Ac / dc converter and charging device

Abstract

The application provides an AC / DC converter and a charging device, and belongs to the technical field of power electronics. The AC / DC converter comprises a controller and a multi-phase AC / DC conversion circuit. The current flowing through the first winding of the autotransformer in each phase AC / DC conversion circuit is the first current, and the current flowing through the second winding of the autotransformer is the second current. When the current difference between the first current and the second current in any phase AC / DC conversion circuit is greater than or equal to a current threshold, the controller can determine that the phase AC / DC conversion circuit has a fault, and turn off the switch in the multi-phase AC / DC conversion circuit to realize fault isolation. Since the above scheme can realize fault detection according to the current flowing through the autotransformer, and realize fault isolation by turning off the switch in the AC / DC conversion circuit, the AC / DC converter does not need to additionally increase the power switch device, and the structural complexity and hardware cost are relatively low.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to an AC / DC converter and charging device. Background Technology

[0002] Charging stations typically include multiple alternating current / direct current (AC / DC) converters, multiple DC / DC converters, and multiple charging guns. The AC terminals of the multiple AC / DC converters are all connected to the power grid, and the DC terminals of the multiple AC / DC converters are connected to the multiple charging guns through the multiple DC / DC converters. Furthermore, the DC terminals of the aforementioned multiple AC / DC converters are connected in parallel.

[0003] Because the DC terminals of multiple AC / DC converters are connected in parallel, a short-circuit fault in any one AC / DC converter can easily spread to the entire charging station. To prevent this, a power switching device (such as a switching transistor) is typically added to the DC terminal of each AC / DC converter. When a short-circuit fault occurs in any AC / DC converter, the power switching device connected to the DC terminal of that AC / DC converter can be disconnected, thereby isolating the faulty AC / DC converter from the others.

[0004] However, the above fault protection scheme requires additional power switching devices, which increases the structural complexity and hardware cost of the charging pile. Summary of the Invention

[0005] This application provides an AC / DC converter and a charging device that can solve the problem of timely isolation of the AC / DC converter with a short circuit fault when multiple AC / DC converters are connected in parallel in a charging device, while also solving the technical problem of increasing the structural complexity and hardware cost of the charging device due to the need to add power switching devices.

[0006] In a first aspect, an AC / DC converter is provided, comprising: a controller and a multi-phase AC / DC conversion circuit. Each phase of the AC / DC conversion circuit includes: a switch, an inductor, an autotransformer, a first rectifier bridge arm, and a second rectifier bridge arm; the autotransformer includes a first winding and a second winding. One end of the switch is connected to an AC power source, and the other end of the switch is connected to one end of the inductor. The other end of the inductor is connected to one end of the first winding and one end of the second winding, respectively. The other end of the first winding is connected to the first rectifier bridge arm, and the other end of the second winding is connected to the second rectifier bridge arm. The controller is used to turn off the switch in the multi-phase AC / DC conversion circuit when the current difference between a first current and a second current in any phase of the AC / DC conversion circuit is greater than or equal to a current threshold. The first current is the current flowing through the first winding of the any phase of the AC / DC conversion circuit, and the second current is the current flowing through the second winding of the any phase of the AC / DC conversion circuit.

[0007] Since the first current and the second current in each phase of the AC / DC converter circuit are equal or approximately equal when all phases of the AC / DC converter circuit are operating normally, the controller can determine that a fault exists in that phase of the AC / DC converter circuit when it detects that the current difference between the first current and the second current in any phase of the AC / DC converter circuit is greater than or equal to a current threshold. Accordingly, the controller can disconnect the faulty AC / DC converter from the AC power supply by turning off the switches in each phase of the AC / DC converter circuit, thereby isolating the faulty AC / DC converter from other normal AC / DC converters and preventing the fault from spreading. Furthermore, the solution provided in this application can achieve fault detection based on the current flowing through the autotransformer and achieve fault isolation by turning off the switches in the AC / DC converter circuit. Therefore, the AC / DC converter does not require additional power switching devices, resulting in lower structural complexity and hardware cost.

[0008] In one embodiment, the current threshold is greater than or equal to 1 / 10 of the current flowing through the autotransformer when the AC / DC converter outputs its rated power. The current flowing through the autotransformer can refer to the sum of the currents flowing through the first winding and the second winding. By setting the current threshold to be greater than 1 / 10 of the rated current flowing through the autotransformer when the AC / DC converter outputs its rated power, false fault detections can be effectively avoided.

[0009] In one embodiment, each of the first and second rectifier bridge arms includes at least one switching transistor. The controller is configured to first turn off the switching transistor in the multiphase AC / DC converter circuit, and then turn off the switch in the multiphase AC / DC converter circuit.

[0010] It is understandable that turning off the switches in a multi-phase AC / DC converter circuit reduces the current flowing through each phase of the AC / DC converter circuit, thereby reducing the current flowing through the switches in each phase of the AC / DC converter circuit. It is also understandable that when the controller turns off the switches, if the current flowing through the switches is large, the switch contacts may stick together, leading to failure in fault isolation. In the solution provided in this application, by first turning off the switches in the multi-phase AC / DC converter circuit, it can be ensured that the current flowing through each switch is small when turning off the switches in each phase of the AC / DC converter circuit, thereby ensuring that each switch can be effectively turned off. Thus, effective isolation of the faulty AC / DC converter can be achieved.

[0011] In one embodiment, the controller is used to turn off the switch in the multiphase AC / DC converter circuit when the off-time of the switching transistor reaches a duration threshold.

[0012] In the solution provided in this application, when the turn-off time of the switching transistor reaches a time threshold, the current flowing through the switch will be less than a certain threshold, which can be less than or equal to the maximum breaking current of the switch. At this time, the controller then controls all switches in the multi-phase AC / DC conversion circuit to turn off, which can effectively prevent switch damage.

[0013] In one embodiment, the aforementioned duration threshold is on the order of microseconds, milliseconds, or seconds. Because this duration threshold is small, the controller can shut off the switches in the multi-phase AC / DC converter circuit shortly after turning off the switching transistor. This ensures timely isolation of the faulty AC / DC converter from the AC power supply, thereby effectively protecting other AC / DC converters within the system.

[0014] In one embodiment, the controller can, after turning off the switches in the multi-phase AC / DC converter circuit, further turn off all switches in the multi-phase AC / DC converter circuit if it detects that the current flowing through the switch in any phase of the AC / DC converter circuit is less than the maximum breaking current of that switch. This not only effectively prevents switch damage but also ensures timely and effective fault isolation.

[0015] In one embodiment, the controller can, after turning off the switches in the multi-phase AC / DC converter circuit, further turn off all switches in the multi-phase AC / DC converter circuit only after detecting that the current flowing through the switches in each phase of the AC / DC converter circuit is less than the maximum breaking current of that switch. This effectively prevents damage to the switches in each phase of the AC / DC converter circuit and ensures effective fault isolation.

[0016] In one embodiment, the AC / DC converter further includes: a positive DC bus, a negative DC bus, a first bus capacitor, and a second bus capacitor. Each of the first and second rectifier bridge arms is connected to both the positive and negative DC buses, respectively. The first and second bus capacitors are connected in series between the positive and negative DC buses. The controller is configured to turn off the switches in the multi-phase AC / DC converter circuit when the current difference between a first current and a second current in any phase of the AC / DC converter circuit is greater than or equal to a current threshold, and the voltage difference between the first half-bus voltage and the second half-bus voltage is greater than or equal to a voltage threshold. The first half-bus voltage is the voltage between the positive DC bus and the bus midpoint, and the second half-bus voltage is the voltage between the negative DC bus and the bus midpoint. The bus midpoint is the series connection node between the first and second bus capacitors.

[0017] It is understandable that when a fault occurs in any phase of the AC / DC converter circuit, the fault current in that faulty AC / DC converter circuit will charge one of the first and second bus capacitors, leading to a significant deviation between the first and second half-bus voltages. In the solution provided in this application, since the controller can simultaneously use the difference in autotransformer current and the difference in half-bus voltage as the basis for fault judgment, it can effectively improve the accuracy of fault detection and reduce the probability of false triggering of fault protection actions (i.e., the action of shutting off the switch).

[0018] In one embodiment, the voltage threshold Vt satisfies: Vt / 2 < V1 - V2. This formula can also be transformed to: Vt < 2 × (V1 - V2). Where V1 is the smaller of the withstand voltage values ​​of the first bus capacitor and the second bus capacitor, and V2 is the rated half-bus voltage, which is half of the rated voltage between the positive DC bus and the negative DC bus. V1 is also referred to as the target withstand voltage value.

[0019] It is understandable that the rated half-bus voltage V2 is also the rated voltage of each bus capacitor, meaning the rated voltages of the two bus capacitors are equal. Furthermore, this rated voltage is less than the withstand voltage of any bus capacitor, i.e., less than the target withstand voltage V1. It is also understandable that the withstand voltage of a bus capacitor can refer to the maximum voltage it can withstand; this withstand voltage can also be called the minimum breakdown voltage of the bus capacitor. In other words, if the voltage across any bus capacitor exceeds its withstand voltage, that bus capacitor is at risk of overvoltage breakdown.

[0020] When a fault occurs in any phase of the AC / DC converter circuit, the voltage across the first bus capacitor and / or the second bus capacitor will change compared to the rated half-bus voltage V2. If the changed voltage is less than the target withstand voltage V1, overvoltage breakdown of the bus capacitor can be avoided. That is, for each bus capacitor, if the change in voltage across it from the rated half-bus voltage V2 is less than (V1-V2), overvoltage breakdown of the bus capacitor can be avoided. Furthermore, when a fault occurs in any phase of the AC / DC converter circuit, the voltage across one of the first and second bus capacitors will increase compared to the rated half-bus voltage V2, while the voltage across the other bus capacitor will decrease compared to the rated half-bus voltage V2. Therefore, by setting a voltage threshold Vt / 2+V2<V1, i.e., Vt<2×(V1-V2), it can be ensured that the switch in the multi-phase AC / DC converter circuit is disconnected in time before the voltage across any bus capacitor reaches the target withstand voltage V1. This ensures that the voltage across each bus capacitor is within its tolerance range, thereby effectively reducing the risk of overvoltage breakdown of the bus capacitor.

[0021] Secondly, a charging device is provided, comprising: an AC / DC converter, a DC / DC converter, and a charging gun as described in the first aspect above, wherein the output of the AC / DC converter is connected to the charging gun via the DC / DC converter. The charging gun can be used to connect to an electric vehicle.

[0022] The AC / DC converter converts the AC power supplied by the AC power source into DC power, while the DC / DC converter converts the DC power output from the AC / DC converter into voltage and outputs it to the charging gun, thereby supplying power to the electric vehicle connected to the charging gun.

[0023] In summary, this application provides an AC / DC converter and a charging device. The AC / DC converter includes a controller and a multi-phase AC / DC conversion circuit. In each phase of the AC / DC conversion circuit, the current flowing through the first winding of the autotransformer is a first current, and the current flowing through the second winding of the autotransformer is a second current. The controller can determine that a fault exists in the phase of the AC / DC conversion circuit when the difference between the first and second currents in any phase is greater than or equal to a current threshold, and then shuts off the switches in the multi-phase AC / DC conversion circuit. This disconnects the faulty AC / DC converter from the AC power supply, isolating the faulty AC / DC converter from other normal AC / DC converters and preventing fault propagation. Furthermore, the solution provided in this application can directly achieve fault isolation through the switches in the multi-phase AC / DC conversion circuit; therefore, the AC / DC converter does not require additional power switching devices, resulting in lower structural complexity and hardware cost. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of a charging device provided in an embodiment of this application;

[0025] Figure 2 This is a schematic diagram of another charging device provided in an embodiment of this application;

[0026] Figure 3 This is a schematic diagram of the structure of another charging device provided in the embodiments of this application;

[0027] Figure 4 This is a schematic diagram of the structure of an AC / DC converter provided in an embodiment of this application;

[0028] Figure 5 This is a schematic diagram of the software protection logic of an AC / DC converter provided in an embodiment of this application;

[0029] Figure 6 This is a partial structural schematic diagram of an AC / DC converter provided in an embodiment of this application;

[0030] Figure 7 This is a schematic diagram of the software protection logic of another AC / DC converter provided in an embodiment of this application;

[0031] Figure 8 This is a schematic diagram of the current path of short-circuit current in an AC / DC converter provided in an embodiment of this application;

[0032] Figure 9 This is a schematic diagram of the current path of the short-circuit current in another AC / DC converter provided in this application embodiment;

[0033] Figure 10 This is a schematic diagram of the current circulation path in a charging device provided in an embodiment of this application. Detailed Implementation

[0034] The AC / DC converter and charging device provided in the embodiments of this application are described in detail below with reference to the accompanying drawings.

[0035] Figure 1 This is a schematic diagram of the structure of a charging device provided in an embodiment of this application, and Figure 1 The following diagram illustrates the charging equipment as a charging station. Figure 1As shown, the charging device includes multiple AC / DC converters 10. The AC terminals (also called input terminals) of these AC / DC converters 10 are used to connect to an AC power source, such as a power grid. The DC terminals (also called output terminals) of these AC / DC converters 10 are connected in parallel to a DC bus. Each of the multiple AC / DC converters 10 is used to convert the AC power supplied by the AC power source into DC power and output it to the DC bus. The AC / DC converters 10 can also be referred to as AC / DC modules or rectifier modules. Because the topology of the AC / DC converters 10 is a non-isolated topology, and the DC terminals of the multiple AC / DC converters 10 are connected in parallel, the above architecture is also called a non-isolated architecture or a non-isolated charging architecture.

[0036] like Figure 1 As shown, the charging device may also include multiple DC / DC converters 20 and multiple charging guns 30. One end of each DC / DC converter 20 is connected in parallel to a DC bus, and the other end of each DC / DC converter 20 is connected to multiple charging guns 30. For example, see reference... Figure 1 The charging equipment also includes a power distribution module 40, through which the other ends of the plurality of DC / DC converters 20 are connected to a plurality of charging guns 30. The plurality of DC / DC converters 20 are used to convert the DC power on the DC bus. The power distribution module 40 is used to distribute the output power of at least one of the plurality of DC / DC converters 20 to at least one of the plurality of charging guns 30. Each charging gun 30 is used to connect to an electric vehicle and to charge the electric vehicle.

[0037] Figure 1 This explanation uses the example of connecting the output of AC / DC converter 10 to DC / DC converter 20 via a DC bus. That is, the outputs of multiple AC / DC converters 10 are connected in parallel to the DC bus, and one end of multiple DC / DC converters 20 is then connected in parallel to the DC bus. It can be understood that, as... Figure 2 As shown, the output of AC / DC converter 10 can also be directly connected to one end of DC / DC converter 20. For example, refer to... Figure 2 The output terminals of multiple AC / DC converters 10 are connected one-to-one with one end of multiple DC / DC converters 20.

[0038] It is also understood that the AC / DC converter 10 and DC / DC converter 20 in the charging device can be independent converters, or the DC / DC converter 20 can be integrated into the AC / DC converter 10. That is, the AC / DC converter 10 not only has AC / DC conversion function, but also DC / DC conversion function. Accordingly, there is no need to set up a separate DC / DC converter 20 in the charging device.

[0039] In the aforementioned charging equipment, a fault within a single AC / DC converter 10 can easily propagate to other AC / DC converters 10 within the charging equipment, causing damage to those other AC / DC converters 10. Therefore, achieving fault isolation within a single AC / DC converter 10 is a key factor in ensuring the reliability of the entire charging equipment.

[0040] In some embodiments, such as Figure 3 As shown, a fuse is typically added between the DC terminal (i.e., output terminal) and the DC bus of each AC / DC converter 10. When an AC / DC converter 10 fails, i.e., a single point of failure occurs in the charging equipment, the remaining AC / DC converters 10 can supply current to the output terminal of the failed AC / DC converter 10, thus blowing the fuse connected to the output terminal of the failed AC / DC converter 10. This achieves isolation between the failed AC / DC converter 10 and other AC / DC converters 10. However, this scheme requires ensuring that the other AC / DC converters 10, when supplying current, can blow the fuse connected to the failed AC / DC converter 10, but not the fuse connected to their own output terminals. In other words, this scheme requires coordination among the AC / DC converters 10, placing high demands on the current sharing coefficient of the system (i.e., the charging equipment).

[0041] In other embodiments, power switching devices (such as switching transistors or diodes) can be added between the DC terminal and the DC bus of each AC / DC converter 10. The AC / DC converter 10 performs software protection by identifying abnormal voltages or currents. Software protection refers to disconnecting the power switching devices to isolate the AC / DC converter 10 from other AC / DC converters 10. However, this approach requires additional power switching devices, increasing the structural complexity and hardware cost of the charging equipment. Furthermore, to ensure effective fault isolation, high-power, low-loss, and fast-response power switching devices are typically required, and such devices are expensive.

[0042] This application provides an AC / DC converter that can be applied to, for example... Figure 1 In the application scenario shown, this AC / DC converter can isolate itself from other AC / DC converters in the event of a fault, preventing the escalation of a single point of failure. For example... Figure 4 As shown, the AC / DC converter provided in this embodiment includes: a controller 11 and a multiphase AC / DC conversion circuit 12. For example, Figure 4 The diagram schematically illustrates a three-phase AC / DC converter circuit 12.

[0043] Each phase of the AC / DC converter circuit 12 includes: a switch K, an inductor L, an autotransformer T, a first rectifier bridge arm 121, and a second rectifier bridge arm 122. The autotransformer T includes a first winding T1 and a second winding T2. Each of the first rectifier bridge arms 121 and the second rectifier bridge arm 122 includes at least one switching transistor.

[0044] Continue to refer to Figure 4 One end of switch K is connected to the AC power supply, and the other end of switch K is connected to one end of inductor L. The other end of inductor L is connected to one end of the first winding T1 and one end of the second winding T2. The other end of the first winding T1 is connected to the first rectifier bridge arm 121, and the other end of the second winding T2 is connected to the second rectifier bridge arm 122. Switch K is also called the pre-stage switch.

[0045] Understandably, this AC / DC converter may also include a DC bus. For example... Figure 4 As shown, the DC bus includes a positive DC bus BUS+ and a negative DC bus BUS-. The AC terminal (i.e., one end of switch K) of each phase AC / DC converter circuit 12 can be used to receive one phase of AC power from the AC power supply, and the DC terminal (i.e., the bus terminals of the first rectifier bridge arm 121 and the second rectifier bridge arm 122) of each phase AC / DC converter circuit 12 is connected to the DC bus. Each phase AC / DC converter circuit 12 is used to convert the received one phase of AC power into DC power and output it to the DC bus. Figure 4 As shown, assuming the AC power supply is used to provide three-phase (i.e., phase A, phase B, and phase C) AC power, the AC / DC converter may include three-phase AC / DC conversion circuits 12 corresponding to the three-phase AC power, namely, phase A AC / DC conversion circuit 12, phase B AC / DC conversion circuit 12, and phase C AC / DC conversion circuit 12. Alternatively, the AC / DC converter may not need to include a DC bus, in which case the DC terminal of each phase AC / DC conversion circuit 12 can be directly connected to the DC / DC converter.

[0046] The controller 11 is configured to turn off the switch K in the multi-phase AC / DC converter circuit 12 when the current difference between the first current and the second current in any phase AC / DC converter circuit 12 is greater than or equal to a current threshold. The aforementioned current difference can refer to the absolute value of the difference between the first current and the second current. The first current is the current flowing through the first winding T1 in the any phase AC / DC converter circuit 12, and the second current is the second current flowing through the second winding T2 in the any phase AC / DC converter circuit 12. The first current and the second current can also be referred to as autotransformer currents.

[0047] It is also understandable that, for each phase of the AC / DC converter circuit 12, during normal operation, the first current flowing through the first winding T1 is equal to or approximately equal to the second current flowing through the second winding T2. That is, under normal circumstances, the current difference between the first current and the second current is zero or close to zero. When a fault occurs in a certain phase of the AC / DC converter circuit 12, for example, when a switch in the first rectifier bridge arm 121 or the second rectifier bridge arm 122 is short-circuited or open-circuited, it will cause a large difference between the first current flowing through the first winding T1 and the second current flowing through the second winding T2, that is, the current difference between the first current and the second current will increase.

[0048] In this embodiment, the controller 11 may pre-store the aforementioned current threshold. Furthermore, this current threshold can be determined based on the range of variation of the current difference between the first current and the second current during normal operation of the AC / DC conversion circuit 12. For example, the current threshold may be greater than the upper limit of this range.

[0049] In one embodiment, the aforementioned current threshold can be greater than or equal to 1 / 10 of the current flowing through the autotransformer T when the AC / DC converter outputs its rated power. The current flowing through the autotransformer T can refer to the sum of the currents flowing through the first winding T1 and the second winding T2. By setting the current threshold to be greater than 1 / 10 of the rated current flowing through the autotransformer T when the AC / DC converter outputs its rated power, false fault detections can be effectively avoided. It is understood that when the AC / DC converter outputs its rated power, i.e., when the AC / DC converter is operating at its rated capacity, the current flowing through the autotransformer T in each phase of the AC / DC conversion circuit 12 is equal.

[0050] Based on the above analysis, it can be seen that when the controller 11 detects that the current difference between the first current and the second current in any phase AC / DC converter circuit 12 is greater than or equal to the current threshold, it can determine that the phase AC / DC converter circuit 12 has a fault, and then it can shut off the switch K in the multi-phase AC / DC converter circuit 12. This isolates the faulty AC / DC converter from the AC power supply, thereby effectively isolating the faulty AC / DC converter from other AC / DC converters in the system (such as charging equipment), preventing the fault from spreading and causing damage to other AC / DC converters.

[0051] Furthermore, the AC / DC converter provided in this application embodiment can detect faults based on the current flowing through the autotransformer and isolate faults by turning off the switches in the AC / DC conversion circuit. Therefore, fault protection can be achieved without adding additional fault detection and protection devices to the AC / DC converter, resulting in lower structural complexity and hardware cost. Moreover, this AC / DC converter does not require coordination with other AC / DC converters when performing fault isolation, thus requiring a lower system current sharing coefficient.

[0052] In one embodiment, reference continues... Figure 4 The AC / DC converter further includes a current detection circuit 13, which detects a first current and a second current in each phase of the AC / DC converter circuit 12. Correspondingly, a controller 11 is configured to acquire the first current and the second current detected by the current detection circuit 13 in each phase of the AC / DC converter circuit 12.

[0053] In one embodiment, reference continues... Figure 4 The AC / DC converter further includes a first bus capacitor C1 and a second bus capacitor C2 connected in series between the positive DC bus BUS+ and the negative DC bus BUS-. The series connection point between the first bus capacitor C1 and the second bus capacitor C2 is the bus midpoint O. Each rectifier bridge arm 121 and the second rectifier bridge arm 122 is also connected to the positive DC bus BUS+, the negative DC bus BUS-, and the bus midpoint O, respectively. The first bus capacitor C1 is connected to the positive DC bus BUS+, and can also be referred to as the positive bus capacitor. The second bus capacitor C2 is connected to the negative DC bus BUS-, and can also be referred to as the negative bus capacitor.

[0054] In one embodiment, each of the first rectifier bridge arm 121 and the second rectifier bridge arm 122 includes at least one switching transistor. The switching transistor may be a metal-oxide-semiconductor field-effect transistor (MOSFET) or an insulated-gate bipolar transistor (IGBT).

[0055] The controller 11 is configured to first turn off the switching transistors in the multiphase AC / DC converter circuit 12, and then turn off the switch K in the multiphase AC / DC converter circuit 12. That is, when the controller 11 detects that the current difference between the first current and the second current in any phase AC / DC converter circuit 12 is greater than or equal to a current threshold, it can first turn off the switching transistors in each rectifier bridge arm of the multiphase AC / DC converter circuit 12, and then turn off the switch K in the multiphase AC / DC converter circuit 12.

[0056] Understandably, by turning off the switching transistors in each rectifier bridge arm of the multi-phase AC / DC converter circuit 12, the current flowing through each phase of the AC / DC converter circuit 12 can be effectively reduced, thereby reducing the current flowing through switch K. This avoids damage to switch K caused by turning it off when the current flowing through it is too high, thus ensuring effective fault isolation.

[0057] In one embodiment, the switches K in each phase of the AC / DC converter circuit 12 are relays. It is understood that when the controller 11 detects that the current difference between the first current and the second current in any phase of the AC / DC converter circuit 12 is greater than or equal to a current threshold, the current flowing through the switch K (i.e., the relay) is relatively large. In this case, if the controller 11 directly turns off the relay, it may cause the relay to arc, leading to contact sticking. In this embodiment, since the controller 11 can first turn off the switches in each rectifier bridge arm, the current flowing through the relay is effectively reduced, thereby effectively preventing contact sticking caused by relay disconnection under high current conditions. Therefore, it can be ensured that the relays in each phase of the AC / DC converter circuit 12 can effectively disconnect, thus achieving effective fault isolation.

[0058] In one embodiment, the controller 11 is used to turn off the switch K in the multiphase AC / DC converter circuit 12 when the turn-off time of the switching transistors in the first rectifier bridge arm 121 and the second rectifier bridge arm 122 reaches a time threshold.

[0059] Understandably, after all the switches in each rectifier bridge arm of each phase AC / DC converter circuit 12 are turned off, the current in each phase AC / DC converter circuit 12 can charge the bus capacitors (e.g., the first bus capacitor C1 or the second bus capacitor C2). During the charging process of the bus capacitors, the current flowing through switch K will gradually decrease to zero. When the turn-off time of the switch reaches a time threshold, the current flowing through switch K will be less than a certain threshold, which can be less than or equal to the maximum breaking current of switch K. At this time, the controller 11 controls all switches K in the multi-phase AC / DC converter circuit 12 to turn off, which can effectively prevent damage to switches K.

[0060] The duration threshold can be pre-stored in the controller 11. Furthermore, the duration threshold can be determined based on the parameters of each device in each phase AC / DC conversion circuit 12, the parameters of the bus capacitor, the parameters of the AC power supply, and the maximum current that switch K can interrupt.

[0061] In one embodiment, the duration threshold can be on the order of microseconds, milliseconds, or seconds. Because this duration threshold is small, the controller 11 can turn off switch K in the multi-phase AC / DC converter circuit 12 shortly after turning off the switching transistor. This ensures timely isolation of the faulty AC / DC converter from the AC power supply, achieving rapid isolation of single-point faults and effective protection for other AC / DC converters within the system.

[0062] Figure 5 This is a schematic diagram of the software protection logic of an AC / DC converter provided in an embodiment of this application. From Figure 5 As can be seen, when the controller 11 detects that the current difference in any phase AC / DC converter circuit 12 is greater than or equal to the current threshold, it can first use software protection to turn off the switching transistor and start timing. When the timing duration reaches the duration threshold, that is, when the timing stops and no large current flows through switch K, switch K in the multi-phase AC / DC converter circuit 12 is turned off to achieve fault isolation.

[0063] In one embodiment, the controller 11 can also detect the current flowing through the switch K in each phase of the AC / DC converter circuit 12 after turning off the switches in the multi-phase AC / DC converter circuit 12, and control the switch K in the multi-phase AC / DC converter circuit 12 to turn off only when the current flowing through the switch K in any phase AC / DC converter circuit 12 is less than the maximum breaking current of that switch K. This not only effectively avoids damage to the switch K, but also ensures rapid fault isolation.

[0064] In one embodiment, after the controller 11 turns off the switches in the multi-phase AC / DC converter circuit 12, it can further control the switches K in the multi-phase AC / DC converter circuit 12 to turn off again when it detects that the current flowing through each switch K in the multi-phase AC / DC converter circuit 12 is less than the maximum breaking current of the switch K. This effectively prevents damage to the switches K in each phase of the AC / DC converter circuit 12.

[0065] For example, the controller 11 can directly detect the current flowing through the switch K in each phase of the AC / DC converter circuit 12 via the aforementioned current detection circuit 13. Furthermore, for each phase of the AC / DC converter circuit 12, the current flowing through the switch K in that phase is the sum of the first current and the second current in that phase. It is also understood that the maximum breaking current of the switch K in each phase of the AC / DC converter circuit 12 can be equal.

[0066] In one embodiment, the controller 11 is configured to turn off switch K in the multi-phase AC / DC converter circuit 12 when the current difference between a first current and a second current in any phase AC / DC converter circuit 12 is greater than or equal to a current threshold, and the voltage difference between the first half-bus voltage and the second half-bus voltage is greater than or equal to a voltage threshold. The aforementioned voltage difference may refer to the absolute value of the difference between the first half-bus voltage and the second half-bus voltage. Here, the first half-bus voltage refers to the voltage between the positive DC bus BUS+ and the bus midpoint O, and the second half-bus voltage refers to the voltage between the negative DC bus BUS- and the bus midpoint O.

[0067] Figure 6 This is a partial structural schematic diagram of an AC / DC converter provided in an embodiment of this application. For example... Figure 6 As shown, the AC / DC converter may further include a voltage detection circuit 14. This voltage detection circuit 14 can be used to detect the first half-bus voltage between the positive DC bus BUS+ and the bus midpoint O, and the second half-bus voltage between the negative DC bus BUS- and the bus midpoint O. Correspondingly, the controller 11 can acquire the first half-bus voltage and the second half-bus voltage detected by the voltage detection circuit 14.

[0068] It is understandable that the aforementioned first half-bus voltage is the voltage across the first bus capacitor C1, and the second half-bus voltage is the voltage across the second bus capacitor C2. When all phases of the AC / DC converter circuit 12 are operating normally, the first half-bus voltage and the second half-bus voltage are equal or approximately equal. That is, under normal conditions, the voltage difference between the first half-bus voltage and the second half-bus voltage is zero or close to zero.

[0069] When a fault occurs in any phase of the AC / DC converter circuit 12, for example, when a switch in any phase of the AC / DC converter circuit 12 is short-circuited or open-circuited, the current in the faulty AC / DC converter circuit 12 will charge one of the first bus capacitors C1 and C2, which will cause a significant deviation between the first half-bus voltage and the second half-bus voltage. That is, the voltage difference between the first half-bus voltage and the second half-bus voltage will increase significantly. Correspondingly, the controller 11 will detect that the voltage difference between the first half-bus voltage and the second half-bus voltage is greater than or equal to a voltage threshold.

[0070] It is understood that the controller 11 can pre-store the aforementioned voltage threshold. Furthermore, this voltage threshold can be determined based on the range of variation of the voltage difference between the first half-bus voltage and the second half-bus voltage when all phase AC / DC conversion circuits 12 are operating normally. For example, the voltage threshold may be greater than the upper limit of this range. Therefore, when the controller 11 detects that the voltage difference between the first half-bus voltage and the second half-bus voltage is greater than or equal to the voltage threshold, it can determine that at least one phase AC / DC conversion circuit 12 has failed. Thus, it can promptly shut off the switches K in each phase AC / DC conversion circuit 12, thereby isolating the faulty AC / DC converter from the AC power supply.

[0071] It is also understandable that if the controller 11 detects whether the AC / DC conversion circuit 12 is faulty based solely on the difference between the first current and the second current (i.e., the difference in autotransformer current), there may be a certain probability of false detection, which could lead to false triggering of the fault protection action, i.e., false shut-off of switch K. However, in this embodiment, since the controller 11 can simultaneously use the difference in autotransformer current and the difference in half-bus voltage as the basis for fault judgment, it can effectively improve the accuracy of fault detection and reduce the probability of false triggering of the fault protection action.

[0072] In one embodiment, the voltage threshold Vt is proportional to the difference between the target withstand voltage V1 and the rated half-bus voltage V2. The difference between the target withstand voltage V1 and the rated half-bus voltage V2 is the difference obtained by subtracting the rated half-bus voltage V2 from the target withstand voltage V1, i.e., V1-V2. The target withstand voltage V1 can be the smaller of the withstand voltage of the first bus capacitor C1 and the withstand voltage of the second bus capacitor C2. The rated half-bus voltage V2 is half of the rated voltage between the positive DC bus BUS+ and the negative DC bus BUS-, and this rated half-bus voltage V2 is also the rated value of the voltage across each bus capacitor, i.e., the rated voltage of the bus capacitor. The withstand voltage of the first bus capacitor C1 and the second bus capacitor C2 can be equal.

[0073] It is understandable that the withstand voltage of a bus capacitor refers to the upper limit of the voltage that the bus capacitor can withstand; this withstand voltage can also be called the minimum breakdown voltage of the bus capacitor. That is, if the voltage across any bus capacitor exceeds its withstand voltage, the bus capacitor will be at risk of overvoltage breakdown.

[0074] It is also understandable that the withstand voltage of the bus capacitor is greater than its rated voltage, i.e., greater than the rated half-bus voltage V2. When a fault occurs in any phase of the AC / DC conversion circuit, the voltage across the first bus capacitor and / or the second bus capacitor will change compared to the rated half-bus voltage V2. If the changed voltage is less than the target withstand voltage V1, overvoltage breakdown of the bus capacitor can be avoided. That is, for each bus capacitor, if the change in voltage across it from the rated half-bus voltage V2 is less than (V1-V2), overvoltage breakdown of the bus capacitor can be avoided.

[0075] Based on the above analysis, it can be seen that by setting the voltage threshold according to the difference (V1-V2) between the target withstand voltage and the rated half bus voltage, the faults in each phase AC / DC conversion circuit 12 can be accurately detected while ensuring that the bus capacitor does not experience overvoltage breakdown.

[0076] In one embodiment, the voltage threshold Vt can satisfy: Vt / 2 < V1 - V2. The expression for the voltage threshold Vt can also be transformed into: Vt / 2 + V2 < V1, or Vt < 2 × (V1 - V2).

[0077] Understandably, when a fault occurs in any phase of the AC / DC converter circuit, the voltage across one of the first and second bus capacitors will increase compared to the rated half-bus voltage V2, while the voltage across the other bus capacitor will decrease compared to the rated half-bus voltage V2. Based on this, by setting a voltage threshold Vt < 2 × (V1 - V2), it can be ensured that the switch K in the multi-phase AC / DC converter circuit 12 is disconnected in time before the voltage across any bus capacitor reaches the target withstand voltage V1. This ensures that the voltage across each bus capacitor remains within its withstand range, effectively reducing the risk of overvoltage breakdown of the bus capacitors.

[0078] In one embodiment, to further reduce the risk of bus capacitor overvoltage breakdown and improve the reliability of the AC / DC converter, the voltage threshold Vt can satisfy: Vt / 2 < V1 - V2 - V mar The expression for the voltage threshold Vt can also be transformed into: Vt / 2 + V2 < V1 - V mar Among them, V mar This is the preset voltage margin.

[0079] It is understandable that by setting the above voltage margin Vmar This can lower the voltage threshold Vt, thereby effectively ensuring that the voltage across each bus capacitor is within its tolerance range before the switch K in the multiphase AC / DC converter circuit 12 is disconnected. In other words, it effectively reduces the risk of overvoltage breakdown of the bus capacitors.

[0080] It is also understandable that the bus capacitor charging requires a certain amount of time. That is, after the controller 11 detects that the current difference between the first current and the second current in any phase AC / DC converter circuit 12 is greater than or equal to the current threshold, it usually takes a certain amount of time before it detects that the voltage difference between the first half bus voltage and the second half bus voltage is greater than or equal to the voltage threshold. Therefore, after the controller 11 detects that the current difference between the first current and the second current in any phase AC / DC converter circuit 12 is greater than or equal to the current threshold, it can first turn off the switching transistors in each phase AC / DC converter circuit 12. Afterwards, the voltage difference between the first half bus voltage and the second half bus voltage will continue to increase due to uncontrolled rectification. The controller 11 can then turn off the switches K in each phase AC / DC converter circuit 12 when it detects that the voltage difference is greater than or equal to the voltage threshold.

[0081] As mentioned above, after the controller 11 turns off the switches in each phase of the AC / DC converter circuit 12, the current flowing through each switch K in the AC / DC converter gradually decreases. Therefore, in this embodiment, by selecting appropriate components (such as bus capacitors and relays) and designing parameters (such as voltage thresholds), it can be ensured that when the controller 11 detects that the voltage difference between the first half-bus voltage and the second half-bus voltage is greater than or equal to the voltage threshold, the current flowing through the switch K in each phase of the AC / DC converter circuit 12 is less than the maximum breaking current of that switch K. This ensures that the controller 11 can control the switches K in each phase of the AC / DC converter circuit 12 to break normally, thereby ensuring effective isolation of the faulty AC / DC converter.

[0082] Figure 7 This is a schematic diagram of the software protection logic of another AC / DC converter provided in an embodiment of this application. From Figure 7 As can be seen, the controller 11 can continuously monitor the current difference in each phase of the AC / DC conversion circuit 12, and continuously monitor the voltage difference between the first half bus voltage and the second half bus voltage. When the controller 11 detects that the current difference in any phase of the AC / DC conversion circuit 12 is greater than or equal to the current threshold, it can first shut down the switching transistor via software protection. When the voltage difference between the first half bus voltage and the second half bus voltage reaches the voltage threshold, it shuts off the switch K in each phase of the AC / DC conversion circuit 12 to achieve fault isolation.

[0083] In one embodiment, the voltage detection circuit 14 may include a voltage divider circuit and an operational amplifier. The voltage divider circuit is used to divide the voltage of the positive DC bus BUS and the voltage of the negative DC bus BUS-. The operational amplifier is used to acquire the first half-bus voltage between the positive DC bus BUS+ and the bus midpoint O, and the second half-bus voltage between the negative DC bus BUS- and the bus midpoint O, based on the output of the voltage divider circuit.

[0084] In one embodiment, the current detection circuit 13 may include multiple detection sub-circuits corresponding one-to-one with the multiphase AC / DC conversion circuit 12. For example... Figure 4 and Figure 6 As shown, each detection sub-circuit includes a first current sensor R1 and a second current sensor R2. Both the first current sensor R1 and the second current sensor R2 can be shunts.

[0085] Furthermore, refer to Figure 4 and Figure 6 As can be seen, in each phase AC / DC conversion circuit 12, the other end of the inductor L is connected to one end of the first winding T1 through the first current sensor R1, and to one end of the second winding T2 through the second current sensor R2. That is, the first current sensor R1 is connected in series between the inductor L and the first winding T1, and the second current sensor R2 is connected in series between the inductor L and the second winding T2. Correspondingly, each detection sub-circuit in the current detection circuit 13 can sample the autotransformer current before the autotransformer T.

[0086] Since the change in autotransformer current before the autotransformer T is more sensitive, by connecting the current sensor in the current detection circuit 13 in series before the autotransformer T, it can be ensured that the presence of faults in each phase AC / DC conversion circuit 12 can be detected more accurately and quickly based on the autotransformer current detected by the current sensor.

[0087] Of course, the first current sensor R1 and the second current sensor R2 in each detection sub-circuit can also be set in other locations. For example, the first current sensor R1 can be connected in series between the first winding T1 and the first rectifier bridge arm 121, and the second current sensor R2 can be connected in series between the second winding T2 and the second rectifier bridge arm 122. This application embodiment does not limit the location of the current sensors; it only needs to ensure that the current sensors can sample the current flowing through the windings of the autotransformer T.

[0088] It is understandable that the current detection circuit 13 may include other signal processing devices in addition to a current sensor. For example, it may also include an operational amplifier and an analog-to-digital converter (ADC). The operational amplifier is used to amplify the current signal sampled by the current sensor, and the ADC is used to convert the amplified current signal from an analog signal to a digital signal and send the digital signal to the controller 11.

[0089] In one embodiment, such as Figure 6 As shown, each phase AC / DC converter circuit 12 in the AC / DC converter can be a three-state switch cell (TSSC) circuit. The first rectifier bridge arm 121 in this TSSC circuit can include diodes D1, D2, D3, D4, and switches S1 and S2. Diodes D1 to D4 are connected in series between the positive DC bus BUS+ and the negative DC bus BUS-, with the cathode of diode D1 connected to the positive DC bus BUS+ and the anode of diode D4 connected to the negative DC bus BUS-. The series connection point between diodes D2 and D3 is connected to the other end of the first winding T1 in the autotransformer T. Switches S1 and S2 are connected in series, with one end of the series connection between switches S1 and S2 connected to the anode of diode D1 (i.e., the cathode of diode D2) and the other end connected to the cathode of diode D4 (i.e., the anode of diode D3). The series connection point between switches S1 and S2 is connected to the midpoint O of the bus.

[0090] Continue to refer to Figure 6 The second rectifier bridge arm 122 in the TSSC circuit may include diodes D5, D6, D7, and D8, and switching transistors S3 and S4. Diodes D5 to D8 are connected in series between the positive DC bus BUS+ and the negative DC bus BUS-, with the cathode of diode D5 connected to the positive DC bus BUS+ and the anode of diode D8 connected to the negative DC bus BUS-. The series connection point between diodes D6 and D7 is connected to the other end of the second winding T2 in the autotransformer T. Switches S3 and S4 are connected in series, with one end of the series connection between S3 and S4 connected to the anode of diode D5 (i.e., the cathode of diode D6) and the other end connected to the cathode of diode D8 (i.e., the anode of diode D7). The series connection point between switches S3 and S4 is also connected to the bus midpoint O.

[0091] For scenarios where the AC / DC converter includes a three-phase AC / DC conversion circuit 12, refer to... Figure 8 and Figure 9The current detection circuit 13 may include three sets of detection sub-circuits corresponding one-to-one with the three-phase AC / DC converter circuit 12. Each set of detection sub-circuits includes two current sensors, which are used to sample the first current flowing through the first winding T1 and the second current flowing through the second winding T2 in the corresponding phase AC / DC converter circuit 12.

[0092] For example, such as Figure 8 and Figure 9 As shown, a set of detection sub-circuits corresponding to the A-phase AC / DC converter circuit 12 includes current sensors R1a and R2a. A set of detection sub-circuits corresponding to the B-phase AC / DC converter circuit 12 includes current sensors R1b and R2b. A set of detection sub-circuits corresponding to the C-phase AC / DC converter circuit 12 includes current sensors R1c and R2c. Current sensor R1a can be used to sample the first current flowing through the first winding in the A-phase AC / DC converter circuit 12 (also called A1-phase current), and current sensor R2a can be used to sample the second current flowing through the second winding in the A-phase AC / DC converter circuit 12 (also called A2-phase current). Current sensor R1b can be used to sample the first current flowing through the first winding in the B-phase AC / DC converter circuit 12 (also called B1-phase current), and current sensor R2b can be used to sample the second current flowing through the second winding in the B-phase AC / DC converter circuit 12 (also called B2-phase current). The current sensor R1c can be used to sample the first current (also called the C1 phase current) flowing through the first winding in the C-phase AC / DC converter circuit 12, and the current sensor R2c can be used to sample the second current (also called the C2 phase current) flowing through the second winding in the C-phase AC / DC converter circuit 12.

[0093] contrast Figure 8 and Figure 9 It can be seen that the current sensors included in the current detection circuit 13 can be connected in series between the inductor L and the autotransformer T (i.e., connected in series before the autotransformer T), or they can be connected in series between the autotransformer T and the rectifier bridge arm (i.e., connected in series after the autotransformer T).

[0094] The following text is in the format of Figure 8 and Figure 9 Taking the topology shown as an example, we will illustrate the faults that occur in this AC / DC converter.

[0095] refer to Figure 8 Assuming the switching transistor S1 (also called the upper transistor) in the first rectifier bridge arm 121a of the A-phase AC / DC converter circuit 12 is short-circuited, then when the AC current in phase A is positive and the AC currents in phases B and C are both negative, a short circuit will occur in the AC / DC converter. Figure 9 The current path of the short-circuit current is shown. From Figure 9It can be seen that the short-circuit current flows through the switch Ka, inductor La, the first winding of the autotransformer Ta, the diode D1 in the first rectifier bridge arm, and the short-circuit switch S1 in the A-phase AC / DC converter circuit 12, and then flows through the second bus capacitor C2 into the B-phase AC / DC converter circuit 12 and the C-phase AC / DC converter circuit 12 respectively.

[0096] from Figure 8 As can be seen, due to the short circuit of the switching transistor S1 in the first rectifier bridge arm 121a, most of the current flowing from the inductor La will flow to the switching transistor S1 through the first winding T1a of the autotransformer Ta. That is, the first current flowing through the first winding T1a of the autotransformer Ta (i.e., phase A1 current) will be much greater than the second current flowing through the second winding T2a of the autotransformer Ta (i.e., phase A2 current). For example, the second current flowing through the second winding T2a of the autotransformer Ta will be approximately 0. Correspondingly, the controller 11 can detect that the current difference between the first and second currents in the A-phase AC / DC converter circuit 12 is greater than or equal to the difference threshold, and can first turn off each switching transistor in the three-phase AC / DC converter circuit 12. Furthermore, since the A1 phase current charges the second bus capacitor C2, the voltage across the second bus capacitor C2 is much greater than the voltage across the first bus capacitor C1. Therefore, the controller 11 can detect that the voltage difference between the first half-bus voltage and the second half-bus voltage is greater than or equal to a voltage threshold, and can turn off switches Ka, Kb, and Kc in the three-phase AC / DC converter circuit 12. It is understandable that in Figure 8 In the short-circuit scenario shown, the current in phase B1 can be equal to the current in phase B2, and the current in phase C1 can be equal to the current in phase C2.

[0097] refer to Figure 9 Assuming the switching transistor S2 (also called the lower transistor) in the first rectifier bridge arm 121a of the A-phase AC / DC converter circuit 12 is short-circuited, then when the AC current in phase C and phase B is positive and the AC current in phase A is negative, a short circuit will occur in the AC / DC converter. Figure 9 The current path of the short-circuit current is shown. From Figure 9 It can be seen that the short-circuit current flows to the positive DC bus BUS+ after passing through the switch Kc, inductor Lc, autotransformer Tc, and rectifier bridge arm in the C-phase AC / DC converter circuit 12, and then to the positive DC bus BUS+ after passing through the switch Kb, inductor Lb, autotransformer Tb, and rectifier bridge arm in the B-phase AC / DC converter circuit 12. It then flows through the first bus capacitor C1 into the short-circuit switch S2 in the A-phase AC / DC converter circuit 12, and then back to the AC power supply after passing through diode D3, the second winding T2a of the autotransformer Ta, inductor La, and switch Ka.

[0098] from Figure 9 It can be seen that because the switching transistor S2 in the first rectifier bridge arm 121 of the A-phase AC / DC converter circuit 12 is short-circuited, most of the current flowing from the first bus capacitor C1 will flow through the switching transistor S2 to the first winding of the autotransformer Ta. That is, the first current flowing through the first winding T1a of the autotransformer Ta at this time will be much greater than the second current flowing through the second winding of the autotransformer Ta. For example, the current flowing through the second winding of the autotransformer Ta at this time is about 0. Accordingly, the controller 11 can detect that the current difference between the first current and the second current is greater than or equal to the difference threshold, and can first turn off each switching transistor in the three-phase AC / DC converter circuit 12. Furthermore, since the current flowing from the C-phase AC / DC converter circuit 12 charges the first bus capacitor C1, the voltage across the first bus capacitor C1 is much greater than the voltage across the second bus capacitor C2. Therefore, the controller 11 can detect that the voltage difference between the first half-bus voltage and the second half-bus voltage is greater than or equal to a voltage threshold, and can turn off switches Ka, Kb, and Kc in the three-phase AC / DC converter circuit 12. It is understandable that in Figure 9 In the short-circuit scenario shown, the current in phase B1 can be equal to the current in phase B2. Furthermore, the current in phase C1 can be equal to the current in phase C2.

[0099] It is also understandable that, Figure 9 In the short-circuit scenario shown, when phase B AC is positive and phases A and C AC are both negative, the short-circuit current flows from phase B AC / DC converter 12 to the positive DC bus BUS+, and then through the first bus capacitor C1 into phase A AC / DC converter 12. At this time, the currents in phases C1 and C2 can be zero. Alternatively, when phase C AC is positive and phases A and B AC are both negative, the short-circuit current flows from phase C AC / DC converter 12 to the positive DC bus BUS+, and then through the first bus capacitor C1 into phase A AC / DC converter 12. At this time, the currents in phases B1 and B2 can be zero.

[0100] The above explanation uses a short circuit in the upper or lower transistor of the first rectifier bridge arm 121 in phase A AC / DC converter circuit 12 as an example. It can be understood that the path of the short-circuit current when other switching transistors are short-circuited can also be referenced. Figure 8 and Figure 9The relevant descriptions will not be repeated in this embodiment. Furthermore, it is understood that when the upper or lower tube of the first rectifier bridge arm 121 in any phase AC / DC converter circuit 12 is short-circuited, the first current flowing through the first winding T1 of the autotransformer T in that phase AC / DC converter circuit 12 will be much greater than the second current flowing through the second winding T2 of the autotransformer T. Similarly, when the upper or lower tube of the second rectifier bridge arm 122 in any phase AC / DC converter circuit 12 is short-circuited, the second current flowing through the second winding T2 of the autotransformer T in that phase AC / DC converter circuit 12 will be much greater than the first current flowing through the first winding T1 of the autotransformer T. Accordingly, the controller 11 can determine that a fault (e.g., a short-circuit fault) exists in the phase AC / DC converter circuit 12 based on the current difference between the first and second currents in any phase AC / DC converter circuit 12 being greater than or equal to a current threshold. Furthermore, the controller 11 can first turn off the switching transistors in each phase AC / DC conversion circuit 12, and then turn off the switches K in each phase AC / DC conversion circuit 12.

[0101] Understandably, in scenarios where AC / DC converters are used in non-isolated architectures, if a short-circuit fault occurs in any AC / DC converter and is not isolated, the fault will propagate to other AC / DC converters. For example, refer to... Figure 10 , Figure 10 Taking phase A as positive and phases B and C as negative as an example, the current circulation path between modules (i.e., between different AC / DC converters) is shown. From Figure 10 As shown by the dashed arrows, in a non-isolated architecture, the current paths within a module, between modules, and on the mains side form a current loop. If a fault (e.g., a short-circuit fault) occurs in any AC / DC converter, the fault current in that AC / DC converter will propagate along this current loop, causing damage to devices in other AC / DC converters, and even causing the system (such as a charging device) to crash.

[0102] In this embodiment of the application, since the controller 11 in the AC / DC converter can turn off the switch K in each phase AC / DC converter 12 after detecting a fault in any phase AC / DC converter 12, the faulty AC / DC converter 12 can be isolated from the AC power supply, thereby effectively isolating the faulty AC / DC converter 12 from other AC / DC converters in the system (such as charging equipment).

[0103] In addition, refer to Figures 6 to 10As can be seen, in the solution provided by the embodiments of this application, the AC / DC conversion circuit 12 adopts the TSSC topology. Since the diodes D1, D4, D5 and D8 in the TSSC topology have the function of reverse top, it can ensure that there is no circulating current between the faulty AC / DC converter and the other normal AC / DC converters, thus effectively preventing the spread of faults.

[0104] It is also understandable that Figure 8 and Figure 9 In this context, PGND refers to the power ground.

[0105] In summary, this application provides an AC / DC converter including a controller and a multi-phase AC / DC conversion circuit. In each phase of the AC / DC conversion circuit, the current flowing through the first winding of the autotransformer is a first current, and the current flowing through the second winding of the autotransformer is a second current. The controller can determine that a fault exists in the AC / DC conversion circuit of any phase when the difference between the first and second currents in any phase is greater than or equal to a current threshold, and then shuts off the switches in each phase of the AC / DC conversion circuit. This disconnects the faulty AC / DC converter from the AC power supply, thereby isolating the faulty AC / DC converter from other normal AC / DC converters and preventing the fault from spreading.

[0106] Furthermore, the solution provided in this application can detect faults based on the current flowing through the autotransformer and isolate faults by turning off the switches in the AC / DC conversion circuit. Therefore, there is no need to add additional power switching devices to the AC / DC converter, effectively avoiding increased structural complexity and hardware costs. Moreover, compared to fuse-based solutions, the solution provided in this application does not require coordination between individual AC / DC converters for fault isolation, resulting in lower implementation complexity and lower requirements for the system's current sharing coefficient.

[0107] This application also provides a charging device, which can be a charging pile. For example... Figure 1 and Figure 2As shown, the charging device includes an AC / DC converter 10, a DC / DC converter 20, and a charging gun 30 as provided in the above embodiment. The output terminal (i.e., DC terminal) of the AC / DC converter 10 is connected to the charging gun 30 via the DC / DC converter 20. The input terminal (i.e., AC terminal) of the AC / DC converter 10 is used to connect to an AC power source, and the AC / DC converter 10 converts the AC power provided by the AC power source into DC power. The DC / DC converter 20 performs voltage conversion on the DC power and outputs it to the charging gun 30, thereby charging the electric vehicle connected to the charging gun 30.

[0108] In one embodiment, such as Figure 1 and Figure 2 As shown, the charging device may include multiple AC / DC converters 10. And, as... Figure 1 As shown, the outputs of the plurality of AC / DC converters 10 can be connected in parallel to the DC bus. One end of the plurality of DC / DC converters 20 is also connected in parallel to the DC bus. Alternatively, as... Figure 2 As shown, the output of each AC / DC converter 10 can be directly connected to one end of a DC / DC converter 20, meaning the AC / DC converter 10 does not need to be connected to the DC / DC converter 20 via a DC bus. Alternatively, the AC / DC converter 10 can also integrate the functions of a DC / DC converter, meaning it can not only perform AC-to-DC conversion but also DC voltage conversion. Correspondingly, the charging device does not require a separate DC / DC converter 20.

[0109] In one embodiment, reference continues... Figure 1 and Figure 2 The charging device may also include a power distribution module 40. One end of the power distribution module 40 is connected to the other end of the plurality of DC / DC converters 20, and the other end of the power distribution module 40 is connected to the plurality of charging guns 30.

[0110] It is understood that the solutions provided in this application can be applied not only to charging equipment (such as charging piles) but also to other fields, such as inverters in photovoltaic systems or energy storage converters in energy storage systems.

[0111] In the embodiments of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The term "at least one" refers to one or more, and "multiple" refers to two or more.

[0112] In the embodiments of this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0113] The above description is merely an optional implementation of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An AC / DC converter, characterized in that, The AC / DC converter includes: a controller and a multi-phase AC / DC conversion circuit; each phase of the AC / DC conversion circuit includes: a switch, an inductor, an autotransformer, a first rectifier bridge arm and a second rectifier bridge arm; the autotransformer includes a first winding and a second winding. Wherein, one end of the switch is used to connect to an AC power source, the other end of the switch is connected to one end of the inductor, the other end of the inductor is connected to one end of the first winding and one end of the second winding respectively, the other end of the first winding is connected to the first rectifier bridge arm, and the other end of the second winding is connected to the second rectifier bridge arm; The controller is configured to turn off the switch in the multi-phase AC / DC conversion circuit when the current difference between the first current and the second current in any phase of the AC / DC conversion circuit is greater than or equal to a current threshold. Wherein, the first current is the current flowing through the first winding of the AC / DC converter circuit in any phase, and the second current is the current flowing through the second winding of the AC / DC converter circuit in any phase.

2. The AC / DC converter according to claim 1, characterized in that, When the current threshold is greater than or equal to 1 / 10 of the current flowing through the autotransformer when the AC / DC converter outputs its rated power, the current flowing through the autotransformer is the sum of the currents flowing through the first winding and the second winding.

3. The AC / DC converter according to claim 1 or 2, characterized in that, Each of the first rectifier bridge arm and the second rectifier bridge arm includes at least one switching transistor; The controller is configured to first turn off the switching transistor in the multiphase AC / DC conversion circuit, and then turn off the switch in the multiphase AC / DC conversion circuit.

4. The AC / DC converter according to claim 3, characterized in that, The controller is configured to turn off the switch in the multiphase AC / DC converter circuit when the off-time of the switch reaches a time threshold.

5. The AC / DC converter according to claim 4, characterized in that, The duration threshold is on the order of microseconds, milliseconds, or seconds.

6. The AC / DC converter according to claim 3, characterized in that, The controller is configured to, after turning off the switching transistors in the multiphase AC / DC converter circuit, turn off the switches in the multiphase AC / DC converter circuit when the current flowing through any one of the switches in the AC / DC converter circuit is less than the maximum breaking current of the switch.

7. The AC / DC converter according to claim 3, characterized in that, The controller is configured to turn off the switches in the multiphase AC / DC converter circuit after turning off the switches in the multiphase AC / DC converter circuit, provided that the current flowing through each switch in the AC / DC converter circuit is less than the maximum breaking current of the switch.

8. The AC / DC converter according to any one of claims 1 to 3, characterized in that, The AC / DC converter also includes: a positive DC bus, a negative DC bus, a first bus capacitor, and a second bus capacitor; Each of the first rectifier bridge arm and the second rectifier bridge arm is also connected to the positive DC bus and the negative DC bus respectively, and the first bus capacitor and the second bus capacitor are connected in series between the positive DC bus and the negative DC bus; The controller is configured to turn off the switch in the multi-phase AC / DC conversion circuit when the current difference between the first current and the second current in any phase of the AC / DC conversion circuit is greater than or equal to the current threshold, and the voltage difference between the first half-bus voltage and the second half-bus voltage is greater than or equal to the voltage threshold. Wherein, the first half-bus voltage is the voltage between the positive DC bus and the bus midpoint, the second half-bus voltage is the voltage between the negative DC bus and the bus midpoint, and the bus midpoint is the series node between the first bus capacitor and the second bus capacitor.

9. The AC / DC converter according to claim 8, characterized in that, The voltage threshold Vt satisfies: Vt / 2 < V1 - V2; Wherein, V1 is the smaller of the withstand voltage of the first bus capacitor and the withstand voltage of the second bus capacitor, and V2 is the rated half bus voltage, which is half of the rated voltage between the positive DC bus and the negative DC bus.

10. A charging device, characterized in that, The charging device includes: an AC / DC converter, a DC / DC converter, and a charging gun as described in any one of claims 1 to 9, wherein the output terminal of the AC / DC converter is connected to the charging gun via the DC / DC converter.

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