A variable frequency soft start and drag system for starting bus section connection

Abstract

The utility model discloses a kind of starting bus with subsection liaison's variable frequency soft start drag system, belong to high voltage frequency converter technical field. Including high voltage bus, frequency converter VFD1, frequency converter VFD2, electric reactor L1, electric reactor L2, disconnecting switch QS1, disconnecting switch QS2, disconnecting switch QS3, starting bus I section, starting bus II section, section I motor, section II motor. By using disconnecting switch QS3 as liaison switch, the power distribution of two starting buses is realized, so that the variable frequency soft start control of two frequency converters to multiple motors is realized, and the two frequency converters are standby for each other. Any frequency converter can perform soft start control for any selected motor through corresponding operation. There is no need to configure as many circuit breakers as the total number of motors on the output side of each frequency converter. Compared with the existing scheme, the one-time investment of switchgear equipment can be reduced, the system's space occupation is reduced, and the complexity of the variable frequency soft start drag system control loop is reduced.

Description

Technical Field

[0001] This utility model relates to a variable frequency soft start drive system with segmented interconnection on the starting bus, belonging to the field of high voltage frequency converter technology. Background Technology

[0002] High-voltage, high-power motors employ high-voltage frequency converter soft-start technology, enabling smooth starting, significantly reducing the impact of starting current on the power grid, and reducing starting stress on the motor and mechanical load. At the same time, they can adjust the speed according to the operating conditions to save energy. They are widely used in fields requiring large power equipment, such as power, metallurgy, petrochemical, mining, rail transportation, and shipbuilding, improving the stability and economy of system operation.

[0003] When multiple devices on the same production line are started simultaneously, the voltage on the power bus drops significantly, affecting the normal operation of other devices on the same bus. Therefore, to ensure the safety and reliability of the power grid supply system and the motor control system, a variable frequency soft start scheme with multiple frequency converters as backups is generally required.

[0004] When multiple frequency converters and multiple high-voltage motors are connected to the same power bus, each frequency converter draws its own power supply from its respective bus segment on the input side. On the output side, each frequency converter is equipped with the same number of high-voltage switches as the motors to select which motor to operate on. From a hardware perspective, this results in a large number of high-voltage switchgear cabinets being configured on the output side of the frequency converters. From a control perspective, this increases the complexity of the control loop connections between the frequency converters and the high-voltage switchgear cabinets.

[0005] Therefore, in order to reduce hardware costs and simplify the complexity of the control loop, a variable frequency soft start drive system with segmented connection of the starting bus was designed. The existing wiring of each segment of the starting bus is reused, and multiple segments of the starting bus are connected through disconnecting switches, thus achieving a simpler and more reasonable wiring method. Summary of the Invention

[0006] The technical problem to be solved by this utility model is to provide a variable frequency soft start drive system with segmented interconnection on the starting bus, which solves the problems of high cost and complex wiring in the current method of driving multiple high-voltage high-power motors with multiple frequency converters through a large number of high-voltage switch cabinets.

[0007] The technical problem to be solved by this utility model is achieved by the following technical solution:

[0008] A variable frequency soft start drive system with segmented interconnection on the starting bus includes a high-voltage bus, frequency converter VFD1, frequency converter VFD2, reactor L1, reactor L2, disconnecting switch QS1, disconnecting switch QS2, disconnecting switch QS3, starting bus section I, starting bus section II, section I motor, and section II motor.

[0009] The high-voltage busbar is electrically connected to the motor in section I through the first incoming circuit breaker, and the high-voltage busbar is electrically connected to the motor in section II through the second incoming circuit breaker.

[0010] The high-voltage busbar is sequentially electrically connected to the frequency converter VFD1, reactor L1, disconnector QS1, and starting busbar section I via circuit breaker QF3, and sequentially electrically connected to the frequency converter VFD2, reactor L2, disconnector QS2, and starting busbar section II via circuit breaker QF4.

[0011] The starting bus section I is electrically connected to the motor of section I through the first starting circuit breaker, and the starting bus section II is electrically connected to the motor of section II through the second starting circuit breaker.

[0012] The starting bus section I is electrically connected to the starting bus section II via the disconnecting switch QS3.

[0013] Preferably, the first-stage motor includes motor M1 and motor M2, the corresponding first incoming circuit breaker includes circuit breaker QF1 and circuit breaker QF2, and the corresponding first starting circuit breaker includes circuit breaker QF7 and circuit breaker QF8.

[0014] Preferably, the second-stage motor includes motor M3 and motor M4, the corresponding second incoming circuit breaker includes circuit breaker QF5 and circuit breaker QF6, and the corresponding second starting circuit breaker includes circuit breaker QF9 and circuit breaker QF10.

[0015] Preferably, the circuit breakers QF1-QF10 are all withdrawable vacuum circuit breakers in high-voltage switchgear.

[0016] Preferably, the motors M1-M4 are high-voltage asynchronous motors.

[0017] Preferably, the disconnect switches QS1 and QS2 are both high-voltage disconnect switches inside the high-voltage disconnect cabinet.

[0018] Preferably, the disconnecting switch QS3 is a high-voltage disconnecting trolley inside the high-voltage disconnecting cabinet.

[0019] Preferably, reactors L1 and L2 are synchronous reactors.

[0020] The beneficial effects of this utility model are as follows: By using the disconnecting switch QS3 as a connecting switch, the power distribution of the two starting busbars is realized, thereby enabling two frequency converters to control the soft start of multiple motors. The two frequency converters serve as backups for each other. Either frequency converter can perform soft start control for any selected motor after appropriate operation. It is not necessary to configure the same number of circuit breakers (switch cabinets) on the output side of each frequency converter as the total number of motors to select and start any motor. Compared with the existing solution, it can reduce the one-time investment of switch cabinet equipment, reduce the space occupation of the system, and reduce the complexity of the control circuit of the frequency converter soft start drive system. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the two-to-four frequency converter soft-start control circuit of this utility model;

[0022] Figure 2 This is a schematic diagram of an existing two-to-four inverter soft-start control circuit. Detailed Implementation

[0023] To facilitate a clear understanding of the technical means, creative features, objectives, and effects of this utility model, the following description, in conjunction with specific illustrations, further elaborates on this utility model.

[0024] like Figure 1 As shown, power distribution between the two starting bus sections (starting bus section I and starting bus section II) is achieved by using a high-voltage isolating trolley (isolating switch QS3) as a connecting switch. Two high-voltage frequency converters (VFD1 and VFD2), each high-voltage circuit breaker, the two starting bus sections, and four motors are interconnected to form a two-to-four frequency converter soft-start control circuit where the two frequency converters can mutually select and soft-start the four high-voltage motors. That is, the two frequency converters serve as backups for each other, and either frequency converter, through appropriate operation, can perform soft-start control for any selected high-voltage motor.

[0025] To better illustrate this system, the technical solution for soft-start control of four high-voltage motors using a two-to-four variable frequency soft-start control circuit will be explained below.

[0026] Circuit breakers QF1-QF10 are withdrawable vacuum circuit breakers in high-voltage switchgear.

[0027] Among them, circuit breakers QF1-QF6 are electrically connected to the high-voltage busbar, circuit breakers QF7 and QF8 are electrically connected to the first section of the starting busbar, and circuit breakers QF9 and QF10 are electrically connected to the second section of the starting busbar.

[0028] Disconnecting switches QS1 and QS2 are high-voltage disconnecting switches inside the high-voltage isolation cabinet.

[0029] Disconnecting switch QS3 is the high-voltage isolation trolley inside the high-voltage isolation cabinet, and disconnecting switch QS3 is the connecting switch between the two starting busbars.

[0030] Inverters VFD1 and VFD2 are high-voltage inverters, and reactors L1 and L2 are synchronizing reactors, forming two sets of high-voltage inverter soft-start devices, which serve as backups for each other. The power of the inverters is selected based on the maximum calculated result according to the different loads and motors.

[0031] Motors M1-M4 are high-voltage asynchronous motors.

[0032] By connecting two starting bus sections (Starting Bus Section I and Starting Bus Section II) using a high-voltage isolating trolley (isolating switch QS3), power distribution for the starting power of four motors (motors M1-M4) is achieved. This ultimately forms a two-to-four variable frequency soft-start control circuit where two frequency converters can selectively soft-start the four high-voltage motors. The two frequency converters serve as backups for each other, and either frequency converter, through appropriate operation, can perform soft-start control for any selected high-voltage motor. If operating conditions permit, after opening the high-voltage isolating trolley (isolating switch QS3), the two frequency converters can also start two different motors simultaneously.

[0033] Before the motor starts, all circuit breakers (circuit breakers QF1-QF10) and the high-voltage isolating trolley (isolating switch QS3) are initially in the "maintenance position", and the isolating switches (isolating switches QS1 and QS2) are in the open position.

[0034] The motor soft-start process is similar, taking VFD1 soft-start motors M1 and M3 as examples.

[0035] The process of starting motor M1 using frequency converter VFD1:

[0036] (1) After the process preparation of the motor M1 drive system is complete, first close the disconnect switch QS1, and then control the closing circuit breaker QF7 to select motor M1.

[0037] (2) Then remotely close the circuit breaker QF3. The frequency converter VFD1 is charged first. After the charging is completed and the self-test is completed, the frequency converter is "ready".

[0038] (3) When the frequency converter VFD1 receives the “start” command, it starts to accelerate according to the set parameters. Under no-load or light-load conditions, it drags the motor M1 to the power frequency of 50Hz. At this time, the frequency converter VFD1 automatically detects the voltage on the grid side and the motor side. When the voltage difference and frequency difference meet the threshold requirements, the frequency converter VFD1 enters the phase capture stage. When the phase difference between the two power supplies is the smallest, it issues a closing command to close the motor feeder switch circuit breaker QF1. At this time, the high-voltage bus of the power grid and the frequency converter VFD1 supply power to the motor M1 at the same time. When the frequency converter VFD1 detects that the circuit breaker QF1 is in the closed state, it controls the circuit breaker QF7 to open. At the same time, the frequency converter VFD1 locks the shutdown and opens the circuit breaker QF3, completing the entire start-up process of the motor M1. This process achieves seamless synchronous switching.

[0039] The process of starting motor M3 using frequency converter VFD1:

[0040] (1) When starting motor M3 with frequency converter VFD1, operate the high voltage isolation trolley (isolation switch QS3) to the "working position".

[0041] (2) When the process of the motor M3 drive system is ready, first control the closing circuit breaker QF9 to select motor M3.

[0042] (3) Then remotely close the circuit breaker QF3. The frequency converter VFD1 is charged first. After the charging is completed and the self-test is completed, the frequency converter VFD1 is "ready".

[0043] (4) When the frequency converter VFD1 receives the “start” command, it starts to accelerate according to the set parameters. Under no-load or light-load conditions, it drags the motor M3 to the power frequency of 50Hz. At this time, the frequency converter VFD1 automatically detects the voltage on the grid side and the motor side. When the voltage difference and frequency difference meet the threshold requirements, the frequency converter VFD1 enters the phase capture stage. When the phase difference between the two power supplies is the smallest, it issues a closing command to close the motor feeder switch circuit breaker QF5. At this time, the high-voltage bus of the power grid and the frequency converter VFD1 supply power to the motor M3 at the same time. When the frequency converter VFD1 detects that the circuit breaker QF5 is in the closed state, it controls the circuit breaker QF9 to open. At the same time, the frequency converter VFD1 locks down the motor, completing the entire start-up process of the motor M3. This process achieves seamless synchronous switching.

[0044] This system is not limited to the above-mentioned two-to-four variable frequency soft starter control circuit. When more motors need to be started, the two-to-four system can be expanded into a two-to-multiple variable frequency soft starter drive system by adding high-voltage circuit breakers to the corresponding starting bus sections. For example, a new motor can be connected to the high-voltage bus through a newly added circuit breaker, and the new motor can be connected to any starting bus section through the newly added circuit breaker. The more motors that need to be started, the more obvious the advantages of this system become, the more switchgear is saved, and the lower the complexity of the variable frequency soft starter drive system control circuit, making it easier to control.

[0045] like Figure 2 The diagram shows a schematic of a two-to-four inverter soft start control circuit. The four starting motors (M1-M4) require four circuit breakers connected to each of the four starting busbars, resulting in a large number of circuit breakers and complex control.

[0046] This system utilizes the disconnector switch QS3 as a tie switch to achieve power distribution between the two starting busbars, thereby enabling two frequency converters to control the soft start of multiple motors. The two frequency converters serve as backups for each other, and either frequency converter can perform soft start control for any selected motor after appropriate operation. It eliminates the need to configure the same number of circuit breakers (switchgear) on the output side of each frequency converter as the total number of motors. Compared with existing solutions, this reduces the one-time investment in switchgear equipment, reduces the system's space occupation, and also reduces the complexity of the control loop of the frequency converter soft start drive system.

[0047] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of protection claimed by this utility model. The scope of protection of this utility model is defined by the appended claims and their equivalents.

Claims

1. A variable frequency soft start drive system with segmented interconnection on the starting bus, characterized in that, This includes the high-voltage busbar, frequency converter VFD1, frequency converter VFD2, reactor L1, reactor L2, disconnector QS1, disconnector QS2, disconnector QS3, starting busbar section I, starting busbar section II, section I motor, and section II motor; The high-voltage busbar is electrically connected to the motor in section I through the first incoming circuit breaker, and the high-voltage busbar is electrically connected to the motor in section II through the second incoming circuit breaker. The high-voltage busbar is sequentially electrically connected to the frequency converter VFD1, reactor L1, disconnector QS1, and starting busbar section I via circuit breaker QF3, and sequentially electrically connected to the frequency converter VFD2, reactor L2, disconnector QS2, and starting busbar section II via circuit breaker QF4. The starting bus section I is electrically connected to the motor of section I through the first starting circuit breaker, and the starting bus section II is electrically connected to the motor of section II through the second starting circuit breaker. The starting bus section I is electrically connected to the starting bus section II via the disconnecting switch QS3.

2. The variable frequency soft start drive system with segmented interconnection on the starting bus as described in claim 1, characterized in that, The first section of motors includes motor M1 and motor M2, the corresponding first incoming circuit breakers include circuit breaker QF1 and circuit breaker QF2, and the corresponding first starting circuit breakers include circuit breaker QF7 and circuit breaker QF8.

3. The variable frequency soft start drive system with segmented interconnection on the starting bus as described in claim 2, characterized in that, The second-stage motors include motors M3 and M4, and the corresponding second incoming circuit breakers include circuit breakers QF5 and QF6, while the corresponding second starting circuit breakers include circuit breakers QF9 and QF10.

4. The variable frequency soft start drive system with segmented interconnection on the starting bus as described in claim 3, characterized in that, The circuit breakers QF1-QF10 are all withdrawable vacuum circuit breakers in high-voltage switchgear.

5. The variable frequency soft start drive system with segmented interconnection on the starting bus as described in claim 3, characterized in that, The motors M1-M4 are high-voltage asynchronous motors.

6. The variable frequency soft start drive system with segmented interconnection on the starting bus as described in claim 1, characterized in that, The disconnect switches QS1 and QS2 are both high-voltage disconnect switches inside the high-voltage disconnect cabinet.

7. The variable frequency soft start drive system with segmented interconnection on the starting bus as described in claim 1, characterized in that, The disconnector switch QS3 is a high-voltage isolation trolley inside the high-voltage isolation cabinet.

8. The variable frequency soft start drive system with segmented interconnection on the starting bus as described in claim 1, characterized in that, The reactors L1 and L2 are synchronous reactors.

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