A diode neutral point clamped three-level inverter

Abstract

This invention discloses a diode-neutral-clamped three-level inverter. Based on the existing inverter topology, by adding additional dynamic shunt branches to the upper and lower arms of the inverter's A, B, and C phases, without changing the electrical coupling characteristics between the inverter and the AC grid, the internal topology adjustment provides a dynamic shunt path for the inverter's working arm current. Thus, in the event of a sudden increase in grid-side current, the additional dynamic shunt branches shunt the current to the switching devices of the diode-neutral-clamped three-level inverter's working arms, preventing damage to the switching devices due to overcurrent, and improving the inverter's safe grid connection capability and its support capability for power system stability.

Description

Technical Field

[0001] This invention relates to the field of electronic technology, and in particular to a diode-neutral-clamped three-level 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 increases 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. Therefore, providing an inverter that can both provide dynamic reactive power support to the AC grid and improve its overcurrent withstand capability has become an urgent problem to be solved. Summary of the Invention

[0004] To address the technical problem that existing inverter control strategies, while improving the inverter's overcurrent withstand capability, increase the electrical distance between the inverter and the AC system, thus hindering the inverter's ability to provide dynamic reactive power support to the AC grid, this invention is proposed. An embodiment of this invention provides a diode-neutral-clamped three-level inverter that does not alter the electrical coupling characteristics between the inverter and the AC grid. Through internal topology adjustments, it provides a dynamic current shunt path for the inverter's working arm current, reducing the current in the working arm switching devices. This reduces the risk of inverter damage or grid disconnection due to overcurrent in the switching devices, improves the inverter's ability to withstand disturbances from the grid-connected AC system, and ensures the safe and stable operation of the inverter's grid-connected system.

[0005] According to one aspect of the present invention, a diode-neutral-clamped three-level inverter is provided, comprising:

[0006] The switching devices V of the upper working bridge arms of the inverter's three phases A, B, and C a1 V a2 V b1 V b2 V c1 V c2The switching devices V of the lower working bridge arms of the inverter's three phases A, B, and C a3 V a4 V b3 V b4 V c3 V c4 ;

[0007] The anti-correlation diodes VD corresponding to the upper working bridge arms of phases A, B, and C of the inverter. a1 VD a2 VD b1 VD b2 VD c1 VD c2 The anti-correlation diodes VD corresponding to the lower working bridge arms of phases A, B, and C of the inverter. a3 VD a4 VD b3 VD b4 VD c3 VD c4 ;

[0008] Clamping diode D of the upper working bridge arm of the inverter's three phases A, B, and C a1 D b1 D c1 Clamping diodes D of the lower working bridge arms of the inverter's A, B, and C phases a2 D b2 D c2 ;

[0009] The additional dynamic shunt branch of the upper working bridge arm of the inverter's three phases A, B, and C includes a diode D1 connected to the neutral point O of the inverter's DC side, switching devices S1 and S2 connected to the diode D1, and a switching device T connected to the switching device S2 for selecting the phases of the inverter's three phases A, B, and C. a1 T b1 and T c1 ;

[0010] The additional dynamic shunt branch of the lower working bridge arm of the inverter's three phases A, B, and C includes a diode D2 connected to the neutral point O of the inverter's DC side, switching devices S3 and S4 connected to the diode D2, and a switching device T connected to the switching device S4 for phase selection of the inverter's three phases A, B, and C. a2 T b2 and T c2 ;

[0011] The neutral point O of the inverter's DC side is connected to the positive and negative terminals of the inverter's DC side via capacitors C1 and C2, respectively.

[0012] When the positive direction of the current in the inverter is from the DC side to the AC side, and the three-phase current i on the AC side of the inverter... a i b i c When the phase with the maximum positive current is in the middle, the switching device T in the additional dynamic shunt branch of the upper working bridge arm of the inverter's three phases A, B, and C is turned on. a1 T b1 T c1 Furthermore, diodes D1, switching devices S1 and S2 in the additional dynamic shunt branch of the upper working bridge arm of the inverter A, B, and C phases perform parallel shunt for the phase with the maximum forward current.

[0013] When the positive direction of the current in the inverter is from the DC side to the AC side, and the three-phase current i on the AC side of the inverter... a i b i c When the phase with the maximum reverse current is in the middle, the switching device T in the additional dynamic shunt branch of the lower working bridge arm of the inverter corresponding to the conduction of phases A, B, and C is turned on. a2 T b2 T c2 Furthermore, diodes D2, switching devices S3 and S4 in the additional dynamic shunt branch of the lower working bridge arm of the inverter A, B, and C phases are connected in parallel to shunt the phase with the maximum reverse current.

[0014] Optionally, in the inverter embodiments described above, the switching devices V of the upper working bridge arms of the inverter's three phases A, B, and C are... a1 V a2 V b1 V b2 V c1 V c2 The switching devices V of the lower working bridge arms of the inverter's three phases A, B, and C a3 V a4 V b3 V b4 V c3 V c4 All of them are insulated gate bipolar transistors (IGBTs).

[0015] Optionally, in the inverter embodiments described above, the switching devices S1 and S2 in the additional dynamic shunt branch of the upper working bridge arm of the inverter A, B, and C phases, and the switching devices S3 and S4 in the additional dynamic shunt branch of the lower working bridge arm of the inverter A, B, and C phases, are all IGBTs (Insulated Gate Bipolar Transistors).

[0016] Optionally, in the inverter embodiments described above, the switching device T in the additional dynamic shunt branch of the upper working bridge arm of the inverter's three phases A, B, and C... a1 Tb1 and T c1 And the switching device T in the additional dynamic shunt branch of the lower working bridge arm of the inverter's A, B, and C phases. a2 T b2 and T c2 All are gate turn-off thyristors (GTOs).

[0017] Optionally, in the inverter embodiments described above, the AC current operating range of the inverter is divided into six regions based on the polarity of the inverter's AC current and the current flow of the switching devices in the inverter, wherein:

[0018] In the first operating region, when phase A of the inverter's three-phase upper arm (A, B, C) outputs in state P and phase B outputs in state N, i a >0 and i a >i b i a >i c V a1 V a2 When the circuit is turned on, the corresponding switching devices S1, S2 and T a1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase A of the inverter, connected to the switching device V of the working arm of phase A. a1 V a2 Share 50% of i a Meanwhile, i b <0 and i b a i b c V b3 V b4 When the circuit is turned on, the corresponding switching devices S3, S4 and T b2 It is turned on and serves as an additional dynamic shunt branch for the lower arm of phase B of the inverter, connected to the switching device V of the lower working arm of phase B. b3 V b4 Share 50% of i b In this context, the P state and N state are assumed to be when the DC side neutral point voltage is 0, and the bridge arm outputs are high and low levels, respectively.

[0019] In the first operating region, when phases A and B of the upper arm of the inverter's three phases A, B, and C both output a zero state, i a >0 and i a >i b i a >i c D a1 V a2 When the circuit is turned on, the corresponding diode D1, switching device S2, and T are activated. a1 ​​It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase A of the inverter, connected to the working arm D of phase A. a1 V a2 Share 50% of i a Meanwhile, i b <0 and i b a i b c V b3 D b2 When the circuit is turned on, the corresponding switching devices S3 and T b2 And diode D2 is turned on and acts as an additional dynamic shunt branch for the lower arm of phase B of the inverter, connecting with the lower working arm V of phase B. b3 D b2 Share 50% of i b In this case, the O state is assumed to be when the DC side neutral point voltage is 0, and the bridge arm output is at a 0 level.

[0020] In the second operating region, when phase A of the inverter's three-phase A, B, and C arms outputs state P and phase C outputs state N, i a >0 and i a >i b i a >i c V a1 V a2 When the circuit is turned on, the corresponding switching devices S1, S2 and T a1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase A of the inverter, connected to the switching device V of the working arm of phase A. a1 V a2 Share 50% of i a Meanwhile, i c <0 and i c a i c b V c3 V c4 When the circuit is turned on, the corresponding switching devices S3, S4 and T c2 It is turned on and serves as an additional dynamic shunt branch for the lower arm of phase C of the inverter, connected to the switching device V of the lower working arm of phase C. c3 V c4 Share 50% of i c ;

[0021] In the second working region, when both phases A and C output a 0 state, i a >0 and i a >i b i a >i c D a1 ​​​​V a2 When the circuit is turned on, the corresponding diode D1, switching device S2, and T are activated. a1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase A of the inverter, connected to the working arm D of phase A. a1 V a2 Share 50% of i a Meanwhile, i c <0 and i c a i c b V c3 D c2 When the circuit is turned on, the corresponding switching device T c2 And S3, and diode D2 are turned on and serve as an additional dynamic shunt branch for the lower arm of the C phase of the inverter, connected to the lower working arm V of the C phase. c3 D c2 Share 50% of i c ;

[0022] In the third operating region, when phase B of the inverter's three-phase (A, B, C) upper arm outputs state P and phase C outputs state N, i b >0 and i b >i a i b >i c V b1 V b2 When the circuit is turned on, the corresponding switching devices S1, S2 and T are activated. b1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase B of the inverter, connected to the switching device V of the working arm of phase B. b1 V b2 Share 50% of i b Meanwhile, i c <0 and i c a i c b V c3 V c4 When the circuit is turned on, the corresponding switching devices S3, S4 and T are activated. c2 It is turned on and serves as an additional dynamic shunt branch for the lower arm of phase C of the inverter, connected to the switching device V of the lower working arm of phase C. c3 V c4 Share 50% of i c ;

[0023] In the third operating region, when phases B and C of the upper arm of the inverter's three phases A, B, and C both output a zero state, i b >0 and i b >i a i b ​​​​>i c D b1 V b2 When the circuit is turned on, the corresponding diode D1, and the switching devices S2 and T are activated. b1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase B of the inverter, connected to the working arm D of phase B. b1 V b2 Share 50% of i b Meanwhile, i c <0 and i c a i c b V c3 D c2 When the circuit is turned on, the corresponding switching device T c2 And S3, and diode D2 are turned on and serve as an additional dynamic shunt branch for the lower arm of the C phase of the inverter, connected to the lower working arm V of the C phase. c3 D c2 Share 50% of i c ;

[0024] In the fourth operating region, when phase B of the inverter's three-phase bridge arm (A, B, C) outputs state P and phase A outputs state N, i b >0 and i b >i a i b >i c V b1 V b2 When the circuit is turned on, the corresponding switching devices S1, S2 and T b1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase B of the inverter, connected to the switching device V of the working arm of phase B. b1 V b2 Share 50% of i b Meanwhile, i a <0 and i a b i a c V a3 V a4 When the circuit is turned on, the corresponding switching devices S3, S4 and T a2 It is turned on and serves as an additional dynamic shunt branch for the lower arm of phase A of the inverter, connected to the switching device V of the lower working arm of phase A. a3 V a4 Share 50% of i a ;

[0025] In the fourth operating region, when both phase B and phase A of the upper arm of the inverter's three phases A, B, and C output a state of 0, i b >0 and i​​​​b >i a i b >i c D b1 V b2 When the circuit is turned on, the corresponding diode D1, and the switching devices S2 and T are activated. b1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase B of the inverter, connected to the working arm D of phase B. b1 V b2 Share 50% of i b Meanwhile, i a <0 and i a b i a c V a3 D a2 When the circuit is turned on, the corresponding switching device T a2 And S3, and diode D2 are turned on and serve as an additional dynamic shunt branch for the lower arm of phase A of the inverter, connected to the lower working arm V of phase A. a3 D a2 Share 50% of i a ;

[0026] In the fifth operating region, when phase C of the inverter's three-phase (A, B, C) upper arm outputs P state and phase A outputs N state, i c >0 and i c >i a i c >i b V c1 V c2 When the circuit is turned on, the corresponding switching devices S1, S2 and T c1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase C of the inverter, connected to the switching device V of the working arm of phase C. c1 V c2 Share 50% of i c Meanwhile, i a <0 and i a b i a c V a3 V a4 On, corresponding to S3, S4 and T a2 It is turned on and serves as an additional dynamic shunt branch for the lower arm of phase A of the inverter, connected to the switching device V of the lower working arm of phase A. a3 V a4 Share 50% of i a ;

[0027] ​​​​In the fifth operating region, when both phase C and phase A of the upper arm of the inverter's three phases A, B, and C output a zero state, i c >0 and i c >i a i c >i b D c1 V c2 When the circuit is turned on, the corresponding diode D1, and the switching devices S2 and T are activated. c1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase C of the inverter, connected to the working arm D of phase C. c1 V c2 Share 50% of i c Meanwhile, i a <0 and i a b i a c V a3 D a2 When the circuit is turned on, the corresponding switching device T a2 And S3, and diode D2 are turned on and serve as an additional dynamic shunt branch for the lower arm of phase A of the inverter, connected to the lower working arm V of phase A. a3 D a2 Share 50% of i a ;

[0028] In the sixth operating region, when phase C of the inverter's three-phase (A, B, C) upper arm outputs state P and phase B outputs state N, i c >0 and i c >i a i c >i b V c1 V c2 When the circuit is turned on, the corresponding switching devices S1, S2 and T c1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase C of the inverter, connected to the switching device V of the working arm of phase C. c1 V c2 Share 50% of i c Meanwhile, i b <0 and i b a i b c V b3 V b4 On, corresponding to S3, S4 and T b2 It is turned on and serves as an additional dynamic shunt branch for the lower arm of phase B of the inverter, connected to the switching device V of the lower working arm of phase B. b3 V b4 Share 50% of i​​​​b ;

[0029] In the sixth operating region, when both phase C and phase B of the upper arm of the inverter's three phases A, B, and C output a state of 0, i c >0 and i c >i a i c >i b D c1 V c2 When the circuit is turned on, the corresponding diode D1, and the switching devices S2 and T are activated. c1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase C of the inverter, connected to the working arm D of phase C. c1 V c2 Share 50% of i c Meanwhile, i b <0 and i b a i b c V b3 D b2 When the circuit is turned on, the corresponding switching device T b2 And S3, and diode D2 are turned on and serve as an additional dynamic shunt branch for the lower arm of phase B of the inverter, connected to the lower working arm V of phase B. b3 D b2 Share 50% of i b .

[0030] Based on the diode-neutral-clamped three-level inverter provided in the above embodiments of the present invention, on the basis of the existing inverter topology, by adding additional dynamic shunt branches to the upper and lower bridge arms of the inverter's A, B, and C phases, without changing the electrical coupling characteristics between the inverter and the AC grid, the internal topology adjustment provides a dynamic shunt path for the inverter's working bridge arm current. Thus, in the event of a sudden increase in grid-side current, the additional dynamic shunt branches shunt the switching devices of the diode-neutral-clamped three-level inverter's working bridge arm, preventing damage to the switching devices due to overcurrent, and improving the inverter's safe grid connection capability and its support capability for power system stability.

[0031] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0032] ​​The above and other objects, features, and advantages of the present invention will become more apparent from the more detailed description of the embodiments of the invention in conjunction with the accompanying drawings. The drawings are provided to further illustrate the embodiments of the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings, the same reference numerals generally represent the same parts or steps.

[0033] Figure 1 This is a schematic diagram of the topology of a diode-neutral-clamped three-level inverter provided in an exemplary embodiment of the present invention;

[0034] Figure 2 This is a schematic diagram of the AC side current operating range division of a diode-neutral-clamped three-level inverter provided in an exemplary embodiment of the present invention;

[0035] Figure 3 This is a schematic diagram of current shunt in a diode-neutral-clamped three-level inverter provided in an exemplary embodiment of the present invention;

[0036] Figure 4 This is a schematic diagram of a test system for evaluating the performance of a diode-neutral-clamped three-level inverter, provided in an exemplary embodiment of the present invention.

[0037] Figure 5 This is a schematic diagram of the current change of a diode-neutral-clamped three-level inverter under AC system voltage disturbance, provided by an exemplary embodiment of the present invention. Detailed Implementation

[0038] Hereinafter, exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments of the present invention. It should be understood that the present invention is not limited to the exemplary embodiments described herein.

[0039] It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention.

[0040] Those skilled in the art will understand that the terms "first," "second," etc., in the embodiments of the present invention are only used to distinguish different steps, devices, or modules, and do not represent any specific technical meaning, nor do they indicate a necessary logical order between them.

[0041] It should also be understood that in the embodiments of the present invention, "multiple" can refer to two or more, and "at least one" can refer to one, two or more.

[0042] It should also be understood that any component, data or structure mentioned in the embodiments of the present invention can generally be understood as one or more unless explicitly defined or given contrary instructions in the context.

[0043] Furthermore, the term "and / or" in this invention is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this invention generally indicates that the preceding and following related objects have an "or" relationship.

[0044] It should also be understood that the description of the various embodiments in this invention emphasizes the differences between the various embodiments, and the similarities or similarities can be referred to each other. For the sake of brevity, they will not be described in detail.

[0045] At the same time, it should be understood that, for ease of description, the dimensions of the various parts shown in the accompanying drawings are not drawn according to actual scale.

[0046] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0047] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0048] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0049] The embodiments of this invention can be applied to electronic devices such as terminal devices, computer systems, and servers, and can operate together with a wide range of other general-purpose or special-purpose computing system environments or configurations. Well-known examples of terminal devices, computing systems, environments, and / or configurations suitable for use with electronic devices such as terminal devices, computer systems, and servers include, but are not limited to: personal computer systems, server computer systems, thin clients, thick clients, handheld or laptop devices, microprocessor-based systems, set-top boxes, programmable consumer electronics, network PCs, minicomputer systems, mainframe computer systems, and distributed cloud computing environments including any of the above systems, etc.

[0050] Electronic devices such as terminal devices, computer systems, and servers can be described in the general context of computer system executable instructions (such as program modules) executed by a computer system. Typically, program modules can include routines, programs, object programs, components, logic, data structures, etc., which perform specific tasks or implement specific abstract data types. Computer systems / servers can be implemented in distributed cloud computing environments, where tasks are executed by remote processing devices linked through communication networks. In distributed cloud computing environments, program modules can reside on local or remote computing system storage media, including storage devices.

[0051] Figure 1 This is a schematic diagram of the topology of a diode-neutral-clamped three-level inverter provided in an exemplary embodiment of the present invention. Figure 1 As shown, U dc i represents the DC-side voltage of the diode-clamped three-level inverter described in this embodiment. a i b i c The current is the three-phase current on the AC side of the inverter, and its positive direction is from the DC side to the AC side of the inverter. The diode neutral point clamped three-level inverter described in this embodiment includes:

[0052] The switching devices V of the upper working bridge arms of the inverter's three phases A, B, and C a1 V a2 V b1 V b2 V c1 V c2 The switching devices V of the lower working bridge arms of the inverter's three phases A, B, and C a3 V a4 V b3 V b4 V c3 V c4 The anti-correlation diodes VD corresponding to the upper working arms of the inverter's A, B, and C phases. a1 VD a2 VD b1 VD b2 VD c1 VD c2 The anti-correlation diodes VD corresponding to the lower working bridge arms of phases A, B, and C of the inverter. a3 VD a4 VD b3 VD b4 VD c3 VD c4 ;

[0053] Clamping diode D of the upper working bridge arm of the inverter's three phases A, B, and C a1D b1 D c1 Clamping diodes D of the lower working bridge arms of the inverter's A, B, and C phases a2 D b2 D c2 ;

[0054] The additional dynamic shunt branch of the upper working bridge arm of the inverter's three phases A, B, and C includes a diode D1 connected to the neutral point O of the inverter's DC side, switching devices S1 and S2 connected to the diode D1, and a switching device T connected to the switching device S2 for selecting the phases of the inverter's three phases A, B, and C. a1 T b1 and T c1 ;

[0055] The additional dynamic shunt branch of the lower working bridge arm of the inverter's three phases A, B, and C includes a diode D2 connected to the neutral point O of the inverter's DC side, switching devices S3 and S4 connected to the diode D2, and a switching device T connected to the switching device S4 for phase selection of the inverter's three phases A, B, and C. a2 T b2 and T c2 ;

[0056] The neutral point O of the inverter's DC side is connected to the positive and negative terminals of the inverter's DC side via capacitors C1 and C2, respectively.

[0057] When the three-phase current i on the AC side of the inverter a i b i c When the phase with the maximum positive current is in the middle, the switching device T in the additional dynamic shunt branch of the upper working bridge arm of the inverter corresponding to the A, B, and C phases is turned on. a1 T b1 T c1 Furthermore, diodes D1, switching devices S1 and S2 in the additional dynamic shunt branch of the upper working bridge arm of the inverter A, B, and C phases perform parallel shunt for the phase with the maximum forward current.

[0058] When the three-phase current i on the AC side of the inverter a i b i c When the phase with the maximum reverse current is in the middle, the switching device T in the additional dynamic shunt branch of the lower working bridge arm of the inverter corresponding to the A, B, and C phases is turned on. a2 T b2 T c2 Furthermore, diodes D2, switching devices S3 and S4 in the additional dynamic shunt branch of the lower working bridge arm of the inverter A, B, and C phases are connected in parallel to shunt the phase with the maximum reverse current.

[0059] Optionally, the switching devices V of the upper working bridge arms of the inverter's three phases A, B, and C... a1 V a2 V b1 V b2 V c1 V c2 The switching devices V of the lower working bridge arms of the inverter's three phases A, B, and C a3 V a4 V b3 V b4 V c3 V c4 All of them are insulated gate bipolar transistors (IGBTs).

[0060] Optionally, the switching devices S1 and S2 in the additional dynamic shunt branch of the upper working bridge arm of the inverter A, B, and C phases, and the switching devices S3 and S4 in the additional dynamic shunt branch of the lower working bridge arm of the inverter A, B, and C phases, are all IGBTs (Insulated Gate Bipolar Transistors).

[0061] Optionally, the switching device T in the additional dynamic shunt branch of the upper working bridge arm of the inverter's three phases A, B, and C... a1 T b1 and T c1 And the switching device T in the additional dynamic shunt branch of the lower working bridge arm of the inverter's A, B, and C phases. a2 T b2 and T c2 All are gate turn-off thyristors (GTOs).

[0062] Specifically, the present invention is accomplished through the following technical solution:

[0063] According to i a i b i c The phase with the maximum positive current corresponds to the phase selection switching device T in the additional shunt branch of the upper bridge arm that conducts phases A, B, and C. a1 T b1 T c1 The upper bridge arm switching devices S1, S2, and D1 of the additional dynamic shunt branch are connected in parallel to shunt the current to this phase, thereby reducing the switching device V of the corresponding phase in the upper working bridge arm of the inverter's three phases A, B, and C. a1 V a2 V b1 V b2 V c1 V c2 and D a1 D b1 D c1 The current flowing through it; according to i ai 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 bridge arm switching devices S3, S4, and D2 of the additional dynamic shunt branch are connected in parallel to shunt the current to this phase, thereby reducing the switching device V in the corresponding phase of the lower working bridge arm of the inverter. a3 V a4 V b3 V b4 V c3 V c4 and D a2 D b2 D 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 a2 V b1 V b2 V c1 V c2 V a3 V a4 V b3 V b4 V c3 V c4 and clamping diode D a1 D b1 D c1 D a2 D b2 D 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.

[0064] Optionally, the AC current operating range of the inverter can be divided into 6 regions based on the polarity of the inverter's AC current and the current flow of the switching devices in the inverter. Figure 2 This is a schematic diagram illustrating the division of the AC side current operating range of a diode-neutral-clamped three-level inverter according to an exemplary embodiment of the present invention. Figure 2 As shown, the three-phase current i on the AC side of the inverter varies according to different time periods. a i b i c The polarity of the current divides the AC side current operating range into 6 regions.

[0065] Figure 3 This is a schematic diagram of current shunt in a diode-neutral-clamped three-level inverter provided in an exemplary embodiment of the present invention. Figure 3As shown, when the upper arm switching devices of the three phases A, B, and C of the inverter or the lower arm switching devices of the three phases A, B, and C are turned on in their respective regions, the upper and lower arm switching devices S1, S2, S3, and S4 with additional dynamic shunt branches, the clamping diodes D1 and D2, and the corresponding additional dynamic shunt branch switching device T are used for phase selection. 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.

[0066] The following is combined with Figure 3 It details the shunt paths of the inverter switching devices in each operating area.

[0067] In the first operating region, when phase A of the inverter's three-phase (A, B, C) upper arm outputs P state and phase B outputs N state, the shunt flow path is as follows: Figure 3 As shown in (a). In this work area, i a >0 and i a >i b i a >i c V a1 V a2 When the circuit is turned on, the corresponding switching devices S1, S2 and T a1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase A of the inverter, connected to the switching device V of the working arm of phase A. a1 V a2 Share 50% of i a Meanwhile, i b <0 and i b a i b c V b3 V b4 When the circuit is turned on, the corresponding switching devices S3, S4 and T b2 It is turned on and serves as an additional dynamic shunt branch for the lower arm of phase B of the inverter, connected to the switching device V of the lower working arm of phase B. b3 V b4 Share 50% of i b In this context, the P state and N state are assumed to be when the DC side neutral point voltage is 0, and the bridge arm outputs are high and low levels, respectively.

[0068] ​​In the first operating region, when phases A and B of the upper arm of the inverter's three phases A, B, and C both output a zero state, the shunt flow path is as follows: Figure 3 As shown in (b). In this work area, i a >0 and i a >i b i a >i c D a1 V a2 When the circuit is turned on, the corresponding diode D1, switching device S2, and T are activated. a1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase A of the inverter, connected to the working arm D of phase A. a1 V a2 Share 50% of i a Meanwhile, i b <0 and i b a i b c V b3 D b2 When the circuit is turned on, the corresponding switching devices S3 and T b2 And diode D2 is turned on and acts as an additional dynamic shunt branch for the lower arm of phase B of the inverter, connecting with the lower working arm V of phase B. b3 D b2 Share 50% of i b In this case, the O state is assumed to be when the DC side neutral point voltage is 0, and the bridge arm output is at a 0 level.

[0069] In the second operating region, when phase A of the inverter's three-phase (A, B, C) upper arm is in state P and phase C is in state N, the shunt current path is as follows: Figure 3 As shown in (c). In this work area, i a >0 and i a >i b i a >i c V a1 V a2 When the circuit is turned on, the corresponding switching devices S1, S2 and T a1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase A of the inverter, connected to the switching device V of the working arm of phase A. a1 V a2 Share 50% of i a Meanwhile, i c <0 and i c a i c b V c3 V c4 ​​​​When the circuit is turned on, the corresponding switching devices S3, S4 and T c2 It is turned on and serves as an additional dynamic shunt branch for the lower arm of phase C of the inverter, connected to the switching device V of the lower working arm of phase C. c3 V c4 Share 50% of i c ;

[0070] In the second working region, when both phases A and C output a 0 state, the shunt flow path is as follows: Figure 3 As shown in (d). In this work area, i a >0 and i a >i b i a >i c D a1 V a2 When the circuit is turned on, the corresponding diode D1, switching device S2, and T are activated. a1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase A of the inverter, connected to the working arm D of phase A. a1 V a2 Share 50% of i a Meanwhile, i c <0 and i c a i c b V c3 D c2 When the circuit is turned on, the corresponding switching device T c2 And S3, and diode D2 are turned on and serve as an additional dynamic shunt branch for the lower arm of the C phase of the inverter, connected to the lower working arm V of the C phase. c3 D c2 Share 50% of i c ;

[0071] In the third operating region, when phase B of the inverter's three-phase (A, B, C) upper arm outputs state P and phase C outputs state N, the shunt flow path is as follows: Figure 3 As shown in (e). In this work area, i b >0 and i b >i a i b >i c V b1 V b2 When the circuit is turned on, the corresponding switching devices S1, S2 and T are activated. b1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase B of the inverter, connected to the switching device V of the working arm of phase B. b1 V b2 Share 50% of i b Meanwhile, i c <0 and i​​c a i c b V c3 V c4 When the circuit is turned on, the corresponding switching devices S3, S4 and T are activated. c2 It is turned on and serves as an additional dynamic shunt branch for the lower arm of phase C of the inverter, connected to the switching device V of the lower working arm of phase C. c3 V c4 Share 50% of i c ;

[0072] In the third operating region, when phases B and C of the upper arm of the inverter's three phases A, B, and C both output a zero state, the shunt flow path is as follows: Figure 3 As shown in (f). In this work area, i b >0 and i b >i a i b >i c D b1 V b2 When the circuit is turned on, the corresponding diode D1, and the switching devices S2 and T are activated. b1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase B of the inverter, connected to the working arm D of phase B. b1 V b2 Share 50% of i b Meanwhile, i c <0 and i c a i c b V c3 D c2 When the circuit is turned on, the corresponding switching device T c2 And S3, and diode D2 are turned on and serve as an additional dynamic shunt branch for the lower arm of the C phase of the inverter, connected to the lower working arm V of the C phase. c3 D c2 Share 50% of i c ;

[0073] In the fourth operating region, when phase B of the inverter's three-phase (A, B, C) upper arm outputs state P and phase A outputs state N, the shunt flow path is as follows: Figure 3 As shown in (g). In this working area, i b >0 and i b >i a i b >i c V b1 V b2 When the circuit is turned on, the corresponding switching devices S1, S2 and T b1 ​​​​It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase B of the inverter, connected to the switching device V of the working arm of phase B. b1 V b2 Share 50% of i b Meanwhile, i a <0 and i a b i a c V a3 V a4 When the circuit is turned on, the corresponding switching devices S3, S4 and T a2 It is turned on and serves as an additional dynamic shunt branch for the lower arm of phase A of the inverter, connected to the switching device V of the lower working arm of phase A. a3 V a4 Share 50% of i a ;

[0074] In the fourth operating region, when both phase B and phase A of the upper arm of the inverter's three phases A, B, and C output a zero state, the shunt flow path is as follows: Figure 3 As shown in (h). In this work area, i b >0 and i b >i a i b >i c D b1 V b2 When the circuit is turned on, the corresponding diode D1, and the switching devices S2 and T are activated. b1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase B of the inverter, connected to the working arm D of phase B. b1 V b2 Share 50% of i b Meanwhile, i a <0 and i a b i a c V a3 D a2 When the circuit is turned on, the corresponding switching device T a2 And S3, and diode D2 are turned on and serve as an additional dynamic shunt branch for the lower arm of phase A of the inverter, connected to the lower working arm V of phase A. a3 D a2 Share 50% of i a ;

[0075] In the fifth operating region, when phase C of the inverter's three-phase (A, B, C) upper arm is in state P and phase A is in state N, the shunt flow path is as follows: Figure 3 As shown in (i). In this work area, i c >0 and i c >i​​​​a i c >i b V c1 V c2 When the circuit is turned on, the corresponding switching devices S1, S2 and T c1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase C of the inverter, connected to the switching device V of the working arm of phase C. c1 V c2 Share 50% of i c Meanwhile, i a <0 and i a b i a c V a3 V a4 On, corresponding to S3, S4 and T a2 It is turned on and serves as an additional dynamic shunt branch for the lower arm of phase A of the inverter, connected to the switching device V of the lower working arm of phase A. a3 V a4 Share 50% of i a ;

[0076] In the fifth operating region, when both phase C and phase A of the upper arm of the inverter's three phases A, B, and C are in the 0 state, the shunt flow path is as follows: Figure 3 As shown in (j). In this work area, i c >0 and i c >i a i c >i b D c1 V c2 When the circuit is turned on, the corresponding diode D1, and the switching devices S2 and T are activated. c1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase C of the inverter, connected to the working arm D of phase C. c1 V c2 Share 50% of i c Meanwhile, i a <0 and i a b i a c V a3 D a2 When the circuit is turned on, the corresponding switching device T a2 And S3, and diode D2 are turned on and serve as an additional dynamic shunt branch for the lower arm of phase A of the inverter, connected to the lower working arm V of phase A. a3 D a2 Share 50% of i a ;

[0077] ​​​​In the sixth operating region, when phase C of the inverter's three-phase (A, B, C) upper arm outputs in state P and phase B outputs in state N, the shunt current path is as follows: Figure 3 As shown in (k). In this working area, i c >0 and i c >i a i c >i b V c1 V c2 When the circuit is turned on, the corresponding switching devices S1, S2 and T c1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase C of the inverter, connected to the switching device V of the working arm of phase C. c1 V c2 Share 50% of i c Meanwhile, i b <0 and i b a i b c V b3 V b4 On, corresponding to S3, S4 and T b2 It is turned on and serves as an additional dynamic shunt branch for the lower arm of phase B of the inverter, connected to the switching device V of the lower working arm of phase B. b3 V b4 Share 50% of i b ;

[0078] In the sixth operating region, when both phase C and phase B of the upper arm of the inverter's three phases A, B, and C are in the 0 state, the shunt flow path is as follows: Figure 3 As shown in (l). In this working area, i c >0 and i c >i a i c >i b D c1 V c2 When the circuit is turned on, the corresponding diode D1, and the switching devices S2 and T are activated. c1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase C of the inverter, connected to the working arm D of phase C. c1 V c2 Share 50% of i c Meanwhile, i b <0 and i b a i b c V b3 D b2 When the circuit is turned on, the corresponding switching device T b2 ​​​​And S3, and diode D2 are turned on and serve as an additional dynamic shunt branch for the lower arm of phase B of the inverter, connected to the lower working arm V of phase B. b3 D b2 Share 50% of i b .

[0079] Figure 4 This is a schematic diagram of a test system for evaluating the performance of a diode-neutral-clamped three-level inverter, provided in an exemplary embodiment of the present invention. Figure 4 As shown, in the test system built in the simulation software to evaluate the performance of a diode-neutral-clamped three-level inverter, U dc U is the DC side voltage of the inverter. sa U sb and U sc This is the voltage output from the AC side of the inverter. The positive direction of the inverter current is from the DC side to the AC side.

[0080] Figure 5 This is a schematic diagram of the current change of a diode-neutral-clamped three-level inverter under AC system voltage disturbance, provided by an exemplary embodiment of the present invention. Figure 4 The test system is set to activate the additional dynamic shunt branch at 0.2s. For example... Figure 5 As shown in (a), the PWM voltage waveform at the AC output terminal of phase A of the diode-clamped three-level inverter described in this embodiment maintains a three-level output. Furthermore, as... Figure 5 As shown in (b), the voltage harmonics of the PWM voltage waveform at the AC output terminal of phase A of the diode-clamped three-level inverter remain unchanged after filtering. The test system activates the additional dynamic shunt branch at 0.2s. The currents of the switching devices in the upper and lower arms of the additional dynamic shunt branch are as follows: Figure 5 As shown in (c). After the current is shunted by the additional shunt branch device, the current of the switching devices in the inverter's working arm can be significantly reduced. Taking the AC output current of the upper arm and the current of the switching devices in the upper arm after the additional dynamic shunt is activated as an example, such as... Figure 5 As shown in (d), after the current is shunted by the additional shunt branch switching device, when the inverter's three phases A, B, and C output current I on the AC side... sa I sb and I sc At that time, the current I of the switching devices in the upper working bridge arms of the inverter's three phases A, B, and C is... Va1 I Va2 I Vb1 I Vb2 I Vc1 and I Vc2 This significantly reduces, specifically, the current in the upper working bridge arm can be reduced by ΔI. pSimulation results show that the diode-neutral-clamped three-level inverter based on an additional dynamic shunt branch proposed in this invention can significantly reduce the overcurrent of the inverter's working bridge arm switching devices and improve the inverter's operational reliability.

[0081] The basic principles of this disclosure have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this disclosure are merely examples and not limitations, and should not be considered as essential features of each embodiment of this disclosure. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the scope of this disclosure to the necessity of employing the aforementioned specific details for implementation.

[0082] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For system embodiments, since they largely correspond to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

[0083] The block diagrams of devices, apparatuses, devices, and systems disclosed herein are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0084] The methods and apparatus of this disclosure may be implemented in many ways. For example, they may be implemented by software, hardware, firmware, or any combination of software, hardware, and firmware. The above-described order of steps for the methods is for illustrative purposes only, and the steps of the methods of this disclosure are not limited to the order specifically described above unless otherwise specifically stated. Furthermore, in some embodiments, this disclosure may also be implemented as a program recorded on a recording medium, the program including machine-readable instructions for implementing the methods according to this disclosure. Thus, this disclosure also covers recording media storing programs for performing the methods according to this disclosure.

[0085] It should also be noted that in the apparatus, devices, and methods of this disclosure, the components or steps are decomposable and / or recombinable. Such decomposition and / or recombination should be considered equivalent to the present disclosure. The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use this disclosure. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of this disclosure. Therefore, this disclosure is not intended to be limited to the aspects shown herein, but rather to be carried out within the widest scope consistent with the principles and novel features disclosed herein.

[0086] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this disclosure to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations therein.

Claims

1. A diode-neutral-clamped three-level inverter, characterized in that, include: Switching devices of the upper working bridge arms of the inverter's three phases A, B, and C V a1 、V a2 , V b1 , V b2 , V c1 , V c2 Switching devices of the lower working bridge arms of the inverter's three phases A, B, and C V a3 、V a4 , V b3 , V b4 , V c3 , V c4 The anti-parallel diodes corresponding to the upper working arms of the inverter's A, B, and C phases. VD a1 VD a2 , VD b1 , VD b2 , VD c1 , VD c2 The anti-parallel diodes corresponding to the lower working arms of the inverter's A, B, and C phases. VD a3 VD a4 , VD b3 , VD b4 , VD c3 , VD c4 ; Clamping diode D of the upper working bridge arm of the inverter's three phases A, B, and C a1 D b1 D c1 Clamping diodes D of the lower working bridge arms of the inverter's A, B, and C phases a2 D b2 D c2 ; The additional dynamic shunt branch of the upper working bridge arm of the inverter's three phases A, B, and C includes a diode connected to the DC side neutral point O of the inverter. D 1. With diode D 1. Connected switching devices S 1 and S 2, and related to switching devices S 2. Connected switching devices for phase selection of the three phases A, B, and C of the inverter. T a1 、T b1 and T c1 ; The additional dynamic shunt branch of the lower working bridge arm of the inverter's three phases A, B, and C includes a diode connected to the DC side neutral point O of the inverter. D 2, with diode D 2 Connected switching devices S 3 and S 4, and related switching devices S 4. Connected switching devices for phase selection of the three phases A, B, and C of the inverter. T a2 、T b2 and T c2 ; The inverter DC side neutral point O is connected to a capacitor. C 1 and C 2. Connect to the positive and negative terminals of the DC side of the inverter, respectively; When the positive direction of the current in the inverter is from the DC side to the AC side, and the three-phase current on the AC side of the inverter... i a 、i b 、i c When a phase has the maximum positive current, the switching devices in the additional dynamic shunt branch of the upper working bridge arm of the inverter's three phases A, B, and C are turned on. T a1 、T b1 , T c1 Furthermore, the diodes in the additional dynamic shunt branches of the upper working bridge arms of the inverter's A, B, and C phases... D 1. Switching devices S 1 and S 2. The phase with the maximum positive current is connected in parallel for current shunting; When the positive direction of the current in the inverter is from the DC side to the AC side, and the three-phase current on the AC side of the inverter... i a 、i b 、i c When the phase with the maximum reverse current is in the middle, the switching devices in the additional dynamic shunt branch of the lower working bridge arm of the inverter's three phases A, B, and C are turned on. T a2 , T b2 , T c2 Furthermore, the diodes in the additional dynamic shunt branches of the lower working arms of the inverter's A, B, and C phases... D 2. Switching devices S 3 and S 4. The phase with the maximum reverse current is connected in parallel for current splitting.

2. The diode-neutral-clamped three-level inverter according to claim 1, characterized in that, Switching devices of the upper working bridge arms of the inverter's three phases A, B, and C V a1 、V a2 , V b1 , V b2 , V c1 , V c2 Switching devices of the lower working bridge arms of the inverter's three phases A, B, and C V a3 、V a4 , V b3 , V b4 , V c3 , V c4 All of them are insulated gate bipolar transistors (IGBTs).

3. The diode-neutral-clamped three-level inverter according to claim 1, characterized in that, Switching devices in the additional dynamic shunt branch of the upper working bridge arm of the inverter's three phases A, B, and C S 1 and S 2. And the switching devices in the additional dynamic shunt branches of the lower working arms of the inverter's A, B, and C phases. S 3 and S 4. All are Insulated Gate Bipolar Transistors (IGBTs).

4. The diode-neutral-clamped three-level inverter according to claim 1, characterized in that, Switching devices in the additional dynamic shunt branch of the upper working bridge arm of the inverter's three phases A, B, and C T a1 、T b1 and T c1 And the switching devices in the additional dynamic shunt branch of the lower working bridge arm of the inverter's A, B, and C phases. T a2 、T b2 and T c2 All are gate turn-off thyristors (GTOs).

5. The diode-neutral-clamped three-level inverter according to claim 1, characterized in that, Based on the polarity of the inverter's AC current and the current flow of the switching devices in the inverter, the AC side current operating range of the inverter is divided into 6 regions, among which: In the first operating region, when phase A of the inverter's three-phase upper arm (A, B, C) outputs state P and phase B outputs state N, i a >0 and i a > i b , i a > i c V a1 V a2 When the circuit is turned on, the corresponding switching devices S1, S2 and T a1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase A of the inverter, connected to the switching device V of the working arm of phase A. a1 V a2 Share 100% i a ;at the same time, i b <0 and i b < i a , i b < i c V b3 V b4 When the circuit is turned on, the corresponding switching devices S3, S4 and T b2 It is turned on and serves as an additional dynamic shunt branch for the lower arm of phase B of the inverter, connected to the switching device V of the lower working arm of phase B. b3 V b4 Share 100% i b In this context, the P state and N state are assumed to be when the DC side neutral point voltage is 0, and the bridge arm outputs are high and low levels, respectively. In the first operating region, when phases A and B of the upper bridge arm of the inverter's three phases A, B, and C both output a zero state, i a >0 and i a > i b , i a > i c D a1 V a2 When the circuit is turned on, the corresponding diode D1, switching device S2, and T are activated. a1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase A of the inverter, connected to the working arm D of phase A. a1 V a2 Share 100% i a ;at the same time, i b <0 and i b < i a , i b < i c V b3 D b2 When the circuit is turned on, the corresponding switching devices S3 and T b2 And diode D2 is turned on and acts as an additional dynamic shunt branch for the lower arm of phase B of the inverter, connecting with the lower working arm V of phase B. b3 D b2 Share 100% i b In this case, the O state is assumed to be when the DC side neutral point voltage is 0, and the bridge arm output is at a 0 level. In the second operating region, when phase A of the inverter's three-phase upper arm (A, B, and C) outputs state P and phase C outputs state N, i a >0 and i a > i b , i a > i c V a1 V a2 When the circuit is turned on, the corresponding switching devices S1, S2 and T a1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase A of the inverter, connected to the switching device V of the working arm of phase A. a1 V a2 Share 100% i a ;at the same time, i c <0 and i c < i a , i c < i b V c3 V c4 When the circuit is turned on, the corresponding switching devices S3, S4 and T c2 It is turned on and serves as an additional dynamic shunt branch for the lower arm of phase C of the inverter, connected to the switching device V of the lower working arm of phase C. c3 V c4 Share 100% i c ; In the second operating region, when phases A and C of the upper bridge arm of the inverter's three phases A, B, and C both output a zero state, i a >0 and i a > i b , i a > i c D a1 V a2 When the circuit is turned on, the corresponding diode D1, switching device S2, and T are activated. a1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase A of the inverter, connected to the working arm D of phase A. a1 V a2 Share 100% i a ;at the same time, i c <0 and i c < i a , i c < i b V c3 D c2 When the circuit is turned on, the corresponding switching device T c2 And S3, and diode D2 are turned on and serve as an additional dynamic shunt branch for the lower arm of the C phase of the inverter, connected to the lower working arm V of the C phase. c3 D c2 Share 100% i c ; In the third operating region, when phase B of the inverter's three-phase upper arm (A, B, and C) outputs state P and phase C outputs state N, i b >0 and i b > i a , i b > i c V b1 V b2 When the circuit is turned on, the corresponding switching devices S1, S2 and T b1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase B of the inverter, connected to the switching device V of the working arm of phase B. b1 V b2 Share 100% i b ;at the same time, i c <0 and i c < i a , i c < i b V c3 V c4 When the circuit is turned on, the corresponding switching devices S3, S4 and T c2 It is turned on and serves as an additional dynamic shunt branch for the lower arm of phase C of the inverter, connected to the switching device V of the lower working arm of phase C. c3 V c4 Share 100% i c ; In the third operating region, when phases B and C of the upper bridge arm of the inverter's three phases A, B, and C both output a zero state, i b >0 and i b > i a , i b > i c D b1 V b2 When the circuit is turned on, the corresponding diode D1, and the switching devices S2 and T are activated. b1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase B of the inverter, connected to the working arm D of phase B. b1 V b2 Share 100% i b ;at the same time, i c <0 and i c < i a , i c < i b V c3 D c2 When the circuit is turned on, the corresponding switching device T c2 And S3, and diode D2 are turned on and serve as an additional dynamic shunt branch for the lower arm of the C phase of the inverter, connected to the lower working arm V of the C phase. c3 D c2 Share 100% i c ; In the fourth operating region, when phase B of the upper arm of the inverter's three phases A, B, and C outputs state P and phase A outputs state N, i b >0 and i b > i a , i b > i c V b1 V b2 When the circuit is turned on, the corresponding switching devices S1, S2 and T b1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase B of the inverter, connected to the switching device V of the working arm of phase B. b1 V b2 Share 100% i b ;at the same time, i a <0 and i a < i b , i a < i c V a3 V a4 When the circuit is turned on, the corresponding switching devices S3, S4 and T a2 It is turned on and serves as an additional dynamic shunt branch for the lower arm of phase A of the inverter, connected to the switching device V of the lower working arm of phase A. a3 V a4 Share 100% i a ; In the fourth operating region, when both phase B and phase A of the upper arm of the inverter's three phases A, B, and C output a state of 0, i b >0 and i b > i a , i b > i c D b1 V b2 When the circuit is turned on, the corresponding diode D1, and the switching devices S2 and T are activated. b1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase B of the inverter, connected to the working arm D of phase B. b1 V b2 Share 100% i b ;at the same time, i a <0 and i a < i b , i a < i c V a3 D a2 When the circuit is turned on, the corresponding switching device T a2 And S3, and diode D2 are turned on and serve as an additional dynamic shunt branch for the lower arm of phase A of the inverter, connected to the lower working arm V of phase A. a3 D a2 Share 100% i a ; In the fifth operating region, when phase C of the upper bridge arm of the inverter (phases A, B, and C) outputs in state P and phase A outputs in state N, i c >0 and i c > i a , i c > i b V c1 V c2 When the circuit is turned on, the corresponding switching devices S1, S2 and T c1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase C of the inverter, connected to the switching device V of the working arm of phase C. c1 V c2 Share 100% i c ;at the same time, i a <0 and i a < i b , i a < i c V a3 V a4 When the circuit is turned on, the corresponding switching devices S3, S4 and T a2 It is turned on and serves as an additional dynamic shunt branch for the lower arm of phase A of the inverter, connected to the switching device V of the lower working arm of phase A. a3 V a4 Share 100% i a ; In the fifth operating region, when both phase C and phase A of the upper arm of the inverter's three phases A, B, and C output a zero state, i c >0 and i c > i a , i c > i b D c1 V c2 When the circuit is turned on, the corresponding diode D1, and the switching devices S2 and T are activated. c1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase C of the inverter, connected to the working arm D of phase C. c1 V c2 Share 100% i c ;at the same time, i a <0 and i a < i b , i a < i c V a3 D a2 When the circuit is turned on, the corresponding switching device T a2 And S3, and diode D2 are turned on and serve as an additional dynamic shunt branch for the lower arm of phase A of the inverter, connected to the lower working arm V of phase A. a3 D a2 Share 100% i a ; In the sixth operating region, when phase C of the inverter's three-phase (A, B, C) upper arm outputs P state and phase B outputs N state, i c >0 and i c > i a , i c > i b V c1 V c2 When the circuit is turned on, the corresponding switching devices S1, S2 and T c1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase C of the inverter, connected to the switching device V of the working arm of phase C. c1 V c2 Share 100% i c ;at the same time, i b <0 and i b < i a , i b < i c V b3 V b4 When the circuit is turned on, the corresponding switching devices S3, S4 and T b2 It is turned on and serves as an additional dynamic shunt branch for the lower arm of phase B of the inverter, connected to the switching device V of the lower working arm of phase B. b3 V b4 Share 100% i b ; In the sixth operating region, when both phase C and phase B of the upper arm of the inverter's three phases A, B, and C output a state of 0, i c >0 and i c > i a , i c > i b D c1 V c2 When the circuit is turned on, the corresponding diode D1, and the switching devices S2 and T are activated. c1 It is turned on and serves as an additional dynamic shunt branch for the upper arm of phase C of the inverter, connected to the working arm D of phase C. c1 V c2 Share 100% i c ;at the same time, i b <0 and i b < i a , i b < i c V b3 D b2 When the circuit is turned on, the corresponding switching device T b2 And S3, and diode D2 are turned on and serve as an additional dynamic shunt branch for the lower arm of phase B of the inverter, connected to the lower working arm V of phase B. b3 D b2 Share 100% i b .

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