Power converter

Abstract

The embodiment of the invention provides a power converter. The power converter comprises a controller, at least one bridge arm, a first capacitor and a second capacitor, wherein the first capacitor and the second capacitor are connected in series. Each bridge arm comprises 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 then connected in parallel to the two ends of the first capacitor and the second capacitor which are connected in series, and the connecting end is connected with the connecting end of the first capacitor and the second capacitor through the second switch tube and the third switch tube which are reversely connected in series. After the power converter is started, the controller controls the target switch tubes in the bridge arms to be kept on, the target capacitor starts to be charged after the target switch tubes in the bridge arms are on, the target capacitor is at least one of the first capacitor and the second capacitor, and the target switch tubes are at least one of the switch tubes in the bridge arms. And when the voltage at the two ends does not reach the voltage threshold after the target capacitor is charged, the controller outputs the information that the switching tube short-circuit fault exists in each bridge arm.

Description

Technical Field

[0001] The present application relates to the field of power electronics, and in particular to a power converter. Background Art

[0002] As the penetration rate of distributed energy sources such as photovoltaics, wind power and energy storage devices gradually increases, power converters or inverters, as important components of energy exchange, are increasingly widely used in power supply systems. During the operation of power converters or inverters, switch tube failures may occur, such as topology direct-through due to switch tube short circuit, busbar short circuit, switch tube overcurrent damage, etc. In order to start the power converter or inverter when there is an abnormality without further damage, it is necessary to perform some power-on self-tests before starting the power converter or inverter to ensure the safe operation of the equipment. Summary of the invention

[0003] An embodiment of the present application provides a power converter that can perform short-circuit fault detection on a switch tube before the power converter operates, thereby avoiding abnormal operating conditions such as bus short circuit and short-circuit fault spread during the operation of the power converter, and improving the reliability of the power converter operation.

[0004] In the first aspect, the present application provides a power converter, which includes a controller, at least one bridge arm, and a first capacitor and a second capacitor connected in series, wherein the first capacitor is connected to a positive DC bus, and the second capacitor is connected to a negative DC bus. Each bridge arm in at least one bridge arm includes a first switch tube, a second switch tube, a third switch tube, and a fourth switch tube, wherein the first switch tube and the fourth switch tube are connected in series and then connected in parallel at both ends of the first capacitor and the second capacitor connected in series, and the connection end of the first switch tube and the fourth switch tube is connected to the connection end of the first capacitor and the second capacitor through the second switch tube and the third switch tube connected in reverse series. The controller is used to control the target switch tubes in each bridge arm to remain turned on after the power converter is turned on, wherein the other switch tubes except the target switch tube in each bridge arm remain turned off, and the target capacitor starts to charge after the target switch tube in each bridge arm is turned on, and the target capacitor is at least one of the first capacitor and the second capacitor, and the target switch tube is at least one of the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube in each bridge arm. The controller is also used to output information that there is a short circuit fault of the switch tube in each bridge arm when the voltage at both ends of the target capacitor does not reach the voltage threshold after charging.

[0005] In the present application, the controller in the power converter controls the target switch tubes in each bridge arm to remain turned on after the power converter is turned on and before the formal operation. The above-mentioned target capacitor starts to charge after the target switch tubes in each bridge arm are turned on. Wherein, the voltage across the above-mentioned target capacitor is zero, which may be that before the power converter is connected to the DC power supply, the above-mentioned target capacitor is not charged and the voltage across the two ends is zero, or the target capacitor may be discharged until the voltage across the two ends is zero. Then, when the voltage across the two ends of the target capacitor does not reach the voltage threshold after the controller is charged, it is determined that there is a short circuit in the switch tube in the current power converter, and the information of the short circuit fault of the switch tube in each bridge arm is output. By detecting the faulty switch tube before the power converter works, abnormal working conditions such as bus short circuit and short circuit fault diffusion are avoided during the operation of the power converter, and the reliability of the power converter operation is improved.

[0006] In a possible implementation, the power converter includes a slow-start switch and a resistor connected in series on a positive DC bus or a negative DC bus, the target capacitor is a first capacitor and a second capacitor, the target switch tube is a first switch tube in each bridge arm, and the target capacitor starts to charge after the target switch tube in each bridge arm is turned on. Specifically, after the first switch tube in each bridge arm remains turned on, the controller controls the slow-start switch to turn on to turn on the connection between the first capacitor and the second capacitor and the DC power supply to start charging the first capacitor and the second capacitor through the DC power supply. The controller is also used to output information that the third switch tube is short-circuited after the DC power supply charges the first capacitor and the second capacitor and the voltage across the first capacitor does not reach the voltage threshold, or output information that the fourth switch tube is short-circuited after the DC power supply charges the first capacitor and the second capacitor and the voltage across the first capacitor and the voltage across the second capacitor do not reach the voltage threshold. Here, if the third switch tube is short-circuited and the second switch tube is disconnected, the diode connected in parallel with the second switch tube can conduct the current flowing from the connection end of the first switch tube and the fourth switch tube to the connection end of the first capacitor and the second capacitor. Therefore, the third switch tube and the second switch tube cannot cut off the current flowing from the connection end of the first switch tube and the fourth switch tube to the connection end of the first capacitor and the second capacitor. The first capacitor is short-circuited and cannot be boosted normally. If the fourth switch tube is short-circuited, the fourth switch tube cannot cut off the current flowing from the positive DC bus to the negative DC bus. The first capacitor and the second capacitor are short-circuited and cannot be boosted normally. Therefore, the short-circuit fault detection of the switch tube can be accurately performed through the voltage change at both ends of the first capacitor and the second capacitor after charging.

[0007] In a possible implementation, the power converter includes a slow-start switch and a resistor connected in series on a positive DC bus or a negative DC bus, the target capacitor is a first capacitor and a second capacitor, the target switch tube is a fourth switch tube in each bridge arm, and the target capacitor starts to charge after the target switch tube in each bridge arm is turned on. Specifically, after the fourth switch tube in each bridge arm remains turned on, the controller controls the slow-start switch to turn on to connect the first capacitor and the second capacitor to the DC power supply to start charging the first capacitor and the second capacitor through the DC power supply. The controller is also used to control the slow-start switch to turn on after controlling the fourth switch tube in each bridge arm to remain turned on, so as to connect the first capacitor and the second capacitor to the DC power supply to charge the first capacitor and the second capacitor through the DC power supply. The controller is also used to output information that the second switch tube is short-circuited after the DC power supply charges the first capacitor and the second capacitor and the voltage across the second capacitor does not reach the voltage threshold, or output information that the first switch tube is short-circuited after the DC power supply charges the first capacitor and the second capacitor and the voltage across the first capacitor and the voltage across the second capacitor do not reach the voltage threshold. Here, if the second switch tube is short-circuited and the third switch tube is disconnected, the diode connected in parallel with the third switch tube can conduct the current flowing from the connection end of the first capacitor and the second capacitor to the connection end of the first switch tube and the fourth switch tube, so the second switch tube and the third switch tube cannot cut off the current flowing from the connection end of the first capacitor and the second capacitor to the connection end of the first switch tube and the fourth switch tube, and the second capacitor is short-circuited and cannot be boosted normally. If the first switch tube is short-circuited, the first switch tube cannot cut off the current flowing from the positive DC bus to the negative DC bus, and the first capacitor and the second capacitor are short-circuited and cannot be boosted normally. Therefore, the short-circuit fault detection of the switch tube can be accurately performed through the voltage change at both ends of the first capacitor and the second capacitor after charging.

[0008] In one possible implementation, a discharge circuit is connected in parallel across the first capacitor and the second capacitor, and the controller is used to, after controlling the slow-start switch to be turned on to connect the first capacitor and the second capacitor to the DC power supply so as to charge the first capacitor and the second capacitor through the DC power supply, if the voltage across the first capacitor and the voltage across the second capacitor are both greater than or equal to the voltage threshold, control the first switch tube to be turned off, and control the slow-start switch to be turned off to disconnect the first capacitor and the second capacitor from the DC power supply so that the discharge circuit discharges the first capacitor and the second capacitor, and when the first capacitor and the second capacitor are discharged to the voltage at both ends being zero, control the second switch tube in each bridge arm to remain turned on, and control the slow-start switch to be turned on to connect the first capacitor and the second capacitor to the DC power supply so as to charge the first capacitor and the second capacitor through the DC power supply, and output information that the fourth switch tube is short-circuited after the second capacitor is charged and the voltage across the two ends does not reach the voltage threshold. Here, when the voltages at both ends of the first capacitor and the second capacitor after being charged are greater than or equal to the voltage threshold, a secondary short circuit fault detection is performed on the fourth switch tube. This can avoid the inability to normally detect whether the fourth switch tube is short-circuited due to the first switch tube being open-circuited, thereby improving the accuracy of switch tube short circuit fault detection.

[0009] In one possible implementation, a discharge circuit is connected in parallel across the first capacitor and the second capacitor, and the controller is used to, after controlling the slow-start switch to be turned on to connect the first capacitor and the second capacitor to the DC power supply so as to charge the first capacitor and the second capacitor through the DC power supply, if the voltage across the first capacitor and the voltage across the second capacitor are both greater than or equal to the voltage threshold, control the fourth switch tube to be turned off, and control the slow-start switch to be turned off to disconnect the first capacitor and the second capacitor from the DC power supply so that the discharge circuit discharges the first capacitor and the second capacitor, and when the first capacitor and the second capacitor are discharged to a voltage of zero at both ends, control the third switch tube in each bridge arm to remain turned on, and control the slow-start switch to be turned on to connect the first capacitor and the second capacitor to the DC power supply so as to charge the first capacitor and the second capacitor through the DC power supply, and output information that the first switch tube is short-circuited after the first capacitor is charged and the voltage across both ends does not reach the voltage threshold. Here, when the voltages at both ends of the first capacitor and the second capacitor after being charged are greater than or equal to the voltage threshold, a secondary short circuit fault detection is performed on the first switch tube, which can avoid the inability to normally detect whether the first switch tube is short-circuited due to the fourth switch tube being disconnected, thereby improving the accuracy of the switch tube short circuit fault detection.

[0010] In a possible implementation, a discharge circuit is connected in parallel across the first capacitor and the second capacitor. In each bridge arm, the connection end of the first switch tube and the fourth switch tube is also connected to the connection end of the first capacitor and the second capacitor through a filter capacitor. After controlling the slow-start switch to be turned on to connect the first capacitor and the second capacitor to the DC power supply to charge the first capacitor and the second capacitor through the DC power supply, the controller is also used to control the target switch tube to be turned off if the voltage across the first capacitor and the voltage across the second capacitor are both greater than or equal to the voltage threshold, and control the slow-start switch to be turned off to disconnect the first capacitor and the second capacitor from the DC power supply so that the discharge circuit discharges the first capacitor and the second capacitor, and when the first capacitor and the second capacitor are discharged to the voltage at both ends being zero, control the slow-start switch to be turned on to connect the first capacitor and the second capacitor to the DC power supply to charge the first capacitor and the second capacitor through the DC power supply. If after the first capacitor and the second capacitor are charged, the voltage across the first capacitor and the voltage across the second capacitor do not reach the voltage threshold, output information that the first switch tube and the fourth switch tube are short-circuited. Alternatively, the controller is also used to control the target switch tube to be disconnected if the voltage across the first capacitor and the voltage across the second capacitor are both greater than or equal to the voltage threshold, and control the slow-start switch to be disconnected to disconnect the connection between the first capacitor and the second capacitor and the DC power supply, so that the discharge circuit discharges the first capacitor and the second capacitor, and when the voltage across the first capacitor and the second capacitor is discharged to zero, control the slow-start switch to be turned on to turn on the connection between the first capacitor and the second capacitor and the DC power supply to charge the first capacitor and the second capacitor through the DC power supply, and if the voltage across the filter capacitor is equal to the voltage across the first capacitor or the second capacitor after the first capacitor and the second capacitor are charged, output the information that the first switch tube or the fourth switch tube is short-circuited. Here, when the voltage across the first capacitor and the second capacitor is greater than or equal to the voltage threshold after the first capacitor and the second capacitor are charged, the first switch tube or the fourth switch tube is subjected to secondary short-circuit fault detection, which can avoid the failure to normally detect whether the first switch tube is short-circuited when the fourth switch tube is disconnected, and the failure to normally detect whether the fourth switch tube is short-circuited when the first switch tube is disconnected, thereby improving the accuracy of the switch tube short-circuit fault detection.

[0011] In a possible implementation, the power converter further includes an electric energy transfer unit, and the controller is used to control the slow-start switch to be turned on to connect the first capacitor and the second capacitor to the DC power supply to charge the first capacitor and the second capacitor through the DC power supply. If the voltage across the first capacitor and the voltage across the second capacitor are both greater than or equal to the voltage threshold, the target switch tube is controlled to be disconnected, and the electric energy transfer unit is controlled to discharge the first capacitor through the electric energy transfer unit. The controller is also used to control the third switch tube in each bridge arm to remain turned on when the voltage across the first capacitor is discharged to zero through the electric energy transfer unit, and control the electric energy transfer unit to charge the first capacitor through the electric energy transfer unit. The controller is also used to output information that the first switch tube is short-circuited if the voltage across the first capacitor does not reach the voltage threshold after charging the first capacitor through the electric energy transfer unit. Here, if the first switch tube is short-circuited, the first switch tube cannot cut off the current flowing from the positive DC bus to the negative DC bus, the first capacitor is short-circuited, and the voltage cannot be boosted normally. Therefore, the voltage change at both ends after the first capacitor is charged can accurately detect the short-circuit fault of the switch tube.

[0012] In a possible implementation, the power converter also includes an electric energy transfer unit, and the controller is used to control the slow-start switch to be turned on to connect the first capacitor and the second capacitor to the DC power supply to charge the first capacitor and the second capacitor through the DC power supply. If the voltage across the first capacitor and the voltage across the second capacitor are both greater than or equal to the voltage threshold, the first switch tube is controlled to be disconnected, and the electric energy transfer unit is controlled to discharge the second capacitor through the electric energy transfer unit. The controller is also used to control the fourth switch tube in each bridge arm to remain turned on when the voltage across the second capacitor is discharged to zero through the electric energy transfer unit, and control the electric energy transfer unit to charge the second capacitor through the electric energy transfer unit. The controller is also used to output information that the second switch tube is short-circuited if the voltage across the second capacitor does not reach the voltage threshold after the second capacitor is charged through the electric energy transfer unit. Here, if the second switch tube is short-circuited and the third switch tube is disconnected, the diode connected in parallel with the third switch tube can conduct the current flowing from the connection end of the first capacitor and the second capacitor to the connection end of the first switch tube and the fourth switch tube. Therefore, the second switch tube and the third switch tube cannot cut off the current flowing from the connection end of the first capacitor and the second capacitor to the connection end of the first switch tube and the fourth switch tube. The second capacitor is short-circuited and cannot be boosted normally. The voltage change at both ends of the second capacitor after charging can accurately detect the short circuit fault of the switch tube.

[0013] In a possible implementation, the power converter also includes an electric energy transfer unit; the controller is used to, after controlling the slow-start switch to turn on to connect the first capacitor and the second capacitor to the DC power supply to charge the first capacitor and the second capacitor through the DC power supply, if the voltage across the first capacitor and the voltage across the second capacitor are both greater than or equal to the voltage threshold, control the fourth switch tube to disconnect, and control the electric energy transfer unit to discharge the first capacitor through the electric energy transfer unit. The controller is also used to control the first switch tube in each bridge arm to remain turned on when the voltage across the first capacitor is discharged to zero through the electric energy transfer unit, and control the electric energy transfer unit to charge the first capacitor through the electric energy transfer unit. The controller is also used to output information that the third switch tube is short-circuited if the voltage across the first capacitor does not reach the voltage threshold after the first capacitor is charged through the electric energy transfer unit. Here, if the third switch tube is short-circuited and the second switch tube is disconnected, the diode connected in parallel with the second switch tube can conduct the current flowing from the connection end of the first switch tube and the fourth switch tube to the connection end of the first capacitor and the second capacitor. Therefore, the third switch tube and the second switch tube cannot cut off the current flowing from the connection end of the first switch tube and the fourth switch tube to the connection end of the first capacitor and the second capacitor. The first capacitor is short-circuited and cannot be boosted normally. The short-circuit fault of the switch tube can be accurately detected by the voltage change at both ends after the first capacitor is charged.

[0014] In a possible implementation, the power converter further includes an electric energy transfer unit, and the controller is used to control the slow-start switch to be turned on to connect the first capacitor and the second capacitor to the DC power supply to charge the first capacitor and the second capacitor through the DC power supply. If the voltage across the first capacitor and the voltage across the second capacitor are both greater than or equal to the voltage threshold, the target switch tube is controlled to be disconnected, and the electric energy transfer unit is controlled to discharge the second capacitor through the electric energy transfer unit. The controller is also used to control the second switch tube in each bridge arm to remain turned on when the voltage across the second capacitor is discharged to zero through the electric energy transfer unit, and control the electric energy transfer unit to charge the second capacitor through the electric energy transfer unit. The controller is also used to output information that the fourth switch tube is short-circuited if the second capacitor is charged through the electric energy transfer unit and the voltage across the second capacitor does not reach the voltage threshold after the second capacitor is charged. If the fourth switch tube is short-circuited, the fourth switch tube cannot cut off the current flowing from the positive DC bus to the negative DC bus, and the second capacitor is short-circuited and cannot be normally boosted. The voltage change at both ends after the second capacitor is charged can accurately detect the short-circuit fault of the switch tube.

[0015] In a possible implementation, the power transfer unit includes an inductor, a fifth switch tube and a sixth switch tube connected in series, the fifth switch tube is connected to the positive DC bus, the sixth switch tube is connected to the negative DC bus, and the connection end of the fifth switch tube and the sixth switch tube is connected to the connection end of the first capacitor and the second capacitor through the inductor. The power transfer unit is controlled to discharge the first capacitor or the second capacitor through the power transfer unit, specifically controlling the fifth switch tube and the sixth switch tube to act so as to transfer the power of the first capacitor to the second capacitor through the inductor to discharge the first capacitor, or, to transfer the power of the second capacitor to the first capacitor through the inductor to discharge the second capacitor. The power transfer unit is controlled to charge the first capacitor or the second capacitor through the power transfer unit, specifically controlling the fifth switch tube and the sixth switch tube to act so as to transfer the power of the second capacitor to the first capacitor through the inductor to charge the first capacitor, or, to transfer the power of the first capacitor to the second capacitor through the inductor to charge the second capacitor.

[0016] In a possible implementation, during the charging process of the target capacitor, the voltage change rate across the target capacitor is less than a set threshold. Here, since the slow-start circuit includes a resistor, the resistor can limit the impact current when the power converter is powered on, so that during the charging process of the first capacitor and the second capacitor, the voltage change rate across the two ends is less than the set threshold, avoiding instantaneous voltage jumps across the first capacitor and the second capacitor, and preventing a large current from being connected when there is a short-circuited switch in the bridge arm, causing overcurrent damage to some switch tubes. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of an application scenario of the power supply system provided by this application;

[0018] Figure 2 is a schematic diagram of another application scenario of the power supply system provided by the present application;

[0019] Figure 3 is a structural schematic diagram of a power converter provided by the present application;

[0020] Figure 4 is another structural schematic diagram of the power converter provided by the present application;

[0021] Figure 5 is another structural schematic diagram of the power converter provided by the present application;

[0022] Figure 6 is another structural schematic diagram of the power converter provided by the present application;

[0023] Figure 7 is another structural schematic diagram of the power converter provided by the present application;

[0024] Figure 8This is a schematic diagram of a short circuit of a switch tube of a power converter provided by the present application;

[0025] Fig. 9 is another short-circuit schematic diagram of a switch tube of a power converter provided by the present application;

[0026] Fig.10 is another short-circuit schematic diagram of a switch tube of a power converter provided by the present application;

[0027] Fig.11 It is another structural schematic diagram of the power converter provided by the present application. DETAILED DESCRIPTION

[0028] See also Figure 1 , Figure 1 : This is a schematic diagram of an application scenario of the power supply system provided by the present application. The power supply system provided by the present application may include a DC power supply and at least one power converter, wherein the DC power supply is a photovoltaic module. Taking the power supply system including multiple power converters as an example, the DC end of the power converter is used to connect the photovoltaic module, and the AC end of the power converter is connected in parallel to connect the power grid or load. The power converter can invert the DC power provided by the battery, and output the AC power obtained after the inversion conversion to the power grid or load for power supply.

[0029] In some feasible implementations, the DC power source is a storage battery, and the DC end of each power converter can be used to connect to the storage battery. Figure 2 , Figure 2 It is another application scenario schematic diagram of the power supply system provided by the present application. Among the multiple power converters of the power supply system, the DC end of some power converters is used to connect the energy storage battery, and the AC end of multiple power converters is connected in parallel to connect the power grid or load. Each power converter can invert the DC power provided by the photovoltaic module or the energy storage battery, and output the AC power obtained after the inversion conversion to the power grid or load for power supply. Here, the power converter connected to the photovoltaic module in the power supply system can be an inverter, and the power converter connected to the energy storage battery in the power supply system can be a converter.

[0030] exist Figure 1 or Figure 2 In the application scenario of the power supply system shown, the switch tube may fail during the operation of the power converter, such as topology shoot-through due to a short circuit of the switch tube, busbar short circuit, overcurrent damage to the switch tube, etc. In order to start the power converter or converter without further damage when there is an abnormality, it is necessary to set a power-on self-check before the power converter is started, that is, before the power converter is connected to the load or grid and performs inverter conversion, to ensure safe operation of the equipment.

[0031] See also Figure 3 , Figure 3 Schematic diagram of a power converter provided by the present application. Figure 3 As shown, Figure 3 The power converter in may include a first capacitor C1 and a second capacitor C2 connected in series, and a bridge arm. The bridge arm may include a first switch tube Q11 and a fourth switch tube Q14 connected in series, the first switch tube Q11 and the fourth switch tube Q14 connected in series are connected in parallel at both ends of the first capacitor C1 and the second capacitor C2, and the connection end of the first switch tube Q11 and the fourth switch tube Q14 is connected to the connection end of the first capacitor C1 and the second capacitor C2 through the second switch tube Q12 and the third switch tube Q13 connected in reverse series, and the connection end of the first switch tube Q11 and the fourth switch tube Q14 can lead to an output port. Here, the second switch tube Q12 and the third switch tube Q13 are connected in reverse series, and the direction of the diodes connected in parallel on the second switch tube Q12 and the third switch tube Q13 may be opposite. In other words, the current conduction direction of the diodes connected in parallel on the second switch tube Q12 and the third switch tube Q13 is opposite, and the diodes connected in parallel on the second switch tube Q12 and the third switch tube Q13 may be the body diodes contained in the second switch tube Q12 and the third switch tube Q13. For example, the diode connected in parallel with the second switch tube Q12 can conduct the current flowing from the connection end of the first switch tube Q11 and the fourth switch tube Q14 to the connection end of the first capacitor C1 and the second capacitor C2, and the diode connected in parallel with the third switch tube Q13 can conduct the current flowing from the connection end of the first capacitor C1 and the second capacitor C2 to the connection end of the first switch tube Q11 and the fourth switch tube Q14. Here, in the above-mentioned second switch tube Q12 and third switch tube Q13 connected in reverse series, the third switch tube Q13 can be connected to the connection end of the first capacitor C1 and the second capacitor C2, or the second switch tube Q12 can be connected to the connection end of the first capacitor C1 and the second capacitor C2. The embodiment of the present application takes the connection end of the third switch tube Q13 to the connection end of the first capacitor C1 and the second capacitor C2 as an example, which will not be repeated below.

[0032] Understandably, the above Figure 3 The power converter shown is a single-bridge converter. The power converter provided in the application may also be a multi-bridge converter. For details, see Figure 4 , Figure 4 is another schematic diagram of the structure of the power converter provided by the present application. Figure 4 As shown, Figure 4The power converter may include a first capacitor C1 and a second capacitor C2 connected in series, as well as an A-phase bridge arm, a B-phase bridge arm and a C-phase bridge arm, and the above-mentioned A-phase bridge arm, B-phase bridge arm and C-phase bridge arm correspond to the A-phase, B-phase and C-phase outputs of the power converter respectively. The first capacitor C1 is connected to the positive DC bus BUS+, and the second capacitor C2 is connected to the negative DC bus BUS-. The A-phase bridge arm may include a first switch tube Q11, a second switch tube Q12, a third switch tube Q13 and a fourth switch tube Q14. The above-mentioned B-phase bridge arm may include a first switch tube Q21, a second switch tube Q22, a third switch tube Q23 and a fourth switch tube Q24, and the above-mentioned C-phase bridge arm may include a first switch tube Q31, a second switch tube Q32, a third switch tube Q33 and a fourth switch tube Q34. It can be understood that, Figure 4 In the power converter shown in FIG. 1 , the circuit structures of the A-phase bridge arm, the B-phase bridge arm and the C-phase bridge arm are the same as those described above. Figure 3 The bridge arms in the power converter shown are the same and will not be described in detail here. Optionally, the power converter may further include an N-phase bridge arm. Figure 5 , Figure 5 is another schematic diagram of the structure of the power converter provided by the present application. Figure 5 As shown, Figure 5 The power converter in the embodiment may include a first capacitor C1 and a second capacitor C2 connected in series, and an A-phase bridge arm, a B-phase bridge arm, a C-phase bridge arm and an N-phase bridge arm. The structures of the A-phase bridge arm, the B-phase bridge arm and the C-phase bridge arm may refer to the above Figure 4 In the power converter shown, the N-phase bridge arm leads to the N-phase output of the power converter. The N-phase bridge arm may include a first switch tube Q41 and a fourth switch tube Q44 connected in series, the first switch tube Q41 and the fourth switch tube Q44 connected in series are connected in parallel at both ends of the first capacitor C1 and the second capacitor C2, and the connection end of the first switch tube Q41 and the fourth switch tube Q44 is connected to the connection end of the first capacitor C1 and the second capacitor C2 through the second switch tube Q42 and the third switch tube Q43 connected in reverse series, and the connection end of the first switch tube Q41 and the fourth switch tube Q44 can lead to the N-phase output.

[0033] exist Figures 3 to 5 In the power converter shown in FIG. 1 , the switch tubes in each bridge arm may be short-circuited. For example, Figure 3Taking the A-phase bridge arm in the power converter shown as an example, when the first switch tube Q11 is short-circuited, if the second switch tube Q12 is turned on and the DC bus side is powered normally, the positive DC bus BUS+ will be short-circuited, the first capacitor C1 cannot be charged normally, and the second switch tube Q12 will be subjected to excessive short-circuit current, affecting the normal operation of the power converter. Alternatively, when the first switch tube Q11 is short-circuited, if the fourth switch tube Q14 is turned on and the DC bus side is powered normally, the positive DC bus BUS+ and the negative DC bus BUS- will be short-circuited, the first capacitor C1 and the second capacitor C2 will not be charged normally, and the fourth switch tube Q14 will be subjected to excessive short-circuit current, affecting the normal operation of the power converter.

[0034] In addition, the above Figures 3 to 5 In the power converter shown in FIG. 1 , the connection end of the first switch tube and the fourth switch tube of each bridge arm is also connected to the connection end of the first capacitor and the second capacitor through a filter capacitor and a filter inductor. Figure 5 Take the power converter shown in the figure as an example, see Figure 6 , Figure 6 is another schematic diagram of the structure of the power converter provided by the present application. Figure 6 As shown, Figure 6 In the power converter, the connection end of the first switch tube Q11 and the fourth switch tube Q14 in the A-phase bridge arm is connected to the connection end of the first capacitor C1 and the second capacitor C2 through the filter inductor L1 and the filter capacitor C10, the connection end of the first switch tube Q21 and the fourth switch tube Q24 in the B-phase bridge arm is connected to the connection end of the first capacitor C1 and the second capacitor C2 through the filter inductor L2 and the filter capacitor C20, the connection end of the first switch tube Q31 and the fourth switch tube Q34 in the C-phase bridge arm is connected to the connection end of the first capacitor C1 and the second capacitor C2 through the filter inductor L3 and the filter capacitor C30, and the connection end of the first switch tube Q41 and the fourth switch tube Q44 in the N-phase bridge arm is connected to the connection end of the first capacitor C1 and the second capacitor C2 through the filter inductor L4 and the filter capacitor C40.

[0035] As described in the above embodiments and in combination Figure 3-Figure 5 The technical solution provided by the present application is suitable for detecting faulty switch tubes of a power converter after it is turned on and before it is officially put into operation. Specifically, in the power converter provided by the present application, the power converter includes a controller ( Figures 3 to 5(not shown), at least one bridge arm and a first capacitor and a second capacitor connected in series, the first capacitor is connected to the positive DC bus, and the second capacitor is connected to the negative DC bus. Before the power converter is turned on, the DC side of the power converter is not connected to the DC power supply, and the AC side of the power converter is not connected to the load or the power grid, and the entire power converter is powered off. After the power converter is turned on, before it officially works, for example, before the DC input of the energy storage battery as a DC power supply is inverted and converted into an AC output and transmitted to the load or the power grid, it is necessary to detect whether the switch tube in the power converter is normal to prevent the switch tube in the power converter from short-circuiting due to a short circuit, thereby endangering the safety of the equipment.

[0036] In the technical solution provided by the present application, the controller selects at least one of the first capacitor and the second capacitor as the target capacitor, selects at least one of the target switch tubes in each phase bridge arm, controls the target switch tube to be turned on, and then charges or discharges the target capacitor. In this process, it is determined whether the charging or discharging process of the target capacitor is normal, thereby determining whether a specific switch tube in each phase bridge arm is short-circuited or open-circuited. Specifically, Figure 5 Taking the power converter shown as an example, the controller of the power converter will first control the target switch tube to turn on after starting up. The target switch tube is at least one of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube in each bridge arm. For example, if the target switch tube is the first switch tube, then the first switch tube Q11 in the A phase bridge arm, the first switch tube Q21 in the B phase bridge arm, the first switch tube Q31 in the C phase bridge arm and the first switch tube Q41 in the N phase bridge arm are the target switch tubes. At the initial moment after the power converter is turned on, the voltage across the first capacitor C1 and the second capacitor C2 is zero, and after controlling the target switch tube to turn on, the target capacitor is charged. The target capacitor is at least one of the first capacitor C1 and the second capacitor C2, and the other switch tubes in each bridge arm except the target switch tube remain turned off. Then, when the voltage across the target capacitor does not reach the voltage threshold after charging, the controller determines that a switch tube in the current power converter is short-circuited, and outputs information about the existence of a switch tube short-circuit fault in each bridge arm. By detecting the faulty switch tube before the power converter works, abnormal conditions such as bus short circuit and short circuit fault spread can be avoided during the operation of the power converter, thereby improving the reliability of the power converter operation.

[0037] In some feasible embodiments, the power converter includes a slow-start circuit, which may include a slow-start switch and a resistor connected in series on a positive DC bus or a negative DC bus. The controller is used to control the first switch tube in each bridge arm to remain turned on when the voltage across the first capacitor and the second capacitor is zero, and then control the slow-start switch to be turned on, so as to connect the first capacitor and the second capacitor to the DC power supply to charge the first capacitor and the second capacitor through the DC power supply. The controller is also used to output information that the third switch tube is short-circuited when the voltage across the first capacitor has been charged and the voltage across the two terminals has not reached a voltage threshold, or output information that the fourth switch tube is short-circuited when the voltage across the first capacitor and the second capacitor has been charged and the voltage across the two terminals has not reached a voltage threshold. See. Figure 7 , Figure 7 is another schematic diagram of the structure of the power converter provided by the present application. Figure 7 As shown, Figure 7 The power converter in the embodiment includes four bridge arms, and the structure of each bridge arm can refer to the above Figure 5 , the power converter may also include a slow-start circuit, which includes a slow-start switch K1 and a resistor R, and the slow-start switch K1 and the resistor R may be connected in series on the positive DC bus BUS+ or the negative DC bus BUS-. Taking the slow-start switch K1 and the resistor R connected in series on the positive DC bus BUS+ as an example, during the fault switch tube detection process, when the voltage across the first capacitor C1 and the second capacitor C2 is zero, the controller controls the first switch tubes in each bridge arm to remain turned on, for example, the first switch tube Q11, the first switch tube Q21, the first switch tube Q31 and the first switch tube Q41 are controlled to be turned on. Then the slow-start switch K1 is controlled to be turned on to turn on the connection between the first capacitor C1 and the second capacitor C2 and the DC power supply, at which time the first capacitor C1 and the second capacitor C2 are charged based on the DC power provided by the DC power supply. The above-mentioned slow-start circuit may be connected in parallel with a switch K2, and the switch K2 is used to be turned on after the fault switch tube detection is completed to turn on the connection between the power converter and the DC power supply. Here, since the slow-start circuit includes a resistor R, the resistor R can limit the impact current when the power converter is powered on, so that during the charging process of the first capacitor C1 and the second capacitor C2, the voltage change rate at both ends is less than the set threshold, thereby avoiding instantaneous voltage jumps at both ends of the first capacitor C1 and the second capacitor C2. In addition, it prevents the connection of a large current when there is a short-circuited switch tube in the bridge arm, causing overcurrent damage to some switch tubes. The controller is also used to determine that the third switch tube in at least one of the multiple bridge arms is short-circuited when it is detected that the first capacitor C1 is charged and the voltage at both ends is not synchronously boosted, or the voltage at both ends of the first capacitor C1 does not reach the voltage threshold, and output information about the short circuit of the third switch tube. For example, taking the short circuit of the third switch tube Q13 in the A-phase bridge arm as an example, see Figure 8 , Figure 8 Schematic diagram of a short circuit of a switch tube of a power converter provided by the present application. Figure 8As shown, after the controller controls the first switch tube Q11, the first switch tube Q21, the first switch tube Q31 and the first switch tube Q41 to be turned on, the slow-start switch K1 is controlled to be turned on to connect the first capacitor C1 and the second capacitor C2 to the DC power supply, and the first capacitor C1 and the second capacitor C2 are charged based on the DC power provided by the DC power supply. If the third switch tube Q13 is short-circuited and the second switch tube Q12 is disconnected, the diode connected in parallel with the second switch tube Q12 can conduct the current flowing from the connection end of the first switch tube Q11 and the fourth switch tube Q14 to the connection end of the first capacitor C1 and the second capacitor C2. Therefore, the third switch tube Q13 and the second switch tube Q12 cannot cut off the current flowing from the connection end of the first switch tube Q11 and the fourth switch tube Q14 to the connection end of the first capacitor C1 and the second capacitor C2. The first capacitor C1 is short-circuited, and the short-circuit current Ia flows out from the positive DC bus BUS+ and flows to the second capacitor C2 through the first switch tube Q11, the second switch tube Q12 and the third switch tube Q13 in sequence. The first capacitor C1 cannot be charged normally, but the second capacitor C2 can be charged normally. The controller is also used to determine that at least one of the fourth switch tubes in the multiple bridge arms is short-circuited, and output information about the fourth switch tube short-circuiting, when it is detected that the voltages at both ends of the first capacitor C1 and the second capacitor C2 are not synchronously boosted after the first capacitor C1 and the second capacitor C2 are charged, or the voltages at both ends of the first capacitor C1 and the second capacitor C2 do not reach the voltage threshold. Fig. 9 , Fig. 9 is another schematic diagram of a short circuit of a switch tube of a power converter provided by the present application. Fig. 9 As shown, after the controller controls the first switch tube Q11, the first switch tube Q21, the first switch tube Q31 and the first switch tube Q41 to be turned on, the slow-start switch K1 is controlled to be turned on to connect the first capacitor C1 and the second capacitor C2 with the DC power supply, and the first capacitor C1 and the second capacitor C2 are charged based on the DC power provided by the DC power supply. If the fourth switch tube Q14 is short-circuited, the fourth switch tube Q14 cannot cut off the current flowing from the positive DC bus BUS+ to the negative DC bus BUS-, the first capacitor C1 and the second capacitor C2 are short-circuited, and the short-circuit current Ib flows out from the positive DC bus BUS+, and flows to the negative DC bus BUS- through the first switch tube Q11 and the fourth switch tube Q14 in sequence, and the first capacitor C1 and the second capacitor C2 cannot be charged normally.

[0038] In some feasible implementations, the controller is used to control the fourth switch tube in each bridge arm to remain turned on and then control the slow-start switch to turn on when the voltage across the first capacitor and the second capacitor is zero, so as to connect the first capacitor and the second capacitor to the DC power supply so as to charge the first capacitor and the second capacitor through the DC power supply. The controller is also used to output information that the second switch tube is short-circuited when the voltage across the second capacitor has not reached the voltage threshold after the second capacitor has been charged, or output information that the first switch tube is short-circuited when the voltage across the first capacitor and the second capacitor has not reached the voltage threshold after the first capacitor and the second capacitor have been charged. See again Figure 7 In the process of fault switch tube detection, when the voltage across the first capacitor C1 and the second capacitor C2 is zero, the controller controls the fourth switch tube in each bridge arm to remain turned on, for example, the fourth switch tube Q14, the fourth switch tube Q24, the fourth switch tube Q34 and the fourth switch tube Q44 are turned on. Then the slow-start switch K1 is controlled to be turned on to turn on the connection between the first capacitor C1 and the second capacitor C2 and the DC power supply, at which time the first capacitor C1 and the second capacitor C2 are charged based on the DC power provided by the DC power supply. Here, since the slow-start circuit includes a resistor R, the resistor R can limit the impact current when the power converter is powered on, so that the voltage change rate across the first capacitor C1 and the second capacitor C2 is less than the set threshold during the charging process, avoiding the instantaneous voltage jump across the first capacitor C1 and the second capacitor C2. In addition, it prevents the bridge arm from being damaged by overcurrent due to the large current when a short-circuited switch tube is connected. The controller is also used to determine that the second switch tube of at least one of the multiple bridge arms is short-circuited when it is detected that the voltage across the second capacitor C2 is not synchronously boosted after the second capacitor C2 is charged, or the voltage across the second capacitor C2 does not reach the voltage threshold, and output information about the second switch tube short-circuit. For example, taking the second switch tube Q12 in the A-phase bridge arm as an example, see Fig.10 , Fig.10 is another schematic diagram of a short circuit of a switch tube of a power converter provided by the present application. Fig.10As shown, after the controller controls the fourth switch tube Q14, the fourth switch tube Q24, the fourth switch tube Q34 and the fourth switch tube Q44 to be turned on, the slow-start switch K1 is controlled to be turned on to connect the first capacitor C1 and the second capacitor C2 with the DC power supply, and the first capacitor C1 and the second capacitor C2 are charged based on the DC power provided by the DC power supply. If the second switch tube Q12 is short-circuited and the third switch tube Q13 is disconnected, the diode connected in parallel with the third switch tube Q13 can conduct the current flowing from the connection end of the first capacitor C1 and the second capacitor C2 to the connection end of the first switch tube Q11 and the fourth switch tube Q14. Therefore, the second switch tube Q12 and the third switch tube Q13 cannot cut off the current flowing from the connection end of the first capacitor C1 and the second capacitor C2 to the connection end of the first switch tube Q11 and the fourth switch tube Q14. The second capacitor C2 is short-circuited, and the short-circuit current Ic flows out from the positive DC bus BUS+, passes through the first capacitor C1, and sequentially flows through the third switch tube Q13, the second switch tube Q12, and the fourth switch tube Q14 to the negative DC bus BUS-. The second capacitor C2 cannot be charged normally, but the first capacitor C1 can be charged normally. The controller is also used to determine that at least one of the first switch tubes in the multiple bridge arms is short-circuited, and output information about the first switch tube short-circuiting when it is detected that the first capacitor C1 and the second capacitor C2 are charged and the voltages at both ends are not synchronously boosted, or the voltages at both ends of the first capacitor C1 and the second capacitor C2 do not reach the voltage threshold. Fig. 9 , when the controller controls the fourth switch tube Q14, the fourth switch tube Q24, the fourth switch tube Q34 and the fourth switch tube Q44 to be turned on, the slow-start switch K1 is controlled to be turned on to connect the first capacitor C1 and the second capacitor C2 with the DC power supply, and the first capacitor C1 and the second capacitor C2 are charged based on the DC power provided by the DC power supply. If the first switch tube Q11 is short-circuited, the first switch tube Q11 cannot cut off the current flowing from the positive DC bus BUS+ to the negative DC bus BUS-, the first capacitor C1 and the second capacitor C2 are short-circuited, and the short-circuit current Ib flows out from the positive DC bus BUS+, and flows to the negative DC bus BUS- through the first switch tube Q11 and the fourth switch tube Q14 in sequence, and the first capacitor C1 and the second capacitor C2 cannot be charged normally.

[0039] Optionally, during the fault switch tube detection process, the controller may first control the first switch tube in each bridge arm to remain turned on, control the slow-start switch to be turned on so that the first capacitor and the second capacitor are charged, and perform short-circuit fault detection on the third switch tube and the fourth switch tube in each bridge arm based on the voltage change at both ends of the first capacitor and the second capacitor. If the third switch tube and the fourth switch tube in each bridge arm are normal, the slow-start switch is controlled to be turned off so that the first capacitor and the second capacitor are discharged until the voltage at both ends is zero. Next, the controller controls the fourth switch tube in each bridge arm to remain turned on, controls the slow-start switch to be turned on so that the first capacitor and the second capacitor are charged, and performs short-circuit fault detection on the first switch tube and the second switch tube in each bridge arm based on the voltage change at both ends of the first capacitor and the second capacitor, thereby completing the fault detection of all switch tubes in each bridge arm.

[0040] Optionally, during the fault switch tube detection process, the controller may first control the fourth switch tube in each bridge arm to remain turned on, control the slow-start switch to be turned on so that the first capacitor and the second capacitor are charged, and perform short-circuit fault detection on the first switch tube and the second switch tube in each bridge arm based on the voltage change at both ends of the first capacitor and the second capacitor. If the first switch tube and the second switch tube in each bridge arm are normal, the slow-start switch is controlled to be turned off so that the first capacitor and the second capacitor are discharged until the voltage at both ends is zero. Next, the first switch tube in each bridge arm is controlled to remain turned on, the slow-start switch is controlled to be turned on so that the first capacitor and the second capacitor are charged, and the third switch tube and the fourth switch tube in each bridge arm are detected for short circuit faults based on the voltage change at both ends of the first capacitor and the second capacitor, thereby completing the fault detection of all switch tubes in each bridge arm.

[0041] In some feasible implementations, a discharge circuit may be connected in parallel across the first capacitor and the second capacitor in the power converter, and when the controller controls the slow-start switch to be disconnected so that the first capacitor and the second capacitor are discharged, the discharge circuit may be used to accelerate the discharge of the first capacitor and the second capacitor until the voltage across the first capacitor and the second capacitor is zero. Here, the discharge circuit may include at least one resistor, or the discharge circuit may be an auxiliary power supply, which is used to accelerate the energy consumption rate of the first capacitor and the second capacitor during the discharge of the first capacitor and the second capacitor.

[0042] In some feasible implementations, when the controller controls the first switch tube in each bridge arm to remain turned on, controls the slow-start switch to be turned on so that the first capacitor and the second capacitor are charged, and performs short-circuit fault detection on the third switch tube and the fourth switch tube in each bridge arm based on the voltage change across the first capacitor and the second capacitor. If the above-mentioned first switch tube is disconnected, after the controller controls the first switch tube in the bridge arm to remain turned on, no current can flow through the first switch tube, resulting in that when the fourth switch tube is short-circuited, the first capacitor and the second capacitor can still be boosted normally, that is, after the first capacitor and the second capacitor are charged, the voltage across them is greater than or equal to the voltage threshold. Figure 7 Taking the power converter shown as an example, if the first switch tube Q11 in the A-phase bridge arm is disconnected, after controlling the first switch tube Q11 to remain turned on, no current can flow through the first switch tube Q11, resulting in that when the fourth switch tube Q14 is short-circuited, the slow-start switch is controlled to be turned on so that the first capacitor C1 and the second capacitor C2 are charged, and the first capacitor C1 and the second capacitor C2 can still be boosted normally. If the fourth switch tube Q14 cannot be detected normally due to the disconnection of the first switch tube Q11, a short-circuit loop will be formed due to the short circuit of the fourth switch tube Q14 during normal operation of the power converter, so that the second capacitor C2 cannot be charged normally and some switches are subjected to excessive short-circuit current. If the first switch tube Q11 is disconnected and the second switch tube Q12 or the third switch tube Q13 is short-circuited, a short-circuit loop will not be formed during normal operation of the power converter to damage the device. Therefore, when the voltages at both ends of the first capacitor C1 and the second capacitor C2 are greater than or equal to the voltage threshold after the first capacitor C1 and the second capacitor C2 are charged, a secondary short-circuit fault detection is performed on the fourth switch tube Q14. Specifically, after controlling the first switch tube Q11 to remain turned on, the controller controls the slow-start switch to be turned on to connect the first capacitor C1 and the second capacitor C2 to the DC power supply so as to charge the first capacitor C1 and the second capacitor C2 through the DC power supply. If the voltage across the first capacitor C1 and the voltage across the second capacitor C2 are both greater than or equal to the voltage threshold, the controller controls the slow-start switch to be turned off to disconnect the first capacitor C1 and the second capacitor C2 from the DC power supply, so that the above-mentioned discharge circuit discharges the first capacitor C1 and the second capacitor C2. When the first capacitor C1 and the second capacitor C2 are discharged until the voltage at both ends is zero, the second switch tube Q12 is controlled to remain turned on, and the slow-start switch is controlled to be turned on, so as to connect the first capacitor C1 and the second capacitor C2 with the DC power supply so as to charge the first capacitor C1 and the second capacitor C2 through the DC power supply. At this time, if the fourth switch tube Q14 is short-circuited, the second capacitor C2 is short-circuited, and the short-circuit current flows out from the positive DC bus BUS+ and flows to the negative DC bus BUS- through the first capacitor C1, the third switch tube Q13, the second switch tube Q12 and the fourth switch tube Q14 in sequence. The second capacitor C2 cannot be charged normally. The specific short-circuit path situation can be referred to the above Fig.10After the second capacitor is charged and the voltage at both ends does not reach the voltage threshold, the controller outputs information that the fourth switch tube is short-circuited, which can avoid the inability to normally detect whether the fourth switch tube is short-circuited when the first switch tube is disconnected, thereby improving the accuracy of switch tube short-circuit fault detection.

[0043] Similarly, when the controller controls the fourth switch tube in each bridge arm to remain turned on, controls the slow-start switch to be turned on so that the first capacitor and the second capacitor are charged, and performs short-circuit fault detection on the first switch tube and the second switch tube in each bridge arm based on the voltage change across the first capacitor and the second capacitor. If the fourth switch tube is disconnected, then after the controller controls the fourth switch tube in the bridge arm to remain turned on, no current can flow through the fourth switch tube, resulting in that when the first switch tube is short-circuited, the first capacitor and the second capacitor can still be boosted normally, that is, after the first capacitor and the second capacitor are charged, the voltage across them is greater than or equal to the voltage threshold. Figure 7Taking the power converter shown as an example, if the fourth switch tube Q14 in the A-phase bridge arm is disconnected, after controlling the fourth switch tube Q14 to remain turned on, no current can flow through the fourth switch tube Q14, resulting in the first switch tube Q11 being short-circuited. The slow-start switch is controlled to be turned on so that the first capacitor C1 and the second capacitor C2 are charged, and the first capacitor C1 and the second capacitor C2 can still be boosted normally. If the first switch tube Q11 cannot be detected normally due to the disconnection of the fourth switch tube Q14, a short-circuit loop will be formed due to the short circuit of the first switch tube Q11 during normal operation of the power converter, so that the first capacitor C1 cannot be charged normally and some switches are subjected to excessive short-circuit current. Therefore, when the voltages at both ends of the first capacitor C1 and the second capacitor C2 are greater than or equal to the voltage threshold after the first capacitor C1 and the second capacitor C2 are charged, the first switch tube Q11 is detected for a short-circuit fault separately. Specifically, after controlling the fourth switch tube Q14 to remain turned on, the controller controls the slow-start switch to be turned on to connect the first capacitor C1 and the second capacitor C2 to the DC power supply so as to charge the first capacitor C1 and the second capacitor C2 through the DC power supply. If the voltage across the first capacitor C1 and the voltage across the second capacitor C2 are both greater than or equal to the voltage threshold, the controller controls the slow-start switch to be turned off to disconnect the first capacitor C1 and the second capacitor C2 from the DC power supply, so that the above-mentioned discharge circuit discharges the first capacitor C1 and the second capacitor C2, and the first capacitor C1 and the second capacitor C2 are charged. When C2 is discharged until the voltage at both ends is zero, the third switch tube Q13 is controlled to remain turned on, and the slow-start switch is controlled to be turned on, so as to connect the first capacitor C1 and the second capacitor C2 with the DC power supply so as to charge the first capacitor C1 and the second capacitor C2 through the DC power supply. At this time, if the first switch tube Q11 is short-circuited, the first capacitor C1 is short-circuited, and the short-circuit current flows out from the positive DC bus BUS+, and flows to the second capacitor C2 through the first capacitor C1, the second switch tube Q12, and the third switch tube Q13 in sequence. The first capacitor C1 cannot be charged normally. The specific short-circuit path situation can be referred to the above Fig.10 After the first capacitor is charged and the voltage at both ends does not reach the voltage threshold, the controller outputs information that the first switch tube is short-circuited, which can avoid the failure to normally detect whether the first switch tube is short-circuited due to the disconnection of the fourth switch tube, thereby improving the accuracy of the switch tube short-circuit fault detection.

[0044] In some feasible implementations, the controller is used to control the first switch tube in each bridge arm to remain turned on, control the slow-start switch to be turned on so that the first capacitor and the second capacitor are charged, and perform short-circuit fault detection on the third switch tube and the fourth switch tube in each bridge arm based on the voltage change at both ends of the first capacitor and the second capacitor, or control the fourth switch tube in each bridge arm to remain turned on, control the slow-start switch to be turned on so that the first capacitor and the second capacitor are charged, and perform short-circuit fault detection on the first switch tube and the second switch tube in each bridge arm based on the voltage change at both ends of the first capacitor and the second capacitor. If it is detected that the first switch tube or the fourth switch tube does not have a short-circuit fault, a secondary short-circuit fault detection can be performed on the first switch tube or the fourth switch tube to avoid misjudgment of a short-circuit fault caused by a disconnection of the first switch tube or the fourth switch tube. Specifically, after controlling the first switch tube or the fourth switch tube in each bridge arm to remain turned on, the controller controls the slow-start switch to be turned on to connect the first capacitor and the second capacitor to the DC power supply so as to charge the first capacitor and the second capacitor through the DC power supply. If the voltage across the first capacitor and the voltage across the second capacitor are both greater than or equal to the voltage threshold, the controller controls the slow-start switch to be turned off to disconnect the first capacitor and the second capacitor from the DC power supply so that the above-mentioned discharge circuit discharges the first capacitor and the second capacitor, and when the first capacitor and the second capacitor are discharged to the voltage across the two ends being zero, the controller controls the slow-start switch to be turned on to connect the first capacitor and the second capacitor to the DC power supply so as to charge the first capacitor and the second capacitor through the DC power supply. At this time, the switch tubes in each bridge arm are all in the off state. If the first switch tube and the fourth switch tube are short-circuited, the first capacitor and the second capacitor are short-circuited, and the short-circuit current flows out from the positive DC bus and flows to the negative DC bus through the first switch tube and the fourth switch tube in turn. The first capacitor and the second capacitor cannot be charged normally. The specific short-circuit path situation can be referred to the above Fig. 9 Description. If the voltage across the first capacitor and the voltage across the second capacitor do not reach the voltage threshold, the controller outputs information that the first switch tube and the fourth switch tube are short-circuited. Furthermore, if after the first capacitor and the second capacitor are charged, the voltage across the filter capacitor connected to any bridge arm is equal to the voltage across the first capacitor or the second capacitor, the information that the first switch tube or the fourth switch tube is short-circuited is output. Specifically, if the voltage across the filter capacitor connected to any bridge arm is equal to the voltage across the first capacitor, the information that the first switch tube is short-circuited is output; if the voltage across the filter capacitor connected to any bridge arm is equal to the voltage across the second capacitor, the information that the fourth switch tube is short-circuited is output. Please refer to the above again. Figure 6In the power converter shown, after the first capacitor C1 and the second capacitor C2 are charged, if the voltage across the filter inductor L1 connected to the A-phase bridge arm is equal to the voltage across the first capacitor C1, it is determined that the first switch tube Q11 in the A-phase bridge arm is short-circuited, so that the first capacitor C1 and the filter inductor L1 are connected in parallel, and the information that the first switch tube is short-circuited is output. Alternatively, if the voltage across the filter inductor L1 connected to the A-phase bridge arm is equal to the voltage across the second capacitor C2, it is determined that the second switch tube Q12 in the A-phase bridge arm is short-circuited, so that the second capacitor C2 and the filter inductor L1 are connected in parallel, and the information that the second switch tube is short-circuited is output.

[0045] In some feasible implementations, the power converter further includes an electric energy transfer unit. The controller is used to control the electric energy transfer unit to discharge one of the first capacitor and the second capacitor after the third switch tube and the fourth switch tube in each bridge arm are short-circuit fault detected, and then charge the discharged first capacitor or the second capacitor to detect the short-circuit fault of the first switch tube or the second switch tube. Specifically, the controller controls the first switch tube in each bridge arm to remain turned on, controls the slow-start switch to be turned on so that the first capacitor and the second capacitor are charged, and performs short-circuit fault detection on the third switch tube and the fourth switch tube in each bridge arm based on the voltage change at both ends of the first capacitor and the second capacitor. If the first capacitor and the second capacitor are charged and the voltage at both ends is greater than or equal to the voltage threshold, that is, the third switch tube and the fourth switch tube in each bridge arm are normal, the controller controls the electric energy transfer unit to discharge the first capacitor through the electric energy transfer unit. When the first capacitor is discharged to the voltage at both ends is zero, the controller controls the third switch tube in each bridge arm to remain turned on, and controls the electric energy transfer unit to charge the first capacitor through the electric energy transfer unit. After the first capacitor is charged and the voltage at both ends does not reach the voltage threshold, the controller outputs information that the first switch tube is short-circuited. Alternatively, when the third switch tube and the fourth switch tube in each bridge arm are normal, the controller controls the above-mentioned power transfer unit to discharge the second capacitor through the power transfer unit. When the second capacitor is discharged to a voltage of zero at both ends, the controller controls the fourth switch tube in each bridge arm to remain turned on, and controls the power transfer unit to charge the second capacitor through the power transfer unit. After the second capacitor is charged and the voltage at both ends does not reach the voltage threshold, the controller outputs information that the second switch tube is short-circuited.

[0046] It can be understood that when the controller performs short-circuit fault detection on the third switch tube and the fourth switch tube in each bridge arm, and the third switch tube and the fourth switch tube in each bridge arm are normal, the controller can first perform short-circuit fault detection on the first switch tube in each bridge arm, and then perform short-circuit fault detection on the second switch tube in each bridge arm, thereby completing the fault detection of all switch tubes in each bridge arm. Alternatively, the controller can also first perform short-circuit fault detection on the second switch tube in each bridge arm, and then perform short-circuit fault detection on the first switch tube in each bridge arm, thereby completing the fault detection of all switch tubes in each bridge arm. Taking the example of first performing short-circuit fault detection on the first switch tube in each bridge arm, and then performing short-circuit fault detection on the second switch tube in each bridge arm, specifically, the above-mentioned power transfer unit can be a balanced bridge arm, and the balanced bridge arm includes an inductor, a fifth switch tube and a sixth switch tube connected in series, the fifth switch tube is connected to the positive DC bus, the sixth switch tube is connected to the negative DC bus, and the connection end of the fifth switch tube and the sixth switch tube is connected to the connection end of the first capacitor and the second capacitor through the inductor. Please refer to Fig.11 , Fig.11 is another schematic diagram of the structure of the power converter provided by the present application. Fig.11 As shown, Fig.11 The power converter in the embodiment includes four bridge arms, and the structure of each bridge arm can refer to the above Figure 5The power converter may further include a slow-start circuit and an electric energy transfer unit, wherein the slow-start circuit includes a slow-start switch K1 and a resistor R, and the slow-start switch K1 and the resistor R may be connected in series to the positive DC bus BUS+. The electric energy transfer unit may be a balanced bridge arm, wherein the balanced bridge arm includes an inductor L0, a switch tube Q5 and a switch tube Q6 connected in series, wherein the switch tube Q5 is connected to the positive DC bus BUS+, and the switch tube Q6 is connected to the negative DC bus BUS-, and the connection end of the switch tube Q5 and the switch tube Q6 is connected to the connection end of the first capacitor C1 and the second capacitor C2 through the inductor L0. When the controller completes the short-circuit fault detection of the third switch tube and the fourth switch tube in each bridge arm, and the third switch tube and the fourth switch tube in each bridge arm are normal, the voltages at both ends of the first capacitor C1 and the second capacitor C2 after charging are greater than or equal to the voltage threshold, and the controller may control the switch tube Q5 and the switch tube Q6 to act, so as to transfer the electric energy of the first capacitor C1 to the second capacitor C2 through the inductor L0, so as to discharge the first capacitor C1. When the first capacitor C1 is discharged to the voltage at both ends being zero, the controller controls the third switch tubes in each bridge arm to remain turned on, that is, controls the third switch tubes Q13, Q23, Q33 and Q43 to be turned on. Then, the switch tubes Q5 and Q6 are controlled to act so that the electric energy of the second capacitor C2 is transferred to the first capacitor C1 through the inductor L0 to charge the first capacitor C1. After the first capacitor C1 is charged and the voltage at both ends does not reach the voltage threshold, the controller determines that the first switch tube of at least one of the multiple bridge arms is short-circuited, and outputs the information that the first switch tube is short-circuited. After the first capacitor C1 is charged, the voltage at both ends is greater than or equal to the voltage threshold, that is, the first switch tubes in each bridge arm are normal, then the controller controls the switch tubes Q5 and Q6 to act so as to transfer the electric energy of the second capacitor C2 to the first capacitor C1 through the inductor L0 to discharge the second capacitor C2. When the second capacitor C2 of the controller is discharged to the voltage at both ends being zero, the fourth switch tube in each bridge arm is controlled to remain turned on, that is, the fourth switch tube Q14, the fourth switch tube Q24, the fourth switch tube Q34 and the fourth switch tube Q44 are controlled to be turned on. Then the switch tube Q5 and the switch tube Q6 are controlled to act so that the electric energy of the first capacitor C1 is transferred to the second capacitor C2 through the inductor L0 to charge the second capacitor C2. After the second capacitor C2 is charged and the voltage at both ends does not reach the voltage threshold, the controller determines that the second switch tube of at least one bridge arm among the multiple bridge arms is short-circuited, and outputs the information of the second switch tube short-circuit, thereby completing the fault detection of all the switch tubes in each bridge arm.

[0047] Further, when the controller controls the first switch tube in each bridge arm to remain turned on, controls the slow-start switch to be turned on so that the first capacitor and the second capacitor are charged, and performs short-circuit fault detection on the third switch tube and the fourth switch tube in each bridge arm based on the voltage change at both ends of the first capacitor and the second capacitor. If the first switch tube is disconnected, the controller controls the first switch tube in the bridge arm to remain turned on, and the current cannot flow through the first switch tube, resulting in that when the fourth switch tube is short-circuited, the first capacitor and the second capacitor can still be boosted normally, that is, the voltage at both ends of the first capacitor and the second capacitor after charging is greater than or equal to the voltage threshold, and there is also a situation where the fourth switch tube short-circuit fault is misjudged. Therefore, after the above-mentioned fault detection is performed on all the switch tubes in each bridge arm, the fourth switch tube is subjected to secondary short-circuit fault detection. Specifically, the controller can control the switch tubes Q5 and Q6 to act to transfer the electric energy of the second capacitor C2 to the first capacitor C1 through the inductor L0 to discharge the second capacitor C2. When the second capacitor C2 is discharged to the voltage at both ends being zero, the controller controls the second switch tubes in each bridge arm to remain turned on, that is, controls the second switch tubes Q12, Q22, Q32 and Q42 to be turned on. Then the switch tubes Q5 and Q6 are controlled to act so that the electric energy of the first capacitor C1 is transferred to the second capacitor C2 through the inductor L0 to charge the second capacitor C2. After the second capacitor C2 is charged and the voltage at both ends does not reach the voltage threshold, the controller determines that the fourth switch tube of at least one of the multiple bridge arms is short-circuited, and outputs the information that the fourth switch tube is short-circuited.

[0048] In some feasible implementations, when the controller performs short-circuit fault detection on the first switch tube and the second switch tube in each bridge arm, and the first switch tube and the second switch tube in each bridge arm are normal, the controller may first perform short-circuit fault detection on the third switch tube in each bridge arm, and then perform short-circuit fault detection on the fourth switch tube in each bridge arm, thereby completing fault detection on all switch tubes in each bridge arm. Alternatively, the controller may first perform short-circuit fault detection on the fourth switch tube in each bridge arm, and then perform short-circuit fault detection on the third switch tube in each bridge arm, thereby completing fault detection on all switch tubes in each bridge arm. Taking the example of first performing short-circuit fault detection on the third switch tube in each bridge arm, and then performing short-circuit fault detection on the fourth switch tube in each bridge arm, specifically, the above-mentioned power transfer unit may be a balanced bridge arm, and the balanced bridge arm includes an inductor, a fifth switch tube and a sixth switch tube connected in series, the fifth switch tube is connected to the positive DC bus, the sixth switch tube is connected to the negative DC bus, and the connection end of the fifth switch tube and the sixth switch tube is connected to the connection end of the first capacitor and the second capacitor through the inductor. Please refer again Fig.11, when the controller completes the short-circuit fault detection of the first switch tube and the second switch tube in each bridge arm, and the first switch tube and the second switch tube in each bridge arm are normal, the voltages at both ends of the first capacitor C1 and the second capacitor C2 after charging are greater than or equal to the voltage threshold, and the controller can control the switch tubes Q5 and Q6 to act, so as to transfer the electric energy of the first capacitor C1 to the second capacitor C2 through the inductor L0, so as to discharge the first capacitor C1. When the controller discharges the first capacitor C1 to zero voltage at both ends, the controller controls the first switch tubes in each bridge arm to remain turned on, that is, controls the first switch tubes Q11, the first switch tubes Q21, the first switch tubes Q31 and the first switch tubes Q41 to be turned on. Then, the switch tubes Q5 and Q6 are controlled to act, so that the electric energy of the second capacitor C2 is transferred to the first capacitor C1 through the inductor L0, so as to charge the first capacitor C1. After the first capacitor C1 is charged and the voltage at both ends does not reach the voltage threshold, the controller determines that the third switch tube of at least one of the multiple bridge arms is short-circuited, and outputs the information that the third switch tube is short-circuited. If the voltage at both ends of the first capacitor C1 after charging is greater than or equal to the voltage threshold, that is, the third switch tube in each bridge arm is normal, the controller controls the switch tube Q5 and the switch tube Q6 to act, so as to transfer the electric energy of the second capacitor C2 to the first capacitor C1 through the inductor L0, so as to discharge the second capacitor C2. When the second capacitor C2 is discharged to the voltage at both ends is zero, the controller controls the second switch tubes in each bridge arm to remain turned on, that is, the second switch tube Q12, the second switch tube Q22, the second switch tube Q32 and the second switch tube Q42 are turned on. Then the switch tube Q5 and the switch tube Q6 are controlled to act, so that the electric energy of the first capacitor C1 is transferred to the second capacitor C2 through the inductor L0, so as to charge the second capacitor C2. After the second capacitor C2 is charged and the voltage at both ends does not reach the voltage threshold, the controller determines that the fourth switch tube of at least one of the multiple bridge arms is short-circuited, and outputs the information of the fourth switch tube short-circuiting, thereby completing the fault detection of all the switch tubes in each bridge arm.

[0049] Further, when the controller controls the fourth switch tube in each bridge arm to remain turned on, controls the slow-start switch to be turned on so that the first capacitor and the second capacitor are charged, and performs short-circuit fault detection on the first switch tube and the second switch tube in each bridge arm based on the voltage change at both ends of the first capacitor and the second capacitor. If the fourth switch tube is disconnected, after the controller controls the fourth switch tube in the bridge arm to remain turned on, the fourth switch tube cannot flow current, resulting in the first capacitor and the second capacitor still being able to boost the voltage normally when the first switch tube is short-circuited, that is, the voltage at both ends of the first capacitor and the second capacitor after charging is greater than or equal to the voltage threshold, and there is also a misjudgment of the short-circuit fault of the first switch tube. Therefore, after the above-mentioned fault detection is performed on all the switch tubes in each bridge arm, the first switch tube is subjected to secondary short-circuit fault detection. Specifically, the controller can control the switch tubes Q5 and Q6 to act to transfer the electric energy of the first capacitor C1 to the second capacitor C2 through the inductor L0 to discharge the first capacitor C1. When the controller discharges the first capacitor C1 until the voltage at both ends is zero, the controller controls the third switch tubes in each bridge arm to remain turned on, that is, controls the third switch tubes Q13, Q23, Q33 and Q43 to be turned on. Then the switch tubes Q5 and Q6 are controlled to act so that the electric energy of the second capacitor C2 is transferred to the first capacitor C1 through the inductor L0 to charge the first capacitor C1. After the first capacitor C1 is charged and the voltage at both ends does not reach the voltage threshold, the controller determines that the first switch tube of at least one of the multiple bridge arms is short-circuited, and outputs the information that the first switch tube is short-circuited.

Claims

1. A power converter, characterized in that: The power converter comprises a controller, at least one bridge arm, and a first capacitor and a second capacitor connected in series, wherein the first capacitor is connected to a positive DC bus, and the second capacitor is connected to a negative DC bus; Each bridge arm in the at least one bridge arm comprises a first switch tube, a second switch tube, a third switch tube and a fourth switch tube, wherein the first switch tube and the fourth switch tube are connected in series and then connected in parallel at both ends of the first capacitor and the second capacitor in series, and the connection end of the first switch tube and the fourth switch tube is connected to the connection end of the first capacitor and the second capacitor through the second switch tube and the third switch tube connected in reverse series; The controller is used to control the target switch tubes in each bridge arm to remain turned on after the power converter is turned on, wherein the switch tubes other than the target switch tube in each bridge arm remain turned off, and the target capacitor starts to charge after the target switch tube in each bridge arm is turned on, the target capacitor is at least one of the first capacitor and the second capacitor, and the target switch tube is at least one of the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube in each bridge arm; The controller is also used to output information that a switch tube short-circuit fault exists in each bridge arm when the voltage across the target capacitor does not reach a voltage threshold after the target capacitor is charged.

2. The power converter according to claim 1, characterized in that: The power converter includes a slow-start switch and a resistor connected in series to the positive DC bus or the negative DC bus; the target capacitor is the first capacitor and the second capacitor, and the target switch tube is the first switch tube in each bridge arm; The target capacitor starts to be charged after the target switch tube in each bridge arm is turned on, specifically: After the first switch tubes in the bridge arms remain turned on, the controller controls the slow-start switch to turn on, so as to connect the first capacitor and the second capacitor to the DC power supply, so as to start charging the first capacitor and the second capacitor through the DC power supply; The controller is also used to output information that the third switch tube is short-circuited after the DC power supply charges the first capacitor and the second capacitor and the voltage across the first capacitor does not reach a voltage threshold, or to output information that the fourth switch tube is short-circuited after the DC power supply charges the first capacitor and the second capacitor and the voltage across the first capacitor and the voltage across the second capacitor do not reach the voltage threshold.

3. The power converter according to claim 1, characterized in that: The power converter includes a slow-start switch and a resistor connected in series to the positive DC bus or the negative DC bus; the target capacitor is the first capacitor and the second capacitor, and the target switch tube is the fourth switch tube in each bridge arm; The target capacitor starts to be charged after the target switch tube in each bridge arm is turned on, specifically: After the fourth switch tubes in each bridge arm remain turned on, the controller controls the slow-start switch to turn on, so as to connect the first capacitor and the second capacitor to the DC power supply, so as to start charging the first capacitor and the second capacitor through the DC power supply; The controller is further used for controlling the slow-start switch to be turned on after controlling the fourth switch tube in each bridge arm to remain turned on, so as to connect the first capacitor and the second capacitor to the DC power supply so as to charge the first capacitor and the second capacitor through the DC power supply; The controller is also used to output information that the second switch tube is short-circuited after the DC power supply charges the first capacitor and the second capacitor and the voltage across the second capacitor does not reach a voltage threshold, or to output information that the first switch tube is short-circuited after the DC power supply charges the first capacitor and the second capacitor and the voltage across the first capacitor and the voltage across the second capacitor do not reach the voltage threshold.

4. The power converter according to claim 2, characterized in that: A discharge circuit is connected in parallel at both ends of the first capacitor and the second capacitor, and the controller is used to control the slow-start switch to be turned on to connect the first capacitor and the second capacitor to the DC power supply so as to charge the first capacitor and the second capacitor through the DC power supply. If the voltage across the first capacitor and the voltage across the second capacitor are both greater than or equal to the voltage threshold, the first switch tube is controlled to be disconnected, and the slow-start switch is controlled to be disconnected to disconnect the first capacitor and the second capacitor from the DC power supply, so that the discharge circuit discharges the first capacitor and the second capacitor, and when the first capacitor and the second capacitor are discharged to the voltage across both ends being zero, the second switch tubes in each bridge arm are controlled to remain turned on, and the slow-start switch is controlled to be turned on to turn on the connection between the first capacitor and the second capacitor and the DC power supply to charge the first capacitor and the second capacitor through the DC power supply, and after the second capacitor is charged and the voltage across both ends does not reach the voltage threshold, the information that the fourth switch tube is short-circuited is output.

5. The power converter according to claim 3, characterized in that: A discharge circuit is connected in parallel at both ends of the first capacitor and the second capacitor, and the controller is used to control the slow-start switch to be turned on to connect the first capacitor and the second capacitor to the DC power supply so as to charge the first capacitor and the second capacitor through the DC power supply. If the voltage across the first capacitor and the voltage across the second capacitor are both greater than or equal to the voltage threshold, the fourth switch tube is controlled to be disconnected, and the slow-start switch is controlled to be disconnected to disconnect the first capacitor and the second capacitor from the DC power supply, so that the discharge circuit discharges the first capacitor and the second capacitor, and when the first capacitor and the second capacitor are discharged to the voltage across both ends being zero, the third switch tubes in each bridge arm are controlled to remain turned on, and the slow-start switch is controlled to be turned on to turn on the connection between the first capacitor and the second capacitor and the DC power supply to charge the first capacitor and the second capacitor through the DC power supply, and after the first capacitor is charged and the voltage across both ends does not reach the voltage threshold, information that the first switch tube is short-circuited is output.

6. The power converter according to claim 2 or 3, characterized in that: A discharge circuit is connected in parallel at both ends of the first capacitor and the second capacitor. In each bridge arm, the connection end of the first switch tube and the fourth switch tube is also connected to the connection end of the first capacitor and the second capacitor through a filter capacitor. The controller is used to control the slow-start switch to turn on to connect the first capacitor and the second capacitor to the DC power supply so as to charge the first capacitor and the second capacitor through the DC power supply. The controller is also used to, if the voltage across the first capacitor and the voltage across the second capacitor are both greater than or equal to the voltage threshold, control the target switch tube to be disconnected, and control the slow-start switch to be disconnected, so as to disconnect the first capacitor and the second capacitor from the DC power supply, so that the discharge circuit discharges the first capacitor and the second capacitor, and when the first capacitor and the second capacitor are discharged to the voltage across the two ends being zero, control the slow-start switch to be turned on, so as to turn on the connection between the first capacitor and the second capacitor and the DC power supply to charge the first capacitor and the second capacitor through the DC power supply, and if the voltage across the first capacitor and the second capacitor does not reach the voltage threshold after the first capacitor and the second capacitor are charged, output information that the first switch tube and the fourth switch tube are short-circuited, Alternatively, the controller is also used to control the target switch tube to be disconnected, and control the slow-start switch to be disconnected, if the voltage across the first capacitor and the voltage across the second capacitor are both greater than or equal to the voltage threshold, so as to disconnect the first capacitor and the second capacitor from the DC power supply, so that the discharge circuit discharges the first capacitor and the second capacitor, and when the first capacitor and the second capacitor are discharged to the voltage across both ends being zero, control the slow-start switch to be turned on, so as to turn on the connection between the first capacitor and the second capacitor and the DC power supply to charge the first capacitor and the second capacitor through the DC power supply, and if after the first capacitor and the second capacitor are charged, the voltage across the filter capacitor is equal to the voltage across the first capacitor or the second capacitor, output information that the first switch tube or the fourth switch tube is short-circuited.

7. The power converter according to claim 2 or 3, characterized in that: The power converter further includes an electric energy transfer unit, wherein the controller is used to, after controlling the slow-start switch to be turned on to connect the first capacitor and the second capacitor to the DC power supply so as to charge the first capacitor and the second capacitor through the DC power supply, If the voltage across the first capacitor and the voltage across the second capacitor are both greater than or equal to the voltage threshold, control the target switch tube to be disconnected, and control the power transfer unit to discharge the first capacitor through the power transfer unit; The controller is further configured to, when the first capacitor is discharged through the power transfer unit until the voltage across both ends is zero, control the third switch tubes in each bridge arm to remain turned on, and control the power transfer unit to charge the first capacitor through the power transfer unit; The controller is further configured to output information that the first switch tube is short-circuited if the voltage across the first capacitor does not reach the voltage threshold after the first capacitor is charged by the power transfer unit.

8. The power converter according to claim 2, characterized in that: The power converter further includes an electric energy transfer unit, wherein the controller is used to, after controlling the slow-start switch to be turned on to connect the first capacitor and the second capacitor to the DC power supply so as to charge the first capacitor and the second capacitor through the DC power supply, If the voltage across the first capacitor and the voltage across the second capacitor are both greater than or equal to the voltage threshold, control the first switch tube to be disconnected, and control the power transfer unit to discharge the second capacitor through the power transfer unit; The controller is further configured to, when the second capacitor is discharged through the power transfer unit until the voltage across both ends is zero, control the fourth switch tube in each bridge arm to remain turned on, and control the power transfer unit to charge the second capacitor through the power transfer unit; The controller is further configured to output information that the second switch tube is short-circuited if the voltage across the second capacitor does not reach the voltage threshold after the second capacitor is charged by the power transfer unit.

9. The power converter according to claim 3, characterized in that: The power converter further includes an electric energy transfer unit; the controller is used to, after controlling the slow-start switch to turn on, so as to turn on the connection between the first capacitor and the second capacitor and the DC power supply to charge the first capacitor and the second capacitor through the DC power supply, If the voltage across the first capacitor and the voltage across the second capacitor are both greater than or equal to the voltage threshold, control the fourth switch tube to be disconnected, and control the power transfer unit to discharge the first capacitor through the power transfer unit; The controller is further configured to, when the first capacitor is discharged through the power transfer unit until the voltage across both ends is zero, control the first switch tubes in each bridge arm to remain turned on, and control the power transfer unit to charge the first capacitor through the power transfer unit; The controller is further configured to output information that the third switch tube is short-circuited if the voltage across the first capacitor does not reach the voltage threshold after the first capacitor is charged by the power transfer unit.

10. The power converter according to claim 2 or 3, characterized in that: The power converter further includes an electric energy transfer unit, wherein the controller is used to, after controlling the slow-start switch to be turned on to connect the first capacitor and the second capacitor to the DC power supply so as to charge the first capacitor and the second capacitor through the DC power supply, If the voltage across the first capacitor and the voltage across the second capacitor are both greater than or equal to the voltage threshold, control the target switch tube to be disconnected, and control the power transfer unit to discharge the second capacitor through the power transfer unit; The controller is further used to control the second switch tubes in each bridge arm to remain turned on, and control the power transfer unit to charge the second capacitor through the power transfer unit when the second capacitor is discharged through the power transfer unit until the voltage at both ends is zero; The controller is also used to output information that the fourth switch tube is short-circuited if the second capacitor is charged by the power transfer unit and the voltage across the second capacitor does not reach a voltage threshold after the second capacitor is charged.

11. The power converter according to any one of claims 7 to 10, characterized in that: The electric energy transfer unit includes an inductor, a fifth switch tube and a sixth switch tube connected in series, the fifth switch tube is connected to the positive DC bus, the sixth switch tube is connected to the negative DC bus, and the connection end of the fifth switch tube and the sixth switch tube is connected to the connection end of the first capacitor and the second capacitor through the inductor; The controlling the electric energy transfer unit to discharge the first capacitor or the second capacitor through the electric energy transfer unit is specifically: Controlling the fifth switch tube and the sixth switch tube to operate, so as to transfer the electric energy of the first capacitor to the second capacitor through the inductor to discharge the first capacitor, or to transfer the electric energy of the second capacitor to the first capacitor through the inductor to discharge the second capacitor; The controlling the electric energy transfer unit to charge the first capacitor or the second capacitor through the electric energy transfer unit specifically includes: The fifth switch tube and the sixth switch tube are controlled to operate so as to transfer the electric energy of the second capacitor to the first capacitor through the inductor to charge the first capacitor, or to transfer the electric energy of the first capacitor to the second capacitor through the inductor to charge the second capacitor.

12. The power converter according to any one of claims 1 to 11, characterized in that: During the charging process of the target capacitor, the voltage change rate across the target capacitor is less than a set threshold.

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