Multi-topology conversion traction converter and control method thereof

Abstract

The present application belongs to the field of electric locomotive application, and particularly relates to a novel multi-topology conversion traction converter and a control method thereof. The present application solves the technical problem that the main circuit topology structure of the traction converter is determined in the current traction converter design, and cannot be converted according to the actual scene or working condition. When a switching device in the power module of the traction converter is damaged, the whole vehicle power loss is caused, and the reliability and operation efficiency of the locomotive operation are greatly affected. The present application optimizes the main topology of the traction converter, adopts modular design, reduces the types of power modules, reduces the inventory of spare parts, and the main topology structure of the four-quadrant converter can be flexibly converted according to the scene demand. When the switching device is damaged, the normal operation of the traction converter can still be realized through topology switching. The application environment and application working condition are redundantly designed, and the reliability and operation efficiency of the traction converter are greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of electric locomotive applications, specifically relating to a novel multi-topology transformation traction converter and its control method. Background Technology

[0002] Traction converters are core components of AC drive systems in rail transit, primarily functioning to convert AC to DC to AC power. Currently, the main circuit topology of traction converters is fixed in their design and cannot be changed based on actual conditions or operating conditions. When switching devices in the power modules of the traction converter fail, it can easily cause a loss of power to the entire vehicle, significantly impacting the reliability and operational efficiency of the locomotive.

[0003] In existing technologies, on the one hand, the rectifier circuit topology (DC converter module) and the AC circuit topology (AC converter module) cannot be uniformly interchanged. If a switching device in the same module fails, the power module will shut down directly, making redundant configuration impossible and affecting its reliability and stability. On the other hand, the topology cannot be changed with operating conditions. With limited cooling capacity, existing technologies cannot achieve good harmonic characteristics through low switching frequencies. Summary of the Invention

[0004] This invention addresses the problem that current traction converter designs have a fixed main circuit topology, which cannot be adapted to actual conditions or operating conditions. Furthermore, when switching devices in the power modules of the traction converter fail, it can easily cause power loss in the entire vehicle, significantly impacting the reliability and operational efficiency of the locomotive. This invention provides a traction converter with multiple topology transformations and its control method.

[0005] The traction converter with multi-topology conversion described in this invention is implemented using the following technical solution: It includes a DC conversion module, a DC support module, an AC conversion module, a topology conversion device, a pre-charging device, a controller, a circuit breaker, and an isolation device. The topology conversion device consists of a pulse conversion module and a topology conversion unit. The pulse conversion module comprises pulse conversion module 1 and pulse conversion module 2. The topology conversion unit includes topology conversion device 1 and topology conversion device 2. Pulse conversion module 1 is connected to topology conversion device 1, and pulse conversion module 2 is connected to topology conversion device 2. The DC conversion module consists of two bridge arms formed by modules S and N. The S and N bridge arms are identical. The S bridge arm is a main circuit topology structure composed of eight IGBTs connected in series and parallel, including S11, S12, S13, S14, S21, and S22. 2. S23, S24; where the midpoint between S11 and S12 is connected to the midpoint between S21 and S22, and the midpoint between S13 and S14 is connected to the midpoint between S23 and S24. The midpoint S1o between S12 and S13 and the midpoint S2o between S22 and S23 are respectively used as output taps of the S-arm and sent to the topology conversion device; the N-arm is a main circuit topology structure composed of 8 IGBTs connected in series and parallel. The N-arm includes N11, N12, N13, N14, N21, N22, N23, and N24; where the midpoint between N11 and N12 is connected to the midpoint between N21 and N22, and the midpoint between N13 and N14 is connected to the midpoint between N23 and N24. The midpoint N1o between N12 and N13 and the midpoint N2o between N22 and N23 are respectively used as output taps of the N-arm and sent to the topology conversion device 1;

[0006] The DC support module consists of two support resistors and three support capacitors. One of the support capacitors C is connected in parallel to the positive and negative DC bus. The support resistors R1 and R2 and the support capacitors C1 and C2 are connected in series and then in parallel. The intermediate point Uo is used as the output tap of the DC support module and sent to the topology converter 2. The DC converter module and the DC support module are connected through the circuit breaker 1.

[0007] The AC converter module consists of four modules: A, B, C, and D. Each module is identical to the S and N modules of the DC converter module. The output terminals of module A are A1o and A2o, those of module B are B1o and B2o, those of module C are C1o and C2o, and those of module D are D1o and D2o. The output terminals of each module of the AC converter module are connected to the topology converter 2. The DC support module is connected to the AC converter module through circuit breaker 2. The controller is bidirectionally connected to the topology converter. The pulse conversion module is used to control and convert the pulse drive of the IGBT. The topology converter realizes different paths and breaks according to the switching of different switching devices, thus completing the transformation of the main circuit topology of the DC converter module and the AC converter module.

[0008] Furthermore, the pulse conversion module generates pulse signals, which include both pulses and signals. Pulses control the IGBT devices, while signals control the circuit breakers in the topology conversion device, isolation device, and pre-charging device. The topology conversion device changes the topology of the traction converter's main circuit. Its control commands and conversion methods are given by the controller, and it receives commands from the controller to perform actions.

[0009] The pre-charging device mainly performs the pre-charging function. It consists of a pre-charging resistor and a contactor connected in parallel. When the traction converter starts, the pre-charging resistor is connected in series in the main circuit to charge the DC support module, avoiding the impact on the power devices and capacitors in the DC support module caused by direct charging.

[0010] The controller monitors the converter's functionality, operating conditions, and the status of each module. It controls the topology conversion device based on different priorities. Once the topology circuit is determined, it provides the corresponding control algorithm to implement the corresponding function.

[0011] The control method for a multi-topology conversion traction converter described in this invention, for a DC-DC conversion module, has the following corresponding conversion conditions:

[0012] (1) Condition 1: The controller enables pulse conversion and circuit conversion. The pulse conversion module enables the IGBT pulse and has full pulse transmission capability. The controller controls the topology conversion module to connect the midpoint output taps S1o and S2o of the S-bridge arm to the grid input terminal S through the pre-charging device. It connects the midpoint output taps N1o and N2o of the N-bridge arm to the grid input terminal N. The output taps of the DC support module are left floating. This circuit forms a four-quadrant converter of the two-level main topology circuit with two transistors in parallel. The controller uses a two-level control algorithm to control the IGBT switching devices in the main topology to realize the DC conversion function.

[0013] (2) In the second working condition, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables the IGBT pulse, and S11, S21, S14, S24, N11, N21, N14, and N24 are continuously given a high level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 1 to connect the midpoint output taps S1o and S2o of the S bridge arm and then connect them to the grid voltage input terminal S through the pre-charging device. It connects the midpoint output taps N1o and N2o of the N bridge arm and then connects them to the grid voltage input terminal N. The output taps of the DC support module are left floating. This circuit constitutes a four-quadrant converter of the two-level main topology circuit. The controller uses a two-level control algorithm to control the IGBT switching devices in the main topology to realize the DC conversion function.

[0014] (3) In the third working condition, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables the IGBT pulse, and S12, S22, S13, S23, N12, N22, N13, and N23 are continuously given a high level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 1 to connect the midpoint output taps S1o and S2o of the S bridge arm and then connect them to the grid voltage input terminal S through the pre-charging device. It connects the midpoint output taps N1o and N2o of the N bridge arm and then connects them to the grid voltage input terminal N. The output taps of the DC support module are left floating. This circuit constitutes a four-quadrant converter of the two-level main topology circuit. The controller uses a two-level control algorithm to control the IGBT switching devices in the main topology to realize the DC conversion function.

[0015] (4) Operating condition four: The controller enables pulse conversion and circuit conversion. The pulse conversion module enables the IGBT pulse, and S11, S12, S13, S14, N11, N12, N13, and N14 are continuously low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 1 to connect the midpoint output taps S1o and Uo of the S-bridge arm and the midpoint output taps N1o and Uo of the N-bridge arm. S2o is connected to the main grid input terminal S, and N2o is connected to the main grid input terminal N. This circuit constitutes a four-quadrant converter of the diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBT switching devices in the main topology to realize the DC-DC conversion function.

[0016] (5) Operating condition five: The controller enables pulse conversion and circuit conversion. The pulse conversion module enables the IGBT pulse, and S21, S22, S23, S24, N21, N22, N23, and N24 are continuously low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 1 to connect the midpoint output taps S2o and Uo of the S-bridge arm and the midpoint output taps N2o and Uo of the N-bridge arm. S1o is connected to the main grid input terminal S, and N1o is connected to the main grid input terminal N. This circuit constitutes a four-quadrant converter of the diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBT switching devices in the main topology to realize the DC-DC conversion function.

[0017] (6) Condition 6: The controller enables pulse conversion and circuit conversion. The pulse conversion module enables the IGBT pulse, and S21, S22, S23, S24, N11, N12, N13, and N14 are continuously low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 1 to connect the midpoint output taps S2o and Uo of the S-bridge arm and the midpoint output taps N1o and Uo of the N-bridge arm. S1o is connected to the mains voltage input terminal S, and N2o is connected to the mains voltage input terminal N. This circuit constitutes a four-quadrant converter of the diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBT switching devices in the main topology to realize the DC-DC conversion function.

[0018] (7) Operating condition seven: The controller enables pulse conversion and circuit conversion. The pulse conversion module enables the IGBT pulse, and S11, S14, N11, and N14 are continuously low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 1 to connect the midpoint output taps S1o and Uo of the S-bridge arm, and connect the midpoint output taps N1o and Uo of the N-bridge arm. S2o is connected to the grid voltage input terminal S, and N2o is connected to the grid voltage input terminal N. This circuit constitutes a four-quadrant converter of the three-level main topology circuit with active midpoint clamping. The controller uses the ANPC control algorithm to control the IGBT switching devices in the main topology to realize the DC-DC conversion function.

[0019] (8) Operating condition eight, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables the IGBT pulse, and S21, S24, N21, and N24 are continuously low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 1 to connect the midpoint output taps S2o and Uo of the S-bridge arm and the midpoint output taps N2o and Uo of the N-bridge arm. S1o is connected to the mains voltage input terminal S, and N1o is connected to the mains voltage input terminal N. This circuit constitutes a four-quadrant converter of the three-level main topology circuit with active midpoint clamping. The controller uses the ANPC control algorithm to control the IGBT switching devices in the main topology to realize the DC-DC conversion function.

[0020] (9) Operating condition nine, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables the IGBT pulse, and S21, S24, N11, and N14 are continuously low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 1 to connect the midpoint output taps S2o and Uo of the S-bridge arm and the midpoint output taps N1o and Uo of the N-bridge arm. S1o is connected to the grid voltage input terminal S, and N2o is connected to the grid voltage input terminal N. This circuit constitutes a four-quadrant converter of the three-level main topology circuit with active midpoint clamping. The controller uses the ANPC control algorithm to control the IGBT switching devices in the main topology to realize the DC-DC conversion function.

[0021] It also includes (10) settings under normal operating conditions:

[0022] (a) When the application does not have high requirements for harmonics on the pantograph-catenary side, a two-level four-quadrant topology consisting of operating conditions one, two, and three is adopted. When the system is operating at full power and full load, the operating condition one scheme is adopted. When the power is operating at half load or light load, the operating condition two and three schemes are adopted. When the system is operating in operating condition two and any one of the IGBTs S12, S13, N22, and N23 breaks down and short-circuits, operating condition two can be switched to operating condition three for normal operation.

[0023] (b) When the application has high requirements for harmonics on the pantograph-catenary side and the intermediate voltage level is high, and the switching device is a Si device, the main circuit topology of diode clamping composed of operating conditions four, five and six can be adopted.

[0024] (c) When the application has high requirements for harmonics on the pantograph-catenary side and the intermediate bus voltage is greater than the withstand voltage rating of the device or the power device is a SiC device, the active clamping main circuit topology consisting of operating conditions seven, eight and nine can be adopted.

[0025] The control method is designed for the following conversion conditions of the AC converter module:

[0026] In the AC converter module, any three of the four sub-modules can be combined to form a three-phase inverter topology. The remaining sub-module performs the intermediate circuit chopping function. The following combinations are possible: Modules ABC form a three-phase inverter topology, and module D is the chopper module; Modules ABD form a three-phase inverter topology, and module C is the chopper module; Modules ACD form a three-phase inverter topology, and module B is the chopper module; Modules BCD form a three-phase inverter topology, and module A is the chopper module. Taking the ABC module forming a three-phase inverter topology with module D as the chopper module as an example, the operating conditions are analyzed. When module D is used as the chopper module, there are three usage scenarios. The first scenario involves using the intermediate circuit chopper function of the D bridge arm... In the first configuration, the middle taps D10 and D20 of the D bridge arm are connected to the output terminal D via topology conversion device 2, and port D is connected to an external chopper resistor. In the second configuration, the middle tap D10 of the D bridge arm is connected to port D via topology conversion device 2 and then connected to the chopper resistor, while D20 is left floating via topology conversion device 2. In the third configuration, the middle tap D20 of the D bridge arm is connected to port D via topology conversion device 2 and then connected to the chopper resistor, while D10 is left floating via topology conversion device 2. The chopper module can be flexibly selected and matched according to different operations. When using other modules as chopper modules, the operation is exactly the same as that of the D module.

[0027] (1) Condition 1: The controller enables pulse conversion and circuit conversion. The pulse conversion module enables the IGBT pulse and has full pulse transmission capability. The controller controls the topology conversion device 2 to connect the midpoint output taps A1o and A2o of the A bridge arm to the output terminal A, connect the midpoint output taps B1o and B2o of the B bridge arm to the output terminal B, connect the midpoint output taps C1o and C2o of the C bridge arm to the output terminal C, and leave the DC support module output taps floating. This circuit constitutes a three-phase inverter of a two-level main topology circuit with two tubes in parallel. The controller uses a two-level control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function.

[0028] (2) In the second working condition, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables the IGBT pulse, and IGBTA11, IGBTA21, IGBTA14, IGBTA24, IGBTB11, IGBTB21, IGBTB14, IGBTB24, IGBBTC11, IGBBTC21, IGBBTC14, and IGBBTC24 are continuously given a high level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A1o and A2o of the A bridge arm to the output terminal A, connect the midpoint output taps B1o and B2o of the B bridge arm to the output terminal B, connect the midpoint output taps C1o and C2o of the C bridge arm to the output terminal C, and leave the DC support module output taps floating. This circuit constitutes a three-phase inverter of a two-level main topology circuit. The controller uses a two-level control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function.

[0029] (3) In the third working condition, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables the IGBT pulse, and IGBTA12, IGBTA22, IGBTA13, IGBTA23, IGBTB12, IGBTB22, IGBTB13, IGBTB23, IGBBTC12, IGBBTC22, IGBBTC13, and IGBBTC23 are continuously given a high level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A1o and A2o of the A bridge arm to the output terminal A, connect the midpoint output taps B1o and B2o of the B bridge arm to the output terminal B, connect the midpoint output taps C1o and C2o of the C bridge arm to the output terminal C, and leave the DC support module output taps floating. This circuit constitutes a three-phase inverter of a two-level main topology circuit. The controller uses a two-level control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function.

[0030] (4) Operating Condition 4: The controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA11, IGBTA12, IGBTA13, IGBTA14, IGBTB11, IGBTB12, IGBTB13, IGBTB14, IGBBTC11, IGBBTC12, IGBBTC13, and IGBBTC14 are continuously given a low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A1o and Uo of the A bridge arm, the midpoint output taps B1o and Uo of the B bridge arm, and the midpoint output taps C1o and Uo of the C bridge arm. A2o is connected to the output terminal A, B2o is connected to the output terminal B, and C2o is connected to the output terminal C. This circuit constitutes a three-phase inverter of a diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0031] (5) Operating condition 5: The controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA11, IGBTA12, IGBTA13, IGBTA14, IGBTB11, IGBTB12, IGBTB13, IGBTB14, IGBBTC21, IGBBTC22, IGBBTC23, and IGBBTC24 are continuously given a low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A1o and Uo of the A bridge arm, connect the midpoint output taps B1o and Uo of the B bridge arm, and connect the midpoint output taps C2o and Uo of the C bridge arm. A2o is connected to the output terminal A, B2o is connected to the output terminal B, and C1o is connected to the output terminal C. This circuit constitutes a three-phase inverter of a diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0032] (6) Operating Condition 6: The controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA11, IGBTA12, IGBTA13, IGBTA14, IGBTB21, IGBTB22, IGBTB23, IGBTB24, IGBBTC11, IGBBTC12, IGBBTC13, and IGBBTC14 are continuously given a low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A1o and Uo of the A bridge arm, the midpoint output taps B2o and Uo of the B bridge arm, and the midpoint output taps C1o and Uo of the C bridge arm. A2o is connected to the output terminal A, B1o is connected to the output terminal B, and C2o is connected to the output terminal C. This circuit constitutes a three-phase inverter of a diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0033] (7) Operating Condition 7: The controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA21, IGBTA22, IGBTA23, IGBTA24, IGBTB11, IGBTB12, IGBTB13, IGBTB14, IGBBTC11, IGBBTC12, IGBBTC13, and IGBBTC14 are continuously given a low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A2o and Uo of the A bridge arm, connect the midpoint output taps B1o and Uo of the B bridge arm, and connect the midpoint output taps C1o and Uo of the C bridge arm. A1o is connected to the output terminal A, B2o is connected to the output terminal B, and C2o is connected to the output terminal C. This circuit constitutes a three-phase inverter of a diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0034] (8) Condition 8: The controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA21, IGBTA22, IGBTA23, IGBTA24, IGBTB11, IGBTB12, IGBTB13, IGBTB14, IGBBTC21, IGBBTC22, IGBBTC23, and IGBBTC24 are continuously given a low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A2o and Uo of the A bridge arm, the midpoint output taps B1o and Uo of the B bridge arm, and the midpoint output taps C2o and Uo of the C bridge arm. A1o is connected to the output terminal A, B2o is connected to the output terminal B, and C1o is connected to the output terminal C. This circuit constitutes a three-phase inverter of a diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0035] (9) Operating Condition 9: The controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA21, IGBTA22, IGBTA23, IGBTA24, IGBTB21, IGBTB22, IGBTB23, IGBTB24, IGBBTC11, IGBBTC12, IGBBTC13, and IGBBTC14 are continuously given a low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A2o and Uo of the A bridge arm, the midpoint output taps B2o and Uo of the B bridge arm, and the midpoint output taps C1o and Uo of the C bridge arm. A1o is connected to the output terminal A, B2o is connected to the output terminal B, and C2o is connected to the output terminal C. This circuit constitutes a three-phase inverter of a diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0036] (10) Operating condition 10: The controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA21, IGBTA22, IGBTA23, IGBTA24, IGBTB21, IGBTB22, IGBTB23, IGBTB24, IGBBTC21, IGBBTC22, IGBBTC23, and IGBBTC24 are continuously given a low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A2o and Uo of the A bridge arm, the midpoint output taps B2o and Uo of the B bridge arm, and the midpoint output taps C2o and Uo of the C bridge arm. A1o is connected to the output terminal A, B1o is connected to the output terminal B, and C1o is connected to the output terminal C. This circuit constitutes a three-phase inverter of a diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0037] (11) Operating condition eleven, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA11, IGBTA12, IGBTA13, IGBTA14, IGBTB21, IGBTB22, IGBTB23, IGBTB24, IGBBTC21, IGBBTC22, IGBBTC23, and IGBBTC24 are continuously given a low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A1o and Uo of the A bridge arm, the midpoint output taps B2o and Uo of the B bridge arm, and the midpoint output taps C2o and Uo of the C bridge arm. A2o is connected to the output terminal A, B1o is connected to the output terminal B, and C1o is connected to the output terminal C. This circuit constitutes a three-phase inverter of a diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0038] (12) Operating condition twelve, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA11, IGBTA14, IGBTB11, IGBTB14, IGBBTC11, and IGBBTC14 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A1o and Uo of the A bridge arm, the midpoint output taps B1o and Uo of the B bridge arm, and the midpoint output taps C1o and Uo of the C bridge arm. A2o is connected to the output terminal A, B2o is connected to the output terminal B, and C2o is connected to the output terminal C. This circuit constitutes a three-phase inverter of the three-level main topology circuit with active midpoint clamping. The controller uses the ANPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0039] (13) Operating condition thirteen, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA11, IGBTA14, IGBTB11, IGBTB14, IGBBTC21, and IGBBTC24 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A1o and Uo of the A bridge arm, the midpoint output taps B1o and Uo of the B bridge arm, and the midpoint output taps C2o and Uo of the C bridge arm. A2o is connected to the output terminal A, B2o is connected to the output terminal B, and C1o is connected to the output terminal C. This circuit constitutes a three-phase inverter of the three-level main topology circuit with active midpoint clamping. The controller uses the ANPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0040] (14) Operating condition fourteen, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA21, IGBTA24, IGBTB11, IGBTB14, IGBBTC11, and IGBBTC14 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A2o and Uo of the A bridge arm, the midpoint output taps B1o and Uo of the B bridge arm, and the midpoint output taps C1o and Uo of the C bridge arm. A1o is connected to the output terminal A, B2o is connected to the output terminal B, and C2o is connected to the output terminal C. This circuit constitutes a three-phase inverter of the three-level main topology circuit with active midpoint clamping. The controller uses the ANPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0041] (15) Operating condition 15: The controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA11, IGBTA14, IGBTB21, IGBTB24, IGBBTC11, and IGBBTC14 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A1o and Uo of the A bridge arm, the midpoint output taps B2o and Uo of the B bridge arm, and the midpoint output taps C1o and Uo of the C bridge arm. A2o is connected to the output terminal A, B1o is connected to the output terminal B, and C2o is connected to the output terminal C. This circuit constitutes a three-phase inverter of the three-level main topology circuit with active midpoint clamping. The controller uses the ANPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0042] (16) Operating condition sixteen, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA11, IGBTA14, IGBTB21, IGBTB24, IGBBTC21, and IGBBTC24 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A1o and Uo of the A bridge arm, the midpoint output taps B2o and Uo of the B bridge arm, and the midpoint output taps C2o and Uo of the C bridge arm. A2o is connected to the output terminal A, B1o is connected to the output terminal B, and C1o is connected to the output terminal C. This circuit constitutes a three-phase inverter of the three-level main topology circuit with active midpoint clamping. The controller uses the ANPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0043] (17) Operating condition seventeen, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA21, IGBTA24, IGBTB21, IGBTB24, IGBBTC11, and IGBBTC14 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A2o and Uo of the A bridge arm, the midpoint output taps B2o and Uo of the B bridge arm, and the midpoint output taps C1o and Uo of the C bridge arm. A1o is connected to the output terminal A, B1o is connected to the output terminal B, and C2o is connected to the output terminal C. This circuit constitutes a three-phase inverter of the three-level main topology circuit with active midpoint clamping. The controller uses the ANPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0044] (18) In operating condition eighteen, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA21, IGBTA24, IGBTB11, IGBTB14, IGBBTC21, and IGBBTC24 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A2o and Uo of the A bridge arm, the midpoint output taps B1o and Uo of the B bridge arm, and the midpoint output taps C2o and Uo of the C bridge arm. A1o is connected to the output terminal A, B2o is connected to the output terminal B, and C1o is connected to the output terminal C. This circuit constitutes a three-phase inverter of the three-level main topology circuit with active midpoint clamping. The controller uses the ANPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0045] (19) Operating condition nineteen, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA21, IGBTA24, IGBTB21, IGBTB24, IGBBTC21, and IGBBTC24 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A2o and Uo of the A bridge arm, the midpoint output taps B2o and Uo of the B bridge arm, and the midpoint output taps C2o and Uo of the C bridge arm. A1o is connected to the output terminal A, B1o is connected to the output terminal B, and C1o is connected to the output terminal C. This circuit constitutes a three-phase inverter of the three-level main topology circuit with active midpoint clamping. The controller uses the ANPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0046] It also includes (20) settings under normal operating conditions:

[0047] (a) When the AC conversion load has low requirements for harmonics, a two-level inverter topology consisting of operating conditions one, two, and three is adopted. When the power is running at full load, the operating condition one scheme is adopted. When the power is running at half load or light load, the operating conditions two and three schemes are adopted. When the system is operating in operating condition two and any IGBT breaks down and short-circuits, operating condition two can be switched to operating condition three for normal operation.

[0048] (b) When the AC conversion load has high requirements for harmonics and the intermediate voltage level is high, and the switching device is a Si device, the diode clamping main circuit topology in operating conditions four to eleven can be adopted.

[0049] (c) When the AC conversion load has high requirements for harmonics, the intermediate bus voltage is greater than the withstand voltage rating of the device, and the power device is a SiC device, the active clamping main circuit topology structure consisting of operating conditions twelve to nineteen can be adopted.

[0050] This invention solves the following technical problems:

[0051] 1. The transformation of the main topology circuit of the traction converter makes the topology structure of the traction converter more flexible;

[0052] 2. Modular and standardized design, with fewer types of modular units;

[0053] 3. Adjust the topology and control method of the traction converter according to the working conditions and actual needs to improve the harmonic characteristics of the pantograph-catenary side and the load side, as well as the overall system reliability.

[0054] This invention optimizes the main topology of the traction converter and adopts a modular design, reducing the types of power modules and the inventory of spare parts. Moreover, the main topology of the four-quadrant converter can be flexibly changed according to needs. Even if the switching device fails, the traction converter can still operate normally through topology switching. Redundancy design is provided for different application environments and operating conditions, which greatly improves the reliability and operating efficiency of the traction converter. Attached Figure Description

[0055] Figure 1 This is the main circuit topology of the traction converter.

[0056] Figure 2 Operating condition control diagram of DC-DC converter module.

[0057] Figure 3 AC converter module operating condition control diagram. Detailed Implementation

[0058] 1. Figure 1The traction converter main circuit topology mainly consists of a DC-DC converter module, a DC support module, an AC-AC converter module, a topology converter, a pre-charging device, a controller, a circuit breaker, and an isolation device. The DC module comprises two bridge arms, S and N, which are identical. The S bridge arm is a main circuit topology composed of eight IGBTs connected in series and parallel. The midpoint between S11 and S12 is connected to the midpoint between S21 and S22, and the midpoint between S13 and S14 is connected to the midpoint between S23 and S24. The midpoints S1o of S12 and S13 and S2o of S22 and S23 are respectively used as output taps of the S-arm and fed into the topology converter. The N-arm is a main circuit topology structure composed of 8 IGBTs connected in series and parallel. The midpoints of N11 and N12 are connected to the midpoints of N21 and N22, and the midpoints of N13 and N14 are connected to the midpoints of N23 and N24. The midpoints N1o of N12 and N13 and N2o of N22 and N23 are respectively used as output taps of the N-arm and fed into the topology converter. The DC support module consists of two support circuits and three support capacitors, such as... Figure 1 As shown, one of the supporting capacitors C is connected in parallel to the positive and negative DC buses. Supporting resistors R1 and R2, and supporting capacitors C1 and C2 are connected in series and then in parallel. The intermediate connection point Uo serves as the output tap of the DC support module, leading to the topology converter. The DC converter module and the DC support module are connected via circuit breaker 1. The AC converter module consists of four modules: A, N, C, and D. Each module is identical to the S and N modules of the DC converter module. The output terminals of module A are A1o and A2o, the output terminals of module N are N1o and N2o, the output terminals of module C are C1o and C2o, and the output terminals of module D are D1o and D2o. The output terminals of each module of the AC converter module are connected to the topology converter 2. The DC support module and the AC converter module are connected via circuit breaker 2.

[0059] 2. The topology conversion device consists of two parts: pulse signals and topology conversion. The pulse conversion mainly controls the pulse drive of the IGBTs. The topology conversion device is mainly composed of a series of circuit breakers arranged in a fixed structure. Its main function is to realize different paths and breaks according to the switching of different switching devices, and to complete the transformation of the main circuit topology of the DC-DC converter module and the AC-DC converter module. The pulse signal includes two types: pulse and signal. The pulse mainly controls the IGBT devices, and the signal mainly controls the circuit breakers in the topology conversion device, isolation device, and pre-charging device. The topology conversion device realizes the change of the main circuit topology of the traction converter. Its control commands and conversion methods are given by the controller, and it receives commands from the controller to perform actions.

[0060] 3. The pre-charging device mainly realizes the pre-charging function. It mainly consists of a pre-charging resistor and a contactor connected in parallel. When the traction converter starts, the pre-charging resistor is connected in series in the main circuit to charge the DC support module, avoiding the impact on the power devices and capacitors in the DC support module caused by direct charging.

[0061] 4. The main function of the controller is to monitor the function implementation, operating conditions and status of each module of the converter, and to control the topology conversion device according to different priorities. After the topology circuit is determined, the controller provides the corresponding control algorithm to realize the corresponding function.

[0062] 5. Main operating conditions of the DC-DC converter module:

[0063] (1) Condition 1: The controller enables pulse conversion and circuit conversion. The pulse conversion module enables the IGBT pulse and has full pulse transmission capability. The controller controls the topology conversion module to connect the midpoint output taps S1o and S2o of the S-bridge arm to the grid voltage input terminal S, and connect the midpoint output taps N1o and N2o of the N-bridge arm to the grid voltage input terminal N. The output taps of the DC support module are left floating. This circuit constitutes a four-quadrant converter of a two-level main topology circuit with two transistors in parallel. The controller uses a two-level control algorithm to control the IGBT switching devices in the main topology to realize the DC conversion function.

[0064] (2) In the second working condition, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables the IGBT pulse, and IGBTS11, IGBTS21, IGBTS14, IGBTS24, IGBTN11, IGBTN21, IGBTN14, and IGBTN24 are given a continuous high level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 1 to connect the midpoint output taps S1o and S2o of the S bridge arm to the grid voltage input terminal S, and connect the midpoint output taps N1o and N2o of the N bridge arm to the grid voltage input terminal N. The output tap of the DC support module is left floating. This circuit constitutes a four-quadrant converter of the two-level main topology circuit. The controller uses a two-level control algorithm to control the IGBT switching devices in the main topology to realize the DC conversion function.

[0065] (3) In the third working condition, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables the IGBT pulse, and IGBTS12, IGBTS22, IGBTS13, IGBTS23, IGBTN12, IGBTN22, IGBTN13, and IGBTN23 are given a continuous high level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 1 to connect the midpoint output taps S1o and S2o of the S bridge arm to the grid voltage input terminal S, and connect the midpoint output taps N1o and N2o of the N bridge arm to the grid voltage input terminal N. The output tap of the DC support module is left floating. This circuit constitutes a four-quadrant converter of the two-level main topology circuit. The controller uses a two-level control algorithm to control the IGBT switching devices in the main topology to realize the DC conversion function.

[0066] (4) Operating condition four: The controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTS11, IGBTS12, IGBTS13, IGBTS14, IGBTN11, IGBTN12, IGBTN13, and IGBTN14 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 1 to connect the midpoint output taps S1o and Uo of the S-bridge arm, and connect the midpoint output taps N1o and Uo of the N-bridge arm. S2o is connected to the main grid input terminal S, and N2o is connected to the main grid input terminal N. This circuit constitutes a four-quadrant converter of the diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBT switching devices in the main topology to realize the DC-DC conversion function.

[0067] (5) Operating condition five, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTS21, IGBTS22, IGBTS23, IGBTS24, IGBTN21, IGBTN22, IGBTN23, and IGBTN24 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 1 to connect the midpoint output taps S2o and Uo of the S bridge arm and the midpoint output taps N2o and Uo of the N bridge arm. S1o is connected to the main grid input terminal S, and N1o is connected to the main grid input terminal N. This circuit constitutes a four-quadrant converter of the diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBT switching devices in the main topology to realize the DC-DC conversion function.

[0068] (6) Condition 6: The controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses and gives IGBTS21, IGBTS22, IGBTS23, IGBTS24, IGBTN11, IGBTN12, IGBTN13, and IGBTN14 a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 1 to connect the midpoint output taps S2o and Uo of the S-bridge arm and the midpoint output taps N1o and Uo of the N-bridge arm. S1o is connected to the main grid input terminal S and N2o is connected to the main grid input terminal N. This circuit constitutes a four-quadrant converter of the diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBT switching devices in the main topology to realize the DC-DC conversion function.

[0069] (7) Condition 7: The controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTS11, IGBTS14, IGBTN11, and IGBTN14 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 1 to connect the midpoint output taps S1o and Uo of the S-bridge arm, and connect the midpoint output taps N1o and Uo of the N-bridge arm. S2o is connected to the grid voltage input terminal S, and N2o is connected to the grid voltage input terminal N. This circuit constitutes a four-quadrant converter of the three-level main topology circuit with active midpoint clamping. The controller uses the ANPC control algorithm to control the IGBT switching devices in the main topology to realize the DC-DC conversion function.

[0070] (8) Condition 8: The controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTS21, IGBTS24, IGBTN21, and IGBTN24 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 1 to connect the midpoint output taps S2o and Uo of the S-bridge arm and the midpoint output taps N2o and Uo of the N-bridge arm. S1o is connected to the grid voltage input terminal S, and N1o is connected to the grid voltage input terminal N. This circuit constitutes a four-quadrant converter of the three-level main topology circuit with active midpoint clamping. The controller uses the ANPC control algorithm to control the IGBT switching devices in the main topology to realize the DC-DC conversion function.

[0071] (9) Operating condition nine, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTS21, IGBTS24, IGBTN11, and IGBTN14 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 1 to connect the midpoint output taps S2o and Uo of the S-bridge arm and the midpoint output taps N1o and Uo of the N-bridge arm. S1o is connected to the grid voltage input terminal S, and N2o is connected to the grid voltage input terminal N. This circuit constitutes a four-quadrant converter of the three-level main topology circuit with active midpoint clamping. The controller uses the ANPC control algorithm to control the IGBT switching devices in the main topology to realize the DC-DC conversion function.

[0072] (10) Settings of DC-DC converter module under normal operating conditions:

[0073] (a) When the application does not have high requirements for harmonics on the pantograph-catenary side, a two-level four-quadrant topology consisting of operating conditions one, two, and three is adopted. When the system is operating at full power and full load, the operating condition one scheme is adopted. When the power is operating at half load or light load, the operating conditions two and three schemes are adopted. When the system is operating in operating condition two and any one of IGBTs12, IGBTS13, IGBTN22, and IGBTN23 breaks down and short-circuits, operating condition two can be switched to operating condition three for normal operation.

[0074] (b) When the application has high requirements for harmonics on the pantograph-catenary side and the intermediate voltage level is high, and the switching device is a Si device, the main circuit topology of diode clamping composed of operating conditions four, five and six can be adopted.

[0075] (c) When the application has high requirements for harmonics on the pantograph-catenary side and the intermediate bus voltage is greater than the withstand voltage rating of the device or the power device is a SiC device, the active clamping main circuit topology consisting of operating conditions seven, eight and nine can be adopted.

[0076] 6. Main operating conditions of the AC converter module:

[0077] The AC inverter module consists of four identical sub-modules: A, B, C, and D. These four sub-modules employ a redundant design, allowing for different combinations to form different topologies and perform different functions and effects depending on the operating conditions. Any three of the four sub-modules in the AC converter module can be combined to form a three-phase inverter topology, with the remaining sub-module performing the intermediate circuit chopping function. The main combination methods are as follows: ABC modules form a three-phase inverter topology, with module D as the chopper module; ABD modules form a three-phase inverter topology, with module C as the chopper module; ACD modules form a three-phase inverter topology, with module B as the chopper module; and BCD modules form a three-phase inverter topology, with module A as the chopper module. Taking the ABC module forming a three-phase inverter topology with module D as the chopper module as an example, the operating condition analysis shows that when module D is used as the chopper module, there are three usage scenarios. The first is to use the D bridge arm... In the first configuration, the intermediate output taps D10 and D20 of the D bridge arm are connected to the output terminal D via topology conversion device 2, and port D is connected to an external chopper resistor. In the second configuration, the intermediate tap D10 of the D bridge arm is connected to port D via topology conversion device 2 and then connected to the chopper resistor, while D20 is left floating via topology conversion device 2. In the third configuration, the intermediate tap D20 of the D bridge arm is connected to port D via topology conversion device 2 and then connected to the chopper resistor, while D10 is left floating via topology conversion device 2. The chopper module can be flexibly selected and matched according to different operations. When using other modules as chopper modules, the operation is exactly the same as that of D.

[0078] (1) In the first working condition, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables the IGBT pulse and has full pulse transmission capability. The controller controls the topology conversion device 2 to connect the midpoint output taps A1o and A2o of the A bridge arm to the output terminal A, connect the midpoint output taps B1o and B2o of the B bridge arm to the output terminal B, connect the midpoint output taps C1o and C2o of the C bridge arm to the output terminal C, and leave the DC support module output taps floating. This circuit constitutes a three-phase inverter of a two-level main topology circuit with two tubes in parallel. The controller adopts a two-level control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function.

[0079] (2) In the second operating condition, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables the IGBT pulse, and IGBTA11, IGBTA21, IGBTA14, IGBTA24, IGBTB11, IGBTB21, IGBTB14, IGBTB24, IGBBTC11, IGBBTC21, IGBBTC14, and IGBBTC24 are continuously given a high level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A1o and A2o of the A bridge arm to the output terminal A, connect the midpoint output taps B1o and B2o of the B bridge arm to the output terminal B, and connect the midpoint output taps C1o and C2o of the C bridge arm to the output terminal C. The output taps of the DC support module are left floating. This circuit constitutes a three-phase inverter of the two-level main topology circuit. The controller uses a two-level control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function.

[0080] (3) In the third working condition, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables the IGBT pulse, and IGBTA12, IGBTA22, IGBTA13, IGBTA23, IGBTB12, IGBTB22, IGBTB13, IGBTB23, IGBBTC12, IGBBTC22, IGBBTC13, and IGBBTC23 are continuously given a high level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A1o and A2o of the A bridge arm to the output terminal A, connect the midpoint output taps B1o and B2o of the B bridge arm to the output terminal B, connect the midpoint output taps C1o and C2o of the C bridge arm to the output terminal C, and leave the DC support module output taps floating. This circuit constitutes a three-phase inverter of a two-level main topology circuit. The controller uses a two-level control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function.

[0081] (4) Operating Condition 4: The controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA11, IGBTA12, IGBTA13, IGBTA14, IGBTB11, IGBTB12, IGBTB13, IGBTB14, IGBBTC11, IGBBTC12, IGBBTC13, and IGBBTC14 are continuously given a low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A1o and Uo of the A bridge arm, the midpoint output taps B1o and Uo of the B bridge arm, and the midpoint output taps C1o and Uo of the C bridge arm. A2o is connected to the output terminal A, B2o is connected to the output terminal B, and C2o is connected to the output terminal C. This circuit constitutes a three-phase inverter of a diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0082] (5) Operating condition five: The controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA11, IGBTA12, IGBTA13, IGBTA14, IGBTB11, IGBTB12, IGBTB13, IGBTB14, IGBBTC21, IGBBTC22, IGBBTC23, and IGBBTC24 are continuously given a low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A1o and Uo of the A bridge arm, the midpoint output taps B1o and Uo of the B bridge arm, and the midpoint output taps C2o and Uo of the C bridge arm. A2o is connected to the output terminal A, B2o is connected to the output terminal B, and C1o is connected to the output terminal C. This circuit constitutes a three-phase inverter of a diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0083] (6) Condition 6: The controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses and gives IGBT11, IGBT12, IGBT13, IGBT14, IGBTB21, IGBTB22, IGBTB23, IGBTB24, IGBBTC11, IGBBTC12, IGBBTC13, and IGBBTC14 a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A1o and Uo of the A bridge arm, the midpoint output taps B2o and Uo of the B bridge arm, and the midpoint output taps C1o and Uo of the C bridge arm. A2o is connected to the output terminal A, B1o is connected to the output terminal B, and C2o is connected to the output terminal C. This circuit constitutes a three-phase inverter of a diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0084] (7) Operating Condition 7: The controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA21, IGBTA22, IGBTA23, IGBTA24, IGBTB11, IGBTB12, IGBTB13, IGBTB14, IGBBTC11, IGBBTC12, IGBBTC13, and IGBBTC14 are continuously given a low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A2o and Uo of the A bridge arm, connect the midpoint output taps B1o and Uo of the B bridge arm, and connect the midpoint output taps C1o and Uo of the C bridge arm. A1o is connected to the output terminal A, B2o is connected to the output terminal B, and C2o is connected to the output terminal C. This circuit constitutes a three-phase inverter of a diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0085] (8) Operating condition eight, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA21, IGBTA22, IGBTA23, IGBTA24, IGBTB11, IGBTB12, IGBTB13, IGBTB14, IGBBTC21, IGBBTC22, IGBBTC23, and IGBBTC24 are continuously given a low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A2o and Uo of the A bridge arm, connect the midpoint output taps B1o and Uo of the B bridge arm, and connect the midpoint output taps C2o and Uo of the C bridge arm. Connect A1o to the output terminal A, B2o to the output terminal B, and C1o to the output terminal C. This circuit constitutes a three-phase inverter of a diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0086] (9) Operating Condition 9: The controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA21, IGBTA22, IGBTA23, IGBTA24, IGBTB21, IGBTB22, IGBTB23, IGBTB24, IGBBTC11, IGBBTC12, IGBBTC13, and IGBBTC14 are continuously given a low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A2o and Uo of the A bridge arm, the midpoint output taps B2o and Uo of the B bridge arm, and the midpoint output taps C1o and Uo of the C bridge arm. A1o is connected to the output terminal A, B2o is connected to the output terminal B, and C2o is connected to the output terminal C. This circuit constitutes a three-phase inverter of a diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0087] (10) Operating condition 10: The controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA21, IGBTA22, IGBTA23, IGBTA24, IGBTB21, IGBTB22, IGBTB23, IGBTB24, IGBBTC21, IGBBTC22, IGBBTC23, and IGBBTC24 are continuously given a low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A2o and Uo of the A bridge arm, the midpoint output taps B2o and Uo of the B bridge arm, and the midpoint output taps C2o and Uo of the C bridge arm. A1o is connected to the output terminal A, B1o is connected to the output terminal B, and C1o is connected to the output terminal C. This circuit constitutes a three-phase inverter of a diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0088] (11) Operating condition eleven, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA11, IGBTA12, IGBTA13, IGBTA14, IGBTB21, IGBTB22, IGBTB23, IGBTB24, IGBBTC21, IGBBTC22, IGBBTC23, and IGBBTC24 are continuously given a low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A1o and Uo of the A bridge arm, the midpoint output taps B2o and Uo of the B bridge arm, and the midpoint output taps C2o and Uo of the C bridge arm. A2o is connected to the output terminal A, B1o is connected to the output terminal B, and C1o is connected to the output terminal C. This circuit constitutes a three-phase inverter of a diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0089] (12) Operating condition twelve, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA11, IGBTA14, IGBTB11, IGBTB14, IGBBTC11, and IGBBTC14 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A1o and Uo of the A bridge arm, the midpoint output taps B1o and Uo of the B bridge arm, and the midpoint output taps C1o and Uo of the C bridge arm. A2o is connected to the output terminal A, B2o is connected to the output terminal B, and C2o is connected to the output terminal C. This circuit constitutes a three-phase inverter of the three-level main topology circuit with active midpoint clamping. The controller uses the ANPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0090] (13) Operating condition thirteen, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA11, IGBTA14, IGBTB11, IGBTB14, IGBBTC21, and IGBBTC24 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A1o and Uo of the A bridge arm, the midpoint output taps B1o and Uo of the B bridge arm, and the midpoint output taps C2o and Uo of the C bridge arm. A2o is connected to the output terminal A, B2o is connected to the output terminal B, and C1o is connected to the output terminal C. This circuit constitutes a three-phase inverter of the three-level main topology circuit with active midpoint clamping. The controller uses the ANPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0091] (14) Operating condition fourteen, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA21, IGBTA24, IGBTB11, IGBTB14, IGBBTC11, and IGBBTC14 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A2o and Uo of the A bridge arm, the midpoint output taps B1o and Uo of the B bridge arm, and the midpoint output taps C1o and Uo of the C bridge arm. A1o is connected to the output terminal A, B2o is connected to the output terminal B, and C2o is connected to the output terminal C. This circuit constitutes a three-phase inverter of the three-level main topology circuit with active midpoint clamping. The controller uses the ANPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0092] (15) Operating condition 15: The controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA11, IGBTA14, IGBTB21, IGBTB24, IGBBTC11, and IGBBTC14 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A1o and Uo of the A bridge arm, the midpoint output taps B2o and Uo of the B bridge arm, and the midpoint output taps C1o and Uo of the C bridge arm. A2o is connected to the output terminal A, B1o is connected to the output terminal B, and C2o is connected to the output terminal C. This circuit constitutes a three-phase inverter of the three-level main topology circuit with active midpoint clamping. The controller uses the ANPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0093] (16) Operating condition sixteen, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA11, IGBTA14, IGBTB21, IGBTB24, IGBBTC21, and IGBBTC24 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A1o and Uo of the A bridge arm, the midpoint output taps B2o and Uo of the B bridge arm, and the midpoint output taps C2o and Uo of the C bridge arm. A2o is connected to the output terminal A, B1o is connected to the output terminal B, and C1o is connected to the output terminal C. This circuit constitutes a three-phase inverter of the three-level main topology circuit with active midpoint clamping. The controller uses the ANPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0094] (17) Operating condition seventeen, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA21, IGBTA24, IGBTB21, IGBTB24, IGBBTC11, and IGBBTC14 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A2o and Uo of the A bridge arm, the midpoint output taps B2o and Uo of the B bridge arm, and the midpoint output taps C1o and Uo of the C bridge arm. A1o is connected to the output terminal A, B1o is connected to the output terminal B, and C2o is connected to the output terminal C. This circuit constitutes a three-phase inverter of the three-level main topology circuit with active midpoint clamping. The controller uses the ANPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0095] (18) In operating condition eighteen, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA21, IGBTA24, IGBTB11, IGBTB14, IGBBTC21, and IGBBTC24 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A2o and Uo of the A bridge arm, the midpoint output taps B1o and Uo of the B bridge arm, and the midpoint output taps C2o and Uo of the C bridge arm. A1o is connected to the output terminal A, B2o is connected to the output terminal B, and C1o is connected to the output terminal C. This circuit constitutes a three-phase inverter of the three-level main topology circuit with active midpoint clamping. The controller uses the ANPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0096] (19) Operating condition nineteen, the controller enables pulse conversion and circuit conversion. The pulse conversion module enables IGBT pulses, and IGBTA21, IGBTA24, IGBTB21, IGBTB24, IGBBTC21, and IGBBTC24 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the midpoint output taps A2o and Uo of the A bridge arm, the midpoint output taps B2o and Uo of the B bridge arm, and the midpoint output taps C2o and Uo of the C bridge arm. A1o is connected to the output terminal A, B1o is connected to the output terminal B, and C1o is connected to the output terminal C. This circuit constitutes a three-phase inverter of the three-level main topology circuit with active midpoint clamping. The controller uses the ANPC control algorithm to control the IGBT switching devices in the main topology to realize the AC conversion function of the inverter.

[0097] (20) Settings under normal operating conditions:

[0098] (a) When the AC conversion load has low requirements for harmonics, a two-level inverter topology consisting of operating conditions one, two, and three is adopted. When the power is running at full load, the operating condition one scheme is adopted. When the power is running at half load or light load, the operating conditions two and three schemes are adopted. When the system is operating in operating condition two and any IGBT breaks down and short-circuits, operating condition two can be switched to operating condition three for normal operation.

[0099] (b) When the AC conversion load has high requirements for harmonics and the intermediate voltage level is high, and the switching device is a Si device, the diode clamping main circuit topology in operating conditions four to eleven can be adopted.

[0100] (c) When the AC conversion load has high requirements for harmonics, the intermediate bus voltage is greater than the withstand voltage rating of the device, and the power device is a SiC device, the active clamping main circuit topology structure consisting of operating conditions twelve to nineteen can be adopted.

[0101] This invention is innovative in the following aspects: 1. The design concept, interface and control method of the traction converter;

[0102] 2. The structural and control framework of the traction converter;

[0103] 3. Switching between different control structures and control methods of the traction converter;

[0104] 4. Modular design and interface of the traction converter bridge arm;

[0105] 5. Main circuit topology design with high redundancy, scalability, compatibility, and portability.

Claims

1. A traction converter with multiple topology transformations, characterized in that: The system includes a DC-DC converter module, a DC support module, an AC-DC converter module, a topology converter, a pre-charging device, a controller, a circuit breaker, and an isolation device. The topology converter consists of a pulse converter module and a topology converter. The pulse converter module comprises pulse converter module 1 and pulse converter module 2. The topology converter includes topology converter 1 and topology converter 2, with pulse converter module 1 connected to topology converter 1 and pulse converter module 2 connected to topology converter 2. The DC-DC converter module consists of two identical bridge arms, S and N. The S bridge arm is a main circuit topology structure composed of eight IGBTs connected in series and parallel, including S11, S12, S13, S14, S21, S22, S23, and S24. S11, S12, S13, S14, S24, S23, S22, and S21 are connected in series, with S21 connected to S11. Among these, S11 and S12... The intermediate point is connected to the midpoint between S21 and S22, the intermediate point between S13 and S14 is connected to the midpoint between S23 and S24, and the midpoint S1o between S12 and S13 and the midpoint S2o between S22 and S23 are respectively used as output taps of the S-arm and sent to the topology transformation device 1; the N-arm is a main circuit topology structure composed of 8 IGBTs connected in series and parallel, and the N-arm includes N11, N12, N13, N14, N21, N22, N23, N 24; N11, N12, N13, N14, N24, N23, N22, and N21 are connected in series, with N21 connected to N11. The midpoint between N11 and N12 is connected to the midpoint between N21 and N22, and the midpoint between N13 and N14 is connected to the midpoint between N23 and N24. The midpoint N1o between N12 and N13 and the midpoint N2o between N22 and N23 are respectively used as N-arm output taps to be led out and fed into the topology transformation device 1. The DC support module consists of two support resistors and three support capacitors. One of the support capacitors C is connected in parallel to the positive and negative DC buses. Support resistors R1 and R2 are connected in series, and support capacitors C1 and C2 are connected in series. The series-connected support resistors R1 and R2 are connected in parallel with the series-connected support capacitors C1 and C2. The midpoint of R1 and R2 is connected to the midpoint of C1 and C2, and the result is used as the output tap Uo of the DC support module, which is then fed into the topology converter 2. The DC converter module and the DC support module are connected through circuit breaker 1. The AC converter module consists of four modules: A, B, C, and D. Each module is identical to the S and N modules of the DC converter module. The output terminals of module A are A1o and A2o, those of module B are B1o and B2o, those of module C are C1o and C2o, and those of module D are D1o and D2o. The output terminals of each module of the AC converter module are connected to the topology converter 2. The DC support module is connected to the AC converter module through circuit breaker 2. The controller is bidirectionally connected to the topology converter. The pulse conversion module is used to control and convert the pulse drive of the IGBT. The topology converter realizes different paths and breaks according to the switching of different switching devices, thus completing the transformation of the main circuit topology of the DC converter module and the AC converter module.

2. The traction converter with multi-topology transformation as described in claim 1, characterized in that: The pulse conversion module generates pulse signals, which include both pulses and signals. Pulses control the IGBTs, while signals control the contactors in the topology conversion device, isolation device, and pre-charging device. The topology conversion device changes the topology of the traction converter's main circuit. Its control commands and transformation methods are given by the controller, and it receives commands from the controller to perform actions.

3. The traction converter with multi-topology transformation as described in claim 1, characterized in that: The pre-charging device performs the pre-charging function and consists of a pre-charging resistor and a contactor connected in parallel. When the traction converter starts, the pre-charging resistor is connected in series in the main circuit to charge the DC support module, avoiding the impact on the IGBT and the capacitor in the DC support module caused by direct charging.

4. The traction converter with multi-topology transformation as described in claim 1, characterized in that: The controller monitors the converter's functionality, operating conditions, and the status of each module. It controls the topology conversion device based on different priorities. Once the main circuit topology is determined, it provides corresponding control algorithms to implement the corresponding functions.

5. A traction converter with multi-topology transformation as described in claim 1, characterized in that: The topology transformation device consists of a series of circuit breakers arranged in a fixed structure.

6. A control method for a traction converter with multi-topology transformation as described in any one of claims 1-5, characterized in that, For the DC-DC converter module, the corresponding conversion conditions are as follows: (1) Condition 1: The controller enables the pulse conversion module and topology conversion. The pulse conversion module enables the IGBT pulse and has full pulse transmission capability. The controller controls the topology conversion device 1 to connect the midpoints S1o and S2o of the S-bridge arm and then connect them to the first main voltage input terminal through the pre-charging device. It connects the midpoints N1o and N2o of the N-bridge arm and then connects them to the second main voltage input terminal. The output tap of the DC support module is left floating. This circuit forms a four-quadrant converter of the two-level main topology circuit with two tubes in parallel. The controller uses a two-level control algorithm to control the IGBT in the main circuit topology to realize the DC conversion function. (2) In the second working condition, the controller enables the pulse conversion module and the topology conversion. The pulse conversion module enables the IGBT pulse, and S11, S21, S14, S24, N11, N21, N14, and N24 are continuously given a high level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 1 to connect the middle points S1o and S2o of the S-bridge arm and then connect them to the first main voltage input terminal through the pre-charging device. It connects the middle points N1o and N2o of the N-bridge arm and then connects them to the second main voltage input terminal. The output tap of the DC support module is left floating. This circuit constitutes a four-quadrant converter of the two-level main topology circuit. The controller uses a two-level control algorithm to control the IGBTs in the main circuit topology to realize the DC conversion function. (3) In the third working condition, the controller enables the pulse conversion module and the topology conversion. The pulse conversion module enables the IGBT pulse, and S12, S22, S13, S23, N12, N22, N13, and N23 are continuously given a high level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 1 to connect the middle points S1o and S2o of the S-bridge arm and then connect them to the first main voltage input terminal through the pre-charging device. It connects the middle points N1o and N2o of the N-bridge arm and then connects them to the second main voltage input terminal. The output tap of the DC support module is left floating. This circuit constitutes a four-quadrant converter of the two-level main topology circuit. The controller uses a two-level control algorithm to control the IGBTs in the main circuit topology to realize the DC conversion function. (4) Operating condition four: The controller enables the pulse conversion module and the topology conversion. The pulse conversion module enables the IGBT pulse, and S11, S12, S13, S14, N11, N12, N13, and N14 are continuously low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 1 to connect the middle point S1o and Uo of the S-bridge arm, connect the middle point N1o and Uo of the N-bridge arm, connect S2o to the first main voltage input terminal, and connect N2o to the second main voltage input terminal. This circuit constitutes a four-quadrant converter of the diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBTs in the main circuit topology to realize the DC-DC conversion function. (5) Operating condition five: The controller enables the pulse conversion module and the topology conversion. The pulse conversion module enables the IGBT pulse, and S21, S22, S23, S24, N21, N22, N23, and N24 are continuously low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 1 to connect the middle point S2o and Uo of the S-bridge arm, and connect the middle point N2o and Uo of the N-bridge arm. S1o is connected to the first main voltage input terminal, and N1o is connected to the second main voltage input terminal. This circuit constitutes a four-quadrant converter of the diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBTs in the main circuit topology to realize the DC-DC conversion function. (6) Condition 6: The controller enables the pulse conversion module and the topology conversion. The pulse conversion module enables the IGBT pulse, and S21, S22, S23, S24, N11, N12, N13, and N14 are continuously low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 1 to connect the middle point S2o and Uo of the S-bridge arm and the middle point N1o and Uo of the N-bridge arm. S1o is connected to the first main voltage input terminal and N2o is connected to the second main voltage input terminal. This circuit constitutes a four-quadrant converter of the diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBTs in the main circuit topology to realize the DC-DC conversion function. (7) Operating condition seven: The controller enables the pulse conversion module and the topology conversion. The pulse conversion module enables the IGBT pulse, and S11, S14, N11, and N14 are continuously low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 1 to connect the midpoint S1o and Uo of the S-bridge arm, connect the midpoint N1o and Uo of the N-bridge arm, connect S2o to the first main voltage input terminal, and connect N2o to the second main voltage input terminal. This circuit constitutes a four-quadrant converter of the three-level main topology circuit with active midpoint clamping. The controller uses the ANPC control algorithm to control the IGBTs in the main circuit topology structure to realize the DC-DC conversion function. (8) Condition 8: The controller enables the pulse conversion module and the topology conversion. The pulse conversion module enables the IGBT pulse, and S21, S24, N21, and N24 are continuously low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 1 to connect the midpoint S2o and Uo of the S-bridge arm, and connect the midpoint N2o and Uo of the N-bridge arm. S1o is connected to the first main voltage input terminal, and N1o is connected to the second main voltage input terminal. This circuit constitutes a four-quadrant converter of the three-level main topology circuit with active midpoint clamping. The controller uses the ANPC control algorithm to control the IGBTs in the main circuit topology structure to realize the DC-DC conversion function. (9) Operating condition nine: The controller enables the pulse conversion module and the topology conversion. The pulse conversion module enables the IGBT pulse, and S21, S24, N11, and N14 are continuously low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 1 to connect the midpoint S2o and Uo of the S-bridge arm and the midpoint N1o and Uo of the N-bridge arm. S1o is connected to the first main voltage input terminal and N2o is connected to the second main voltage input terminal. This circuit constitutes a four-quadrant converter of the three-level main topology circuit with active midpoint clamping. The controller uses the ANPC control algorithm to control the IGBTs in the main circuit topology structure to realize the DC-DC conversion function.

7. The control method for a traction converter with multi-topology transformation as described in claim 6, characterized in that: It also includes (10) settings under normal operating conditions: (a) When the application does not have high requirements for harmonics on the pantograph-catenary side, a two-level four-quadrant topology consisting of operating conditions one, two, and three is adopted. When the system is operating at full power and full load, the operating condition one scheme is adopted. When the power is operating at half load or light load, the operating condition two and three schemes are adopted. When the system is operating in operating condition two and any one of the IGBTs S12, S13, N22, and N23 breaks down and short-circuits, operating condition two is switched to operating condition three for normal operation. (b) When the application has high requirements for harmonics on the pantograph-catenary side and the intermediate voltage level is high, and the IGBT uses Si devices, the diode clamping main circuit topology consisting of operating conditions four, five, and six is ​​adopted. (c) When the application has high requirements for harmonics on the pantograph-catenary side and the intermediate bus voltage is greater than the withstand voltage rating of the device or the IGBT uses SiC devices, the active clamping main circuit topology consisting of operating conditions seven, eight and nine shall be adopted.

8. A control method for a traction converter with multi-topology transformation as described in claim 6 or 7, characterized in that: The following conversion conditions apply to the AC converter module: In the AC converter module, any three of the four sub-modules can be combined to form a three-phase inverter topology. The remaining sub-module performs the intermediate circuit chopping function. The following combinations are possible: Modules ABC form a three-phase inverter topology, with module D as the chopper module; Modules ABD form a three-phase inverter topology, with module C as the chopper module; Modules ACD form a three-phase inverter topology, with module B as the chopper module; Modules BCD form a three-phase inverter topology, with module A as the chopper module. Module A is a main circuit topology consisting of eight IGBTs connected in series and parallel, including IGBT A11, IGBT A12, IGBT A13, IGBT A14, IGBT A21, and IGBT A22. 22, IGBTA23, IGBTA24; IGBTA11, IGBTA12, IGBTA13, IGBTA14, IGBTA24, IGBTA23, IGBTA22, IGBTA21 are connected in series, with IGBTA21 connected to IGBTA11. The midpoint between IGBTA11 and IGBTA12 is connected to the midpoint between IGBTA21 and IGBTA22. The midpoint between IGBTA13 and IGBTA14 is connected to the midpoint between IGBTA23 and IGBTA24. The midpoint A1o between IGBTA12 and IGBTA13 is connected to IGBTA... Point A2o, the midpoint between IGBT 22 and IGBT A23, serves as the output terminal of module A. Module B is a main circuit topology consisting of eight IGBTs connected in series and parallel, including IGBT 11, IGBT 12, IGBT 13, IGBT 14, IGBT 21, IGBT 22, IGBT 23, and IGBT 24. IGBT 11, IGBT 12, IGBT 13, IGBT 14, IGBT 24, IGBT 23, IGBT 22, and IGBT 21 are connected in series, with IGBT 21 connected to IGBT 11. IGBT 11 is connected to IGBT 24. The midpoint of BTB12 is connected to the midpoint of IGBTB21 and IGBTB22, and the midpoint of IGBTB13 and IGBTB14 is connected to the midpoint of IGBTB23 and IGBTB24. The midpoint B1o of IGBTB12 and IGBTB13 and the midpoint B2o of IGBTB22 and IGBTB23 serve as the output terminals of module B. Module C is a main circuit topology consisting of 8 IGBTs connected in series and parallel, including IGBTC11, IGBTC12, IGBTC13, IGBTC14, IGBTC21, IGBTC22, IGBTC23, and IGBTC24.IGBTC11, IGBTC12, IGBTC13, IGBTC14, IGBTC24, IGBTC23, IGBTC22, and IGBTC21 are connected in series, with IGBTC21 connected to IGBTC11. The midpoint between IGBTC11 and IGBTC12 is connected to the midpoint between IGBTC21 and IGBTC22. The midpoint between IGBTC13 and IGBTC14 is connected to the midpoint between IGBTC23 and IGBTC24. The midpoint C1o between IGBTC12 and IGBTC13 and the midpoint C1o between IGBTC22 and IGBTC24 are also connected. The intermediate point C2o serves as the output terminal of module C; module D is a main circuit topology composed of 8 IGBTs connected in series and parallel, including IGBTD11, IGBTD12, IGBTD13, IGBTD14, IGBTD21, IGBTD22, IGBTD23, and IGBTD24; IGBTD11, IGBTD12, IGBTD13, IGBTD14, IGBTD24, IGBTD23, IGBTD22, and IGBTD21 are connected in series, and IGBTD21 is connected to IGBTD11, wherein IGBTD11 and I... The midpoint of GBTD12 is connected to the midpoint of IGBTD21 and IGBTD22, and the midpoint of IGBTD13 and IGBTD14 is connected to the midpoint of IGBTD23 and IGBTD24. The midpoints D1o of IGBTD12 and IGBTD13 and D2o of IGBTD22 and IGBTD23 are respectively used as the output terminals of module D. A three-phase inverter topology is constructed using modules ABC. Module D is used as a chopper module for operating condition analysis. When module D is used as a chopper module, there are three usage scenarios. The first scenario is that the output terminals D10 and D20 of module D are connected through topology conversion device 2. After connection, it is connected to the fourth port of the isolation device, which is then connected to an external chopper resistor. Alternatively, the output terminal D10 of module D is connected to the fourth port of the isolation device via topology converter 2, and then connected to the chopper resistor, while D20 is left floating via topology converter 2. A third option connects the output terminal D20 of module D to the fourth port of the isolation device via topology converter 2, and then connects to the chopper resistor, while D10 is left floating via topology converter 2. The chopper module can be flexibly selected and matched according to different operating conditions. When using other modules as chopper modules, the operating method is exactly the same as module D. (1) Condition 1: The controller enables the pulse conversion module and topology conversion. The pulse conversion module enables the IGBT pulse and has full pulse transmission capability. The controller controls the topology conversion device 2 to connect the output terminals A1o and A2o of module A to the first output terminal of the isolation device, connect the output terminals B1o and B2o of module B to the second output terminal of the isolation device, connect the output terminals C1o and C2o of module C to the third output terminal of the isolation device, and leave the output tap of the DC support module floating. This circuit constitutes a three-phase inverter of a two-level main topology circuit with two transistors in parallel. The controller uses a two-level control algorithm to control the IGBT in the main circuit topology to realize the AC conversion function. (2) In operating condition 2, the controller enables the pulse conversion module and the topology conversion. The pulse conversion module enables the IGBT pulse, and IGBTA11, IGBTA21, IGBTA14, IGBTA24, IGBTB11, IGBTB21, IGBTB14, IGBTB24, IGBBTC11, IGBBTC21, IGBBTC14, and IGBBTC24 are continuously given a high level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the output terminals A1o and A2o of module A to the first output terminal of the isolation device, connect the output terminals B1o and B2o of module B to the second output terminal of the isolation device, connect the output terminals C1o and C2o of module C to the third output terminal of the isolation device, and leave the output tap of the DC support module floating. This circuit constitutes a three-phase inverter of a two-level main topology circuit. The controller uses a two-level control algorithm to control the IGBTs in the main circuit topology to realize the AC conversion function. (3) In operating condition three, the controller enables the pulse conversion module and the topology conversion. The pulse conversion module enables the IGBT pulse, and IGBTA12, IGBTA22, IGBTA13, IGBTA23, IGBTB12, IGBTB22, IGBTB13, IGBTB23, IGBBTC12, IGBBTC22, IGBBTC13, and IGBBTC23 are continuously given a high level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the output terminals A1o and A2o of module A to the first output terminal of the isolation device, connect the output terminals B1o and B2o of module B to the second output terminal of the isolation device, connect the output terminals C1o and C2o of module C to the third output terminal of the isolation device, and leave the output tap of the DC support module floating. This circuit constitutes a three-phase inverter of a two-level main topology circuit. The controller uses a two-level control algorithm to control the IGBTs in the main circuit topology to realize the AC conversion function. (4) Operating Condition 4: The controller enables the pulse conversion module and topology conversion. The pulse conversion module enables the IGBT pulse, and IGBTA11, IGBTA12, IGBTA13, IGBTA14, IGBTB11, IGBTB12, IGBTB13, IGBTB14, IGBBTC11, IGBBTC12, IGBBTC13, and IGBBTC14 are continuously given a low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the output terminals A1o and Uo of module A, the output terminals B1o and Uo of module B, and the output terminals C1o and Uo of module C. A2o is connected to the first output terminal of the isolation device, B2o is connected to the second output terminal of the isolation device, and C2o is connected to the third output terminal of the isolation device. This circuit constitutes a three-phase inverter of a diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBTs in the main circuit topology to realize the AC conversion function of the inverter. (5) Operating condition five: The controller enables the pulse conversion module and topology conversion. The pulse conversion module enables the IGBT pulse, and IGBTA11, IGBTA12, IGBTA13, IGBTA14, IGBTB11, IGBTB12, IGBTB13, IGBTB14, IGBBTC21, IGBBTC22, IGBBTC23, and IGBBTC24 are continuously given a low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the output terminals A1o and Uo of module A, the output terminals B1o and Uo of module B, and the output terminal C2o and Uo of module C. A2o is connected to the first output terminal of the isolation device, B2o is connected to the second output terminal of the isolation device, and C1o is connected to the third output terminal of the isolation device. This circuit constitutes a three-phase inverter of a diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBTs in the main circuit topology to realize the AC conversion function of the inverter. (6) Operating Condition 6: The controller enables the pulse conversion module and topology conversion. The pulse conversion module enables the IGBT pulses, and IGBTA11, IGBTA12, IGBTA13, IGBTA14, IGBTB21, IGBTB22, IGBTB23, IGBTB24, IGBBTC11, IGBBTC12, IGBBTC13, and IGBBTC14 are continuously given a low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the output terminals A1o and Uo of module A, the output terminals B2o and Uo of module B, and the output terminals C1o and Uo of module C. A2o is connected to the first output terminal of the isolation device, B1o is connected to the second output terminal of the isolation device, and C2o is connected to the third output terminal of the isolation device. This circuit constitutes a three-phase inverter of a diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBTs in the main circuit topology to realize the AC conversion function of the inverter. (7) Condition 7: The controller enables the pulse conversion module and topology conversion. The pulse conversion module enables the IGBT pulse, and IGBTA21, IGBTA22, IGBTA23, IGBTA24, IGBTB11, IGBTB12, IGBTB13, IGBTB14, IGBBTC11, IGBBTC12, IGBBTC13, and IGBBTC14 are continuously given a low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the output terminals A2o and Uo of module A, the output terminals B1o and Uo of module B, and the output terminals C1o and Uo of module C. A1o is connected to the first output terminal of the isolation device, B2o is connected to the second output terminal of the isolation device, and C2o is connected to the third output terminal of the isolation device. This circuit constitutes a three-phase inverter of a diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBTs in the main circuit topology to realize the AC conversion function of the inverter. (8) Condition 8: The controller enables the pulse conversion module and topology conversion. The pulse conversion module enables the IGBT pulse, and IGBTA21, IGBTA22, IGBTA23, IGBTA24, IGBTB11, IGBTB12, IGBTB13, IGBTB14, IGBBTC21, IGBBTC22, IGBBTC23, and IGBBTC24 are continuously given a low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the output terminals A2o and Uo of module A, the output terminals B1o and Uo of module B, and the output terminals C2o and Uo of module C. A1o is connected to the first output terminal of the isolation device, B2o is connected to the second output terminal of the isolation device, and C1o is connected to the third output terminal of the isolation device. This circuit constitutes a three-phase inverter of a diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBTs in the main circuit topology to realize the AC conversion function of the inverter. (9) Operating Condition 9: The controller enables the pulse conversion module and topology conversion. The pulse conversion module enables the IGBT pulse, and IGBTA21, IGBTA22, IGBTA23, IGBTA24, IGBTB21, IGBTB22, IGBTB23, IGBTB24, IGBBTC11, IGBBTC12, IGBBTC13, and IGBBTC14 are continuously given a low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the output terminals A2o and Uo of module A, the output terminals B2o and Uo of module B, and the output terminals C1o and Uo of module C. A1o is connected to the first output terminal of the isolation device, B2o is connected to the second output terminal of the isolation device, and C2o is connected to the third output terminal of the isolation device. This circuit constitutes a three-phase inverter of a diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBTs in the main circuit topology to realize the AC conversion function of the inverter. (10) Operating condition 10: The controller enables the pulse conversion module and topology conversion. The pulse conversion module enables the IGBT pulse, and IGBTA21, IGBTA22, IGBTA23, IGBTA24, IGBTB21, IGBTB22, IGBTB23, IGBTB24, IGBBTC21, IGBBTC22, IGBBTC23, and IGBBTC24 are continuously given a low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the output terminals A2o and Uo of module A, the output terminals B2o and Uo of module B, and the output terminals C2o and Uo of module C. A1o is connected to the first output terminal of the isolation device, B1o is connected to the second output terminal of the isolation device, and C1o is connected to the third output terminal of the isolation device. This circuit constitutes a three-phase inverter of a diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBTs in the main circuit topology to realize the AC conversion function of the inverter. (11) Operating condition eleven, the controller enables the pulse conversion module and topology conversion. The pulse conversion module enables the IGBT pulse, and IGBTA11, IGBTA12, IGBTA13, IGBTA14, IGBTB21, IGBTB22, IGBTB23, IGBTB24, IGBBTC21, IGBBTC22, IGBBTC23, and IGBBTC24 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the output terminals A1o and Uo of module A, the output terminals B2o and Uo of module B, and the output terminals C2o and Uo of module C. A2o is connected to the first output terminal of the isolation device, B1o is connected to the second output terminal of the isolation device, and C1o is connected to the third output terminal of the isolation device. This circuit constitutes a three-phase inverter of a diode-clamped three-level main topology circuit. The controller uses the NPC control algorithm to control the IGBTs in the main circuit topology to realize the AC conversion function of the inverter. (12) Operating condition twelve: The controller enables the pulse conversion module and topology conversion. The pulse conversion module enables the IGBT pulse, and IGBTA11, IGBTA14, IGBTB11, IGBTB14, IGBBTC11, and IGBBTC14 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the output terminals A1o and Uo of module A, the output terminals B1o and Uo of module B, and the output terminals C1o and Uo of module C. A2o is connected to the first output terminal of the isolation device, B2o is connected to the second output terminal of the isolation device, and C2o is connected to the third output terminal of the isolation device. This circuit constitutes a three-phase inverter of the three-level main topology circuit with active neutral clamp. The controller uses the ANPC control algorithm to control the IGBTs in the main circuit topology structure to realize the AC conversion function of the inverter. (13) Operating condition thirteen, the controller enables the pulse conversion module and topology conversion. The pulse conversion module enables the IGBT pulse, and IGBTA11, IGBTA14, IGBTB11, IGBTB14, IGBBTC21, and IGBBTC24 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the output terminals A1o and Uo of module A, the output terminals B1o and Uo of module B, and the output terminals C2o and Uo of module C. A2o is connected to the first output terminal of the isolation device, B2o is connected to the second output terminal of the isolation device, and C1o is connected to the third output terminal of the isolation device. This circuit constitutes a three-phase inverter of the three-level main topology circuit with active neutral clamp. The controller uses the ANPC control algorithm to control the IGBTs in the main circuit topology structure to realize the AC conversion function of the inverter. (14) Operating condition fourteen: The controller enables the pulse conversion module and topology conversion. The pulse conversion module enables the IGBT pulse, and IGBTA21, IGBTA24, IGBTB11, IGBTB14, IGBBTC11, and IGBBTC14 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the output terminals A2o and Uo of module A, the output terminals B1o and Uo of module B, and the output terminals C1o and Uo of module C. A1o is connected to the first output terminal of the isolation device, B2o is connected to the second output terminal of the isolation device, and C2o is connected to the third output terminal of the isolation device. This circuit constitutes a three-phase inverter of the three-level main topology circuit with active neutral clamp. The controller uses the ANPC control algorithm to control the IGBTs in the main circuit topology structure to realize the AC conversion function of the inverter. (15) Operating condition 15: The controller enables the pulse conversion module and topology conversion. The pulse conversion module enables the IGBT pulse, and IGBTA11, IGBTA14, IGBTB21, IGBTB24, IGBBTC11, and IGBBTC14 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the output terminals A1o and Uo of module A, the output terminals B2o and Uo of module B, and the output terminals C1o and Uo of module C. A2o is connected to the first output terminal of the isolation device, B1o is connected to the second output terminal of the isolation device, and C2o is connected to the third output terminal of the isolation device. This circuit constitutes a three-phase inverter of the three-level main topology circuit with active neutral clamp. The controller uses the ANPC control algorithm to control the IGBTs in the main circuit topology structure to realize the AC conversion function of the inverter. (16) Operating condition sixteen, the controller enables the pulse conversion module and topology conversion. The pulse conversion module enables the IGBT pulse, and IGBTA11, IGBTA14, IGBTB21, IGBTB24, IGBBTC21, and IGBBTC24 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the output terminals A1o and Uo of module A, the output terminals B2o and Uo of module B, and the output terminals C2o and Uo of module C. A2o is connected to the first output terminal of the isolation device, B1o is connected to the second output terminal of the isolation device, and C1o is connected to the third output terminal of the isolation device. This circuit constitutes a three-phase inverter of the three-level main topology circuit with active neutral clamp. The controller uses the ANPC control algorithm to control the IGBTs in the main circuit topology structure to realize the AC conversion function of the inverter. (17) Operating Condition 17: The controller enables the pulse conversion module and topology conversion. The pulse conversion module enables the IGBT pulse, and IGBTA21, IGBTA24, IGBTB21, IGBTB24, IGBBTC11, and IGBBTC14 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the output terminals A2o and Uo of module A, the output terminals B2o and Uo of module B, and the output terminals C1o and Uo of module C. A1o is connected to the first output terminal of the isolation device, B1o is connected to the second output terminal of the isolation device, and C2o is connected to the third output terminal of the isolation device. This circuit constitutes a three-phase inverter of the three-level main topology circuit with active neutral clamp. The controller uses the ANPC control algorithm to control the IGBTs in the main circuit topology structure to realize the AC conversion function of the inverter. (18) In operating condition eighteen, the controller enables the pulse conversion module and topology conversion. The pulse conversion module enables the IGBT pulse, and IGBTA21, IGBTA24, IGBTB11, IGBTB14, IGBBTC21, and IGBBTC24 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the output terminals A2o and Uo of module A, the output terminals B1o and Uo of module B, and the output terminals C2o and Uo of module C. A1o is connected to the first output terminal of the isolation device, B2o is connected to the second output terminal of the isolation device, and C1o is connected to the third output terminal of the isolation device. This circuit constitutes a three-phase inverter of the three-level main topology circuit with active neutral clamp. The controller uses the ANPC control algorithm to control the IGBTs in the main circuit topology structure to realize the AC conversion function of the inverter. (19) Operating condition nineteen, the controller enables the pulse conversion module and topology conversion. The pulse conversion module enables the IGBT pulse, and IGBTA21, IGBTA24, IGBTB21, IGBTB24, IGBBTC21, and IGBBTC24 are given a continuous low level. The remaining IGBTs have the ability to transmit high and low levels. The controller controls the topology conversion device 2 to connect the output terminals A2o and Uo of module A, the output terminals B2o and Uo of module B, and the output terminals C2o and Uo of module C. A1o is connected to the first output terminal of the isolation device, B1o is connected to the second output terminal of the isolation device, and C1o is connected to the third output terminal of the isolation device. This circuit constitutes a three-phase inverter of the three-level main topology circuit with active neutral clamp. The controller uses the ANPC control algorithm to control the IGBTs in the main circuit topology structure to realize the AC conversion function of the inverter.

9. The control method for a traction converter with multi-topology transformation as described in claim 8, characterized in that: It also includes (20) settings under normal operating conditions: (a) When the AC conversion load has low requirements for harmonics, a two-level main topology circuit consisting of operating conditions one, two, and three is adopted. When the power is fully loaded, the operating condition one scheme is adopted. When the power is half-loaded or light-loaded, the operating conditions two and three schemes are adopted. When the system is operating in operating condition two and any IGBT breaks down and short-circuits, operating condition two is switched to operating condition three for normal operation. (b) When the AC conversion load has high requirements for harmonics and the intermediate voltage level is high, the diode clamping main circuit topology in operating conditions four to eleven shall be adopted when the IGBT uses Si devices. (c) When the AC conversion load has high requirements for harmonics, the intermediate bus voltage is greater than the withstand voltage rating of the device, and the IGBT uses SiC devices, the active clamping main circuit topology structure consisting of operating conditions twelve to nineteen shall be adopted.

10. The control method for a traction converter with multi-topology transformation as described in claim 8, characterized in that: The AC conversion module consists of four sub-modules: A, B, C, and D. All four sub-modules are identical and employ a redundant design, enabling them to transform into different topologies based on different combinations and to perform different functions and effects according to different operating conditions.

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