A three-phase voltage source inverter

Abstract

The application discloses a three-phase voltage source inverter, which comprises: inverter A, B and C three-phase upper and lower working bridge arms V a1 、 b1 、 c1 、 a2 、 b2 、 c2 , corresponding anti-association diodes VD a1 、 b1 、 c1 、 a2 、 b2 、 c2 , upper and lower bridge arm shunt switch devices S1 and S2, three-phase selective switch devices T a1 、 b1 、 c1 、 a2 、 b2 、 c2 in additional dynamic shunt branches; when the inverter AC side three-phase current has a phase with a maximum positive current, the T a2 、 b2 、 c2 corresponding to the additional dynamic shunt branch are turned on, and the S1 of the additional dynamic shunt branch is shunted in parallel to the phase with the maximum positive current; when a phase with a maximum reverse current exists, the T a1 、 b1 、 c1 corresponding to the additional dynamic shunt branch are turned on, and the S1 of the additional dynamic shunt branch is shunted in parallel to the phase with the maximum reverse current. The application reduces the overcurrent of the inverter working bridge arm switch device caused by AC system disturbance, and improves the operation reliability of the inverter.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power electronics, in particular to a three-phase voltage source inverter. BACKGROUND

[0002] With the continuous growth of wind power and photovoltaic grid-connected capacity, the number of energy storage devices and flexible DC transmission projects is increasing. Inverters have been widely used in power systems, and the development trend of power electronics in the system is increasingly prominent. Restricted by the low overcurrent tolerance of power electronic devices, after the disturbance of the grid-connected AC system, the inverter has the risk of switching device damage due to overcurrent, which leads to the inverter exiting operation. In the presence of wind power, photovoltaic, energy storage and other large number of grid-connected inverters, the overcurrent of the inverter due to AC system disturbance will cause the inverter to fail or be disconnected from the grid, which will bring a large amount of active and reactive power impact to the system, and further threaten the system power angle stability, voltage stability and frequency stability. Therefore, it is urgent to study the measures to improve the overcurrent tolerance of the inverter.

[0003] Existing related researches mainly focus on the control strategy of the inverter, and researches on reducing the current of the inverter under AC system disturbance, including virtual impedance control, etc. However, this control method will increase the electrical distance between the inverter and the AC system, which is not conducive to the inverter providing dynamic reactive power support for the AC grid. SUMMARY

[0004] To solve the above problems, the present application provides a three-phase voltage source inverter, which comprises: inverter A, B, C three-phase upper and lower working bridge arms V a1 , V b1 , V c1 and V a2 , V b2 , V c2 , the anti-associated diodes corresponding to the inverter A, B, C three-phase upper and lower working bridge arms are VD a1 , VD b1 , VD c1 and VD a2 , VD b2 , VD c2 , the inverter A, B, C three-phase upper and lower bridge arms are divided into S1, which are the phase selection switching devices T a1 , T b1 , T c1 and T a2 , T b2 , T c2 in the additional dynamic shunt branch.

[0005] When the three-phase current i a , i b , i cWhen a phase has the maximum positive current, the phase selection switch T corresponding to the additional dynamic shunt branch is activated. a2 T b2 T c2 The upper arm switching device S1 of the additional dynamic shunt branch performs parallel shunt on the phase with the maximum positive current.

[0006] When the three-phase current i on the AC side of the inverter a i b i c When a phase has the maximum reverse current, the phase selection switch T corresponding to the additional dynamic shunt branch is activated. a1 T b1 T c1 The lower bridge arm switching device S1 of the additional dynamic shunt branch performs parallel shunt on the phase with the maximum reverse current.

[0007] Preferably, the upper and lower working arms V of the three phases A, B, and C of the inverter a1 V b1 V c1 and V a2 V b2 V c2 It is the body of the Insulated Gate Bipolar Transistor (IGBT).

[0008] Preferably, the shunt switching device S1 of the upper and lower bridge arms of the inverter A, B, and C phases is an insulated gate bipolar transistor (IGBT).

[0009] Preferably, the phase selection switching device T for phases A, B, and C of the inverter is... a1 T b1 T c1 and T a2 T b2 T c2 , is a gate turn-off thyristor GTO.

[0010] Preferably, it further includes: dividing the current flow of the additional dynamic shunt branch and the inverter working bridge arm into 6 working regions, wherein,

[0011] The first work area, in which i a >0 and i a >i b i a >i c V a1 On, corresponding to S1 and T a2 It is connected and acts as an additional dynamic shunt branch, connected to the working bridge arm V of phase A. a1 Share 50% of i a ;

[0012] Second working region, in which i c <0 and |i c >|i a |, |i c >|i b |, V c2 is on, corresponding to S1 and T c1 is on and acts as an additional dynamic shunt branch, with C the lower working bridge arm V c2 sharing 50% of i c ;

[0013] Third working region, in which i b >0 and i b >i a , i b >i c , V b1 is on, corresponding to S1 and T b2 is on and acts as an additional dynamic shunt branch, with B the upper working bridge arm V b1 sharing 50% of i b ;

[0014] Fourth working region, in which i a <0 and |i a |>|i b |, |i a |>|i c |, V a2 is on, corresponding to S1 and T a1 is on and acts as an additional dynamic shunt branch, with A the lower working bridge arm V a2 sharing 50% of i a ;

[0015] Fifth working region, in which i c >0 and i c >i a , i c >i b , V c1 is on, corresponding to S1 and T c2 is on and acts as an additional dynamic shunt branch, with C the upper working bridge arm V c1 sharing 50% of i c ;

[0016] Sixth working region, in which i b <0 and |i b |>|i a |, |i b |>|i c |, V b2 is on, corresponding to S1 and T b1Conducting and as an additional dynamic shunt branch, with B phase upper work bridge arm V b2 Commonly share 50% of i b . BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a schematic diagram of a topology of a three-phase voltage source inverter provided by the present application;

[0018] Figure 2 is a schematic diagram of a three-phase voltage source inverter AC side current operating interval division involved by the present application;

[0019] Figure 3 is a schematic diagram of a three-phase voltage source inverter current dynamic shunt involved by the present application;

[0020] Figure 4 is a schematic diagram of a test system involved by the present application;

[0021] Figure 5 is a schematic diagram of a three-phase voltage source inverter current waveform diagram of each branch before and after applying AC voltage disturbance involved by the present application;

[0022] Figure 6 is a schematic diagram of a three-phase voltage source inverter current under AC system voltage disturbance involved by the present application. DETAILED DESCRIPTION

[0023] In the following description, a lot of specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be practiced in many different ways beyond the specific details disclosed herein, and similar modifications and / or adjustments can be made by those skilled in the art without departing from the spirit and scope of the present application, so the present application is not limited to the specific implementation disclosed below.

[0024] Figure 1 is a schematic diagram of a topology of a three-phase voltage source inverter provided by the present application, as Figure 1 shown, a three-phase voltage source inverter provided by the present application includes: inverter A, B, C three-phase upper and lower work bridge arm V a1 , V b1 , V c1 and V a2 , V b2 , V c2 , the corresponding anti-association diode of inverter A, B, C three-phase upper and lower work bridge arm is VD a1 , VD b1 , VD c1 and VD a2 , VD b2 , VD c2 , the shunt switching device S1 of inverter A, B, C three-phase upper and lower bridge arm, as an additional dynamic shunt branch, the phase selection switching device T of inverter A, B, C three-phasea1 , T b1 , T c1 and T a2 , T b2 , T c2 ;

[0025] When the phase with the maximum positive current among the three-phase currents i a , i b , i c of the AC side of the inverter appears, the phase selection switch device T a2 , T b2 , T c2 of the additional dynamic shunt branch is turned on, and the upper bridge arm switch device S1 of the additional dynamic shunt branch shunts the phase with the maximum positive current in parallel.

[0026] When the phase with the maximum negative current among the three-phase currents i a , i b , i c of the AC side of the inverter appears, the phase selection switch device T a1 , T b1 , T c1 of the additional dynamic shunt branch is turned on, and the lower bridge arm switch device S1 of the additional dynamic shunt branch shunts the phase with the maximum negative current in parallel.

[0027] The upper and lower working bridge arms V a1 , V b1 , V c1 and V a2 , V b2 , V c2 of the three-phase inverter A, B and C are insulated gate bipolar transistors (IGBT). The shunt switch devices S1 of the upper and lower bridge arms of the three-phase inverter A, B and C are IGBTs. The phase selection switch devices T a1 , T b1 , T c1 and T a2 , T b2 , T c2 of the three-phase inverter A, B and C are gate turn-off thyristors (GTO).

[0028] Figure 1 U dc in the above formula is the DC side voltage. i a , i b , i c are the three-phase currents of the AC side of the inverter, and the positive direction of the current is shown in the following formula. Figure 1

[0029] Specifically, the present application is implemented by the following technical scheme. According to i a , i​b , i c The phase with the maximum positive current in i a2 , T b2 , T c2 The phase is shunted in parallel by the switching device S1 of the additional dynamic shunt branch, so as to reduce the current flowing through the corresponding phase V a1 , V b1 , or V c1 in the upper working bridge arm of the inverter; the phase with the maximum negative current in i a , i b , i c The phase is shunted in parallel by the switching device S1 of the additional dynamic shunt branch, so as to reduce the current flowing through the corresponding phase V a1 , T b1 , T c1 The phase is shunted in parallel by the switching device S1 of the additional dynamic shunt branch, so as to reduce the current flowing through the corresponding phase V a2 , V b2 , or V c2 in the lower working bridge arm of the inverter. Through the shunting effect of the additional dynamic shunt branch, the maximum current flowing through the switching devices V a1 , V b1 , V c1 , and V a2 , V b2 , V c2 of the working bridge arm can be effectively reduced, so as to improve the continuous grid-connected operation capability of the inverter during the AC disturbance process, and avoid the working bridge arm from exiting operation or being damaged due to overcurrent.

[0030] The flow of the additional dynamic shunt branch and the current of the working bridge arm of the inverter is divided into six working regions, as shown in Figure 2 .

[0031] The current shunting working mode of the working bridge arm of the inverter is shown in Figure 3 . As can be seen from the figure, when the switching devices of the three working upper bridge arms or working lower bridge arms are turned on in the corresponding working region, an additional dynamic shunt branch is generated in parallel with the switching device S1 and the corresponding additional dynamic shunt branch selection switch T a1 , T b1 , T c1 , T a2 , T b2 , T c2 , which shares the current flowing through the switching device. It should be noted that, in order to highlight the shunting situation in each working interval, Figure 3 only the on state of the switching device with a shunt path in the working interval is drawn, and the working mode of the remaining switching devices is omitted.

[0032] The following explains in detail the shunt paths of the switching devices in each working area.

[0033] The first work area, the diversion and circulation path is as follows: Figure 3 As shown in (1). In this work area, i a >0 and i a >i b i a >i c V a1 On, corresponding to S1 and T a2 It is connected and acts as an additional dynamic shunt branch, connected to the working bridge arm V of phase A. a1 Share 50% of i a ;

[0034] The second work area has the following distribution path: Figure 3 As shown in (2). In this work area, i c <0 and |i c |>|i a |、|i c |>|i b |,V c2 On, corresponding to S1 and T c1 It is connected and acts as an additional dynamic shunt branch, connected to the working bridge arm V of phase C. c2 Share 50% of i c ;

[0035] The third work area has the following distribution path: Figure 3 As shown in (3), in this working area, i b >0 and i b >i a i b >i c V b1 On, corresponding to S1 and T b2 It is connected and acts as an additional dynamic shunt branch, connected to the working bridge arm V of phase B. b1 Share 50% of i b ;

[0036] The fourth work area has the following distribution path: Figure 3 As shown in (4), in this working area, i a <0 and |i a |>|i b |、|i a |>|i c |,V a2 On, corresponding to S1 and T a1 It is connected and acts as an additional dynamic shunt branch, connected to the working bridge arm V of phase A. a2 Share 50% of i a;

[0037] The fifth work area has the following distribution path: Figure 3 As shown in (5), in this working area, i c >0 and i c >i a i c >i b V c1 On, corresponding to S1 and T c2 It is connected and acts as an additional dynamic shunt branch, connected to the working bridge arm V of phase C. c1 Share 50% of i c ;

[0038] The sixth work area has the following distribution path: Figure 3 As shown in (6), in this working area, i b <0 and |i b |>|i a |、|i b |>|i c |,V b2 On, corresponding to S1 and T b1 It is connected and acts as an additional dynamic shunt branch, connected to the working bridge arm V of phase B. b2 Share 50% of i b .

[0039] Specific application examples are as follows:

[0040] Build such in simulation software Figure 4 The test system is shown, and the following conditions are applied: Figure 5 The AC voltage disturbance shown causes the amplitude of the three phases of the AC voltage to decrease simultaneously from 0.3 pu to 0.2 pu at 0.186 s.

[0041] It can be seen that after the AC voltage drops, the amplitudes of the currents Isa, Isb, and Isc injected by the inverter into the AC system increase significantly, such as Figure 6 As shown in (a), when this current flows through the upper and lower working bridge arm switching devices Va1, Vb1, Vc1 and Va2, Vb2, Vc2 of the inverter, there is a risk of device damage due to excessive current, causing the inverter to malfunction and shut down. At the moment of disturbance (0.186s), an additional dynamic shunt branch is activated, and the upper and lower bridge arm currents in the shunt branch are as follows: Figure 6 As shown in (b) and (c), after current shunting, the current in the switching devices in the working bridge arm can be significantly reduced, such as... Figure 6(b) and (c) Iva1, Ivb1, Ivc1 and Iva2, Ivb2, Ivc2, the maximum current of the upper and lower working bridge arms can be reduced by ΔIp, ΔIn. From the simulation results, it can be seen that the new three-phase voltage source inverter proposed in the patent can significantly reduce the overcurrent of the inverter working bridge arm switch caused by AC system disturbance, and improve the reliability of the inverter operation.

Claims

1. A three-phase voltage source inverter, characterized by comprising: Comprise: Inverter A, B, C three-phase upper and lower working bridge arm V a1 , V b1 , V c1 and V a2 , V b2 , V c2 , the corresponding anti-association diode of inverter A, B, C three-phase upper and lower working bridge arm is VD a1 , VD b1 , VD c1 and VD a2 , VD b2 , VD c2 , the shunt switch device S1 of inverter A, B, C three-phase upper and lower bridge arm, as the selected phase switch device T a1 , T b1 , T c1 and T a2 , T b2 , T c2 , the selected phase switch device of upper and lower bridge arm is T up , T dn ; When the three-phase current i a , b , c of the inverter AC side has a phase with a maximum positive current, the phase selection switch device T a2 , b2 , c2 of the additional dynamic shunt branch is turned on, and S1 is in parallel shunt with the phase with the maximum positive current. When the three-phase current i a , b , c of the inverter AC side has a phase with a maximum reverse current, the phase selection switch device T a1 , b1 , c1 S1 in parallel with the phase with the maximum reverse current is turned on to add a dynamic shunt branch. T up The cathode of T is connected to the collector of S1, T up The anode of T is connected to the positive terminal of the power supply. T dn the anode of T dn is connected to the negative terminal of the power supply; The collector of S1 is connected to the cathode of T a1 , the anode of T b1 , the cathode of T c1 , the emitter of S1 is connected to the anode of T a2 , the cathode of T b2 , the anode of T c2 ​ T a1 anode and T a2 The cathode is connected to serve as the A-phase output; T b1 anode of T b2 cathode of T as phase B output; T c1 anode of T c2 cathode of T as phase C output.

2. The three-phase voltage source inverter according to claim 1, characterized by Inverters A, B, C three-phase upper and lower working bridge arms V a1 , V b1 , V c1 and V a2 , V b2 , V c2 , are insulated gate bipolar transistors IGBT.

3. The three-phase voltage source inverter according to claim 1, characterized by The three-phase upper and lower bridge arm shunt switch devices S1 of the inverter A, B, C are IGBT.

4. The three-phase voltage source inverter according to claim 1, characterized by Phase selection switching devices T of the inverter A, B, C three phases a1 b1 c1 a2 b2 c2 GTO, gate turn-off thyristor​​​​​ 5. The three-phase voltage source inverter according to claim 1, characterized by Also include: The flow of the additional dynamic shunt branch and the working bridge arm current of the inverter is divided into six working areas, wherein, The first working area, in the working area, i a >0 and i a >i b , i a >i c , V a1 conduction, corresponding to S1 and T a2 conduction and as an additional dynamic shunt branch, with A phase upper working bridge arm V a1 share 50% of i a ; The second working area, in which i c <0 and |i c |>|i a |, |i c |>|i b |, V c2 Conducting, corresponding to S1 and T c1 Conducting and as an additional dynamic shunt branch, with C, the lower working bridge arm V c2 Commonly share 50% of i c ; A third operating region, in which i b > 0 and i b > i a , i b > i c , V b1 is on, corresponding to S1 and T b2 is on and as an additional dynamic shunt branch, shares 50% of i b1 with B, the upper operating bridge arm V b ; A fourth operating region, in which operating region i a <0 and |i a |>|i b |, |i a |>|i c |, V a2 is on, corresponding to S1 and T a1 is on and acts as an additional dynamic shunt branch, with A being the lower operating bridge arm V a2 sharing 50% of i a ; The fifth working area, in this working area, i c 0 and i c i a , i c i b , V c1 on, corresponding to S1 and T c2 on and as an additional dynamic shunt branch, with C, the upper working bridge arm V c1 share 50% of i c ; Sixth operating region, in which operating region i b <0 and |i b |>|i a |, |i b |>|i c |, V b2 conduction, corresponding to S1 and T b1 conduction and as an additional dynamic shunt branch, with B, upper operating bridge arm V b2 share 50% of i b .

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