A power converter and control method

Abstract

The application discloses a power converter and a control method. The power converter comprises two bidirectional conversion circuits, a first switch module, a second switch module and a controller. The first ends of the two bidirectional conversion circuits are connected to the first end and the second end of the first switch module respectively, and the second ends of the two bidirectional conversion circuits are connected to the first end and the second end of the second switch module respectively. The controller is used for controlling the switch tubes of the two bidirectional conversion circuits to act before starting the machine, so that the power is transmitted back and forth between the first end and the second end of each bidirectional conversion circuit to discharge energy. After the discharging is completed, if the voltage at the third end of the first switch module is greater than or equal to a first threshold value, it is determined that the switch tube of the first switch module or the power converter is abnormal; if the voltage at at least one of the first end and the second end of the second switch module is greater than or equal to a second threshold value, it is determined that the switch tube of the second switch module or the power converter is abnormal. The scheme can realize reliable detection of the switch module through lower hardware cost.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, specifically to a power converter and control method. Background Technology

[0002] In DC photovoltaic-energy storage charging systems, in order to adapt to different input and output voltage levels, multiple conversion circuits in the power converter usually need to switch between the input and output terminals in series and parallel through switches, and the switch status is detected before startup to ensure the safe and reliable operation of the system.

[0003] To ensure the accuracy of switch status detection, residual energy in the power converter needs to be discharged before detection. Related technologies typically employ additional discharge resistors and switches to dissipate the stored electrical energy as heat. However, this approach requires additional power devices, increasing the cost and hardware complexity of the power converter. Furthermore, the discharge process generates significant power losses and thermal stress, impacting device lifespan. Summary of the Invention

[0004] In view of this, this application provides a power converter and control method that can achieve rapid and reliable discharge of residual energy without relying on additional power devices, and achieve reliable detection of the switch with low hardware cost.

[0005] To solve the above problems, the technical solution provided in this application is as follows: In a first aspect of this application, a power converter is provided, comprising: a first bidirectional conversion circuit, a second bidirectional conversion circuit, a first switching module, a second switching module, and a controller; The first terminal of the first bidirectional conversion circuit is connected to the first terminal of the first switching module, the first terminal of the second bidirectional conversion circuit is connected to the second terminal of the first switching module, and the third terminal of the first switching module is used to connect to a DC source. The second terminal of the first bidirectional conversion circuit is connected to the first terminal of the second switching module, the second terminal of the second bidirectional conversion circuit is connected to the second terminal of the second switching module, and the third terminal of the second switching module is used to connect to the load. The controller is configured to, before the power converter is started, control the switching transistor in the first bidirectional conversion circuit to operate, causing power to reciprocate between the first terminal and the second terminal of the first bidirectional conversion circuit, and control the switching transistor in the second bidirectional conversion circuit to operate, causing power to reciprocate between the first terminal and the second terminal of the second bidirectional conversion circuit, so as to discharge energy in the power converter; after the discharge is completed, in response to the voltage at the third terminal of the first switching module being greater than or equal to a first threshold, determine that the first switching module is abnormal or the switching transistor of the power converter is abnormal; or, in response to at least one of the voltage at the first terminal of the second switching module or the voltage at the second terminal of the second switching module being greater than or equal to a second threshold, determine that the second switching module is abnormal or the switching transistor of the power converter is abnormal.

[0006] In one possible implementation, the first bidirectional conversion circuit and the second bidirectional conversion circuit have the same structure; The first bidirectional conversion circuit includes a first DC circuit and a first dual active conversion circuit. The first DC circuit is connected to the first dual active conversion circuit through an intermediate bus. The primary circuit of the first dual active conversion circuit includes a first bridge arm and a second bridge arm connected in parallel. The secondary circuit of the first dual active conversion circuit includes a third bridge arm and a fourth bridge arm connected in parallel. The controller is specifically configured to sequentially turn on the first group of switches, the second group of switches, the third group of switches, and the fourth group of switches in the first dual active converter circuit at a first frequency; the first group of switches includes the upper switch of the first bridge arm and the lower switch of the second bridge arm, the second group of switches includes the upper switch of the third bridge arm and the lower switch of the fourth bridge arm, the third group of switches includes the lower switch of the first bridge arm and the upper switch of the second bridge arm, and the fourth group of switches includes the lower switch of the third bridge arm and the upper switch of the fourth bridge arm; The first frequency is higher than the operating frequency of the switching transistor in the first dual active converter circuit after the power converter is started.

[0007] In one possible implementation, the power converter further includes: a main switch and a pre-charge switch; a first terminal of the main switch is connected to the DC source, and a second terminal of the main switch is connected to the positive terminal of the third terminal of the first switch module; a first terminal of the pre-charge switch is connected to the first terminal of the main switch, and a second terminal of the pre-charge switch is connected to the second terminal of the main switch through a resistor; The first switch module includes a first series switch module and a first parallel switch module. The first series switch module includes a first switch, and the first parallel switch module includes a second switch and a third switch. The positive terminal of the first end of the first bidirectional conversion circuit is connected to the positive terminal of the first end of the second bidirectional conversion circuit through the second switch. The negative terminal of the first end of the first bidirectional conversion circuit is connected to the positive terminal of the first end of the second bidirectional conversion circuit through the first switch. The negative terminal of the first end of the first bidirectional conversion circuit is connected to the negative terminal of the first end of the second bidirectional conversion circuit through the third switch. The controller is further configured to: in response to the voltage at the third terminal of the first switching module being less than a first threshold, and the first series switching module or the first parallel switching module being normal and the precharge switch being normal, send a shutdown command to the main switch; control the switching transistor in the first bidirectional conversion circuit to operate at the first frequency, control the switching transistor in the second bidirectional conversion circuit to operate at the second frequency, and determine that the main switch is abnormal in response to the voltage at both ends of the main switch being less than or equal to a third threshold; The second frequency is higher than the operating frequency of the switching transistor in the second dual active converter circuit after the power converter is started.

[0008] In one possible implementation, the power converter further includes: a main switch and a precharge switch; The first terminal of the main switch is used to connect to the DC source, and the second terminal of the main switch is connected to the positive terminal of the third terminal of the first switch module; the first terminal of the precharge switch is used to connect to the first terminal of the main switch, and the second terminal of the precharge switch is connected to the second terminal of the main switch through a resistor; The second switch module includes a fourth switch, a fifth switch, and a sixth switch. The positive terminal of the second end of the first bidirectional conversion circuit is connected to the positive terminal of the second end of the second bidirectional conversion circuit through the fifth switch. The negative terminal of the second end of the first bidirectional conversion circuit is connected to the positive terminal of the second end of the second bidirectional conversion circuit through the fourth switch. The negative terminal of the second end of the first bidirectional conversion circuit is connected to the negative terminal of the second end of the second bidirectional conversion circuit through the sixth switch. The controller is further configured to, in response to the voltage at the first terminal of the second switching module being less than a second threshold and the voltage at the second terminal of the second switching module being less than the second threshold, the precharge switch and the main switch being normal, and the fifth switch and the sixth switch being normally engaged, send a shutdown command to the fifth switch and the sixth switch; cause the switching transistor in the first bidirectional conversion circuit to operate at the first frequency, cause the switching transistor in the second bidirectional conversion circuit to operate at the second frequency, and determine that at least one of the fifth switch or the sixth switch is abnormally shut down in response to the voltage at the third terminal of the second switching module being less than a fourth threshold; The second frequency is higher than the operating frequency of the switching transistor in the second dual active converter circuit after the power converter is started.

[0009] In one possible implementation, the controller is further configured to engage the fourth switch in response to both the fifth and sixth switches being functioning normally. When the fourth switch is engaged normally, a shutdown command is sent to the fourth switch; the switching transistor in the first bidirectional conversion circuit operates at the first frequency, and the switching transistor in the second bidirectional conversion circuit operates at the second frequency. In response to the voltage at the third terminal of the second switch module being less than the fourth threshold, the fourth switch is determined to be abnormal.

[0010] In one possible implementation, the controller is further configured to stop detecting the first switching module, the second switching module, the main switch, or the precharge switch in response to the power converter being in anti-reverse current mode.

[0011] In one possible implementation, the power converter further includes: a main switch; a first terminal of the main switch is used to connect to the DC source, and a second terminal of the main switch is connected to the positive terminal of the third terminal of the first switch module; The controller is further configured to, after the power converter stops, turn off the main switch, and after a second preset time, cause the switching transistor in the first bidirectional conversion circuit to operate at the first frequency and the switching transistor in the second bidirectional conversion circuit to operate at the second frequency; and, if the voltage of the intermediate bus of the first bidirectional conversion circuit and the voltage of the intermediate bus of the second bidirectional conversion circuit are both less than a fifth threshold, turn off the switching transistors of the primary circuits of the first bidirectional conversion circuit and the second bidirectional conversion circuit; and, if the voltage at the third terminal of the second switching module is less than the second threshold and the change in voltage at the third terminal of the second switching module is less than a sixth threshold within a preset number of preset periods, determine that the switching transistor of the power converter is abnormal. The second frequency is higher than the operating frequency of the switching transistor in the second dual active converter circuit after the power converter is started.

[0012] In a second aspect of this application, a control method for a power converter is provided. The power converter includes: a first bidirectional conversion circuit, a second bidirectional conversion circuit, a first switching module, and a second switching module. A first terminal of the first bidirectional conversion circuit is connected to a first terminal of the first switching module, a first terminal of the second bidirectional conversion circuit is connected to a second terminal of the first switching module, and a third terminal of the first switching module is used to connect to a DC source. A second terminal of the first bidirectional conversion circuit is connected to a first terminal of the second switching module, a second terminal of the second bidirectional conversion circuit is connected to a second terminal of the second switching module, and a third terminal of the second switching module is used to connect to a load. The control method includes: before the power converter is started, controlling the switching transistor in the first bidirectional conversion circuit to operate, so that power is reciprocated between the first terminal and the second terminal of the first bidirectional conversion circuit; controlling the switching transistor in the second bidirectional conversion circuit to operate, so that power is reciprocated between the first terminal and the second terminal of the second bidirectional conversion circuit, so as to discharge energy in the power converter; after the discharge is completed, in response to the voltage at the third terminal of the first switching module being greater than or equal to a first threshold, determining that the first switching module is abnormal or the switching transistor of the power converter is abnormal; or, in response to at least one of the voltage at the first terminal of the second switching module or the voltage at the second terminal of the second switching module being greater than or equal to a second threshold, determining that the second switching module is abnormal or the switching transistor of the power converter is abnormal.

[0013] In one possible implementation, the first bidirectional conversion circuit and the second bidirectional conversion circuit have the same structure; the first bidirectional conversion circuit includes a first DC circuit and a first dual active conversion circuit, the first DC circuit is connected to the first dual active conversion circuit through an intermediate bus, the primary side circuit of the first dual active conversion circuit includes a first bridge arm and a second bridge arm connected in parallel, and the secondary side circuit of the first dual active conversion circuit includes a third bridge arm and a fourth bridge arm connected in parallel. The control method specifically includes: sequentially turning on the first group of switches, the second group of switches, the third group of switches, and the fourth group of switches in the first dual active converter circuit at a first frequency; the first group of switches includes the upper switch of the first bridge arm and the lower switch of the second bridge arm, the second group of switches includes the upper switch of the third bridge arm and the lower switch of the fourth bridge arm, the third group of switches includes the lower switch of the first bridge arm and the upper switch of the second bridge arm, and the fourth group of switches includes the lower switch of the third bridge arm and the upper switch of the fourth bridge arm; The first frequency is higher than the operating frequency of the switching transistor in the first dual active converter circuit after the power converter is started.

[0014] In one possible implementation, the power converter further includes: a main switch and a pre-charge switch; a first terminal of the main switch is connected to the DC source, and a second terminal of the main switch is connected to the positive terminal of the third terminal of the first switch module; a first terminal of the pre-charge switch is connected to the first terminal of the main switch, and a second terminal of the pre-charge switch is connected to the second terminal of the main switch via a resistor; the first switch module includes a first series switch module and a first parallel switch module, the first series switch module includes a first switch, and the first parallel switch module includes a second switch and a third switch; the positive terminal of the first terminal of the first bidirectional conversion circuit is connected to the positive terminal of the first terminal of the second bidirectional conversion circuit via the second switch, the negative terminal of the first terminal of the first bidirectional conversion circuit is connected to the positive terminal of the first terminal of the second bidirectional conversion circuit via the first switch, and the negative terminal of the first terminal of the first bidirectional conversion circuit is connected to the negative terminal of the first terminal of the second bidirectional conversion circuit via the third switch; The control method further includes: in response to the voltage at the third terminal of the first switching module being less than a first threshold, and the first series switching module or the first parallel switching module being normal and the precharge switch being normal, sending a shutdown command to the main switch; controlling the switching transistor in the first bidirectional conversion circuit to operate at the first frequency, controlling the switching transistor in the second bidirectional conversion circuit to operate at the second frequency, and in response to the voltage at both ends of the main switch being less than or equal to a third threshold, determining that the main switch is abnormal; The second frequency is higher than the operating frequency of the switching transistor in the second dual active converter circuit after the power converter is started.

[0015] In one possible implementation, the power converter further includes: a main switch and a pre-charge switch; a first terminal of the main switch is connected to the DC source, and a second terminal of the main switch is connected to the positive terminal of the third terminal of the first switch module; a first terminal of the pre-charge switch is connected to the first terminal of the main switch, and a second terminal of the pre-charge switch is connected to the second terminal of the main switch via a resistor; the second switch module includes a fourth switch, a fifth switch, and a sixth switch, wherein the positive terminal of the second terminal of the first bidirectional conversion circuit is connected to the positive terminal of the second terminal of the second bidirectional conversion circuit via the fifth switch, the negative terminal of the second terminal of the first bidirectional conversion circuit is connected to the positive terminal of the second terminal of the second bidirectional conversion circuit via the fourth switch, and the negative terminal of the second terminal of the first bidirectional conversion circuit is connected to the negative terminal of the second terminal of the second bidirectional conversion circuit via the sixth switch; The control method further includes: in response to the voltage at the first terminal of the second switching module being less than a second threshold and the voltage at the second terminal of the second switching module being less than the second threshold, the precharge switch and the main switch being normal, and the fifth switch and the sixth switch being normally engaged, sending a shutdown command to the fifth switch and the sixth switch; causing the switching transistor in the first bidirectional conversion circuit to operate at the first frequency, causing the switching transistor in the second bidirectional conversion circuit to operate at the second frequency, and in response to the voltage at the third terminal of the second switching module being less than a fourth threshold, determining that at least one of the fifth switch or the sixth switch is abnormally shut down; the second frequency is higher than the operating frequency of the switching transistor in the second dual active conversion circuit after the power converter is started.

[0016] In one possible implementation, the control method further includes: In response to the fact that both the fifth and sixth switches are functioning normally, the fourth switch is engaged. When the fourth switch is engaged normally, a shutdown command is sent to the fourth switch; the switching transistor in the first bidirectional conversion circuit operates at the first frequency, and the switching transistor in the second bidirectional conversion circuit operates at the second frequency. In response to the voltage at the third terminal of the second switch module being less than the fourth threshold, the fourth switch is determined to be abnormal.

[0017] In one possible implementation, the power converter further includes: a main switch; a first terminal of the main switch is connected to the DC source, and a second terminal of the main switch is connected to the positive terminal of the third terminal of the first switching module; the control method further includes: after the power converter stops, turning off the main switch; after a second preset time, causing the switching transistor in the first bidirectional conversion circuit to operate at a first frequency, and causing the switching transistor in the second bidirectional conversion circuit to operate at a second frequency; in response to the voltage of the intermediate bus of the first bidirectional conversion circuit and the voltage of the intermediate bus of the second bidirectional conversion circuit being less than a fifth threshold, turning off the switching transistors of the primary circuits of the first bidirectional conversion circuit and the second bidirectional conversion circuit; and in response to the voltage of the third terminal of the second switching module being less than the second threshold, and the change in the voltage of the third terminal of the second switching module being less than a sixth threshold within a preset number of preset periods, determining that the switching transistor of the power converter is abnormal. The power converter provided in this application has a controller configured to control the operation of the switching transistors of a first bidirectional conversion circuit, causing power to reciprocate between the first and second terminals of the first bidirectional conversion circuit, and to control the operation of the switching transistors of a second bidirectional conversion circuit, causing power to reciprocate between the first and second terminals of the second bidirectional conversion circuit, thereby discharging residual energy in the power converter. Based on the port voltages of the first and second switching modules after discharging, the controller determines whether the first switching module, the second switching module, or the switching transistors of the power converter are malfunctioning. This solution eliminates the need for separate first and second terminal discharging branches for the power converter, thus reducing additional power devices. While reducing hardware complexity and cost, it provides a more stable voltage condition for detecting the switching state before power converter startup, extending the lifespan of the power converter. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a first type of power converter provided in an embodiment of this application; Figure 2 This is a schematic diagram of a second type of power converter provided in an embodiment of this application; Figure 3 A schematic diagram of a switching transistor operation timing provided for an embodiment of this application; Figure 4 A schematic diagram of a third type of power converter provided in the embodiments of this application; Figure 5 A schematic diagram of the detection logic of the first parallel switch module provided in an embodiment of this application; Figure 6 This is a schematic diagram of the detection logic of the first series switch module provided in an embodiment of this application; Figure 7 This is a schematic diagram of a fourth type of power converter provided in the embodiments of this application; Figure 8 This is a schematic diagram of the detection logic of the second switch module provided in an embodiment of this application; Figure 9 A schematic diagram of energy discharge logic after a power converter is shut down, provided in an embodiment of this application; Figure 10 This is a schematic diagram of a control method for a power converter provided in an embodiment of this application. Detailed Implementation

[0019] After a power converter shuts down, residual energy may remain in the DC bus capacitor, intermediate bus capacitor, output capacitor, and other energy storage components in the conversion circuit. If switch status detection is performed directly at this time, the residual voltage may prevent the voltage relationship across the switch from accurately reflecting the actual on / off state. Therefore, this application provides a power converter and control method that utilizes the switching transistors of the conversion circuit to perform narrow-pulse operation before the power converter starts up. This allows residual energy to be gradually consumed during the high-frequency switching process of the switching transistors through the conduction losses, switching losses, and equivalent impedance of the power devices, thereby reducing the voltage at relevant nodes. This solution eliminates the need for separate bleeder switches and bleeder resistors at the input and output terminals of the power converter, resulting in low hardware costs.

[0020] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the embodiments of this application will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0021] See Figure 1 The figure is a schematic diagram of the first power converter provided in the embodiment of this application.

[0022] The power converter provided in this application includes: a first bidirectional conversion circuit 100, a second bidirectional conversion circuit 200, a first switching module 300, a second switching module 400, and a controller 500.

[0023] The first end of the first bidirectional conversion circuit 100 is connected to the first end of the first switch module 300, the first end of the second bidirectional conversion circuit 200 is connected to the second end of the first switch module 300, and the third end of the first switch module 300 is used to connect to the DC source 600.

[0024] The second end of the first bidirectional conversion circuit 100 is connected to the first end of the second switch module 400, the second end of the second bidirectional conversion circuit 200 is connected to the second end of the second switch module 400, and the third end of the second switch module 400 is used to connect the load 700.

[0025] This application does not specifically limit the types of DC source 600 and load 700. In one possible implementation, DC source 600 can be the DC bus of an energy storage converter or a DC battery; load 700 can be a battery. When both DC source 600 and load 700 are batteries, the power converter can be used to achieve mutual charging of the two batteries. The first switching module 300 is used to switch the series or parallel connection between the first terminal of the first bidirectional conversion circuit 100 and the first terminal of the second bidirectional conversion circuit 200. The second switching module 400 is used to switch the series or parallel connection between the second terminal of the first bidirectional conversion circuit 100 and the second terminal of the second bidirectional conversion circuit 200. Thus, the power converter can flexibly switch the series and parallel connection of the first and second terminals, as well as combine different operating modes of the first and second terminals, according to the voltage requirements of the first and second terminals of the power converter.

[0026] The controller 500 is configured to control the operation of the switching transistors in the first bidirectional conversion circuit 100 before the power converter is started, so that power is reciprocated between the first terminal and the second terminal of the first bidirectional conversion circuit 100, and to control the operation of the switching transistors in the second bidirectional conversion circuit 200, so that power is reciprocated between the first terminal and the second terminal of the second bidirectional conversion circuit 200, so as to release the energy in the power converter.

[0027] Specifically, the controller 500 sends narrow pulse drive signals to the switching transistors in the first bidirectional conversion circuit 100 and the second bidirectional conversion circuit 200 to control the operation of the switching transistors in the first bidirectional conversion circuit 100 and the second bidirectional conversion circuit 200. The duty cycle of the narrow pulse drive signal is lower than the duty cycle of the drive signal for the switching transistors of the power converter during normal operation after the power converter is powered on.

[0028] The controller 500 controls the power transmission direction in the bidirectional converter circuit by controlling the conduction timing of the switching transistors; it also controls the power transmission magnitude by controlling the duty cycle of the drive signal. Taking the first bidirectional converter circuit 100 as an example, the controller 500 alternately sends narrow pulse drive signals to the switching transistors at the first and second ends of the first bidirectional converter circuit 100. When the switching transistor at the first end of the first bidirectional converter circuit 100 is activated, energy is transferred from the first end to the second end; when the switching transistor at the second end of the first bidirectional converter circuit 100 is activated, energy is transferred from the second end to the first end. Furthermore, the narrow pulse drive signal ensures higher switching losses when the switching transistors are activated. Thus, the energy in the first bidirectional converter circuit 100 is gradually dissipated during the reciprocating transmission process.

[0029] In one possible implementation, the controller 500 sends high-frequency narrow-pulse drive signals to the switching transistors in the first bidirectional converter circuit 100 and the second bidirectional converter circuit 200. For example, the frequency of the narrow-pulse drive signal can be 300kHz to 500kHz, allowing the first bidirectional converter circuit 100 and the second bidirectional converter circuit 200 to complete multiple energy transfers within a preset discharge time. The switch in the first switching module 300, based on the operating mode of the power converter before its last shutdown, keeps the first bidirectional converter circuit 100 and the second bidirectional converter circuit 200 in a series or parallel connection, thereby gradually decreasing the third terminal voltage of the first switching module 300, the first terminal voltage and the second terminal voltage of the second switching module 400, and the capacitor voltages in the first bidirectional converter circuit 100 and the second bidirectional converter circuit 200. Furthermore, because the controller 500 controls the operation of the switching transistors in the power converter using narrow-pulse drive signals with low duty cycles, the conduction time of each switching transistor is short, thereby limiting the energy and peak current transmitted during each switching transistor operation and reducing the thermal stress borne by the switching transistors.

[0030] After the energy discharge in the power converter is completed, the controller 500 can perform fault detection of the first switching module based on the port voltages of the first switching module 300 and the second switching module 400. If the voltage at the third terminal of the first switching module 300 is greater than or equal to the first threshold U1, it indicates that the input voltage has not been effectively discharged. At this time, the controller 500 determines that the first switching module 300 is abnormal or the switching transistor of the power converter is abnormal. For example, the switch in the first switching module 300 may not be effectively engaged, or the switching transistor of the power converter may not operate according to the drive signal sent by the controller 500.

[0031] Similarly, after the energy discharge in the power converter is completed, the controller 500 can indicate that the voltage at the second terminal of the first bidirectional conversion circuit 100 or the second bidirectional conversion circuit 200 has not been effectively discharged, based on at least one of the voltage at the first terminal or the voltage at the second terminal of the second switching module 400 being greater than or equal to the second threshold U2. At this time, the controller 500 determines that the second switching module 400 is malfunctioning or that the switching transistor of the power converter is malfunctioning. For example, the switch in the second switching module 400 may be stuck, or the switching transistor of the power converter may not operate according to the drive signal sent by the controller 500.

[0032] This application does not specifically limit the conditions under which the power converter completes energy discharge. For example, the controller 500 can determine that the power converter has completed energy discharge after the power converter has discharged energy for a preset time. The preset time can be 1.1s.

[0033] This application does not specifically limit the values ​​of the first threshold U1 and the second threshold U2. The first threshold U1 and the second threshold U2 can be set according to the safe switching voltage of the switching module, the withstand voltage of the devices in the power converter, the actual operating conditions of the power converter, and the allowable voltage error detected by the switching module. For example, if the withstand voltage of the capacitor in the power converter is 500V, the first threshold U1 can be 450V and the second threshold U2 can be 30V.

[0034] The power converter provided in this application embodiment has a controller configured to control the operation of the switching transistors of a first bidirectional conversion circuit, causing power to reciprocate between the first and second terminals of the first bidirectional conversion circuit. The controller also controls the switching transistors of a second bidirectional conversion circuit to operate at a second frequency, causing power to reciprocate between the first and second terminals of the second bidirectional conversion circuit, thereby discharging residual energy in the power converter. Based on the port voltages of the first and second switching modules after discharging, the controller determines whether the first switching module, the second switching module, or the switching transistors of the power converter are malfunctioning. This solution eliminates the need for separate first and second terminal discharging branches for the power converter, thus reducing additional power devices. While reducing hardware complexity and cost, it provides a more stable voltage condition for detecting the switching state before power converter startup, extending the power converter's lifespan.

[0035] This application does not specifically limit the structure of the first bidirectional conversion circuit 100 and the second bidirectional conversion circuit 200. Both the first bidirectional conversion circuit 100 and the second bidirectional conversion circuit 200 can be bidirectional DC / DC converters (BDC). For example, the first bidirectional conversion circuit 100 and the second bidirectional conversion circuit 200 may include isolated topologies such as CLLC, LLC, full-bridge, and dual active bridge (DAB) DC / DC converters. In one possible implementation, the power converter provided in this application has the same structure for the first bidirectional conversion circuit 100 and the second bidirectional conversion circuit 200.

[0036] See Figure 2 This figure is a schematic diagram of a second type of power converter provided in an embodiment of this application.

[0037] The following description uses the structure of the first bidirectional converter circuit 100 as an example. The first bidirectional converter circuit 100 includes a first DC circuit 110 and a first dual active converter circuit 120. The first DC circuit 110 is connected to the first dual active converter circuit 120 via an intermediate bus. An intermediate bus capacitor C1 is connected between the positive and negative terminals of the intermediate bus of the first bidirectional converter circuit 100. This application does not specifically limit the structure of the first DC circuit 110; the first DC circuit 110 may include a DC bus capacitor, a step-up / step-down circuit, etc. The second bidirectional converter circuit 200 may include a second DC circuit 210 and a second dual active converter circuit 220 connected via an intermediate bus. An intermediate bus capacitor C2 is connected between the positive and negative terminals of the intermediate bus of the second bidirectional converter circuit 200. The specific structure of the second bidirectional converter circuit 200 is the same as that of the first bidirectional converter circuit 100, and will not be repeated here.

[0038] The primary side circuit of the first dual active converter circuit 120 includes a first bridge arm and a second bridge arm connected in parallel, and the secondary side circuit includes a third bridge arm and a fourth bridge arm connected in parallel. Each of the first, second, third, and fourth bridge arms includes an upper transistor and a lower transistor connected in series. The first dual active converter circuit 120 includes an upper transistor Q1 and a lower transistor Q2 for the first bridge arm, an upper transistor Q3 and a lower transistor Q4 for the second bridge arm, an upper transistor Q5 and a lower transistor Q6 for the third bridge arm, and an upper transistor Q7 and a lower transistor Q8 for the fourth bridge arm. The first and second bridge arms form a primary-side full bridge, and the third and fourth bridge arms form a secondary-side full bridge. The primary-side and secondary-side full bridges are connected by a high-frequency transformer.

[0039] See Figure 3 This figure is a schematic diagram of a switching transistor operation timing provided in an embodiment of this application.

[0040] Figure 3 In the diagram, the horizontal axis t represents the timing sequence of switching transistors Q1 to Q8, and the vertical axis represents the control signals of each switching transistor.

[0041] The controller 500 sequentially turns on the first group of switches, the second group of switches, the third group of switches, and the fourth group of switches in the first dual active converter circuit 120 at a first frequency. The first group of switches includes the upper switch Q1 of the first bridge arm and the lower switch Q4 of the second bridge arm; the second group of switches includes the upper switch Q5 of the third bridge arm and the lower switch Q8 of the fourth bridge arm; the third group of switches includes the lower switch Q2 of the first bridge arm and the upper switch Q3 of the second bridge arm; and the fourth group of switches includes the lower switch Q6 of the third bridge arm and the upper switch Q7 of the fourth bridge arm.

[0042] When the first set of switches is turned on, the primary-side full-bridge applies a first primary-side voltage to the transformer. When the second set of switches is turned on, the secondary-side full-bridge forms a current path corresponding to the first primary-side voltage and applies a first secondary-side voltage to the transformer. When the third set of switches is turned on, the primary-side full-bridge forms a current path corresponding to the first secondary-side voltage and applies a second primary-side voltage to the transformer. When the fourth set of switches is turned on, the secondary-side full-bridge forms a current path corresponding to the second primary-side voltage and applies a second secondary-side voltage to the transformer. Subsequently, the first set of switches is turned on, the primary-side full-bridge forms a current path corresponding to the second secondary-side voltage, and continues to apply the first primary-side voltage to the transformer. In this way, the first to fourth sets of switches operate in a cycle, causing the energy stored in the intermediate bus capacitor C1 of the first bidirectional converter circuit 100, the capacitor connected to the first terminal of the first switching module 300, and the capacitor connected to the first terminal of the second switching module 400 to be alternately transferred between the primary and secondary sides of the first dual active converter circuit 120, and gradually consumed through the conduction loss, switching loss, and equivalent impedance of the power devices.

[0043] The second dual active converter circuit 220 can use the same switching transistor grouping and operating sequence as the first dual active converter circuit 120, and operate at the second frequency. Its working principle is the same as that of the first dual active converter circuit 120, and will not be described again here.

[0044] This application does not specifically limit the relationship between the first frequency and the second frequency; the first frequency and the second frequency may be equal or unequal. Those skilled in the art can set the first frequency and the second frequency based on the actual operating conditions of the power converter, the device parameters in the first bidirectional conversion circuit 100 and the second bidirectional conversion circuit 200, the voltage levels at the input and output terminals, and the allowable device stress. This application does not specifically limit the values ​​of the first frequency and the second frequency. To improve energy dissipation efficiency, a higher first frequency or second frequency can be set. The first frequency and the second frequency can be selected based on the magnitude of the energy to be dissipated. For example, when the energy to be dissipated is high, the first frequency and the second frequency can be set to 500kHz; when the energy to be dissipated is low, the first frequency and the second frequency can be adjusted to 300kHz.

[0045] This application does not specifically limit the specific time when the switching transistor in the first bidirectional conversion circuit 100 operates at the first frequency or the specific time when the switching transistor in the second bidirectional conversion circuit 200 operates at the second frequency. Those skilled in the art can also set it according to the actual operating conditions of the power converter.

[0046] The power converter provided in this application embodiment may include dual active converter circuits, with the first and second bidirectional conversion circuits comprising a first bidirectional conversion circuit and a second bidirectional conversion circuit. The controller is configured to sequentially turn on the diagonal switches of the primary and secondary circuits of the dual active converter circuits at high frequency for short periods, thereby enabling the establishment of a bidirectional energy transfer path using the existing power loops in the power converter without introducing an additional energy discharge circuit. This solution achieves energy discharge without adding independent discharge power devices, providing a prerequisite for the self-test of the switching module before the power converter starts up; and it can limit the current generated by a single discharge and the stress borne by the devices, ensuring device safety.

[0047] The self-test logic of the first and second switching modules of the power converter will be described in detail below with reference to the attached diagram.

[0048] In one possible implementation, the power converter provided in this application embodiment further includes: a main switch and a precharge switch.

[0049] See Figure 4 This figure is a schematic diagram of a third type of power converter provided in an embodiment of this application.

[0050] The first DC circuit 110 and the second DC circuit 210 can be Buck-Boost circuits. Figure 4 In this embodiment, the DC source 600 is the energy storage converter PCS, the load 700 is the battery ev, and the first DC circuit 110 and the second DC circuit 210 are both interleaved Buck-Boost circuits.

[0051] Figure 4 In this embodiment, the first terminal of the main switch K0 is connected to the DC source 600, and the second terminal of the main switch K0 is connected to the positive terminal of the third terminal of the first switch module 300. The first terminal of the precharge switch Kp is connected to the first terminal of the main switch K0, and the second terminal of the precharge switch Kp is connected to the second terminal of the main switch K0 through the precharge resistor Rp.

[0052] The first switch module 300 includes a first series switch module and a first parallel switch module. The first series switch module includes a first switch K1, and the first parallel switch module includes a second switch K2 and a third switch K3. The positive terminal of the first end of the first bidirectional conversion circuit 100 is connected to the positive terminal of the first end of the second bidirectional conversion circuit 200 through the second switch K2; the negative terminal of the first end of the first bidirectional conversion circuit 100 is connected to the positive terminal of the first end of the second bidirectional conversion circuit 200 through the first switch K1; and the negative terminal of the first end of the first bidirectional conversion circuit 100 is connected to the negative terminal of the first end of the second bidirectional conversion circuit 200 through the third switch K3.

[0053] When the second switch K2 and the third switch K3 are engaged and the first switch K1 is disengaged, the input terminal of the first bidirectional converter circuit 100 is connected in parallel with the input terminal of the second bidirectional converter circuit 200. When the first switch K1 is engaged and the second switch K2 and the third switch K3 are disengaged, the input terminal of the first bidirectional converter circuit 100 is connected in series with the input terminal of the second bidirectional converter circuit 200.

[0054] The controller 500 is also configured to send a shutdown command to the main switch K0 in response to the voltage at the third terminal of the first switch module 300 being less than the first threshold U1, and the first series switch module or the first parallel switch module being normal and the precharge switch Kp being normal; control the switch in the first bidirectional conversion circuit 100 to operate at the first frequency, control the switch in the second bidirectional conversion circuit 200 to operate at the second frequency, and determine that the main switch K0 is abnormal in response to the voltage at both ends of the main switch K0 being less than or equal to the third threshold U3.

[0055] The embodiments of this application do not specifically limit the value of the third threshold U3. The third threshold U3 can be selected according to the parameters of the main switch K0 itself. For example, the third threshold U3 can be 15V.

[0056] The detection logic of the controller 500 for the first switch module 300, the main switch K0, and the precharge switch Kp is explained below with reference to the accompanying drawings. The detection of the first parallel switch module will be used as an example for explanation.

[0057] See Figure 5 The figure is a schematic diagram of the detection logic of the first parallel switch module provided in the embodiment of this application.

[0058] When the power converter stops, the controller 500 controls the power converter to block the waveform and sends shutdown commands to the main switch K0, precharge switch Kp, first switch K1, second switch K2, and third switch K3. At the start of the self-test of the first switching module 300 of the power converter, the controller 500 controls the switching transistors of the first bidirectional conversion circuit 100 and the second bidirectional conversion circuit 200 to operate at a first frequency, thereby discharging the residual voltage at the input terminal and intermediate bus of the power converter. For example, the controller 500 can collect the voltage at each port of the first switching module 300 after a first preset time has elapsed since the switching transistors of the first bidirectional conversion circuit 100 and the second bidirectional conversion circuit 200 operate, and determine whether the initial discharge is complete based on the voltage at each port. If the voltage Vin at the third terminal of the first switching module 300 is greater than or equal to the first threshold U1, it indicates that the input voltage has not been effectively discharged. At this time, the controller 500 determines that the first switching module 300 is abnormal or the switching transistor of the power converter is abnormal. For example, the switch in the first switching module 300 may not be effectively engaged, or the switching transistor of the power converter may not operate according to the drive signal sent by the controller 500.

[0059] The embodiments of this application do not specifically limit the value of the first preset time. For example, the first preset time can be 1.1s.

[0060] The controller 500 is also configured to detect the activation of the input switches when the first switch module is normally turned off. The activation detection of the first parallel switch module will be used as an example below.

[0061] In the activation detection of the first parallel switch module, the controller 500 sends activation commands to the second switch K2 and the third switch K3, and acquires the input voltages of the first bidirectional conversion circuit 100 and the second bidirectional conversion circuit 200. Since the first bidirectional conversion circuit 100 and the second bidirectional conversion circuit 200 are connected in parallel when the second switch K2 and the third switch K3 are normally activated, the input voltage V1 of the first bidirectional conversion circuit 100 is approximately equal to the input voltage V2 of the second bidirectional conversion circuit 200, and the input voltages of both conversion circuits are approximately equal to the third terminal voltage Vin of the first switch module 300. When the main switch K0 and the precharge switch Kp are off, the voltage difference across the main switch K0 should be greater than the fourth threshold U4, that is, the voltage difference between the DC source 600 voltage Vout and the third terminal voltage Vin of the first switch module 300 should be greater than the fourth threshold U4. Therefore, the controller 500 can determine that the main switch K0 and the precharge switch Kp are normally turned off, and the first parallel switch module is normally engaged, based on the following: the voltage difference across the main switch K0 is greater than the fourth threshold U4; the voltage difference between the input voltage V1 of the first bidirectional conversion circuit 100 and the third terminal voltage Vin of the first switch module 300 is less than the fourth threshold U4; and the voltage difference between the input voltage V2 of the second bidirectional conversion circuit 200 and the third terminal voltage Vin of the first switch module 300 is less than the fourth threshold U4. Otherwise, the controller 500 determines that at least one of the main switch K0, the precharge switch Kp, and the first parallel switch module is abnormal.

[0062] In response to the normal shutdown of the main switch K0 and the precharge switch Kp, and the normal engagement of the first parallel switch module, the controller 500 performs an engagement detection of the precharge switch Kp. During the precharge switch Kp detection, the controller 500 sends an engagement command to the precharge switch Kp, and the DC source 600 charges the energy storage elements on the input side of the first bidirectional converter circuit 100 and the second bidirectional converter circuit 200 through the precharge resistor Rp. If the precharge switch Kp and the precharge circuit are normal, the third terminal voltage Vin of the first switch module 300 will rise to the seventh threshold U7 within a preset time, and the third terminal voltage Vin of the first switch module 300 will be transmitted to the input terminals of the first bidirectional converter circuit 100 and the second bidirectional converter circuit 200. Therefore, after a preset time, the controller 500 can determine that the precharge switch Kp is engaged normally and the precharge circuit is normal based on the following: the voltage Vin at the third terminal of the first switch module 300 is greater than the seventh threshold U7; the voltage difference between the voltage Vout of the DC source 600 and the voltage Vin at the third terminal of the first switch module 300 is less than the eighth threshold U8; the voltage difference between the voltage Vin at the third terminal of the first switch module 300 and the input voltage V1 of the first bidirectional converter circuit 100 is less than the eighth threshold U8; and the voltage difference between the voltage Vin at the third terminal of the first switch module 300 and the input voltage V2 of the second bidirectional converter circuit 200 is less than the eighth threshold U8. Otherwise, the controller 500 determines that there is an abnormality in the precharge switch Kp or the precharge circuit.

[0063] The embodiments of this application do not specifically limit the value of the seventh threshold U7. The seventh threshold U7 can be selected according to the actual operating conditions of the power converter. For example, when the minimum operating voltage of the power converter is 100V, the seventh threshold U7 can be 60V.

[0064] In response to the normal operation of the precharge switch Kp and the precharge circuit, the controller 500 sends a closing command to the main switch K0. After the main switch K0 closes normally, the voltage difference across the main switch K0 should be less than the eighth threshold U8. Therefore, the controller determines that the main switch K0 is closing normally based on the fact that the voltage difference across the main switch K0 is less than the eighth threshold U8, i.e., the voltage difference between the DC source 600 voltage Vout and the third terminal voltage Vin of the first switch module 300 is less than the eighth threshold U8. Otherwise, the controller 500 determines that the main switch K0 is abnormal.

[0065] The embodiments of this application do not specifically limit the values ​​of the third threshold U3, the fourth threshold U4, and the eighth threshold U8. The third threshold U3, the fourth threshold U4, and the eighth threshold U8 can be selected according to the conduction parameters, turn-off parameters, etc. of each switch. For example, the third threshold U3 can be 15V, the fourth threshold U4 can be 5V, and the eighth threshold U8 can be 10V.

[0066] In response to the normal engagement of the main switch K0, the controller 500 sends a turn-off command to the main switch K0, controlling the switching transistors in the first bidirectional conversion circuit 100 to operate at a first frequency and the switching transistors in the second bidirectional conversion circuit 200 to operate at a second frequency, thereby changing the third terminal voltage Vin of the first switching module 300. If the voltage difference across the main switch K0 is less than or equal to the third threshold U3, it indicates that the main switch K0 has not turned off normally, and the main switch K0 is determined to be abnormal. If the voltage difference across the main switch K0 is greater than the third threshold U3, it indicates that the main switch K0 turns off normally.

[0067] The detection logic of the first series switch module in the first switch module 300 is described below with reference to the accompanying drawings.

[0068] See Figure 6 The figure is a schematic diagram of the detection logic of the first series switch module provided in the embodiment of this application.

[0069] and Figure 5 The difference in the embodiments is that, Figure 6 In the embodiment, during the activation detection of the first series-connected switch module, the controller 500 sends an activation command to the first switch K1 and acquires the input voltages of the first bidirectional converter circuit 100 and the second bidirectional converter circuit 200. Since the first bidirectional converter circuit 100 and the second bidirectional converter circuit 200 are connected in series when the first switch K1 is normally activated, the sum of the input voltages V1 and V2 of the first bidirectional converter circuit 100 and the second bidirectional converter circuit 200 is approximately equal to the third terminal voltage Vin of the first switch module 300. When the main switch K0 and the precharge switch Kp are off, the voltage difference across the main switch K0 should be greater than the fourth threshold U4, that is, the voltage difference between the DC source 600 voltage Vout and the third terminal voltage Vin of the first switch module 300 should be greater than the fourth threshold U4. Therefore, the controller 500 can determine that the main switch K0 and the precharge switch Kp are normally turned off, and that the first series switch module is normally engaged, based on the following: the voltage difference across the main switch K0 is greater than the fourth threshold, and the voltage difference between the sum of the third terminal voltage Vin of the first switch module 300 and the input terminal voltage V1 of the first bidirectional conversion circuit 100 and the input terminal voltage V2 of the second bidirectional conversion circuit 200 is less than the fourth threshold. Otherwise, the controller 500 determines that at least one of the main switch K0, the precharge switch Kp, and the first series switch module is abnormal.

[0070] After confirming that the main switch K0, precharge switch Kp, and the first series switch module are engaged normally... Figure 6 The subsequent detection logic in the embodiments is all the same as Figure 5 The implementation methods are the same and will not be repeated here.

[0071] The power converter provided in this application embodiment has a controller configured to control the operation of the switching transistors in the first and second bidirectional conversion circuits to discharge residual energy in the power converter. This provides a basis for the detection of the first switching module, the main switch, and the pre-charge switch, thereby improving the accuracy and reliability of switching fault detection in the power converter. This solution eliminates the need for additional detection and discharge circuits, reducing hardware costs and preventing the power converter from operating with faults due to abnormalities in the first switching module, the main switch, or the pre-charge switch, thus improving the operational safety of the power converter.

[0072] In one possible implementation, the power converter provided in this application embodiment includes a second switching module comprising a fourth switch, a fifth switch, and a sixth switch.

[0073] See Figure 7 This figure is a schematic diagram of the fourth type of power converter provided in the embodiments of this application.

[0074] Figure 7 In this embodiment, the positive terminal of the second end of the first bidirectional conversion circuit 100 is connected to the positive terminal of the second end of the second bidirectional conversion circuit 200 via the fifth switch K5; the negative terminal of the second end of the first bidirectional conversion circuit 100 is connected to the positive terminal of the second end of the second bidirectional conversion circuit 200 via the fourth switch K4; and the negative terminal of the second end of the first bidirectional conversion circuit 100 is connected to the negative terminal of the second end of the second bidirectional conversion circuit 200 via the sixth switch K6.

[0075] When the fifth switch K5 and the sixth switch K6 are engaged and the fourth switch K4 is disengaged, the outputs of the first bidirectional conversion circuit 100 and the second bidirectional conversion circuit 200 are connected in parallel. When the fourth switch K4 is engaged and the fifth switch K5 and the sixth switch K6 are disengaged, the outputs of the first bidirectional conversion circuit 100 and the second bidirectional conversion circuit 200 are connected in series.

[0076] The controller 500 is also configured to send a shutdown command to the fifth switch K5 and the sixth switch K6 in response to the voltage Vdab1 at the first terminal of the second switch module 400 being less than a second threshold, the voltage Vdab2 at the second terminal of the second switch module 400 being less than the second threshold, the precharge switch Kp and the main switch K0 being normal, and the fifth switch K5 and the sixth switch K6 being normally engaged; to cause the switching transistor in the first bidirectional conversion circuit 100 to operate at a first frequency, and to cause the switching transistor in the second bidirectional conversion circuit 200 to operate at a second frequency; and to determine that at least one of the fifth switch K5 or the sixth switch K6 is abnormally shut down in response to the voltage Vev at the third terminal of the second switch module 400 being less than a fourth threshold U4.

[0077] The detection logic of the controller 500 for the second switch module 400 is described below with reference to the attached diagram.

[0078] See Figure 8 The figure is a schematic diagram of the detection logic of the second switch module provided in an embodiment of this application.

[0079] When the power converter shuts down, the controller 500 controls the power converter to block the waveform and sends shutdown commands to the main switch K0, precharge switch Kp, fourth switch K4, fifth switch K5, and sixth switch K6. At the start of the self-test of the second switching module 400 of the power converter, the controller 500 controls the switching transistors of the first bidirectional conversion circuit 100 and the second bidirectional conversion circuit 200 to operate at the first frequency to discharge residual voltage at the output terminal and intermediate bus of the power converter. If the relevant voltage does not drop to a safe range within a third preset time, for example, if at least one of the voltages Vdab1 at the first terminal or Vdab2 at the second terminal of the second switching module 400 is greater than or equal to the second threshold U2, it indicates that the output voltage of either the first bidirectional conversion circuit 100 or the second bidirectional conversion circuit 200 has not been effectively discharged. At this time, the controller 500 determines that at least one of the fourth switch K4, fifth switch K5, and sixth switch K6 is abnormal, or that the switching transistors of the power converter are abnormal. The embodiments of this application do not specifically limit the value of the third preset time. For example, the third preset time can be 1 second.

[0080] The controller 500 is also configured to send a pull-in command to the precharge switch Kp in response to the voltage Vdab1 at the first terminal of the second switch module 400 and the voltage Vdab2 at the second terminal of the second switch module 400 both being less than a second threshold U2. If the voltage difference between the voltage Vout of the DC source 600 and the voltage Vin at the third terminal of the first switch module 300 is less than a fourth threshold U4, the precharge switch Kp is determined to be normal. Conversely, if the voltage difference is less than a fourth threshold U4, the precharge switch Kp is determined to be abnormal.

[0081] In response to the precharge switch Kp operating normally, the controller 500 sends a turn-off command to the precharge switch Kp and a pull-in command to the main switch K0, causing the first bidirectional conversion circuit 100 and the second bidirectional conversion circuit 200 to operate according to the normal modulation mode. The controller 500 collects the intermediate bus voltages of the first bidirectional conversion circuit 100 and the second bidirectional conversion circuit 200. If the intermediate bus voltage Vmid1 of the first bidirectional conversion circuit 100 is greater than the ninth threshold U9, and the intermediate bus voltage Vmid2 of the second bidirectional conversion circuit 200 is greater than the ninth threshold U9, it means that both the first bidirectional conversion circuit 100 and the second bidirectional conversion circuit 200 can establish the expected operating voltage, and the controller 500 determines that the main switch K0 is normal. Conversely, if the intermediate bus voltage Vmid1 of the first bidirectional conversion circuit 100 is less than or equal to the ninth threshold U9, or the intermediate bus voltage Vmid2 of the second bidirectional conversion circuit 200 is less than or equal to the ninth threshold U9, the controller 500 determines that the main switch K0 is abnormal.

[0082] The embodiments of this application do not specifically limit the value of the ninth threshold U9. The ninth threshold U9 can be selected according to the operating conditions of the power converter. For example, when the lowest input voltage of the power converter is 100V, the ninth threshold U9 can be 100V.

[0083] After confirming that both the precharge switch Kp and the main switch K0 are functioning correctly, the controller 500 performs a test on the second switch module 400. In one possible implementation, the controller 500 is configured to first test the second parallel switch module, and then test the second series switch module; that is, to first test the fifth switch K5 and the sixth switch K6, and then test the fourth switch K4.

[0084] The controller 500 sends activation commands to the fifth switch K5 and the sixth switch K6, and controls the first bidirectional conversion circuit 100 and the second bidirectional conversion circuit 200 to operate according to the modulation mode during normal operation of the power converter to establish the output voltage. Since the first bidirectional conversion circuit 100 and the second bidirectional conversion circuit 200 are connected in parallel when the fifth switch K5 and the sixth switch K6 are normally activated, the output voltage Vdab1 of the first bidirectional conversion circuit 100 is approximately equal to the output voltage Vdab2 of the second bidirectional conversion circuit 200, and the output voltages of both circuits are approximately equal to the third terminal voltage Vev of the second switch module 400. Therefore, the controller 500 can determine that the fifth switch K5 and the sixth switch K6 are normally activated based on the fact that the output voltages Vdab1 of the first bidirectional conversion circuit 100, Vdab2 of the second bidirectional conversion circuit 200, and Vev of the second switch module 400 are all greater than the third threshold U3. Otherwise, the controller 500 determines that either the fifth switch K5 or the sixth switch K6 is abnormal.

[0085] In one possible implementation, in response to the normal engagement of the fifth switch K5 and the sixth switch K6, the controller 500 sends a turn-off command to the fifth switch K5 and the sixth switch K6, and causes the switching transistors in the first bidirectional converter circuit 100 to operate at a first frequency and the switching transistors in the second bidirectional converter circuit 200 to operate at a second frequency, in order to discharge the voltage established by the power converter during the engagement of the fifth switch K5 and the sixth switch K6. Since the discharge circuit is broken after both the fifth switch K5 and the sixth switch K6 are turned off, the controller 500 determines that at least one of the fifth switch K5 or the sixth switch K6 is abnormally turned off based on the fact that the voltage Vev at the third terminal of the second switch module 400 is less than the fourth threshold U4.

[0086] In response to the normal operation of both the fifth switch K5 and the sixth switch K6, the controller 500 engages the fourth switch K4. Since the output terminals of the first bidirectional converter circuit 100 and the second bidirectional converter circuit 200 are connected in series when the fourth switch K4 is engaged normally, the sum of the output voltages Vdab1 and Vdab2 of the first bidirectional converter circuit 100 and the second bidirectional converter circuit 200 is approximately equal to the voltage Vev at the third terminal of the second switch module 400. Therefore, the controller 500 can determine that the fourth switch K4 is engaged normally based on the fact that both the output voltages Vdab1 and Vdab2 of the first bidirectional converter circuit 100 and the second bidirectional converter circuit 200 are greater than the third threshold U3, and the voltage Vev at the third terminal of the second switch module 400 is greater than the sum of the output voltages Vdab1 and Vdab2 of the first bidirectional converter circuit 100 and the second bidirectional converter circuit 200. Otherwise, the controller 500 determines that the output voltage of the power converter has failed to establish properly.

[0087] In one possible implementation, in response to the normal engagement of the fourth switch K4, the controller 500 sends a turn-off command to the fourth switch K4, causing the switching transistor in the first bidirectional converter circuit 100 to operate at a first frequency and the switching transistor in the second bidirectional converter circuit 200 to operate at a second frequency. Since the discharge circuit is disconnected after the fourth switch K4 is turned off, the controller 500 determines that the fourth switch K4 is abnormal based on the voltage Vev at the third terminal of the second switch module 400 being less than the fourth threshold U4. Otherwise, it determines that the fourth switch K4 is turned off normally and ends the self-test of the second switch module 400.

[0088] In one possible implementation, the controller 500 is further configured to restore the normal modulation parameters of the first bidirectional converter circuit 100 and the second bidirectional converter circuit 200 after completing various detections on the input and output sides, and to activate the corresponding input and output switches according to the target operating mode of the power converter, so that the power converter enters the normal operating state.

[0089] The power converter provided in this application embodiment has a controller configured to control the operation of the switching transistors in the first and second bidirectional conversion circuits to discharge residual energy in the power converter. This provides a basis for the detection of the second switching module, the main switch, and the pre-charge switch, thereby improving the accuracy and reliability of switching fault detection in the power converter. This solution eliminates the need for additional detection and discharge circuits, reducing hardware costs and preventing the power converter from operating with faults due to abnormalities in the second switching module, the main switch, or the pre-charge switch, thus improving the operational safety of the power converter.

[0090] In one possible implementation, the controller 500 is also configured to stop detecting the first switching module 300, the second switching module 400, the main switch K0, or the precharge switch Kp in response to the power converter being in anti-reverse current mode.

[0091] Specifically, when the power converter is in anti-reverse current mode, it indicates that the power converter has completed the self-test of the switching module. Therefore, after recognizing the anti-reverse current mode, the controller 500 skips the corresponding self-test steps, which can improve the startup efficiency of the power converter.

[0092] In one possible implementation, the controller 500 is further configured to, after the power converter stops, turn off the main switch K0, and after a second preset time, cause the switching transistors in the first bidirectional converter circuit 100 to operate at a first frequency and the switching transistors in the second bidirectional converter circuit 200 to operate at a second frequency. In response to the intermediate bus voltage Vmid1 of the first bidirectional converter circuit 100 and the intermediate bus voltage Vmid2 of the second bidirectional converter circuit 200 both being less than a fifth threshold U5, the controller turns off the switching transistors of the primary circuits of the first bidirectional converter circuit 100 and the second bidirectional converter circuit 200. In response to the voltage Vev at the third terminal of the second switching module 400 being less than a second threshold U2 and the change in voltage at the third terminal of the second switching module 400 being less than a sixth threshold U6 within a preset number of preset periods, the controller determines that the switching transistor is abnormal.

[0093] See Figure 9 The figure is a schematic diagram of the energy discharge logic after a power converter is shut down, provided in an embodiment of this application.

[0094] Specifically, after the power converter stops for a second preset time, the controller 500 causes the switching transistors in the first bidirectional conversion circuit 100 to operate at a first frequency and the switching transistors in the second bidirectional conversion circuit 200 to operate at a second frequency, in order to release residual energy in the power converter. The second preset time is used to wait for the main switch K0, the precharge switch Kp, and the switches in the first switch module 300 and the second switch module 400 to complete mechanical disconnection or electrical shutdown. This embodiment does not specifically limit the value of the second preset time; it can be set according to the switch operation time and the control loop response time. For example, the second preset time can be 60ms.

[0095] After completing the energy discharge waveform configuration, the controller 500 can wait for a mode switching time and record the voltage Vev at the third terminal of the second switch module 400 as a reference for subsequent voltage change judgment. For example, the mode switching time can be 40ms.

[0096] When the intermediate bus voltage Vmid1 of the first bidirectional converter circuit 100 and the intermediate bus voltage Vmid2 of the second bidirectional converter circuit 200 are both less than the fifth threshold U5, it indicates that the primary-side energy storage of the first bidirectional converter circuit 100 and the primary-side energy storage of the second bidirectional converter circuit 200 have both decreased to the preset range. At this time, the controller 500 turns off the switching transistors of the primary-side circuits of the first bidirectional converter circuit 100 and the second bidirectional converter circuit 200, and only allows the secondary-side switching transistors to continue operating, so as to continue to reduce the voltage Vev at the third terminal of the second switching module 400.

[0097] This application does not specifically limit the value of the fifth threshold U5, and it can be set according to the withstand voltage of the intermediate bus capacitor, the withstand voltage of the power devices, and the subsequent discharge strategy. For example, the fifth threshold U5 can be 485V.

[0098] The controller 500 periodically samples the voltage at the third terminal of the second switching module 400 and calculates the voltage change between adjacent preset periods. If the voltage VeV at the third terminal of the second switching module 400 is less than the second threshold U2, and the voltage change at the third terminal of the second switching module 400 is less than the sixth threshold U6 within a preset number of preset periods, it indicates that the voltage VeV at the third terminal of the second switching module 400 has entered a lower voltage range. However, due to faults such as the switching transistor not operating according to control commands, the voltage VeV at the third terminal of the second switching module 400 tends to stabilize within several consecutive sampling periods, failing to achieve the expected voltage decrease. At this time, the controller 500 determines that the switching transistor is abnormal to reduce the risk of damage to various components in the power converter due to energy accumulation.

[0099] This application does not specifically limit the values ​​of the sixth threshold U6, the preset number of times, and the preset period. Those skilled in the art can set these values ​​based on the voltage sampling resolution, the normal discharge curve, the output capacitor capacity, and the allowable discharge time. For example, the sixth threshold U6 can be 6V, the preset period can be 100ms, and the preset number of times can be 20.

[0100] The power converter provided in this application, after the power converter stops and the switch is opened, controls the switching transistors of the primary and secondary circuits of the conversion circuit to generate waves for energy discharge. When the intermediate bus voltage of the conversion circuit drops below the fifth threshold, the operation of the primary circuit's switching transistors stops, and the secondary circuit's switching transistors continue to reduce the output voltage. The completion of discharge is determined by periodically observing changes in the output voltage. If the voltage drop rate is too slow, the discharge configuration will automatically restart and the detection process will be re-executed, forming a closed-loop control that enhances robustness and reliability. This scheme can adjust the switching transistors involved in the operation according to the voltage state of different nodes and identify switching transistor abnormalities through changes in output voltage.

[0101] In one possible implementation, after the power converter enters normal operation, the controller 500 restores the normal modulation mode of the first bidirectional conversion circuit 100 and the second bidirectional conversion circuit 200, so that the power converter performs energy conversion according to the target voltage, target current or target power.

[0102] The power converter provided in this application can be applied not only to DC photovoltaic energy storage and charging projects, but also to energy storage converters, DC charging piles, industrial power systems, etc., and has good versatility and scalability.

[0103] Based on the power converters provided in the above embodiments, this application also provides a control method for the power converter. The control method for the power converter provided in this application is applicable to any of the above-described power converters. The power converter includes: a first bidirectional conversion circuit, a second bidirectional conversion circuit, a first switching module, and a second switching module; the input terminal of the first bidirectional conversion circuit is connected to the first terminal of the first switching module, the input terminal of the second bidirectional conversion circuit is connected to the second terminal of the first switching module, and the third terminal of the first switching module is used to connect to a DC source; the output terminal of the first bidirectional conversion circuit is connected to the first terminal of the second switching module, the output terminal of the second bidirectional conversion circuit is connected to the second terminal of the second switching module, and the third terminal of the second switching module is used to connect to a load.

[0104] See Figure 10 The figure is a schematic diagram of a power converter control method provided in an embodiment of this application.

[0105] Control methods include: S1: Before the power converter is started, the switching transistor in the first bidirectional conversion circuit is controlled to operate, so that power is transferred back and forth between the first terminal and the second terminal of the first bidirectional conversion circuit. The switching transistor in the second bidirectional conversion circuit is controlled to operate, so that power is transferred back and forth between the first terminal and the second terminal of the second bidirectional conversion circuit, so as to discharge the energy in the power converter. After the discharge is completed, in response to the voltage at the third terminal of the first switching module being greater than or equal to the first threshold, it is determined that the first switching module is abnormal or the switching transistor of the power converter is abnormal.

[0106] S2: Before the power converter is started, the switching transistor in the first bidirectional conversion circuit is controlled to operate, so that power is transferred back and forth between the first terminal and the second terminal of the first bidirectional conversion circuit. The switching transistor in the second bidirectional conversion circuit is controlled to operate, so that power is transferred back and forth between the first terminal and the second terminal of the second bidirectional conversion circuit, so as to discharge the energy in the power converter. After the discharge is completed, in response to at least one of the voltage at the first terminal of the second switching module or the voltage at the second terminal of the second switching module being greater than or equal to the second threshold, it is determined that the second switching module is abnormal or the switching transistor of the power converter is abnormal.

[0107] The power converter control method provided in this application embodiment controls the operation of the switching transistors of the first bidirectional conversion circuit to allow power to reciprocate between the first and second terminals of the first bidirectional conversion circuit, and controls the operation of the switching transistors of the second bidirectional conversion circuit to allow power to reciprocate between the first and second terminals of the second bidirectional conversion circuit, thereby discharging residual energy in the power converter. Based on the port voltages of the first and second switching modules after discharging, it is determined whether the first switching module, the second switching module, or the switching transistors of the power converter are abnormal. This solution eliminates the need for separate first and second terminal discharging branches for the power converter, providing a relatively stable voltage condition for detecting the switching state before power converter startup while reducing hardware complexity and cost.

[0108] In one possible implementation, the power converter provided in this application embodiment has the same structure for the first bidirectional conversion circuit and the second bidirectional conversion circuit; the first bidirectional conversion circuit includes a first DC circuit and a first dual active conversion circuit, the first DC circuit is connected to the first dual active conversion circuit through an intermediate bus, the primary side of the first dual active conversion circuit includes a first bridge arm and a second bridge arm connected in parallel, and the secondary side of the first dual active conversion circuit includes a third bridge arm and a fourth bridge arm connected in parallel.

[0109] The control method specifically includes: being configured to sequentially turn on the first group of switching transistors, the second group of switching transistors, the third group of switching transistors, and the fourth group of switching transistors in the first dual active converter circuit at a first frequency; the first group of switching transistors includes the upper transistor of the first bridge arm and the lower transistor of the second bridge arm, the second group of switching transistors includes the upper transistor of the third bridge arm and the lower transistor of the fourth bridge arm, the third group of switching transistors includes the lower transistor of the first bridge arm and the upper transistor of the second bridge arm, and the fourth group of switching transistors includes the lower transistor of the third bridge arm and the upper transistor of the fourth bridge arm; The first frequency is higher than the operating frequency of the switching transistor in the first dual active converter circuit after the power converter is started.

[0110] The power converter control method provided in this application embodiment includes a first bidirectional conversion circuit and a second bidirectional conversion circuit, both of which may include dual active conversion circuits. By controlling the diagonal switches on the primary and secondary sides of the dual active conversion circuits to sequentially conduct at high frequencies for short periods, a bidirectional energy transfer path can be established using the existing power loops in the power converter without introducing an additional energy discharge circuit. This solution can achieve energy discharge without adding independent discharge power devices, providing a prerequisite for the self-test of the switching module before the power converter starts up; and it can limit the current generated by a single discharge and the stress on the devices, ensuring device safety and extending the life of the power converter.

[0111] In one possible implementation, the power converter further includes: a main switch and a pre-charge switch; a first terminal of the main switch is connected to a DC source, and a second terminal of the main switch is connected to the positive terminal of the third terminal of the first switch module; a first terminal of the pre-charge switch is connected to the first terminal of the main switch, and a second terminal of the pre-charge switch is connected to the second terminal of the main switch via a resistor; the first switch module includes a first series switch module and a first parallel switch module, the first series switch module includes a first switch, and the first parallel switch module includes a second switch and a third switch; the positive terminal of the first terminal of the first bidirectional conversion circuit is connected to the positive terminal of the first terminal of the second bidirectional conversion circuit via the second switch, the negative terminal of the first terminal of the first bidirectional conversion circuit is connected to the positive terminal of the first terminal of the second bidirectional conversion circuit via the first switch, and the negative terminal of the first terminal of the first bidirectional conversion circuit is connected to the negative terminal of the first terminal of the second bidirectional conversion circuit via the third switch; The control method further includes: in response to the voltage at the third terminal of the first switching module being less than a first threshold, and the first series switching module or the first parallel switching module being normal and the precharge switch being normal, sending a shutdown command to the main switch; controlling the switching transistor in the first bidirectional conversion circuit to operate at a first frequency, controlling the switching transistor in the second bidirectional conversion circuit to operate at a second frequency, and in response to the voltage at both ends of the main switch being less than or equal to a third threshold, determining that the main switch is abnormal. The second frequency is higher than the operating frequency of the switching transistor in the second dual active converter circuit after the power converter is started.

[0112] In one possible implementation, the power converter further includes: a main switch and a pre-charge switch; a first terminal of the main switch is connected to a DC source, and a second terminal of the main switch is connected to the positive terminal of the third terminal of the first switching module; a first terminal of the pre-charge switch is connected to the first terminal of the main switch, and a second terminal of the pre-charge switch is connected to the second terminal of the main switch via a resistor; the second switching module includes a fourth switch, a fifth switch, and a sixth switch, wherein the positive terminal of the second terminal of the first bidirectional conversion circuit is connected to the positive terminal of the second terminal of the second bidirectional conversion circuit via the fifth switch, the negative terminal of the second terminal of the first bidirectional conversion circuit is connected to the positive terminal of the second terminal of the second bidirectional conversion circuit via the fourth switch, and the negative terminal of the second terminal of the first bidirectional conversion circuit is connected to the negative terminal of the second terminal of the second bidirectional conversion circuit via the sixth switch; The control method further includes: in response to the voltage at the first terminal of the second switching module being less than a second threshold and the voltage at the second terminal of the second switching module being less than the second threshold, the precharge switch and the main switch being normal, and the fifth switch and the sixth switch being normally engaged, sending a turn-off command to the fifth switch and the sixth switch; causing the switching transistor in the first bidirectional conversion circuit to operate at a first frequency, causing the switching transistor in the second bidirectional conversion circuit to operate at a second frequency, and in response to the voltage at the third terminal of the second switching module being less than a fourth threshold, determining that at least one of the fifth switch or the sixth switch is abnormally turned off; the second frequency is higher than the operating frequency of the switching transistor in the second dual active conversion circuit after the power converter is started.

[0113] In one possible implementation, the control method further includes: In response to the fact that both the fifth and sixth switches are functioning normally, the fourth switch is activated. When the fourth switch is engaged normally, a shutdown command is sent to the fourth switch; the switching transistor in the first bidirectional conversion circuit operates at a first frequency, and the switching transistor in the second bidirectional conversion circuit operates at a second frequency. In response to the voltage at the third terminal of the second switch module being less than the fourth threshold, the fourth switch is determined to be abnormal.

[0114] The control method provided in this application embodiment enables the power converter to detect the first switching module, the second switching module, the main switch, and the pre-charge switch when the residual energy is low. This improves the accuracy and reliability of the power converter's switch fault detection, reduces the risk of the power converter operating with faults due to abnormalities in the first switching module, the second switching module, the main switch, or the pre-charge switch, and improves the operational safety of the power converter.

[0115] In one possible implementation, the control method provided in this application further includes: after the power converter stops, turning off the main switch; after a second preset time, causing the switching transistor in the first bidirectional conversion circuit to operate at a first frequency, and causing the switching transistor in the second bidirectional conversion circuit to operate at a second frequency; in response to the voltage of the intermediate bus of the first bidirectional conversion circuit and the voltage of the intermediate bus of the second bidirectional conversion circuit being less than a fifth threshold, turning off the switching transistors of the primary circuits of the first bidirectional conversion circuit and the second bidirectional conversion circuit; and in response to the voltage of the third terminal of the second switching module being less than the second threshold, and the change in the voltage of the third terminal of the second switching module being less than a sixth threshold within a preset number of preset periods, determining that the switching transistor is abnormal.

[0116] The power converter control method provided in this application controls the primary and secondary switching transistors of the conversion circuit to generate waves for energy discharge after the power converter stops and the switch is opened. When the intermediate bus voltage of the conversion circuit drops below the fifth threshold, the operation of the primary switching transistors is stopped, and the secondary side is used to continue to reduce the output voltage. This staged discharge method can adjust the switching transistors involved in the operation according to the voltage state of different nodes, and identify switching transistor abnormalities by the output voltage change.

[0117] This application does not specifically limit the implementation form of the controller 500. The controller 500 may include a digital signal processor (DSP), a field-programmable gate array (FPGA), a microcontroller unit (MCU), an application-specific integrated circuit (ASIC), or other devices with signal acquisition, logic judgment, and drive control functions.

[0118] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0119] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A power converter, characterized in that, include: The system comprises a first bidirectional conversion circuit, a second bidirectional conversion circuit, a first switching module, a second switching module, and a controller. The first terminal of the first bidirectional conversion circuit is connected to the first terminal of the first switching module, the first terminal of the second bidirectional conversion circuit is connected to the second terminal of the first switching module, and the third terminal of the first switching module is used to connect to a DC source. The second terminal of the first bidirectional conversion circuit is connected to the first terminal of the second switching module, the second terminal of the second bidirectional conversion circuit is connected to the second terminal of the second switching module, and the third terminal of the second switching module is used to connect to the load. The controller is configured to, before the power converter is powered on, control the switching transistor in the first bidirectional conversion circuit to operate, causing power to reciprocate between the first terminal and the second terminal of the first bidirectional conversion circuit, and control the switching transistor in the second bidirectional conversion circuit to operate, causing power to reciprocate between the first terminal and the second terminal of the second bidirectional conversion circuit, so as to discharge energy in the power converter; after the discharge is completed, in response to the voltage at the third terminal of the first switching module being greater than or equal to a first threshold, determine that the first switching module is abnormal or the switching transistor of the power converter is abnormal; Alternatively, in response to at least one of the voltage at the first terminal of the second switching module or the voltage at the second terminal of the second switching module being greater than or equal to a second threshold, it is determined that the second switching module is malfunctioning or the switching transistor of the power converter is malfunctioning.

2. The power converter according to claim 1, characterized in that, The first bidirectional conversion circuit and the second bidirectional conversion circuit have the same structure; The first bidirectional conversion circuit includes a first DC circuit and a first dual active conversion circuit. The first DC circuit is connected to the first dual active conversion circuit through an intermediate bus. The primary circuit of the first dual active conversion circuit includes a first bridge arm and a second bridge arm connected in parallel. The secondary circuit of the first dual active conversion circuit includes a third bridge arm and a fourth bridge arm connected in parallel. The controller is specifically configured to sequentially turn on the first group of switches, the second group of switches, the third group of switches, and the fourth group of switches in the first dual active converter circuit at a first frequency; the first group of switches includes the upper switch of the first bridge arm and the lower switch of the second bridge arm, the second group of switches includes the upper switch of the third bridge arm and the lower switch of the fourth bridge arm, the third group of switches includes the lower switch of the first bridge arm and the upper switch of the second bridge arm, and the fourth group of switches includes the lower switch of the third bridge arm and the upper switch of the fourth bridge arm; The first frequency is higher than the operating frequency of the switching transistor in the first dual active converter circuit after the power converter is started.

3. The power converter according to claim 2, characterized in that, Also includes: A main switch and a pre-charge switch; the first terminal of the main switch is connected to the DC source, and the second terminal of the main switch is connected to the positive terminal of the third terminal of the first switch module; the first terminal of the pre-charge switch is connected to the first terminal of the main switch, and the second terminal of the pre-charge switch is connected to the second terminal of the main switch through a resistor; The first switch module includes a first series switch module and a first parallel switch module. The first series switch module includes a first switch, and the first parallel switch module includes a second switch and a third switch. The positive terminal of the first end of the first bidirectional conversion circuit is connected to the positive terminal of the first end of the second bidirectional conversion circuit through the second switch. The negative terminal of the first end of the first bidirectional conversion circuit is connected to the positive terminal of the first end of the second bidirectional conversion circuit through the first switch. The negative terminal of the first end of the first bidirectional conversion circuit is connected to the negative terminal of the first end of the second bidirectional conversion circuit through the third switch. The controller is further configured to: in response to the voltage at the third terminal of the first switching module being less than a first threshold, and the first series switching module or the first parallel switching module being normal and the precharge switch being normal, send a shutdown command to the main switch; control the switching transistor in the first bidirectional conversion circuit to operate at the first frequency, control the switching transistor in the second bidirectional conversion circuit to operate at the second frequency, and determine that the main switch is abnormal in response to the voltage at both ends of the main switch being less than or equal to a third threshold; The second frequency is higher than the operating frequency of the switching transistor in the second dual active converter circuit after the power converter is started.

4. The power converter according to claim 2, characterized in that, Also includes: Main switch and precharge switch; The first terminal of the main switch is used to connect to the DC source, and the second terminal of the main switch is connected to the positive terminal of the third terminal of the first switch module; the first terminal of the precharge switch is used to connect to the first terminal of the main switch, and the second terminal of the precharge switch is connected to the second terminal of the main switch through a resistor; The second switch module includes a fourth switch, a fifth switch, and a sixth switch. The positive terminal of the second end of the first bidirectional conversion circuit is connected to the positive terminal of the second end of the second bidirectional conversion circuit through the fifth switch. The negative terminal of the second end of the first bidirectional conversion circuit is connected to the positive terminal of the second end of the second bidirectional conversion circuit through the fourth switch. The negative terminal of the second end of the first bidirectional conversion circuit is connected to the negative terminal of the second end of the second bidirectional conversion circuit through the sixth switch. The controller is further configured to, in response to the voltage at the first terminal of the second switching module being less than a second threshold and the voltage at the second terminal of the second switching module being less than the second threshold, the precharge switch and the main switch being normal, and the fifth switch and the sixth switch being normally engaged, send a shutdown command to the fifth switch and the sixth switch; cause the switching transistor in the first bidirectional conversion circuit to operate at the first frequency, cause the switching transistor in the second bidirectional conversion circuit to operate at the second frequency, and determine that at least one of the fifth switch or the sixth switch is abnormally shut down in response to the voltage at the third terminal of the second switching module being less than a fourth threshold; The second frequency is higher than the operating frequency of the switching transistor in the second dual active converter circuit after the power converter is started.

5. The power converter according to claim 4, characterized in that, The controller is also configured to engage the fourth switch in response to both the fifth and sixth switches being functioning normally. When the fourth switch is engaged normally, a shutdown command is sent to the fourth switch; the switching transistor in the first bidirectional conversion circuit operates at the first frequency, and the switching transistor in the second bidirectional conversion circuit operates at the second frequency. In response to the voltage at the third terminal of the second switch module being less than the fourth threshold, the fourth switch is determined to be abnormal.

6. The power converter according to any one of claims 3-5, characterized in that, The controller is also configured to stop detecting the first switching module, the second switching module, the main switch, or the precharge switch in response to the power converter being in anti-reverse current mode.

7. The power converter according to claim 2, characterized in that, Also includes: Main switch; The first terminal of the main switch is used to connect to the DC source, and the second terminal of the main switch is connected to the positive terminal of the third terminal of the first switch module; The controller is further configured to, after the power converter stops, turn off the main switch, and after a second preset time, cause the switching transistor in the first bidirectional conversion circuit to operate at the first frequency and the switching transistor in the second bidirectional conversion circuit to operate at the second frequency; and, if the voltage of the intermediate bus of the first bidirectional conversion circuit and the voltage of the intermediate bus of the second bidirectional conversion circuit are both less than a fifth threshold, turn off the switching transistors of the primary circuits of the first bidirectional conversion circuit and the second bidirectional conversion circuit; and, if the voltage at the third terminal of the second switching module is less than the second threshold and the change in voltage at the third terminal of the second switching module is less than a sixth threshold within a preset number of preset periods, determine that the switching transistor of the power converter is abnormal. The second frequency is higher than the operating frequency of the switching transistor in the second dual active converter circuit after the power converter is started.

8. A control method for a power converter, characterized in that, The power converter includes: a first bidirectional conversion circuit, a second bidirectional conversion circuit, a first switching module, and a second switching module; a first terminal of the first bidirectional conversion circuit is connected to a first terminal of the first switching module, a first terminal of the second bidirectional conversion circuit is connected to a second terminal of the first switching module, and a third terminal of the first switching module is used to connect to a DC source; a second terminal of the first bidirectional conversion circuit is connected to a first terminal of the second switching module, a second terminal of the second bidirectional conversion circuit is connected to a second terminal of the second switching module, and a third terminal of the second switching module is used to connect to a load; The control method includes: before the power converter is started, controlling the switching transistor in the first bidirectional conversion circuit to operate, so that power is reciprocated between the first terminal and the second terminal of the first bidirectional conversion circuit; controlling the switching transistor in the second bidirectional conversion circuit to operate, so that power is reciprocated between the first terminal and the second terminal of the second bidirectional conversion circuit, so as to discharge energy in the power converter; after the discharge is completed, in response to the voltage at the third terminal of the first switching module being greater than or equal to a first threshold, determining that the first switching module is abnormal or the switching transistor of the power converter is abnormal; or, in response to at least one of the voltage at the first terminal of the second switching module or the voltage at the second terminal of the second switching module being greater than or equal to a second threshold, determining that the second switching module is abnormal or the switching transistor of the power converter is abnormal.

9. The control method according to claim 8, characterized in that, The first bidirectional conversion circuit and the second bidirectional conversion circuit have the same structure; the first bidirectional conversion circuit includes a first DC circuit and a first dual active conversion circuit. The first DC circuit is connected to the first dual active conversion circuit through an intermediate bus. The primary circuit of the first dual active conversion circuit includes a first bridge arm and a second bridge arm connected in parallel. The secondary circuit of the first dual active conversion circuit includes a third bridge arm and a fourth bridge arm connected in parallel. The control method specifically includes: sequentially turning on the first group of switches, the second group of switches, the third group of switches, and the fourth group of switches in the first dual active converter circuit at a first frequency; the first group of switches includes the upper switch of the first bridge arm and the lower switch of the second bridge arm, the second group of switches includes the upper switch of the third bridge arm and the lower switch of the fourth bridge arm, the third group of switches includes the lower switch of the first bridge arm and the upper switch of the second bridge arm, and the fourth group of switches includes the lower switch of the third bridge arm and the upper switch of the fourth bridge arm; The first frequency is higher than the operating frequency of the switching transistor in the first dual active converter circuit after the power converter is started.

10. The control method according to claim 9, characterized in that, The power converter further includes: a main switch and a pre-charge switch; the first terminal of the main switch is connected to the DC source, and the second terminal of the main switch is connected to the positive terminal of the third terminal of the first switch module; the first terminal of the pre-charge switch is connected to the first terminal of the main switch, and the second terminal of the pre-charge switch is connected to the second terminal of the main switch through a resistor; the first switch module includes a first series switch module and a first parallel switch module, the first series switch module includes a first switch, and the first parallel switch module includes a second switch and a third switch; the positive terminal of the first terminal of the first bidirectional conversion circuit is connected to the positive terminal of the first terminal of the second bidirectional conversion circuit through the second switch, the negative terminal of the first terminal of the first bidirectional conversion circuit is connected to the positive terminal of the first terminal of the second bidirectional conversion circuit through the first switch, and the negative terminal of the first terminal of the first bidirectional conversion circuit is connected to the negative terminal of the first terminal of the second bidirectional conversion circuit through the third switch; The control method further includes: in response to the voltage at the third terminal of the first switching module being less than a first threshold, and the first series switching module or the first parallel switching module being normal and the precharge switch being normal, sending a shutdown command to the main switch; controlling the switching transistor in the first bidirectional conversion circuit to operate at the first frequency, controlling the switching transistor in the second bidirectional conversion circuit to operate at the second frequency, and in response to the voltage at both ends of the main switch being less than or equal to a third threshold, determining that the main switch is abnormal; The second frequency is higher than the operating frequency of the switching transistor in the second dual active converter circuit after the power converter is started.

11. The control method according to claim 9, characterized in that, The power converter further includes: a main switch and a pre-charge switch; the first terminal of the main switch is connected to the DC source, and the second terminal of the main switch is connected to the positive terminal of the third terminal of the first switch module; the first terminal of the pre-charge switch is connected to the first terminal of the main switch, and the second terminal of the pre-charge switch is connected to the second terminal of the main switch through a resistor; the second switch module includes a fourth switch, a fifth switch, and a sixth switch, the positive terminal of the second terminal of the first bidirectional conversion circuit is connected to the positive terminal of the second terminal of the second bidirectional conversion circuit through the fifth switch, the negative terminal of the second terminal of the first bidirectional conversion circuit is connected to the positive terminal of the second terminal of the second bidirectional conversion circuit through the fourth switch, and the negative terminal of the second terminal of the first bidirectional conversion circuit is connected to the negative terminal of the second terminal of the second bidirectional conversion circuit through the sixth switch; The control method further includes: in response to the voltage at the first terminal of the second switching module being less than a second threshold and the voltage at the second terminal of the second switching module being less than the second threshold, the precharge switch and the main switch being normal, and the fifth switch and the sixth switch being normally engaged, sending a shutdown command to the fifth switch and the sixth switch; causing the switching transistor in the first bidirectional conversion circuit to operate at the first frequency, causing the switching transistor in the second bidirectional conversion circuit to operate at the second frequency, and in response to the voltage at the third terminal of the second switching module being less than a fourth threshold, determining that at least one of the fifth switch or the sixth switch is abnormally shut down; the second frequency is higher than the operating frequency of the switching transistor in the second dual active conversion circuit after the power converter is started.

12. The control method according to claim 11, characterized in that, Also includes: In response to the fact that both the fifth and sixth switches are functioning normally, the fourth switch is activated. When the fourth switch is engaged normally, a shutdown command is sent to the fourth switch; the switching transistor in the first bidirectional conversion circuit operates at the first frequency, and the switching transistor in the second bidirectional conversion circuit operates at the second frequency. In response to the voltage at the third terminal of the second switch module being less than the fourth threshold, the fourth switch is determined to be abnormal.

13. The control method according to claim 9, characterized in that, The power converter further includes: a main switch; a first terminal of the main switch is connected to the DC source, and a second terminal of the main switch is connected to the positive terminal of the third terminal of the first switching module; the control method further includes: after the power converter stops, turning off the main switch; after a second preset time, causing the switching transistor in the first bidirectional conversion circuit to operate at a first frequency, and causing the switching transistor in the second bidirectional conversion circuit to operate at a second frequency; in response to the voltage of the intermediate bus of the first bidirectional conversion circuit and the voltage of the intermediate bus of the second bidirectional conversion circuit being less than a fifth threshold, turning off the switching transistors of the primary circuits of the first bidirectional conversion circuit and the second bidirectional conversion circuit; and in response to the voltage of the third terminal of the second switching module being less than the second threshold, and the change in the voltage of the third terminal of the second switching module being less than a sixth threshold within a preset number of preset periods, determining that the switching transistor of the power converter is abnormal.

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