Hybrid quasi-resonant soft-switching three-level ANPC converter and commutation strategy thereof

Abstract

The invention discloses a hybrid quasi-resonant soft switching three-level ANPC converter and a current conversion strategy thereof, belongs to the technical field of power electronic new energy grid connection, and solves the problem of how to reduce switching loss. In a converter topology, two switching tubes connected with the output end of a bridge arm adopt SiC devices, and the other switching tubes adopt Si devices; a quasi-resonance soft switching circuit is designed between the two SiC type switching tubes; in the positive half cycle of the output voltage, the switching sequence is (1 < 0 > 0 < 1 >) at positive level, and the switching sequence is (1 < 0 > 0 < 1 >) at zero level; in the negative half cycle of the output voltage, the switching sequence is (0101100) when the level is negative, and the switching sequence is (0101100) when the level is zero; the converter topology and the converter strategy are combined, the output switching frequency of the converter is improved, the switching loss of the converter is reduced, the voltage stress borne by the switching tubes is the same in any level state, the stability of the converter is improved, and meanwhile the converter has high cost performance.

Description

Technical Field

[0001] The invention belongs to the technical field of power electronic new energy grid-connected technology, and relates to a hybrid quasi-resonant soft-switching three-level ANPC converter and a commutation strategy thereof. Background Art

[0002] With the rapid increase in the proportion of renewable energy power generation, the new power system gradually presents the characteristics of "double high" (high proportion of renewable energy and high proportion of power electronic equipment). Compared with the traditional three-level topology, Fig.10 As shown in the figure, the active neutral point clamped (ANPC) three-level converter (all using silicon devices) is suitable for medium and high power fields due to its low switching stress and high output performance. It is lower in cost than multi-level converters and is simple to control, making it suitable for application in large-scale new energy access systems.

[0003] Compared with traditional silicon (Si) devices, wide bandgap power devices such as silicon carbide (SiC) have the advantages of fast switching speed, high temperature resistance and lower switching loss per device than traditional silicon devices. However, as the switching frequency increases, the switching loss will increase significantly after accumulation, leading to increased electromagnetic interference and reduced circuit efficiency.

[0004] Due to the high cost of SiC devices, it is a more urgent task to study how to strike a balance between the cost of SiC devices and their advantages in switching frequency and heat dissipation. Summary of the invention

[0005] The technical solution of the present invention is used to solve the problem of how to reduce switching losses.

[0006] The present invention solves the above technical problems through the following technical solutions: The present invention provides a hybrid quasi-resonant soft-switching three-level ANPC single-phase converter for inversion or rectification. In the three-level ANPC single-phase converter, two switch tubes connected to the output end of the bridge arm are connected to the output end of the bridge arm. and Adopt SiC type switch device, switch tube , , and Si-type switching devices are used; and in two SiC-type switching tubes and A quasi-resonant soft switching circuit is designed between the switch tube And switch tube During the dead time of switching on and off, the resonant capacitor and resonant inductor in the quasi-resonant soft switching circuit are connected in series to resonate. Achieve zero voltage turn-on and zero voltage turn-off, switch tube The natural zero voltage switching is achieved through the commutation process. When the resonant inductor of the quasi-resonant soft switching circuit is pre-charged, the switch tube is controlled. The shutdown achieves zero current shutdown.

[0007] Preferably, the quasi-resonant soft switching circuit comprises: a resonant capacitor , resonant inductor , resonant switch tube ; Resonant capacitor Connect in parallel to the switch Between the drain and source, the resonant inductor With resonant switch After connecting in series, connect in parallel to the output filter inductor Both ends, resonant switch tube The drain of the resonant switch is connected to the positive pole of the load. The source is connected to the resonant inductor one end.

[0008] Preferably, the SiC type switching device is a SiC type MOSFET device.

[0009] Preferably, the Si-type switching device is a Si-type IGBT device.

[0010] The present invention also provides a commutation strategy applied to the above hybrid quasi-resonant soft-switching three-level ANPC single-phase converter: the commutation strategy of the positive half-cycle of the output voltage of the single-phase converter is: the corresponding switch tube at the positive level ~ The switching sequence is (1 1 0 0 0 1), and the corresponding switch tube at zero level ~ The switching sequence is (1 0 1 0 0 1); the commutation strategy of the negative half cycle of the output voltage of the single-phase converter is: the corresponding switch tube is ~ The switching sequence is (0 0 1 1 1 0), and the corresponding switch tube at zero level ~ The switching sequence is (0 1 0 1 1 0).

[0011] Furthermore, when the output of the three-level ANPC single-phase converter switches from a positive level to a zero level, the switch tube , Keep conducting, switch After a period of dead time, the switch tube The anti-parallel diode Open, switch tube No current flows.

[0012] Furthermore, when the output of the three-level ANPC single-phase converter switches from zero level to positive level, the switch tube , Keep conducting, switch After a period of dead time, the switch tube Open, switch tube No current flows.

[0013] Furthermore, when the output of the three-level ANPC single-phase converter switches from a negative level to a zero level, the switch tube , Keep conducting, switch After a period of dead time, the switch tube The anti-parallel diode Open, switch tube No current flows.

[0014] Furthermore, when the output of the three-level ANPC single-phase converter switches from zero level to negative level, at this time, the switch tube , Keep conducting, switch After a period of dead time, the switch tube Open, switch tube No current flows.

[0015] The present invention also provides a hybrid quasi-resonant soft-switching three-level ANPC three-phase converter, wherein the three-level ANPC three-phase converter is formed by using the above-mentioned hybrid quasi-resonant soft-switching three-level ANPC single-phase converter.

[0016] The beneficial effects of the present invention are as follows: In the topology of the hybrid quasi-resonant soft-switching three-level ANPC converter proposed in the present invention, the two switch tubes connected to the output end of the bridge arm are and Adopt SiC type switch device, switch tube , , and Si type switching devices are used; the commutation strategy of the positive half cycle of the converter output voltage is: the corresponding switch tube ~ The switching sequence is (1 1 0 0 0 1), and the corresponding switch tube at zero level ~ The switching sequence is (1 0 1 0 0 1); the commutation strategy of the negative half-cycle of the converter output voltage is: the corresponding switch tube is ~ The switching sequence is (0 0 1 11 0), and the corresponding switch tube at zero level ~ The switching sequence is (0 1 0 1 1 0); the topology of the hybrid three-level ANPC converter of the present invention is combined with the commutation strategy to improve the output switching frequency of the converter, greatly reduce the switching loss of the converter, make each switch tube bear the same voltage stress under any level state, and improve the stability of the topology. At the same time, by comparing with other types of topologies at present, while ensuring the advantages of SiC and Si hybrid three-level ANPC converter circuits, the cost is controlled to achieve better cost performance; the quasi-resonant soft switching circuit significantly reduces the switching loss and improves the overall conversion efficiency by realizing zero voltage switching or zero current switching during the switching process; the current and voltage changes during the switching process are smoother than those of the hard switching three-level circuit, which can effectively reduce electromagnetic interference; at the same time, the cost is only increased by the resonant capacitor and resonant inductor with very small capacitance and inductance values ​​and ordinary MOSFET, and the circuit is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a topology diagram of a hybrid quasi-resonant soft-switching three-level ANPC single-phase converter according to Embodiment 1 of the present invention; Figure 2 is the switching sequence table of the three-level ANPC converter; FIG3 (a) is a schematic diagram of the switch tube state when the converter is in the switch state P and OL1; FIG3 (b) is a schematic diagram of the switch tube state when the converter is in the switch state N and OU1; Figure 4 This is a switching signal waveform diagram within one switching cycle of a hybrid quasi-resonant soft-switching three-level ANPC single-phase converter according to the first embodiment of the present invention; Figure 5 (a) is a current loop diagram of the OL1 state in a switching cycle of the positive half cycle; FIG5( b ) is a current loop diagram of a switching cycle in a resonant state in a positive half cycle; Figure 5 (c) is a current loop diagram for the P state in a switching cycle of the positive half cycle; Figure 5 (d) is a current loop diagram when the natural zero voltage is turned on in a switching cycle in the positive half cycle; Figure 6 A topological diagram of a hybrid quasi-resonant soft-switching three-level ANPC three-phase converter according to the second embodiment of the present invention; FIG7 (a) is a graph showing the switching loss and conduction loss of the three-level ANPC converter and its commutation strategy according to the present invention; FIG7( b ) is a graph showing the switching loss and conduction loss of a three-level ANPC converter using four SiC switching devices and two Si switching devices (referred to as 4-SiC hybrid) ; FIG7 (c) is a graph showing the switching loss and conduction loss of a three-level ANPC converter in which all six switching devices are SiC type (referred to as full SiC type) switching devices; FIG7( d ) is a graph showing the switching loss and conduction loss of a three-level ANPC converter in which all six switching devices are Si-type (referred to as full Si-type) switching devices; Figure 8 (a) is a comparison of the total loss distribution of four single-phase three-level ANPC topologies under their respective optimal modulation strategies when the phase voltage output apparent frequency is high (2000 Hz) and the power factor is 1; Figure 8 (b) is a comparison of the total loss distribution of the four single-phase three-level ANPC topologies under their respective optimal modulation strategies when the phase voltage output apparent frequency is high (2000 Hz) and the power factor is -1; Figure 9 (a) is a comparison of the total loss distribution of four single-phase three-level ANPC topologies under their respective optimal modulation strategies when the phase voltage output apparent frequency is low (500 Hz) and the power factor is 1; Figure 9 (b) is a comparison of the total loss distribution of four single-phase three-level ANPC topologies under their respective optimal modulation strategies when the phase voltage output apparent frequency is low (500 Hz) and the power factor is -1; Fig.10 The circuit diagram of the existing ANPC three-level converter using all silicon devices is shown in FIG. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments: Embodiment 1 like Figure 1 As shown, an embodiment of the present invention provides a hybrid quasi-resonant soft-switching three-level ANPC single-phase converter, which is used for an inverter or a rectifier. In the single-phase converter, two switch tubes connected to the output end of the bridge arm are and Adopt SiC type switch device, switch tube , , and Adopt Si type switch device, switch tube and Using SiC MOSFET devices, switch tube , , and A Si-type IGBT device is taken as an example for detailed description.

[0020] The single-phase inverter includes: a quasi-resonant soft switching circuit, a switch tube ~ ,diode ~ , input voltage divider capacitors of the same type and ; The quasi-resonant soft switching circuit comprises: a resonant capacitor , resonant inductor , resonant switch tube ; Voltage divider capacitor and Series, voltage-dividing capacitors The non-series termination of the DC bus positive pole, the voltage dividing capacitor The negative pole of the DC bus is connected in series with the voltage divider capacitor and The series common point of the switch tube is connected to the midpoint of the DC bus; ~ Corresponding to the anti-parallel diodes ~ , switch tube The collector of the switch is connected to the positive pole of the DC bus. The emitter of the switch is connected to the negative pole of the DC bus. The emitter of the switch tube The drain and switch The collector connection of the switch tube The collector of the switch tube The source and switch The emitter connection of the switch tube The emitter and switch tube After the collector is connected to the midpoint O of the DC bus, the switch tube The source and switch tube The drains of the capacitors are connected together, and the connection point is used as the output end of the bridge arm; the resonant capacitor Connect in parallel to the switch Between the drain and source, the resonant inductor With resonant switch After connecting in series, connect in parallel to the output filter inductor Both ends, resonant switch tube The drain of the resonant switch is connected to the positive pole of the load. The source is connected to the resonant inductor one end.

[0021] like Figure 2 As shown, it is a switching sequence table of a three-level ANPC converter. In the table, the three levels are: positive level, zero level, and negative level; The positive level corresponds to the switch state P. At this time, the switch tube ~ The switching sequence is (1 1 0 0 0 1); Negative level corresponds to switch state N, at this time the switch tube ~ The switching sequence is (0 0 1 1 1 0); The zero level corresponds to four switching states, namely switch state OU1, switch state OU2, switch state OL1, and switch state OL2; the switching sequence of switch state OU1 is (0 1 0 1 1 0), the switching sequence of switch state OU2 is (0 1 0 01 0), the switching sequence of switch state OL1 is (1 0 1 0 0 1), and the switching sequence of switch state OL2 is (0 0 1 0 01).

[0022] The commutation strategy of the hybrid quasi-resonant soft-switching three-level ANPC converter provided by the embodiment of the present invention is as follows: (1) Positive half cycle of single-phase inverter output voltage In the positive half cycle of the converter output voltage, the converter output has only positive level and zero level.

[0023] At this time, the commutation strategy of the present invention is: the positive level selects the switch state P, and the corresponding switch tube ~ The switching sequence is (1 1 0 0 0 1), the zero level selects the switch state OL1, and the corresponding switch tube ~ The switching sequence is (1 01 0 0 1).

[0024] As shown in Figure 3(a), when the output of the converter is at a positive level, that is, the converter is in the switching state P (the red path in Figure 3(a)), the switch tube , , The other switches are turned off. No current flows; When the output of the converter switches from the positive level to the zero level, that is, the converter switches from the switching state P to the switching state OL1, at this time, the switch tube , Keep conducting, switch After a period of dead time, the switch tube The anti-parallel diode Open, switch tube No current flows; When the output of the converter is zero level, that is, the converter is in the switching state OL1 (the blue path in Figure 3 (a)), the switch tube , , The other switches are turned off. No current flows; When the output of the converter switches from zero level to positive level, that is, the converter switches from switch state OL1 to switch state P, the switch tube , Keep conducting, switch After a period of dead time, the switch tube Open, switch tube No current flows.

[0025] The advantages of the above commutation strategy are: in the positive half cycle of the converter output voltage, each state switching process maintains , Keep conducting, and only the switch tube performs high-frequency switching action , , and the switch tube , SiC switching devices are used, which can fully utilize the advantages of high switching frequency and low loss of SiC switching devices, thereby reducing switching losses in high frequencies.

[0026] (2) Negative half cycle of single-phase inverter output voltage In the negative half cycle of the converter output voltage, the converter output has only negative level and zero level.

[0027] At this time, the commutation strategy of the present invention is: negative level selects switch state N, and the corresponding switch tube ~ The switching sequence is (0 0 1 1 1 0), the zero level selects the switch state OU1, and the corresponding switch tube ~ The switching sequence is (0 10 1 1 0).

[0028] As shown in Figure 3(b), when the output of the converter is at a negative level, that is, the converter is in the switching state N (the purple path in Figure 3(b)), the switch tube , , The other switches are turned off. No current flows; When the output of the converter switches from negative level to zero level, that is, the converter switches from switch state N to switch state OU1, at this time, the switch tube , Keep conducting, switch After a period of dead time, the switch tube The anti-parallel diode Open, switch tube No current flows; When the output of the converter is zero level, that is, the converter is in the switching state OU1 (the green path in Figure 3 (b)), the switch tube , , The other switches are turned off. No current flows; When the output of the converter switches from zero level to negative level, that is, the converter switches from switch state OU1 to switch state N, the switch tube , Keep conducting, switch After a period of dead time, the switch tube Open, switch tube No current flows.

[0029] The advantages of the above commutation strategy are: in the negative half cycle of the converter output voltage, each state switching process maintains , Keep conducting, and only the switch tube performs high-frequency switching action , , and the switch tube , SiC switching devices are used, which can fully utilize the advantages of high switching frequency and low loss of SiC switching devices, thereby reducing switching losses in high frequencies.

[0030] The stress analysis of the switch tube is as follows: (1) Positive half cycle of converter output voltage When the converter is in the switching state P, the switch tube , , On, switch tube , , Turn off; switch The collector is connected to the positive pole of the DC bus, and the emitter is connected to the voltage divider capacitor and The midpoint of the switch tube Withstand voltage ; Switching tube The drain is connected to the positive pole of the DC bus, and the source is connected to the voltage divider capacitor and The midpoint of the switch tube Withstand voltage ; Switching tube The collector of and The midpoint of the switch tube is connected to the negative pole of the DC bus. Withstand voltage .

[0031] When the converter is in the switching state OL1, the switch tube , , On, switch tube , , Turn off; switch The collector is connected to the positive pole of the DC bus, and the emitter is connected to the voltage divider capacitor and The midpoint of the switch tube Withstand voltage ; Switching tube The drain is connected to the positive pole of the DC bus, and the source is connected to the voltage divider capacitor and The midpoint of the switch tube Withstand voltage ; Switching tube The collector of and The midpoint of the switch tube is connected to the negative pole of the DC bus. Withstand voltage ;in, is the DC bus voltage.

[0032] (2) Negative half cycle of converter output voltage When the converter is in the switching state N, the switch tube , , On switch , , Turn off; switch tube The collector of and The midpoint of the switch tube is connected to the negative pole of the DC bus. Withstand voltage ; Switching tube The collector is connected to the positive pole of the DC bus, and the emitter is connected to the voltage divider capacitor and The midpoint of the switch tube Withstand voltage ; Switching tube The drain terminal is connected to a voltage divider capacitor and The midpoint of the switch tube is connected to the negative pole of the DC bus. Withstand voltage ; When the converter is in the switching state OU1, the switch tube , , On, switch tube , , Turn off; switch The emitter is connected to the positive pole of the DC bus and the emitter is connected to the voltage dividing capacitor and The midpoint of the switch tube Withstand voltage ; Switching tube The drain terminal is connected to a voltage divider capacitor and The midpoint of the switch tube is connected to the negative pole of the DC bus. Withstand voltage ; Switching tube The collector of and The midpoint of the switch tube is connected to the negative pole of the DC bus. Withstand voltage ;in, is the DC bus voltage.

[0033] From the above analysis, it can be seen that the voltages borne by all the switched-off switches under the commutation strategy provided by the embodiment of the present invention are the same, namely, , which can improve the quality of the output waveform and extend the life of the device.

[0034] The working principle of the quasi-resonant soft switching circuit is as follows: In the switch tube And switch tube During the dead time of turn-on and turn-off, the resonant capacitor and resonant inductor Connected in series, resonance occurs Achieve zero voltage turn-on and zero voltage turn-off, switch tube The natural zero voltage switching is achieved through the commutation process, and the resonant inductor During pre-charging, the switch is controlled The shutdown achieves zero current shutdown.

[0035] As shown in Figure 5 (a), this is the current loop when OL1 is in a switching cycle in the positive half cycle, corresponding to Figure 4 of In this state, Always turn on the resonant switch , resonant inductor Start charging, where the resonant inductor The smaller the value, the faster the charge can be filled. If the value is large, the current in this path can be considered almost unchanged. When it increases, according to the KCL law, we know Reduce, when When it decreases to 0, ;in Make the resonant switch The current rises slowly when turned on, which can reduce the area where the voltage and current intersect when turned on, and reduce the resonant switch tube By selecting The inductance value makes it at the critical point of overcharge and undercharge. , by regulating the switch The off time of The shutdown within the time period can make Achieve zero current shutdown.

[0036] As shown in Figure 5 (b), the resonant state in a switching cycle in the positive half cycle ( and Dead time) of the current loop, corresponding to Figure 4 of In this state, the resonant switch tube Keep it open when Dead time resonant capacitor after shut down With resonant inductor Forming a resonant circuit, resonant inductor right To charge, When it decreases to 0, the resonant capacitor Reaching the resonance peak, the resonant capacitor right Reverse charging is performed, and the current direction is shown by the blue arrow in Figure 5 (b). The current changes direction and increases in the opposite direction. When the resonant inductor The voltage across the terminals is 0. Reaching the resonance peak, Reverse charging until hour, is clamped to 0, then The voltage across the two ends is , The reverse current begins to decrease, and the switch tube The opening time of Turning on during this period can achieve zero voltage turning on.

[0037] As shown in Figure 5 (c), this is the current loop in the P state in a switching cycle of the positive half cycle, corresponding to Figure 4 of In this state, open After that, After The resonant switch tube Shutdown, can be achieved Zero current shutdown, at To shut down a moment before Activate , resonant inductor Start charging, then When it increases linearly, according to the KCL law, we know Reduce, when When it decreases to 0, ;when , by regulating the switch The off time of The shutdown within the time period can make Zero current shutdown is also achieved.

[0038] As shown in Figure 5 (d), this is the current loop when the natural zero voltage is turned on in a switching cycle in the positive half cycle, corresponding to Figure 4 of Status, in and During the dead time, resonance begins to occur until the resonant capacitor Reaching the resonance peak When the resonant switch Shutdown can almost achieve Zero current shutdown due to the output filter inductor It is considered that the current will not change suddenly, so the switch tube The freewheeling diode The voltage difference between the two ends is approximately 0, and the freewheeling diode In the off state, the output filter inductor Theoretically, The capacitor voltage rises to the freewheeling diode Forward voltage, freewheeling diode Starts to conduct, current starts to flow through the diode, due to The resonant peak has been reached, and the capacitor is quickly filled, which can be regarded as the diode being turned on immediately. This state corresponds to Figure 4 of ,diode After turning on, the switch The voltage across the diode Clamped at 0, by adjusting the switch The turn-on time is short, and zero voltage turn-on can be achieved by turning on during this stage.

[0039] Embodiment 2 like Figure 6 As shown, an embodiment of the present invention provides a hybrid quasi-resonant soft-switching three-level ANPC three-phase converter, in which two switch tubes connected to the output end of the A-phase bridge arm are and Adopt SiC type switch device, switch tube , , and Si type switching devices are used, and the two switching tubes connected to the output end of the B phase bridge arm and Adopt SiC type switch device, switch tube , , and Si type switch devices are used, and the two switch tubes connected to the output end of the C phase bridge arm and Adopt SiC type switch device, switch tube , , and Adopt Si type switching device.

[0040] Switching tube and , and , and Using SiC MOSFET devices, switch tube , , and , switch tube , , and , , , and A Si-type IGBT device is taken as an example for detailed description.

[0041] The three-phase inverter includes: A-phase bridge arm, B-phase bridge arm, C-phase bridge arm, and input voltage-dividing capacitors of the same type. and ; Voltage divider capacitor and Series, voltage-dividing capacitors The non-series termination of the DC bus positive pole, the voltage dividing capacitor The negative pole of the DC bus is connected in series with the voltage divider capacitor and The series common point is connected to the midpoint of the DC bus.

[0042] The A phase bridge arm consists of a switch tube ~ Composition, switch tube ~ Corresponding to the anti-parallel diodes ~ , switch tube The collector of the switch is connected to the positive pole of the DC bus. The emitter of the switch is connected to the negative pole of the DC bus. The emitter of the switch tube The drain and switch The collector connection of the switch tube The collector of the switch tube The source and switch The emitter connection of the switch tube The emitter and switch tube After the collector is connected to the midpoint of the DC bus, the switch tube The source and switch tube The drain electrodes of the A-phase bridge arm are connected together, and the connection point is used as the output end of the A-phase bridge arm; the A-phase bridge arm also includes a quasi-resonant soft switching circuit, and the quasi-resonant soft switching circuit includes: a resonant capacitor , resonant inductor , resonant switch tube ; Among them, the resonant capacitor Connect in parallel to the switch Between the drain and source, the resonant inductor With resonant switch After connecting in series, connect in parallel to the output filter inductor Both ends, resonant switch tube The drain of the resonant switch is connected to the positive pole of the load. The source is connected to the resonant inductor one end.

[0043] The B phase bridge arm consists of a switch tube ~ Composition, switch tube ~ Corresponding to the anti-parallel diodes ~ , switch tube The collector of the switch is connected to the positive pole of the DC bus. The emitter of the switch is connected to the negative pole of the DC bus. The emitter of the switch tube The drain and switch The collector connection of the switch tube The collector of the switch tube The source and switch The emitter connection of the switch tube The emitter and switch tube After the collector is connected to the midpoint of the DC bus, the switch tube The source and switch tube The drain electrodes of the two phases are connected together, and the connection point is used as the output end of the B phase bridge arm; the B phase bridge arm also includes a quasi-resonant soft switching circuit, and the quasi-resonant soft switching circuit includes: a resonant capacitor , resonant inductor , resonant switch tube ; Among them, the resonant capacitor Connect in parallel to the switch Between the drain and source, the resonant inductor With resonant switch After connecting in series, connect in parallel to the output filter inductor Both ends, resonant switch tube The drain of the resonant switch is connected to the positive pole of the load. The source is connected to the resonant inductor one end.

[0044] The C phase bridge arm consists of a switch tube ~ Composition, switch tube ~ Corresponding to the anti-parallel diodes ~ , switch tube The collector of the switch is connected to the positive pole of the DC bus. The emitter of the switch is connected to the negative pole of the DC bus. The emitter of the switch tube The drain and switch The collector connection of the switch tube The collector of the switch tube The source and switch The emitter connection of the switch tube The emitter and switch tube After the collector is connected to the midpoint of the DC bus, the switch tube The source and switch tube The drain electrodes of the two phases are connected together, and the connection point is used as the output end of the C phase bridge arm; the C phase bridge arm also includes a quasi-resonant soft switching circuit, and the quasi-resonant soft switching circuit includes: a resonant capacitor , resonant inductor , resonant switch tube ; Among them, the resonant capacitor Connect in parallel to the switch Between the drain and source, the resonant inductor With resonant switch After connecting in series, connect in parallel to the output filter inductor Both ends, resonant switch tube The drain of the resonant switch is connected to the positive pole of the load. The source is connected to the resonant inductor one end.

[0045] The commutation strategy of the A phase of the hybrid quasi-resonant soft-switching three-level ANPC three-phase converter in the embodiment of the present invention is the same as the commutation strategy of the single-phase converter in the first embodiment, which is as follows: (1) Positive half cycle of the output voltage of phase A bridge arm of the three-phase converter In the positive half cycle of the output voltage of the A-phase bridge arm of the converter, the output of the converter has only positive level and zero level.

[0046] At this time, the commutation strategy of the present invention is: the positive level selects the switch state P, and the corresponding switch tube ~ The switching sequence is (1 1 0 0 0 1), the zero level selects the switch state OL1, and the corresponding switch tube ~ The switching sequence is (1 01 0 0 1).

[0047] (2) Negative half cycle of the output voltage of the A phase bridge arm of the three-phase converter In the negative half cycle of the output voltage of the phase A bridge arm of the converter, the output of the converter only has negative level and zero level.

[0048] At this time, the commutation strategy of the present invention is: negative level selects switch state N, and the corresponding switch tube ~ The switching sequence is (0 0 1 1 1 0), the zero level selects the switch state OU1, and the corresponding switch tube ~ The switching sequence is (0 10 1 1 0).

[0049] The stress analysis of the switch tube is the same as that of the single-phase converter in the first embodiment, and will not be repeated here.

[0050] The quasi-resonant soft switching circuit is in phase A through Parallel resonant capacitor across both ends , in the switch tube And switch tube During the dead time of turn-on and turn-off, the resonant capacitor and resonant inductor Connected in series, resonance occurs Achieve zero voltage turn-on and zero voltage turn-off, switch tube The natural zero voltage switching is achieved through the commutation process. When the resonant inductor is pre-charged, the switch tube is controlled. The shutdown can achieve zero current shutdown. In this quasi-resonant soft switching topology, there is no need to The parallel resonant capacitor at both ends saves cost and enables the two SiC MOSFETs in one phase to achieve zero voltage turn-on and zero current turn-off.

[0051] The operating principle of the quasi-resonant soft switching circuit of the B-phase and C-phase of the hybrid quasi-resonant soft switching three-level ANPC three-phase converter in the embodiment of the present invention is the same as that of the A-phase, which will not be repeated here.

[0052] The commutation strategy for phases B and C of the hybrid quasi-resonant soft-switching three-level ANPC three-phase converter of the embodiment of the present invention is the same as the commutation strategy for phase A, which will not be repeated here.

[0053] Comparative Verification FIG7 (a) is a graph showing the switching loss and conduction loss of the three-level ANPC converter of the present invention and its commutation strategy; FIG7 (b) is a graph showing the switching loss and conduction loss of the three-level ANPC converter composed of four SiC switching devices and two Si-type (referred to as 4-SiC hybrid) switching devices; FIG7 (c) is a graph showing the switching loss and conduction loss of the three-level ANPC converter in which all six switching devices are SiC-type (referred to as full SiC-type) switching devices; FIG7 (d) is a graph showing the switching loss and conduction loss of the three-level ANPC converter in which all six switching devices are Si-type (referred to as full Si-type) switching devices; it can be seen from the figure that the switching loss of the converter of the present invention and the switching loss of the 4-SiC hybrid converter are basically all concentrated on the SiC devices; the switching losses of other types of converters are distributed on the six switching tubes.

[0054] Figures 8 (a) and 8 (b) are comparison diagrams of the total loss distribution of the four single-phase three-level ANPC topologies under their respective optimal modulation strategies when the phase voltage output apparent frequency is high and the power factor is 1 and -1 respectively; Figures 9 (a) and 9 (b) are comparison diagrams of the total loss distribution of the four single-phase three-level ANPC topologies under their respective optimal modulation strategies when the phase voltage output apparent frequency is low and the power factor is 1 and -1 respectively; Considering that the cost of SiC devices is about twice that of Si devices, considering the SiC cost of the three-phase converter, the 6-SiC type saves about 30% of the cost compared with the 12-SiC type converter, and the 6-SiC type saves about 50% of the cost compared with the full SiC type converter. It can be seen from Figures 8 (a) and 8 (b) that at high switching frequency, the total power loss of the three-level ANPC converter of the present invention is basically equal to that of the 4-SiC hybrid three-level ANPC converter, but the loss distribution is more balanced, and the high power loss of the three-level ANPC converter of the present invention is on the two SiC MOSFET devices. Considering the high temperature resistance of SiC devices, it is not necessary to keep the junction temperature of SiC MOSFET and Si IGBT balanced, and uneven power loss is no longer a problem. As can be seen from Figure 9 (a) and Figure 9 (b), at low switching frequencies, the 4-SiC hybrid three-level ANPC converter has no obvious advantages over the converter in the present invention. Although the total power loss of the full SiC three-level ANPC topology is better than that of the 2-SiC type, when a large number of converters are required for large projects, it is more cost-effective to choose the converter of the present invention in combination with cost considerations. Therefore, in order to optimize the balance between performance and cost, the present invention can give full play to the advantages of SiC devices in switching frequency and heat dissipation while minimizing manufacturing costs, thereby improving system power density.

[0055] The topology of the hybrid three-level ANPC converter of the present invention is combined with the commutation strategy to achieve an increase in the output switching frequency of the converter, greatly reduce the switching loss of the converter, make each switch tube bear the same voltage stress under any level state, and improve the stability of the topology. At the same time, by comparing with other types of topologies at present, while ensuring the advantages of SiC and Si hybrid three-level ANPC converter circuits, the cost is controlled to achieve better cost performance; while efficiently exerting the performance of SiC devices, considering that even if the switching loss of SiC switching devices is significantly lower than that of Si devices, SiC devices still have non-negligible switching losses when working in a high frequency state of several hundred or several thousand kHz, a resonant soft switching circuit is designed for SiC devices on the classic ANPC three-level inverter topology, and the SiC devices can simultaneously achieve zero current shutdown and zero voltage opening according to the precise control of the switching time. Through the SiC MOSFET and Si IGBT hybrid three-level ANPC inverter circuit topology based on quasi-resonant soft switching combined with the commutation strategy, the overall circuit output switching frequency is improved, the switching loss of the circuit is greatly reduced, and the voltage stress borne by each switch tube is the same under any power level state, and the stability of the topology is improved. At the same time, by comparing with other types of topologies, the cost of the main switch tube and the resonant circuit is controlled while ensuring the advantages of the SiC and Si hybrid three-level ANPC inverter circuit.

[0056] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A hybrid quasi-resonant soft-switching three-level ANPC single-phase converter, characterized in that: In the single-phase converter, the switch tube connected to the output end of the bridge arm and SiC type switching devices are used, and the remaining switching tubes are Si type switching devices; and in the switching tube and A quasi-resonant soft switching circuit is designed between the switch tubes. and In the switching dead time, the resonant capacitor and inductor in the quasi-resonant soft switching circuit are connected to form a series resonant circuit, making Achieve zero voltage turn-on and zero voltage turn-off. The natural zero voltage switching is achieved through the commutation process. When the resonant inductor is pre-charged, the control Shutdown achieves zero current shutdown.

2. The hybrid quasi-resonant soft-switching three-level ANPC single-phase converter according to claim 1, characterized in that: The quasi-resonant soft switching circuit comprises: a resonant capacitor , resonant inductor , resonant switch tube ; Resonant capacitor Connect in parallel to the switch Between the drain and source, the resonant inductor With resonant switch After connecting in series, connect in parallel to the output filter inductor Both ends, resonant switch tube The drain of the resonant switch is connected to the positive electrode of the load. The source is connected to the resonant inductor one end.

3. The hybrid quasi-resonant soft-switching three-level ANPC single-phase converter according to claim 1, characterized in that: The SiC type switch device adopts a SiC type MOSFET device.

4. The hybrid quasi-resonant soft-switching three-level ANPC single-phase converter according to claim 1, characterized in that: The Si-type switch device adopts a Si-type IGBT device.

5. The hybrid quasi-resonant soft-switching three-level ANPC single-phase converter according to claim 1, characterized in that: Used for inversion.

6. The hybrid quasi-resonant soft-switching three-level ANPC single-phase converter according to claim 1, characterized in that: Used for rectification.

7. A commutation strategy applied to the hybrid quasi-resonant soft-switching three-level ANPC single-phase converter according to any one of claims 1 to 6, characterized in that: The commutation strategy of the positive half cycle of the output voltage of the single-phase converter is: the corresponding switch tube ~ The switching sequence is (1 1 0 0 0 1), and the corresponding switch tube at zero level ~ The switching sequence is (1 0 1 0 0 1); the commutation strategy for the negative half cycle is: the corresponding switch tube at the negative level ~ The switching sequence is (0 0 1 1 1 0), and the corresponding switch tube at zero level ~ The switching sequence is (0 1 0 1 1 0).

8. The commutation strategy according to claim 7, characterized in that: When the output of the three-level ANPC single-phase converter switches from positive level to zero level, the switch tube , Keep conducting, switch After a period of dead time, the switch tube The anti-parallel diode Open, switch tube No current flows.

9. The commutation strategy according to claim 7, characterized in that: When the output of the three-level ANPC single-phase converter switches from zero level to positive level, the switch tube , Keep conducting, switch After a period of dead time, the switch tube Open, switch tube No current flows.

10. The commutation strategy according to claim 7, characterized in that: When the output of the three-level ANPC single-phase converter switches from negative level to zero level, the switch tube , Keep conducting, switch After a period of dead time, the switch tube The anti-parallel diode Open, switch tube No current flows.

11. The commutation strategy according to claim 7, characterized in that: When the output of the three-level ANPC single-phase converter switches from zero level to negative level, the switch tube , Keep conducting, switch After a period of dead time, the switch tube Open, switch tube No current flows.

12. A hybrid quasi-resonant soft-switching three-level ANPC three-phase converter, characterized in that: The three-level ANPC three-phase converter is composed of the hybrid quasi-resonant soft-switching three-level ANPC single-phase converter according to any one of claims 1 to 6.

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