Frequency converter
By designing a frequency converter that uses a transformer cabinet to drive the power cabinets on both sides to work alternately, the problem of energy waste caused by the long stator track of the linear motor is solved, achieving the effects of compact structure, high power density and low cost.
Patent Information
- Application Number
- CN202422798534.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-15
- Publication Date
- 2025-11-14
- Estimated Expiration
- 2034-11-15
AI Technical Summary
In existing technologies, the stator track of linear motors is relatively long, resulting in high power supply loss for the entire stator section. Furthermore, two frequency converters are required to drive the two stator sections separately, which increases costs.
Design a frequency converter that uses a transformer cabinet to drive two power cabinets to work alternately. It connects to the two stator sections of a linear motor through a set of three-phase outputs and controls time-sharing power supply through an output switch cabinet. This reduces the number of frequency converters, resulting in a compact structure, high power density, and low cost.
It achieves energy savings, reduces equipment costs, improves system reliability and efficiency, and features a compact structure and high power density.
Smart Images
Figure CN223553211U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of power control equipment technology, and in particular to a frequency converter. Background Technology
[0002] A frequency converter is a power control device that controls a motor by changing the frequency of the motor's operating power supply.
[0003] Because the stator track of existing linear motors is relatively long, the power supply loss to the entire stator section is significant. To save energy, it is usually chosen to segment the stator of the linear motor, dividing the entire track into two stator sections. Power is supplied to the stator section where the mover moves. After segmenting the stator, it is necessary to provide time-sharing power to the stator of each section of the three-phase windings.
[0004] Because existing frequency converters can only drive one set of three-phase windings, two frequency converters are usually required to perform time-sharing power supply control on the two stator sections respectively. The entire traction system equipment requires two frequency converters to drive, which is costly. Utility Model Content
[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a frequency converter with a compact structure, high power density, and low cost, thereby solving the aforementioned technical problems.
[0006] A frequency converter includes: a frequency conversion unit, the frequency conversion unit including a transformer cabinet, a first power cabinet, a second power cabinet, a third power cabinet, a first output switch cabinet, and a first control cabinet arranged sequentially on the left side of the transformer cabinet; the frequency conversion unit further includes a fourth power cabinet, a fifth power cabinet, a sixth power cabinet, a second output switch cabinet, and a second control cabinet arranged sequentially on the right side of the transformer cabinet, the output terminal of the transformer cabinet being electrically connected to the input terminals of the first power cabinet, the second power cabinet, the third power cabinet, the fourth power cabinet, the fifth power cabinet, and the sixth power cabinet, the first power cabinet, the second power cabinet, and the third power cabinet forming one set of three-phase output, and the fourth power cabinet, the fifth power cabinet, and the sixth power cabinet forming another set of three-phase output.
[0007] Preferably, the first, second, third, fourth, fifth, and sixth power cabinets are each provided with six power units arranged in a stacked manner. Each transformer cabinet has a three-phase output terminal, and each power unit has a three-phase input terminal. Each phase output terminal is provided with 18 extended delta winding output points. The input terminal of each phase of the first, second, and third power cabinets is electrically connected to the corresponding extended delta winding output point in the corresponding phase. The fourth, fifth, and sixth power cabinets... Each phase input terminal of the power cabinet is electrically connected to the corresponding extended delta winding output point in the corresponding phase; the three phase input terminals of the power units on the same layer as the first power cabinet are electrically connected to the same extended delta winding output point; the three phase input terminals of the power units on the same layer as the second power cabinet are electrically connected to the same extended delta winding output point; the three phase input terminals of the power units on the same layer as the third power cabinet are electrically connected to the same extended delta winding output point.
[0008] Preferably, a pre-charging cabinet is provided on the left side of the frequency converter unit, and the output end of the pre-charging cabinet is electrically connected to the input end of the transformer cabinet.
[0009] Preferably, a grid-side switch cabinet is provided on the left side of the pre-charge cabinet, and the output end of the grid-side switch cabinet is electrically connected to the input end of the pre-charge cabinet.
[0010] Preferably, there are two frequency conversion units, which are arranged sequentially on the right side of the pre-charge cabinet, and the output end of the pre-charge cabinet is electrically connected to the input end of the two transformer cabinets respectively.
[0011] Preferably, a phase-shifting transformer is installed inside the transformer cabinet.
[0012] Preferably, the power unit includes a fuse, a rectifier bridge, an IGBT module, a heat sink, a first bus capacitor module, and a second bus capacitor module. The rectifier bridge and the IGBT module are fixed to the heat sink from front to back. The first bus capacitor module and the second bus capacitor module are respectively disposed on both sides of the heat sink. The fuse is disposed at the input terminal of the rectifier bridge, and the output terminal of the rectifier bridge is electrically connected to the input terminal of the IGBT module.
[0013] Preferably, the six power units of the first power cabinet, second power cabinet, third power cabinet, fourth power cabinet, fifth power cabinet and sixth power cabinet are cascaded from top to bottom with their neutral terminals left floating. The three-phase output circuit composed of the first power cabinet, second power cabinet and third power cabinet is connected in a star configuration, and the three-phase output circuit composed of the fourth power cabinet, fifth power cabinet and sixth power cabinet is also connected in a star configuration.
[0014] Preferably, the input end of the rectifier bridge is provided with a busbar extending to the side of the transformer cabinet, and the frequency converter is also provided with a cable to connect the busbar to the output point of the extended delta winding corresponding to the phase-shifting transformer.
[0015] Preferably, the first output switch cabinet is provided with a first voltage detection circuit, a first current detection circuit, and a first circuit breaker for controlling the switching on and off of the first power cabinet, the second power cabinet, and the third power cabinet; the second output switch cabinet is provided with a second voltage detection circuit, a second current detection circuit, and a second circuit breaker for controlling the switching on and off of the fourth power cabinet, the fifth power cabinet, and the sixth power cabinet.
[0016] This utility model discloses a frequency converter. The first output switchgear controls the on / off switching, power switching and protection, start / stop control, and status monitoring of the first, second, and third power cabinets. The second output switchgear controls the on / off switching, power switching and protection, start / stop control, and status monitoring of the fourth, fifth, and sixth power cabinets. The first control cabinet is mainly used to adjust the operating frequencies of the first, second, and third power cabinets to reduce energy loss, smoothly start the equipment, and improve the reliability and efficiency of the system. The second control cabinet is mainly used to adjust the operating frequencies of the fourth, fifth, and sixth power cabinets to reduce energy loss, smoothly start the equipment, and improve the reliability and efficiency of the system.
[0017] This utility model's frequency converter has three power cabinets on each of the left and right sides of the transformer cabinet, resulting in a compact structure and symmetrical arrangement of the cabinets on both sides, making it neat and aesthetically pleasing. One transformer cabinet drives the two power cabinets to work alternately. The first, second, and third power cabinets on the left side of the transformer cabinet form one set of three-phase outputs, while the fourth, fifth, and sixth power cabinets on the right side form another set of three-phase outputs. These two sets of three-phase outputs can be configured to work alternately in a time-sharing manner as needed. The two sets of three-phase outputs of this utility model's frequency converter can be connected to the two stator sections of a linear motor, and the two sets of three-phase outputs can be controlled by the first and second output switch cabinets to provide time-sharing power to the two stator sections. Power is supplied to the stator section that the motor is currently in, thus significantly saving energy. This utility model's frequency converter, with its transformer cabinet driving the power cabinets on both sides to work alternately and having two sets of three-phase outputs, eliminates the need for two separate frequency converters to provide time-sharing power to the two stator sections, as required by existing technologies. This reduces the number of transformer cabinets required, resulting in a compact structure, high power density, and low cost. Attached Figure Description
[0018] The present invention will be further described with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the present invention.
[0019] Figure 1 This is a schematic diagram of the structure of a frequency converter according to this utility model;
[0020] Figure 2 This is a schematic diagram of the structure of a frequency converter with conductive busbars according to the present invention;
[0021] Figure 3 This is a schematic diagram of the power unit cascade structure of a frequency converter according to this utility model;
[0022] Figure 4 This is a schematic diagram of the structure of a frequency converter with two frequency conversion units according to the present invention;
[0023] Figure 5 This is a schematic diagram of the power unit of a frequency converter according to this utility model. Detailed Implementation
[0024] The present invention will be further described in conjunction with the following embodiments and accompanying drawings:
[0025] A type of frequency converter, such as Figures 1 to 4As shown, the system includes: a frequency converter unit 10, which includes a transformer cabinet 11, a first power cabinet 12, a second power cabinet 13, a third power cabinet 14, a first output switch cabinet 15, and a first control cabinet 16 arranged sequentially on the left side of the transformer cabinet 11; the frequency converter unit 10 also includes a fourth power cabinet 17, a fifth power cabinet 18, a sixth power cabinet 19, a second output switch cabinet 20, and a second control cabinet 21 arranged sequentially on the right side of the transformer cabinet 11. The output terminals of the transformer cabinet 11 are electrically connected to the input terminals of the first power cabinet 12, the second power cabinet 13, the third power cabinet 14, the fourth power cabinet 17, the fifth power cabinet 18, and the sixth power cabinet 19, respectively. The first power cabinet 12, the second power cabinet 13, and the third power cabinet 14 form a set of three-phase outputs, and the fourth power cabinet 17, the fifth power cabinet 18, and the sixth power cabinet 19 form another set of three-phase outputs.
[0026] The frequency converter of this utility model has a first output switch cabinet 15 that controls the on / off switching, power switching and protection, start / stop control, and status monitoring of the first power cabinet 12, the second power cabinet 13, and the third power cabinet 14. A second output switch cabinet 20 controls the on / off switching, power switching and protection, start / stop control, and status monitoring of the fourth power cabinet 17, the fifth power cabinet 18, and the sixth power cabinet 19. The first control cabinet 16 is mainly used to adjust the operating frequencies of the first power cabinet 12, the second power cabinet 13, and the third power cabinet 14 to reduce energy loss, smoothly start the equipment, and improve the reliability and efficiency of the system. The second control cabinet 21 is mainly used to adjust the operating frequencies of the fourth power cabinet 17, the fifth power cabinet 18, and the sixth power cabinet 19 to reduce energy loss, smoothly start the equipment, and improve the reliability and efficiency of the system.
[0027] The frequency converter of this invention has three power cabinets on the left and right sides of the transformer cabinet 11, respectively. The structure is compact, and the cabinets on both sides are symmetrically arranged, resulting in a neat and aesthetically pleasing appearance. One transformer cabinet 11 drives the two power cabinets to work alternately. The first power cabinet 12, the second power cabinet 13, and the third power cabinet 14 on the left side of the transformer cabinet 11 form one set of three-phase outputs, while the fourth power cabinet 17, the fifth power cabinet 18, and the sixth power cabinet 19 on the right side of the transformer cabinet 11 form another set of three-phase outputs. The two sets of three-phase outputs can be configured to work alternately in a time-sharing manner as needed. The two sets of three-phase outputs of this invention can be connected to the two stator sections of a linear motor, respectively. The first output switch cabinet 15 and the second output switch cabinet 20 control the two sets of three-phase outputs to provide time-sharing power to the two stator sections. Power is supplied to the stator section that the motor is moving to, thus significantly saving energy. The transformer cabinet 11 of this utility model drives the power cabinets on the left and right sides of the frequency converter to work alternately. The frequency converter has two sets of three-phase outputs, which eliminates the need to set up two frequency converters to supply power to the two stator sections separately in the existing technology. This saves the number of transformer cabinets 11, and the structure is compact, with high power density and low cost.
[0028] Better, such as Figures 1 to 4 As shown, the first power cabinet 12, the second power cabinet 13, the third power cabinet 14, the fourth power cabinet 17, the fifth power cabinet 18, and the sixth power cabinet 19 are each equipped with six power units 22 arranged in a stacked manner. The transformer cabinet 11 has three-phase output terminals, and each power unit 22 has three-phase input terminals. Each phase output terminal is equipped with 18 extended delta winding output points. The input terminals of each phase of the first power cabinet 12, the second power cabinet 13, and the third power cabinet 14 are electrically connected to the corresponding extended delta winding output points in the corresponding phase. The fourth power cabinet 17, the fifth power cabinet 18, and the sixth power cabinet 19 are all equipped with six power units 22 arranged in a stacked manner. Each phase input terminal of power cabinet 8 and the sixth power cabinet 19 is electrically connected to the corresponding extended delta winding output point in the corresponding phase; the three-phase input terminals of the power unit 22 on the same layer as the first power cabinet 12 are electrically connected to the same extended delta winding output point; the three-phase input terminals of the power unit 22 on the same layer as the fifth power cabinet 18 and the second power cabinet 13 are electrically connected to the same extended delta winding output point; the three-phase input terminals of the power unit 22 on the same layer as the third power cabinet 14 are electrically connected to the same extended delta winding output point.
[0029] Each phase output terminal is equipped with 18 extended delta winding output points, totaling 18 power units 22 in the first power cabinet 12, second power cabinet 13, and third power cabinet 14. The three-phase input terminals of the power units 22 on the same layer as those in the fourth power cabinet 17 and the first power cabinet 12 are electrically connected to the same extended delta winding output points. Similarly, the three-phase input terminals of the power units 22 on the same layer as those in the fifth power cabinet 18 and the second power cabinet 13 are electrically connected to the same extended delta winding output points. The three-phase input terminals of the power units 22 on the same layer as those in the sixth power cabinet 19 and the third power cabinet 14 are electrically connected to the same extended delta winding output points, thus enabling the transformer cabinet 11 to drive the power cabinets on both sides to work alternately. The six power units 22 within each power cabinet are arranged in a stacked configuration, resulting in a compact structure and facilitating wiring between the power units 22.
[0030] Better, such as Figure 4 As shown, a pre-charging cabinet 23 is provided on the left side of the frequency converter unit 10. The output terminal of the pre-charging cabinet 23 is electrically connected to the input terminal of the transformer cabinet 11. The pre-charging cabinet 23 ensures that the frequency converter can be properly magnetized before startup, reducing the current surge during startup and reducing transformer failures and damage caused by magnetic field problems, thereby ensuring the normal operation of the frequency converter and extending the service life of the equipment.
[0031] Better, such as Figure 4As shown, a grid-side switchgear 24 is located on the left side of the pre-charging cabinet 23. The output terminal of the grid-side switchgear 24 is electrically connected to the input terminal of the pre-charging cabinet 23. The grid-side switchgear 24 is typically equipped with a circuit breaker, connected to an external power supply, to control the switching on and off of the pre-charging cabinet 23 and the transformer cabinet 11. The grid-side switchgear 24 is located on the left side of the pre-charging cabinet 23, which is close to it, facilitates wiring, and saves on the length of connecting wires, thus saving costs.
[0032] Better, such as Figure 4 As shown, there are two frequency converter units 10, which are arranged sequentially on the right side of the pre-charging cabinet 23. The output terminals of the pre-charging cabinet 23 are electrically connected to the input terminals of the two transformer cabinets 11. The frequency converter of this utility model has two frequency converter units 10, which are shared by the pre-charging cabinet 23 and the grid-side switch cabinet 24. It can control the two transformer cabinets 11 simultaneously and has a total of four sets of three-phase power outputs. It can supply power to the four stators in sections simultaneously or on demand, eliminating the need for four frequency converters as required by existing technologies. This greatly reduces the number of devices, makes the structure compact, further improves the power density, and further reduces the cost.
[0033] Preferably, a phase-shifting transformer 25 is installed inside the transformer cabinet 11. The phase-shifting transformer 25 is a prior art phase-shifting transformer 25, whose core function is to form a multi-phase rectifier system by adjusting the phase of the secondary winding, which can reduce the harmonic current on the grid side.
[0034] Better, such as Figure 5 As shown, the power unit 22 includes a fuse 26, a rectifier bridge 27, an IGBT module 28, a heat sink 29, a first bus capacitor module 30, and a second bus capacitor module 31. The rectifier bridge 27 and the IGBT module 28 are fixed to the heat sink 29. The first bus capacitor module 30 and the second bus capacitor module 31 are respectively disposed on both sides of the heat sink 29. The fuse 26 is disposed at the input end of the rectifier bridge 27, and the output end of the rectifier bridge 27 is electrically connected to the input end of the IGBT module 28.
[0035] A fuse 26 is installed at the input terminal of the rectifier bridge 27 to provide short-circuit protection. The rectifier bridge 27, IGBTs, and bus capacitors in the power unit 22 are relatively large and numerous; a conventional flat-lay installation structure would be loose, not compact, and bulky. By dividing the bus capacitors into a first bus capacitor module 30 and a second bus capacitor module 31, and fixing the rectifier bridge 27 and IGBT module 28 to the heat sink 29, the first bus capacitor module 30 and the second bus capacitor module 31 are respectively positioned on both sides of the heat sink 29. The symmetrical arrangement of the first bus capacitor module 30 and the second bus capacitor module 31 on both sides of the rectifier bridge 27, IGBT module 28, and heat sink 29 fully utilizes space, resulting in a very compact structure, small size, and increased power density.
[0036] Better, such as Figure 2 and Figure 3 As shown, the six power units 22 of the first power cabinet 12, the second power cabinet 13, the third power cabinet 14, the fourth power cabinet 17, the fifth power cabinet 18 and the sixth power cabinet 19 are cascaded from top to bottom to output 39, and the neutral terminal 40 is left floating. The three-phase output circuit composed of the first power cabinet 12, the second power cabinet 13 and the third power cabinet 14 is connected in a star configuration, and the three-phase output circuit composed of the fourth power cabinet 17, the fifth power cabinet 18 and the sixth power cabinet 19 is also connected in a star configuration.
[0037] The six power units 22 in each power cabinet are cascaded from top to bottom to output 39, with the neutral terminal 40 left floating. This means that the cascaded six power units 22 in each power cabinet output one phase of power. The three-phase output circuit composed of the first power cabinet 12, the second power cabinet 13, and the third power cabinet 14 is connected in a star configuration. This star configuration is a common connection method in existing technology. The power supply consists of three sine waves with a 120-degree phase difference. The load of each phase is connected to the same neutral terminal 40, achieving balanced load distribution and preventing system failures caused by overload of any single load. The cascaded output 39 of the six power units 22 in each power cabinet is simple to connect, provides high output power, and has high power density.
[0038] Better, such as Figure 2 As shown, the input end of the rectifier bridge 27 is provided with a conductor bus 38 extending to the side of the transformer cabinet 11. The frequency converter is also provided with a cable to connect the conductor bus 38 to the output point of the extended delta winding of the phase-shifting transformer 25.
[0039] The input end of the rectifier bridge 27 is provided with a conductive bus 38 extending to the side of the transformer cabinet 11. The conductive bus 38 is then connected to the output point of the extended delta winding of the phase-shifting transformer 25 using a shorter cable. This reduces the use of cables, facilitates parallel cabinet wiring, and saves costs.
[0040] Better, such as Figure 2 and Figure 3 As shown, the first output switch cabinet 15 is equipped with a first voltage detection circuit 32, a first current detection circuit 33, and a first circuit breaker 34 that controls the switching on and off of the first power cabinet 12, the second power cabinet 13, and the third power cabinet 14; the second output switch cabinet 20 is equipped with a second voltage detection circuit 35, a second current detection circuit 36, and a second circuit breaker 37 that controls the switching on and off of the fourth power cabinet 17, the fifth power cabinet 18, and the sixth power cabinet 19.
[0041] The first voltage detection circuit 32 and the first current detection circuit 33 can detect the voltage and current of the transformer cabinet 11 and the three power cabinets on the left, respectively; the second voltage detection circuit 35 and the second current detection circuit 36 can detect the voltage and current of the three power cabinets on the right, respectively. The first control cabinet 16 controls the first circuit breaker 34 to control the on / off state of the first power cabinet 12, the second power cabinet 13, and the third power cabinet 14 based on the voltage and current signals detected by the first voltage detection circuit 32 and the first current detection circuit 33, thereby achieving overvoltage and overcurrent protection. The second control cabinet 21 controls the second circuit breaker 37 to control the on / off state of the fourth power cabinet 17, the fifth power cabinet 18, and the sixth power cabinet 19 based on the voltage and current signals detected by the second voltage detection circuit 35 and the second current detection circuit 36, thereby achieving overvoltage and overcurrent protection.
[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit the scope of protection of this utility model. Although this utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this utility model without departing from the essence and scope of the technical solutions of this utility model.
Claims
1. A frequency converter, characterized in that, include: The frequency converter unit includes a transformer cabinet, and a first power cabinet, a second power cabinet, a third power cabinet, a first output switch cabinet, and a first control cabinet arranged sequentially on the left side of the transformer cabinet. The frequency converter unit also includes a fourth power cabinet, a fifth power cabinet, a sixth power cabinet, a second output switch cabinet, and a second control cabinet arranged sequentially on the right side of the transformer cabinet. The output terminals of the transformer cabinet are electrically connected to the input terminals of the first power cabinet, the second power cabinet, the third power cabinet, the fourth power cabinet, the fifth power cabinet, and the sixth power cabinet, respectively. The first power cabinet, the second power cabinet, and the third power cabinet form one set of three-phase output, and the fourth power cabinet, the fifth power cabinet, and the sixth power cabinet form another set of three-phase output.
2. The frequency converter according to claim 1, characterized in that: The first, second, third, fourth, fifth, and sixth power cabinets each have six power units arranged in a stacked configuration. Each transformer cabinet has a three-phase output terminal, and each power unit has a three-phase input terminal. Each phase output terminal has 18 extended delta winding output points. The input terminal of each phase in the first, second, and third power cabinets is electrically connected to the corresponding extended delta winding output point in that phase. The fourth, fifth, and sixth power cabinets... Each phase input terminal of the cabinet is electrically connected to the corresponding extended delta winding output point in the corresponding phase; the three phase input terminals of the power units on the same layer as the first power cabinet are electrically connected to the same extended delta winding output point; the three phase input terminals of the power units on the same layer as the second power cabinet are electrically connected to the same extended delta winding output point; the three phase input terminals of the power units on the same layer as the third power cabinet are electrically connected to the same extended delta winding output point.
3. A frequency converter according to claim 2, characterized in that: A pre-charging cabinet is provided on the left side of the frequency converter unit, and the output end of the pre-charging cabinet is electrically connected to the input end of the transformer cabinet.
4. A frequency converter according to claim 3, characterized in that: A grid-side switch cabinet is installed on the left side of the pre-charge cabinet, and the output terminal of the grid-side switch cabinet is electrically connected to the input terminal of the pre-charge cabinet.
5. A frequency converter according to claim 4, characterized in that: The number of frequency conversion units is two, and the two frequency conversion units are arranged sequentially on the right side of the pre-charge cabinet. The output terminal of the pre-charge cabinet is electrically connected to the input terminal of the two transformer cabinets respectively.
6. A frequency converter according to claim 5, characterized in that: The transformer cabinet is equipped with a phase-shifting transformer.
7. A frequency converter according to claim 6, characterized in that: The power unit includes a fuse, a rectifier bridge, an IGBT module, a heat sink, a first bus capacitor module, and a second bus capacitor module. The rectifier bridge and the IGBT module are fixed to the heat sink from the front and back. The first bus capacitor module and the second bus capacitor module are respectively disposed on both sides of the heat sink. The fuse is disposed at the input terminal of the rectifier bridge, and the output terminal of the rectifier bridge is electrically connected to the input terminal of the IGBT module.
8. A frequency converter according to claim 7, characterized in that: The six power units of the first power cabinet, the second power cabinet, the third power cabinet, the fourth power cabinet, the fifth power cabinet, and the sixth power cabinet are cascaded from top to bottom with their neutral terminals floating. The three-phase output circuit composed of the first power cabinet, the second power cabinet, and the third power cabinet is connected in a star configuration. The three-phase output circuit composed of the fourth power cabinet, the fifth power cabinet, and the sixth power cabinet is also connected in a star configuration.
9. A frequency converter according to claim 8, characterized in that: The input end of the rectifier bridge is provided with a conductive bus extending to the side of the transformer cabinet, and the frequency converter is also provided with a cable to connect the conductive bus to the output point of the extended delta winding corresponding to the phase-shifting transformer.
10. A frequency converter according to claim 9, characterized in that: The first output switch cabinet is equipped with a first voltage detection circuit, a first current detection circuit, and a first circuit breaker that controls the switching on and off of the first power cabinet, the second power cabinet, and the third power cabinet; the second output switch cabinet is equipped with a second voltage detection circuit, a second current detection circuit, and a second circuit breaker that controls the switching on and off of the fourth power cabinet, the fifth power cabinet, and the sixth power cabinet.