific formula for calculation (VII) in, the span of d is 0.95 ~ 1.0.