Converter module, traction converter system and control method thereof

Abstract

The application provides a variable current module, a traction variable current system and a control method thereof. The variable current module is applied to a traction variable current system in which multiple variable current modules are connected in parallel. The traction variable current system comprises a positive direct current bus, a negative direct current bus and a power grid. The variable current module comprises an inverter bridge circuit having a direct current end and an alternating current end. The direct current end is used for being connected with the positive direct current bus and the negative direct current bus. The alternating current end is used for being connected with the power grid. A first fuse is arranged between the direct current end of the inverter bridge circuit and the positive direct current bus or the negative direct current bus. A midpoint interconnection circuit has a first end connected with a midpoint of the inverter bridge circuit. Second ends of the midpoint interconnection circuits in the multiple variable current modules are connected in parallel. When a half bus short circuit occurs in the inverter bridge circuit of a first variable current module in the multiple variable current modules, a first midpoint interconnection circuit corresponding to the first variable current module is disconnected, so that the first variable current module is decoupled from the midpoint of other variable current modules. The first variable current module is any one of the multiple variable current modules.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of rail transit technology, and in particular to a variable current module, a traction variable current system and a control method thereof. BACKGROUND

[0002] In order to realize the bidirectional flow of energy between the DC side and the AC side of the rail transit power supply system and provide stable DC voltage, a bidirectional traction power supply device is introduced into the rail transit power supply system. The traction power supply device includes a bidirectional traction variable current circuit, and the variable current circuit includes a plurality of variable current modules connected in parallel.

[0003] In the above variable current circuit, if the midpoint potentials of adjacent first and second modules are inconsistent, a potential difference will be generated between the midpoints of different modules. The existence of the potential difference will generate a current flowing from the midpoint of the first module to the midpoint of the second module through the AC side, i.e. inter-module circulating current. The circulating current will increase the loss of the converter and reduce the efficiency of the system. At the same time, excessive circulating current may cause overcurrent of the switch tube and affect the normal operation of the system. In related technologies, in order to suppress the circulating current between different modules, the midpoints of different modules can be directly connected to keep the midpoint potentials of different modules consistent, thereby achieving the purpose of suppressing the circulating current.

[0004] However, during the operation of the bidirectional traction variable current circuit, the positive half bus or the negative half bus of the DC side may be short-circuited due to insulation aging, overvoltage breakdown, line fault, load imbalance or load mutation. If half bus failure occurs in one of the modules, the other modules of the entire system will face the risk of failure, which will not be applicable to the rail transit traction system requiring high reliability. SUMMARY

[0005] The present application mainly provides a variable current module, a traction variable current system and a control method thereof. The technical solution of the present application is implemented as follows:

[0006] In a first aspect, a variable current module is provided for a traction variable current system with multiple variable current modules in parallel, the traction variable current system comprising a positive direct current bus, a negative direct current bus and a power grid; the variable current module comprising: an inverter bridge circuit having a direct current end and an alternating current end, the direct current end being configured to be connected to the positive direct current bus and the negative direct current bus, and the alternating current end being configured to be connected to the power grid; a first fuse arranged between the direct current end of the inverter bridge circuit and the positive direct current bus or the negative direct current bus; a midpoint interconnection circuit, a first end of the midpoint interconnection circuit being connected to a midpoint of the inverter bridge circuit; second ends of the midpoint interconnection circuits in the multiple variable current modules being connected in parallel; when a half bus short circuit occurs in the inverter bridge circuit of a first variable current module in the multiple variable current modules, a first midpoint interconnection circuit corresponding to the first variable current module is disconnected, so that the first variable current module is decoupled from the midpoints of other variable current modules, and the first variable current module is any one of the multiple variable current modules.

[0007] According to the above technical means, when the midpoint potential of the first variable current module changes by more than a threshold value or the midpoint current exceeds a threshold value, the midpoint interconnection circuit can quickly disconnect the midpoint of the module from the connection with other modules, so that the midpoint of the module is decoupled from the midpoints of other modules, thereby avoiding the propagation of fault current to other modules.

[0008] In some embodiments, the midpoint interconnection circuit comprises a second fuse; when a half bus short circuit occurs in the inverter bridge circuit of the first variable current module, the second fuse is fused to decouple the first variable current module; the fuse current of the second fuse is less than the convergence current of the midpoint of the inverter bridge circuit of the first variable current module; wherein the convergence current is the current flowing from the midpoint of the inverter bridge circuit of the other variable current modules to the midpoint of the inverter bridge circuit of the first variable current module when a half bus short circuit occurs in the inverter bridge circuit of the first variable current module.

[0009] According to the above technical means, by arranging a second fuse in the midpoint interconnection circuit and setting the melting point current of the second fuse to be lower than the convergence current, the rapid decoupling of the faulty module can be achieved, thereby preventing the propagation of faults to other modules, and further improving the operation stability and safety of the entire rail traction system.

[0010] In some embodiments, the midpoint interconnection circuit comprises a switching circuit; when a half bus short circuit does not occur in the inverter bridge circuit of the first variable current module, the switching circuit is turned on to connect the midpoints of the inverter bridge circuits of the multiple variable current modules; when a half bus short circuit occurs in the inverter bridge circuit of the first variable current module, the corresponding first switching circuit in the first variable current module is disconnected to decouple the first variable current module.

[0011] According to the above technical means, the controllable switch circuit is arranged to replace the traditional midpoint direct connection mode, so that the midpoint potential balance can be realized in the normal operation of the system, and the fault module can be quickly isolated in the case of local fault. Thus, the operation of the whole system can be avoided from being affected by the failure of a single module.

[0012] In some embodiments, the switch circuit includes a controllable switch; the current conversion module further includes a control circuit connected with the controllable switch in the plurality of current conversion modules, and the control circuit is configured to: control the controllable switch in the plurality of current conversion modules to be turned on when the inverter bridge circuit of the first current conversion module does not occur half bus short circuit; control the first controllable switch corresponding to the first current conversion module to be turned off when the inverter bridge circuit of the first current conversion module occurs half bus short circuit, so as to decouple the first current conversion module; or the switch circuit includes an active bridge circuit, the active bridge circuit includes two IGBT modules connected in anti-series, and the IGBT module includes a first switch tube and an anti-parallel diode; the current conversion module further includes a control circuit connected with the gate of the first switch tube, and the control circuit is configured to: control the first switch tube to be turned on when the inverter bridge circuit of the first current conversion module does not occur half bus short circuit.

[0013] According to the above technical means, by controlling the control circuit to switch the conduction state of the controllable switch or the IGBT module according to whether the half bus short circuit occurs, the system efficiency can be maintained in the normal operation, and the influence path of the fault module can be quickly cut off in the abnormal situation.

[0014] In some embodiments, the current conversion module further includes a plurality of third fuses respectively arranged between the AC end of the inverter bridge circuit and the multi-phase of the power grid; when the inverter bridge circuit of the first current conversion module occurs half bus short circuit, one or more of the plurality of third fuses are fused, so as to decouple the AC end of the first current conversion module from the AC end of the other current conversion modules.

[0015] According to the above technical means, since the third fuses exist, when the half bus short circuit occurs, the third fuses connected with the AC end of the first converter are quickly fused, the connection between the short circuit point in the first current conversion module and the AC bus is cut off, so as to decouple the AC end of the first current conversion module from the AC end of the other current conversion modules. Thus, the influence of the short circuit current on the other switch tubes in the first current conversion module and the other current conversion modules can be avoided, and the normal work of the other modules can be ensured.

[0016] In a second aspect, a traction converter system is provided, comprising a plurality of converter modules connected in parallel, a controller, a positive DC bus, a negative DC bus and a power grid; each of the converter modules comprises: an inverter bridge circuit having a DC end and an AC end, the DC end being connected to the positive DC bus and the negative DC bus, the AC end being connected to the power grid; a first fuse arranged between the DC end of the inverter bridge circuit and the positive DC bus or the negative DC bus; a midpoint interconnection circuit, a first end of the midpoint interconnection circuit being connected to a midpoint of the inverter bridge circuit; second ends of the midpoint interconnection circuits of the plurality of converter modules being connected in parallel; when a half bus short circuit occurs in the inverter bridge circuit of a first converter module of the plurality of converter modules, a first midpoint interconnection circuit corresponding to the first converter module is disconnected, so that the first converter module is decoupled from the midpoints of the other converter modules; the controller is connected to the plurality of converter modules and configured to control the inverter bridge circuits of the plurality of converter modules to perform bidirectional conversion between the DC end and the AC end, so as to supply power to a DC load through the positive DC bus and the negative DC bus, or to convert power generated by the DC load to the power grid.

[0017] In some embodiments, the midpoint interconnection circuit comprises a second fuse; when the half bus short circuit occurs in the inverter bridge circuit of the first converter module, the second fuse is fused to decouple the first converter module; a fuse current of the second fuse is smaller than a convergence current of the midpoint of the inverter bridge circuit of the first converter module; wherein the convergence current is a current flowing from the midpoint of the inverter bridge circuit of the other converter modules to the midpoint of the inverter bridge circuit of the first converter module when the half bus short circuit occurs in the inverter bridge circuit of the first converter module.

[0018] In some embodiments, the midpoint interconnection circuit comprises a switching circuit; the switching circuit comprises controllable switches; the controller is connected with the controllable switches in the plurality of variable current modules, and the controller is configured to: control the controllable switches in the plurality of variable current modules to be turned on when the inverter bridge circuit of the first variable current module does not occur half bus short circuit; control the first controllable switch corresponding to the first variable current module to be turned off when the inverter bridge circuit of the first variable current module occurs half bus short circuit, so as to decouple the first variable current module; or, the switching circuit comprises an active bridge circuit, the active bridge circuit comprises two IGBT modules connected in anti-series, the IGBT module comprises a first switch tube and an anti-parallel diode; the controller is connected with the gate of the first switch tube, and the controller is configured to: control the two IGBT modules to be turned on when the inverter bridge circuit of the first variable current module does not occur half bus short circuit; control the two IGBT modules in the active bridge circuit corresponding to the first variable current module to be turned off when the inverter bridge circuit of the first variable current module occurs half bus short circuit, so as to decouple the first variable current module.

[0019] In a third aspect, a control method of a traction variable current system is provided, the traction variable current system comprising a plurality of variable current modules connected in parallel, a positive direct current bus, a negative direct current bus and a power grid; the variable current module comprising: an inverter bridge circuit having a direct current end and an alternating current end, the direct current end being connected with the positive direct current bus and the negative direct current bus, and the alternating current end being used for connecting with the power grid; a first fuse being arranged between the direct current end of the inverter bridge circuit and the positive direct current bus or the negative direct current bus; a midpoint interconnection circuit, a first end of the midpoint interconnection circuit being connected with a midpoint of the inverter bridge circuit; a second end of the midpoint interconnection circuit in the plurality of variable current modules being connected in parallel; when an inverter bridge circuit of a first variable current module in the plurality of variable current modules occurs half bus short circuit, a first midpoint interconnection circuit corresponding to the first variable current module is turned off, so as to decouple the midpoint of the first variable current module and other variable current modules, the first variable current module being any one of the plurality of variable current modules; the method comprising: controlling the inverter bridge circuit in the plurality of variable current modules to perform bidirectional variable current between the direct current end and the alternating current end, so as to supply power to a direct current load through the positive direct current bus and the negative direct current bus, or inversely variable the electric energy generated by the direct current load to the power grid.

[0020] In some embodiments, the midpoint interconnection circuit comprises a switching circuit, and the switching circuit comprises controllable switches; the method comprises: when the half bus short circuit does not occur in the inverter bridge circuit of the first current conversion module, controlling the controllable switches in the plurality of current conversion modules to be turned on; when the half bus short circuit occurs in the inverter bridge circuit of the first current conversion module, controlling the first controllable switch corresponding to the first current conversion module to be turned off, so that the first current conversion module is decoupled; or the switching circuit comprises an active bridge circuit, and the active bridge circuit comprises two IGBT modules connected in anti-series, and the IGBT module comprises a first switch tube and an anti-parallel diode; the method comprises: when the half bus short circuit does not occur in the inverter bridge circuit of the first current conversion module, controlling the two IGBT modules to be turned on; when the half bus short circuit occurs in the inverter bridge circuit of the first current conversion module, controlling the two IGBT modules in the active bridge circuit corresponding to the first current conversion module to be turned off, so that the first current conversion module is decoupled. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 A schematic diagram of a rail transit traction system to which the technical scheme provided by the embodiments of the present application is applied;

[0022] Figure 2 A schematic diagram of a bidirectional traction current conversion circuit in a rail transit vehicle in Figure 1

[0023] Figure 3 A schematic diagram of an ANPC type three-level current conversion circuit;

[0024] Figure 4 A schematic diagram of a bidirectional traction current conversion circuit;

[0025] Figure 5 A schematic circuit diagram of a traction current conversion system of a current conversion module to which the embodiments of the present application are applied;

[0026] Figure 6 A circuit topology of a traction current conversion system provided by the embodiments of the present application Figure 1 ;

[0027] Figure 7 A schematic diagram of a traction current conversion system provided by the embodiments of the present application Figure 1 ;

[0028] Figure 8 A circuit topology of a traction current conversion system provided by the embodiments of the present application Figure 2 ;

[0029] Figure 9 A schematic diagram of a traction current conversion system provided by the embodiments of the present application Figure 2 ;

[0030] Figure 10 ​A schematic diagram of a traction conversion system provided by an embodiment of the present application Figure 3 ;

[0031] Figure 11 A circuit topology of a traction conversion system provided by an embodiment of the present application Figure 3 ;

[0032] Figure 12 A schematic diagram of a traction conversion system provided by an embodiment of the present application Figure 4 ;

[0033] Figure 13 A circuit topology of a traction conversion system provided by an embodiment of the present application Figure 4 ;

[0034] Figure 14 A schematic structural diagram of a traction conversion system provided by an embodiment of the present application

[0035] Figure 15 A schematic flow chart of a control method of a traction conversion system provided by an embodiment of the present application. DETAILED DESCRIPTION

[0036] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application.

[0037] It should be noted that the "connection" in the embodiments of the present application refers to electrical connection, and the connection between two electrical elements can be direct or indirect connection between the two electrical elements. For example, A is connected to B, which can be direct connection between A and B, or indirect connection between A and B through one or more other electrical elements. For example, A is connected to B, which can be direct connection between A and C, direct connection between C and B, and connection between A and B through C.

[0038] In addition, the reference "one embodiment" or "some embodiments" and the like described in the specification means that the specific features, structures or characteristics described in connection with the embodiment are included in one or more embodiments of the present application. Therefore, the statements "in one embodiment", "in some embodiments", "in other some embodiments", "in further some embodiments" and the like appearing in different parts of the specification are not necessarily all referring to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized. The terms "include", "contain", "have" and their variants mean "include but not limited to", unless otherwise specifically emphasized.

[0039] In this application, the ordinal numbers such as "first" and "second" are used to distinguish multiple objects, but are not used to limit the order, sequence, priority or importance of multiple objects.

[0040] Currently, most rail transit power supply systems use unidirectional rectifiers to convert three-phase AC power into DC power to provide DC power to rail transit vehicles. To achieve bidirectional energy flow between the DC and AC sides of the rail transit power supply system and provide a stable DC contact voltage, a rechargeable bidirectional traction power supply device has been introduced into this system. The AC side of the rechargeable bidirectional traction power supply device is connected to the AC power grid, and the DC side is connected to the DC traction network. When the rail transit vehicle is in traction mode, the power supply device operates in rectification mode, converting the AC power from the AC power grid into DC power to supply the DC traction network. When the rail transit vehicle is in braking mode, the power supply device operates in inverter mode, converting the DC power from the DC traction network back into AC power and feeding it back to the AC power grid.

[0041] Figure 1 This is a schematic diagram of a rail transit traction system applying the technical solutions provided in the embodiments of this application.

[0042] like Figure 1 As shown, the rail transit traction system 100 includes an AC power grid 110, a bidirectional traction converter 120, and a traction motor 130.

[0043] Figure 1 The diagram also shows a track 140 and a vehicle 150 in a rail transit system. A DC contact network 160 is installed above the track. A bidirectional traction converter 120 is positioned between the AC power grid 110 and the DC contact network 160 to rectify the AC power supplied by the AC power grid 110, providing DC power suitable for the traction motor 130 to the DC contact network 160. The vehicle 150 can obtain DC power through its pantograph 151. Furthermore, when the vehicle 150 is braking, the traction motor 130 generates DC power through electromagnetic induction and transmits it to the DC contact network 160. At this time, the bidirectional traction converter 120 inverts this DC power, feeding it back to the AC power grid 110.

[0044] Figure 2 yes Figure 1 A schematic diagram of the bidirectional traction converter 120 is shown below. Figure 2 As shown, the bidirectional traction converter 120 includes at least one bidirectional converter module 121. The AC terminal of the bidirectional converter module 121 is connected to the AC bus, and the DC terminal is connected to the DC load.

[0045] When the bidirectional traction converter 120 comprises at least two bidirectional converter modules 121, the bidirectional converter modules are connected in parallel. Each bidirectional converter module can work simultaneously, or part of the bidirectional converter modules work simultaneously, and the remaining part of the bidirectional converter modules serve as backup, and when the working bidirectional converter module fails, the backup bidirectional converter module replaces the failed bidirectional converter module. For example, if the bidirectional traction converter comprises two bidirectional converter modules, the two bidirectional converter modules can work simultaneously, or one of the bidirectional converter modules works, and the other bidirectional converter module serves as backup, and when the working bidirectional converter module fails, the backup bidirectional converter module replaces the failed bidirectional converter module to work.

[0046] The bidirectional converter module can be any one of a three-level converter, an interleaved parallel converter, a cascaded H-bridge converter, and the like. The active neutral-point-clamped (ANPC) three-level converter is a topology developed on the basis of a conventional neutral-point-clamped (NPC) three-level converter, and more flexible neutral-point potential control and lower switching loss are achieved by introducing active switching devices.

[0047] The ANPC three-level converter is suitable for working in an inverter mode and / or a rectifier mode, and comprises a control circuit and a main circuit. The main circuit comprises an upper bridge arm composed of a first switching tube T1, a second switching tube T2, and a fifth switching tube T5, and a lower bridge arm composed of a third switching tube T3, a fourth switching tube T4, and a sixth switching tube T6. The first switching tube T1 and the fourth switching tube T4 are respectively connected to a positive terminal BUS+ and a negative terminal BUS- of a direct-current network, a connection point of the fifth switching tube T5 and the sixth switching tube T6 is connected to a neutral terminal of the direct-current network, and a connection point of the second switching tube T2 and the third switching tube T3 is connected to an alternating-current network.

[0048] As a possible implementation, the first switching tube T1 and the fifth switching tube T5 are packaged in the same switching tube packaging module, the fourth switching tube T4 and the sixth switching tube T6 are packaged in the same switching tube packaging module, and the second switching tube T2 and the third switching tube T3 are packaged in the same switching tube packaging module.

[0049] The control circuit is used to control the on-off of each switching tube in the main circuit, including: when the alternating-current network is an input terminal, controlling the conduction and turn-off of the switching device, so that the input alternating-current voltage is connected to the positive bus, the negative bus, and the neutral point at different times, to realize the rectification of the alternating-current voltage; and when the direct-current network is an input terminal, controlling the conduction and turn-off of the switching device, to convert the direct-current voltage into a three-phase alternating-current voltage, to form a required alternating-current waveform.

[0050] InFigure 3 In the ANPC type three-level converter shown, each switching transistor is a controllable switching transistor with an anti-parallel diode, and the diodes corresponding to each switching transistor are represented by D1, D2, D3, D4, D5 and D6.

[0051] In practical applications, pulse width modulation (PWM) technology is usually used to control the on-time and off-time of the switching transistor, and the magnitude of the output DC voltage is controlled by adjusting the duty cycle of the PWM signal.

[0052] In the case where the aforementioned AC power grid is a three-phase AC power grid, such as Figure 4 As shown, each bidirectional converter module may include three ANPC type three-level converters connected in parallel. The DC terminals of the three ANPC type three-level converters are all connected to the DC bus, and the AC terminals are respectively connected to different phases of the three-phase AC power grid. By controlling the on and off phases of multiple switching transistors in the three ANPC type three-level converters, the conversion between DC power and three-phase AC power can be realized.

[0053] In the aforementioned converter circuit, when multiple ANPC three-level converters operate in parallel, differences in parameters between ANPC modules, differences in the on-state voltage drop of switching transistors, and load imbalance can lead to differences in the output voltage amplitude, phase, and frequency among the converters. This, in turn, generates circulating currents between the parallel branches. Circulating currents refer to currents that flow between the parallel converters without passing through the load. Circulating currents increase converter losses and reduce system efficiency. Furthermore, excessive circulating currents can cause overcurrent in the switching transistors, affecting the normal operation of the system and potentially damaging the converters.

[0054] Secondly, when a parallel system uses a three-level circuit, in order to ensure power quality and efficiency, it is necessary to keep the midpoint potential of each three-level circuit consistent. For example, if the midpoint potentials of adjacent first and second modules are inconsistent, that is, there is a potential difference between the midpoints of different modules, the existence of this potential difference will generate a current flowing from the midpoint of the first module through the AC side to the midpoint of the second module. This current is the aforementioned circulating current.

[0055] In related technologies, to suppress circulating current between different modules, the midpoints of different modules can be directly connected to keep the midpoint potentials of different modules consistent, thereby achieving the purpose of suppressing circulating current. However, during the operation of a bidirectional traction converter circuit, short circuits may occur on the positive or negative half-busbar of the DC side due to reasons such as insulation aging, overvoltage breakdown, line faults, load imbalance, or sudden load changes.

[0056] by Figure 4The circuit shown is an example, each bidirectional current conversion module further comprises a first capacitor C1 and a second capacitor C2, which are respectively arranged between the direct current positive bus and the midpoint and the direct current negative bus and the midpoint. Taking the first bidirectional current conversion module in the figure as an example, when the first capacitor C1 is short-circuited, at this time, the first module is short-circuited on the positive half bus, at this time, the midpoint potential of the first module is pulled up to be consistent with the potential of the positive direct current bus, and the potential difference between the negative direct current bus and the midpoint is also pulled up.

[0057] When the midpoint potential of the first module is raised, due to the mutual connection of the midpoints of the modules, the midpoint potentials of other modules will also be raised. For each module, since the potential difference between the negative direct current bus and the midpoint is pulled up, if the potential difference is greater than the withstand voltage limit of the second capacitor or the third switch tube T3, the fourth switch tube T4 and the sixth switch tube T6 in the lower bridge arm, the above-mentioned devices will be broken down, resulting in failure of the entire module.

[0058] That is, in the circuit shown, if one of the modules fails on the half bus, the other modules in the entire system will face the risk of failure due to the direct connection of the midpoints, so it cannot be applied to the rail transit traction system which requires high reliability. Figure 4 In the circuit shown, due to the direct connection of the midpoints, if one of the modules fails on the half bus, the other modules in the entire system will face the risk of failure, so it cannot be applied to the rail transit traction system which requires high reliability.

[0059] In view of the above problems, the embodiment of the present application provides a current conversion module, a traction current conversion system and a control method thereof. The technical solutions of the embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0060] The current conversion circuit provided by the embodiment of the present application maintains the balance of the midpoint potentials of the modules during normal operation by arranging the midpoint interconnection circuit between the midpoints of the modules, and quickly disconnects the fault module when a half bus short circuit fault occurs, so as to cause the fault to spread to other modules, thereby improving the safety and reliability of the system.

[0061] Figure 5 is a schematic circuit diagram of a traction current conversion system 500 applying the current conversion module provided by the embodiment of the present application. The traction current conversion system 500 comprises a plurality of current conversion modules 510, a positive direct current bus BUS+, a negative direct current bus BUS- and a power grid 520.

[0062] The plurality of current conversion modules 510 in the traction current conversion system 500 are connected in parallel with each other, and each current conversion module 510 comprises an inverter bridge circuit 511, a first fuse F1 and a midpoint interconnection circuit 512.

[0063] The inverter bridge circuit 511 is a core component of the converter module 510, which can work in inverting or rectifying mode. For example, when applied to the aforementioned rail transit vehicle, in the vehicle braking state, the inverter bridge circuit can work in inverting mode, so as to convert the direct current generated by the motor idling into alternating current and feedback to the power grid 520; in the normal running state of the vehicle, the inverter bridge circuit is in rectifying mode, which is used to convert the alternating current provided by the power grid 520 into direct current to drive the motor and other direct current loads.

[0064] In the embodiments of the present application, the inverter bridge circuit 511 has a direct current end and an alternating current end, wherein the direct current end is used to connect with the positive direct current bus BUS+ and the negative direct current bus BUS-, and the alternating current end is used to connect with the alternating current grid.

[0065] The embodiments of the present application do not make specific limitations on the form of the inverter bridge circuit, which may, for example, be a full-bridge inverter circuit, a three-phase inverter circuit, a multi-level inverter circuit, etc.

[0066] For example, as shown in Figure 6 Each inverter bridge circuit in the traction converter system includes three ANPC type three-level converters connected in parallel with each other, the direct current positive and negative ends of the three ANPC type three-level converters are connected with BUS+ and BUS- respectively, the direct current ends are connected with three phases of the three-phase alternating current grid respectively, and the midpoints of the three ANPC type three-level converters are connected with each other.

[0067] The first fuse F1 is arranged between the direct current end of the inverter bridge circuit and the positive or negative direct current bus, and can be fused when the current exceeds the limit that it can withstand, so as to cut off the connection between the module and the positive direct current bus. For example, in the circuit shown in Figure 6 When the inverter bridge circuit of the first converter module in the plurality of converter modules occurs positive half bus short circuit, the first fuse F1 is fused to decouple the positive direct current end of the first converter module from other converter modules. The above-mentioned first converter module is any one of the plurality of converter modules.

[0068] Referring to Figure 5 and Figure 6 The first end of the midpoint interconnection circuit 512 in each converter module 510 is connected with the midpoint of the inverter bridge circuit 511, and the second ends of the midpoint interconnection circuits 512 in the plurality of converter modules 510 are connected in parallel.

[0069] When the inverter bridge circuit of the first converter module in the plurality of converter modules occurs half bus short circuit, the first midpoint interconnection circuit corresponding to the first converter module is disconnected to decouple the midpoint of the first converter module from other converter modules.

[0070] In some embodiments of the present application, as shown in Figure 6As shown, the current conversion module further comprises a positive bus capacitor C3 and a negative bus capacitor C4, which are respectively arranged between the positive DC bus and the negative DC bus and the midpoint of the inverter bridge circuit; the first end of the first fuse F1 is connected with the positive DC bus, and the other end is connected with one end of the positive bus capacitor C3 away from the midpoint.

[0071] The following will be described in combination with Figure 6 The above process will be further described, taking the first current conversion module as an example. Figure 6 As shown in the first current conversion module, when the positive half bus of the first current conversion module is short-circuited, the positive DC bus is directly conducted with the midpoint, forming a low-impedance path, and the midpoint potential jumps to the same potential as the positive DC bus. At the moment of short-circuit, the current of the positive DC bus rises rapidly, which may reach 10-20 times of the normal current value. When the current exceeds the minimum melting current of the first fuse F1, the fuse of the first fuse F1 melts and heats, cutting off the connection between the DC end of the first current conversion module and the DC bus, thereby decoupling the first current conversion module and other modules, and avoiding the influence of the failed module on the normal work of other modules.

[0072] Since the midpoints of the modules are connected through the aforementioned midpoint interconnection circuit, when the positive half bus of the first current conversion module is short-circuited, the midpoint potential of the first current conversion module will be higher than the midpoint potentials of other current conversion modules. At this time, a current will flow from the first current conversion module to other modules, which will affect the work of other modules.

[0073] In the technical solution of the present application, the midpoint interconnection circuit can quickly disconnect the connection between the midpoint of the first current conversion module and other modules when detecting the change of the midpoint potential of the first current conversion module, so as to decouple the first current conversion module from other modules, thereby avoiding the propagation of fault current to other modules through the midpoint interconnection circuit.

[0074] In some embodiments, referring to Figure 7 and Figure 8 The midpoint interconnection circuit 512 comprises a second fuse F2.

[0075] More specifically, the first end of the second fuse F2 in each current conversion module is connected with the midpoint of the corresponding current conversion module. The second ends of the plurality of second fuses F2 in the plurality of current conversion modules are connected in parallel.

[0076] When the first current conversion module does not have a short-circuit condition, even if there is a potential difference between the midpoints of the modules, the current flowing through the second fuse F2 will be much smaller than the melting current of the second fuse F2, and the midpoint interconnection circuit can ensure that the midpoint potentials of the modules are consistent, thereby balancing the midpoint potentials.

[0077] And in the case of short-circuit of the first current conversion module, for example, in Figure 8In the shown circuit, if a short circuit occurs in the positive bus capacitor C3 in the first current conversion module, the midpoint potential of the first current conversion module will be pulled up, and the midpoint potential of the module will be much higher than the midpoint potential of other modules, thereby causing a convergence current between the multiple midpoint interconnection circuits. The convergence current flows from the midpoint of the first current conversion module to the midpoints of other modules.

[0078] To avoid the influence of the convergence current on other modules, in the scheme of the embodiments of the present application, the melting current of the second fuse F2 is set to be less than or equal to the aforementioned convergence current. At this time, the second fuse corresponding to the first current conversion module will be melted under the action of the convergence current, thereby decoupling the midpoint of the first current conversion module.

[0079] Meanwhile, it should be noted that, due to the parallel connection of multiple modules, the aforementioned convergence current will be shunted to multiple modules. In order to avoid mistakenly disconnecting the midpoint of the module that has not occurred a short circuit, the melting current of the second fuse F2 can be set to be greater than the current shunted to each module. The value of the melting current is related to the positive DC bus voltage, the number of current conversion modules, and the path impedance and other factors.

[0080] It can also be understood that, if the half bus short circuit occurs in the negative half bridge of the inverter bridge circuit, the midpoint potential of the first current conversion module will be pulled down. At this time, the convergence current flows from the midpoints of other modules to the midpoint of the first current conversion module. This current will also cause the second fuse to melt, thereby decoupling the faulty first current conversion module from the entire circuit.

[0081] According to the above technical means, by setting the second fuse in the midpoint interconnection circuit and setting the melting point current of the second fuse to be lower than the convergence current, the rapid decoupling of the faulty module can be realized, thereby preventing the fault from propagating to other modules, and further improving the operation stability and safety of the entire rail transit traction system.

[0082] In some embodiments, referring to Figure 9 , the midpoint interconnection circuit 512 includes a switching circuit 5121.

[0083] The switching circuit 5121 refers to an electronic switching element or a combination thereof for controlling the electrical connection state between the DC bus midpoints. The switching circuit 5121 can be composed of controllable switches and realize the opening and closing function through control signals.

[0084] In the normal operation state (i.e., no half bus short circuit occurs), the switching circuit is in the on state, so that the midpoint potentials between the modules can balance with each other. When a half bus short circuit occurs in the inverter bridge circuit of the first current conversion module, the corresponding first switching circuit in the first current conversion module is disconnected, so as to decouple the first current conversion module.

[0085] In the embodiments of the present application, the controllable switching circuit is arranged to replace the traditional direct connection mode of the midpoint, so that the midpoint potential balance can be achieved when the system is normally running, and the faulty module can be quickly isolated when a local fault occurs. In this way, the running of the entire system can be affected due to the failure of a single module.

[0086] In some embodiments, with reference to Figure 9 the current conversion circuit further comprises a control circuit 530 connected with the switching circuit 5121 in the plurality of current conversion modules 510, for controlling the switching circuit 5121 in the plurality of current conversion modules 510 to be turned on when no half bus short circuit occurs in the inverter bridge circuit of the first current conversion module, and for controlling the first switching circuit corresponding to the first current conversion module to be turned off when a half bus short circuit occurs in the inverter bridge circuit of the first current conversion module, so as to decouple the first current conversion module.

[0087] The control circuit refers to an electronic device for controlling the action of a switching device through logical judgment and signal output. The circuit is usually composed of a microprocessor, a driving chip, an isolation element, etc., and is responsible for issuing instructions according to the running state of the system to control the conduction or turn-off of each switching circuit. In the embodiments, the control circuit is connected with the switching circuit in each current conversion module, so that the running state of the entire system can be centrally managed.

[0088] By controlling the conduction of the switching circuits of the plurality of current conversion modules through the control circuit, the midpoint balance can be maintained when the system is normally running, the circulating current between the modules can be effectively reduced, and the efficiency and reliability of the system can be improved. When a half bus short circuit occurs, the corresponding switching circuit is quickly turned off through the control circuit, so that the faulty module is decoupled, which can effectively prevent the spread of the fault and protect the remaining normal modules to continue running.

[0089] In some embodiments, as shown in Figure 10 and Figure 11 the switching circuit 5121 is an active bridge circuit 51211.

[0090] The active bridge circuit is a topology structure composed of two IGBT modules connected in anti-series, which can realize the dynamic connection or disconnection between the midpoints of the DC bus by controlling the conduction state of the two IGBT modules.

[0091] The IGBT module in the active bridge circuit 51211 described above includes a first switch tube and an anti-parallel diode, and the control circuit 530 is connected with the gate of the first switch tube to control the switching state of the first switch tube. The control circuit is used for:

[0092] The two IGBT modules are controlled to be turned on when the half bus short circuit does not occur in the inverter bridge circuit of the first current conversion module. The two IGBT modules being turned on can be that the first switch in the two IGBT modules is turned on at the same time or is turned on complementarily, and at this time, the active bridge circuit is equivalent to a direct channel, and the midpoint potential balance between the modules can be maintained.

[0093] When the half bus short circuit occurs in the inverter bridge circuit of the first current conversion module, the control circuit can control the two IGBT modules to be turned off, so that the midpoint of the module is isolated from other modules.

[0094] In the technical scheme of the embodiments of the present application, the on-off state of the IGBT module is switched according to whether the half bus short circuit occurs, so that the system efficiency can be maintained in normal operation, and the influence path of the fault module can be quickly cut off in an abnormal situation.

[0095] In some embodiments, Figure 9 The switch circuit in the foregoing embodiments can also be a metal oxide semiconductor field effect transistor (MOSFET) or a thyristor.

[0096] In some embodiments, as shown in Figure 12 and Figure 13 The switch circuit 5121 includes a controllable switch 51212, and the control circuit 530 is connected with the controllable switch 51212. The controllable switch 51212 can be a relay or a contactor, which can be turned on or turned off under the control of the control circuit 530.

[0097] The control circuit 530 is configured to control the controllable switch to be turned on when the half bus short circuit does not occur in the inverter bridge circuit of the first current conversion module, and control the controllable switch in the active bridge circuit corresponding to the first current conversion module to be turned off when the half bus short circuit occurs in the inverter bridge circuit of the first current conversion module.

[0098] In some embodiments, the current conversion module 510 further includes a plurality of third fuses F3, which are arranged between the AC end of the inverter bridge circuit and the multi-phase power grid.

[0099] For example, as shown in Figure 6 The A phase, the B phase and the C phase of the three-phase AC power grid are converted into an a phase output, a b phase output and a c phase output through a transformer, and the a phase output, the b phase output and the c phase output are connected with the AC end of the three ANPC type three-level converters in the inverter bridge module.

[0100] In some implementations, a filter circuit is further arranged between the three-phase alternating current power grid and the inverter bridge circuit, including three filter inductors L and three filter capacitors C, the three filter inductors are arranged between the three phases of the three-phase alternating current power grid and the alternating current ends of the three ANPC three-level converters respectively, one end of the three filter capacitors is connected in communication, and the other end is connected to the end of the three filter inductors close to the three-phase alternating current power grid.

[0101] In Figure 6 In the circuit shown, three third fuses F3 are arranged in each current conversion module, and are respectively arranged between the three filter inductors and the three-phase alternating current power grid.

[0102] When a half bus short circuit occurs in the inverter bridge circuit of the first current conversion module, one or more of the plurality of third fuses F3 are fused, so that the alternating current end of the first current conversion module is decoupled from the alternating current end of the other current conversion modules.

[0103] Still taking the first current conversion module in the traction current conversion system as an example, the three ANPC three-level converters in parallel in the first current conversion module are denoted as a first converter, a second converter and a third converter respectively. Figure 6

[0104] For example, in the case of short circuit of the first switch tube and the second switch tube of the first converter, the alternating current end of the first converter is connected to the direct current bus to form a low impedance path, at this time the current of the positive direct current bus flows through the short circuit point and the alternating current end of the first converter to the transformer; in the transformer, the three-phase transformer coils are connected to each other, so that the current of the positive direct current bus flows through the alternating current end to the alternating current end of the second converter and the third converter.

[0105] At the same time, since the inverter bridge circuits of the plurality of current conversion modules in the traction current conversion system are all connected to the alternating current transformer in the alternating current power grid, the short circuit current in the first current conversion module will flow into the other current conversion modules through the alternating current bus.

[0106] In the case of short circuit of the first switch tube and the second switch tube of the first converter, the short circuit current will be sharply increased due to the small impedance of the current path, which will cause the other switch tubes in the first current conversion module and the switch tubes in the other current conversion modules to bear a large current, which will cause the other switch tubes to be impacted.

[0107] ​In the technical solution of the present application, due to the presence of the third fuse, when the short circuit occurs, the short circuit current flowing into the transformer through the AC end of the first converter is greater than the minimum fuse current of F3, so that the third fuse F3 connected with the AC end of the first converter is quickly fused, cutting off the connection between the short circuit point in the first converter module and the AC bus, thereby decoupling the AC end of the first converter module from other converter modules, so as to avoid the influence of the short circuit current on other switch tubes in the first converter module and other converter modules, and ensure that other modules can still work normally.

[0108] Figure 14 is a schematic structural diagram of a traction converter system 1400 provided by an embodiment of the present application. As shown in the figure, the traction converter system 1400 includes a plurality of converter modules 1410 connected in parallel, a controller 1420, a power grid 1430, a positive DC bus BUS+ and a negative DC bus BUS-. Figure 14 As shown in the figure, the traction converter system 1400 includes a plurality of converter modules 1410 connected in parallel, a controller 1420, a power grid 1430, a positive DC bus BUS+ and a negative DC bus BUS-.

[0109] The above-mentioned converter module 1410 includes an inverter bridge circuit 1411, a first fuse 1412 and a midpoint interconnection circuit 1413.

[0110] The inverter bridge circuit 1411 has a DC end and an AC end, the DC end is connected with the positive DC bus and the negative DC bus, and the AC end is connected with the power grid 1430.

[0111] In some embodiments, the inverter bridge circuit 1411 includes the ANPC type three-level conversion circuit shown in the foregoing Figure 3

[0112] The first fuse 1412 is arranged between the DC end of the inverter bridge circuit 1411 and the positive DC bus or the negative DC bus.

[0113] The first end of the midpoint interconnection circuit 1413 is connected with the midpoint of the inverter bridge circuit, and the second ends of the midpoint interconnection circuits 1413 in the plurality of converter modules 1410 are connected in parallel.

[0114] When the inverter bridge circuit of a first converter module in the plurality of converter modules 1410 occurs half-bus short circuit, the first midpoint interconnection circuit corresponding to the first converter module is disconnected, so as to decouple the first converter module from the midpoints of other converter modules, and the first converter module is any one of the plurality of converter modules.

[0115] The controller 1420 is connected with the plurality of converter modules 1410, and is used to control the inverter bridge circuit 1411 in the plurality of converter modules 1410 to perform bidirectional conversion between the DC end and the AC end, so as to supply power to the DC load through the positive DC bus and the negative DC bus, or inversely convert the power generated by the DC load to the power grid. ​

[0116] As a possible implementation, the number of the above-mentioned controllers 1420 can be multiple, and the multiple controllers 1420 are correspondingly connected with the multiple variable flow modules 1410. Each controller 1420 is respectively used for controlling the turn-on and turn-off of each switch tube in the corresponding connected variable flow module 1410, and performing the module-level protection logic and the like.

[0117] In addition to the above-mentioned multiple controllers 1420, the traction variable flow system 1400 further includes a system-level controller, which can be connected with the multiple controllers 1420 to perform the system-level scheduling and the system-level protection logic.

[0118] Alternatively, as another possible implementation, the number of the above-mentioned controllers 1420 can be one, and the one controller 1420 is connected with the multiple variable flow modules 1410 to control the switch tubes in each variable flow module 1410.

[0119] In some embodiments, the midpoint interconnection circuit includes a second fuse; when a half bus short circuit occurs in the inverter bridge circuit of the first variable flow module, the second fuse is fused to decouple the first variable flow module; the fuse current of the second fuse is smaller than the convergence current of the midpoint of the inverter bridge circuit of the first variable flow module; wherein the convergence current is the current flowing through the midpoint of the inverter bridge circuit of the first variable flow module from the midpoint of the inverter bridge circuit of the other variable flow module when a half bus short circuit occurs in the inverter bridge circuit of the first variable flow module.

[0120] In some embodiments, the midpoint interconnection circuit includes a switching circuit; the switching circuit includes a controllable switch; the controller is connected with the controllable switch in the multiple variable flow modules, and the controller is used for: controlling the controllable switch in the multiple variable flow modules to be turned on when a half bus short circuit does not occur in the inverter bridge circuit of the first variable flow module; controlling the first controllable switch corresponding to the first variable flow module to be turned off to decouple the first variable flow module when a half bus short circuit occurs in the inverter bridge circuit of the first variable flow module.

[0121] Alternatively, the above-mentioned switching circuit includes an active bridge circuit, and the active bridge circuit includes two IGBT modules connected in anti-series, and the IGBT module includes a first switch tube and an anti-parallel diode; the controller is connected with the gate of the first switch tube, and the controller is used for: controlling the two IGBT modules to be turned on when a half bus short circuit does not occur in the inverter bridge circuit of the first variable flow module; controlling the two IGBT modules in the active bridge circuit corresponding to the first variable flow module to be turned off when a half bus short circuit occurs in the inverter bridge circuit of the first variable flow module.

[0122] The above is described in combination with Figures 1-14The device embodiments of the present application are described in detail, and the method embodiments of the present application will be described in detail below with reference to the drawings. It should be understood that the method embodiments correspond to the foregoing device embodiments, and therefore, the parts not described in detail can be referred to the foregoing device embodiments.

[0123] Figure 15 is a schematic flow chart of a control method of a traction converter system provided by an embodiment of the present application. The traction converter system can be the traction converter system 1400 shown in Figure 14 . The traction converter system includes: a plurality of converter modules connected in parallel, a positive DC bus, a negative DC bus and a power grid; the converter module includes: an inverter bridge circuit having a DC end and an AC end, the DC end being connected with the positive DC bus and the negative DC bus, and the AC end being used for connecting with the power grid; a first fuse being arranged between the DC end of the inverter bridge circuit and the positive DC bus or the negative DC bus; a midpoint interconnection circuit, a first end of the midpoint interconnection circuit being connected with a midpoint of the inverter bridge circuit; a second end of the midpoint interconnection circuit in the plurality of converter modules being connected in parallel; when a half bus short circuit occurs in the inverter bridge circuit of a first converter module in the plurality of converter modules, a first midpoint interconnection circuit corresponding to the first converter module is disconnected, so as to decouple the first converter module from the midpoints of other converter modules, and the first converter module is any one of the plurality of converter modules.

[0124] Figure 15 The method in the above embodiment includes: controlling the inverter bridge circuit in the plurality of converter modules to perform bidirectional conversion between the DC end and the AC end, so as to supply power to a DC load through the positive DC bus and the negative DC bus, or to convert the power generated by the DC load to the power grid.

[0125] In some embodiments, the midpoint interconnection circuit includes a switching circuit, and the switching circuit includes a controllable switch; the method includes: controlling the controllable switch in the plurality of converter modules to be turned on when the half bus short circuit does not occur in the inverter bridge circuit of the first converter module; and controlling the first controllable switch corresponding to the first converter module to be turned off when the half bus short circuit occurs in the inverter bridge circuit of the first converter module, so as to decouple the first converter module; or the switching circuit includes an active bridge circuit, and the active bridge circuit includes two IGBT modules connected in anti-series, and the IGBT module includes a first switch tube and an anti-parallel diode; the method includes: controlling the two IGBT modules to be turned on when the half bus short circuit does not occur in the inverter bridge circuit of the first converter module; and controlling the two IGBT modules in the active bridge circuit corresponding to the first converter module to be turned off when the half bus short circuit occurs in the inverter bridge circuit of the first converter module, so as to decouple the first converter module.

[0126] The embodiment of the present application further provides a computer readable storage medium, which stores a computer program, and the computer program is executed to realize the foregoing method steps.

[0127] In several embodiments provided in the present application, it should be understood that the disclosed system, device and method can be implemented in other manners. For example, the described device embodiments are merely schematic, and the division of the units is merely a logical function division, and there can be another division manner in actual implementation. For example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections can be indirect couplings or communication connections through some interfaces, devices or units, and can be in electrical, mechanical or other forms.

[0128] The units described as separated components can or can not be physically separated, and the components displayed as units can or can not be physical units, i.e., can be located in one place, or can be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purposes of the embodiments of the present application.

[0129] In addition, each functional unit in the embodiments of the present application can be integrated in a processing unit, or each unit can exist physically as a separate unit, or two or more units can be integrated in one unit.

[0130] In the above embodiments, all or part of the embodiments can be implemented by software, hardware, firmware or any combination thereof. When implemented by software, all or part of the embodiments can be implemented in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of the present application are generated. The computer can be a general purpose computer, a special purpose computer, a computer network, or other programmable apparatus. The computer instructions can be stored in a computer readable storage medium or transmitted from one computer readable storage medium to another computer readable storage medium, for example, the computer instructions can be transmitted from one website, computer, server or data center to another website, computer, server or data center through wired (such as coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (such as infrared, wireless, microwave, etc.) manner. The computer readable storage medium can be any available medium that can be read by a computer or a data storage device such as a server, data center, etc. integrated with one or more available media sets. The available media can be magnetic media (for example, floppy disk, hard disk, magnetic tape), optical media (for example, digital video disc (DVD)) or semiconductor media (for example, solid state disk (SSD)) and the like.

[0131] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical range disclosed in the present application, which should be covered within the protection scope of the present application.

Claims

1. A current conversion module, characterized by The application relates to a traction current conversion system applied to multiple parallel current conversion modules, the traction current conversion system comprising: a positive direct current bus, a negative direct current bus and a power grid; the current conversion module comprising: an inverter bridge circuit having a direct current end and an alternating current end, the direct current end being used for connection with the positive direct current bus and the negative direct current bus, the positive direct current bus and the negative direct current bus being used for connection with a direct current load, and the alternating current end being used for connection with the power grid; a first fuse being arranged between the direct current end of the inverter bridge circuit and the positive direct current bus or the negative direct current bus; a midpoint interconnection circuit, a first end of the midpoint interconnection circuit being connected with a midpoint of the inverter bridge circuit and being used for maintaining balance of midpoint potentials of the current conversion modules in normal operation; a second end of the midpoint interconnection circuit in the multiple current conversion modules being in parallel connection; when a half bus short circuit occurs in the inverter bridge circuit of a first current conversion module in the multiple current conversion modules, a first midpoint interconnection circuit corresponding to the first current conversion module is disconnected, so that the first current conversion module is decoupled from the midpoints of other current conversion modules, and the first current conversion module is any one of the multiple current conversion modules.

2. The current module of claim 1, wherein, the midpoint interconnection circuit comprising a second fuse; when the half bus short circuit occurs in the inverter bridge circuit of the first current conversion module, the second fuse is fused, so that the first current conversion module is decoupled; a fuse current of the second fuse is smaller than a convergence current of the midpoint of the inverter bridge circuit of the first current conversion module; wherein the convergence current is a current flowing from the midpoint of the inverter bridge circuit of the other current conversion modules to the midpoint of the inverter bridge circuit of the first current conversion module when the half bus short circuit occurs in the inverter bridge circuit of the first current conversion module.

3. The current module of claim 1, wherein, the midpoint interconnection circuit comprising a switching circuit; when the half bus short circuit does not occur in the inverter bridge circuit of the first current conversion module, the switching circuit is turned on, so that the midpoints of the inverter bridge circuits of the multiple current conversion modules are connected; when the half bus short circuit occurs in the inverter bridge circuit of the first current conversion module, a first switching circuit corresponding to the first current conversion module is turned off, so that the first current conversion module is decoupled.

4. The current conversion module according to claim 3, wherein the switching circuit comprises a controllable switch; the current conversion module further comprises a control circuit, the control circuit being connected with the controllable switch in the multiple current conversion modules, and the control circuit being used for: controlling the controllable switch in the multiple current conversion modules to be turned on when the half bus short circuit does not occur in the inverter bridge circuit of the first current conversion module; controlling the first controllable switch corresponding to the first current conversion module to be turned off when the half bus short circuit occurs in the inverter bridge circuit of the first current conversion module, so that the first current conversion module is decoupled; or the switching circuit comprises an active bridge circuit, the active bridge circuit comprising two IGBT modules in anti-serial connection, the IGBT module comprising a first switch tube and an anti-parallel diode; the current conversion module further comprises a control circuit, the control circuit being connected with a gate of the first switch tube, and the control circuit being used for: controlling the two IGBT modules to be turned on when the half bus short circuit does not occur in the inverter bridge circuit of the first current conversion module. In a case that a half bus short circuit occurs in the inverter bridge circuit of the first current conversion module, the two IGBT modules in the active bridge circuit corresponding to the first current conversion module are controlled to be turned off, so as to decouple the first current conversion module.

5. The current conversion module according to any one of claims 1-4, wherein, The current conversion module further comprises a plurality of third fuses, each of which is arranged between the AC end of the inverter bridge circuit and the multi-phase of the power grid. In a case that a half bus short circuit occurs in the inverter bridge circuit of the first current conversion module, one or more of the plurality of third fuses are blown, so as to decouple the AC end of the first current conversion module from the AC end of the other current conversion modules.

6. A traction converter system, characterized by The current conversion module further comprises a plurality of third fuses, each of which is arranged between the AC end of the inverter bridge circuit and the multi-phase of the power grid. The current conversion module further comprises a plurality of third fuses, each of which is arranged between the AC end of the inverter bridge circuit and the multi-phase of the power grid. The current conversion module further comprises a plurality of third fuses, each of which is arranged between the AC end of the inverter bridge circuit and the multi-phase of the power grid. The current conversion module further comprises a plurality of third fuses, each of which is arranged between the AC end of the inverter bridge circuit and the multi-phase of the power grid. The midpoint interconnection circuit of the plurality of current conversion modules are connected in parallel. In a case that a half bus short circuit occurs in the inverter bridge circuit of the first current conversion module, the first midpoint interconnection circuit corresponding to the first current conversion module is turned off, so as to decouple the first current conversion module from the midpoint of the other current conversion modules. The controller is connected with the plurality of current conversion modules, and is configured to control the inverter bridge circuits in the plurality of current conversion modules to perform bidirectional current conversion between the DC end and the AC end, so as to supply power to the DC load through the positive DC bus and the negative DC bus, or to convert the power generated by the DC load to the power grid. The midpoint interconnection circuit comprises a second fuse.

7. The traction converter system of claim 6, wherein, In a case that a half bus short circuit occurs in the inverter bridge circuit of the first current conversion module, the second fuse is blown, so as to decouple the first current conversion module. The blowing current of the second fuse is smaller than the convergence current of the midpoint of the inverter bridge circuit of the first current conversion module. The convergence current is the current flowing from the midpoint of the inverter bridge circuit of the other current conversion modules to the midpoint of the inverter bridge circuit of the first current conversion module in a case that a half bus short circuit occurs in the inverter bridge circuit of the first current conversion module. The midpoint interconnection circuit comprises a switching circuit.

8. A traction converter system according to claim 6 or 7, characterized in that The switching circuit comprises a controllable switch. The controller is connected with the controllable switch in the plurality of current conversion modules, and the controller is configured to: In a case that a half bus short circuit does not occur in the inverter bridge circuit of the first current conversion module, the controllable switch in the plurality of current conversion modules is controlled to be turned on. In a case that a half bus short circuit occurs in the inverter bridge circuit of the first current conversion module, the first controllable switch corresponding to the first current conversion module is controlled to be turned off, so as to decouple the first current conversion module. Or, ​ The switch circuit comprises an active bridge circuit, and the active bridge circuit comprises two IGBT modules connected in anti-series, and the IGBT module comprises a first switch tube and an anti-parallel diode. The controller is connected with the gate of the first switch tube, and the controller is used for: When the inverter bridge circuit of the first current conversion module does not occur half bus short circuit, the two IGBT modules are controlled to be turned on; When the inverter bridge circuit of the first current conversion module occurs half bus short circuit, the two IGBT modules in the active bridge circuit corresponding to the first current conversion module are controlled to be turned off, so that the first current conversion module is decoupled.

9. A control method of a traction converter system, characterized by, The traction current conversion system comprises a plurality of current conversion modules connected in parallel, a positive direct current bus, a negative direct current bus and a power grid; The current conversion module comprises: an inverter bridge circuit having a direct current end and an alternating current end, the direct current end being connected with the positive direct current bus and the negative direct current bus, the positive direct current bus and the negative direct current bus being used for connecting with a direct current load, and the alternating current end being used for connecting with the power grid; a first fuse arranged between the direct current end of the inverter bridge circuit and the positive direct current bus or the negative direct current bus; a midpoint interconnection circuit, a first end of the midpoint interconnection circuit being connected with a midpoint of the inverter bridge circuit, and the midpoint interconnection circuit being used for maintaining balance of the midpoint potential of each current conversion module in normal operation; second ends of the midpoint interconnection circuits in the plurality of current conversion modules are connected in parallel; When the inverter bridge circuit of a first current conversion module in the plurality of current conversion modules occurs half bus short circuit, a first midpoint interconnection circuit corresponding to the first current conversion module is turned off, so that the midpoint of the first current conversion module is decoupled from the midpoint of other current conversion modules, and the first current conversion module is any one of the plurality of current conversion modules; The method comprises: controlling the inverter bridge circuit in the plurality of current conversion modules to perform bidirectional current conversion between the direct current end and the alternating current end, so as to supply power to a direct current load through the positive direct current bus and the negative direct current bus, or inversely convert electric energy generated by the direct current load to the power grid.

10. The control method of a traction converter system according to claim 9, characterized by, The midpoint interconnection circuit comprises a switch circuit, and the switch circuit comprises a controllable switch. The method comprises: When the inverter bridge circuit of the first current conversion module does not occur half bus short circuit, the controllable switch in the plurality of current conversion modules is controlled to be turned on; When the inverter bridge circuit of the first current conversion module occurs half bus short circuit, the first controllable switch corresponding to the first current conversion module is controlled to be turned off, so that the first current conversion module is decoupled; Alternatively, The switch circuit comprises an active bridge circuit, and the active bridge circuit comprises two IGBT modules connected in anti-series, and the IGBT module comprises a first switch tube and an anti-parallel diode. The method comprises: When the inverter bridge circuit of the first current conversion module does not occur half bus short circuit, the two IGBT modules are controlled to be turned on; When the inverter bridge circuit of the first current conversion module occurs half bus short circuit, the two IGBT modules in the active bridge circuit corresponding to the first current conversion module are controlled to be turned off, so that the first current conversion module is decoupled.

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