Power converter

Abstract

The embodiment of the invention provides a power converter which comprises a control unit, a first capacitor, a second capacitor, a positive direct-current bus, a negative direct-current bus, at least one bridge arm circuit connected between the positive direct-current bus and the negative direct-current bus, and a fault detection circuit corresponding to the bridge arm circuit. A voltage division circuit of the fault detection circuit is connected between a positive DC bus and a negative DC bus, a potential midpoint of the voltage division circuit is connected with a series connection point of a first capacitor and a second capacitor, the voltage division circuit comprises a first potential point and a second potential point, the first potential point is located between the potential midpoint of the voltage division circuit and the positive DC bus, and the second potential point is located between the potential midpoint of the voltage division circuit and the negative DC bus. The second potential point is located between the potential midpoint of the voltage division circuit and the negative DC bus; the control unit is used for controlling the bridge arm circuit to stop working when a real-time comparison result of the voltage of the first potential point, the voltage of the second potential point and the output voltage of the bridge arm circuit is inconsistent with a preset comparison result, fault detection can be carried out on the power converter, and the reliability is high.

Description

Technical Field

[0001] The present application relates to the technical field of electronic power, and particularly to a power converter. Background Art

[0002] As an important component unit for energy conversion, the power converter is widely used in the field of power electronics. Among them, the power converter at least includes a leg circuit, and the conversion of electrical energy can be achieved by controlling the conduction and cutoff of the switching tubes in the leg circuit. During the operation of the power converter, a switching tube failure may occur. At this time, the switching tube failure will cause an incorrect path of the leg current, which may lead to out-of-control leg current and excessive turn-off voltage stress on other non-failed switching tubes, thereby damaging other devices in the leg circuit. Therefore, how to timely identify the failure of the switching tube, avoid the expansion of the failure and affect the normal operation of other devices, is one of the technical problems that need to be solved urgently at present. Summary of the Invention

[0003] The present application provides a power converter, which can perform real-time fault detection on the power converter, avoid abnormal working conditions such as fault diffusion during the operation of the power converter, and improve the reliability of the operation of the power converter.

[0004] The present application provides a power converter, which includes a control unit, a first capacitor, a second capacitor, a positive DC bus, a negative DC bus, at least one arm circuit connected between the positive DC bus and the negative DC bus, and a fault detection circuit corresponding to the arm circuit. The fault detection circuit includes a voltage dividing circuit. The first capacitor and the second capacitor are connected in series between the positive DC bus and the negative DC bus. The voltage dividing circuit is connected between the positive DC bus and the negative DC bus. The potential midpoint of the voltage dividing circuit is connected to the series connection point of the first capacitor and the second capacitor. The voltage dividing circuit includes a first potential point and a second potential point. Among them, the first potential point is located between the potential midpoint of the voltage dividing circuit and the positive DC bus, and the second potential point is located between the potential midpoint of the voltage dividing circuit and the negative DC bus. During the operation of the power converter, the control unit can control the arm circuit to operate in a preset operating state, detect the voltage of the first potential point, the voltage of the second potential point, and the output voltage of the arm circuit, and then compare the voltage of the first potential point with the output voltage of the arm circuit, and compare the voltage of the second potential point with the output voltage of the arm circuit, so as to obtain the real-time comparison result of the voltage of the first potential point, the voltage of the second potential point and the output voltage of the arm circuit. Then, the control unit can compare the real-time comparison result of the voltage of the first potential point, the voltage of the second potential point and the output voltage of the arm circuit with the preset comparison result. When the real-time comparison result of the voltage of the first potential point, the voltage of the second potential point and the output voltage of the arm circuit is inconsistent with the preset comparison result, the control unit controls the arm circuit to stop working. It should be understood that during the operation of the power converter, short-circuit faults may occur in the switching tubes of the arm circuit, which may cause the arm current path of the arm circuit to go wrong, resulting in problems such as out-of-control arm current and excessive turn-off voltage stress on other non-faulty switching tubes in the arm circuit, and also cause the output voltage of the arm circuit to be abnormal. Therefore, when the real-time comparison result of the voltage of the first potential point, the voltage of the second potential point and the output voltage of the arm circuit is inconsistent with the preset comparison result, it can be determined that a switching tube short-circuit fault has occurred in the arm circuit. It can be seen that through the fault detection circuit, the switching tubes are detected in real time during the operation of the power converter, so as to quickly perform protection actions after detecting the switching tube faults, avoid abnormal working conditions such as bus short-circuit and short-circuit fault spread during the operation of the power converter, prevent the switching tubes in the power converter from short-circuiting due to short-circuit conditions, and endanger the equipment safety, thereby improving the reliability of the power converter operation.

[0005] In a possible implementation, the above voltage dividing circuit includes a first resistor, a second resistor, a third resistor, and a fourth resistor connected in series; one end of the first resistor is connected to the positive DC bus, and the connection point between the other end of the first resistor and one end of the second resistor is the first potential point. The connection point between the other end of the second resistor and one end of the third resistor is the potential midpoint. The connection point between the other end of the third resistor and one end of the fourth resistor is the second potential point, and the other end of the fourth resistor is connected to the negative DC bus.

[0006] In this application, the first potential point and the second potential point can divide two reference voltages between the negative bus voltage and the positive bus voltage, that is, the voltage of the first potential point and the voltage of the second potential point. Moreover, the voltage of the first potential point is between the midpoint voltage and the positive bus voltage, and the voltage of the second potential point is between the negative bus voltage and the midpoint voltage. Among them, the potential midpoint of the voltage dividing circuit is connected to the series connection point of the first capacitor and the second capacitor. Therefore, the voltage of the potential midpoint of the voltage dividing circuit is the same as the voltage of the series connection point of the first capacitor and the second capacitor. It can be seen that by comparing the voltage of the first potential point with the output voltage of the bridge arm circuit and comparing the voltage of the second potential point with the output voltage of the bridge arm circuit, the real-time comparison results of the voltage of the first potential point, the voltage of the second potential point, and the output voltage of the bridge arm circuit can be obtained. Furthermore, by comparing the real-time comparison results with the preset comparison results, it can be determined whether the switching tube fails, which has the advantages of fast voltage acquisition speed, simple circuit structure, and low cost.

[0007] In a possible implementation, the above bridge arm circuit may include a first diode, a second diode, a first switching tube, a second switching tube, a third switching tube, and a fourth switching tube. The first switching tube, the second switching tube, the third switching tube, and the fourth switching tube are connected in series between the positive DC bus and the negative DC bus. The anode of the first diode is connected to the cathode of the second diode, the series connection point of the first capacitor and the second capacitor. The cathode of the first diode is connected to the connection end of the first switching tube and the second switching tube. The anode of the second diode is connected to the connection end of the third switching tube and the fourth switching tube. The connection end of the second switching tube and the third switching tube is the output end of the bridge arm circuit.

[0008] In a possible implementation, the above bridge arm circuit includes a first switching tube, a second switching tube, a third switching tube, and a fourth switching tube. The first switching tube and the fourth switching tube are connected in series between the positive DC bus and the negative DC bus, and the connection end of the first switching tube and the fourth switching tube is connected to the series connection point of the first capacitor and the second capacitor through the second switching tube and the third switching tube connected in reverse series. The connection end of the first switching tube and the fourth switching tube is the output end of the bridge arm circuit.

[0009] In a possible implementation manner, the above-mentioned leg circuit includes a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, and a sixth switch tube. The first switch tube, the second switch tube, the third switch tube, and the fourth switch tube are connected in series between the positive DC bus and the negative DC bus. The first end of the fifth switch tube is connected to the connection end of the first switch tube and the second switch tube. The second end of the fifth switch tube is connected to the first end of the sixth switch tube and the series connection point of the first capacitor and the second capacitor. The second end of the sixth switch tube is connected to the connection end of the third switch tube and the fourth switch tube. The connection end of the second switch tube and the third switch tube is the output end of the leg circuit.

[0010] In a possible implementation manner, the above-mentioned leg circuit includes a first switch tube, a second switch tube, a third switch tube, and a fourth switch tube; the preset working state includes a preset switch tube conduction state, and the preset switch tube conduction state includes a first conduction state, a second conduction state, a third conduction state, a fourth conduction state, and a fifth conduction state. Among them, the first conduction state is that the first switch tube and the second switch tube are conducting, and the third switch tube and the fourth switch tube are off; the second conduction state is that the second switch tube and the third switch tube are conducting, and the first switch tube and the fourth switch tube are off; the third conduction state is that the third switch tube and the fourth switch tube are conducting, and the first switch tube and the second switch tube are off; the fourth conduction state is that the second switch tube is conducting, and the first switch tube, the third switch tube, and the fourth switch tube are off; the fifth conduction state is that the third switch tube is conducting, and the first switch tube, the second switch tube, and the fourth switch tube are off. In this application, when the leg circuit operates in the preset switch tube conduction state (that is, the first conduction state, the second conduction state, the third conduction state, the fourth conduction state, and the fifth conduction state) and the switch tubes in the leg circuit do not fail, the output voltage of the leg circuit can be determined. At this time, the output voltage of the leg circuit is the theoretical value. Therefore, if the leg circuit operates in the preset switch tube conduction state and the actual output voltage of the leg circuit should be different from the theoretical output voltage, it can be determined that the switch tubes in the leg circuit have failed. If the actual output voltage of the leg circuit should be the same as the theoretical output voltage, it can be determined that the switch tubes in the leg circuit have not failed, and the accuracy of switch tube fault detection is high.

[0011] In a possible implementation manner, the above preset comparison results include a first preset comparison result, a second preset comparison result, and a third preset comparison result. Among them, the first preset comparison result is that when the bridge arm circuit is in the first conduction state, the voltage of the first potential point is less than the output voltage of the bridge arm circuit and the voltage of the second potential point is less than the output voltage of the bridge arm circuit; the second preset comparison result is that when the bridge arm circuit is in the second conduction state, the voltage of the first potential point is greater than the output voltage of the bridge arm circuit and the voltage of the second potential point is less than the output voltage of the bridge arm circuit; the third preset comparison result is that when the bridge arm circuit is in the third conduction state, the voltage of the first potential point is greater than the output voltage of the bridge arm circuit and the voltage of the second potential point is greater than the output voltage of the bridge arm circuit. In this application, when the bridge arm circuit operates in the first conduction state, the second conduction state, or the third conduction state and the switching tubes in the arm circuit do not fail, the preset comparison results of the voltage of the first potential point, the voltage of the second potential point, and the output voltage of the bridge arm circuit in the corresponding conduction state can be determined. If the real-time comparison results of the voltage of the first potential point, the voltage of the second potential point, and the output voltage of the bridge arm circuit are inconsistent with the preset comparison results, it can be determined that the switching tubes in the bridge arm circuit have failed, and the accuracy of switching tube failure detection is high.

[0012] In a possible implementation manner, the above preset working state further includes the arm current state. The arm current state includes that the arm current direction of the arm circuit is flowing out of the output end of the arm circuit and the arm current direction of the arm circuit is flowing into the output end of the arm circuit. The preset comparison results include the fourth preset comparison result, the fifth preset comparison result, the sixth preset comparison result, and the seventh preset comparison result. Among them, the fourth preset comparison result is that when the arm current state is that the current direction of the arm current is flowing out of the output end of the arm circuit and the preset switch tube conduction state is the fourth conduction state, the voltage of the first potential point is greater than the output voltage of the arm circuit and the voltage of the second potential point is less than the output voltage of the arm circuit. The fifth preset comparison result is that when the arm current state is that the current direction of the arm current is flowing into the output end of the arm circuit and the preset switch tube conduction state is the fourth conduction state, the voltage of the first potential point is less than the output voltage of the arm circuit and the voltage of the second potential point is less than the output voltage of the arm circuit. The sixth preset comparison result is that when the arm current state is that the current direction of the arm current is flowing out of the output end of the arm circuit and the preset switch tube conduction state is the fifth conduction state, the voltage of the first potential point is greater than the output voltage of the arm circuit and the voltage of the second potential point is greater than the output voltage of the arm circuit. The seventh preset comparison result is that when the arm current state is that the current direction of the arm current is flowing into the output end of the arm circuit and the preset switch tube conduction state is the fifth conduction state, the voltage of the first potential point is greater than the output voltage of the arm circuit and the voltage of the second potential point is less than the output voltage of the arm circuit. In this application, since the arm circuit is in a commutation state when working in the fourth conduction state or the fifth conduction state, when a switch tube failure occurs in the arm circuit, it may cause an incorrect arm current path. Therefore, when the arm circuit is working in the fourth conduction state or the fifth conduction state, the switch tube can be detected for failure by combining the current direction of the arm current, and the accuracy is high.

[0013] In a possible implementation manner, the above real-time comparison results include the first comparison result and the second comparison result. The fault detection circuit further includes a comparison circuit. The comparison circuit includes a first comparator and a second comparator. The negative input terminal of the first comparator is connected to the first potential point, the negative input terminal of the second comparator is connected to the second potential point, and the positive input terminals of the first comparator and the second comparator are connected and then connected to the output end of the arm circuit. Among them, the first comparator is used to compare the voltage of the first potential point with the output voltage of the arm circuit and output the first comparison result to the control unit. The second comparator is used to compare the voltage of the second potential point with the output voltage of the arm circuit and output the second comparison result to the control unit. In this application, the first comparator and the second comparator can reflect the actual voltage range of the output voltage of the arm circuit in digital form, which is convenient for observation and comparison, and has a simple structure and is easy to implement.

[0014] In a possible implementation, the above-mentioned fault detection circuit further includes an amplification circuit, which includes a first amplification circuit and a second amplification circuit. The input end of the first amplification circuit is connected to the output end of the first comparator, and the input end of the second amplification circuit is connected to the output end of the second comparator. The first amplification circuit is configured to amplify the comparison result output by the first comparator and then output the first comparison result to the control unit. The second amplification circuit is configured to amplify the comparison result output by the second comparator and then output the second comparison result to the control unit. In this application, the first amplification circuit and the second amplification circuit can amplify the output signals of the first comparator and the second comparator, and reflect the actual voltage range of the output voltage of the bridge arm circuit in digital form, which can improve the reliability and stability of the detection result, and has a simple structure and is easy to implement. Description of the Drawings

[0015] Figure 1 is a schematic diagram of an application scenario of the photovoltaic power generation system provided by this application;

[0016] Figure 2 is another schematic diagram of an application scenario of the photovoltaic power generation system provided by this application;

[0017] Figure 3 is a schematic diagram of a structure of the power converter provided by this application;

[0018] Figure 4 is another schematic diagram of a structure of the power converter provided by this application;

[0019] Figure 5 is another schematic diagram of a structure of the power converter provided by this application;

[0020] Figure 6 is another schematic diagram of a structure of the power converter provided by this application;

[0021] Figure 7 is another schematic diagram of a structure of the power converter provided by this application;

[0022] Figure 8 is another schematic diagram of a structure of the power converter provided by this application;

[0023] Figure 9 is another schematic diagram of a structure of the power converter provided by this application;

[0024] Figure 10 is another schematic diagram of a structure of the power converter provided by this application. Detailed Implementation Modes

[0025] In order to make the objectives, technical solutions and advantages of the present application more clear and understandable, the present application will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0026] Referring to Figure 1 , Figure 1 which is a schematic diagram of an application scenario of the photovoltaic power generation system provided by the present application. The photovoltaic power generation system provided by the present application may include a photovoltaic unit and at least one power converter. Among them, the photovoltaic unit may be a photovoltaic module. Taking the photovoltaic power generation system including multiple power converters as an example, the DC side of the power converter is used to connect the photovoltaic unit, and the AC sides of the power converters are connected in parallel and then used to connect to the power grid or load. The photovoltaic unit can convert light energy into direct current and transmit the direct current to the power converter. The power converter can perform an inversion conversion on the direct current provided by the photovoltaic unit and output the alternating current obtained after the inversion conversion to the power grid or load for power supply.

[0027] In some feasible implementation manners, the photovoltaic power generation system may include a storage battery, and the DC side of each power converter can be used to connect the storage battery. Please refer to Figure 2 , Figure 2 which is another schematic diagram of an application scenario of the photovoltaic power generation system provided by the present application. Among the multiple power converters of the photovoltaic power generation system, the DC sides of some power converters are used to connect the storage battery, and the AC sides of the multiple power converters are connected in parallel and then used to connect to the power grid or load. Each power converter can perform an inversion conversion on the direct current provided by the photovoltaic unit or the storage battery and output the alternating current obtained after the inversion conversion to the power grid or load for power supply.

[0028] In the Figure 1 or Figure 2 application scenario of the photovoltaic power generation system shown, during the operation of the power converter, a situation where a switching tube fails may occur. For example, due to a short circuit of the switching tube, the topology is directly connected, the bus is short-circuited, and the switching tube is damaged due to overcurrent. In order to prevent the failure of the switching tube from spreading and causing damage to other devices, it is necessary to detect the failure of the switching tube in a timely manner during the operation of the power converter, and then quickly perform a protection action when the switching tube fails.

[0029] Referring to Figure 3 , Figure 3 which is a schematic structural diagram of the power converter provided by the present application. As shown in Figure 3As shown, the power converter may include a control unit, a first capacitor C1, a second capacitor C2, a positive DC bus BUS+, a negative DC bus BUS-, at least one arm circuit connected between BUS+ and BUS-, and a fault detection circuit corresponding to the arm circuit. C1 and C2 are connected in series between BUS+ and BUS-. Here, one end of C1 is connected to BUS+, the other end of C1 is connected to one end of C2, and the other end of C2 is connected to BUS-. The connection point where the other end of C1 is connected to one end of C2 is the series connection point of C1 and C2. The series-connected C1 and C2 can divide the voltage between the DC buses into three levels, namely the positive bus voltage, the negative bus voltage, and the voltage at the series connection point of C1 and C2. When the capacitance values of C1 and C2 are equal, the voltage at the series connection point of C1 and C2 is zero voltage, and the series connection point of C1 and C2 can be denoted as the neutral point N.

[0030] See Figure 4 , Figure 4 is another structural schematic diagram of the power converter provided by this application. As Figure 4 shown, the fault detection circuit may include a voltage dividing circuit. The voltage dividing circuit is connected between BUS+ and BUS-, and the potential midpoint of the voltage dividing circuit is connected to the series connection point of C1 and C2. Here, the voltage at the potential midpoint of the voltage dividing circuit is equal to the voltage at the series connection point of C1 and C2, that is, zero voltage. The voltage dividing circuit may include a first potential point and a second potential point. The first potential point is located between the potential midpoint of the voltage dividing circuit and BUS+, and the second potential point is located between the potential midpoint of the voltage dividing circuit and BUS-. In other words, the voltage of the first potential point (denoted as V1) is in the range from zero voltage to the positive bus voltage, and the voltage of the second potential point (denoted as V2) is in the range from zero voltage to the negative bus voltage. It can be seen that V1 and V2 divided by the voltage dividing circuit can divide at least four voltage intervals in the voltage range from the negative bus voltage to the positive bus voltage, namely the negative bus voltage to V2, V2 to zero voltage, zero voltage to V1, and V1 to the positive bus voltage.

[0031] It should be understood that during the operation of the power converter, short - circuit faults may occur in the switching transistors of the arm circuit, which may lead to incorrect arm - current paths in the arm circuit, resulting in out - of - control arm currents and excessive turn - off voltage stress on other non - faulty switching transistors in the arm circuit. Therefore, it is necessary to detect whether the switching transistors in the power converter are normal to prevent short - circuit faults caused by short - circuit conditions in the switching transistors, which may endanger the safety of the equipment. Also, because the output voltage of the arm circuit is different under different preset operating states, it is possible to detect whether there are faults in the switching transistors in the arm circuit by comparing the theoretical value and the actual value of the output voltage of the arm circuit under this preset operating state. Specifically, during the operation of the power converter, the control unit can control the arm circuit to operate in a preset operating state. At this time, the control unit can detect V1, V2, and the output voltage of the arm circuit. By comparing the magnitudes of V1 and the output voltage of the arm circuit, and the magnitudes of V2 and the output voltage of the arm circuit, the voltage range to which the output voltage of the arm circuit belongs can be determined, that is, the real - time comparison results of V1, V2, and the output voltage of the arm circuit can be obtained. When the real - time comparison result is inconsistent with the preset comparison result, the arm circuit can be controlled to stop working. Among them, the preset comparison result is the comparison result of the voltage at the first potential point, the voltage at the second potential point, and the output voltage of the arm circuit when the arm circuit is in the preset operating state. It can be seen that through the fault - detection circuit, the faulty switching transistors can be detected in real time during the operation of the power converter, and rapid protection actions can be taken after detecting the switching - transistor faults, avoiding serious faults such as bus - bar short - circuits and short - circuit - fault propagation caused by switching - transistor faults during the operation of the power converter, which may endanger the safety of the equipment, thereby improving the reliability of the operation of the power converter.

[0032] In some feasible embodiments, as Figure 4 shown, the arm circuit may include a first diode D11, a second diode D21, a first switching transistor Q11, a second switching transistor Q12, a third switching transistor Q13, and a fourth switching transistor Q14. Q11, Q12, Q13, and Q14 are connected in series between BUS+ and BUS-. The anode of D11 is connected to the cathode of D21, the series - connection point of C1 and C2. The cathode of D11 is connected to the connection terminal of Q11 and Q12. The anode of D21 is connected to the connection terminal of Q13 and Q14. The connection terminal of Q12 and Q13 is the output terminal O of the arm circuit, and the voltage at the output terminal O is the output voltage of the arm circuit.

[0033] In some feasible embodiments, the above-mentioned preset operating state may include a preset switch - tube conduction state. During the operation of the power converter, the control unit can control the conduction or cut - off of Q11, Q12, Q13, and Q14 in the bridge - arm circuit, so that the bridge - arm circuit operates in different preset switch - tube conduction states, thereby controlling the output voltage of the bridge - arm circuit to be different. And the series connection point of C1 and C2 is connected to the potential mid - point of the voltage - dividing circuit, the anode of D11, and the cathode of D21. That is, one bridge - arm circuit corresponds to one voltage - dividing circuit. Therefore, whether there is a switch - tube fault in the bridge - arm circuit is detected through the voltage - dividing circuit corresponding to the bridge - arm circuit. In other words, whether there is a fault in the above - mentioned bridge - arm circuit can be detected by comparing the real - time comparison result of V1, V2 with the output voltage of the bridge - arm circuit with the preset comparison result.

[0034] In some feasible embodiments, the above - mentioned preset switch - tube conduction state may include a first conduction state, a second conduction state, a third conduction state, a fourth conduction state, and a fifth conduction state. Specifically, the preset switch - tube conduction state can be seen in the following table.

[0035]

[0036] Table 1

[0037] As shown in Table 1, "1" represents that the switch - tube is conducting, and "0" represents that the switch - tube is cut - off. Then, the first conduction state can be recorded as 1100, at this time Q11 and Q12 are conducting, and Q13 and Q14 are cut - off; the second conduction state can be recorded as 0110, at this time Q12 and Q13 are conducting, and Q11 and Q14 are cut - off; the third conduction state can be recorded as 0011, at this time Q13 and Q14 are conducting, and Q11 and the second switch - tube Q12 are cut - off; the fourth conduction state can be recorded as 0100, at this time Q12 is conducting, and Q11, Q13, and Q14 are cut - off; the fifth conduction state can be recorded as 0010, at this time Q13 is conducting, and Q11, Q12, and Q14 are cut - off.

[0038] In some feasible embodiments, when the preset working state includes the preset conduction state of the switch tube, the preset comparison result may include a first preset comparison result, a second preset comparison result, and a third preset comparison result. In some feasible embodiments, the above-mentioned preset working state may further include the arm current state, and the arm current state may include the direction of the arm current of the arm circuit flowing out of the output terminal of the arm circuit and the direction of the arm current of the arm circuit flowing into the output terminal of the arm circuit. At this time, the preset comparison result may include a fourth preset comparison result, a fifth preset comparison result, a sixth preset comparison result, and a seventh preset comparison result. Specifically, the preset comparison result can be seen in Table 2. BIT1 may represent the comparison result between V1 and the output voltage of the arm circuit, and BIT2 may represent the comparison result between V2 and the output voltage of the arm circuit. Among them, both BIT1 and BIT2 include a high level 1 and a low level 0. For example, BIT1 = 1 may indicate that V1 is less than the output voltage of the arm circuit. At this time, BIT1 = 0 can indicate that V1 is greater than the output voltage of the arm circuit. BIT2 = 1 may indicate that V2 is less than the output voltage of the arm circuit. At this time, BIT2 = 0 can indicate that V2 is greater than the output voltage of the arm circuit. Or, BIT1 = 0 may indicate that V1 is less than the output voltage of the arm circuit. At this time, BIT1 = 1 can indicate that V1 is greater than the output voltage of the arm circuit. BIT2 = 0 may indicate that V2 is less than the output voltage of the arm circuit. At this time, BIT2 = 1 can indicate that V2 is greater than the output voltage of the arm circuit. The specific meanings represented by BIT1 being 1 or 0 and BIT2 being 1 or 0 can be determined according to the actual application scenario, and the present application does not limit this here. For the convenience of description, in the embodiments of the present application, it is taken as an example that BIT1 = 1 indicates that V1 is less than the output voltage of the arm circuit, BIT1 = 0 indicates that V1 is greater than the output voltage of the arm circuit, and BIT2 = 1 indicates that V2 is less than the output voltage of the arm circuit, and BIT2 = 0 indicates that V2 is greater than the output voltage of the arm circuit, and will not be elaborated hereinafter. In addition, for the convenience of description, the direction in which the arm current flows out of the output terminal of the arm circuit can be recorded as positive, and the direction in which the arm current flows into the output terminal of the arm circuit can be recorded as negative.

[0039]

[0040] Table 2

[0041] Combined with Table 1 and Table 2, it can be seen that when the bridge arm circuit is in the first conduction state 1100, the output voltage of the bridge arm circuit is the positive bus voltage. Also, since V1 is between zero voltage and the positive bus voltage, and V2 is between the negative bus voltage and zero voltage, when there is no switch tube failure in the bridge arm circuit, V1 should be less than the output voltage of the bridge arm circuit, and V2 should be less than the output voltage of the bridge arm circuit. At this time, the preset comparison result is the first preset comparison result, and the first preset comparison result is that V1 is less than the output voltage of the bridge arm circuit and V2 is less than the output voltage of the bridge arm circuit, that is, BIT1 = 1, BIT2 = 1. Thus, it can be seen that when the real-time comparison result of V1 and V2 with the output voltage of the bridge arm circuit is inconsistent with the preset comparison result, it can be determined that there is a switch tube failure in the bridge arm circuit. For example, when V1 is less than the output voltage of the bridge arm circuit and V2 is greater than the output voltage of the bridge arm circuit, or, V1 is greater than the output voltage of the bridge arm circuit and V2 is greater than the output voltage of the bridge arm circuit, or, V1 is greater than the output voltage of the bridge arm circuit and V2 is less than the output voltage of the bridge arm circuit, it can be determined that there is a switch tube failure in the bridge arm circuit.

[0042] Similarly, when the bridge arm circuit is in the second conduction state 0110, the output voltage of the bridge arm circuit is zero voltage. Also, since V1 is between zero voltage and the positive bus voltage, and V2 is between the negative bus voltage and zero voltage, when there is no switch tube failure in the bridge arm circuit, V1 should be greater than the output voltage of the bridge arm circuit, and V2 should be less than the output voltage of the bridge arm circuit. At this time, the preset comparison result is the second preset comparison result, and the second preset comparison result is that V1 is greater than the output voltage of the bridge arm circuit and V2 is less than the output voltage of the bridge arm circuit, that is, BIT1 = 0, BIT2 = 1. Thus, it can be seen that when the real-time comparison result of V1 and V2 with the output voltage of the bridge arm circuit is inconsistent with the preset comparison result, it can be determined that there is a switch tube failure in the bridge arm circuit. For example, when V1 is less than the output voltage of the bridge arm circuit and V2 is greater than the output voltage of the bridge arm circuit, or, V1 is less than the output voltage of the bridge arm circuit and V2 is less than the output voltage of the bridge arm circuit, or, V1 is greater than the output voltage of the bridge arm circuit and V2 is greater than the output voltage of the bridge arm circuit, it can be determined that there is a switch tube failure in the bridge arm circuit.

[0043] Similarly, when the leg circuit is in the third conduction state 0011, the output voltage of the leg circuit is the negative bus voltage. Also, since V1 is between the zero voltage and the positive bus voltage, and V2 is between the negative bus voltage and the zero voltage, when there is no switch tube fault in the leg circuit, V1 should be greater than the output voltage of the leg circuit, and V2 should be greater than the output voltage of the leg circuit. At this time, the preset comparison result is the third preset comparison result, and the third preset comparison result is that V1 is greater than the output voltage of the leg circuit and V2 is greater than the output voltage of the leg circuit, that is, BIT1 = 0, BIT2 = 0. Thus, when the real-time comparison result of V1 and V2 with the output voltage of the leg circuit is inconsistent with the preset comparison result, it can be determined that there is a switch tube fault in the leg circuit. For example, when V1 is less than the output voltage of the leg circuit and V2 is greater than the output voltage of the leg circuit, or V1 is less than the output voltage of the leg circuit and V2 is less than the output voltage of the leg circuit, or V1 is greater than the output voltage of the leg circuit and V2 is less than the output voltage of the leg circuit, it can be determined that there is a switch tube fault in the leg circuit.

[0044] Similarly, when the leg circuit is in the fourth conduction state 0100 and the current direction of the leg current is positive, the output voltage of the leg circuit is the zero voltage. Also, since V1 is between the zero voltage and the positive bus voltage, and V2 is between the negative bus voltage and the zero voltage, when there is no switch tube fault in the leg circuit, V1 should be greater than the output voltage of the leg circuit, and V2 should be less than the output voltage of the leg circuit. At this time, the preset comparison result is the fourth preset comparison result, and the fourth preset comparison result is that V1 is greater than the output voltage of the leg circuit and V2 is less than the output voltage of the leg circuit, that is, BIT1 = 0, BIT2 = 1. Thus, when the real-time comparison result of V1 and V2 with the output voltage of the leg circuit is inconsistent with the preset comparison result, it can be determined that there is a switch tube fault in the leg circuit. For example, when V1 is less than the output voltage of the leg circuit and V2 is greater than the output voltage of the leg circuit, or V1 is less than the output voltage of the leg circuit and V2 is less than the output voltage of the leg circuit, or V1 is greater than the output voltage of the leg circuit and V2 is greater than the output voltage of the leg circuit, it can be determined that there is a switch tube fault in the leg circuit.

[0045] Similarly, when the arm circuit is in the fourth conduction state 0100 and the current direction of the arm current is negative, the output voltage of the arm circuit is the positive bus voltage. Also, since V1 is between zero voltage and the positive bus voltage, and V2 is between the negative bus voltage and zero voltage, when there is no switch tube fault in the arm circuit, V1 should be less than the output voltage of the arm circuit, and V2 should be less than the output voltage of the arm circuit. At this time, the preset comparison result is the fifth preset comparison result, and the fifth preset comparison result is that V1 is less than the output voltage of the arm circuit and V2 is less than the output voltage of the arm circuit, that is, BIT1 = 1, BIT2 = 1. Thus, it can be seen that when the real-time comparison result of V1 and V2 with the output voltage of the arm circuit is inconsistent with the preset comparison result, it can be determined that there is a switch tube fault in the arm circuit. For example, when V1 should be less than the output voltage of the arm circuit and V2 should be greater than the output voltage of the arm circuit, or, V1 should be greater than the output voltage of the arm circuit and V2 should be greater than the output voltage of the arm circuit, or, V1 should be greater than the output voltage of the arm circuit and V2 should be less than the output voltage of the arm circuit, it can be determined that there is a switch tube fault in the arm circuit.

[0046] Similarly, when the arm circuit is in the fifth conduction state 0010 and the current direction of the arm current is positive, the output voltage of the arm circuit is the negative bus voltage. Also, since V1 is between zero voltage and the positive bus voltage, and V2 is between the negative bus voltage and zero voltage, when there is no switch tube fault in the arm circuit, V1 should be greater than the output voltage of the arm circuit, and V2 should be greater than the output voltage of the arm circuit. At this time, the preset comparison result is the sixth preset comparison result, and the sixth preset comparison result is that V1 is greater than the output voltage of the arm circuit and V2 is greater than the output voltage of the arm circuit, that is, BIT1 = 0, BIT2 = 0. Thus, it can be seen that when the real-time comparison result of V1 and V2 with the output voltage of the arm circuit is inconsistent with the preset comparison result, it can be determined that there is a switch tube fault in the arm circuit. For example, when V1 is less than the output voltage of the arm circuit and V2 is greater than the output voltage of the arm circuit, or, V1 is less than the output voltage of the arm circuit and V2 is less than the output voltage of the arm circuit, or, V1 is greater than the output voltage of the arm circuit and V2 is less than the output voltage of the arm circuit, it can be determined that there is a switch tube fault in the arm circuit.

[0047] Similarly, when the arm circuit is in the fifth conduction state 0010 and the current direction of the arm current is negative, the output voltage of the arm circuit is zero voltage. Also, since V1 is between zero voltage and the positive bus voltage, and V2 is between the negative bus voltage and zero voltage, when there is no switch tube fault in the arm circuit, V1 should be greater than the output voltage of the arm circuit, and V2 should be less than the output voltage of the arm circuit. At this time, the preset comparison result is the seventh preset comparison result, which is that V1 is greater than the output voltage of the arm circuit and V2 is less than the output voltage of the arm circuit, that is, BIT1 = 0 and BIT2 = 1. Thus, when the real-time comparison result of V1 and V2 with the output voltage of the arm circuit is inconsistent with the preset comparison result, it can be determined that there is a switch tube fault in the arm circuit. For example, when V1 is less than the output voltage of the arm circuit and V2 is greater than the output voltage of the arm circuit, or, V1 is less than the output voltage of the arm circuit and V2 is less than the output voltage of the arm circuit, or, V1 is greater than the output voltage of the arm circuit and V2 is greater than the output voltage of the arm circuit, it can be determined that there is a switch tube fault in the arm circuit.

[0048] It should be understood that when the arm circuit operates in the first conduction state, the second conduction state, and the third conduction state and there is no fault in the switch tubes in the arm circuit, the theoretical value of the output voltage of the arm circuit can be determined in advance, and then by comparing the magnitudes of V1 and V2 with the theoretical value, the preset comparison results in each conduction state can be obtained, that is, the first preset comparison result, the second preset comparison result, and the third preset comparison result. When the arm circuit operates in the fourth conduction state and the fifth conduction state, the fourth preset comparison result, the fifth preset comparison result, the sixth preset comparison result, and the seventh preset comparison result can be obtained by comparing the magnitudes of V1 and V2 with the theoretical value and the arm current state. Further, during the operation of the power converter, the output voltage of the arm circuit can be detected in real time, and by comparing the magnitudes of V1 and V2 with the output voltage of the arm circuit, the real-time comparison result can be obtained. Then, whether there is a switch tube fault in the arm circuit can be judged through the real-time comparison result of V1 and V2 with the output voltage of the arm circuit and the preset comparison result, which has the advantages of fast detection speed and fast fault judgment.

[0049] In some feasible embodiments, the voltage dividing circuit includes at least four voltage dividing resistors to divide two reference voltages, namely V1 and V2, between the negative bus voltage and the positive bus voltage. Specifically, as Figure 4As shown, the voltage dividing circuit may include a first resistor R11, a second resistor R12, a third resistor R13, and a fourth resistor R14 connected in series. Here, one end of R11 is connected to BUS+, and the connection point between the other end of R11 and one end of R12 is the first potential point. The connection point between the other end of R12 and one end of R13 is the potential midpoint. The connection point between the other end of R13 and one end of R14 is the second potential point. The other end of R14 is connected to BUS-. Among them, the potential midpoint of the voltage dividing circuit is connected to the series connection point of C1 and C2. Therefore, it can be known that the voltage at the potential midpoint is the same as the voltage at the series connection point of C1 and C2, that is, zero voltage. It should be understood that through R11, R12, R13, and R14, two reference voltages, namely V1 and V2, can be divided between the negative bus voltage and the positive bus voltage. The voltage at the potential midpoint of the voltage dividing circuit is zero voltage. Therefore, V1 is within the range from zero voltage to the positive bus voltage, and the second potential point is located between the potential midpoint of the voltage dividing circuit and BUS-. V2 is within the range from zero voltage to the negative bus voltage. Thus, it can be seen that the two reference voltages divided by the voltage dividing circuit can divide at least 4 voltage intervals within the range from the negative bus voltage to the positive bus voltage, namely from the negative bus voltage to V2, from V2 to zero voltage, from zero voltage to V1, and from V1 to the positive bus voltage. It can be seen that by comparing V1 with the output voltage of the bridge arm circuit and comparing V2 with the output voltage of the bridge arm circuit, the real-time comparison results of V1, V2, and the output voltage of the bridge arm circuit can be obtained, such as the voltage interval where the output voltage of the bridge arm circuit is located. Furthermore, by comparing the real-time comparison results with the preset comparison results, it can be determined whether the switching tube fails, which has the advantages of fast voltage acquisition speed, simple circuit structure, and low cost.

[0050] Optionally, when the resistance values of R11, R12, R13, and R14 are equal, the voltage dividing circuit can divide the bus voltage into four equal parts. At this time, V2 is 1 / 2 of the negative bus voltage, and V1 is 1 / 2 of the positive bus voltage.

[0051] Optionally, the above Figure 4 The four voltage dividing resistors shown can be replaced by four capacitors. For example, R11, R12, R13, and R14 can also be replaced by a third capacitor, a fourth capacitor, a fifth capacitor, and a sixth capacitor respectively to divide two reference voltages, namely V1 and V2, between the negative bus voltage and the positive bus voltage. Optionally, when the capacitance values of the third capacitor, the fourth capacitor, the fifth capacitor, and the sixth capacitor are equal, the voltage dividing circuit can divide the bus voltage into four equal parts. At this time, V2 is 1 / 2 of the negative bus voltage, and V1 is 1 / 2 of the positive bus voltage.

[0052] Refer to Figure 5 , Figure 5 which is another structural schematic diagram of the power converter provided by this application. As Figure 5As shown, based on the voltage division circuit, the fault detection circuit may further include a comparison circuit. The comparison circuit may include a first comparator P11 and a second comparator P12. The negative input terminal of P11 is connected to the first potential point, the negative input terminal of P12 is connected to the second potential point, and after the positive input terminals of P11 and P12 are connected, they are connected to the output terminal O of the bridge arm circuit. In some feasible embodiments, the negative input terminal of P11 may be connected to the first potential point through a fifth resistor R2, the negative input terminal of P12 may be connected to the second potential point through a sixth resistor R3, and after the positive input terminals of P11 and P12 are connected, they may be connected to the output terminal O of the bridge arm circuit through a seventh resistor R4. Here, R2, R3, and R4 can protect the circuits of P11 and P12, avoiding excessive V1 and V2 from damaging the components in the comparison circuit. The real-time comparison results may include a first comparison result and a second comparison result. The first comparison result may be used to represent the comparison result between V1 and the output voltage of the bridge arm circuit, and the second comparison result may be used to represent the comparison result between V2 and the output voltage of the bridge arm circuit. P11 can compare the magnitudes of V1 and the output voltage of the bridge arm circuit and output the first comparison result to the control unit, and P12 can compare the magnitudes of V2 and the output voltage of the bridge arm circuit and output the second comparison result to the control unit.

[0053] Among them, the first comparison result output by P11 to the control unit may include a first comparison signal (such as the above-mentioned BIT1), and the second comparison result output by P12 to the control unit may include a second comparison signal (such as the above-mentioned BIT2). Both BIT1 and BIT2 include a high level 1 and a low level 0. For example, BIT1 = 1 may indicate that V1 is less than the output voltage of the bridge arm circuit. At this time, BIT1 = 0, that is, it indicates that V1 is greater than the output voltage of the bridge arm circuit. BIT2 = 1 may indicate that V2 is less than the output voltage of the bridge arm circuit. At this time, BIT2 = 0, that is, it indicates that V2 is greater than the output voltage of the bridge arm circuit.

[0054] Furthermore, the control unit can compare the first comparison result, the second comparison result with the preset comparison result of the bridge arm circuit in the preset working state. When the first comparison result, the second comparison result are inconsistent with the preset comparison result of the bridge arm circuit in the preset working state, the control unit can control the bridge arm circuit to stop working. Specifically, referring to Table 1 and Table 2, when the bridge arm circuit is in the first conduction state 1100, the output voltage of the bridge arm circuit is the positive bus voltage. When V1 is less than the output voltage of the bridge arm circuit and V2 is less than the output voltage of the bridge arm circuit, it can be determined that there is no switch tube fault in the bridge arm circuit, otherwise the control unit controls the arm circuit to stop working. In other words, BIT1 = 1 output by P11 and BIT2 = 1 output by P12, that is, the first comparison result is that V1 is less than the output voltage of the bridge arm circuit and the second comparison result is that V2 is less than the output voltage of the bridge arm circuit. At this time, it can be determined that there is no switch tube fault in the bridge arm circuit, otherwise the control unit controls the arm circuit to stop working.

[0055] Similarly, when the arm circuit is in the second conduction state 0110, the output voltage of the arm circuit is zero voltage. When V1 is greater than the output voltage of the arm circuit and V2 is less than the output voltage of the arm circuit, it can be determined that there is no switch tube fault in the arm circuit; otherwise, the control unit controls the arm circuit to stop working. In other words, BIT1 output by P11 = 0, and BIT2 output by P12 = 1, that is, the second preset comparison result is that V1 is greater than the output voltage of the arm circuit and V2 is less than the output voltage of the arm circuit. At this time, it can be determined that there is no switch tube fault in the arm circuit; otherwise, the control unit controls the arm circuit to stop working.

[0056] Similarly, when the arm circuit is in the third conduction state 0011, the output voltage of the arm circuit is the negative bus voltage. When V1 is greater than the output voltage of the arm circuit and V2 is greater than the output voltage of the arm circuit, it can be determined that there is no switch tube fault in the arm circuit; otherwise, the control unit controls the arm circuit to stop working. In other words, BIT1 output by P11 = 0, and BIT2 output by P12 = 0, that is, the third preset comparison result is that V1 is greater than the output voltage of the arm circuit and V2 is greater than the output voltage of the arm circuit. At this time, it can be determined that there is no switch tube fault in the arm circuit; otherwise, the control unit controls the arm circuit to stop working.

[0057] Similarly, when the arm circuit is in the fourth conduction state 0100 and the current direction of the arm current is positive, the output voltage of the arm circuit is zero voltage. When V1 is greater than the output voltage of the arm circuit and V2 is less than the output voltage of the arm circuit, it can be determined that there is no switch tube fault in the arm circuit; otherwise, the control unit controls the arm circuit to stop working. In other words, BIT1 output by P11 = 0, and BIT2 = 1, that is, the fourth preset comparison result is that V1 is greater than the output voltage of the arm circuit and V2 is less than the output voltage of the arm circuit. At this time, it can be determined that there is no switch tube fault in the arm circuit; otherwise, the control unit controls the arm circuit to stop working.

[0058] Similarly, when the arm circuit is in the fourth conduction state 0100 and the current direction of the arm current is negative, the output voltage of the arm circuit is the positive bus voltage. When V1 is less than the output voltage of the arm circuit and V2 is less than the output voltage of the arm circuit, it can be determined that there is no switch tube fault in the arm circuit; otherwise, the control unit controls the arm circuit to stop working. In other words, BIT1 output by P11 = 1, and BIT2 = 1, that is, the fifth preset comparison result is that V1 is less than the output voltage of the arm circuit and V2 is less than the output voltage of the arm circuit. At this time, it can be determined that there is no switch tube fault in the arm circuit; otherwise, the control unit controls the arm circuit to stop working.

[0059] Similarly, when the arm circuit is in the fifth conduction state 0010 and the current direction of the arm current is positive, the output voltage of the arm circuit is the negative bus voltage. When V1 is greater than the output voltage of the arm circuit and V2 is greater than the output voltage of the arm circuit, it can be determined that there is no switch tube fault in the arm circuit; otherwise, the control unit controls the arm circuit to stop working. In other words, BIT1 = 0 and BIT2 = 0 are output by P11, that is, the sixth preset comparison result is that V1 is greater than the output voltage of the arm circuit and V2 is greater than the output voltage of the arm circuit. At this time, it can be determined that there is no switch tube fault in the arm circuit; otherwise, the control unit controls the arm circuit to stop working.

[0060] Similarly, when the arm circuit is in the fifth conduction state 0010 and the current direction of the arm current is negative, the output voltage of the arm circuit is zero voltage. When V1 is greater than the output voltage of the arm circuit and V2 is less than the output voltage of the arm circuit, it can be determined that there is no switch tube fault in the arm circuit; otherwise, the control unit controls the arm circuit to stop working. In other words, BIT1 = 0 and BIT2 = 1 are output by P11, that is, the seventh preset comparison result is that V1 is greater than the output voltage of the arm circuit and V2 is less than the output voltage of the arm circuit. At this time, it can be determined that there is no switch tube fault in the arm circuit; otherwise, the control unit controls the arm circuit to stop working.

[0061] It should be understood that P11 can receive V1 output by the voltage dividing circuit and the output voltage of the arm circuit, and output the comparison result of V1 and the output voltage of the arm circuit in digital form, that is, the first comparison signal. P12 can receive V2 output by the voltage dividing circuit and the output voltage of the arm circuit, and output the comparison result of V2 and the output voltage of the arm circuit in digital form, that is, the second comparison signal. It can be seen that through P11 and P12, the actual voltage range of the output voltage of the arm circuit can be reflected in digital form, which is convenient for observation and comparison, and has a simple structure and is easy to implement.

[0062] See Figure 5 , on the basis of the above voltage dividing circuit and comparison circuit, the fault detection circuit may further include an amplification circuit. The amplification circuit includes a first amplification circuit and a second amplification circuit. The input end of the first amplification circuit is connected to the output end of P11, and the input end of the second amplification circuit is connected to the output end of P12. The first amplification circuit can amplify the comparison result output by P11 and then output the first comparison result to the control unit. The second amplification circuit can amplify the comparison result output by P12 and then output the second comparison result to the control unit.

[0063] It should be understood that the comparison result output by P11 to the first amplifier circuit may include a first comparison signal (such as the above-mentioned BIT1). The first amplifier circuit can amplify BIT1 and then output the first comparison result to the control unit. The comparison result output by P12 to the second amplifier circuit may include a second comparison signal (such as the above-mentioned BIT2). The second amplifier circuit can amplify BIT2 and then output the second comparison result to the control unit. Both BIT1 and BIT2 include a high level 1 and a low level 0. For example, BIT1 = 1 can indicate that V1 is less than the output voltage of the bridge arm circuit. At this time, BIT1 = 0, which means that V1 is greater than the output voltage of the bridge arm circuit. BIT2 = 1 can indicate that V2 is less than the output voltage of the bridge arm circuit. At this time, BIT2 = 0, which means that V2 is greater than the output voltage of the bridge arm circuit. Further, the control unit can compare the first comparison result and the second comparison result with the preset comparison result of the bridge arm circuit in the preset working state. When the first comparison result and the second comparison result are inconsistent with the preset comparison result of the bridge arm circuit in the preset working state, the bridge arm circuit can be controlled to stop working.

[0064] It should be understood that the first amplifier circuit and the second amplifier circuit can respectively amplify the comparison results output by P11 and P12 and output BIT1 and BIT2 in digital form. It can be seen that through the first amplifier circuit and the second amplifier circuit, the output signals of P11 and P12 can be amplified, and the actual voltage range of the output voltage of the bridge arm circuit can be reflected in digital form, which can improve the reliability and stability of the detection result, and has a simple structure and is easy to implement.

[0065] In some feasible embodiments, the first amplifier circuit and the second amplifier circuit may include a push-pull circuit. The first amplifier circuit may include a first triode S11 and a second triode S12. The collector of S11 is connected to the power supply. The bases of S11 and S12 are connected and then connected to the output terminal of P11 through an eighth resistor R5. The emitters of S11 and S12 are connected and then grounded through a series of a ninth resistor R6 and a tenth resistor R7. The collector of S12 is grounded. Similarly, the second amplifier circuit may include a third triode S13 and a fourth triode S14. The collector of S13 is connected to the power supply. The bases of S13 and S14 are connected and then connected to the output terminal of P12 through an eleventh resistor R8. The emitters of S13 and S14 are connected and then grounded through a series of a twelfth resistor R9 and a thirteenth resistor R10. The collector of S14 is grounded.

[0066] In some other feasible embodiments, the above triode can be replaced by a transistor, such as a field effect transistor (FET). Specifically, the first amplifying circuit may include a first transistor and a second transistor. The drain of the first transistor is connected to the power supply. After the gates of the first transistor and the second transistor are connected, they are connected to the output terminal of P11 through R5. After the sources of the first transistor and the second transistor are connected, they are grounded through the series-connected R6 and R7. The drain of the second transistor is grounded. Similarly, the second amplifying circuit may include a third transistor and a fourth transistor. The drain of the third transistor is connected to the power supply. After the gates of the third transistor and the fourth transistor are connected, they are connected to the output terminal of P12 through R8. After the sources of the third transistor and the fourth transistor are connected, they are grounded through the series-connected R9 and R10. The drain of the fourth transistor is grounded.

[0067] In this embodiment, when the leg circuit operates in different preset operating states, the fault detection circuit can divide two reference voltages between the negative bus voltage and the positive bus voltage, that is, the voltage of the first potential point and the voltage of the second potential point. The control unit can detect whether there is a short-circuit fault in the leg circuit by comparing the real-time comparison results of the voltage of the first potential point, the voltage of the second potential point and the output voltage of the leg circuit with the preset comparison results. Furthermore, when a fault is detected, the control unit can block the waves of each switching tube in the leg circuit, that is, stop sending waves to each switching tube in the leg circuit, control each switching tube to turn off, so as to protect the leg circuit and further protect the power converter. The power converter provided by the present application not only has a simple hardware circuit structure, small detection delay, but also has a simple and efficient detection logic, and the detection result is accurate and reliable.

[0068] It should be understood that the circuit structure of the leg circuit in the power converter can be various. The following is an exemplary illustration of it, but it is not a specific limitation to it. In some feasible embodiments, refer to Figure 6 , Figure 6 is another structural schematic diagram of the power converter provided by the present application. As Figure 6As shown, Q11 and Q14 of the leg circuit are connected in series between BUS+ and BUS-, and the connection terminals of Q11 and Q14 are connected to the series connection point of C1 and C2 through Q12 and Q13 connected in reverse series. The connection terminals of Q11 and Q14 are the output terminals O of the leg circuit, and the voltage at the output terminal O is the output voltage of the leg circuit. Here, the reverse series connection of Q12 and Q13 means that the directions of the diodes connected in parallel with Q12 and Q13 are opposite. In other words, the current conduction directions of the diodes connected in parallel with Q12 and Q13 are opposite. The diodes connected in parallel with Q12 and Q13 can be the body diodes included in Q12 and Q13. For example, the diode connected in parallel with Q12 can conduct the current flowing from the connection terminals of Q11 and Q14 to the connection terminals of C1 and C2, while the diode connected in parallel with Q13 can conduct the current flowing from the connection terminals of C1 and C2 to the connection terminals of Q11 and Q14. Here, among the reverse series-connected Q12 and Q13, it can be that Q13 is connected to the connection terminals of C1 and C2, or Q12 is connected to the connection terminals of C1 and C2. In the embodiment of the present application, it is taken that Q13 is connected to the connection terminals of C1 and C2 as an example, and details will not be described hereinafter.

[0069] In the specific implementation, as Figure 6 shown, the connection point between the other end of R11 and one end of R12 of the voltage dividing circuit is the first potential point, the connection point between the other end of R12 and one end of R13 is the potential midpoint, and the connection point between the other end of R13 and one end of R14 is the second potential point. The above first potential point and second potential point can divide two reference voltages, namely V1 and V2, between the negative bus voltage and the positive bus voltage. The connection terminals of Q11 and Q14 are connected to the series connection point of C1 and C2 through Q12 and Q13 connected in reverse series, and the series connection point of C1 and C2 is also connected to the potential midpoint of the voltage dividing circuit. It can be seen that one leg circuit corresponds to one voltage dividing circuit. Therefore, it is possible to detect whether there is a switch tube fault in the leg circuit through the voltage dividing circuit corresponding to the leg circuit, that is, by comparing the magnitudes of V1 and the output voltage of the leg circuit, and the magnitudes of V2 and the output voltage of the leg circuit, to determine the voltage range to which the output voltage of the leg circuit belongs, that is, to obtain the real-time comparison result of V1, V2 and the output voltage of the leg circuit. When the real-time comparison result is inconsistent with the preset comparison result, it is determined whether there is a switch tube fault in the leg circuit. Among them, the preset comparison result can be seen in Table 2, and specific details can be seen in Figure 5 the corresponding embodiment, which will not be elaborated here. It should be understood that in Figure 5 the corresponding embodiment, the implementation manners corresponding to the voltage dividing circuit, the comparison circuit and the amplification circuit in the fault detection circuit are still applicable to Figure 6 the power converter shown in Figure 6 and Figure 4 , Figure 4The shown leg circuit has a long commutation path and a short commutation path. The number of conducting switching devices in the long commutation path is more than that in the short commutation path. Therefore, when switching from the long commutation path to the short commutation path, the switching devices will be turned off. At this time, the rapidly changing current will result in a relatively large stray inductance, such as the equivalent inductance presented by conductors in the circuit (such as connecting wires, component leads, component bodies, etc.). The induced voltage generated by the stray inductance will be superimposed on the bus voltage, causing a voltage spike when the switching device is turned off, thereby leading to excessive stress on the switching device and increasing the loss of the switching device. Figure 6 The shown leg circuit can change the long commutation loop into a short commutation loop, so the circuit loss can be reduced and the working efficiency can be improved.

[0070] In some other feasible embodiments, for the circuit structure of the leg circuit in the power converter, reference can also be made to Figure 7 , Figure 7 which is another schematic structural diagram of the power converter provided by this application. As Figure 7 shown, the leg circuit may include Q11, Q12, Q13, Q14, the fifth switching device T11, and the sixth switching device T21. Q11, Q12, Q13, and Q14 are connected in series between BUS+ and BUS-. The first end of T11 is connected to the connection point of Q11 and Q12. The second end of T11 is connected to the first end of T21 and the series connection point of C1 and C2. The second end of T21 is connected to the connection point of Q13 and Q14. The connection point of Q12 and Q13 is the output end of the leg circuit.

[0071] In a specific implementation manner, as Figure 7 shown, the connection point between the other end of R11 and one end of R12 of the voltage dividing circuit is the first potential point. The connection point between the other end of R12 and one end of R13 is the potential midpoint. The connection point between the other end of R13 and one end of R14 is the second potential point. The above-mentioned first potential point and second potential point can divide two reference voltages, namely V1 and V2, between the negative bus voltage and the positive bus voltage. And the series connection point of C1 and C2 is also connected to the second end of T11 and the first end of T21. Therefore, one leg circuit corresponds to one voltage dividing circuit. Whether there is a switching device fault in the leg circuit can be detected through the voltage dividing circuit corresponding to the leg circuit, that is, by comparing the magnitudes of V1 and the output voltage of the leg circuit, and the magnitudes of V2 and the output voltage of the leg circuit, the voltage range to which the output voltage of the leg circuit belongs can be determined, that is, the real-time comparison result of V1, V2 and the output voltage of the leg circuit can be obtained. When the real-time comparison result is inconsistent with the preset comparison result, it is determined whether there is a switching device fault in the leg circuit. Among them, the preset comparison result can be seen in Table 2, and for specific reference, see Figure 5 the corresponding embodiment, which will not be elaborated here too much. It should be understood that in Figure 5In the corresponding embodiments, the implementation manners corresponding to the voltage dividing circuit, the comparison circuit, and the amplification circuit in the fault detection circuit are still applicable to Figure 7 the power converter shown herein, which will not be elaborated herein. Refer to Figure 7 , Figure 6 and Figure 4 . Compared with the bridge arm circuit shown in Figure 4 and Figure 6 , the bridge arm circuit shown in Figure 7 has two more switching tubes (i.e., T11 and T21) and corresponding commutation circuits. Therefore, the conduction and cutoff of each switching tube can be controlled to balance the loss distribution, so as to reduce the loss of the switching tubes and thus improve the output power of the power converter.

[0072] It can be understood that the above Figures 4 to 7 shown power converter is a single-bridge-arm single-path, that is, the power converter only includes a fault detection circuit corresponding to the bridge arm circuit. However, in practical applications, the power converter can also be a multi-bridge-arm single-path. At this time, multiple bridge arm circuits are all corresponding to fault detection circuits, and each fault detection circuit can detect whether there is a short-circuit fault of the switching tube in the corresponding bridge arm circuit. Specifically, refer to Figure 8 , Figure 8 is another structural schematic diagram of the power converter provided by this application. As shown in Figure 8 , Figure 8The power converter shown may include a control unit, C1 and C2 connected between BUS+ and BUS-, an A-phase bridge arm circuit, a B-phase bridge arm circuit, and a C-phase bridge arm circuit, and fault detection circuits corresponding to the A-phase bridge arm circuit, the B-phase bridge arm circuit, and the C-phase bridge arm circuit respectively. Among them, the above-mentioned A-phase bridge arm circuit, B-phase bridge arm circuit, and C-phase bridge arm circuit respectively correspond to the A-phase, B-phase, and C-phase outputs of the power converter. The fault detection circuit corresponding to the A-phase bridge arm circuit includes a voltage dividing circuit 1, the fault detection circuit corresponding to the B-phase bridge arm circuit includes a voltage dividing circuit 2, and the fault detection circuit corresponding to the C-phase bridge arm circuit includes a voltage dividing circuit 3. The potential midpoint N1 of the voltage dividing circuit 1 is connected to the series connection point of C1 and C2 and the A-phase bridge arm circuit, the potential midpoint N2 of the voltage dividing circuit 2 is connected to the series connection point of C1 and C2 and the B-phase bridge arm circuit, and the potential midpoint N3 of the voltage dividing circuit 3 is connected to the series connection point of C1 and C2 and the C-phase bridge arm circuit. Here, the voltage dividing circuit 1 corresponding to the A-phase bridge arm circuit can detect whether there is a short circuit fault of the switching tube in the A-phase bridge arm circuit, the voltage dividing circuit 2 corresponding to the B-phase bridge arm circuit can detect whether there is a short circuit fault of the switching tube in the B-phase bridge arm circuit, and the voltage dividing circuit 3 corresponding to the C-phase bridge arm circuit can detect whether there is a short circuit fault of the switching tube in the C-phase bridge arm circuit. Specifically, the control unit can control the A-phase bridge arm circuit, the B-phase bridge arm circuit, and the C-phase bridge arm circuit to work in a preset working state. At this time, the control unit can detect the output voltages of each phase bridge arm circuit (i.e., the output voltage of the A-phase bridge arm circuit, the output voltage of the B-phase bridge arm circuit, and the output voltage of the C-phase bridge arm circuit) and the voltages of the first potential point and the second potential point of each voltage dividing circuit, and then detect whether there is a short circuit fault of the switching tube in each phase bridge arm circuit through the real-time comparison results of the voltages of the first potential point and the second potential point of each voltage dividing circuit and the output voltages of each phase bridge arm circuit.

[0073] As Figure 8 shown, the power converter can be based on Figure 4 the power converter shown and add two-phase bridge arm circuits. In other words, Figure 8 for the circuit structures of the A-phase bridge arm circuit, B-phase bridge arm circuit, and C-phase bridge arm circuit in the power converter shown, reference can be made to Figure 4The circuit structure of the leg circuit in the power converter shown is not elaborated here. In a specific implementation, the control unit can control the leg circuits of phase A, phase B, and phase C to operate in a preset operating state, and detect the output voltage of the leg circuit of phase A (i.e., the voltage at the output terminal O1 of the leg circuit of phase A), detect the output voltage of the leg circuit of phase B (i.e., the voltage at the output terminal O2 of the leg circuit of phase B), detect the output voltage of the leg circuit of phase C (i.e., the voltage at the output terminal O3 of the leg circuit of phase C), as well as the voltages at the first potential point and the second potential point of each voltage division circuit. Further, by comparing the voltage at the first potential point with the output voltage of the leg circuit and the voltage at the second potential point with the output voltage of the leg circuit, a real-time comparison result of the voltage at the first potential point, the voltage at the second potential point, and the output voltage of the leg circuit is obtained. When the real-time comparison result is inconsistent with the preset comparison result, the leg circuit can be controlled to stop working. For details, refer to Figure 5 the corresponding embodiment, which is not elaborated here. It should be understood that in Figure 5 the corresponding embodiment, the implementation manners corresponding to the voltage division circuit, the comparison circuit, and the amplification circuit in the fault detection circuit are still applicable to Figure 8 the power converter shown, which is not elaborated here.

[0074] In this embodiment, when the leg circuit operates in different preset operating states, the fault detection circuit can divide two reference voltages between the negative bus voltage and the positive bus voltage, namely the voltage at the first potential point and the voltage at the second potential point. The control unit can detect whether there is a short circuit fault in the leg circuit by comparing the real-time comparison result of the voltage at the first potential point, the voltage at the second potential point, and the output voltage of the leg circuit with the preset comparison result. Furthermore, when a fault is detected, the wave output of each switching tube in the leg circuit is blocked, that is, the wave output of each switching tube in the leg circuit is stopped, and each switching tube is controlled to turn off to protect the leg circuit, and further protect the power converter. The power converter provided by this application not only has a simple hardware circuit structure, small detection delay, but also has a simple and efficient detection logic, and the detection result is accurate and reliable.

[0075] It should be understood that there can be various circuit structures of the leg circuit in the power converter. The following is an exemplary illustration of it, but it is not a specific limitation to it. In some feasible implementation manners, refer to Figure 9 , Figure 9 which is another structural schematic diagram of the power converter provided by this application. As Figure 9 shown, Figure 9The leg circuits therein may include a control unit, C1 and C2 connected between BUS+ and BUS-, an A-phase leg circuit, a B-phase leg circuit, and a C-phase leg circuit, as well as fault detection circuits respectively corresponding to the A-phase leg circuit, the B-phase leg circuit, and the C-phase leg circuit. And the above-mentioned A-phase leg circuit, B-phase leg circuit, and C-phase leg circuit respectively correspond to the A-phase, B-phase, and C-phase outputs of the power converter. Among them, the fault detection circuit corresponding to the A-phase leg circuit includes a voltage dividing circuit 1, the fault detection circuit corresponding to the B-phase leg circuit includes a voltage dividing circuit 2, and the fault detection circuit corresponding to the C-phase leg circuit includes a voltage dividing circuit 3. The potential midpoint N1 of the voltage dividing circuit 1 is connected to the series connection point of C1 and C2 and the A-phase leg circuit, the potential midpoint N2 of the voltage dividing circuit 2 is connected to the series connection point of C1 and C2 and the B-phase leg circuit, and the potential midpoint N3 of the voltage dividing circuit 3 is connected to the series connection point of C1 and C2 and the C-phase leg circuit. Here, the voltage dividing circuit 1 corresponding to the A-phase leg circuit can detect whether there is a short circuit fault of the switching tube in the A-phase leg circuit, the voltage dividing circuit 2 corresponding to the B-phase leg circuit can detect whether there is a short circuit fault of the switching tube in the B-phase leg circuit, and the voltage dividing circuit 3 corresponding to the C-phase leg circuit can detect whether there is a short circuit fault of the switching tube in the C-phase leg circuit. Specifically, the control unit can control the A-phase leg circuit, the B-phase leg circuit, and the C-phase leg circuit to work in a preset working state. At this time, the control unit can detect the output voltages of each phase leg circuit (i.e., the output voltage of the A-phase leg circuit, the output voltage of the B-phase leg circuit, and the output voltage of the C-phase leg circuit) and the voltages of the first potential point and the second potential point of each voltage dividing circuit, and then detect whether there is a short circuit fault of the switching tube in each phase leg circuit through the real-time comparison results of the voltages of the first potential point and the second potential point of each voltage dividing circuit and the output voltages of each phase leg circuit.

[0076] Such as Figure 9 The power converter shown in Figure 6 can be obtained by adding two-phase leg circuits on the basis of the power converter shown in Figure 9 That is to say, the circuit structures of the A-phase leg circuit, the B-phase leg circuit, and the C-phase leg circuit in the power converter shown in Figure 6The circuit structure of the leg circuit in the power converter shown is not elaborated here. In specific implementation, the control unit can control the leg circuits of phase A, phase B, and phase C to operate in a preset operating state, and detect the output voltage of the leg circuit of phase A (i.e., the voltage at the output terminal O1 of the leg circuit of phase A), detect the output voltage of the leg circuit of phase B (i.e., the voltage at the output terminal O2 of the leg circuit of phase B), detect the output voltage of the leg circuit of phase C (i.e., the voltage at the output terminal O3 of the leg circuit of phase C), and the voltages at the first potential point and the second potential point of each voltage division circuit. Further, by comparing the voltage at the first potential point with the output voltage of the leg circuit and the voltage at the second potential point with the output voltage of the leg circuit, a real-time comparison result of the voltage at the first potential point, the voltage at the second potential point, and the output voltage of the leg circuit is obtained. When the real-time comparison result is inconsistent with the preset comparison result, the leg circuit can be controlled to stop working. For details, see Figure 5 the corresponding embodiment, which is not elaborated here. It should be understood that in Figure 5 the corresponding embodiment, the implementation manners corresponding to the voltage division circuit, the comparison circuit, and the amplification circuit in the fault detection circuit are still applicable to Figure 9 the power converter shown, which is not elaborated here. See Figure 9 and Figure 8 , Figure 8 the leg circuit shown has a long commutation path and a short commutation path. The number of conducting switching tubes in the long commutation path is more than that in the short commutation path. Therefore, when switching from the long commutation path to the short commutation path, the switching tubes turn off. At this time, the rapidly changing current will cause a relatively large stray inductance, and the induced voltage generated by the stray inductance will be superimposed on the bus voltage, causing a voltage spike when the switching tubes turn off, thereby causing excessive stress on the switching tubes, increasing the loss of the switching tubes, and Figure 9 the leg circuit shown can change the long commutation loop into a short commutation loop, so the circuit loss can be reduced and the working efficiency can be improved.

[0077] Optionally, see Figure 10 , Figure 10 is another structural schematic diagram of the power converter provided by the present application. As Figure 10 shown, Figure 10The arm circuit therein may include a control unit, C1 and C2 connected between BUS+ and BUS-, an A-phase arm circuit, a B-phase arm circuit, and a C-phase arm circuit, as well as fault detection circuits corresponding to the A-phase arm circuit, the B-phase arm circuit, and the C-phase arm circuit respectively. And the above A-phase arm circuit, B-phase arm circuit, and C-phase arm circuit respectively correspond to the A-phase, B-phase, and C-phase outputs of the power converter. Among them, the fault detection circuit corresponding to the A-phase arm circuit includes a voltage dividing circuit 1, the fault detection circuit corresponding to the B-phase arm circuit includes a voltage dividing circuit 2, and the fault detection circuit corresponding to the C-phase arm circuit includes a voltage dividing circuit 3. The potential midpoint N1 of the voltage dividing circuit 1 is connected to the series connection point of C1 and C2 and the A-phase arm circuit, the potential midpoint N2 of the voltage dividing circuit 2 is connected to the series connection point of C1 and C2 and the B-phase arm circuit, and the potential midpoint N3 of the voltage dividing circuit 3 is connected to the series connection point of C1 and C2 and the C-phase arm circuit. It can be seen that the voltage dividing circuit 1 corresponding to the A-phase arm circuit can detect whether there is a short circuit fault of the switching tube in the A-phase arm circuit, the voltage dividing circuit 2 corresponding to the B-phase arm circuit can detect whether there is a short circuit fault of the switching tube in the B-phase arm circuit, and the voltage dividing circuit 3 corresponding to the C-phase arm circuit can detect whether there is a short circuit fault of the switching tube in the C-phase arm circuit. Specifically, the control unit can control the A-phase arm circuit, the B-phase arm circuit, and the C-phase arm circuit to work in a preset working state. At this time, the control unit can detect the output voltages of each phase arm circuit (that is, the output voltage of the A-phase arm circuit, the output voltage of the B-phase arm circuit, and the output voltage of the C-phase arm circuit) and the voltages of the first potential point and the second potential point of each voltage dividing circuit, and then detect whether there is a short circuit fault of the switching tube in each phase arm circuit through the real-time comparison results of the voltages of the first potential point and the second potential point of each voltage dividing circuit and the output voltages of each phase arm circuit.

[0078] Such as Figure 10 The power converter shown may be adding two-phase arm circuits on the basis of the power converter shown in Figure 7 That is to say, Figure 10 For the circuit structures of the A-phase arm circuit, the B-phase arm circuit, and the C-phase arm circuit in the power converter shown in Figure 7The circuit structure of the leg circuit in the power converter shown is not elaborated here. In specific implementation, the control unit can control the leg circuits of phase A, phase B, and phase C to work in a preset working state, and detect the output voltage of the leg circuit of phase A (i.e., the voltage at the output terminal O1 of the leg circuit of phase A), detect the output voltage of the leg circuit of phase B (i.e., the voltage at the output terminal O2 of the leg circuit of phase B), detect the output voltage of the leg circuit of phase C (i.e., the voltage at the output terminal O3 of the leg circuit of phase C), and the voltages at the first potential point and the second potential point of each voltage division circuit. Further, by comparing the voltage at the first potential point with the output voltage of the leg circuit and the voltage at the second potential point with the output voltage of the leg circuit, a real-time comparison result of the voltage at the first potential point, the voltage at the second potential point, and the output voltage of the leg circuit is obtained. When the real-time comparison result is inconsistent with the preset comparison result, the leg circuit can be controlled to stop working. For details, please refer to Figure 5 the corresponding embodiment, which is not elaborated here. It should be understood that in Figure 5 the corresponding embodiment, the implementation manners corresponding to the voltage division circuit, the comparison circuit, and the amplification circuit in the fault detection circuit are still applicable to Figure 10 the power converter shown, which is not elaborated here. Please refer to Figure 10 、 Figure 9 and Figure 8 . Compared with the leg circuit shown in Figure 9 and Figure 8 , the leg circuit shown in Figure 10 has two more switching tubes (i.e., T11 and T21) and corresponding commutation circuits. Therefore, the conduction and cutoff of each switching tube can be controlled to balance the loss distribution, so as to reduce the loss of the switching tubes and thus improve the output power of the power converter.

[0079] It should be understood that the power converter shown above Figures 4 to 7 is a single-leg single-path, and the power converter shown above Figures 8 to 10 is a multi-leg single-path. Figure 8 The multi-leg circuit in the power converter shown Figure 9 adopts an I-type three-level topology structure, Figure 10 the multi-leg circuit in the power converter shown

[0080] It can be understood that when the arm circuit operates in different preset operating states, the fault detection circuit can divide two reference voltages between the negative bus voltage and the positive bus voltage, that is, the voltage of the first potential point and the voltage of the second potential point. The control unit can detect whether there is a short-circuit fault in the arm circuit by comparing the real-time comparison results of the voltage of the first potential point, the voltage of the second potential point and the output voltage of the arm circuit with the preset comparison results. Furthermore, when a fault is detected, the control unit can block the waves of each switch tube in the arm circuit, that is, stop sending waves to each switch tube in the arm circuit and control each switch tube to turn off to protect the arm circuit and further protect the power converter. The power converter provided in this application not only has a simple hardware circuit structure, small detection delay, but also has a simple and efficient detection logic and accurate and reliable detection results. In addition, the arm circuit in the power converter provided in the embodiments of this application is also applicable to a variety of circuit structures, can meet the fault detection under a variety of application scenarios, and has strong applicability.

Claims

1. A power converter, characterized in that: The power converter includes a control unit, a first capacitor, a second capacitor, a positive DC bus, a negative DC bus, at least one bridge arm circuit connected between the positive DC bus and the negative DC bus, and a fault detection circuit corresponding to the bridge arm circuit, wherein the fault detection circuit includes a voltage divider circuit, wherein the first capacitor and the second capacitor are connected in series and connected between the positive DC bus and the negative DC bus, the voltage divider circuit is connected between the positive DC bus and the negative DC bus, the potential midpoint of the voltage divider circuit is connected to the series connection point of the first capacitor and the second capacitor, and the voltage divider circuit includes a first potential point and a second potential point, wherein the first potential point is located between the potential midpoint of the voltage divider circuit and the positive DC bus, and the second potential point is located between the potential midpoint of the voltage divider circuit and the negative DC bus; The control unit is used to control the bridge arm circuit to stop working when a real-time comparison result of the voltage of the first potential point, the voltage of the second potential point and the output voltage of the bridge arm circuit is inconsistent with a preset comparison result, wherein the preset comparison result is a comparison result of the voltage of the first potential point, the voltage of the second potential point and the output voltage of the bridge arm circuit when the bridge arm circuit is in a preset working state.

2. The power converter according to claim 1, characterized in that: The voltage divider circuit includes a first resistor, a second resistor, a third resistor and a fourth resistor connected in series; one end of the first resistor is connected to the positive DC bus, the connection point between the other end of the first resistor and one end of the second resistor is the first potential point, the connection point between the other end of the second resistor and one end of the third resistor is the potential midpoint, the connection point between the other end of the third resistor and one end of the fourth resistor is the second potential point, and the other end of the fourth resistor is connected to the negative DC bus.

3. The power converter according to claim 1, characterized in that: The bridge arm circuit includes a first diode, a second diode, a first switch tube, a second switch tube, a third switch tube and a fourth switch tube. The first switch tube, the second switch tube, the third switch tube and the fourth switch tube are connected in series and connected between the positive DC bus and the negative DC bus. The anode of the first diode is connected to the cathode of the second diode and the series connection point of the first capacitor and the second capacitor. The cathode of the first diode is connected to the connection end of the first switch tube and the second switch tube. The anode of the second diode is connected to the connection end of the third switch tube and the fourth switch tube. The connection end of the second switch tube and the third switch tube is the output end of the bridge arm circuit.

4. The power converter according to claim 1, characterized in that: The bridge arm circuit includes a first switch tube, a second switch tube, a third switch tube and a fourth switch tube. The first switch tube and the fourth switch tube are connected in series and connected between the positive DC bus and the negative DC bus. The connection end of the first switch tube and the fourth switch tube is connected to the series connection point of the first capacitor and the second capacitor through the second switch tube and the third switch tube connected in reverse series. The connection end of the first switch tube and the fourth switch tube is the output end of the bridge arm circuit.

5. The power converter according to claim 1, characterized in that: The bridge arm circuit includes a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube and a sixth switch tube. The first switch tube, the second switch tube, the third switch tube and the fourth switch tube are connected in series and connected between the positive DC bus and the negative DC bus. The first end of the fifth switch tube is connected to the connection end of the first switch tube and the second switch tube, the second end of the fifth switch tube is connected to the first end of the sixth switch tube and the series connection point of the first capacitor and the second capacitor, the second end of the sixth switch tube is connected to the connection end of the third switch tube and the fourth switch tube, and the connection end of the second switch tube and the third switch tube is the output end of the bridge arm circuit.

6. The power converter according to any one of claims 3 to 5, characterized in that: The preset working state includes a preset switch tube conduction state, and the preset switch tube conduction state includes a first conduction state, a second conduction state, a third conduction state, a fourth conduction state and a fifth conduction state; The first conduction state is that the first switch tube and the second switch tube are turned on, and the third switch tube and the fourth switch tube are turned off; The second conduction state is that the second switch tube and the third switch tube are turned on, and the first switch tube and the fourth switch tube are turned off; The third conduction state is that the third switch tube and the fourth switch tube are turned on, and the first switch tube and the second switch tube are turned off; The fourth conduction state is that the second switch tube is turned on, and the first switch tube, the third switch tube and the fourth switch tube are turned off; The fifth conducting state is that the third switch tube is turned on, and the first switch tube, the second switch tube and the fourth switch tube are turned off.

7. The power converter according to claim 6, characterized in that: The preset comparison results include a first preset comparison result, a second preset comparison result and a third preset comparison result; The first preset comparison result is that when the bridge arm circuit is in the first conduction state, the voltage at the first potential point is less than the output voltage of the bridge arm circuit and the voltage at the second potential point is less than the output voltage of the bridge arm circuit; The second preset comparison result is that when the bridge arm circuit is in the second conduction state, the voltage at the first potential point is greater than the output voltage of the bridge arm circuit and the voltage at the second potential point is less than the output voltage of the bridge arm circuit; The third preset comparison result is that when the bridge arm circuit is in the third conduction state, the voltage of the first potential point is greater than the output voltage of the bridge arm circuit and the voltage of the second potential point is greater than the output voltage of the bridge arm circuit.

8. The power converter according to any one of claims 6 or 7, characterized in that: The preset working state also includes a bridge arm current state, and the bridge arm current state includes a bridge arm current direction of the bridge arm circuit flowing out of the output end of the bridge arm circuit and a bridge arm current direction flowing into the output end of the bridge arm circuit; the preset comparison result includes; The fourth preset comparison result is that, when the bridge arm current state is that the current direction of the bridge arm current is flowing out of the output end of the bridge arm circuit and the preset switch tube conduction state is the fourth conduction state, the voltage of the first potential point is greater than the output voltage of the bridge arm circuit and the voltage of the second potential point is less than the output voltage of the bridge arm circuit; The fifth preset comparison result is that, when the bridge arm current state is that the current direction of the bridge arm current is flowing into the output end of the bridge arm circuit and the preset switch tube conduction state is the fourth conduction state, the voltage of the first potential point is less than the output voltage of the bridge arm circuit and the voltage of the second potential point is less than the output voltage of the bridge arm circuit; The sixth preset comparison result is that, when the bridge arm current state is that the current direction of the bridge arm current is flowing out of the output end of the bridge arm circuit and the preset switch tube conduction state is the fifth conduction state, the voltage of the first potential point is greater than the output voltage of the bridge arm circuit and the voltage of the second potential point is greater than the output voltage of the bridge arm current; The seventh preset comparison result is that, when the bridge arm current state is that the current direction of the bridge arm current is flowing into the output end of the bridge arm circuit and the preset switch tube conduction state is the fifth conduction state, the voltage of the first potential point is greater than the output voltage of the bridge arm circuit and the voltage of the second potential point is less than the output voltage of the bridge arm circuit.

9. The power converter according to any one of claims 1 to 8, characterized in that: The real-time comparison result includes a first comparison result and a second comparison result, and the fault detection circuit further includes a comparison circuit, and the comparison circuit includes a first comparator and a second comparator; the negative input end of the first comparator is connected to the first potential point, the negative input end of the second comparator is connected to the second potential point, and the positive input end of the first comparator and the positive input end of the second comparator are connected to the output end of the bridge arm circuit; The first comparator is used to compare the voltage of the first potential point with the output voltage of the bridge arm circuit and output the first comparison result to the control unit; The second comparator is used to compare the voltage of the second potential point with the output voltage of the bridge arm circuit and output the second comparison result to the control unit.

10. The power converter according to claim 9, characterized in that: The fault detection circuit further includes an amplifier circuit, which includes a first amplifier circuit and a second amplifier circuit; an input end of the first amplifier circuit is connected to an output end of the first comparator, and an input end of the second amplifier circuit is connected to an output end of the second comparator; The first amplifier circuit is used to amplify the comparison result output by the first comparator and then output the first comparison result to the control unit; The second amplifier circuit is used to amplify the comparison result output by the second comparator and then output the second comparison result to the control unit.

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