Converter based on SiC / Si hybrid ANPC circuit

Abstract

The utility model provides a converter based on a SiC / Si hybrid ANPC circuit. The converter comprises two same traction converter circuits; the traction converter circuit comprises a rectifier module, an inverter module and two support capacitor branches; both the rectifier module and the inverter module adopt an ANPC three-level circuit structure formed by mixing a SiC device and a Si IGBT device; the M nodes of the two traction converter circuits are communicated, and the N nodes of the two traction converter circuits are also communicated. According to the utility model, the three-level circuit is adopted, so that the withstand voltage values of semiconductor switch tubes such as Si IGBT devices and SiC devices can be reduced by half, and therefore, the voltage level of the converter can be further improved to output higher power, and higher power density can be obtained under the condition that the size of the converter is not changed.

Description

Technical Field

[0001] The utility model relates to the technical field of power electronic devices, and in particular to a converter based on a SiC / Si hybrid ANPC circuit. Background Art

[0002] At present, the inverter and rectifier circuits of locomotive traction converters mainly adopt a two-level structure based on Si IGBT devices. As locomotives continue to develop in the direction of high speed and heavy load, the requirements for the power and volume of locomotive converters are getting higher and higher, and the circuit structure of the converter and the semiconductor devices used in the module are the key.

[0003] With the rapid development of semiconductor devices, wide bandgap semiconductor devices SiC and GaN have received great attention and research due to their advantages such as high power density, high switching frequency, low junction temperature and low switching loss compared to Si IGBT and other devices. Among them, SiC devices have higher withstand voltage than GaN devices and are suitable for high-power power systems, especially in the field of rail transit converters, where they have considerable application scenarios.

[0004] Compared with the traditional two-level inverter and rectifier circuit, the three-level circuit has been widely used in fields such as grid-connected photovoltaic inverters due to its lower output voltage harmonics and higher withstand voltage performance. At present, the three-level circuit structure is gradually being used in the field of rail transportation to replace the traditional two-level structure to increase the power upper limit of the converter and obtain a better output voltage waveform. At the same time, compared with the NPC (Neutral Point Clamped) three-level structure, the use of the ANPC (Active Neutral Point Clamped) three-level circuit structure can make the loss distribution of each bridge arm switch tube more uniform, which is beneficial to the heat dissipation of the module and the reliability of the converter.

[0005] Although SiC devices have many advantages, they also have the disadvantage of high device cost. In order to reduce costs, various SiC / Si hybrid three-level circuit topologies have emerged. The more representative ones are TNPC and ANPC circuit topologies. At present, the comprehensive performance and cost of ANPC circuit are the best, and it has a reliable application scenario in the field of rail transit high-power converters. Utility Model Content

[0006] In order to solve the technical problem that rail transit has increasingly higher performance requirements for traction converters, the utility model proposes a converter based on a SiC / Si hybrid ANPC circuit.

[0007] According to a first aspect of the present embodiment, a converter based on a SiC / Si hybrid ANPC circuit is provided, comprising two identical traction converter circuits; the traction converter circuit comprises a rectifier module and an inverter module; the rectifier module and the inverter module both adopt an ANPC three-level circuit structure that is a mixture of SiC devices and Si IGBT devices;

[0008] The first end of the single bridge arm of the rectifier module is connected to the AC1 node, and the AC1 node is connected to the secondary side of the traction main transformer; the second end of the single bridge arm of the rectifier module is connected to the P node, and the third end of the single bridge arm of the rectifier module is connected to the N node; the fourth end of the single bridge arm of the rectifier module is connected to the M node;

[0009] The first end of the single bridge arm of the inverter module is connected to the P node; the second end of the single bridge arm of the inverter module is connected to the M node; the third end of the single bridge arm of the inverter module is connected to the N node; the fourth end of the single bridge arm of the inverter module is connected to the AC traction motor;

[0010] The traction converter circuit further includes two supporting capacitor branches, each supporting capacitor branch includes two supporting capacitors connected in sequence, a first end of a first supporting capacitor and a first end of a second supporting capacitor in each supporting capacitor branch are both connected to the M node, a second end of the first supporting capacitor is connected to the P node, and a second end of the second supporting capacitor is connected to the N node;

[0011] The M nodes of the two traction converter circuits are connected, and the N nodes of the two traction converter circuits are also connected.

[0012] In some implementations, a single bridge arm of the rectifier module includes a first Si IGBT device, a second Si IGBT device, a first branch, and a second branch; the first end of the first Si IGBT device is connected to the P node, the first end of the first branch and the first end of the second branch are both connected to the second end of the first Si IGBT device; the second end of the first branch and the second end of the second branch are both connected to the first end of the second Si IGBT device; the second end of the second Si IGBT device is connected to the N node; the first branch includes a third Si IGBT device T3 and a fourth Si IGBT device connected in sequence, and the middle node between the third Si IGBT device and the fourth Si IGBT device is connected to the M node; the second branch includes a first SiC device and a second SiC device connected in sequence, and the middle node between the first SiC device and the second SiC device is connected to the AC1 node; the first SiC device and the second SiC device are three SiC devices connected in parallel;

[0013] A single bridge arm of the inverter module includes a third SiC device, a fourth SiC device, a third branch and a fourth branch; the first end of the third SiC device is connected to the P node, the first end of the third branch and the first end of the fourth branch are both connected to the second end of the third SiC device; the second end of the third branch and the second end of the fourth branch are both connected to the first end of the fourth SiC device; the second end of the fourth SiC device is connected to the N node; the third branch includes a fifth SiC device and a sixth SiC device connected in sequence, and the intermediate node between the fifth SiC device and the sixth SiC device is connected to the M node; the fourth branch includes a fifth Si IGBT device and a sixth Si IGBT device connected in sequence, and the intermediate node between the fifth Si IGBT device and the sixth Si IGBT device is connected to the AC traction motor.

[0014] In some implementations, the converter further includes a ground detection circuit shared by two identical traction converter circuits, the ground detection circuit including a first ground detection circuit and a second ground detection circuit;

[0015] The first grounding detection circuit includes a first voltage sensor, a second voltage sensor, a semi-grounded capacitor, a first fixed discharge resistor and a second fixed discharge resistor; the first end of the first voltage sensor, the first end of the second voltage sensor, and the first end of the first fixed discharge resistor are connected to the P node in any traction converter circuit; the second end of the second voltage sensor, the second end of the semi-grounded capacitor, the second end of the first fixed discharge resistor, and the first end of the second fixed discharge resistor are all connected to the power supply end; the second end of the first voltage sensor, the second end of the semi-grounded capacitor, and the second end of the second fixed discharge resistor are all connected to the N node;

[0016] The second grounding detection circuit includes four neutral point grounding resistors, a neutral point grounding capacitor and a ninth current sensor; the first end of the first neutral point grounding resistor, the first end of the second neutral point grounding resistor and the first end of the neutral point grounding capacitor are all connected to the M node; the second end of the first neutral point grounding resistor, the second end of the second neutral point grounding resistor, the first end of the third neutral point grounding resistor and the first end of the fourth neutral point grounding resistor are connected; the second end of the neutral point grounding capacitor, the second end of the third neutral point grounding resistor and the second end of the fourth neutral point grounding resistor are all connected to the first end of the ninth current sensor; the second end of the ninth current sensor is grounded.

[0017] In some implementations, a shared secondary filter circuit is provided between the two traction conversion circuits, and the secondary filter circuit includes a seventh fixed discharge resistor, an eighth fixed discharge resistor, a capacitor branch and a filter inductor; the capacitor branch includes six capacitors connected in sequence; the first end of the filter inductor is connected to the first end of the capacitor branch; the second end of the seventh fixed discharge resistor is connected to the first end of the eighth fixed discharge resistor; the second end of the capacitor branch and the second end of the eighth fixed discharge resistor are both connected to the N node, and the second end of the filter inductor is connected to the P node in any one of the traction conversion circuits.

[0018] In some implementations, the traction inverter circuit further includes an indicator light, a first end of the indicator light is connected to a P node in the traction inverter circuit; a second end of the indicator light is connected to an N node in the traction inverter circuit.

[0019] In some implementations, the traction converter circuit further includes a pre-charging loop, a first end of the pre-charging loop is connected to a first end of a secondary side of the traction main transformer, and a second end of the pre-charging loop is connected to an AC1 node.

[0020] In some implementations, the converter further includes a fixed discharge circuit, the fixed discharge circuit including a ninth fixed discharge resistor, a tenth fixed discharge resistor, an eleventh fixed discharge resistor, a twelfth fixed discharge resistor, and a seventh fixed discharge resistor and an eighth fixed discharge resistor shared with the secondary filtering circuit, and a first fixed discharge resistor and a second fixed discharge resistor shared with the first ground detection circuit;

[0021] The first end of the ninth fixed discharge resistor is connected to the P node in the first traction converter circuit; the second end of the ninth fixed discharge resistor and the first end of the tenth fixed discharge resistor are both connected to the M node; the second end of the tenth fixed discharge resistor is connected to the N node;

[0022] The first end of the eleventh fixed discharge resistor is connected to the P node in the second traction converter circuit; the second end of the eleventh fixed discharge resistor and the first end of the twelfth fixed discharge resistor are both connected to the M node; the second end of the twelfth fixed discharge resistor is connected to the N node.

[0023] In some implementations, the traction converter circuit further includes a chopper circuit, a first terminal of the chopper circuit is connected to a P node, and a second terminal of the chopper circuit is connected to an N node.

[0024] In some implementations, the converter also includes current sensors for monitoring the input current of the traction conversion circuit, the output current of the inverter module, and the chopping current of the chopper circuit respectively; the converter also includes a voltage sensor for monitoring the neutral point to positive and negative pole voltages; the voltage sensor and the current sensor are both connected to the TCU chassis.

[0025] In some implementations, the converter is disposed in an equipment cabinet, a flat liquid cooling radiator is disposed in the equipment cabinet, and a cooling fan is also disposed in the equipment cabinet.

[0026] Compared with the prior art, the embodiments of the present disclosure have at least the following beneficial effects:

[0027] (1) Compared with the two-level circuit structure, the three-level circuit can reduce the withstand voltage of semiconductor switch tubes such as Si IGBT devices and SiC devices by half, so that the converter can further increase the voltage level to output higher power, and obtain higher power density without changing the converter volume.

[0028] (2) The use of SiC devices can significantly increase the switching frequency. At the same time, the voltage harmonics output by the three-level circuit structure are relatively low, further improving the grid-side harmonic level and the motor harmonic level.

[0029] (3) SiC devices are small in size, which can reduce the size of the rectifier module and inverter module. At the same time, their high switching frequency can reduce the size and weight of the filter components, thereby reducing the size and weight of the converter.

[0030] (4) The use of the ANPC circuit structure can evenly distribute the inverter losses to each device, thereby reducing the thermal stress on SiC devices and Si IGBT devices and further improving the thermal life of the power module.

[0031] (5) Due to the low switching voltage stress, the voltage change rate dv / dt is small, and EMI (Electromagnetic Interference) will be lower. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0033] Figure 1 is a schematic diagram of a single bridge arm of a rectifier module provided in an embodiment of the present disclosure;

[0034] Figure 2 is a schematic diagram of a single bridge arm of an inverter module provided in an embodiment of the present disclosure;

[0035] Figure 3 A schematic diagram of a ground detection circuit provided in an embodiment of the present disclosure;

[0036] Figure 4 A schematic diagram of a secondary filtering circuit provided in an embodiment of the present disclosure;

[0037] Figure 5 A schematic diagram of a converter provided in an embodiment of the present disclosure;

[0038] Figure 6 A schematic diagram of an inverter PWM modulation strategy for an ANPC three-level circuit structure provided in an embodiment of the present disclosure;

[0039] Figure 7 A schematic diagram of a commutation path when the load current is in the positive switching state P and OL provided in an embodiment of the present disclosure;

[0040] Figure 8 A schematic diagram of the commutation paths of switch states P and OL when the load current is negative provided in an embodiment of the present disclosure;

[0041] Fig. 9 A schematic diagram of a commutation path of OU and N when the load current is in the positive switching state provided by an embodiment of the present disclosure;

[0042] Fig.10 A schematic diagram of the commutation path of switch states OU and N when the load current is negative provided in an embodiment of the present disclosure;

[0043] Fig.11 A schematic diagram of a liquid cooling radiator provided in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0044] The technical scheme in the embodiment of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiment of the utility model. Obviously, the described embodiment is only a part of the embodiment of the utility model, rather than all the embodiments. The components of the embodiment of the utility model generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiment of the utility model provided in the drawings is not intended to limit the scope of the utility model claimed for protection, but merely represents the selected embodiment of the utility model. Based on the embodiment of the utility model, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the utility model.

[0045] This embodiment provides a converter based on a SiC / Si hybrid ANPC (Active Neutral Point Clamped) circuit. By combining the ANPC three-level circuit structure based on a mixture of SiC (Silicon Carbide) devices and Si IGBT (insulated Gate Bipolar Transistor, an insulated gate bipolar transistor, a power electronic power switching device) devices with the mature traction converter system in the current locomotive field, the high frequency of the converter is achieved, the grid-side harmonic level and the motor harmonic level are further improved, and the dynamic response capability of the converter to load fluctuations and grid disturbances is enhanced. At the same time, the power density of the converter is further improved, which can make the converter have a higher power output capacity. Specifically, the converter provided in this embodiment includes two identical traction converter circuits. The traction converter circuit includes a rectifier module and an inverter module; the rectifier module and the inverter module both adopt an ANPC three-level circuit structure mixed with SiC devices and SiIGBT devices.

[0046] The first end of the single bridge arm of the rectifier module is connected to the AC1 node, and the AC1 node is connected to the secondary side of the traction main transformer; the second end of the single bridge arm of the rectifier module is connected to the P node, and the third end of the single bridge arm of the rectifier module is connected to the N node; the fourth end of the single bridge arm of the rectifier module is connected to the M node.

[0047] The first end of the single bridge arm of the inverter module is connected to the P node; the second end of the single bridge arm of the inverter module is connected to the M node; the third end of the single bridge arm of the inverter module is connected to the N node; and the fourth end of the single bridge arm of the inverter module is connected to the AC traction motor.

[0048] The traction converter circuit also includes two supporting capacitor branches, each supporting capacitor branch includes two supporting capacitors connected in sequence, the first end of the first supporting capacitor and the first end of the second supporting capacitor in each supporting capacitor branch are both connected to the M node, the second end of the first supporting capacitor is connected to the P node, and the second end of the second supporting capacitor is connected to the N node.

[0049] The M nodes of the two traction converter circuits are connected, and the N nodes of the two traction converter circuits are also connected.

[0050] The converter provided in this embodiment has the following advantages: (1) Compared with the two-level circuit structure, the three-level circuit can reduce the withstand voltage of the semiconductor switch by half, so that the converter can further increase the voltage level to output higher power, and can obtain higher power density while keeping the volume lower. (2) By adopting SiC devices, the switching frequency can be greatly increased, and the voltage harmonics output by the three-level circuit structure are low, further improving the grid-side harmonic level and motor harmonic level. (3) The small size of SiC devices can reduce the volume of the module, and the high switching frequency can reduce the volume and weight of the filter device, thereby reducing the volume and weight of the converter. (4) The ANPC circuit structure can make the inverter loss balanced and distributed to each device, so that the thermal stress of SiC devices and Si IGBT devices is small, further improving the thermal life of the power module. (5) Due to the low switching voltage stress, the voltage change rate dv / dt is small, and EMI (Electromagnetic Interference) will be lower.

[0051] like Figure 1 As shown, a single bridge arm of the rectifier module includes a first Si IGBT device T1, a second Si IGBT device T2, a first branch and a second branch; the first end of the first Si IGBT device T1 is connected to the P node, and the first end of the first branch and the first end of the second branch are both connected to the second end of the first Si IGBT device T1; the second end of the first branch and the second end of the second branch are both connected to the first end of the second Si IGBT device T2; the second end of the second Si IGBT device T2 is connected to the N node; the first branch includes a third Si IGBT device T3 and a fourth Si IGBT device T4 connected in sequence, and the middle node between the third Si IGBT device T3 and the fourth Si IGBT device T4 is connected to the M node; the second branch includes a first SiC device Q1 and a second SiC device Q2 connected in sequence, and the middle node between the first SiC device Q1 and the second SiC device Q2 is connected to the AC1 node; the first SiC device Q1 and the second SiC device Q2 are three SiC devices connected in parallel.

[0052] like Figure 2As shown, a single bridge arm of the inverter module includes a third SiC device Q3, a fourth SiC device Q4, a third branch and a fourth branch; the first end of the third SiC device Q3 is connected to the P node, and the first end of the third branch and the first end of the fourth branch are both connected to the second end of the third SiC device Q3; the second end of the third branch and the second end of the fourth branch are both connected to the first end of the fourth SiC device Q4; the second end of the fourth SiC device Q4 is connected to the N node; the third branch includes a fifth SiC device T5 and a sixth SiC device T6 connected in sequence, and the intermediate node between the fifth SiC device T5 and the sixth SiC device T6 is connected to the M node; the fourth branch includes a fifth Si IGBT device T5 and a sixth Si IGBT device T6 connected in sequence, and the intermediate node between the fifth Si IGBT device T5 and the sixth Si IGBT device T6 is connected to the AC traction motor.

[0053] In some embodiments, Figure 5 As shown, the traction converter circuit further includes a pre-charging loop, a first end of the pre-charging loop is connected to a first end of the secondary side of the traction main transformer, and a second end of the pre-charging loop is connected to an AC1 node. The pre-charging loop can prevent the converter from having an excessively large inrush current when it is just started, thereby preventing damage to the supporting capacitor of the intermediate DC circuit of the converter.

[0054] In some embodiments, the converter further includes a ground detection circuit shared by two identical traction converter circuits, and the ground detection circuit includes a first ground detection circuit and a second ground detection circuit.

[0055] like Figure 3 As shown in (b), the first grounding detection circuit includes a first voltage sensor VH1, a second voltage sensor VH2, a semi-grounded capacitor CM1, a first fixed discharge resistor R5 and a second fixed discharge resistor R6; the first end of the first voltage sensor VH1, the first end of the second voltage sensor VH2, and the first end of the first fixed discharge resistor R5 are connected to the P node in any traction converter circuit; the second end of the second voltage sensor VH2, the second end of the semi-grounded capacitor CM1, the second end of the first fixed discharge resistor R5, and the first end of the second fixed discharge resistor R6 are all connected to the power supply end; the second end of the first voltage sensor VH1, the second end of the semi-grounded capacitor CM1, and the second end of the second fixed discharge resistor R6 are all connected to the N node. The voltage monitored by the first voltage sensor VH1 is recorded as the full voltage VH1, and the voltage monitored by the second voltage sensor VH2 is recorded as the half voltage VH2. The fifth fixed discharge resistor R5 and the sixth fixed discharge resistor R6 act as a voltage divider. When When it is greater than a preset first threshold, it can be determined that the intermediate circuit is grounded.

[0056] like Figure 3 As shown in (a), the second grounding detection circuit includes four neutral point grounding resistors RG1 to RG4, a neutral point grounding capacitor CG1 and a ninth current sensor LH9; the first end of the first neutral point grounding resistor RG1, the first end of the second neutral point grounding resistor RG2 and the first end of the neutral point grounding capacitor CG1 are all connected to the M node; the second end of the first neutral point grounding resistor RG1, the second end of the second neutral point grounding resistor RG2, the first end of the third neutral point grounding resistor RG3 and the first end of the fourth neutral point grounding resistor RG4 are connected; the second end of the neutral point grounding capacitor CG1, the second end of the third neutral point grounding resistor RG3 and the second end of the fourth neutral point grounding resistor RG4 are all connected to the first end of the ninth current sensor LH9; the second end of the ninth current sensor LH9 is grounded. When the current detected by the ninth current sensor LH9 is greater than the preset second threshold value, it can also be determined that the intermediate circuit is grounded.

[0057] In some embodiments, a shared secondary filter circuit is provided between the two traction converter circuits. The secondary filter circuit can filter out the secondary harmonics in the intermediate DC circuit and improve the output waveform quality. Figure 4 As shown, the secondary filtering circuit includes a seventh fixed discharge resistor R7, an eighth fixed discharge resistor R8, a capacitor branch and a filter inductor; the capacitor branch includes six capacitors C21 to C26 connected in sequence; the first end L1.2 of the filter inductor is connected to the first end of the capacitor branch; the second end of the seventh fixed discharge resistor R7 and the first end of the eighth fixed discharge resistor R8; the second end of the capacitor branch and the second end of the eighth fixed discharge resistor R8 are both connected to the N node, and the second end L1.1 of the filter inductor is connected to the P node in any traction converter circuit.

[0058] In some implementations, the traction converter circuit further includes a chopper circuit, a first terminal of the chopper circuit is connected to a P node, and a second terminal of the chopper circuit is connected to an N node.

[0059] For example, Figure 5 As shown, the converter includes two traction converter circuits, the fixed discharge circuit, and the secondary filter circuit and the ground detection circuit shared by the two traction converter circuits. Both traction converter circuits include the pre-charging circuit, the rectifier module, the chopper circuit, the inverter module, and indicator lights LED1 and LED2. The first end of the indicator light is connected to the P node in the traction converter circuit; the second end of the indicator light is connected to the N node in the traction converter circuit. When there is an unsafe voltage in the converter, the indicator lights LED1 and LED2 will light up to warn.

[0060] The rectifier module adopts a two-phase rectifier circuit with two circuit bridge arms, which can rectify the two-phase AC on the secondary side of the traction main transformer into a DC voltage to charge the intermediate DC circuit. The inverter module is a three-phase inverter circuit with three circuit bridge arms, which can convert the input intermediate DC voltage into three-phase AC power and output it to the AC traction motor for operation.

[0061] like Figure 5 As shown, the chopper circuit includes a chopper resistor Rch1, a seventh switch tube Q7 and an eighth switch tube Q8, the first end of the seventh switch tube Q7 is connected to the P node, the second end of the seventh switch tube Q7 and the first end of the eighth switch tube Q8 are connected to the first end of the chopper resistor Rch1; the second end of the eighth switch tube Q8 and the second end of the chopper resistor Rch1 are connected to the N node. In this embodiment, the seventh switch tube Q7 and the eighth switch tube Q8 are both SiCIGBT devices. When the converter fails, the SiC IGBT device of the chopper bridge arm can be turned on, so that the intermediate loop current is quickly discharged by the chopper resistor Rch1, and the remaining electric energy of the two intermediate DC loops can be discharged to below the safe voltage within 1s.

[0062] The fixed discharge circuit includes a ninth fixed discharge resistor R9, a tenth fixed discharge resistor R10, an eleventh fixed discharge resistor R11, a twelfth fixed discharge resistor R12, a seventh fixed discharge resistor R7 and an eighth fixed discharge resistor R8 shared with the secondary filter circuit, and a first fixed discharge resistor R5 and a second fixed discharge resistor R6 shared with the first ground detection circuit. The first end of the ninth fixed discharge resistor R9 is connected to the P node in the first traction converter circuit; the second end of the ninth fixed discharge resistor R9 and the first end of the tenth fixed discharge resistor R10 are both connected to the M node; the second end of the tenth fixed discharge resistor R10 is connected to the N node. The first end of the eleventh fixed discharge resistor R11 is connected to the P node in the second traction converter circuit; the second end of the eleventh fixed discharge resistor R11 and the first end of the twelfth fixed discharge resistor R12 are both connected to the M node; the second end of the twelfth fixed discharge resistor R12 is connected to the N node. The fixed discharge resistors in the fixed discharge circuit can discharge the remaining electric energy of the two intermediate DC circuits to below the safe voltage by slowly discharging when the converter stops working.

[0063] The inverter PWM (Pulse-Width Modulation) modulation strategy of the ANPC three-level circuit structure is as follows Figure 6 As shown in Table 1, in the positive half cycle of the modulation wave, Q3 and Q6 are always on, Q4 and Q5 are always off, and T5 and T6 are alternately turned on. In the negative half cycle of the modulation wave, Q4 and Q5 are always on, Q3 and Q6 are always off, and T5 and T6 are alternately turned on.

[0064] When the switch state is P, Q3, T5, and Q6 are turned on, and the current flows from P→Q3→T5→output point. When the load current is negative, the path is opposite, and the output voltage is 0.5Udc, where Udc is the DC bus voltage. Figure 7 and Figure 8 shown.

[0065] When the switch state is OL, Q3, T6, and Q6 are turned on, and the current flows from M→Q6→T6→output point. When the load current is negative, the path is opposite, and the output voltage is 0. Figure 7 and Figure 8 shown.

[0066] When the switch state is OU, Q4, T5, and Q5 are turned on, and the current flows from P→Q5→T5→output point. When the load current is negative, the path is opposite, and the output voltage is 0. Fig. 9 and Fig.10 shown.

[0067] When the switch state is N, Q4, T6, and Q5 are turned on, and the current flows from N→Q4→T6→output point. When the load current is negative, the path is opposite, and the output voltage is -0.5Udc. Fig. 9 and Fig.10 shown.

[0068] Table 1 Three-level status

[0069] Switch Status Q3 T5 T6 Q4 Q5 Q6 Output point level P 1 1 0 0 0 1 <![CDATA[0.5U dc ]]> OU 0 1 0 1 1 0 0 OL 1 0 1 0 0 1 0 N 0 0 1 1 1 0 <![CDATA[-0.5U dc ]]>

[0070] The converter provided in this embodiment has the following functions:

[0071] (1) Braking function: The principle is as follows: When the locomotive is in braking condition, the inverter module is used as a rectifier module to rectify the current of the AC traction motor into a DC voltage and charge it to the intermediate DC circuit. At this time, the rectifier module is used as an inverter module to invert the DC power of the intermediate DC circuit into a two-phase AC voltage and feed it back to the power grid.

[0072] (2) Traction inverter function: its principle is: under traction conditions, the single-phase AC output of the traction main transformer is converted into DC through the four-quadrant rectifier module in the converter to supply power to the intermediate DC circuit of the converter. Under the control of the Traction Control Unit (TCU), the inverter unit inverts the DC power of the intermediate circuit into three-phase frequency-adjustable AC power to drive the AC traction motor.

[0073] In another embodiment, the two rectifier modules and the two inverter modules of the converter are cooled by liquid cooling circulation. Fig.11The flat liquid cooling radiator shown can evenly take away the heat generated by the semiconductor devices in the converter, thereby reducing the thermal stress on the SiC devices and SiIGBT devices, further improving the thermal life of the power module. At the same time, a high-power cooling fan is installed in the equipment cabinet, which can effectively drive the thermal cycle of the busbars, capacitors, resistors, contactors, sensors and other small-power devices in the equipment cabinet, ensuring the thermal reliability of the entire converter.

[0074] The key components of the converter, such as contactors, modules, capacitors, resistors, etc., are all arranged on the front side of the cabinet door for easy maintenance and replacement, making the converter more maintainable and smaller in size.

[0075] In another embodiment, the converter further includes current sensors for monitoring the input current of the traction converter circuit, the output current of the inverter module, and the chopping current of the chopper circuit. The converter further includes voltage sensors for monitoring the voltage of the neutral point to the positive and negative poles. Both the voltage sensor and the current sensor are connected to the TCU chassis. When these monitoring values ​​are abnormal, the TCU (Traction Control Unit) chassis will determine that a fault has occurred and take corresponding actions in time to protect the converter and devices such as loads connected to the converter.

[0076] For example, Figure 5 As shown, the converter further includes a first current sensor LH1, a second current sensor LH2, a third current sensor LH3, a fourth current sensor LH4, a fifth current sensor LH5, a sixth current sensor LH6, a seventh current sensor LH7 and an eighth current sensor LH8. The first current sensor LH1 is used to monitor the input current of the first traction converter circuit. The second current sensor LH2 is used to monitor the input current of the second traction converter circuit. The third current sensor LH3 is used to monitor the output current of the A phase line of the inverter module in the first traction converter circuit. The fourth current sensor LH4 is used to monitor the output current of the B phase line of the inverter module in the first traction converter circuit. The fifth current sensor LH5 is used to monitor the output current of the A phase line of the inverter module in the second traction converter circuit. The sixth current sensor LH6 is used to monitor the output current of the B phase line of the inverter module in the second traction converter circuit. The seventh current sensor LH7 is used to monitor the chopping current of the chopping circuit in the first traction converter circuit. The eighth current sensor LH8 is used to monitor the chopping current of the chopping circuit in the second traction converter circuit. The converter further comprises a third voltage sensor VH3 and a fourth voltage sensor VH4. The third voltage sensor VH3 and the fourth voltage sensor VH4 are both used to monitor the voltage between the neutral point and the negative electrode of the converter.

[0077] It should be noted that, in this article, the terms "first", "second", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. The terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0078] The above descriptions are only some preferred embodiments of the present disclosure and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the utility model involved in the embodiments of the present disclosure is not limited to the technical solutions formed by the specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the above-mentioned utility model concept. For example, the above-mentioned features are replaced with the technical features with similar functions disclosed in the embodiments of the present disclosure (but not limited to) to form a technical solution.

Claims

1. A converter based on SiC / Si hybrid ANPC circuit, characterized in that: It comprises two identical traction converter circuits; the traction converter circuit comprises a rectifier module and an inverter module; the rectifier module and the inverter module both adopt an ANPC three-level circuit structure mixed with SiC devices and Si IGBT devices; The first end of the single bridge arm of the rectifier module is connected to the AC1 node, and the AC1 node is connected to the secondary side of the traction main transformer; the second end of the single bridge arm of the rectifier module is connected to the P node, and the third end of the single bridge arm of the rectifier module is connected to the N node; the fourth end of the single bridge arm of the rectifier module is connected to the M node; The first end of the single bridge arm of the inverter module is connected to the P node; the second end of the single bridge arm of the inverter module is connected to the M node; the third end of the single bridge arm of the inverter module is connected to the N node; the fourth end of the single bridge arm of the inverter module is connected to the AC traction motor; The traction converter circuit further includes two supporting capacitor branches, each supporting capacitor branch includes two supporting capacitors connected in sequence, a first end of a first supporting capacitor and a first end of a second supporting capacitor in each supporting capacitor branch are both connected to the M node, a second end of the first supporting capacitor is connected to the P node, and a second end of the second supporting capacitor is connected to the N node; The M nodes of the two traction converter circuits are connected, and the N nodes of the two traction converter circuits are also connected.

2. The converter based on SiC / Si hybrid ANPC circuit according to claim 1, characterized in that: A single bridge arm of the rectifier module comprises a first Si IGBT device (T1), a second Si IGBT device (T2), a first branch and a second branch; the first end of the first Si IGBT device (T1) is connected to the P node, the first end of the first branch and the first end of the second branch are both connected to the second end of the first Si IGBT device (T1); the second end of the first branch and the second end of the second branch are both connected to the first end of the second Si IGBT device (T2); the second end of the second Si IGBT device (T2) is connected to the N node; the first branch comprises a third Si IGBT device (T3) and a fourth Si IGBT device (T4) connected in sequence, and the middle node between the third Si IGBT device (T3) and the fourth Si IGBT device (T4) is connected to the M node; the second branch comprises a first SiC device (Q1) and a second SiC device (Q2) connected in sequence, and the middle node between the first SiC device (Q1) and the second SiC device (Q2) is connected to the AC1 node; the first SiC device (Q1) and the second SiC device (Q2) are three SiC devices connected in parallel; A single bridge arm of the inverter module comprises a third SiC device (Q3), a fourth SiC device (Q4), a third branch and a fourth branch; the first end of the third SiC device (Q3) is connected to the P node, the first end of the third branch and the first end of the fourth branch are both connected to the second end of the third SiC device (Q3); the second end of the third branch and the second end of the fourth branch are both connected to the first end of the fourth SiC device (Q4); the second end of the fourth SiC device (Q4) is connected to the N node; the third branch comprises a fifth SiC device (T5) and a sixth SiC device (T6) connected in sequence, and the middle node between the fifth SiC device (T5) and the sixth SiC device (T6) is connected to the M node; the fourth branch comprises a fifth Si IGBT device (T5) and a sixth Si IGBT device (T6) connected in sequence, and the middle node between the fifth Si IGBT device (T5) and the sixth Si IGBT device (T6) is connected to the AC traction motor.

3. The converter based on SiC / Si hybrid ANPC circuit according to claim 1, characterized in that: The converter further comprises a ground detection circuit shared by two identical traction converter circuits, wherein the ground detection circuit comprises a first ground detection circuit and a second ground detection circuit; The first grounding detection circuit comprises a first voltage sensor (VH1), a second voltage sensor (VH2), a semi-grounded capacitor (CM1), a first fixed discharge resistor (R5) and a second fixed discharge resistor (R6); a first end of the first voltage sensor (VH1), a first end of the second voltage sensor (VH2) and a first end of the first fixed discharge resistor (R5) are connected to a P node in any branch traction converter circuit; a second end of the second voltage sensor (VH2), a second end of the semi-grounded capacitor (CM1), a second end of the first fixed discharge resistor (R5) and a first end of the second fixed discharge resistor (R6) are all connected to a power supply terminal; a second end of the first voltage sensor (VH1), a second end of the semi-grounded capacitor (CM1) and a second end of the second fixed discharge resistor (R6) are all connected to an N node; The second grounding detection circuit includes four neutral point grounding resistors (RG1 to RG4), a neutral point grounding capacitor (CG1) and a ninth current sensor (LH9); the first end of the first neutral point grounding resistor (RG1), the first end of the second neutral point grounding resistor (RG2) and the first end of the neutral point grounding capacitor (CG1) are all connected to the M node; the second end of the first neutral point grounding resistor (RG1), the second end of the second neutral point grounding resistor (RG2), the first end of the third neutral point grounding resistor (RG3) and the first end of the fourth neutral point grounding resistor (RG4) are connected; the second end of the neutral point grounding capacitor (CG1), the second end of the third neutral point grounding resistor (RG3) and the second end of the fourth neutral point grounding resistor (RG4) are all connected to the first end of the ninth current sensor (LH9); the second end of the ninth current sensor (LH9) is grounded.

4. The converter based on SiC / Si hybrid ANPC circuit according to claim 3, characterized in that: A shared secondary filtering circuit is also provided between the two traction converter circuits, the secondary filtering circuit comprising a seventh fixed discharge resistor (R7), an eighth fixed discharge resistor (R8), a capacitor branch and a filter inductor; the capacitor branch comprises six capacitors (C21 to C26) connected in sequence; the first end (L1.2) of the filter inductor is connected to the first end of the capacitor branch; the second end of the seventh fixed discharge resistor (R7) and the first end of the eighth fixed discharge resistor (R8); the second end of the capacitor branch and the second end of the eighth fixed discharge resistor (R8) are both connected to the N node, and the second end (L1.1) of the filter inductor is connected to the P node in any traction converter circuit.

5. The converter based on SiC / Si hybrid ANPC circuit according to claim 1, characterized in that: The traction inverter circuit also includes indicator lights (LED1, LED2), a first end of the indicator lights is connected to a P node in the traction inverter circuit; a second end of the indicator lights is connected to an N node in the traction inverter circuit.

6. The converter based on SiC / Si hybrid ANPC circuit according to claim 1, characterized in that: The traction converter circuit further includes a pre-charging loop, a first end of the pre-charging loop is connected to a first end of a secondary side of the traction main transformer, and a second end of the pre-charging loop is connected to an AC1 node.

7. The converter based on SiC / Si hybrid ANPC circuit according to claim 4, characterized in that: It also includes a fixed discharge circuit, the fixed discharge circuit including a ninth fixed discharge resistor (R9), a tenth fixed discharge resistor (R10), an eleventh fixed discharge resistor (R11), a twelfth fixed discharge resistor (R12), a seventh fixed discharge resistor (R7) and an eighth fixed discharge resistor (R8) shared with the secondary filter circuit, and a first fixed discharge resistor (R5) and a second fixed discharge resistor (R6) shared with the first ground detection circuit; A first end of a ninth fixed discharge resistor (R9) is connected to a P node in the first traction converter circuit; a second end of the ninth fixed discharge resistor (R9) and a first end of a tenth fixed discharge resistor (R10) are both connected to an M node; and a second end of the tenth fixed discharge resistor (R10) is connected to an N node; The first end of the eleventh fixed discharge resistor (R11) is connected to the P node in the second traction converter circuit; the second end of the eleventh fixed discharge resistor (R11) and the first end of the twelfth fixed discharge resistor (R12) are both connected to the M node; and the second end of the twelfth fixed discharge resistor (R12) is connected to the N node.

8. The converter based on SiC / Si hybrid ANPC circuit according to claim 4, characterized in that: The traction converter circuit further includes a chopper circuit, a first terminal of the chopper circuit is connected to a P node, and a second terminal of the chopper circuit is connected to an N node.

9. The converter based on SiC / Si hybrid ANPC circuit according to claim 8, characterized in that: The converter also includes current sensors for monitoring the input current of the traction conversion circuit, the output current of the inverter module, and the chopping current of the chopping circuit respectively; the converter also includes a voltage sensor for monitoring the neutral point to positive and negative pole voltages; the voltage sensor and the current sensor are both connected to the TCU chassis.

10. The converter based on SiC / Si hybrid ANPC circuit according to any one of claims 1 to 9, characterized in that: The converter is arranged in an equipment cabinet, a flat liquid cooling radiator is arranged in the equipment cabinet, and a cooling fan is also arranged in the equipment cabinet.

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