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

Abstract

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. The fault-tolerant device is applied to a power conversion circuit, the power conversion circuit includes a primary bridge circuit, a transformer and a secondary bridge circuit, the fault-tolerant device includes a fault-tolerant protection circuit, the fault-tolerant protection circuit is connected to the power conversion circuit, wherein the fault-tolerant protection circuit is used to output a fault-tolerant external tube control signal to the two external tubes when the external tube control signals of the two external tubes are disconnection control signals at the same time, and / or output a fault-tolerant internal tube control signal to the two internal tubes when the internal tube control signals of the two internal tubes are disconnection control signals at the same time; the fault-tolerant external tube control signal is used to control one of the two external tubes to be turned on, and the fault-tolerant internal tube control signal is used to control one of the two internal tubes to be turned on, so that the secondary current on the secondary side can continue to flow, thereby reducing the overstress risk of the secondary side switch tube and ensuring the operation of the power conversion circuit.

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 parallel, the first secondary bridge arm includes two bidirectional switches 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 to the power conversion circuit, wherein the fault-tolerant protection circuit 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, the fault-tolerant external tube control signal is output to the two external tubes; the fault-tolerant external tube control signal is used to control one of the two external tubes to be turned on; and / or, when the internal tube control signals of the two internal tubes are disconnection control signals at the same time, the fault-tolerant internal tube control signal is output to the two internal tubes; the fault-tolerant internal tube control signal is used to control one of the two internal tubes to be turned on.

[0005] In one embodiment, the fault-tolerant protection circuit is also used to output the acquired external tube control signal to the two external tubes when the external tube control signals of the two external tubes are not disconnection control signals at the same time; and / or, when the internal tube control signals of the two internal tubes are not disconnection control signals at the same time, output the acquired internal tube control signal to the two internal tubes.

[0006] In one embodiment, the fault-tolerant protection circuit includes a first fault-tolerant processing circuit and a second fault-tolerant processing circuit. The first fault-tolerant processing circuit includes a first logic unit and a first selection unit connected to each other. The first logic unit is used to output a first selection signal to the first selection unit when the two external tube control signals are at the first level at the same time; and, when the two external tube control signals are at the second level at the same time, or one of the external tube control signals is at the first level and the other external tube control signal is at the second level, output a second selection signal to the first selection unit. The first selection unit is used to use the second level as the external tube control signal of one of the external tubes when receiving the first selection signal, and keep the external tube control signal of the other external tube unchanged, so as to obtain the fault-tolerant external tube control signals of the two external tubes; and, when receiving the second selection signal, keep the external tube control signals of the two external tubes unchanged. The second fault-tolerant processing circuit includes a second logic unit and a second selection unit connected to each other. The second logic unit is used to output a first selection signal to the second selection unit when the inner tube control signals of the two inner tubes are at the first level at the same time; and, 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, output a second selection signal to the second selection unit. The second selection unit is used to use the second level as the inner tube control signal of one of the inner tubes when receiving the first selection signal, and keep the inner tube control signal of the other inner tube unchanged, so as to obtain the fault-tolerant inner tube control signals of the two inner tubes; and, when receiving the second selection signal, keep the inner tube control signals of the two inner tubes unchanged. 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 conduct.

[0007] In one embodiment, the first logic unit and the second logic unit are both NOR gates, and the first selection unit and the second selection unit are both switch chips.

[0008] In one embodiment, the fault-tolerant device also includes a modulation circuit, which is connected to the fault-tolerant protection circuit. The modulation circuit is used to generate external tube control signals for the two external tubes and internal tube control signals for the two internal tubes, and transmit the two external tube control signals and the two internal tube control signals to the fault-tolerant protection circuit.

[0009] 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, 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 parallel, the first secondary bridge arm includes two bidirectional switches 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 protection circuit is connected to the power conversion circuit, wherein the fault-tolerant protection circuit 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, the fault-tolerant external tube control signal is output to the two external tubes; the fault-tolerant external tube control signal is used to control one of the two external tubes to be turned on; and / or, when the internal tube control signals of the two internal tubes are disconnection control signals at the same time, the fault-tolerant internal tube control signal is output to the two internal tubes; the fault-tolerant internal tube control signal is used to control one of the two internal tubes to be turned on.

[0010] In one embodiment, the fault-tolerant protection circuit is also used to output the acquired external tube control signal to the two external tubes when the external tube control signals of the two external tubes are not disconnection control signals at the same time; and / or, when the internal tube control signals of the two internal tubes are not disconnection control signals at the same time, output the acquired internal tube control signal to the two internal tubes.

[0011] In one embodiment, the fault-tolerant protection circuit includes a first fault-tolerant processing circuit and a second fault-tolerant processing circuit. The first fault-tolerant processing circuit includes a first logic unit and a first selection unit connected to each other. The first logic unit is used to output a first selection signal to the first selection unit when the two external tube control signals are at the first level at the same time; and, when the two external tube control signals are at the second level at the same time, or one of the external tube control signals is at the first level and the other external tube control signal is at the second level, output a second selection signal to the first selection unit. The first selection unit is used to use the second level as the external tube control signal of one of the external tubes when receiving the first selection signal, and keep the external tube control signal of the other external tube unchanged, so as to obtain the fault-tolerant external tube control signals of the two external tubes; and, when receiving the second selection signal, keep the external tube control signals of the two external tubes unchanged. The second fault-tolerant processing circuit includes a second logic unit and a second selection unit connected to each other. The second logic unit is used to output a first selection signal to the second selection unit when the inner tube control signals of the two inner tubes are at the first level at the same time; and, 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, output a second selection signal to the second selection unit. The second selection unit is used to use the second level as the inner tube control signal of one of the inner tubes when receiving the first selection signal, and keep the inner tube control signal of the other inner tube unchanged, so as to obtain the fault-tolerant inner tube control signals of the two inner tubes; and, when receiving the second selection signal, keep the inner tube control signals of the two inner tubes unchanged. 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 conduct.

[0012] In one embodiment, when the power conversion circuit generates a secondary current, one of the bidirectional switches and the secondary side of the transformer always constitutes a freewheeling loop of the secondary current, and / or another bidirectional switch and the secondary side of the transformer always constitutes another freewheeling loop of the secondary current.

[0013] 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.

[0014] In one embodiment, the power conversion device further includes a modulation circuit, the modulation circuit is used to generate a control signal of 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 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 internal tube in the secondary bridge circuit. The modulation circuit is connected to the fault-tolerant protection circuit and is used to transmit the external tube control signals of the two external tubes and the internal tube control signals of the two internal tubes to the fault-tolerant protection circuit.

[0015] In one embodiment, the primary bridge circuit includes a first primary bridge arm and a second primary bridge arm connected in parallel, 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.

[0016] The 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 of the embodiments 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.

[0017] 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, 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 in parallel, the first secondary bridge arm includes two bidirectional switches 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 power conversion circuit is also connected to a fault-tolerant protection circuit, and the fault-tolerant method is performed by the fault-tolerant protection circuit. 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, outputting the fault-tolerant outer tube control signal to the two outer tubes; the fault-tolerant outer tube control signal is used to control one of the two outer tubes to be turned on; and / or, when the inner tube control signals of two inner tubes are disconnection control signals at the same time, outputting the fault-tolerant inner tube control signal to the two inner tubes; the fault-tolerant inner tube control signal is used to control one of the two inner tubes to be turned on.

[0018] 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, outputting the acquired outer tube control signal to the two outer tubes; and / or, when the inner tube control signals of the two inner tubes are not disconnection control signals at the same time, outputting the acquired inner tube control signal to the two inner tubes.

[0019] In one embodiment, the fault-tolerant protection circuit includes a first fault-tolerant processing circuit and a second fault-tolerant processing circuit, the first fault-tolerant processing circuit includes a first logic unit and a first selection unit connected to each other, and the second fault-tolerant processing circuit includes a second logic unit and a second selection unit connected to each other. Based on this, when the external tube control signals of the two external tubes are disconnection control signals at the same time, the process of outputting the fault-tolerant external tube control signals to the two external tubes includes: when the two external tube control signals are at the first level at the same time, outputting the first selection signal through the first logic unit; and using the second level as the external tube control signal of one of the external tubes in response to the first selection signal output by the first logic unit through the first selection unit, and keeping the external tube control signal of the other external tube unchanged, thereby obtaining the fault-tolerant external tube control signals of the two external tubes. Correspondingly, when the external tube control signals of the two external tubes are not disconnection control signals at the same time, the process of outputting the acquired external tube control signal to the two external tubes includes: when the two external tube control signals 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, outputting a second selection signal through the first logic unit; and keeping the external tube control signals of the two external tubes unchanged in response to the second selection signal output by the first logic unit through the first selection unit.

[0020] In addition, when the inner tube control signals of the two inner tubes are disconnection control signals at the same time, the process of outputting the fault-tolerant inner tube control signals to the two inner tubes includes: when the inner tube control signals of the two inner tubes are at the first level at the same time, outputting the first selection signal through the second logic unit; using the second level as the inner tube control signal of one of the inner tubes in response to the first selection signal output by the second logic unit, and keeping the inner tube control signal of the other inner tube unchanged, thereby obtaining the fault-tolerant inner tube control signals of the two inner tubes. Correspondingly, when the inner tube control signals of the two inner tubes are not disconnection control signals at the same time, the process of outputting the acquired inner tube control signal to the two inner tubes includes: 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, outputting the second selection signal through the second logic unit; and keeping the inner tube control signals of the two inner tubes unchanged in response to the second selection signal output by the second logic unit through the second selection unit. Among them, 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 conduct.

[0021] Compared with the prior art, this application has at least the following advantages:

[0022] 1. The present application adds a fault-tolerant protection circuit to the power conversion circuit. When the secondary control signal erroneously drives both outer tubes to disconnect, the fault-tolerant protection circuit can perform fault-tolerant processing on the erroneous secondary control signal, and use the fault-tolerant secondary control signal to actively control one of the outer tubes to be turned on, so that the secondary current can continue to flow normally through the channel of the turned-on outer tube. When the secondary control signal erroneously drives the two inner tubes to disconnect, the fault-tolerant protection circuit can also perform fault-tolerant processing on the erroneous secondary control signal, and use the fault-tolerant secondary control signal to actively control one of the inner tubes to be turned on, so that the secondary current can continue to flow normally through the channel of the turned-on inner tube. 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 current and boosting. Therefore, the present 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.

[0023] 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.

[0024] 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 and simple control. Moreover, when the secondary control signal is normal, the present application does not need to change the original control logic of the outer tube and the inner tube, so it will not increase the control complexity of the outer tube and the inner tube, and it is not easy to cause control logic confusion.

[0025] 4. The fault-tolerant protection circuit of the present application can be a hardware protection circuit, and the fault-tolerant protection of the power conversion circuit can be more reliable and stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of a power supply system provided in an embodiment of the present application.

[0027] Figure 2 yes Figure 1 A schematic diagram of a power conversion circuit and a fault-tolerant device in FIG.

[0028] Figure 3 yes Figure 1 A circuit diagram of a power conversion circuit in FIG.

[0029] Figure 4 yes Figure 3 A working waveform diagram of the power conversion circuit shown when it operates normally.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] Figure 8 yes Figure 7 A partial enlarged view of the portion near a zero crossing point of the waveform shown.

[0034] Fig. 9 yes Figure 1 A structural schematic diagram of a fault-tolerant device in.

[0035] Fig.10 yes Fig. 9 A circuit diagram of a fault-tolerant protection circuit in.

[0036] Fig.11 After setting the fault-tolerant device of the embodiment of the present application, 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.

[0037] Fig.12 After setting the fault-tolerant device of the embodiment of the present application, Figure 3 Another flow diagram of the secondary current in the power conversion circuit shown in FIG. 1 when a control timing error occurs.

[0038] Fig.13 After setting the fault-tolerant device of the embodiment of the present application, 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.

[0039] Fig.14 It is a flow chart of a fault-tolerant method for a power conversion circuit provided in an embodiment of the present application.

[0040] Main component symbols

[0041] 100-power supply system, 10-DC power supply, 11-energy storage equipment, 12-photovoltaic power generation equipment, 20-power conversion equipment,

[0042] 21-power conversion circuit, 211-primary bridge circuit, 2111-first primary bridge arm, 2112-second primary bridge arm,

[0043] 212-transformer, 213-resonant inductor, 214-secondary bridge circuit, 2141-first secondary bridge arm,

[0044] 2142-second secondary bridge arm, 22-fault-tolerant device, 220-modulation circuit, 221-fault-tolerant protection circuit,

[0045] 222-first fault-tolerant processing circuit, 2221-first logic unit, 2222-first selection unit,

[0046] 223 - second fault-tolerant processing circuit, 2231 - second logic unit, 2232 - second selection unit, 30 - common coupling point,

[0047] 40-grid, 50-AC load. DETAILED DESCRIPTION

[0048] 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.

[0049] See also Figure 1 , showing a topological diagram of a power supply system 100 provided in an embodiment of the present application.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] For the convenience of description, the present application embodiment is 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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. When the real-time AC voltage Vac is positive, under the control of 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 control signals S6 and S8, the first inner tube Q6 and the second outer tube Q8 are always on, so that the first bidirectional switch and the secondary side of the transformer constitute a freewheeling loop of the secondary current, and / or the second bidirectional switch and the secondary side of the transformer constitute another freewheeling loop of the secondary current. To avoid the first secondary bridge arm from being directly connected, 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.

[0067] When the real-time AC voltage Vac is negative, under the control of 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 control signals S5 and S7, the first outer tube Q5 and the second inner tube Q7 are always turned on, so that the first bidirectional switch and the secondary side of the transformer constitute a freewheeling loop of the secondary current, and / or the second bidirectional switch and the secondary side of the transformer constitute another freewheeling loop of the secondary current. In order 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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 8 It 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.

[0072] 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.

[0073] Specifically, if Figure 1 As shown, the fault-tolerant device 22 can be arranged in the power conversion device 20 and connected to the power conversion circuit 21. Specifically, the fault-tolerant device 22 can be connected to the control end of the switch tubes Q1-Q8 in the power conversion circuit 21, and output a control signal to the switch tubes Q1-Q8 to control the on-off state of the switch tubes Q1-Q8, thereby realizing the control of the working condition of the power conversion circuit 21.

[0074] like Figure 2As shown, the fault-tolerant device 22 includes a modulation circuit 220 and a fault-tolerant protection circuit 221, and the modulation circuit 220 and the fault-tolerant protection circuit 221 are connected. The modulation circuit 220 can be used to modulate and generate control signals S1~S8 of the switch tubes Q1~Q8, and transmit the external tube control signals S5, S8 of the external tubes Q5 and Q8 in the secondary bridge circuit and the internal tube control signals S6, S7 of the internal tubes Q6 and Q7 to the fault-tolerant protection circuit 221. Furthermore, the fault-tolerant protection circuit 221 can obtain the external tube control signals S5, S8 and the internal tube control signals S6, S7, and perform corresponding fault-tolerant processing when the control timing of the external tube control signals S5, S8 and the internal tube control signals S6, S7 is wrong. The external tube control signal after the fault-tolerant processing is used to be given to the external tube of the secondary bridge circuit 214, and the internal tube control signal after the fault-tolerant processing is used to be given to the internal tube of the secondary bridge circuit 214.

[0075] In the embodiment of the present application, the modulation circuit 220 may adopt any general modulation circuit, such as a PWM modulation circuit, etc. The fault-tolerant protection circuit 221 may select a corresponding circuit or module according to actual conditions.

[0076] In some embodiments, the fault-tolerant protection circuit 221 is a pure hardware circuit. Fig. 9 and Fig.10 The fault-tolerant protection circuit 221 is shown as an example. For the sake of distinction, in the embodiment of the present application, the control signal input to the fault-tolerant device 22 is represented as S5-S8, and the control signal finally output by the fault-tolerant device 22 is represented as S5'-S8'.

[0077] See also Fig. 9 and Fig.10 The fault-tolerant protection circuit 221 in the fault-tolerant device 22 includes a first fault-tolerant processing circuit 222 and a second fault-tolerant processing circuit 223, wherein the first fault-tolerant processing circuit 222 includes a first logic unit 2221 and a first selection unit 2222, and the second fault-tolerant processing circuit 223 includes a second logic unit 2231 and a second selection unit 2232.

[0078] In this embodiment, if Fig.10 As shown, the first logic unit 2221 and the second logic unit 2231 can both use NOR gates, and the first selection unit 2222 and the second selection unit 2232 can both use switch chips. The switch chip can select a corresponding type of switch chip according to actual conditions, such as an analog switch chip. The switch chip has a first input pin IN1, a second input pin IN2, a third input pin IN3, a selection pin Select, a first output pin OUT1, and a second output pin OUT2. It should be understood that Fig.10The pin numbers of the switch chip shown in the figure are only examples and do not constitute a specific limitation on the embodiments of the present application. In practical applications, other pin numbers can also be used to implement Fig.10 The functions of the pins are shown in FIG. 1 , or the switch chip may include more or fewer pins.

[0079] Specifically, two input terminals of the first logic unit 2221 are connected to the modulation circuit 220 to access the two external control signals S5 and S8 , and an output terminal of the first logic unit 2221 is connected to a selection pin Select of the first selection unit 2222 .

[0080] The first logic unit 2221 is used to output a first selection signal to the first selection unit 2222 when the two external control signals S5 and S8 are at the first level at the same time; and output a second selection signal to the first selection unit 2222 when the two external control signals S5 and S8 are at the second level at the same time, or one of the external control signals is at the first level and the other external control signal is at the second level, that is, when the external control signals S5 and S8 are not at the first level at the same time.

[0081] The first selection signal and the second selection signal are different electrical signals. For example, the first selection signal may be a high level (eg, represented by 1), and the second selection signal may be a low level (eg, represented by 0).

[0082] The first input pin IN1 of the first selection unit 2222 is used to access the power level VCC from the power supply, and the power level VCC is a high level (for example, 1), so it is also equivalent to the second level. The power supply can be the internal power supply of the fault-tolerant device 22, the external power supply, or other circuits that can provide the power level, which are not specifically limited here. The second input pin IN2 of the first selection unit 2222 is used to connect the modulation circuit 220 to access the external tube control signal of one of the external tubes generated by the modulation circuit 220. The third input pin IN3 of the first selection unit 2222 is used to connect the modulation circuit 220 to access the external tube control signal of another external tube generated by the modulation circuit 220. The first output pin OUT1 of the first selection unit 2222 is used to output the final control signal of one of the external tubes, and the second output pin OUT2 of the first selection unit 2222 is used to output the final control signal of the other external tube.

[0083] For ease of description, Fig.10 In the example, the second input pin IN2 of the first selection unit 2222 is connected to S5, the third input pin IN3 of the first selection unit 2222 is connected to S8, the first output pin OUT1 of the first selection unit 2222 is used to output S5', and the second output pin OUT2 of the first selection unit 2222 is used to output S8'.

[0084] The first selection unit 2222 is used for, when receiving the first selection signal, using the second level as the external tube control signal of the external tube Q5, and keeping the external tube control signal of the external tube Q8 unchanged, thereby obtaining the fault-tolerant external tube control signal S5' of the external tube Q5 and the fault-tolerant external tube control signal S8' of the external tube Q8; and, when receiving the second selection signal, keeping the external tube control signals of the two external tubes Q5 and Q8 unchanged.

[0085] That is to say, as shown in Table 1 below, when S5 and S8 connected to the first logic unit 2221 are both at the first level (for example, can be represented as 0), the first logic unit 2221 generates a first selection signal (for example, can be represented as 1), and accordingly, the fault-tolerant external tube control signal S5' output by the first selection unit 2222 is at the second level (that is, VCC, for example, can be represented as 1), and the fault-tolerant external tube control signal S8' output by the first selection unit 2222 is the original external tube control signal S8 (that is, the first level, for example, can be represented as 0).

[0086] When S5 and S8 connected to the first logic unit 2221 are not at the first level at the same time, the first logic unit 2221 generates a second selection signal (for example, can be represented as 0), and accordingly, S5' output by the first selection unit 2222 remains as the original external control signal S5, and S8' remains as the original external control signal S8.

[0087] Table 1

[0088]

[0089] Similarly, two input terminals of the second logic unit 2231 are connected to the modulation circuit 220 to access the two internal tube control signals S6 and S7 , and an output terminal of the second logic unit 2231 is connected to a selection pin Select of the second selection unit 2232 .

[0090] The second logic unit 2231 is used to output a first selection signal to the second selection unit 2232 when the two inner tube control signals S6 and S7 are at the first level at the same time; and output a second selection signal to the second selection unit 2232 when the two inner tube control signals S6 and S7 are at the second level at the same time, or one of the inner tube control signals is the first level and the other inner tube control signal is the second level, that is, when the outer tube control signals S5 and S8 are not at the first level at the same time.

[0091] The first input pin IN1 of the second selection unit 2232 is used to access VCC from the power supply, that is, the second level. The second input pin IN2 of the second selection unit 2232 is used to connect the modulation circuit 220 to access the inner tube control signal of one of the inner tubes generated by the modulation circuit 220. The third input pin IN3 of the second selection unit 2232 is used to connect the modulation circuit 220 to access the inner tube control signal of another inner tube generated by the modulation circuit 220. The first output pin OUT1 of the second selection unit 2232 is used to output the final control signal of one of the inner tubes, and the second output pin OUT2 of the second selection unit 2232 is used to output the final control signal of the other inner tube.

[0092] For ease of description, Fig.10 In the example, the second input pin IN2 of the second selection unit 2232 is connected to S7, the third input pin IN3 of the second selection unit 2232 is connected to S6, the first output pin OUT1 of the second selection unit 2232 is used to output S7', and the second output pin OUT2 of the second selection unit 2232 is used to output S6'.

[0093] The second selection unit 2232 is used to, when receiving the first selection signal, use the second level as the inner tube control signal S7' of the inner tube Q7, and keep the inner tube control signal S6 of the inner tube Q6 unchanged, thereby obtaining the fault-tolerant inner tube control signal S7' of the inner tube Q7 and the fault-tolerant inner tube control signal S6' of the inner tube Q6; and, when receiving the second selection signal, keep the inner tube control signals of the two inner tubes Q7 and Q6 unchanged.

[0094] That is to say, as shown in Table 2 below, when S6 and S7 connected to the second logic unit 2231 are both at the first level (for example, can be represented as 0), the second logic unit 2231 generates a first selection signal (for example, can be represented as 1), and accordingly, the fault-tolerant external tube control signal S7' output by the second selection unit 2232 is the second level (that is, VCC, for example, can be represented as 1), and the fault-tolerant external tube control signal S6' output by the second selection unit 2232 is the original external tube control signal S6 (that is, the first level, for example, can be represented as 0).

[0095] When S6 and S7 connected to the second logic unit 2231 are not at the first level at the same time, the second logic unit 2231 generates a second selection signal (for example, can be represented as 0), and accordingly, S7' output by the second selection unit 2232 remains as the original internal tube control signal S7, and S6' remains as the original internal tube control signal S6.

[0096] Table 2

[0097]

[0098] Based on such a design, when the control timing is wrong and the inner tube control signals S6 and S7 of the two inner tubes are disconnection control signals at the same time, the fault-tolerant protection circuit 221 can output the fault-tolerant inner tube control signal S6' to the inner tube Q6 and output the fault-tolerant inner tube control signal S7' to the inner tube Q7. The fault-tolerant inner tube control signals S6' and S7' can be used to control one of the two inner tubes Q6 and Q7 to be turned on. For example, S7' shown in Table 2 is used to control Q7 to be turned on, and S6' is used to control Q6 to be turned off.

[0099] It can be understood that when the inner tube control signals S6 and S7 are both disconnection control signals, under the control of the disconnection control signals, the inner tubes Q6 and Q7 are both disconnected. Figure 5 As described in 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. However, the fault-tolerant protection circuit 221 of the embodiment of the present application actively processes the inner tube control signals S6 and S7 in a fault-tolerant manner, so that one of the inner tube control signals changes from a disconnection control signal to a conduction control signal, to ensure that Q6 and Q7 are not turned off at the same time.

[0100] For example, if the fault-tolerant internal tube control signal S6' is a conduction control signal, so that Q6 is turned on, then Fig.11 As shown, the secondary current is can be continuously circulated through the channel of Q6, but not through the parasitic capacitance of Q6, thereby suppressing the continuous current boost of the parasitic capacitance of Q6. Due to the strong current-carrying capacity of the channel, the secondary current is can be continuously circulated more through the channel of Q6, thereby suppressing the continuous current boost of the parasitic capacitance of Q7. Therefore, the overstress risk of Q6 and Q7 can be reduced. Among them, when Q5 is turned on, the secondary current is can flow to the secondary side of the transformer through the channel of Q5 after flowing through the channel of Q6. When Q5 is turned off, the secondary current is can flow to the secondary side of the transformer through the body diode of Q5 after flowing through the channel of Q6. That is, at this time, the first bidirectional switch and the secondary side of the transformer 212 constitute a continuous current loop of the secondary current.

[0101] For another example, if the fault-tolerant internal tube control signal S7' is a conduction control signal, so that Q7 is turned on, then Fig.11As shown, the secondary current is can be continuously circulated through the channel of Q7, but not through the parasitic capacitance of Q7, thereby suppressing the continuous current boost of the parasitic capacitance of Q7. Because the secondary current is can be continuously circulated more through the channel of Q7, the continuous current boost of the parasitic capacitance of Q6 is also suppressed. Therefore, the overstress risk of Q6 and Q7 can be reduced. Among them, when Q8 is turned on, the secondary current is can flow to the secondary side of the transformer through the channel of Q8 after flowing through the channel of Q7. When Q8 is turned off, the secondary current is can flow to the secondary side of the transformer through the body diode of Q8 after flowing through the channel of Q7. That is, at this time, the second bidirectional switch and the secondary side of the transformer 212 constitute a continuous current loop for the secondary current.

[0102] Similarly, when the control timing is wrong and the external tube control signals S5 and S8 of the two external tubes are disconnection control signals at the same time, the fault-tolerant protection circuit 221 can output the fault-tolerant external tube control signal S5' to the external tube Q5 and output the fault-tolerant external tube control signal S8' to the external tube Q8. The fault-tolerant external tube control signals S5' and S8' can be used to control one of the two external tubes Q5 and Q8 to be turned on. For example, as shown in Table 1, S5' is used to control Q5 to be turned on, and S8' is used to control Q8 to be turned off.

[0103] It can be understood that when the external tube control signals S5 and S8 are both disconnection control signals, under the control of the disconnection control signals, the external tubes Q5 and Q8 are both disconnected. Figure 6 As described above, the reverse-flowing secondary current is can only be continued through the parasitic capacitance of the external tube Q5 and the parasitic capacitance of the external tube Q8, resulting in large voltage stress of Q5 and Q8 and high risk of stress damage. However, the fault-tolerant protection circuit 221 of the embodiment of the present application actively processes the external tube control signals S5 and S8 in a fault-tolerant manner, so that one of the external tube control signals changes from a disconnection control signal to a conduction control signal, to ensure that Q5 and Q8 are not turned off at the same time.

[0104] For example, if the fault-tolerant external control signal S5' is a conduction control signal, so that Q5 is turned on, then Fig.12 As shown, the secondary current is can be continuously circulated through the channel of Q5, but not through the parasitic capacitance of Q5, thus suppressing the continuous current boost of the parasitic capacitance of Q5. Because the secondary current is can be continuously circulated more through the channel of Q5, the continuous current boost of the parasitic capacitance of Q8 is also suppressed. Therefore, the overstress risk of Q5 and Q8 can be reduced. Among them, when Q6 is turned on, the secondary current is can flow to the secondary side of the transformer through the channel of Q6 after flowing through the channel of Q5. When Q6 is turned off, the secondary current is can flow to the secondary side of the transformer through the body diode of Q6 after flowing through the channel of Q5. That is, at this time, the first bidirectional switch and the secondary side of the transformer constitute a continuous current loop for the secondary current.

[0105] For another example, if the fault-tolerant external control signal S8' is a conduction control signal, so that Q8 is turned on, then Fig.12 As shown, the secondary current is can be continuously circulated through the channel of Q8, but not through the parasitic capacitance of Q8, thereby suppressing the continuous current boost of the parasitic capacitance of Q8. Because the secondary current is can be continuously circulated more through the channel of Q8, the continuous current boost of the parasitic capacitance of Q5 is also suppressed. Therefore, the overstress risk of Q5 and Q8 can be reduced. Among them, when Q7 is turned on, the secondary current is can flow to the secondary side of the transformer through the channel of Q7 after flowing through the channel of Q8. When Q7 is turned off, the secondary current is can flow to the secondary side of the transformer through the body diode of Q7 after flowing through the channel of Q8. That is, at this time, the second bidirectional switch and the secondary side of the transformer 212 constitute a continuous current loop for the secondary current.

[0106] It can be seen that based on the fault-tolerant device 20 of the embodiment of the present application, in the case of a control timing error of the secondary control signal, no matter whether the secondary current is flows in the forward direction or the reverse direction, the two outer tubes of the secondary bridge circuit 214 will not be disconnected at the same time, and the two inner tubes will not be disconnected at the same time. The secondary bridge circuit 214 can always continue the flow of the secondary current is, suppress the continued flow and voltage boost of the parasitic capacitance, and thus reduce the voltage stress of the secondary switch tube, and prevent the secondary switch tube from being damaged by overstress, thereby ensuring the operation of the power conversion circuit 21.

[0107] Therefore, through the fault-tolerant device 20 of the embodiment of the present application, it is possible to avoid the power conversion circuit 21 from being damaged by overstress of the secondary switch tube due to the inability of the secondary current to continue to flow due to the control timing error, thereby achieving fault-tolerant protection of the secondary switch tube and the power conversion circuit 21. Moreover, the fault-tolerant processing of the fault-tolerant device 20 of the embodiment of the present application will not cause the two outer tubes and the two inner tubes to be turned on at the same time, that is, it will not cause the first secondary bridge arm 2141 to be directly turned on, which makes the safe operation of the secondary bridge circuit 214 more guaranteed.

[0108] In addition, under normal circumstances, Q5 and Q8 are turned on alternately at high frequency and Q6 and Q8 are always on, or Q6 and Q8 are turned on alternately at high frequency and Q5 and Q8 are always 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 both on control signals, or one of the external tube control signals is a disconnection control signal and the other external tube control signal is an on control signal. Since in these cases, Q5 and Q8 are not disconnected at the same time, and at least one external tube is turned on, 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 follow-up boost of the parasitic capacitance of Q5 and Q8, which affects the operation of the circuit.

[0109] 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 follow-up boost of the parasitic capacitance of Q6 and Q7, which affects the operation of the circuit.

[0110] That is to say, in the above case, the power conversion circuit 21 can operate normally. The fault-tolerant protection circuit 221 of the embodiment of the present application can output the original inner tube control signals S6 and S7 when the inner tube control signals S6 and S7 of the two inner tubes are not disconnection control signals at the same time, that is, when the control timing is normal; and output the original inner tube control signals S5 and S8 when the inner tube control signals S5 and S8 of the two outer tubes are not disconnection control signals at the same time, that is, when the control timing is normal. That is to say, the fault-tolerant protection circuit 221 of the embodiment of the present application will not interfere with the control timing when the control timing is normal.

[0111] It can be seen that the power conversion device 20 of the embodiment of the present application can not only perform fault-tolerant control on the secondary switch tube when the control timing error affects the normal operation of the secondary bridge circuit 214, so that the secondary bridge circuit 214 can continue to operate, but also can not affect the normal control of the secondary switch tube when the secondary bridge circuit 214 operates normally, so as to avoid affecting the operation of the secondary bridge circuit 214, 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 secondary bridge circuit 214 can always form a freewheeling loop of the secondary current is with the secondary side of the transformer 212 through at least one of the first bidirectional switch and the second bidirectional switch. Based on this, 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 safety 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.

[0112] Moreover, since there is no need to change the control logic of the secondary-side switch tube when the secondary-side bridge circuit 214 operates normally, the control complexity of the secondary-side bridge circuit 214 is also reduced.

[0113] In addition, compared with the fault-tolerant protection implemented purely by software, the fault-tolerant device 22 and the fault-tolerant protection circuit 221 can be hardware fault-tolerant protection, and the fault-tolerant protection of the power conversion circuit 21 can be more reliable and stable.

[0114] It should be understood that Fig. 9 and Fig.10The fault-tolerant protection circuit 221 described is only an illustrative example provided in this application. In some other embodiments, Fig. 9 and Fig.10 The fault-tolerant protection circuit 221 shown can be adaptively adjusted according to actual conditions. For example, two selection units can be integrated into one, or the selection unit and the logic unit in the same fault-tolerant processing circuit can be integrated into one. For another example, Fig.10 Other selection circuits or switch circuits can be used to implement the same function as the switch chip. Alternatively, other logic units or circuits can be used to implement the OR / NO function. For another example, Fig.10 As shown, the inputs IN1 and IN2 of the first selection unit 2222 can be swapped, the outputs OUT1 and OUT2 of the first selection unit 2222 can also be swapped, the inputs IN1 and IN2 of the second selection unit 2232 can also be swapped, and the outputs OUT1 and OUT2 of the second selection unit 2232 can also be swapped.

[0115] In other embodiments, the fault-tolerant protection circuit 221 may also be implemented by other digital-analog circuits, digital circuits, or analog circuits. Fig. 9 and Fig.10 In some other embodiments, the fault-tolerant protection circuit 221 may also adopt a chip module, such as a microcontroller unit (MCU) or a digital signal processor (DSP), etc., and the fault-tolerant processing of the secondary side control signal may be realized by a pure software program or a combination of a software program and a hardware circuit.

[0116] In some embodiments, the fault-tolerant device 22 may also be independently provided, or integrated with other circuits / modules / devices. In some other embodiments, the modulation circuit 220 may also be independent of the fault-tolerant device 22, that is, the fault-tolerant protection circuit 221 alone constitutes the fault-tolerant device 22. The specifics may be adjusted accordingly according to the actual situation, all within the protection scope of this application.

[0117] In addition, the fault-tolerant device 22 of the embodiment of the present application controls the operation of the primary bridge circuit 211 while controlling the operation of the secondary bridge circuit 214. Therefore, the fault-tolerant device 22 of the embodiment of the present application can also use the primary control signal generated by the modulation circuit 220 to control the first primary switch tube Q1 and the second primary switch tube Q2 to be alternately turned on, and control the third primary switch tube Q3 and the fourth primary switch tube Q4 to be alternately turned on.

[0118] 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 2When 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.

[0119] In addition, in order to verify the effect of the fault-tolerant processing circuit 221 of the embodiment of the present application on reducing the stress of the secondary-side switch tube, the embodiment of the present application also conducted a simulation experiment on the power conversion device 20.

[0120] Specifically, see Fig.13 , Fig.13 , when a control timing error occurs during the operation of the power conversion device 20, in which both Q5 and Q8 are disconnected, and / or both Q6 and Q7 are disconnected, a waveform diagram of the voltage borne by both ends of Q5 to Q8, that is, a voltage stress waveform diagram of Q5 to Q8, is shown.

[0121] Understandably, Fig.13 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 processing circuit 221. Fig.13 In the corresponding experiment, the power conversion device 20 is provided with a fault-tolerant processing circuit 221, and the fault-tolerant processing circuit 221 provides fault-tolerant protection.

[0122] from Fig.13 It can be seen that when the power conversion device 20 is working, although the control timing is wrong, the voltage stress waveform of Q5~Q8 can still smoothly transition near the voltage zero point without a spike, indicating that the stress of Q5~Q8 near the voltage zero point is almost 0. When S5~S8 are all disconnection control signals, since the fault-tolerant processing circuit 221 can process S5 and S6 into conduction control signals to control Q5 and Q6 to be turned on, the voltage stress of Q5~Q8 can be 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.

[0123] It can be seen that based on the fault-tolerant processing circuit 221 of the embodiment of the present application, 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.

[0124] In addition, based on Figure 1In 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 a fault-tolerant processing circuit 221 in the fault-tolerant device 22. Through the fault-tolerant protection circuit 221, when the secondary switch tube of the power conversion circuit 21 has a timing error in controlling the secondary switch tube, fault-tolerant protection of the secondary switch tube and the power conversion circuit 21 can be achieved.

[0125] Specifically, see Fig.14 The fault-tolerant method of the power conversion circuit of the embodiment of the present application comprises the following steps:

[0126] Step S10, obtaining an outer tube control signal and an inner tube control signal of a secondary side bridge circuit.

[0127] Specifically, the fault-tolerant processing circuit 221 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 220.

[0128] Step S20: when the external tube control signals of the two external tubes are disconnection control signals at the same time, output the fault-tolerant external tube control signal to the two external tubes; the fault-tolerant external tube control signal is used to control one of the two external tubes to be turned on.

[0129] 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:

[0130] 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.

[0131] 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.

[0132] 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.

[0133] 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.

[0134] Therefore, the process of step S20 can be specifically as follows:

[0135] When the two external tube control signals are at the first level at the same time, the second level is used as the external tube control signal of one of the external tubes, and the external tube control signal of the other external tube remains unchanged, thereby obtaining fault-tolerant external tube control signals of the two external tubes.

[0136] Further, in one embodiment, when the fault-tolerant processing circuit adopts Fig.10 When the circuit is shown, the process of the fault-tolerant processing circuit 221 executing step S20 may include the following sub-steps:

[0137] Step S201: When the two external control signals are at the first level at the same time, a first selection signal is output through a first logic unit.

[0138] Step S202: The first selection unit responds to the first selection signal output by the first logic unit, uses the second level as the external tube control signal of one of the external tubes, and keeps the external tube control signal of the other external tube unchanged, thereby obtaining fault-tolerant external tube control signals of the two external tubes.

[0139] Based on this, the external tube receiving the external tube control signal of the second level will be turned on, and the external tube receiving the external tube control signal of the first level will be turned off. That is, Q5 and Q8 are not turned off at the same time.

[0140] For example, in one embodiment, if S5 and S8 are both at the first level, the fault-tolerant external tube control signal S5' changes to the second level, which can be used to control the external tube Q5 to be turned on; the fault-tolerant external tube control signal S8' remains at the first level, which can be used to control the external tube Q8 to be turned off. In another embodiment, if S5 and S8 are both at the first level, the fault-tolerant external tube control signal S5' remains at the first level, which can be used to control the external tube Q5 to be turned off; the fault-tolerant external tube control signal S8' changes to the second level, which can be used to control the external tube Q8 to be turned on.

[0141] Step S30: when the inner tube control signals of the two inner tubes are disconnection control signals at the same time, output the fault-tolerant inner tube control signal to the two inner tubes; the fault-tolerant inner tube control signal is used to control one of the two inner tubes to be turned on.

[0142] In the embodiment of the present application, the process of step S30 may be specifically as follows:

[0143] When the two inner tube control signals are at the first level at the same time, the second level is used as the inner tube control signal of one of the inner tubes, and the inner tube control signal of the other inner tube remains unchanged, thereby obtaining fault-tolerant inner tube control signals of the two inner tubes.

[0144] Further, in one embodiment, when the fault-tolerant processing circuit adopts Fig.10 When the circuit is shown, the process of the fault-tolerant processing circuit 221 executing step S30 may include the following sub-steps:

[0145] Step S301: When the inner tube control signals of the two inner tubes are at the first level at the same time, a first selection signal is outputted through a second logic unit.

[0146] Step S302: In response to the first selection signal output by the second logic unit, the second selection unit uses the second level as the inner tube control signal of one of the inner tubes, and keeps the inner tube control signal of the other inner tube unchanged, thereby obtaining fault-tolerant inner tube control signals of the two inner tubes.

[0147] Based on this, the inner tube receiving the inner tube control signal of the second level will be turned on, and the inner tube receiving the inner tube control signal of the first level will be turned off. That is, Q6 and Q7 are not turned off at the same time.

[0148] For example, in one embodiment, if S6 and S7 are both at the first level, the fault-tolerant inner tube control signal S6' changes to the second level, which can be used to control the inner tube Q6 to be turned on; the fault-tolerant inner tube control signal S7' remains at the first level, which can be used to control the inner tube Q7 to be turned off. In another embodiment, if S5 and S8 are both at the first level, the fault-tolerant inner tube control signal S6' remains at the first level, which can be used to control the inner tube Q6 to be turned off; the fault-tolerant inner tube control signal S7' changes to the second level, which can be used to control the inner tube Q7 to be turned on.

[0149] 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 secondary side bridge circuit can always continue the flow of the secondary side current is, suppress the parasitic capacitance continue flow and voltage boost, 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.

[0150] 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.14 The fault tolerance method of the embodiment of the present application may also include the following steps:

[0151] Step S40: When the external tube control signals of the two external tubes are not disconnection control signals at the same time, output the acquired external tube control signal to the two external tubes.

[0152] In the embodiment of the present application, the process of step S40 may be specifically as follows:

[0153] When the two external tube control signals 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, the external tube control signals of the two external tubes are kept unchanged.

[0154] Further, in one embodiment, when the fault-tolerant processing circuit adopts Fig.10 When the circuit is shown, the process of the fault-tolerant processing circuit 221 executing step S40 may include the following sub-steps:

[0155] Step S401: when two external control signals are at the second level at the same time, or when one external control signal is at the first level and the other external control signal is at the second level, outputting a second selection signal through a first logic unit;

[0156] Step S402: The first selection unit responds to the second selection signal output by the first logic unit to keep the external tube control signals of the two external tubes unchanged.

[0157] Step S50: When the inner tube control signals of the two inner tubes are not disconnection control signals at the same time, output the acquired inner tube control signal to the two inner tubes.

[0158] In the embodiment of the present application, the process of step S50 may be specifically as follows:

[0159] When the inner tube control signals of the two inner tubes are at the second level at the same time, or when one inner tube control signal is at the first level and the other inner tube control signal is at the second level, the inner tube control signals of the two inner tubes are kept unchanged.

[0160] Further, in one embodiment, when the fault-tolerant processing circuit adopts Fig.10When the circuit is shown, the process of the fault-tolerant processing circuit 221 executing step S50 may include the following sub-steps:

[0161] Step S501: when the inner tube control signals of the two inner tubes are at the second level at the same time, or when one inner tube control signal is at the first level and the other inner tube control signal is at the second level, output a second selection signal through a second logic unit.

[0162] Step S502: The second selection unit responds to the second selection signal output by the second logic unit to keep the inner tube control signals of the two inner tubes unchanged.

[0163] It should be understood that "step S20", "step S30", "step S40", and "step S50" are only used to distinguish different situations, and do not limit the execution order. In actual applications, the fault-tolerant device 22 can execute one of "step S20" and "step S40" or one of "step S30" and "step S50" according to actual conditions.

[0164] 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:

[0165] 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.

[0166] 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 221 can be used to control the fault-tolerant operation of the secondary bridge circuit so that the secondary current is can continue to flow normally, thereby realizing fault-tolerant protection of the secondary switch tube and 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 fault-tolerant protection circuit 221 can be used to control the secondary bridge circuit 214 to operate normally so that the secondary current is can continue to flow normally. Therefore, regardless of whether the control timing is wrong or correct, the power conversion device 20 can always continue to flow 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.

[0167] Moreover, in some embodiments of the present application, the fault-tolerant protection and fault-tolerant methods proposed in the embodiments of the present application can be implemented by relying on hardware structure. Compared with relying on pure software program implementation, such an implementation method is more reliable and has higher control efficiency.

[0168] 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 parallel, 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 to the power conversion circuit, wherein: The fault-tolerant protection circuit is used to obtain the external tube control signal and the internal tube control signal of the secondary bridge circuit, and when the external tube control signals of the two external tubes are disconnection control signals at the same time, output the fault-tolerant external tube control signal to the two external tubes; the fault-tolerant external tube control signal is used to control one of the two external tubes to be turned on; and / or, When the inner tube control signals of the two inner tubes are disconnection control signals at the same time, the fault-tolerant inner tube control signal is output to the two inner tubes; the fault-tolerant inner tube control signal is used to control the conduction of one of the two inner tubes.

2. The fault-tolerant device according to claim 1, characterized in that: The fault-tolerant protection circuit is also used to output the acquired outer tube control signal to the two outer tubes when the outer tube control signals of the two outer tubes are not disconnection control signals at the same time; and / or, when the inner tube control signals of the two inner tubes are not disconnection control signals at the same time, output the acquired inner tube control signal to the two inner tubes.

3. The fault-tolerant device according to claim 1 or 2, characterized in that: The fault-tolerant protection circuit comprises a first fault-tolerant processing circuit and a second fault-tolerant processing circuit; The first fault-tolerant processing circuit includes a first logic unit and a first selection unit connected to each other, wherein: The first logic unit is used to output a first selection signal to the first selection unit when the two external control signals are at the first level at the same time; and output a second selection signal to the first selection unit when the two external control signals are at the second level at the same time, or when one of the external control signals is at the first level and the other external control signal is at the second level; The first selection unit is configured to, when receiving the first selection signal, use the second level as the external tube control signal of one of the external tubes, and keep the external tube control signal of the other external tube unchanged, thereby obtaining the fault-tolerant external tube control signals of the two external tubes; and, when receiving the second selection signal, keep the external tube control signals of the two external tubes unchanged; The second fault-tolerant processing circuit includes a second logic unit and a second selection unit connected to each other, wherein: The second logic unit is used to output a first selection signal to a second selection unit when the inner tube control signals of the two inner tubes are at the first level at the same time; and output a second selection signal to the second selection unit 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; The second selection unit is configured to, when receiving the first selection signal, use the second level as the inner tube control signal of one of the inner tubes, and keep the inner tube control signal of the other inner tube unchanged, thereby obtaining the fault-tolerant inner tube control signals of the two inner tubes; and, when receiving the second selection signal, keep the inner tube control signals of the two inner tubes unchanged; 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.

4. The fault-tolerant device according to claim 3, characterized in that: The first logic unit and the second logic unit are both NOR gates, and the first selection unit and the second selection unit are both switch chips.

5. The fault-tolerant device according to claim 1, characterized in that: The fault-tolerant device also includes a modulation circuit, which is connected to the fault-tolerant protection circuit. The modulation circuit is used to generate the outer tube control signals of the two outer tubes and the inner tube control signals of the two inner tubes, and transmit the outer tube control signals of the two outer tubes and the inner tube control signals of the two inner tubes to the fault-tolerant protection circuit.

6. 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 parallel, wherein the first secondary bridge arm comprises two bidirectional switches connected in series, and 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 to the power conversion circuit, wherein: The fault-tolerant protection circuit is used to obtain the external tube control signal and the internal tube control signal of the secondary bridge circuit, and when the external tube control signals of the two external tubes are disconnection control signals at the same time, output the fault-tolerant external tube control signal to the two external tubes; the fault-tolerant external tube control signal is used to control one of the two external tubes to be turned on; and / or, When the inner tube control signals of the two inner tubes are disconnection control signals at the same time, the fault-tolerant inner tube control signal is output to the two inner tubes; the fault-tolerant inner tube control signal is used to control the conduction of one of the two inner tubes.

7. The power conversion device according to claim 6, characterized in that The fault-tolerant protection circuit is also used to output the acquired outer tube control signal to the two outer tubes when the outer tube control signals of the two outer tubes are not disconnection control signals at the same time; and / or, when the inner tube control signals of the two inner tubes are not disconnection control signals at the same time, output the acquired inner tube control signal to the two inner tubes.

8. The power conversion device according to claim 6, characterized in that The fault-tolerant protection circuit comprises a first fault-tolerant processing circuit and a second fault-tolerant processing circuit; The first fault-tolerant processing circuit includes a first logic unit and a first selection unit connected to each other, wherein: The first logic unit is used to output a first selection signal to the first selection unit when the two external control signals are at the first level at the same time; and output a second selection signal to the first selection unit when the two external control signals are at the second level at the same time, or when one of the external control signals is at the first level and the other external control signal is at the second level; The first selection unit is configured to, when receiving the first selection signal, use the second level as the external tube control signal of one of the external tubes, and keep the external tube control signal of the other external tube unchanged, thereby obtaining the fault-tolerant external tube control signals of the two external tubes; and, when receiving the second selection signal, keep the external tube control signals of the two external tubes unchanged; The second fault-tolerant processing circuit includes a second logic unit and a second selection unit connected to each other, wherein: The second logic unit is used to output a first selection signal to a second selection unit when the inner tube control signals of the two inner tubes are at the first level at the same time; and output a second selection signal to the second selection unit 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; The second selection unit is configured to, when receiving the first selection signal, use the second level as the inner tube control signal of one of the inner tubes, and keep the inner tube control signal of the other inner tube unchanged, thereby obtaining the fault-tolerant inner tube control signals of the two inner tubes; and, when receiving the second selection signal, keep the inner tube control signals of the two inner tubes unchanged; 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.

9. The power conversion device according to claim 6, characterized in that When the power conversion circuit generates a secondary current, one of the bidirectional switches and the secondary side of the transformer always constitutes a freewheeling loop of the secondary current, and / or the other bidirectional switch and the secondary side of the transformer always constitutes another freewheeling loop of the secondary current.

10. The power conversion device according to claim 6, 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.

11. The power conversion device according to claim 6, characterized in that The power conversion device further includes a modulation circuit, the modulation circuit is used to generate a control signal of the power conversion circuit, wherein the control signal of the power conversion circuit includes a primary control signal, the external tube control signal and the 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 internal tube in the secondary bridge circuit; The modulation circuit is connected to the fault-tolerant protection circuit and is used for transmitting the outer tube control signals of the two outer tubes and the inner tube control signals of the two inner tubes to the fault-tolerant protection circuit.

12. The power conversion device according to claim 6, characterized in that The primary bridge circuit includes a first primary bridge arm and a second primary bridge arm connected in parallel, 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.

13. 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 6 to 12, wherein 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.

14. 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, 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 parallel, the first secondary bridge arm includes two bidirectional switches connected in series, both of the two 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 power conversion circuit is also connected to a fault-tolerant protection circuit, and the fault-tolerant method is executed by the fault-tolerant protection circuit; 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 external tube control signals of the two external tubes are disconnection control signals at the same time, outputting the fault-tolerant external tube control signal to the two external tubes; the fault-tolerant external tube control signal is used to control one of the two external tubes to be turned on; and / or, When the inner tube control signals of the two inner tubes are disconnection control signals at the same time, the fault-tolerant inner tube control signal is output to the two inner tubes; the fault-tolerant inner tube control signal is used to control the conduction of one of the two inner tubes.

15. The fault-tolerant method according to claim 14, 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, the obtained outer tube control signal is output to the two outer tubes; and / or, when the inner tube control signals of the two inner tubes are not disconnection control signals at the same time, the obtained inner tube control signal is output to the two inner tubes.

16. The fault-tolerant method according to claim 15, characterized in that: The fault-tolerant protection circuit comprises a first fault-tolerant processing circuit and a second fault-tolerant processing circuit, wherein the first fault-tolerant processing circuit comprises a first logic unit and a first selection unit connected to each other, and the second fault-tolerant processing circuit comprises a second logic unit and a second selection unit connected to each other; When the external tube control signals of the two external tubes are disconnection control signals at the same time, outputting the fault-tolerant external tube control signals to the two external tubes comprises: When the two external control signals are at the first level at the same time, the first logic unit outputs a first selection signal; The first selection unit responds to the first selection signal output by the first logic unit, uses the second level as the external tube control signal of one of the external tubes, and keeps the external tube control signal of the other external tube unchanged, thereby obtaining the fault-tolerant external tube control signals of the two external tubes; Correspondingly, when the external tube control signals of the two external tubes are not disconnection control signals at the same time, outputting the acquired external tube control signal to the two external tubes includes: When the two external control signals are at the second level at the same time, or when one of the external control signals is at the first level and the other external control signal is at the second level, outputting a second selection signal through the first logic unit; By the first selection unit responding to the second selection signal output by the first logic unit, the external tube control signals of the two external tubes remain unchanged; In addition, when the inner tube control signals of the two inner tubes are disconnection control signals at the same time, outputting the fault-tolerant inner tube control signals to the two inner tubes includes: When the inner tube control signals of the two inner tubes are at the first level at the same time, outputting a first selection signal through the second logic unit; The second selection unit responds to the first selection signal output by the second logic unit, uses the second level as the inner tube control signal of one of the inner tubes, and keeps the inner tube control signal of the other inner tube unchanged, thereby obtaining the fault-tolerant inner tube control signals of the two inner tubes; Correspondingly, when the inner tube control signals of the two inner tubes are not disconnection control signals at the same time, outputting the acquired inner tube control signal to the two inner tubes includes: 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, outputting a second selection signal through the second logic unit; Keeping the inner tube control signals of the two inner tubes unchanged in response to the second selection signal output by the second logic unit by the second selection unit; 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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