Fault-tolerant device, power conversion device, power supply system, and fault-tolerant method of power conversion circuit

Abstract

The invention provides a fault-tolerant device, power conversion equipment, a power supply system and a fault-tolerant method of a power conversion circuit. The fault-tolerant device is applied to the power conversion circuit, the power conversion circuit comprises a primary side bridge circuit, a transformer and a secondary side bridge circuit, the fault-tolerant device comprises a fault-tolerant protection circuit, and the fault-tolerant protection circuit is connected between the secondary side of the transformer and the secondary side bridge circuit. When the outer tube control signals of the two outer tubes of the secondary side bridge circuit are disconnection control signals at the same time, and / or when the inner tube control signals of the two inner tubes of the secondary side bridge circuit are disconnection control signals at the same time, the fault-tolerant protection circuit is in a closed state, so that secondary side current on the secondary side is subjected to follow current and energy of the secondary side current is absorbed; therefore, the overstress risk of the secondary side switching tube is reduced, and the operation of the power conversion circuit is ensured.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to a fault-tolerant device, a power conversion device, a power supply system, and a fault-tolerant method for a power conversion circuit. Background Art

[0002] In the field of new energy, dual active bridge micro inverters are increasingly widely used due to their small size, low cost, and high efficiency. In practical applications, dual active bridge micro inverters may have control timing errors of the secondary switch tubes due to hardware or software problems under various complex working conditions, resulting in the secondary current not being able to continue normally, causing the risk of stress damage to the secondary switch tubes, and affecting the operation of the dual active bridge micro inverter. Therefore, it is necessary to propose a control fault-tolerant design for dual active bridge micro inverters. Summary of the invention

[0003] In view of the deficiencies in the prior art, the present application provides a fault-tolerant device, a power conversion device, a power supply system and a fault-tolerant method for a power conversion circuit, which can ensure the safety of the secondary side switch tube and the normal operation of the power conversion circuit when the control timing of the secondary side switch tube is wrong.

[0004] The first aspect of the present application provides a fault-tolerant device, which is applied to a power conversion circuit. The power conversion circuit includes a primary bridge circuit, a transformer and a secondary bridge circuit, wherein the first end of the primary bridge circuit is connected to the primary side of the transformer, the second end of the primary bridge circuit is used to connect a DC power supply or a DC load, the first end of the secondary bridge circuit is connected to the secondary side of the transformer, and the second end of the secondary bridge circuit is used to connect an AC load or an AC power supply; wherein the secondary bridge circuit includes a first secondary bridge arm and a second secondary bridge arm connected in series, the first secondary bridge arm includes two bidirectional switches connected in series, both bidirectional switches include an outer tube and an inner tube connected in reverse series, and the second secondary bridge arm includes a first capacitor and a second capacitor connected in series. The fault-tolerant device includes a fault-tolerant protection circuit, which is connected between the secondary side of the transformer and the secondary bridge circuit, wherein when the outer tube control signals of the two outer tubes are disconnection control signals at the same time, and / or when the inner tube control signals of the two inner tubes are disconnection control signals at the same time, the fault-tolerant protection circuit is in a pass state, so that the secondary current on the secondary side continues to flow and absorbs the energy of the secondary current.

[0005] In one embodiment, when the outer tube control signals of the two outer tubes are not disconnection control signals at the same time, and the inner tube control signals of the two inner tubes are not disconnection control signals at the same time, the fault-tolerant protection circuit is in an open circuit state so that the secondary side bridge circuit continues the secondary side current on the secondary side.

[0006] In one embodiment, the fault-tolerant protection circuit is connected between the secondary side of the transformer and the first end of the secondary side bridge circuit, and the fault-tolerant protection circuit includes a connected control switch and an absorption circuit. The fault-tolerant device also includes a controller, the controller is connected to the control switch, and the controller is used to obtain the outer tube control signal and the inner tube control signal of the secondary side bridge circuit, and when the outer tube control signals of the two outer tubes are disconnection control signals at the same time, and / or, when the inner tube control signals of the two inner tubes are disconnection control signals at the same time, control the control switch to close, so that the secondary side current continues to flow through the control switch and the absorption circuit, and the energy of the secondary side current is absorbed by the absorption circuit; and when the outer tube control signals of the two outer tubes are not disconnection control signals at the same time, and the inner tube control signals of the two inner tubes are not disconnection control signals at the same time, control the control switch to open.

[0007] In one embodiment, the number of fault-tolerant protection circuits is two, and both fault-tolerant protection circuits are connected between the secondary side of the transformer and the second end of the secondary side bridge circuit, and are connected in parallel with the two bidirectional switches in a one-to-one correspondence, and each fault-tolerant protection circuit includes a connected control switch and an absorption circuit. The fault-tolerant device also includes a controller, which is connected to the control switches of the two fault-tolerant protection circuits. The controller is used to obtain the outer tube control signal and the inner tube control signal of the secondary side bridge circuit, and when the outer tube control signals of the two outer tubes are disconnection control signals at the same time, and / or when the inner tube control signals of the two inner tubes are disconnection control signals at the same time, the control switches are controlled to be closed, so that the secondary side current continues to flow through the control switch and the absorption circuit, and the energy of the secondary side current is absorbed by the absorption circuit; and when the outer tube control signals of the two outer tubes are not disconnection control signals at the same time, and the inner tube control signals of the two inner tubes are not disconnection control signals at the same time, the control switches are controlled to be opened.

[0008] In one embodiment, the absorption circuit includes an absorption resistor and a buffer capacitor, and the absorption resistor and the buffer capacitor in the same fault-tolerant protection circuit are connected to the control switch.

[0009] In one embodiment, the absorption resistor, buffer capacitor and control switch in the same fault-tolerant protection circuit are connected in series; or, the absorption resistor and buffer capacitor in the same fault-tolerant protection circuit are connected in parallel, and the control switch in the same fault-tolerant protection circuit is connected in series with the parallel-connected absorption resistor and buffer capacitor.

[0010] The second aspect of the present application provides a power conversion device. The power conversion device includes a power conversion circuit and a fault-tolerant protection circuit. The power conversion circuit includes a primary bridge circuit, a transformer and a secondary bridge circuit. The first end of the primary bridge circuit is connected to the primary side of the transformer, and the second end of the primary bridge circuit is used to connect a DC power supply or a DC load. The first end of the secondary bridge circuit is connected to the secondary side of the transformer, and the second end of the secondary bridge circuit is used to connect an AC load or an AC power supply; wherein the secondary bridge circuit includes a first secondary bridge arm and a second secondary bridge arm connected in series, the first secondary bridge arm includes two bidirectional switches connected in series, and the two bidirectional switches both include an outer tube and an inner tube connected in reverse series, and the second secondary bridge arm includes a first capacitor and a second capacitor connected in series. The fault-tolerant protection circuit is connected between the secondary side of the transformer and the secondary bridge circuit, wherein when the outer tube control signals of the two outer tubes are disconnection control signals at the same time, and / or when the inner tube control signals of the two inner tubes are disconnection control signals at the same time, the fault-tolerant protection circuit is in a pass state to continue the secondary current on the secondary side and absorb the energy of the secondary current.

[0011] In one embodiment, when the outer tube control signals of the two outer tubes are not disconnection control signals at the same time, and the inner tube control signals of the two inner tubes are not disconnection control signals at the same time, the fault-tolerant protection circuit is in an open circuit state so that the secondary side bridge circuit continues the secondary side current on the secondary side.

[0012] In one embodiment, the fault-tolerant protection circuit is connected between the secondary side of the transformer and the first end of the secondary side bridge circuit, and the fault-tolerant protection circuit includes a connected control switch and an absorption circuit. The power conversion device also includes a controller, the controller is connected to the control switch, and the controller is used to obtain the external tube control signal and the internal tube control signal of the secondary side bridge circuit, and when the external tube control signals of the two external tubes are disconnection control signals at the same time, and / or, when the internal tube control signals of the two internal tubes are disconnection control signals at the same time, the control switch is controlled to be closed, so that the secondary side current continues to flow through the control switch and the absorption circuit, and the energy of the secondary side current is absorbed by the absorption circuit; and when the external tube control signals of the two external tubes are not disconnection control signals at the same time, and the internal tube control signals of the two internal tubes are not disconnection control signals at the same time, the control switch is controlled to be opened.

[0013] In one embodiment, the number of fault-tolerant protection circuits is two, and the two fault-tolerant protection circuits are both connected between the secondary side of the transformer and the second end of the secondary side bridge circuit, and are connected in parallel with the two bidirectional switches in a one-to-one correspondence, and each fault-tolerant protection circuit includes a connected control switch and an absorption circuit. The power conversion device also includes a controller, the controller is connected to the control switches of the two fault-tolerant protection circuits, the controller is used to obtain the external tube control signal and the internal tube control signal of the secondary side bridge circuit, and when the external tube control signals of the two external tubes are disconnection control signals at the same time, and / or when the internal tube control signals of the two internal tubes are disconnection control signals at the same time, the control switches are all closed, so that the secondary side current continues to flow through the control switch and the absorption circuit, and the energy of the secondary side current is absorbed by the absorption circuit; and when the external tube control signals of the two external tubes are not disconnection control signals at the same time, and the internal tube control signals of the two internal tubes are not disconnection control signals at the same time, the control switches are all opened.

[0014] In one embodiment, the voltage applied to both ends of the outer tube and the voltage applied to both ends of the inner tube are always within a preset safe voltage range.

[0015] In one embodiment, the controller is also connected to the power conversion circuit, and the controller is also used to generate a control signal for the power conversion circuit, wherein the control signal of the power conversion circuit includes a primary control signal, an external tube control signal and an internal tube control signal, the primary control signal is used to control the on-off state of the switching tube in the primary bridge circuit, the external tube control signal is used to control the on-off state of the external tube in the secondary bridge circuit, and the internal tube control signal is used to control the on-off state of the inner tube in the secondary bridge circuit.

[0016] In one embodiment, the primary bridge circuit includes a first primary bridge arm and a second primary bridge arm connected in series, the first primary bridge arm includes a first primary switch tube and a second primary switch tube connected in series, and the second primary bridge arm includes a third primary switch tube and a fourth primary switch tube connected in series.

[0017] A third aspect of the present application provides a power supply system, which includes: a DC power supply and the power conversion device described in the second aspect or any one embodiment of the second aspect, the DC power supply is connected to the second end of the primary bridge circuit, the second end of the secondary bridge circuit is connected to a common coupling point, the DC power supply includes at least one of an energy storage device and a photovoltaic power generation device, and the common coupling point is used to connect at least one of a power grid and an AC load.

[0018] The fourth aspect of the present application provides a fault-tolerant method for a power conversion circuit. The power conversion circuit includes a primary bridge circuit, a transformer, and a secondary bridge circuit, wherein the first end of the primary bridge circuit is connected to the primary side of the transformer, the second end of the primary bridge circuit is used to connect a DC power supply or a DC load, the first end of the secondary bridge circuit is connected to the secondary side of the transformer, the second end of the secondary bridge circuit is used to connect an AC load or an AC power supply, and a fault-tolerant protection circuit is also connected between the secondary side of the transformer and the secondary bridge circuit; wherein the secondary bridge circuit includes a first secondary bridge arm and a second secondary bridge arm connected in series, the first secondary bridge arm includes two bidirectional switches connected in series, the two bidirectional switches each include an outer tube and an inner tube connected in reverse series, and the second secondary bridge arm includes a first capacitor and a second capacitor connected in series. The fault-tolerant method of the power conversion circuit includes: obtaining an outer tube control signal and an inner tube control signal of a secondary side bridge circuit; when the outer tube control signals of two outer tubes are disconnection control signals at the same time, and / or when the inner tube control signals of two inner tubes are disconnection control signals at the same time, controlling a fault-tolerant protection circuit to be in a pass state, so that the fault-tolerant protection circuit continues the secondary side current on the secondary side and absorbs the energy of the secondary side current.

[0019] In one embodiment, the fault-tolerant method further includes: when the outer tube control signals of the two outer tubes are not disconnection control signals at the same time, and the inner tube control signals of the two inner tubes are not disconnection control signals at the same time, controlling the fault-tolerant protection circuit to be in an open circuit state.

[0020] In one embodiment, the fault-tolerant protection circuit is connected between the secondary side of the transformer and the first end of the secondary side bridge circuit, and the fault-tolerant protection circuit includes a connected control switch and an absorption circuit. Correspondingly, when the outer tube control signals of the two outer tubes are disconnection control signals at the same time, and / or, when the inner tube control signals of the two inner tubes are disconnection control signals at the same time, the fault-tolerant protection circuit is controlled to be in a pass state, so that the fault-tolerant protection circuit continues to flow the secondary current on the secondary side and absorbs the energy of the secondary current. The process includes: when the outer tube control signals of the two outer tubes are disconnection control signals at the same time, and / or, when the inner tube control signals of the two inner tubes are disconnection control signals at the same time, the control switch is controlled to be closed, so that the secondary current continues to flow through the control switch and the absorption circuit, and the energy of the secondary current is absorbed by the absorption circuit. Correspondingly, when the outer tube control signals of the two outer tubes are not disconnect control signals at the same time, and the inner tube control signals of the two inner tubes are not disconnect control signals at the same time, the process of controlling the fault-tolerant protection circuit to be in an open circuit state includes: when the outer tube control signals of the two outer tubes are not disconnect control signals at the same time, and the inner tube control signals of the two inner tubes are not disconnect control signals at the same time, the control switch is controlled to open.

[0021] In one embodiment, the number of fault-tolerant protection circuits is two, and both fault-tolerant protection circuits are connected between the secondary side of the transformer and the second end of the secondary side bridge circuit, and are connected in parallel with two bidirectional switches in a one-to-one correspondence, and each fault-tolerant protection circuit includes a connected control switch and an absorption circuit. Correspondingly, when the outer tube control signals of the two outer tubes are disconnection control signals at the same time, and / or, when the inner tube control signals of the two inner tubes are disconnection control signals at the same time, the fault-tolerant protection circuit is controlled to be in a pass state, so that the fault-tolerant protection circuit continues to flow for the secondary side current and absorbs the energy of the secondary side current. The process includes: when the outer tube control signals of the two outer tubes are disconnection control signals at the same time, and / or, when the inner tube control signals of the two inner tubes are disconnection control signals at the same time, the control switches are controlled to be closed, so that the secondary side current continues to flow through the control switch and the absorption circuit, and the energy of the secondary side current is absorbed by the absorption circuit. Correspondingly, when the outer tube control signals of the two outer tubes are not disconnect control signals at the same time, and the inner tube control signals of the two inner tubes are not disconnect control signals at the same time, the process of controlling the fault-tolerant protection circuit to be in an open circuit state includes: when the outer tube control signals of the two outer tubes are not disconnect control signals at the same time, and the inner tube control signals of the two inner tubes are not disconnect control signals at the same time, the control switches are both turned on.

[0022] In one embodiment, the fault-tolerant method further includes: when the outer tube control signals of the two outer tubes are at the first level at the same time, determining that the outer tube control signals of the two outer tubes are disconnection control signals at the same time. When the outer tube control signals of the two outer tubes are at the second level at the same time, or one of the outer tube control signals is at the first level and the other outer tube control signal is at the second level, determining that the outer tube control signals of the two outer tubes are not disconnection control signals at the same time. When the inner tube control signals of the two inner tubes are at the first level at the same time, determining that the inner tube control signals of the two inner tubes are at the same time disconnection control signals. When the inner tube control signals of the two inner tubes are at the second level at the same time, or one of the inner tube control signals is at the first level and the other inner tube control signal is at the second level, determining that the inner tube control signals of the two inner tubes are not disconnection control signals at the same time. Wherein, the first level is different from the second level, the first level is used to drive the switch tube to disconnect, and the second level is used to drive the switch tube to turn on.

[0023] Compared with the prior art, this application has at least the following advantages: 1. This application adds a fault-tolerant device to the power conversion circuit. When the secondary control signal mistakenly drives both outer tubes to disconnect, and / or the secondary control signal mistakenly drives both inner tubes to disconnect, the fault-tolerant protection circuit in the fault-tolerant device can be in a pass state, so that the secondary current can continue to flow through the fault-tolerant protection circuit. Therefore, even if a control timing error occurs, the power conversion circuit will not have the problem of overstress damage to the outer tube caused by the parasitic capacitance of the secondary switch tube continuing to flow and boosting. Therefore, this application can achieve fault-tolerant protection of the secondary switch tube and the power conversion circuit, and ensure the operation of the power conversion circuit.

[0024] 2. The fault-tolerant device of the present application can ensure that the secondary current continues to flow when the secondary control signal is erroneous, and can also ensure that the normal flow of the secondary current and the normal operation of the secondary bridge circuit are not affected when the secondary control signal is normal.

[0025] 3. The present application is applicable to the case where the secondary control signal drives both outer tubes to disconnect due to an error, or the secondary control signal drives both inner tubes to disconnect due to an error, or the secondary control signal drives both inner tubes and both outer tubes to disconnect due to an error. That is to say, the present application can be applicable to a variety of control timing errors. Therefore, the present application has a wide range of applications. Moreover, the present application directly controls the fault-tolerant protection circuit without changing the original control logic of the outer tube and the inner tube. Therefore, the control is simple, and the control complexity of the outer tube and the inner tube will not be increased, and the control logic confusion is not likely to occur.

[0026] 4. The fault-tolerant protection circuit of the present application is a hardware protection circuit, and the fault-tolerant protection of the power conversion circuit is more reliable and stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of a power supply system provided in an embodiment of the present application.

[0028] Figure 2 yes Figure 1 Schematic diagram of the connection between the power conversion circuit and the fault-tolerant device.

[0029] Figure 3 yes Figure 1 A circuit diagram of a power conversion circuit in FIG.

[0030] Figure 4 yes Figure 3 A working waveform diagram of the power conversion circuit shown when it operates normally.

[0031] Figure 5 In the case where the fault-tolerant device of the embodiment of the present application is not provided, Figure 3 The shown diagram is a flow diagram of the secondary side current when the control timing of the power conversion circuit is wrong.

[0032] Figure 6 In the case where the fault-tolerant device of the embodiment of the present application is not provided, Figure 3 Another flow diagram of the secondary current in the power conversion circuit shown in FIG. 1 when a control timing error occurs.

[0033] Figure 7 In the case where the fault-tolerant device of the embodiment of the present application is not provided, Figure 3 The power conversion circuit shown is a waveform diagram of the voltage stress borne by the secondary side switch tube when the control timing is wrong.

[0034] Figure 8 yes Figure 7 A partial enlarged view of the portion near a zero crossing point of the waveform shown.

[0035] Fig. 9 This is a circuit diagram of a power conversion circuit and a fault-tolerant protection circuit provided in the first embodiment.

[0036] Fig.10 yes Fig. 9 A flow diagram of the secondary side current of the power conversion circuit shown.

[0037] Fig.11 yes Fig. 9 Another flow diagram of the secondary side current of the power conversion circuit shown.

[0038] Fig.12 yes Fig. 9 A waveform diagram of the voltage stress borne by the secondary side switch tube of the power conversion circuit shown.

[0039] Fig.13 yes Fig.12 A partial enlarged view of the portion near a zero crossing point of the waveform shown.

[0040] Fig.14 This is a circuit diagram of a power conversion circuit and a fault-tolerant protection circuit provided in the second embodiment.

[0041] Fig.15 yes Fig.14 A flow diagram of the secondary side current of the power conversion circuit shown.

[0042] Fig.16 yes Fig.14 Another flow diagram of the secondary side current of the power conversion circuit shown.

[0043] Fig.17 yes Fig.14 A waveform diagram of the voltage stress borne by the secondary side switch tube of the power conversion circuit shown.

[0044] Fig.18 yes Fig.17 A partial enlarged view of the portion near a zero crossing point of the waveform shown.

[0045] Fig.19 It is a flow chart of a fault-tolerant method for a power conversion circuit provided in an embodiment of the present application.

[0046] Main component symbols 100-power supply system, 10-DC power supply, 11-energy storage equipment, 12-photovoltaic power generation equipment, 20-power conversion equipment, 21-power conversion circuit, 211-primary bridge circuit, 2111-first primary bridge arm, 2112-second primary bridge arm, 212-transformer, 213-resonant inductor, 214-secondary bridge circuit, 2141-first secondary bridge arm, 2142-second secondary bridge arm, 22-fault-tolerant device, 23, 23A, 23B-fault-tolerant protection circuit, 24-controller, 30- point of common coupling, 40- grid, 50- AC load. DETAILED DESCRIPTION

[0047] In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only embodiments of a part of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present application. In the absence of conflict, the following different embodiments and features in the embodiments can be combined with each other.

[0048] See also Figure 1 , showing a topological diagram of a power supply system 100 provided in an embodiment of the present application.

[0049] like Figure 1 As shown, the power supply system 100 includes a DC power supply 10 and a power conversion device 20. For the convenience of description, the DC power supply 10 is an energy storage device 11 and a photovoltaic power generation device 12. At this time, the power supply system 100 can also be called a photovoltaic storage and charging system.

[0050] It should be understood that in other scenarios, only the photovoltaic power generation device 12 or the energy storage device 11 may be used as the DC power source 10, or other devices that can provide DC power may be used as the DC power source 10. In the scenario where only the photovoltaic power generation device 12 is used as the DC power source 10, the power supply system 100 may also be called a photovoltaic system, and in the scenario where only the energy storage device 11 is used as the DC power source 10, the power supply system 100 may also be called an energy storage system or a storage and charging system.

[0051] The power conversion device 20 is a single-stage micro inverter. The power conversion device 20 includes a power conversion circuit 21. One end of the power conversion circuit 21 is connected to the energy storage device 11 and the photovoltaic power generation device 12. The energy storage device 11 includes a rechargeable energy storage battery. The other end of the power conversion circuit 21 is connected to a common coupling point 30 (abbreviated as PCC). The common coupling point 30 can be used to connect the power grid 40 and the AC load 50.

[0052] In the embodiments of this application, please refer to Figure 2 The power conversion circuit 21 includes a primary bridge circuit 211, a transformer 212, and a secondary bridge circuit 214, wherein the primary bridge circuit 211 may adopt a full-bridge structure or a half-bridge structure, and the secondary bridge circuit 214 adopts a half-bridge structure. Therefore, the power conversion circuit 21 may also be called a dual active bridge (DAB) conversion circuit.

[0053] For the convenience of description, the embodiments of the present application are described as follows. Figure 3 The primary bridge circuit 211 shown is a full-bridge structure, and the secondary bridge circuit 214 is a half-bridge structure for exemplary description.

[0054] like Figure 3 As shown, the primary bridge circuit 211 includes a first primary bridge arm 2111 and a second primary bridge arm 2112 connected in parallel, the first primary bridge arm 2111 includes a first primary switch tube Q1 and a second primary switch tube Q2 connected in series, and the second primary bridge arm 2112 includes a third primary switch tube Q3 and a fourth primary switch tube Q4 connected in series. The midpoint of the first primary bridge arm 2111 and the midpoint of the second primary bridge arm 2112 together constitute the first end of the primary bridge circuit 211, and the first end of the primary bridge circuit 211 is connected to the primary side of the transformer 212. The two ends of the first primary bridge arm 2111 and the two ends of the second primary bridge arm 2112 constitute the second end of the primary bridge circuit 211. The second end of the primary bridge circuit 211 can be connected to the capacitor Cdc, and can be used to connect the DC power supply 10 or the DC load.

[0055] The secondary bridge circuit 214 includes a first secondary bridge arm 2141 and a second secondary bridge arm 2142 connected in parallel. The first secondary bridge arm 2141 includes two bidirectional switches in series, namely, a first bidirectional switch and a second bidirectional switch, wherein the first bidirectional switch includes two secondary switch tubes Q5 and Q6 connected in reverse series, and the second bidirectional switch includes two secondary switch tubes Q7 and Q8 connected in reverse series. Among them, Q6 and Q7 are located between Q5 and Q8, Q5 can also be called the first outer tube, Q8 can also be called the second outer tube, Q6 can also be called the first inner tube, and Q7 can also be called the second inner tube. The second secondary bridge arm 2142 includes a first capacitor Cr1 and a second capacitor Cr2 connected in series. The midpoint of the first secondary bridge arm 2141 and the midpoint of the second secondary bridge arm 2142 together constitute the first end of the secondary bridge circuit 214, and the first end of the secondary bridge circuit 214 is connected to the secondary side of the transformer 212.

[0056] Among them, the switch tubes Q1~Q8 can use corresponding types of semiconductor switch devices according to actual needs. For the convenience of description, Figure 3 In the example, the switch tubes Q1~Q8 are all MOSFET. The turns ratio between the secondary side and the primary side of the transformer 212 is n:1, n>1. The transformer 212 has a secondary leakage inductance, which can be independent of the transformer 212 and is located between the midpoint of the first secondary bridge arm 2141 and the secondary side of the transformer 212. The secondary leakage inductance can be used as a resonant inductor 213. For ease of description, Figure 3 The resonant inductor 213 (corresponding to Figure 3 In some embodiments, the resonant inductor Lr can constitute a resonant circuit alone. In some other embodiments, the resonant inductor Lr, the first capacitor Cr1 and the second capacitor Cr2 can constitute a resonant circuit together.

[0057] The two ends of the first secondary bridge arm 2141 and the two ends of the second secondary bridge arm 2142 constitute the second end of the secondary bridge circuit 214. The second end of the secondary bridge circuit 214 can be used to connect to the common coupling point 30, thereby connecting to the AC power supply or the AC load 50. A filter or filtering circuit can be provided between the second end of the secondary bridge circuit 214 and the common coupling point 30, for example Figure 3 The filter inductor Lf in.

[0058] Based on such a design, when the power supply system 100 is working, the energy storage device 11 can be used as a DC power source 10, and the power conversion circuit 21 can transmit the power provided by the energy storage device 11 to the AC load 50 and / or the power grid 40. When the power conversion circuit 21 feeds power to the power grid 40, the power grid 40 can be regarded as an AC load 50. Conversely, the energy storage device 11 can also be used as a DC load, and the power grid 40 can be used as an AC power source. The power conversion circuit 21 can transmit the power provided by the power grid 40 to the energy storage device 11 to charge the energy storage device 11.

[0059] In the embodiment of the present application, the process of transmitting power from the primary bridge circuit 211 to the secondary bridge circuit 214 can be referred to as the forward operation process of the power conversion circuit 21, and the process of transmitting power from the secondary bridge circuit 214 to the primary bridge circuit 211 can be referred to as the reverse operation process of the power conversion circuit 21. In other embodiments, the forward and reverse directions can also be reversed, which is not specifically limited here.

[0060] The primary bridge circuit 211 constitutes a DC / AC conversion circuit, and the secondary bridge circuit 214 constitutes an AC / AC conversion circuit. The voltage at the second end of the primary bridge circuit 211 is a DC voltage Vdc, the voltage at the second end of the secondary bridge circuit 214 is an AC voltage Vac, and the current at the second end of the secondary bridge circuit 214 is an AC current iac.

[0061] The transformer 212 is used to isolate and couple the primary bridge circuit 211 and the secondary bridge circuit 214. The resonant circuit is used to store and transmit energy. The voltage on the primary side of the transformer 212 can be called the primary voltage Vp. The primary voltage Vp is the voltage generated on the first end of the primary bridge circuit 211, or the voltage between the midpoint of the first primary bridge arm 2111 and the midpoint of the second primary bridge arm 2112 of the primary bridge circuit 211. The current on the secondary side of the transformer 212 can be called the secondary current is. The secondary current is is also the inductor current flowing through the resonant inductor Lr. The voltage generated on the secondary side of the transformer 212 can be called the secondary voltage Vs. The secondary voltage Vs is the voltage on the first end of the secondary bridge circuit 214, or the voltage between the midpoint of the first secondary bridge arm 2141 and the midpoint of the second secondary bridge arm 2142 of the secondary bridge circuit 214.

[0062] The control end of the switch tube Q1~Q8 is used to receive a control signal, and the control signal is used to control the on-off state of the switch tube Q1~Q8. When the control signal of the switch tube is a first level, the control signal is a conduction control signal, which can be used to drive the switch tube to conduct; when the control signal of the switch tube is a second level, the control signal is a disconnection control signal, which can be used to drive the switch tube to turn off. Among them, the first level is different from the second level. For the convenience of description, the embodiment of the present application is described by taking the first level as a low level (for example, 0) and the second level as a high level (for example, 1) as an example.

[0063] In the embodiment of the present application, the control signal of the first primary switch tube Q1 is S1, the control signal of the second primary switch tube Q2 is S2, the control signal of the third primary switch tube Q3 is S2, and the control signal of the fourth primary switch tube Q4 is S4. The control signal of the first outer tube Q5 is S5, the control signal of the first inner tube Q6 is S6, the control signal of the second inner tube Q7 is S7, and the control signal of the second outer tube Q8 is S8. For the convenience of description, S1~S4 can all be called primary control signals, S5~S8 can all be called secondary control signals, and further, the control signal S6 of the first inner tube Q6 and the control signal S7 of the second inner tube Q7 can both be called inner tube control signals, and the control signal S5 of the first outer tube Q5 and the control signal S8 of the second outer tube Q8 can both be called outer tube control signals.

[0064] Under normal circumstances, for the primary bridge circuit 211, under the control of the control signals S1 and S2, the first primary switch tube Q1 and the second primary switch tube Q2 are alternately turned on at high frequency; under the control of the control signals S3 and S4, the third primary switch tube Q3 and the fourth primary switch tube Q4 are alternately turned on at high frequency.

[0065] Under normal circumstances, for the secondary bridge circuit 214, please refer to Figure 4 , the secondary switch tube switches state at the zero crossing point of the AC voltage Vac. Among them, when the real-time AC voltage Vac is positive, under the control of the control signals S5 and S7, the first outer tube Q5 and the second inner tube Q7 are alternately turned on at high frequency; under the control of the control signals S6 and S8, the first inner tube Q6 and the second outer tube Q8 are always on. To avoid the first secondary bridge arm being directly turned on, the control signals S5 and S7 have a dead time. During this dead time, the first outer tube Q5 and the second inner tube Q7 are both turned off. When the real-time AC voltage Vac is negative, under the control of the control signals S6 and S8, the first inner tube Q6 and the second outer tube Q8 are alternately turned on at high frequency; under the control of the control signals S5 and S7, the first outer tube Q5 and the second inner tube Q7 are always on. To avoid the first secondary bridge arm being directly turned on, the control signals S6 and S8 have a dead time. During this dead time, the first inner tube Q6 and the second outer tube Q8 are both turned off.

[0066] However, in actual applications, the power conversion device 20 may have control timing errors of the secondary side switch tube due to hardware or software problems under various complex working conditions. For example, Q5~Q8 are all incorrectly switched to the disconnected state; or, Q6 and Q7 are turned on and off normally, but the switching timing of Q5 and Q8 is incorrect, resulting in both being in the disconnected state; or, Q5 and Q8 are turned on and off normally, but the switching timing of Q6 and Q7 is incorrect, resulting in both being in the disconnected state.

[0067] like Figure 5 As shown by the black bold line (arrow indicates the current flow direction), when Q6 and Q7 are disconnected at the same time, if the secondary current is flows into the first end of the secondary bridge circuit at this time (for the convenience of description, this flow direction can be referred to as the forward flow of the secondary current is), the secondary current is cannot flow normally, that is, the secondary current is cannot flow through the channel and body diode of the first inner tube Q6, nor can it flow through the channel and body diode of the second inner tube Q7, and can only flow through the parasitic capacitance of the first inner tube Q6 and the parasitic capacitance of the second inner tube Q7. At this time, the parasitic capacitor is in a charging state, and the parasitic capacitor voltage increases. Since the parasitic capacitor voltage is applied to both ends of the switch tube, if the secondary current is is too large and the parasitic capacitor flow time is too long, the parasitic capacitor voltage will be too large, causing Q6 and Q7 to be subjected to excessive voltage stress.

[0068] Similarly, if Figure 6 As shown by the black bold line (arrow indicates the current flow direction), when Q5 and Q8 are disconnected at the same time, if the secondary current is flows in from the second end of the secondary bridge circuit at this time (for the convenience of description, this flow direction can be referred to as the reverse flow of the secondary current is), the secondary current is cannot flow normally, that is, the secondary current is cannot flow through the channel and body diode of the first outer tube Q5, nor can it flow through the channel and body diode of the second outer tube Q8, and can only flow through the parasitic capacitance of the first outer tube Q5 and the parasitic capacitance of the second outer tube Q8. At this time, the parasitic capacitor is in a charging state, and the parasitic capacitor voltage increases. If the secondary current is is too large and the parasitic capacitor continues to flow for too long, the parasitic capacitor voltage will be too large, causing Q5 and Q8 to be subjected to excessive voltage stress.

[0069] by Figure 7 and Figure 8 Take the simulation signal waveform shown as an example. Figure 7 In the Figure 3 The waveform diagram of the voltage borne by both ends of Q5-Q8, i.e., the voltage stress waveform diagram of Q5-Q8, occurs when a control timing error occurs during the operation of the power conversion circuit 21, such as both Q5 and Q8 are disconnected, and / or both Q6 and Q7 are disconnected. Figure 8 Shown Figure 7 The waveform shown is a partial enlarged view of the part near the zero-crossing point within the elliptical dotted frame. Figure 7 and Figure 8It can be seen that when Q5 and Q8 are switched to the disconnected state, a large spike will appear in the waveform near the voltage zero point, and the spike voltage is about 150V~200V, indicating that the voltage stress of Q5 and Q8 near the voltage zero point reaches about 150V~200V. Similarly, when Q6 and Q7 are switched to the disconnected state, the waveform also has a spike of about 150V~200V near the voltage zero point, indicating that the voltage stress of Q6 and Q7 near the voltage zero point reaches about 150V~200V. Figure 7 It can be seen that when Q5~Q8 are all turned off, the stress of Q5 is as high as about 800V, and the stress of Q6, Q7, and Q8 are all as high as 500V or exceed 500V.

[0070] It is understandable that excessive voltage stress may cause overstress damage to the secondary switch tube, thus affecting the operation of the power conversion circuit 21. Figure 1 and Figure 2 The embodiment of the present application proposes a fault-tolerant device 22, which can be applied to the power conversion circuit 21 to ensure that the secondary current can continue to flow when a control timing error occurs in the secondary side switch tube of the power conversion circuit 21, thereby realizing fault-tolerant protection for the secondary side switch tube and the power conversion circuit 21.

[0071] Specifically, if Figure 1 As shown, the fault-tolerant device 22 can be arranged in the power conversion device 20. The fault-tolerant device 22 includes a fault-tolerant protection circuit 23 and a controller 24. Figure 2 As shown, the fault-tolerant protection circuit 23 is connected between the secondary side of the transformer 212 and the secondary side bridge circuit 214. The controller 24 is connected to the power conversion circuit 21 and the fault-tolerant protection circuit 23.

[0072] Furthermore, the fault-tolerant protection circuit 23 includes a control switch and an absorption circuit. The control switch can be any kind of electrically controlled switch, and the electrically controlled switch can be, for example, a relay, a contactor, a semiconductor switch, or a combination thereof, etc., which is not specifically limited here. The absorption circuit can include a resistor for energy consumption and a capacitor for energy storage, etc. The control switch is connected to the absorption circuit. When the power conversion circuit is running, when the control switch is turned on, the fault-tolerant protection circuit 23 is in a conductive state, and when the control switch is turned off, the fault-tolerant protection circuit 23 is in an open circuit state.

[0073] The controller 24 may be a microcontroller unit (MCU), a digital signal processor (DSP) or other control elements or circuits. The controller 24 may be connected to the control terminals of the switch tubes Q1 to Q8 in the power conversion circuit 21, and may be used to modulate and generate control signals of the switch tubes Q1 to Q8 and output the control signals to the switch tubes Q1 to Q8 to control the on / off states of the switch tubes Q1 to Q8, thereby controlling the working conditions of the power conversion circuit 21.

[0074] The controller 24 may be used to connect the control switch in the fault-tolerant protection circuit 23 , and to output a control signal of the control switch to the control switch to control the on / off state of the control switch, thereby controlling the connectivity of the fault-tolerant protection circuit 23 .

[0075] Among them, when a control timing error occurs and the outer tube control signals of the two outer tubes are simultaneously disconnected control signals, or the inner tube control signals of the two inner tubes are simultaneously disconnected control signals, or the outer tube control signals of the two outer tubes are simultaneously disconnected control signals and the inner tube control signals of the two inner tubes are simultaneously disconnected control signals, the controller 24 can be used to control the control switch in the fault-tolerant protection circuit 23 to be turned on, so that the fault-tolerant protection circuit 23 is in a conductive state.

[0076] It can be understood that when the external tube control signals S5 and S8 are both disconnection control signals, the external tubes Q5 and Q8 are both disconnected. Figure 6 According to the description, the reverse-flowing secondary current is can only be continued through the parasitic capacitance of the outer tube Q5 and the parasitic capacitance of the outer tube Q8, resulting in large voltage stress of Q5 and Q8 and high risk of stress damage. At this time, the controller 24 of the embodiment of the present application actively controls the fault-tolerant protection circuit 23 to be turned on, so that the secondary side of the transformer 212 is connected to the secondary side bridge circuit 214 through the turned-on fault-tolerant protection circuit 23, and then, the secondary current is flowing in the forward or reverse direction can flow to the fault-tolerant protection circuit 23, that is, continue to flow through the fault-tolerant protection circuit 23, thereby reducing the current flowing to the parasitic capacitance of the outer tubes Q5 and Q8, and suppressing the continued flow and voltage boost of the parasitic capacitance of Q5 and Q8, so the overstress risk of Q5 and Q8 can be reduced. At the same time, the absorption circuit in the fault-tolerant protection circuit 23 can also absorb the energy of the secondary current is during the continued flow, further reducing the overstress risk of Q5 and Q8.

[0077] Similarly, when the inner tube control signals S6 and S7 are both disconnect control signals, the inner tubes Q6 and Q7 are both disconnected. Figure 5According to the description, the secondary current is flowing in the forward direction can only be continued through the parasitic capacitance of the inner tube Q6 and the parasitic capacitance of the inner tube Q7, resulting in large voltage stress of Q6 and Q7 and high risk of stress damage. At this time, the controller 24 of the embodiment of the present application actively controls the fault-tolerant protection circuit 23 to be turned on, so that the secondary side of the transformer 212 is connected to the secondary side bridge circuit 214 through the turned-on fault-tolerant protection circuit 23, and then, the secondary current is flowing in the forward direction or reverse direction can flow to the fault-tolerant protection circuit 23, that is, continue to flow through the fault-tolerant protection circuit 23, thereby reducing the current flowing to the parasitic capacitance of the inner tubes Q6 and Q7, and suppressing the continuous flow and voltage boost of the parasitic capacitance of Q6 and Q7, so the overstress risk of Q6 and Q7 can be reduced. At the same time, the absorption circuit in the fault-tolerant protection circuit 23 can also absorb the energy of the secondary current is during continuous flow, further reducing the overstress risk of Q6 and Q7.

[0078] It can be seen that based on the fault-tolerant device 22 of the embodiment of the present application, in the case of a secondary side switch tube control timing error, no matter whether the secondary side current is flows in the forward direction or the reverse direction, the fault-tolerant protection circuit 23 can continue the secondary side current is, suppress the parasitic capacitance from continuing the current and boosting the voltage, and thus reduce the voltage stress of the secondary side switch tube, preventing the secondary side switch tube from being damaged by overstress, thereby ensuring the operation of the power conversion circuit 21.

[0079] Therefore, the fault-tolerant device 20 can prevent the power conversion circuit 21 from being damaged by overstress on the secondary switch tube due to the inability of the secondary current to continue flowing due to control timing errors, thereby achieving fault-tolerant protection for the secondary switch tube and the power conversion circuit 21.

[0080] In addition, under normal circumstances, the external tubes Q5 and Q8 are alternately turned on at high frequencies and Q6 and Q8 are always turned on, or Q6 and Q8 are alternately turned on at high frequencies and Q5 and Q8 are always turned on, therefore, under normal control timing, the control timing of the external tubes Q5 and Q8 may be: the external tube control signals of the two external tubes are simultaneously turned on control signals, or one of the external tube control signals is a disconnection control signal and the other external tube control signal is a turn-on control signal. In these cases, Q5 and Q8 are not disconnected at the same time, and at least one external tube is turned on, so the secondary current is flowing in the reverse direction can still flow normally through the channel of the turned-on external tube, and there will be no problem of overstress damage to the external tube caused by the continuous current boost of the parasitic capacitance of Q5 and Q8, which affects the operation of the power conversion circuit 21.

[0081] Similarly, under normal control timing, the control timing of the inner tubes Q6 and Q7 may be: the inner tube control signals of the two inner tubes are both on control signals, or one of the inner tube control signals is a disconnection control signal and the other inner tube control signal is an on control signal. In these cases, Q6 and Q7 are not disconnected at the same time, and at least one inner tube is turned on. Therefore, the secondary current is flowing in the forward direction can still flow normally through the channel of the turned-on outer tube, and there will be no problem of overstress damage to the outer tube caused by the freewheeling boost of the parasitic capacitance of Q6 and Q7, which affects the operation of the power conversion circuit 21.

[0082] That is to say, under the above circumstances, the power conversion circuit 21 can operate normally. Therefore, the fault-tolerant device 22 of the embodiment of the present application will not interfere with the continuous flow of the secondary current. That is, when the outer tube control signals of the two outer tubes are not disconnection control signals at the same time, and the inner tube control signals of the two inner tubes are not disconnection control signals at the same time, the controller 24 can be used to control the control switch in the fault-tolerant protection circuit 23 to be disconnected, so that the fault-tolerant protection circuit 23 is in an open circuit state, and the secondary current on the secondary side is continuous through the secondary side bridge circuit 214.

[0083] It can be seen that the power conversion device 20 of the embodiment of the present application can not only enable the fault-tolerant device 22 to continue the secondary current is when the control timing error affects the normal operation of the secondary bridge circuit 214, so as to achieve fault-tolerant protection for the secondary switch tube and ensure that the secondary bridge circuit 214 can continue to operate, but also disable the fault-tolerant device 22 when the control timing of the secondary bridge circuit 214 is normal, so as to avoid affecting the secondary bridge circuit 214 to continue the secondary current is, thereby affecting the power conversion of the power conversion circuit 21. In this way, regardless of whether the control timing is wrong or correct, the power conversion device 20 can always continue the secondary current is, based on which, the voltage applied to both ends of the outer tube and the voltage applied to both ends of the inner tube can always be maintained within the preset safe voltage (for example, about 90% of the withstand voltage value of the switch tube), ensuring that the secondary bridge circuit 214 can continue to operate normally. Moreover, compared with the fault-tolerant protection implemented by pure software, the fault-tolerant device 22 belongs to hardware fault-tolerant protection, and the fault-tolerant protection of the power conversion circuit 21 is more reliable and stable.

[0084] It should be understood that in other embodiments, the controller 24 in the fault-tolerant device 22 may also be independently provided, or integrated with other circuits / modules / devices. In other embodiments, the fault-tolerant protection circuit 23 and the power conversion circuit 21 may also be controlled by different controllers 24, respectively.

[0085] For better understanding, the fault-tolerant device 22 of the embodiment of the present application is further described below in combination with Embodiments 1 and 2.

[0086] Embodiment 1 See also Fig. 9 , shows a circuit diagram of the fault-tolerant protection circuit 23 in the fault-tolerant device 22 of the first embodiment connected to the power conversion circuit 21. To simplify the schematic, Fig. 9 Controller 24 is not shown.

[0087] like Fig. 9 As shown, the fault-tolerant protection circuit 23 is connected between the secondary side of the transformer 212 and the first end of the secondary side bridge circuit 214, and specifically can be connected between the secondary side of the transformer 212 and the midpoint of the first secondary side bridge arm 2141, or between the secondary side of the transformer 212 and the inner tube Q6 of the first bidirectional switch. The secondary side leakage inductance Lr of the transformer 212 of this embodiment is also located between the midpoint of the first secondary side bridge arm 2141 and the secondary side of the transformer 212, and the fault-tolerant protection circuit 23 at this time can be connected in parallel with the secondary side leakage inductance Lr.

[0088] The fault-tolerant protection circuit 23 includes a control switch Ks and an absorption circuit. The control switch Ks is connected to the controller 24, and its switch state is controlled by the controller 24. The absorption circuit includes an absorption resistor Rs and a buffer capacitor Cs, and the absorption resistor Rs and the buffer capacitor Cs are connected to the control switch Ks.

[0089] In the first embodiment, the absorption resistor Rs, the control switch Ks and the buffer capacitor Cs are connected in series in sequence. It should be understood that in other embodiments, the specific positions and connection relationships of the absorption resistor Rs, the control switch Ks and the buffer capacitor Cs can be adjusted accordingly according to actual conditions, and are not limited to the positions and connection relationships shown in the first embodiment.

[0090] Based on such a structural design, when the outer tube control signals of the two outer tubes Q5 and Q8 are disconnection control signals at the same time, and / or when the inner tube control signals of the two inner tubes Q6 and Q7 are disconnection control signals at the same time, the controller 24 can control the control switch Ks to close to turn on the fault-tolerant protection circuit 23.

[0091] At this time, if Fig.10 As shown by the black bold line (arrow indicates the current flow direction), if the secondary current is flows in the forward direction, the fault-tolerant protection circuit 23 can form a freewheeling branch, so that the secondary current is can flow to the fault-tolerant protection circuit 23. Fig.11As shown by the black bold line (arrow indicates the current flow direction), if the secondary current is flows in the reverse direction, the fault-tolerant protection circuit 23 can also constitute a freewheeling branch, so that the secondary current is can flow to the fault-tolerant protection circuit. Among them, the energy of the current flowing through the buffer capacitor Cs will first be stored in the buffer capacitor Cs, and then released to the absorption resistor Rs, and the energy of the current flowing through the absorption resistor Rs will be consumed by the absorption resistor Rs. In other words, the buffer capacitor Cs can buffer the energy of the secondary current is, and the absorption resistor Rs can absorb the energy of the secondary current is, thereby reducing the voltage stress of the secondary switch tube and protecting the secondary switch tube.

[0092] When the outer tube control signals of the two outer tubes Q5 and Q8 are not disconnection control signals at the same time, and the inner tube control signals of the two inner tubes Q6 and Q7 are not disconnection control signals at the same time, the controller 24 can control the control switch Ks to open to disconnect the fault-tolerant protection circuit 23.

[0093] In addition, the controller 24 controls the operation of the primary bridge circuit 211 while controlling the operation of the secondary bridge circuit 214. Therefore, the controller 24 of this embodiment can also control the first primary switch tube Q1 and the second primary switch tube Q2 to be turned on alternately, and control the third primary switch tube Q3 and the fourth primary switch tube Q4 to be turned on alternately.

[0094] It should be understood that in other embodiments, if the primary bridge circuit 211 of the power conversion circuit 21 is a primary half-bridge circuit, that is, Figure 3 When some of the primary switching tubes in the primary full-bridge circuit are replaced with capacitors, the primary switching tubes in the primary half-bridge circuit are switched on and off according to the on-off logic of the same primary switching tubes in the primary full-bridge circuit, so they will not be repeated here.

[0095] In addition, in order to verify the effect of reducing the stress of the secondary-side switch tube in the first embodiment, the embodiment of the present application also conducted a simulation experiment on the power conversion device 20.

[0096] See also Fig.12 and Fig.13 The simulation signal waveform shown in the figure, Fig.12 Shown in Fig. 9 The waveform diagram of the voltage borne by both ends of Q5 to Q8, i.e., the voltage stress waveform diagram of Q5 to Q8, when a control timing error occurs during the operation of the power conversion circuit 21, in which both Q5 and Q8 are disconnected, and / or both Q6 and Q7 are disconnected; Fig.13 Shown Fig.12 A local enlarged view of the portion of the waveform near the zero-crossing point within the elliptical dotted frame.

[0097] Understandably, Fig.12 The corresponding simulation experiments and Figure 7 The experimental conditions of the corresponding simulation experiments remain the same, the difference is Figure 7 In the corresponding experiment, the power conversion device 20 is not provided with the fault-tolerant device 22 of the first embodiment. Fig.12 In the corresponding experiment, the power conversion device 20 is provided with the fault-tolerant device 22 shown in the first embodiment, and the fault-tolerant device 22 provides fault-tolerant protection.

[0098] from Fig.12 It can be seen that when Q5 and Q8 are switched to the disconnected state, the voltage stress waveforms of Q5 and Q8 can still transition roughly smoothly near the voltage zero point. When Q6 and Q7 are switched to the disconnected state, the voltage stress waveforms of Q6 and Q7 can also transition roughly smoothly near the voltage zero point. Fig.13 It can be seen that the voltage stress of Q5, Q8, Q6 and Q7 near the voltage zero crossing point is less than 25V, which is significantly smaller than Figure 8 When Q5 to Q8 are all turned off, since the fault-tolerant protection circuit 23 of the embodiment of the present application can be turned on, the voltage stress of Q5 to Q8 is still significantly less than Figure 7 The stress shown, for example, is less than 400V for Q5, Q6, and Q7, and less than 200V for Q8.

[0099] It can be seen that based on the fault-tolerant device 22 of embodiment one, it is possible to reduce the voltage stress of the secondary side switch tubes Q5~Q8 when there is an error in the control timing of the secondary side switch tube, so that the voltage stress of Q5~Q8 (that is, the voltage applied to both ends of Q5~Q8) is always within the preset safe voltage range, thereby ensuring the safety of the secondary side switch tube and the normal operation of the power conversion circuit 21.

[0100] Embodiment 2 See also Fig.14 , shows a circuit diagram of the fault-tolerant protection circuit 23 in the fault-tolerant device 22 of the second embodiment connected to the power conversion circuit 21. To simplify the schematic, Fig.14 Controller 24 is not shown.

[0101] The difference between the second embodiment and the first embodiment mainly lies in the number and position connection relationship of the fault-tolerant protection circuits 23 .

[0102] Specifically, Fig.14As shown, the number of fault-tolerant protection circuits 23 of the second embodiment is two, namely, a first fault-tolerant protection circuit 23A and a second fault-tolerant protection circuit 23B. The structures and component parameters of the two fault-tolerant protection circuits 23 are the same. Both fault-tolerant protection circuits 23 are connected between the secondary side of the transformer 212 and the second end of the secondary side bridge circuit 214, and the two fault-tolerant protection circuits 23 are connected in parallel with the two bidirectional switches in a one-to-one correspondence, for example, the first fault-tolerant protection circuit 23A is connected in parallel with the first bidirectional switch, and the second fault-tolerant protection circuit 23B is connected in parallel with the second bidirectional switch.

[0103] The first fault-tolerant protection circuit 23A includes a control switch Ks1 and an absorption circuit, and the second fault-tolerant protection circuit 23B includes a control switch Ks2 and an absorption circuit. The control switch Ks1 and the control switch Ks2 are respectively connected to the controller 24, and their switch states are controlled by the controller 24. In this embodiment, the switch states of the control switch Ks1 and the control switch Ks2 are the same. The absorption circuit in the first fault-tolerant protection circuit 23A includes an absorption resistor Rs1 and a buffer capacitor Cs1, and the absorption resistor Rs1 and the buffer capacitor Cs1 are connected to the control switch Ks1. The absorption circuit in the second fault-tolerant protection circuit 23B includes an absorption resistor Rs2 and a buffer capacitor Cs2, and the absorption resistor Rs1 and the buffer capacitor Cs1 are connected to the control switch Ks1, and the absorption resistor Rs2 and the buffer capacitor Cs2 are connected to the control switch Ks2.

[0104] In the second embodiment, the absorption resistor Rs1 is connected in parallel with the buffer capacitor Cs1, the control switch Ks1 is connected in series with the absorption resistor Rs1 and the buffer capacitor Cs1 after the parallel connection, and is also connected to the midpoint of the first secondary bridge arm, the absorption resistor Rs2 is connected in parallel with the buffer capacitor Cs2, and the control switch Ks2 is connected in series with the absorption resistor Rs2 and the buffer capacitor Cs2 after the parallel connection, and is also connected to the midpoint of the first secondary bridge arm. It should be understood that in other embodiments, the specific positions and connection relationships of the absorption resistor, control switch and buffer capacitor of the same fault-tolerant protection circuit 23 can be adjusted accordingly according to actual conditions, and are not limited to the positions and connection relationships shown in the second embodiment.

[0105] Based on such a structural design, when the outer tube control signals of the two outer tubes Q5 and Q8 are disconnection control signals at the same time, and / or when the inner tube control signals of the two inner tubes Q6 and Q7 are disconnection control signals at the same time, the controller 24 can control the control switches Ks1 and Ks2 to be closed to turn on the fault-tolerant protection circuits 23A and 23B.

[0106] At this time, if Fig.15As shown by the black bold line (arrow indicates the current flow direction), if the secondary current is flows in the forward direction, the fault-tolerant protection circuit 23A can form a freewheeling branch, and the fault-tolerant protection circuit 23B can form another freewheeling branch, so that the secondary current is can flow to the fault-tolerant protection circuits 23A and 23B. Fig.16 As shown by the black bold line (arrow indicates the current flow direction), if the secondary current is flows in the reverse direction, the fault-tolerant protection circuits 23A and 23B can also form two freewheeling branches, so that the secondary current is can flow to the fault-tolerant protection circuits 23A and 23B. Among them, the buffer capacitors Cs1 and Cs2 can buffer the energy of the secondary current is, and the absorption resistors Rs1 and Rs2 can absorb the energy of the secondary current is, thereby reducing the voltage stress of the secondary switch tube and protecting the secondary switch tube.

[0107] When the outer tube control signals of the two outer tubes Q5 and Q8 are not disconnection control signals at the same time, and the inner tube control signals of the two inner tubes Q6 and Q7 are not disconnection control signals at the same time, the controller 24 can control the control switches Ks1 and Ks2 to open to disconnect the fault-tolerant protection circuits 23A and 23B.

[0108] In addition, in order to verify the effect of reducing the stress of the secondary-side switch tube in the second embodiment, the embodiment of the present application also conducts a simulation experiment on the power conversion device 20.

[0109] See also Fig.17 and Fig.18 The simulation signal waveform shown in the figure, Fig.17 Shown in Fig.14 The waveform diagram of the voltage borne by both ends of Q5 to Q8, i.e., the voltage stress waveform diagram of Q5 to Q8, when a control timing error occurs during the operation of the power conversion circuit 21, in which both Q5 and Q8 are disconnected, and / or both Q6 and Q7 are disconnected; Fig.18 Shown Fig.17 A local enlarged view of the portion of the waveform near the zero-crossing point within the elliptical dotted frame.

[0110] Understandably, Fig.17 The corresponding simulation experiments and Figure 7 The experimental conditions of the corresponding simulation experiments remain the same, the difference is Figure 7 In the corresponding experiment, the power conversion device 20 is not provided with the fault-tolerant device 22 shown in the second embodiment. Fig.17 In the corresponding experiment, the power conversion device 20 is provided with the fault-tolerant device 22 shown in the second embodiment, and the fault-tolerant device 22 provides fault-tolerant protection.

[0111] from Fig.17It can be seen that when Q5 and Q8 are switched to the disconnected state, the voltage stress waveforms of Q5 and Q8 can still smoothly transition near the voltage zero point. When Q6 and Q7 are switched to the disconnected state, the voltage stress waveforms of Q6 and Q7 can also smoothly transition near the voltage zero point. Fig.18 It can be seen that the voltage stress of Q5, Q8, Q6 and Q7 near the voltage zero crossing point is less than 2.5V, which is almost 0, which is significantly smaller than Figure 8 When Q5 to Q8 are all turned off, since the fault-tolerant protection circuit 23 of the embodiment of the present application can be turned on, the voltage stress of Q5 to Q8 is still significantly less than Figure 7 The stress shown, for example, the stress of Q5 and Q6 is 0, and the stress of Q7 and Q8 is less than 150V.

[0112] It can be seen that based on the fault-tolerant device 22 of Example 2, it is possible to reduce the voltage stress of the secondary side switch tubes Q5~Q8 when the secondary side switch tube control timing error occurs, so that the voltage stress of Q5~Q8 (that is, the voltage applied to both ends of Q5~Q8) is always within the preset safety voltage range, thereby ensuring the safety of the secondary side switch tube and the normal operation of the power conversion circuit 21.

[0113] It should be understood that other descriptions of the second embodiment can also refer to the first embodiment and will not be repeated here.

[0114] In addition, based on Figure 1 In the scenario shown, the embodiment of the present application also provides a fault-tolerant method for a power conversion circuit. The fault-tolerant method can be executed by the controller 24 in the fault-tolerant device 22, and can implement fault-tolerant protection of the secondary switch tube and the power conversion circuit 21 through the fault-tolerant protection circuit 23 when the secondary switch tube of the power conversion circuit 21 has a timing error in controlling the timing. It should be understood that in other embodiments, the fault-tolerant method can also be executed by other modules or devices with control functions, which can be selected according to actual conditions, and are not specifically limited here.

[0115] Specifically, see Fig.19 The fault-tolerant method of the power conversion circuit of the embodiment of the present application comprises the following steps: Step S100: obtaining an outer tube control signal and an inner tube control signal of a secondary bridge circuit.

[0116] It can be understood that the control signals S1 to S8 of the power conversion circuit 21 can all be generated by the modulation circuit. The modulation circuit can be integrated into the controller 24 or independently provided. Therefore, in step S100, the controller 24 can obtain the outer tube control signal S5 of the outer tube Q5, the outer tube control signal S8 of the outer tube Q8, the inner tube control signal S6 of the inner tube Q6, and the inner tube control signal S7 of the inner tube Q7 from the modulation circuit.

[0117] Step S200, when the outer tube control signals of the two outer tubes are disconnection control signals at the same time, and / or when the inner tube control signals of the two inner tubes are disconnection control signals at the same time, control the fault-tolerant protection circuit to be in a conduction state, so that the fault-tolerant protection circuit continues the secondary current on the secondary side and absorbs the energy of the secondary current.

[0118] For example, in the first embodiment, the fault-tolerant device 22 is provided with a fault-tolerant protection circuit 23, and the fault-tolerant protection circuit 23 includes a connected control switch Ks and an absorption circuit. Therefore, step S200 may be specifically as follows: When the outer tube control signals of the two outer tubes are disconnection control signals at the same time, and / or when the inner tube control signals of the two inner tubes are disconnection control signals at the same time, the control switch Ks is controlled to be closed, so that the secondary current continues to flow through the control switch Ks and the absorption circuit, and the energy of the secondary current is absorbed by the absorption circuit.

[0119] As another example, in the second embodiment, the fault-tolerant device 22 is provided with two fault-tolerant protection circuits, namely 23A and 23B, wherein the fault-tolerant protection circuit 23A includes a connected control switch Ks1 and an absorption circuit, and the fault-tolerant protection circuit 23B includes a connected control switch Ks2 and an absorption circuit. Therefore, step S200 may be specifically as follows: When the outer tube control signals of the two outer tubes are disconnection control signals at the same time, and / or when the inner tube control signals of the two inner tubes are disconnection control signals at the same time, the control switches Ks1 and Ks2 are both closed, so that the secondary current continues to flow through the control switch Ks1 and the absorption circuit connected to it, and continues to flow through the control switch Ks2 and the absorption circuit connected to it, and the energy of the secondary current is absorbed by the two absorption circuits.

[0120] In the embodiment of the present application, the first level is used to drive the switch tube to turn off, and the second level is used to drive the switch tube to turn on. Therefore, before step S20, the fault tolerance method may also include: When the external tube control signals S5 and S8 of the external tubes Q5 and Q8 are at the first level at the same time, it is determined that the external tube control signals S5 and S8 of the two external tubes are disconnection control signals at the same time.

[0121] When the inner tube control signals S6 and S7 of the inner tubes Q6 and Q7 are at the first level at the same time, it is determined that the inner tube control signals S6 and S7 of the two inner tubes are disconnection control signals at the same time.

[0122] On the contrary, when the external tube control signals S5 and S8 of the external tubes Q5 and Q8 are both at the second level, or when one of the external tube control signals is at the first level and the other external tube control signal is at the second level, for example, S5 is at the first level and S8 is at the second level, or for example, S8 is at the first level and S5 is at the second level, it is determined that the external tube control signals S5 and S8 of the two external tubes are not disconnection control signals at the same time.

[0123] When the inner tube control signals S6 and S7 of the inner tubes Q6 and Q7 are both at the second level, or when one of the inner tube control signals is at the first level and the other inner tube control signal is at the second level, for example, S6 is at the first level and S7 is at the second level, or for example, S7 is at the first level and S6 is at the second level, it is determined that the inner tube control signals S6 and S7 of the two inner tubes are not disconnection control signals at the same time.

[0124] To summarize, based on the method of the embodiment of the present application, in the case of a secondary side switch tube control timing error, regardless of whether the secondary side current is flows in the forward direction or the reverse direction, the fault-tolerant protection circuit 23 can continue the flow of the secondary side current is, suppress the parasitic capacitance from continuing the flow and boosting the voltage, and thus reduce the voltage stress of the secondary side switch tube, preventing the secondary side switch tube from being damaged by overstress, thereby ensuring the operation of the power conversion circuit 21.

[0125] In addition, under normal control timing, the reverse-flowing secondary current is can still flow normally through the channel of the turned-on external tube, and the problem of overstress damage to the external tube caused by the continuous current boost of the parasitic capacitance of Q5 and Q8 will not occur, which affects the operation of the circuit. Similarly, under normal control timing, the forward-flowing secondary current is can still flow normally through the channel of the turned-on external tube, and the problem of overstress damage to the external tube caused by the continuous current boost of the parasitic capacitance of Q6 and Q7 will not occur, which affects the operation of the circuit. Therefore, please continue to refer to Fig. 9 The fault tolerance method of the embodiment of the present application may also include the following steps: Step S300: When the outer tube control signals of the two outer tubes are not disconnection control signals at the same time, and the inner tube control signals of the two inner tubes are not disconnection control signals at the same time, the fault-tolerant protection circuit is controlled to be in an open circuit state.

[0126] That is to say, when S5 and S8 are both at the second level, or when S5 is at the second level and S8 is at the first level, or when S8 is at the second level and S5 is at the first level, the controller 24 controls the fault-tolerant protection circuit 23 to disconnect, so that the secondary side of the transformer 212 and the secondary side bridge circuit 214 cannot be connected through the fault-tolerant protection circuit 23, and then, the secondary side current is flowing in the forward direction or the reverse direction flows to the first secondary side bridge arm 2141, that is, it continues to flow normally through the secondary side bridge circuit 214.

[0127] For example, in the first embodiment, step S200 may be specifically as follows: When the outer tube control signals of the two outer tubes are not disconnection control signals at the same time, and the inner tube control signals of the two inner tubes are not disconnection control signals at the same time, the control switch Ks is controlled to be opened.

[0128] For example, in the second embodiment, step S200 may be specifically as follows: When the outer tube control signals of the two outer tubes are not disconnection control signals at the same time, and the inner tube control signals of the two inner tubes are not disconnection control signals at the same time, the control switches Ks1 and Ks2 are both turned on.

[0129] It should be understood that “step S200” and “step S300” are only used to distinguish two different situations, and are not intended to limit the execution order.

[0130] In addition, based on Figure 3 The power conversion circuit 21 shown, the fault-tolerant method of the embodiment of the present application further includes the step of controlling the operation of the primary bridge circuit 211, which can be specifically: The first primary switch tube Q1 and the second primary switch tube Q2 are controlled to be alternately turned on, and the third primary switch tube Q3 and the fourth primary switch tube Q4 are controlled to be alternately turned on.

[0131] In general, in the embodiment of the present application, when the control timing of the power conversion circuit 21 is wrong and affects the normal operation of the secondary bridge circuit 214, the fault-tolerant protection circuit 23 can be used to continue the flow of the secondary current is, thereby realizing fault-tolerant protection of the secondary switch tube, thereby ensuring that the secondary bridge circuit 214 can continue to operate. In addition, when the control timing of the secondary bridge circuit 214 is normal, the secondary bridge circuit 214 can be ensured to continue the flow of the secondary current is normally, thereby avoiding the fault-tolerant protection circuit 23 from affecting the flow of the secondary bridge circuit 214, thereby avoiding affecting the power conversion of the power conversion circuit 21. Therefore, regardless of whether the control timing is wrong or correct, the power conversion device 20 can always continue the flow of the secondary current is, so that the voltage applied to both ends of the outer tube and the voltage applied to both ends of the inner tube can always be maintained within the preset safe voltage range, ensuring that the power conversion circuit 21 can continue to operate normally.

[0132] Moreover, the fault-tolerant protection and fault-tolerant method proposed in the embodiment of the present application can be implemented by hardware structure, which is more reliable and has higher control efficiency than relying on pure software program implementation. The fault-tolerant method proposed in the embodiment of the present application does not need to change the original control logic of the outer tube and the inner tube, so the control is simple, does not increase the control complexity of the outer tube and the inner tube, and is not prone to control logic confusion.

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present application and are not intended to limit it. Although the present application has been described in detail with reference to the preferred embodiments, a person of ordinary skill in the art should understand that the technical solution of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present application.

Claims

1. A fault-tolerant device, characterized in that: Applied to a power conversion circuit, the power conversion circuit includes a primary bridge circuit, a transformer and a secondary bridge circuit, the first end of the primary bridge circuit is connected to the primary side of the transformer, the second end of the primary bridge circuit is used to connect a DC power supply or a DC load, the first end of the secondary bridge circuit is connected to the secondary side of the transformer, and the second end of the secondary bridge circuit is used to connect an AC load or an AC power supply; wherein the secondary bridge circuit includes a first secondary bridge arm and a second secondary bridge arm connected in series, the first secondary bridge arm includes two bidirectional switches connected in series, the two bidirectional switches each include an outer tube and an inner tube connected in reverse series, and the second secondary bridge arm includes a first capacitor and a second capacitor connected in series; The fault-tolerant device comprises a fault-tolerant protection circuit, and the fault-tolerant protection circuit is connected between the secondary side of the transformer and the secondary side bridge circuit, wherein: When the outer tube control signals of the two outer tubes are disconnection control signals at the same time, and / or when the inner tube control signals of the two inner tubes are disconnection control signals at the same time, the fault-tolerant protection circuit is in a conduction state to continue the secondary current on the secondary side and absorb the energy of the secondary current.

2. The fault-tolerant device according to claim 1, characterized in that: When the outer tube control signals of the two outer tubes are not disconnection control signals at the same time, and the inner tube control signals of the two inner tubes are not disconnection control signals at the same time, the fault-tolerant protection circuit is in an open circuit state, so that the secondary side bridge circuit continues the secondary side current on the secondary side.

3. The fault-tolerant device according to claim 1, characterized in that: The fault-tolerant protection circuit is connected between the secondary side of the transformer and the first end of the secondary side bridge circuit, and the fault-tolerant protection circuit includes a connected control switch and an absorption circuit; The fault-tolerant device further includes a controller, the controller is connected to the control switch, the controller is used to obtain the outer tube control signal and the inner tube control signal of the secondary bridge circuit, and when the outer tube control signals of the two outer tubes are disconnection control signals at the same time, and / or when the inner tube control signals of the two inner tubes are disconnection control signals at the same time, control the control switch to close, so that the secondary current continues to flow through the control switch and the absorption circuit, and the energy of the secondary current is absorbed by the absorption circuit; and, When the outer tube control signals of the two outer tubes are not disconnection control signals at the same time, and the inner tube control signals of the two inner tubes are not disconnection control signals at the same time, the control switch is controlled to be opened.

4. The fault-tolerant device according to claim 1, characterized in that: The number of the fault-tolerant protection circuits is two, and the two fault-tolerant protection circuits are both connected between the secondary side of the transformer and the second end of the secondary side bridge circuit, and are connected in parallel with the two bidirectional switches in a one-to-one correspondence, and each of the fault-tolerant protection circuits includes a connected control switch and an absorption circuit; The fault-tolerant device further includes a controller, the controller is connected to the control switches of the two fault-tolerant protection circuits, the controller is used to obtain the outer tube control signal and the inner tube control signal of the secondary bridge circuit, and when the outer tube control signals of the two outer tubes are disconnection control signals at the same time, and / or when the inner tube control signals of the two inner tubes are disconnection control signals at the same time, control the control switches to be closed, so that the secondary current continues to flow through the control switch and the absorption circuit, and the energy of the secondary current is absorbed by the absorption circuit; and, When the outer tube control signals of the two outer tubes are not disconnection control signals at the same time, and the inner tube control signals of the two inner tubes are not disconnection control signals at the same time, the control switches are controlled to be opened.

5. The fault-tolerant device according to claim 3 or 4, characterized in that: The absorption circuit includes an absorption resistor and a buffer capacitor. The absorption resistor and the buffer capacitor in the same fault-tolerant protection circuit are connected to the control switch.

6. The fault-tolerant device according to claim 5, characterized in that: The absorption resistor, the buffer capacitor and the control switch in the same fault-tolerant protection circuit are connected in series; or, The absorption resistor in the same fault-tolerant protection circuit is connected in parallel with the buffer capacitor, and the control switch in the same fault-tolerant protection circuit is connected in series with the parallel-connected absorption resistor and the buffer capacitor.

7. A power conversion device, characterized in that: The power conversion device comprises a power conversion circuit and a fault-tolerant protection circuit, wherein the power conversion circuit comprises a primary bridge circuit, a transformer and a secondary bridge circuit, wherein the first end of the primary bridge circuit is connected to the primary side of the transformer, the second end of the primary bridge circuit is used to connect a DC power supply or a DC load, the first end of the secondary bridge circuit is connected to the secondary side of the transformer, and the second end of the secondary bridge circuit is used to connect an AC load or an AC power supply; wherein the secondary bridge circuit comprises a first secondary bridge arm and a second secondary bridge arm connected in series, wherein the first secondary bridge arm comprises two bidirectional switches connected in series, both of the two bidirectional switches comprise an outer tube and an inner tube connected in reverse series, and the second secondary bridge arm comprises a first capacitor and a second capacitor connected in series; The fault-tolerant protection circuit is connected between the secondary side of the transformer and the secondary side bridge circuit, wherein: When the outer tube control signals of the two outer tubes are disconnection control signals at the same time, and / or when the inner tube control signals of the two inner tubes are disconnection control signals at the same time, the fault-tolerant protection circuit is in a conduction state to continue the secondary current on the secondary side and absorb the energy of the secondary current.

8. The power conversion device according to claim 7, characterized in that When the outer tube control signals of the two outer tubes are not disconnection control signals at the same time, and the inner tube control signals of the two inner tubes are not disconnection control signals at the same time, the fault-tolerant protection circuit is in an open circuit state, so that the secondary side bridge circuit continues the secondary side current on the secondary side.

9. The power conversion device according to claim 7, characterized in that: The fault-tolerant protection circuit is connected between the secondary side of the transformer and the first end of the secondary side bridge circuit, and the fault-tolerant protection circuit includes a connected control switch and an absorption circuit; The power conversion device further includes a controller, the controller is connected to the control switch, the controller is used to obtain the outer tube control signal and the inner tube control signal of the secondary bridge circuit, and when the outer tube control signals of the two outer tubes are disconnection control signals at the same time, and / or when the inner tube control signals of the two inner tubes are disconnection control signals at the same time, control the control switch to close, so that the secondary current continues to flow through the control switch and the absorption circuit, and the energy of the secondary current is absorbed by the absorption circuit; and, When the outer tube control signals of the two outer tubes are not disconnection control signals at the same time, and the inner tube control signals of the two inner tubes are not disconnection control signals at the same time, the control switch is controlled to be opened.

10. The power conversion device according to claim 7, characterized in that The number of the fault-tolerant protection circuits is two, and the two fault-tolerant protection circuits are both connected between the secondary side of the transformer and the second end of the secondary side bridge circuit, and are connected in parallel with the two bidirectional switches in a one-to-one correspondence, and each of the fault-tolerant protection circuits includes a connected control switch and an absorption circuit; The power conversion device further includes a controller, the controller is connected to the control switches of the two fault-tolerant protection circuits, the controller is used to obtain the outer tube control signal and the inner tube control signal of the secondary bridge circuit, and when the outer tube control signals of the two outer tubes are disconnection control signals at the same time, and / or when the inner tube control signals of the two inner tubes are disconnection control signals at the same time, control the control switches to be closed, so that the secondary current continues to flow through the control switch and the absorption circuit, and the energy of the secondary current is absorbed by the absorption circuit; and, When the outer tube control signals of the two outer tubes are not disconnection control signals at the same time, and the inner tube control signals of the two inner tubes are not disconnection control signals at the same time, the control switches are controlled to be opened.

11. The power conversion device according to claim 7, characterized in that The voltage applied to both ends of the outer tube and the voltage applied to both ends of the inner tube are always within a preset safe voltage range.

12. The power conversion device according to claim 7, characterized in that The power conversion device also includes a controller, which is connected to the power conversion circuit and is used to generate a control signal for the power conversion circuit, wherein the control signal for the power conversion circuit includes a primary control signal, an external tube control signal and an internal tube control signal, the primary control signal is used to control the on-off state of the switch tube in the primary bridge circuit, the external tube control signal is used to control the on-off state of the external tube in the secondary bridge circuit, and the internal tube control signal is used to control the on-off state of the inner tube in the secondary bridge circuit.

13. The power conversion device according to claim 7, characterized in that The primary bridge circuit includes a first primary bridge arm and a second primary bridge arm connected in series, the first primary bridge arm includes a first primary switch tube and a second primary switch tube connected in series, and the second primary bridge arm includes a third primary switch tube and a fourth primary switch tube connected in series.

14. A power supply system, characterized in that: The power supply system comprises: a DC power supply and a power conversion device as described in any one of claims 7 to 13, the DC power supply is connected to the second end of the primary bridge circuit, the second end of the secondary bridge circuit is connected to a common coupling point, the DC power supply comprises at least one of an energy storage device and a photovoltaic power generation device, and the common coupling point is used to connect at least one of a power grid and an AC load.

15. A fault-tolerant method for a power conversion circuit, characterized in that: The power conversion circuit includes a primary bridge circuit, a transformer and a secondary bridge circuit, wherein the first end of the primary bridge circuit is connected to the primary side of the transformer, the second end of the primary bridge circuit is used to connect a DC power supply or a DC load, the first end of the secondary bridge circuit is connected to the secondary side of the transformer, the second end of the secondary bridge circuit is used to connect an AC load or an AC power supply, and a fault-tolerant protection circuit is also connected between the secondary side of the transformer and the secondary bridge circuit; wherein the secondary bridge circuit includes a first secondary bridge arm and a second secondary bridge arm connected in series, the first secondary bridge arm includes two bidirectional switches connected in series, the two bidirectional switches each include an outer tube and an inner tube connected in reverse series, and the second secondary bridge arm includes a first capacitor and a second capacitor connected in series; the fault-tolerant method includes: Obtaining an outer tube control signal and an inner tube control signal of the secondary side bridge circuit; When the outer tube control signals of the two outer tubes are disconnection control signals at the same time, and / or when the inner tube control signals of the two inner tubes are disconnection control signals at the same time, the fault-tolerant protection circuit is controlled to be in a conduction state so that the fault-tolerant protection circuit continues the secondary current on the secondary side and absorbs the energy of the secondary current.

16. The fault-tolerant method according to claim 15, characterized in that: The fault-tolerant method further comprises: When the outer tube control signals of the two outer tubes are not disconnection control signals at the same time, and the inner tube control signals of the two inner tubes are not disconnection control signals at the same time, the fault-tolerant protection circuit is controlled to be in an open circuit state.

17. The fault-tolerant method according to claim 15 or 16, characterized in that: The fault-tolerant protection circuit is connected between the secondary side of the transformer and the first end of the secondary side bridge circuit, and the fault-tolerant protection circuit includes a connected control switch and an absorption circuit; When the outer tube control signals of the two outer tubes are disconnection control signals at the same time, and / or when the inner tube control signals of the two inner tubes are disconnection control signals at the same time, controlling the fault-tolerant protection circuit to be in a pass state so that the fault-tolerant protection circuit continues the secondary current on the secondary side and absorbs the energy of the secondary current, comprising: When the outer tube control signals of the two outer tubes are disconnection control signals at the same time, and / or when the inner tube control signals of the two inner tubes are disconnection control signals at the same time, the control switch is controlled to be closed, so that the secondary current continues to flow through the control switch and the absorption circuit, and the energy of the secondary current is absorbed by the absorption circuit; When the outer tube control signals of the two outer tubes are not disconnection control signals at the same time, and the inner tube control signals of the two inner tubes are not disconnection control signals at the same time, controlling the fault-tolerant protection circuit to be in an open circuit state includes: When the outer tube control signals of the two outer tubes are not disconnection control signals at the same time, and the inner tube control signals of the two inner tubes are not disconnection control signals at the same time, the control switch is controlled to be opened.

18. The fault-tolerant method according to claim 15 or 16, characterized in that: The number of the fault-tolerant protection circuits is two, and the two fault-tolerant protection circuits are both connected between the secondary side of the transformer and the second end of the secondary side bridge circuit, and are connected in parallel with the two bidirectional switches in a one-to-one correspondence, and each of the fault-tolerant protection circuits includes a connected control switch and an absorption circuit; When the outer tube control signals of the two outer tubes are disconnection control signals at the same time, and / or when the inner tube control signals of the two inner tubes are disconnection control signals at the same time, controlling the fault-tolerant protection circuit to be in a pass state so that the fault-tolerant protection circuit continues the secondary current on the secondary side and absorbs the energy of the secondary current, comprising: When the outer tube control signals of the two outer tubes are disconnection control signals at the same time, and / or when the inner tube control signals of the two inner tubes are disconnection control signals at the same time, the control switches are controlled to be closed, so that the secondary current continues to flow through the control switch and the absorption circuit, and the energy of the secondary current is absorbed by the absorption circuit; When the outer tube control signals of the two outer tubes are not disconnection control signals at the same time, and the inner tube control signals of the two inner tubes are not disconnection control signals at the same time, controlling the fault-tolerant protection circuit to be in an open circuit state includes: When the outer tube control signals of the two outer tubes are not disconnection control signals at the same time, and the inner tube control signals of the two inner tubes are not disconnection control signals at the same time, the control switches are controlled to be opened.

19. The fault-tolerant method according to claim 15 or 16, characterized in that: The fault-tolerant method further comprises: When the external tube control signals of the two external tubes are at the first level at the same time, determining that the external tube control signals of the two external tubes are disconnection control signals at the same time; When the external tube control signals of the two external tubes are at the second level at the same time, or when one of the external tube control signals is at the first level and the other external tube control signal is at the second level, determining that the external tube control signals of the two external tubes are not disconnection control signals at the same time; When the inner tube control signals of the two inner tubes are at the first level at the same time, determining that the inner tube control signals of the two inner tubes are disconnection control signals at the same time; When the inner tube control signals of the two inner tubes are at the second level at the same time, or when one of the inner tube control signals is at the first level and the other inner tube control signal is at the second level, determining that the inner tube control signals of the two inner tubes are not disconnection control signals at the same time; The first level is different from the second level, the first level is used to drive the switch tube to turn off, and the second level is used to drive the switch tube to turn on.

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