A three-phase two-level voltage source inverter

Abstract

The application discloses a three-phase two-level 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 an additional dynamic shunt branch; when the inverter AC side three-phase current has a phase with a maximum positive current, 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 positive current; when a phase with a maximum reverse current exists, the T a2 、 b2 、 c2 corresponding to the additional dynamic shunt branch are turned on, and the S2 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] This invention relates to the field of power electronics technology, specifically to a three-phase two-level voltage source inverter. Background Technology

[0002] With the continuous growth of grid-connected wind and solar power capacity, the increasing number of energy storage devices and flexible DC transmission projects, inverters have been widely used in power systems, and the trend of power electronics development in these systems is becoming increasingly prominent. However, due to factors such as the low overcurrent withstand capability of power electronic devices, inverters face the risk of overcurrent damage to switching devices and subsequent shutdown after disturbances in the grid-connected AC system. In power systems with a large number of inverters connected to the grid, including wind, solar, and energy storage systems, inverter failures or grid disconnections due to overcurrent caused by AC system disturbances can lead to significant active and reactive power surges, threatening system power angle stability, voltage stability, and frequency stability. Therefore, it is urgent to research measures to improve the overcurrent withstand capability of inverters.

[0003] Existing research mainly focuses on inverter control strategies, studying how to reduce inverter current under AC system disturbances, including virtual impedance control. 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 to the AC grid. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a three-phase two-level voltage source inverter, comprising: upper and lower working bridge arms V of inverters A, B, and C. a1 V b1 V c1 and V a2 V b2 V c2 The anti-correlation diodes corresponding to the upper and lower working arms of the three phases A, B, and C of the inverter are VD, ... a1 VD b1 VD c1 and VD a2 VD b2 VD c2 The shunt switching devices S1 and S2 of the upper and lower bridge arms of the inverter A, B, and C phases serve as the phase selection switching devices T of the inverter A, B, and C phases in the additional dynamic shunt branch. a1 T b1 T c1 and T a2 T b2 T c2 ;

[0005] When the three-phase current i on the AC side of the inverter 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. a1 T b1 T c1 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. a2 T b2 T c2 The lower bridge arm switching device S2 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 devices S1 and S2 of the upper and lower bridge arms of the inverter A, B, and C phases are insulated gate bipolar transistors (IGBTs).

[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 a1 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 Meanwhile, i b <0 and i ba i b c V b2 On, corresponding to S2 and T b2 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 ;

[0012] The second work area, in which i a >0 and i a >i b i a >i c V a1 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. a1 Share 50% of i a Meanwhile, i c <0 and i c a i c b V c2 On, corresponding to S2 and T c2 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 ;

[0013] The third work area, in which i b >0 and i b >i a i b >i c V b1 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. b1 Share 50% of i b Meanwhile, i c <0 and i c a i c b V c2 On, corresponding to S2 and T c2 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 ;

[0014] The fourth work area, in which i b >0 and i b >i a ​​​​​​i b >i c V b1 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. b1 Share 50% of i b Meanwhile, i a <0 and i a b i a c V a2 On, corresponding to S2 and T a2 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 ;

[0015] The fifth work area, in which i c >0 and i c >i a i c >i b V c1 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. c1 Share 50% of i c Meanwhile, i a <0 and i a b i a c V a2 On, corresponding to S2 and T a2 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 ;

[0016] The sixth work area, in which i c >0 and i c >i a i c >i b V c1 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. c1 Share 50% of i c Meanwhile, i b <0 and i b a i b c V b2 ​​​​​​On, corresponding to S2 and T b2 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 . Attached Figure Description

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

[0018] Figure 2 This invention relates to a schematic diagram of the AC side current operating range division of a three-phase two-level voltage source inverter;

[0019] Figure 3 This invention relates to a schematic diagram of current shunt in a three-phase two-level voltage source inverter;

[0020] Figure 4 This is a schematic diagram of the testing system involved in the present invention;

[0021] Figure 5 This invention relates to inverter current under AC system voltage disturbances. Detailed Implementation

[0022] Numerous specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0023] Figure 1 This is a schematic diagram of the topology of a three-phase two-level voltage source inverter provided by the present invention, as shown below. Figure 1 As shown, the present invention provides a three-phase two-level voltage source inverter comprising: inverter A, B, and C three-phase upper and lower working bridge arms V a1 V b1 V c1 and V a2 V b2 V c2 The anti-correlation diodes corresponding to the upper and lower working arms of the three phases A, B, and C of the inverter are VD, ... a1 VD b1 VD c1 and VD a2 VD b2 VD c2 The shunt switching devices S1 and S2 of the upper and lower bridge arms of the inverter A, B, and C phases serve as the phase selection switching devices T of the inverter A, B, and C phases in the additional dynamic shunt branch. a1 T b1 Tc1 and T a2 T b2 T c2 ;

[0024] When the three-phase current i on the AC side of the inverter a i b i c When a phase has the maximum positive current, the phase selection switch T corresponding to the additional dynamic shunt branch is activated. a1 T b1 T c1 The upper arm switching device S1 of the additional dynamic shunt branch performs parallel shunt on the phase with the maximum positive current.

[0025] 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. a2 T b2 T c2 The lower bridge arm switching device S2 of the additional dynamic shunt branch performs parallel shunt on the phase with the maximum reverse current.

[0026] 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 inverter's three-phase (A, B, C) upper and lower bridge arm shunt switching devices S1 and S2 are insulated-gate bipolar transistors (IGBTs). The inverter's three-phase (A, B, C) phase selection switching device T... a1 T b1 T c1 and T a2 T b2 T c2 , is a gate turn-off thyristor GTO.

[0027] Figure 1 U in dc This is the DC side voltage. a i b i c The three-phase current on the AC side of the inverter is defined, and the positive direction of the current is specified as follows: Figure 1 As shown.

[0028] Specifically, this invention is accomplished through the following technical solution. Based on i a i b i cThe phase with the maximum positive current corresponds to the phase selection switch T that activates the additional shunt branch. a1 T b1 T c1 The upper arm switching device S1 of the additional dynamic shunt branch performs parallel shunt on this phase to reduce the V of the corresponding phase in the working arm of the inverter. a1 V b1 or V c1 The current flowing through it; according to i a i b i c The phase with the maximum reverse current corresponds to the phase selection switch T that activates the additional shunt branch. a2 T b2 T c2 The lower arm switching device S2 of the additional dynamic shunt branch performs parallel shunt on this phase to reduce the corresponding phase V in the lower working arm of the inverter. a2 V b2 or V c2 The current flowing through it. After being shunt by the additional dynamic shunt branch, the current flowing through the switching devices V of the working bridge arm can be effectively reduced. a1 V b1 V c1 and V a2 V b2 V c2 The maximum current is reduced, thereby improving the inverter's ability to continuously operate in grid connection during AC disturbances and preventing it from being taken out of service or damaged due to overcurrent in the working bridge arm.

[0029] The current flow in the additional dynamic shunt branch and the inverter working bridge arm is divided into 6 working regions, such as... Figure 2 As shown.

[0030] The schematic diagram of the current shunt operating mode of the inverter working bridge arm is shown below. Figure 3 As shown in the figure, when the three working upper or lower bridge arm switching devices are turned on in their respective working areas, the upper and lower bridge arm shunt switching devices S1 or S2 of the additional dynamic shunt branch and the corresponding additional dynamic shunt branch phase selection switch T are activated. a1 T b1 T c1 or T a2 T b2 T c2 This creates an additional dynamic shunt branch connected in parallel to the switching device, sharing the current flowing through it. It should be noted that, to highlight the current shunt within each operating range, Figure 3 The diagram only shows the conduction status of switching devices with shunt paths within the operating range; the operating modes of other switching devices are omitted.

[0031] The following explains in detail the shunt paths of the switching devices in each working area.

[0032] 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 a1 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 Meanwhile, i b <0 and i b a i b c V b2 On, corresponding to S2 and T b2 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 ;

[0033] The second work area has the following distribution path: Figure 3 As shown in (2). In this work area, i a >0 and i a >i b i a >i c V a1 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. a1 Share 50% of i a Meanwhile, i c <0 and i c a i c b V c2 On, corresponding to S2 and T c2 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 ;

[0034] 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 b1 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 Meanwhile, i c <0 and i c a i c b V c2 On, corresponding to S2 and T c2 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 fourth work area has the following distribution path: Figure 3 As shown in (4), in this working area, i b >0 and i b >i a i b >i c V b1 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. b1 Share 50% of i b Meanwhile, i a <0 and i a b i a c V a2 On, corresponding to S2 and T a2 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 ;

[0036] 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 c1 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 Meanwhile, i a <0 and i a b i a c ​​​​​​V a2 On, corresponding to S2 and T a2 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 sixth work area has the following distribution path: Figure 3 As shown in (6), in this working area, i c >0 and i c >i a i c >i b V c1 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. c1 Share 50% of i c Meanwhile, i b <0 and i b a i b c V b2 On, corresponding to S2 and T b2 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 .

[0038] Specific application examples are as follows:

[0039] Build such in simulation software Figure 4 The test system is shown.

[0040] Figure 5 The waveforms show the grid-connected AC system voltage of the three-phase two-level voltage source inverter in this patent, as well as the three-phase output current of the inverter and the current of each switching device.

[0041] Set the disturbance in 0.5s, such as Figure 5 (a) shows that the AC system voltage amplitude drops from 300V to 200V. As a result, the inverter-injected AC system current I... sa I sb I sc The amplitude increases significantly, such as Figure 5 As shown in (b), the current flows through the working bridge arm switching device V. a1 V b1 V c1 and V a2 V b2 V c2 ​​There is a risk of inverter failure and shutdown due to overcurrent damage to components. An additional dynamic shunt branch is activated 0.5 seconds after the disturbance occurs. The current in the upper and lower bridge arms of the shunt branch is as follows: Figure 5 As shown in (b) and 5(d), after shunting, the current of the switching devices in the working bridge arm can be significantly reduced, such as... Figure 5 (c) and 5(e) I va1 I vb1 I vc1 and I va2 I vb2 I vc2 As shown, the maximum current of the upper and lower working bridge arms can be reduced by ΔI. p ΔI n Simulation results show that the three-phase two-level voltage source inverter based on dynamic shunt branch proposed in this patent can significantly reduce the overcurrent of the inverter working bridge arm switching devices caused by AC system disturbances, and improve the reliability of inverter operation.

Claims

1. A three-phase two-level 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 inverter A, B, C three-phase upper and lower bridge arm shunt switch device S1, S2, as the additional dynamic shunt branch inverter A, B, C three-phase selection switch device T a1 , T b1 , T c1 and T a2 , T b2 , T c2 ; 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 a1 , b1 , c1 of the additional dynamic shunt branch is turned on, and the upper bridge arm shunt switch device S1 is shunted in parallel to 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 a2 , b2 , c2 of the additional dynamic shunt branch is turned on, and the lower bridge arm shunt switch device S2 shunts the phase with the maximum reverse current in parallel. The collector of S1 is connected to the positive pole of the current, and the emitter of S1 is connected to T a1 , the anode of T b1 , the anode of T c1 ​ The emitter of S2 is connected to the negative terminal of the power supply, and the collector of S2 is connected to T a2 , the cathode of T b2 , the cathode of T c2 . T a1 cathode and T a2 The anode is connected to the phase A output; T b1 cathode and a T b2 anode connected as a B phase output; T c1 cathode and T c2 The anode is connected to the phase C, which is used as the output phase C.

2. The three-phase two-level voltage source inverter according to claim 1, characterized in that, 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 IGBTs.

3. The three-phase two-level voltage source inverter according to claim 1, characterized in that, The three-phase upper and lower bridge arm shunt switch devices S1, S2 of the inverter A, B, C are IGBTs.

4. The three-phase two-level 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, for gate turn-off thyristor​​​​​ 5. The three-phase two-level voltage source inverter according to claim 1, characterized by Also comprise: 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 on, corresponding to S1 and T a1 on and as an additional dynamic shunt branch, with the upper working bridge arm V a1 A shared 50% of i a ; at the same time, i b <0 and i b <i a , i b <i c , V b2 on, corresponding to S2 and T b2 on and as an additional dynamic shunt branch, with the lower working bridge arm V b2 B shared 50% of i b ; The second working area, in which i a >0 and i a >i b , i a >i c , V a1 is turned on, corresponding to S1 and T a1 is turned on and as an additional dynamic shunt branch, sharing 50% of i a1 with V a ; at the same time, i c <0 and i c <i a , i c <i b , V c2 is turned on, corresponding to S2 and T c2 is turned on and as an additional dynamic shunt branch, sharing 50% of i c2 with V c ; The third working area, in this working area, i b >0 and i b <i a , i b <i c , V b1 is turned on, corresponding to S1 and T b1 is turned on and as an additional dynamic shunt branch, with B phase upper working bridge arm V b1 share 50% of i b ; at the same time, i c <0 and i c <i a , i c <i b , V c2 is turned on, corresponding to S2 and T c2 is turned on and as an additional dynamic shunt branch, with C phase lower working bridge arm V c2 share 50% of i c ; The fourth working area, in this working area, i b >0 and i b <i a , i b <i c , V b1 is turned on, corresponding to S1 and T b1 is turned on and as an additional dynamic shunt branch, sharing 50% of i b1 with B-phase lower working bridge arm V b ; at the same time, i a <0 and i a <i b , i a <i c , V a2 is turned on, corresponding to S2 and T a2 is turned on and as an additional dynamic shunt branch, sharing 50% of i a2 with A-phase lower working bridge arm V a ; The fifth working area, in this working area, i c >0 and i c >i a , i c >i b , V c1 is turned on, corresponding to S1 and T c1 is turned on and as an additional dynamic shunt branch, sharing 50% of i c1 with C-phase upper working bridge arm V c ; at the same time, i a <0 and i a <i b , i a <i c , V a2 is turned on, corresponding to S2 and T a2 is turned on and as an additional dynamic shunt branch, sharing 50% of i a2 with A-phase lower working bridge arm V a ; Sixth operating region, in which i c > 0 and i c < i a , i c > 0 and i b < 0, V c1 is on, corresponding to S1 and T c1 is on and as an additional dynamic shunt branch, shares 50% of i c1 with C-phase upper operating bridge arm V c ; at the same time, i b < 0 and i b > i a , i b > i c < 0, V b2 is on, corresponding to S2 and T b2 is on and as an additional dynamic shunt branch, shares 50% of i b2 with B-phase lower operating bridge arm V b .

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