Single-column operation variable frequency induced draft fan dual power supply terminal switching power supply system

Abstract

Embodiments of the present disclosure provide a single-column operation variable frequency induced draft fan dual power supply terminal switching power supply system, comprising a first power supply main circuit connected with a first high-voltage power supply and a second power supply main circuit connected with a second high-voltage power supply, a high-voltage motor, a high-voltage frequency converter, and a first local high-voltage bypass cabinet and a second local high-voltage bypass cabinet respectively arranged at the terminals of the two power supply main circuits; wherein each bypass cabinet is provided with a variable frequency branch switch and a power frequency bypass branch switch, so that each power supply main circuit can be connected with the high-voltage frequency converter through the variable frequency branch or directly connected with the high-voltage motor through the power frequency bypass branch. Embodiments of the present disclosure eliminate single-point failure from the source through dual power supply redundancy and terminal switching design, realize second-level rapid switching, greatly improve the reliability of single variable frequency induced draft fan power supply, effectively avoid unit unscheduled shutdown, and at the same time control the investment cost.

Description

Technical Field

[0001] The embodiments disclosed herein belong to the field of induced draft fan power supply technology, specifically relating to a power supply system for a single-row operating variable frequency induced draft fan with dual power supply terminal switching. Background Technology

[0002] In existing thermal power plants and steel mills, under the condition of a single generating unit equipped with a single variable frequency induced draft fan, the power supply system generally adopts a "single power source + single circuit" architecture: power is supplied solely by the upstream plant high-voltage switchgear, relying on the interconnection function of the two sections of the plant high-voltage busbar to ensure power continuity. The specific power supply path is: plant high-voltage busbar, high-voltage switchgear, high-voltage cable, local high-voltage inverter room, high-voltage inverter, high-voltage motor (induced draft fan drive end). Some systems may be equipped with simple bypass cabinets, but this does not form dual power source redundancy or end-point switching capability. The cable laying distance is usually in the range of 350 to 450 meters, depending on the unit size and plant layout, and can reach more than 500 meters in some complex plant areas.

[0003] Although the existing power supply method complies with basic regulations and standards, it has the following core defects that directly threaten the safe operation of the generating unit: (1) High risk of single-point failure in power supply link: failure of any link such as high voltage switch cabinet failure, high voltage cable insulation damage / phase loss / short circuit, bypass cabinet failure, high voltage motor failure, etc. will lead to the shutdown of induced draft fan (because a single unit is only equipped with one induced draft fan). The shutdown of induced draft fan directly causes unplanned shutdown of the unit, resulting in significant economic losses. (2) Weak fault response capability: The power supply redundancy method that relies on bus interconnection has a long switching path and slow response time. It usually requires manual intervention or linkage at the upper bus level, and cannot quickly isolate fault links and restore power supply. (3) Imperfect interlocking mechanism: Existing systems mostly rely on a single mechanical interlocking or program interlocking, lacking redundant protection. They are prone to accidental closing due to interlocking failure, which can lead to secondary accidents such as short circuits in the power supply system. (4) Insufficient adaptability: For situations where the high investment required for parallel operation of two induced draft fans cannot be afforded, there is no effective alternative to the existing single power supply system, making it difficult to balance investment costs and operational reliability. Summary of the Invention

[0004] The embodiments disclosed herein aim to at least solve one of the technical problems existing in the prior art, and provide a power supply system for a single-row operating variable frequency induced draft fan with dual power supply terminal switching, including: A first power supply main circuit and a second power supply main circuit, wherein the first power supply main circuit is connected to a first high-voltage power supply and the second power supply main circuit is connected to a second high-voltage power supply; High-voltage motors are used to drive induced draft fans that operate in a single row. A high-voltage frequency converter, the output of which is connected to the high-voltage motor; The first local high-voltage bypass cabinet and the second local high-voltage bypass cabinet are respectively located at the ends of the first power supply main circuit and the second power supply main circuit; wherein, The first local high-voltage bypass cabinet is equipped with a first frequency converter branch switch and a first power frequency bypass branch switch, and the second local high-voltage bypass cabinet is equipped with a second frequency converter branch switch and a second power frequency bypass branch switch. The first main power supply circuit can be selectively connected to the input terminal of the high-voltage frequency converter through the first frequency conversion branch switch, or connected to the high-voltage motor through the first power frequency bypass branch switch; The second main power supply circuit can be selectively connected to the input terminal of the high-voltage frequency converter via the second frequency conversion branch switch, or connected to the high-voltage motor via the second power frequency bypass branch switch.

[0005] Furthermore, the first power supply main circuit includes a first high-voltage switchgear, a first vacuum circuit breaker, and a first high-voltage cable connected in sequence; the second power supply main circuit includes a second high-voltage switchgear, a second vacuum circuit breaker, and a second high-voltage cable connected in sequence.

[0006] Furthermore, the power supply system also includes a control module and a fault detection module; The control module is communicatively connected to the first vacuum circuit breaker, the second vacuum circuit breaker, the first variable frequency branch switch, the first power frequency bypass branch switch, the second variable frequency branch switch, the second power frequency bypass branch switch, and the high-voltage frequency converter, respectively. The fault detection module is used to monitor the operating status of the first power supply main circuit, the second power supply main circuit, and the high-voltage frequency converter, and sends the monitoring signals to the control module.

[0007] Furthermore, the control module has a preset program interlocking logic to prevent the first vacuum circuit breaker and the second vacuum circuit breaker from closing simultaneously.

[0008] Furthermore, the control module is configured as follows: When the fault detection module detects a fault in the first power supply main circuit, it controls the first vacuum circuit breaker and the first frequency converter branch switch to open, and controls the second vacuum circuit breaker and the second frequency converter branch switch to close.

[0009] Furthermore, the control module is configured as follows: When the fault detection module detects a fault in the high-voltage frequency converter and the first power supply main circuit is normal, it controls the first frequency converter branch switch to open and the high-voltage frequency converter to stop, while simultaneously controlling the first power frequency bypass branch switch to close.

[0010] Furthermore, a first physical interlocking mechanism is provided between the first frequency conversion branch switch and the second frequency conversion branch switch to prevent the first frequency conversion branch switch and the second frequency conversion branch switch from closing simultaneously.

[0011] Furthermore, a second physical interlocking mechanism is provided between the first power frequency bypass branch switch and the second power frequency bypass branch switch to prevent the first power frequency bypass branch switch and the second power frequency bypass branch switch from closing simultaneously.

[0012] Furthermore, a third physical interlocking mechanism is provided between the first frequency conversion branch switch and the first power frequency bypass branch switch, and a fourth physical interlocking mechanism is provided between the second frequency conversion branch switch and the second power frequency bypass branch switch, to prevent the frequency conversion branch switch and the power frequency bypass branch switch in the same local high voltage bypass cabinet from closing at the same time.

[0013] Furthermore, the power supply system also includes a common connection switch, the first end of which is connected to the high-voltage motor, and the second end of which is connected to the output terminal of the high-voltage frequency converter, the output terminal of the first power frequency bypass branch switch, and the output terminal of the second power frequency bypass branch switch, respectively.

[0014] This disclosure discloses a power supply system for a single-row variable frequency induced draft fan with dual power supply and end-of-line switching. By constructing a dual independent power supply architecture consisting of a first main power supply circuit and a second main power supply circuit, and installing a local high-voltage bypass cabinet at the end of each main power supply circuit, it achieves power supply redundancy and end-of-line switching functionality. This eliminates the risk of single-point failure from the power source, significantly shortens the switching path, and significantly improves the reliability and fault recovery capability of the power supply system for a single variable frequency induced draft fan, effectively avoiding unplanned unit shutdowns due to power supply link failures. Simultaneously, this architecture eliminates the need for additional spare induced draft fans, significantly improving operational reliability while keeping the total investment cost at a low level, thus effectively balancing the requirements of investment cost and operational reliability. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the power supply system for a single-row operating variable frequency induced draft fan with dual power supply terminal switching, according to an embodiment of the present disclosure. Detailed Implementation

[0016] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. Based on the embodiments of this disclosure, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this disclosure.

[0017] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this disclosure.

[0018] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0019] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various components, these components should not be limited by these terms. These terms are used to distinguish one component from another. Therefore, the first component discussed below may be referred to as the second component without departing from the teachings of this disclosure. As used in this disclosure, the term "and / or" includes all combinations of any and more of the associated listed items.

[0020] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of exemplary embodiments, and the modules or processes in the drawings are not necessarily necessary for implementing this disclosure, and therefore cannot be used to limit the scope of protection of this disclosure.

[0021] like Figure 1 As shown, embodiments of this disclosure provide a power supply system for a single-row variable frequency induced draft fan with dual power supply terminal switching, comprising: A first power supply main circuit 100 and a second power supply main circuit 200 are connected, wherein the first power supply main circuit 100 is connected to a first high-voltage power supply 110 and the second power supply main circuit 200 is connected to a second high-voltage power supply 210. High-voltage motor 300 is used to drive induced draft fan 400 for single-row operation; A high-voltage frequency converter 500, the output of which is connected to the high-voltage motor 300; The first local high-voltage bypass cabinet 120 and the second local high-voltage bypass cabinet 220 are respectively located at the ends of the first power supply main circuit 100 and the second power supply main circuit 200; wherein, the first local high-voltage bypass cabinet 120 is provided with a first frequency converter branch switch QS1 and a first power frequency bypass branch switch QS3, and the second local high-voltage bypass cabinet 220 is provided with a second frequency converter branch switch QS2 and a second power frequency bypass branch switch QS4; The first main power supply circuit 100 can be selectively connected to the input terminal of the high-voltage frequency converter 500 via the first frequency conversion branch switch QS1, or connected to the high-voltage motor 300 via the first power frequency bypass branch switch QS3; the second main power supply circuit 200 can be selectively connected to the input terminal of the high-voltage frequency converter 500 via the second frequency conversion branch switch QS2, or connected to the high-voltage motor 300 via the second power frequency bypass branch switch QS4.

[0022] Specifically, the power supply system in this embodiment adopts dual independent power sources: the first high-voltage power source 110 is the plant high-voltage section I bus, and the second high-voltage power source 210 is the plant high-voltage section II bus. One of the plant bus can be replaced with an independent standby generator (such as a diesel generator) to form a dual power source architecture of plant bus and standby generator, thereby further improving power supply redundancy to cope with the extreme scenario of all buses losing power at the same time.

[0023] The first main power supply circuit 100 includes a first high-voltage switchgear 130, a first vacuum circuit breaker QF1, and a first high-voltage cable 140 connected in sequence; the second main power supply circuit 200 includes a second high-voltage switchgear 230, a second vacuum circuit breaker QF2, and a second high-voltage cable 240 connected in sequence. The aforementioned high-voltage switchgear and vacuum circuit breaker are power supply switching devices of this power supply system. The first high-voltage switchgear 130 corresponds to the first high-voltage power supply 110, and the second high-voltage switchgear 230 corresponds to the second high-voltage power supply 210. The first vacuum circuit breaker QF1 is installed at the output terminal of the first high-voltage switchgear 130, and the second vacuum circuit breaker QF2 is installed at the output terminal of the second high-voltage switchgear 230.

[0024] The local switching equipment includes a first local high-voltage bypass cabinet 120 and a second local high-voltage bypass cabinet 220. The first frequency converter branch switch QS1, the second frequency converter branch switch QS2, the first power frequency bypass branch switch QS3, and the second power frequency bypass branch switch QS4 all employ high-voltage isolating switches. The two independent high-voltage bypass cabinets are integrated near the high-voltage frequency converter room of the induced draft fan, forming a local end-to-end switching design. This enables the localized deployment of power supply switching functions at the load end (near the induced draft fan), shortening the switching path from "bus-switch cabinet-cable-end" to "internal switching within the end-to-end bypass cabinet." Compared to traditional bus-level switching, this reduces the switching path by more than 80%, and the fault response time is reduced from minutes (3-5 minutes) to seconds (≤1 second), significantly reducing production capacity losses caused by faults.

[0025] The core equipment of the power supply system includes a high-voltage motor 300, which serves as the drive motor for the induced draft fan 400, and a high-voltage frequency converter 500 (such as the ABB ACS800-17 series) adapted to the power level of the high-voltage motor 300.

[0026] This embodiment uses two completely physically isolated power supplies, each forming two parallel main power supply circuits through independent high-voltage switch cabinets and high-voltage cables. This eliminates the risk of single-point failure of a single power supply from the source, and there is no need to add induced draft fan equipment. Redundant power supply is achieved only through the architecture of the power supply system. While meeting the high reliability requirements, the total investment cost is controlled to only 30% to 40% of the dual induced draft fan parallel operation scheme, which well balances the requirements of investment cost and reliability.

[0027] Exemplarily, the power supply system of this embodiment further includes a control module and a fault detection module. The control module is a DCS / PLC host (such as a Siemens S7-400 series), which is communicatively connected to the first vacuum circuit breaker QF1, the second vacuum circuit breaker QF2, the first frequency converter branch switch QS1, the first power frequency bypass branch switch QS2, the second frequency converter branch switch QS3, the second power frequency bypass branch switch QS4, and the high-voltage frequency converter 500. The fault detection module includes current transformers, voltage transformers, cable insulation monitoring sensors, etc., and is hardwired to the DCS / PLC host. It is used to monitor the operating status of the first main power supply circuit 100, the second main power supply circuit 200, and the high-voltage frequency converter 500, and sends monitoring signals (current, voltage, insulation status, etc.) to the control module. By monitoring the cable insulation status, switchgear status, and inverter operation status of the two main circuits in real time, when a fault occurs in any main circuit or the high-voltage inverter 500, the other main circuit is automatically triggered to start and the corresponding disconnector / circuit breaker is opened or closed, without the need for manual intervention, thus achieving self-recovery from the fault.

[0028] The control module has a pre-set program interlocking logic to prevent the first vacuum circuit breaker QF1 and the second vacuum circuit breaker QF2 from closing simultaneously. For example, when QF1 is closed, the closing command for QF2 is prohibited, and a "closing prohibited" signal is sent back to the operation panel of the second high-voltage switchgear 230; conversely, when QF2 is closed, the closing command for QF1 is prohibited. Fast signal transmission (response time ≤ 100ms) can be achieved through hardwiring, avoiding malfunctions caused by logic delays.

[0029] For example, gear meshing mechanisms are used between the first frequency conversion branch switch QS1 and the second frequency conversion branch switch QS3, and between the first power frequency bypass branch switch QS2 and the second power frequency bypass branch switch QS4. When one of the switches is closed, the gear meshes and locks the operating shaft of the other switch, preventing it from rotating, thus forming a physical lock-in and preventing QS1 and QS3, and QS2 and QS4 from closing at the same time.

[0030] For example, the power supply system of this disclosure embodiment also employs a physical interlocking mechanism to prevent the frequency converter branch switch and the power frequency bypass branch switch in the same local high-voltage bypass cabinet from closing simultaneously. The first frequency converter branch switch QS1 and the first power frequency bypass branch switch QS2 are connected by a linkage pin structure. When QS1 closes, the linkage pin inserts into the operating mechanism slot of QS2, restricting QS2 from closing. The second frequency converter branch switch QS3 and the second power frequency bypass branch switch QS4 are connected by a bidirectional interlocking plate structure. When either disconnector closes, the interlocking plate blocks the closing path of the other disconnector, ensuring that they cannot be physically closed simultaneously.

[0031] In some embodiments, the aforementioned mechanical interlocks (gear engagement, linkage pins, bidirectional interlocking plates) can be entirely or partially replaced with electromagnetic interlocks (such as electromagnetic interlocking switches). Electromagnetic signals control the closing authority of the disconnect switch, preventing malfunctions caused by mechanical wear and improving the convenience of remote control. The complementary interlocking system, combining programmatic and physical mechanisms, achieves rapid logical interlocking, while physical interlocking provides redundant protection, completely eliminating secondary accidents such as simultaneous closing of two power supplies or incorrect switching between frequency converter and power frequency branches, significantly improving the reliability of the power supply system in this embodiment.

[0032] For example, such as Figure 1 As shown, the power supply system of this embodiment further includes a common connection switch QS5 (isolating switch). The first end of the common connection switch QS5 is connected to the high-voltage motor 300, and the second end is connected to the output end of the high-voltage frequency converter 500, the output end of the first power frequency bypass branch switch QS3, and the output end of the second power frequency bypass branch switch QS4, respectively.

[0033] The following describes the workflow of the power supply system in this embodiment through a series of specific operating conditions: Operating Condition 1: Normal frequency converter operation startup (first power supply main circuit 100 prioritized) The control module issues the following commands: ① Close QF1, QS1 and QS5, while simultaneously opening QF2, QS2 and QS4; ② Start the high-voltage frequency converter 500, adjust it to the target frequency, supply power to the high-voltage motor 300 through the frequency conversion branch, and start the induced draft fan 400 to operate at the frequency conversion. The fault detection module monitors the voltage, QF1 status, QS1 status, cable insulation status, and high-voltage frequency converter 500 operating parameters of the first high-voltage power supply 110 in real time, and uploads the data to the control module.

[0034] Operating Condition 2: Fault in the first main power supply circuit 100 MHz switches to the second main power supply circuit 200 MHz inverter operation. When the fault detection module detects a cable short circuit / insulation damage, QF1 fault, QS1 fault, or high-voltage frequency converter 500 operating normally but the first power supply main circuit 100 is unable to supply power: Upon receiving the fault signal, the control module immediately issues the following commands: ① Open QF1 and QS1; ② After a delay of 0.5 to 1 second (ensuring the circuit is completely disconnected), close QF2 and QS2; ③ The high-voltage frequency converter 500 continues to run (or restarts), continuously supplying power to the high-voltage motor 300 through the frequency conversion branch of the second power supply main circuit 200, and the induced draft fan 400 does not stop during the switching process (or the stop time is ≤1 second).

[0035] Operating Condition 3: High-voltage frequency converter 500 fault, switching to power frequency bypass operation. When the fault detection module detects abnormalities such as overcurrent, overvoltage, or IGBT fault in the high-voltage frequency converter: The control module issues the following commands: ① Open QS1 and stop the high-voltage frequency converter 500; ② Close QS3 (power frequency bypass branch); ③ Keep QF1 and QS5 closed, supply power to the high-voltage motor 300 through the power frequency bypass branch of the first power supply main circuit 100, and the induced draft fan 400 runs at power frequency. Backup logic: If the first power supply main circuit 100 is faulty at the same time, it will be switched to the power frequency bypass branch of the second power supply main circuit 200 (QF1, QS1 for opening, QF2, QS4, QS5 for closing).

[0036] Operating Condition 4: Manual Switching Mode (Emergency Operating Condition) When the control module fails, the opening and closing operations of the disconnectors and circuit breakers can be manually completed through the manual operation mechanism of the local high-voltage bypass cabinets 120 and 220, combined with the physical interlocking mechanism, to ensure that the system can still achieve basic power supply switching functions.

[0037] By designing variable frequency operation branches (via high-voltage frequency converter 500) and power frequency bypass branches (via QS3 or QS4) for each main power supply circuit, and combining them with interlocking logic linkage control, seamless switching between two operating modes is achieved: variable frequency operation, which is energy-saving and flexible in speed regulation under normal operating conditions, and power frequency bypass operation, which automatically switches when the frequency converter fails. This ensures that the induced draft fan can work stably and continuously under different equipment conditions, adapt to different fault scenarios, and reduce the rate of unplanned unit shutdowns from over 80% to 0%, significantly improving production continuity.

[0038] Additionally, all isolating switches in the local high-voltage bypass cabinet can be replaced with vacuum circuit breakers, increasing the number of bypass cabinets to four (one per branch). All vacuum circuit breakers are connected to the control module via hardwiring to achieve program interlocking, eliminating physical interlocking, improving the feasibility of remote operation, reducing the intensity of manual operation, and thus being suitable for scenarios with high automation requirements. Furthermore, the aforementioned automatic fault switching logic can be changed from hardwiring control to local PLC control, with an independent PLC controller set up locally to communicate and link with the host control module. This reduces signal attenuation over long distances via hardwiring, improves switching control accuracy, and is therefore suitable for large-span factory environments.

[0039] This disclosure discloses a power supply system for a single-row variable frequency induced draft fan with dual power supply and end-of-line switching. By constructing a dual independent power supply architecture consisting of a first main power supply circuit and a second main power supply circuit, and installing a local high-voltage bypass cabinet at the end of each main power supply circuit, it achieves power supply redundancy and end-of-line switching functionality. This eliminates the risk of single-point failure from the power source, significantly shortens the switching path, and significantly improves the reliability and fault recovery capability of the power supply system for a single variable frequency induced draft fan, effectively avoiding unplanned unit shutdowns due to power supply link failures. Simultaneously, this architecture eliminates the need for additional spare induced draft fans, significantly improving operational reliability while keeping the total investment cost at a low level, thus effectively balancing the requirements of investment cost and operational reliability.

[0040] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A power supply system for a single-row variable frequency induced draft fan with dual power supply and end-point switching, characterized in that, include: A first power supply main circuit and a second power supply main circuit, wherein the first power supply main circuit is connected to a first high-voltage power supply and the second power supply main circuit is connected to a second high-voltage power supply; High-voltage motors are used to drive induced draft fans that operate in a single row. A high-voltage frequency converter, the output of which is connected to the high-voltage motor; The first local high-voltage bypass cabinet and the second local high-voltage bypass cabinet are respectively located at the ends of the first power supply main circuit and the second power supply main circuit; wherein, The first local high-voltage bypass cabinet is equipped with a first frequency converter branch switch and a first power frequency bypass branch switch, and the second local high-voltage bypass cabinet is equipped with a second frequency converter branch switch and a second power frequency bypass branch switch. The first main power supply circuit can be selectively connected to the input terminal of the high-voltage frequency converter through the first frequency conversion branch switch, or connected to the high-voltage motor through the first power frequency bypass branch switch; The second main power supply circuit can be selectively connected to the input terminal of the high-voltage frequency converter via the second frequency conversion branch switch, or connected to the high-voltage motor via the second power frequency bypass branch switch.

2. The power supply system according to claim 1, characterized in that, The first power supply main circuit includes a first high-voltage switchgear, a first vacuum circuit breaker, and a first high-voltage cable connected in sequence; the second power supply main circuit includes a second high-voltage switchgear, a second vacuum circuit breaker, and a second high-voltage cable connected in sequence.

3. The power supply system according to claim 2, characterized in that, It also includes a control module and a fault detection module; The control module is communicatively connected to the first vacuum circuit breaker, the second vacuum circuit breaker, the first variable frequency branch switch, the first power frequency bypass branch switch, the second variable frequency branch switch, the second power frequency bypass branch switch, and the high-voltage frequency converter, respectively. The fault detection module is used to monitor the operating status of the first power supply main circuit, the second power supply main circuit, and the high-voltage frequency converter, and sends the monitoring signals to the control module.

4. The power supply system according to claim 3, characterized in that, The control module has a preset program interlocking logic to prevent the first vacuum circuit breaker and the second vacuum circuit breaker from closing simultaneously.

5. The power supply system according to claim 3, characterized in that, The control module is configured as follows: When the fault detection module detects a fault in the first power supply main circuit, it controls the first vacuum circuit breaker and the first frequency converter branch switch to open, and controls the second vacuum circuit breaker and the second frequency converter branch switch to close.

6. The power supply system according to claim 3, characterized in that, The control module is configured as follows: When the fault detection module detects a fault in the high-voltage frequency converter and the first power supply main circuit is normal, it controls the first frequency converter branch switch to open and the high-voltage frequency converter to stop, while simultaneously controlling the first power frequency bypass branch switch to close.

7. The power supply system according to claim 1, characterized in that, A first physical interlocking mechanism is provided between the first frequency conversion branch switch and the second frequency conversion branch switch to prevent the first frequency conversion branch switch and the second frequency conversion branch switch from closing at the same time.

8. The power supply system according to claim 1, characterized in that, A second physical interlocking mechanism is provided between the first power frequency bypass branch switch and the second power frequency bypass branch switch to prevent the first power frequency bypass branch switch and the second power frequency bypass branch switch from closing at the same time.

9. The power supply system according to claim 1, characterized in that, A third physical interlocking mechanism is provided between the first frequency conversion branch switch and the first power frequency bypass branch switch, and a fourth physical interlocking mechanism is provided between the second frequency conversion branch switch and the second power frequency bypass branch switch, to prevent the frequency conversion branch switch and the power frequency bypass branch switch in the same local high voltage bypass cabinet from closing at the same time.

10. The power supply system according to any one of claims 1 to 9, characterized in that, It also includes a common connection switch, the first end of which is connected to the high-voltage motor, and the second end is connected to the output terminal of the high-voltage frequency converter, the output terminal of the first power frequency bypass branch switch and the output terminal of the second power frequency bypass branch switch, respectively.

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