CN104184353A - Inverter parallel connection based circulating current suppression method - Google Patents

Abstract

The invention discloses an inverter parallel connection based circulating current suppression method, which comprises the stages of measuring three-phase output current of an inverter 1 by a detection current sensor, and establishing a mathematical model of a duty ratio state space equation under a three-phase static coordinate system; synchronously rotating the duty ratio state space equation under the coordinate system; acquiring a duty ratio state space equation under a synchronous rotating coordinate system by the duty ratio state space equation under the three-phase static coordinate system; acquiring a zero-axis component of a three-phase bridge arm duty ratio in the inverter 1 and an inverter 2, and acquiring zero-axis current signals; sending the acquired zero-axis current signals to a circulating current controller to act as feedback signals, acting as output of an inverter parallel connection circulator after being processed, and compensating the output to the three-phase bridge arm duty ratio. The inverter parallel connection based circulating current suppression method has the beneficial effects of simple circuit structure, low power consumption, good circulating current suppression effect, capable of meeting requirements of various occasions without additionally arranging hardware, and particularly applicable to a three-phase PWM converter system which is directly connected in parallel at an alternating current side of a public direct current bus.

Description

A kind of inhibition method based on inverter parallel circulation

Technical field

The present invention relates to a kind of inhibition method of inverter parallel circulation; Particularly relate to the directly circulation inhibition method of Three-Phase PWM Converter system in parallel of common DC bus AC.

Background technology

It is adjustable that three-phase voltage type pwm converter has power factor, low harmonic wave, and the advantages such as high efficiency, thereby be widely used in various occasions.And along with the increase of capacity, being subject to Modern Power Electronic Devices holds quantitative limitation, the capacity of separate unit voltage-fed PWM converter is difficult to meet the requirement of present capacity again.In order to break through this restriction, parallel technology becomes study hotspot gradually in large-power occasions.In the direct Three-Phase PWM Converter in parallel of common DC bus AC, can produce the circulation channel of zero-sequence current.In prior art, suppressing the most basic method of circulation is to utilize hardware blocking-up circulation channel, comprise that each current transformer adopts independently DC power supply, AC adopts multi winding transformer to realize electrical isolation etc., and this method can be eliminated circulation completely, but can increase cost and the volume of system.

Summary of the invention

Technical problem to be solved by this invention is that a kind of inhibition method based on inverter parallel circulation is provided.

The technical solution adopted in the present invention is that a kind of inhibition method based on inverter parallel circulation, comprises the following steps;

The three-phase output current of step 1, detection current sensor measurement inverter 1;

Step 2, set up the Mathematical Modeling of duty ratio state space equation under three phase static coordinate system;

Duty ratio state space equation under step 3, synchronous rotating frame;

Step 4, by duty ratio state space equation under three phase static coordinate system, obtain the duty ratio state space equation under synchronous rotating frame;

Step 5, further draw and the zero-axis component of the three-phase brachium pontis duty ratio in inverter 1 and inverter 2 obtain zero-axis current signal;

Step 6, will in step 5, obtain zero-axis current signal, send into after circulation controller as feedback signal, be given as 0, after PI integral controller, compensate to respectively in three-phase brachium pontis duty ratio as the output of inverter parallel circulator.

Sky in described step 2 than state space equation is,

$\frac{d}{\mathrm{dt}}\left[\begin{array}{c}{i}_{a1}\\ i_{b1}\\ i_{c1}\end{array}\right]=-\frac{1}{L_1}(\left[\begin{array}{c}{i}_{a1}\\ i_{b1}\\ i_{c1}\end{array}\right]\left[\begin{array}{ccc}{R}_1& 0& 0\\ 0& R_1& 0\\ 0& 0& R_1\end{array}\right]-\frac{1}{L_1}\left[\begin{array}{c}{e}_a-d_{a1}{U}_{\mathrm{dc}}-U_{N{O}_1}\\ e_b-d_{b1}{U}_{\mathrm{dc}}-{U_{\mathrm{NO}}}_1\\ e_c-d_{c1}{U}_{\mathrm{dc}}-{U_{\mathrm{NO}}}_1\end{array}\right])$

Duty ratio state space equation under synchronous rotating frame in described step 3, by the Mathematical Modeling in step 2 by three phase static coordinate system transformation under two cordic phase rotators, through three-dimensional coordinate transformation, i.e. abc/dqz conversion, transformation matrix is shown below:

$T=\frac{2}{3}\left[\begin{array}{ccc}\cos \left(\mathrm{\ωt}\right)& \cos (\mathrm{\ωt}-\frac{2\mathrm{\π}}{3})& \cos (\mathrm{\ωt}+\frac{2\mathrm{\π}}{3})\\ -\sin \left(\mathrm{\ωt}\right)& -\sin (\mathrm{\ωt}-\frac{2\mathrm{\π}}{3})& -\sin (\mathrm{\ωt}+\frac{2\mathrm{\π}}{3})\\ \sqrt{\frac{1}{2}}& \sqrt{\frac{1}{2}}& \sqrt{\frac{1}{2}}\end{array}\right].$

Duty ratio state space equation under synchronous rotating frame described in step 4 is,

$\begin{array}{c}\frac{d}{\mathrm{dt}}\left[\begin{array}{c}{i}_{d1}\\ i_{q1}\\ i_{z1}\end{array}\right]=-\frac{R_1}{L_1}\left[\begin{array}{c}{i}_{d1}\\ i_{q1}\\ i_{z1}\end{array}\right]-\left[\begin{array}{ccc}0& -\mathrm{\ω}& 0\\ \mathrm{\ω}& 0& 0\\ 0& 0& 0\end{array}\right]\left[\begin{array}{c}{i}_{d1}\\ i_{q1}\\ i_{z1}\end{array}\right]\\ -\frac{1}{L_1}\left[\begin{array}{c}-e_{d1}+d_{d1}{U}_{\mathrm{dc}}\\ -e_{q1}+d_{q1}{U}_{\mathrm{dc}}\\ -e_{z1}+d_{z1}{U}_{\mathrm{dc}}+3U_{N{O}_1}\end{array}\right]\end{array}$

$\begin{array}{c}\frac{d}{\mathrm{dt}}\left[\begin{array}{c}{i}_{d2}\\ i_{q2}\\ i_{z2}\end{array}\right]=-\frac{R_2}{L_2}\left[\begin{array}{c}{i}_{d2}\\ i_{q2}\\ i_{z2}\end{array}\right]-\left[\begin{array}{ccc}0& -\mathrm{\ω}& 0\\ \mathrm{\ω}& 0& 0\\ 0& 0& 0\end{array}\right]\left[\begin{array}{c}{i}_{d2}\\ i_{q2}\\ i_{z2}\end{array}\right]\\ -\frac{1}{L_2}\left[\begin{array}{c}-e_{d1}+d_{d2}{U}_{\mathrm{dc}}\\ -e_{q1}+d_{q2}+U_{\mathrm{dc}}\\ -e_{z1}+d_{z2}{U}_{\mathrm{dc}}+3{U_{\mathrm{NO}}}_1\end{array}\right]\\ \frac{{\mathrm{di}}_{z1}}{\mathrm{dt}}=-\frac{R_1+R_2}{L_1+L_2}{i}_{z1}+\frac{d_{z1}-d_{z2}}{L_1+L_2}{U}_{\mathrm{dc}}\end{array}$

D in formula _z1, d _z2be respectively the zero-axis component of the three-phase brachium pontis duty ratio in inverter 1 and inverter 2; That is:

d _z1＝d _a1+d _b1+d _c1

d _z2＝d _a2+d _b2+d _c2。

The invention has the beneficial effects as follows, this scheme has the outstanding advantages such as circuit topological structure is simple, energy consumption is little, the total capacity of inverter can meet under the requirement of various occasions not needs increases extra hardware, the advantages such as circulation inhibition is good, are particularly useful for the directly Three-Phase PWM Converter system of parallel connection of common DC bus AC.

Brief description of the drawings

Fig. 1 is the flow chart that the present invention is based on the inhibition method of inverter parallel circulation;

Fig. 2 is the topology diagram that the present invention is based on the inverter parallel of the inhibition method of inverter parallel circulation;

Fig. 3 is the circulation controller schematic diagram that the present invention is based on the inhibition method of inverter parallel circulation;

Fig. 4 is that the inhibition method that the present invention is based on inverter parallel circulation adds inverter 1 and inverter 2 phase current waveform comparison diagrams after circulation controller.

Embodiment

Below in conjunction with the drawings and specific embodiments, the present invention is described in further detail:

Fig. 1 is the flow chart that the present invention is based on the inhibition method of inverter parallel circulation; Fig. 2 is the topology diagram that the present invention is based on the inverter parallel of the inhibition method of inverter parallel circulation; Fig. 3 is the circulation controller schematic diagram that the present invention is based on the inhibition method of inverter parallel circulation; As shown in Figure 1 to Figure 3, the present invention is based on the inhibition method of inverter parallel circulation, comprise the following steps; The three-phase output current of step 1, detection current sensor measurement inverter 1; Step 2, set up the Mathematical Modeling of duty ratio state space equation under three phase static coordinate system; Duty ratio state space equation under step 3, synchronous rotating frame; Step 4, by duty ratio state space equation under three phase static coordinate system, obtain the duty ratio state space equation under synchronous rotating frame; Step 5, further draw and the zero-axis component of the three-phase brachium pontis duty ratio in inverter 1 and inverter 2 obtain zero-axis current signal; Step 6, will in step 5, obtain zero-axis current signal, send into after circulation controller as feedback signal, be given as 0, after PI integral controller, compensate to respectively in three-phase brachium pontis duty ratio as the output of inverter parallel circulator.

1. zero-sequence current produces reason

1) duty ratio state space equation under three phase static coordinate system:

As shown in Figure 2, can obtain the state space equation that duty ratio represents by kirchhoff electric current and voltage law:

$\frac{d}{\mathrm{dt}}\left[\begin{array}{c}{i}_{a1}\\ i_{b1}\\ i_{c1}\end{array}\right]=-\frac{1}{L_1}(\left[\begin{array}{c}{i}_{a1}\\ i_{b1}\\ i_{c1}\end{array}\right]\left[\begin{array}{ccc}{R}_1& 0& 0\\ 0& R_1& 0\\ 0& 0& R_1\end{array}\right]-\frac{1}{L_1}\left[\begin{array}{c}{e}_a-d_{a1}{U}_{\mathrm{dc}}-U_{N{O}_1}\\ e_b-d_{b1}{U}_{\mathrm{dc}}-{U_{\mathrm{NO}}}_1\\ e_c-d_{c1}{U}_{\mathrm{dc}}-{U_{\mathrm{NO}}}_1\end{array}\right])$

Wherein:

L ₁, L ₂be respectively inverter 1, inverter 2 three pole reactors;

R ₁, R ₂be respectively inverter 1, inverter 2 three pole reactors at interior line resistance;

I _a1, i _b1,i _c1represent inverter 1 three-phase alternating current side output current;

I _a2, i _b2, i _c2represent inverter 2 three-phase alternating current side output currents;

D _a1, d _b1, d _c1represent the every phase brachium pontis of inverter duty ratio;

D _a2, d _b2, d _c2represent the every phase brachium pontis of inverter 2 duty ratio.

DU _dcrepresent the mid-point voltage of every phase brachium pontis;

U _dcrepresent DC bus-bar voltage;

E _a,e _b, e _crepresent three phase network voltage;

I _z1=i _a1+ i _b1+ i _c1represent inverter 1 zero-sequence current;

I _z2=i _a2+ i _b2+ i _c2represent inverter 2 zero-sequence currents.

2) duty ratio state space equation under synchronous rotating frame

By model by three phase static coordinate system transformation under two cordic phase rotators, need to take three-dimensional coordinate transformation here, i.e. abc/dqz conversion, transformation matrix is shown below:

$T=\frac{2}{3}\left[\begin{array}{ccc}\cos \left(\mathrm{\ωt}\right)& \cos (\mathrm{\ωt}-\frac{2\mathrm{\π}}{3})& \cos (\mathrm{\ωt}+\frac{2\mathrm{\π}}{3})\\ -\sin \left(\mathrm{\ωt}\right)& -\sin (\mathrm{\ωt}-\frac{2\mathrm{\π}}{3})& -\sin (\mathrm{\ωt}+\frac{2\mathrm{\π}}{3})\\ \sqrt{\frac{1}{2}}& \sqrt{\frac{1}{2}}& \sqrt{\frac{1}{2}}\end{array}\right]$

In formula, ω is synchronous angular velocity.

By duty ratio state space equation under three phase static coordinate system, can obtain the duty ratio state space equation under synchronous rotating frame:

$\begin{array}{c}\frac{d}{\mathrm{dt}}\left[\begin{array}{c}{i}_{d1}\\ i_{q1}\\ i_{z1}\end{array}\right]=-\frac{R_1}{L_1}\left[\begin{array}{c}{i}_{d1}\\ i_{q1}\\ i_{z1}\end{array}\right]-\left[\begin{array}{ccc}0& -\mathrm{\ω}& 0\\ \mathrm{\ω}& 0& 0\\ 0& 0& 0\end{array}\right]\left[\begin{array}{c}{i}_{d1}\\ i_{q1}\\ i_{z1}\end{array}\right]\\ -\frac{1}{L_1}\left[\begin{array}{c}-e_{d1}+d_{d1}{U}_{\mathrm{dc}}\\ -e_{q1}+d_{q1}{U}_{\mathrm{dc}}\\ -e_{z1}+d_{z1}{U}_{\mathrm{dc}}+3U_{N{O}_1}\end{array}\right]\end{array}$

$\begin{array}{c}\frac{d}{\mathrm{dt}}\left[\begin{array}{c}{i}_{d2}\\ i_{q2}\\ i_{z2}\end{array}\right]=-\frac{R_2}{L_2}\left[\begin{array}{c}{i}_{d2}\\ i_{q2}\\ i_{z2}\end{array}\right]-\left[\begin{array}{ccc}0& -\mathrm{\ω}& 0\\ \mathrm{\ω}& 0& 0\\ 0& 0& 0\end{array}\right]\left[\begin{array}{c}{i}_{d2}\\ i_{q2}\\ i_{z2}\end{array}\right]\\ -\frac{1}{L_2}\left[\begin{array}{c}-e_{d1}+d_{d2}{U}_{\mathrm{dc}}\\ -e_{q1}+d_{q2}+U_{\mathrm{dc}}\\ -e_{z1}+d_{z2}{U}_{\mathrm{dc}}+3{U_{\mathrm{NO}}}_1\end{array}\right]\\ \frac{{\mathrm{di}}_{z1}}{\mathrm{dt}}=-\frac{R_1+R_2}{L_1+L_2}{i}_{z1}+\frac{d_{z1}-d_{z2}}{L_1+L_2}{U}_{\mathrm{dc}}\end{array}$ ①

D in formula _z1, d _z2be respectively the zero-axis component of inverter 1, inverter 2 three-phase brachium pontis duty ratios; That is:

d _z1＝d _a1+d _b1+d _c1

d _z2＝d _a2+d _b2+d _c2

1. the rate of change that can be found out zero-sequence current by formula causes by the zero sequence duty ratio zero-axis component of two inverters is inconsistent.

2. circulation PI controller

Due to i _z=i _z1=-i _z2as long as suppress the circulation of one of them inverter, the circulation of another inverter is inhibited naturally.First the three-phase output current of current sensor measurement inverter 1, can obtain zero-axis current signal by abc/dqz transformation matrix, send into after circulation controller as feedback signal, be given as 0, after pi regulator, compensate to respectively three-phase brachium pontis duty ratio d as the output of circulation controller _a1, d _b1, d _c1upper, thus d adjusted _z1,reach the object that circulation suppresses.Fig. 4 is that the inhibition method that the present invention is based on inverter parallel circulation adds inverter 1 and inverter 2 phase current waveform comparison diagrams after circulation controller; As shown in Figure 4, add circulation controller after inverter 1 very close with inverter 2 phase current waveform.

The present invention has the outstanding advantages such as circuit topological structure is simple, energy consumption is little, the total capacity of inverter can meet under the requirement of various occasions not needs increases extra hardware, the advantages such as circulation inhibition is good, are particularly useful for the directly Three-Phase PWM Converter system of parallel connection of common DC bus AC.

Above the technical program embodiment is had been described in detail, but described content is only the preferred embodiment of the technical program, can not be considered to the practical range for limiting the technical program.All equalization variation and improvement etc. of doing according to the technical program application range, within all should still belonging to the patent covering scope of the technical program.

Claims (4)

1. the inhibition method based on inverter parallel circulation, is characterized in that, comprises the following steps;

The three-phase output current of step 1, detection current sensor measurement inverter 1;

Step 2, set up the Mathematical Modeling of duty ratio state space equation under three phase static coordinate system;

Duty ratio state space equation under step 3, synchronous rotating frame;

Step 4, by duty ratio state space equation under three phase static coordinate system, obtain the duty ratio state space equation under synchronous rotating frame;

Step 5, further draw and the zero-axis component of the three-phase brachium pontis duty ratio in inverter 1 and inverter 2 obtain zero-axis current signal;

Step 6, will in step 5, obtain zero-axis current signal, send into after circulation controller as feedback signal, be given as 0, after PI integral controller, compensate to respectively in three-phase brachium pontis duty ratio as the output of inverter parallel circulator.

2. the inhibition method based on inverter parallel circulation according to claim 1, is characterized in that, the sky in described step 2 than state space equation is,

$\frac{d}{\mathrm{dt}}\left[\begin{array}{c}{i}_{a1}\\ i_{b1}\\ i_{c1}\end{array}\right]=-\frac{1}{L_1}(\left[\begin{array}{c}{i}_{a1}\\ i_{b1}\\ i_{c1}\end{array}\right]\left[\begin{array}{ccc}{R}_1& 0& 0\\ 0& R_1& 0\\ 0& 0& R_1\end{array}\right]-\frac{1}{L_1}\left[\begin{array}{c}{e}_a-d_{a1}{U}_{\mathrm{dc}}-U_{N{O}_1}\\ e_b-d_{b1}{U}_{\mathrm{dc}}-{U_{\mathrm{NO}}}_1\\ e_c-d_{c1}{U}_{\mathrm{dc}}-{U_{\mathrm{NO}}}_1\end{array}\right])$

3. the inhibition method based on inverter parallel circulation according to claim 1, it is characterized in that, duty ratio state space equation under synchronous rotating frame in described step 3, by the Mathematical Modeling in step 2 by three phase static coordinate system transformation under two cordic phase rotators, through three-dimensional coordinate transformation, be abc/dqz conversion, transformation matrix is shown below:

$T=\frac{2}{3}\left[\begin{array}{ccc}\cos \left(\mathrm{\ωt}\right)& \cos (\mathrm{\ωt}-\frac{2\mathrm{\π}}{3})& \cos (\mathrm{\ωt}+\frac{2\mathrm{\π}}{3})\\ -\sin \left(\mathrm{\ωt}\right)& -\sin (\mathrm{\ωt}-\frac{2\mathrm{\π}}{3})& -\sin (\mathrm{\ωt}+\frac{2\mathrm{\π}}{3})\\ \sqrt{\frac{1}{2}}& \sqrt{\frac{1}{2}}& \sqrt{\frac{1}{2}}\end{array}\right].$

4. the inhibition method based on inverter parallel circulation according to claim 1, is characterized in that, the duty ratio state space equation under the synchronous rotating frame described in step 4 is,

$\begin{array}{c}\frac{d}{\mathrm{dt}}\left[\begin{array}{c}{i}_{d1}\\ i_{q1}\\ i_{z1}\end{array}\right]=-\frac{R_1}{L_1}\left[\begin{array}{c}{i}_{d1}\\ i_{q1}\\ i_{z1}\end{array}\right]-\left[\begin{array}{ccc}0& -\mathrm{\ω}& 0\\ \mathrm{\ω}& 0& 0\\ 0& 0& 0\end{array}\right]\left[\begin{array}{c}{i}_{d1}\\ i_{q1}\\ i_{z1}\end{array}\right]\\ -\frac{1}{L_1}\left[\begin{array}{c}-e_{d1}+d_{d1}{U}_{\mathrm{dc}}\\ -e_{q1}+d_{q1}{U}_{\mathrm{dc}}\\ -e_{z1}+d_{z1}{U}_{\mathrm{dc}}+3U_{N{O}_1}\end{array}\right]\end{array}$

$\begin{array}{c}\frac{d}{\mathrm{dt}}\left[\begin{array}{c}{i}_{d2}\\ i_{q2}\\ i_{z2}\end{array}\right]=-\frac{R_2}{L_2}\left[\begin{array}{c}{i}_{d2}\\ i_{q2}\\ i_{z2}\end{array}\right]-\left[\begin{array}{ccc}0& -\mathrm{\ω}& 0\\ \mathrm{\ω}& 0& 0\\ 0& 0& 0\end{array}\right]\left[\begin{array}{c}{i}_{d2}\\ i_{q2}\\ i_{z2}\end{array}\right]\\ -\frac{1}{L_2}\left[\begin{array}{c}-e_{d1}+d_{d2}{U}_{\mathrm{dc}}\\ -e_{q1}+d_{q2}+U_{\mathrm{dc}}\\ -e_{z1}+d_{z2}{U}_{\mathrm{dc}}+3{U_{\mathrm{NO}}}_1\end{array}\right]\\ \frac{{\mathrm{di}}_{z1}}{\mathrm{dt}}=-\frac{R_1+R_2}{L_1+L_2}{i}_{z1}+\frac{d_{z1}-d_{z2}}{L_1+L_2}{U}_{\mathrm{dc}}\end{array}$

D in formula _z1, d _z2be respectively the zero-axis component of the three-phase brachium pontis duty ratio in inverter 1 and inverter 2; That is:

d _z1＝d _a1+d _b1+d _c1

d _z2＝d _a2+d _b2+d _c2。