High-voltage variable-frequency soft start control circuit structure

Abstract

The utility model discloses a high pressure frequency conversion soft start control circuit structure belongs to high pressure frequency converter technical field. Including high voltage bus I section, high voltage bus II section, high voltage bus III section, motor M1, motor M2, frequency converter VFD1, frequency converter VFD2, electric reactor L1, electric reactor L2, starting bus. Through the utilization disconnecting switch (high voltage isolation trolley car) realizes the power distribution of high voltage bus I section, high voltage bus II section and the power distribution of starting bus, and then realizes the frequency conversion two -in -one soft start function of two motor unit's high voltage motor control system, need not switching two bus power supply, also need not gathering starting motor's voltage mutual inductor PT signal of bus section, compared with traditional frequency conversion soft start scheme, can reduce high voltage switchgear's one -time investment, improve the utilization efficiency of equipment, reduce the occupation of high voltage motor control system to space, reduce the complexity of motor drive system and frequency conversion soft start system simultaneously.

Description

Technical Field

[0001] This utility model relates to a high-voltage frequency converter soft-start control circuit structure, belonging to the technical field of high-voltage frequency converters. Background Technology

[0002] With the widespread use of high-voltage motors, the starting problem of these motors has gradually become a major challenge for users' internal power grids. High-voltage, high-power AC motors, in particular, have large starting currents, and direct starting can cause a significant drop in grid voltage, affecting the normal operation of other equipment on the same grid. There are various starting methods to choose from, and different methods not only affect the initial investment of the project but also the long-term safe and stable operation of the factory's internal power grid.

[0003] Among them, high-voltage frequency converters, as a starting method, can achieve soft starting of high-voltage, high-power AC motors. Compared with traditional water resistance and solid-state soft starters, high-voltage frequency converters have more technical advantages: no impact on the unit and the power grid; greater starting torque can be obtained while limiting current; the system is simple and easy to maintain; multiple units can share a single frequency converter for soft starting, reducing investment costs; and excellent control performance makes it easy to achieve automated control.

[0004] Currently, in practical applications, multiple production lines are often equipped simultaneously, each consisting of several main motor devices connected to the same or different power busbars. Whenever a single high-capacity device or multiple devices on the same busbar start, the power busbar voltage drops significantly, sometimes exceeding -15%, affecting the normal operation of other devices on the same busbar. Therefore, to ensure the safety and reliability of the power grid supply system and motor control system, a variable frequency soft-start scheme with two or more frequency converters as backups is required. This necessitates providing multiple power sources to the frequency converter input side from both high-voltage busbar sections I and II, and configuring multiple high-voltage switchgear on the frequency converter output side to select from multiple motors. As the number of switchgear increases, not only does the initial investment in the high-voltage switchgear equipment increase, but the complexity of the high-voltage switchgear control logic also rises. Therefore, a high-voltage variable frequency soft-start control circuit structure was designed to solve these problems. Summary of the Invention

[0005] The technical problem to be solved by this utility model is to provide a high-voltage variable frequency soft start control circuit structure, which solves the problems of high cost and complex control logic in the current variable frequency soft start scheme with two or more frequency converters as backups for each other.

[0006] The technical problem to be solved by this utility model is achieved by the following technical solution:

[0007] A high-voltage variable frequency soft start control circuit structure includes a high-voltage bus section I, a high-voltage bus section II, a high-voltage bus section III, a motor M1, a motor M2, a frequency converter VFD1, a frequency converter VFD2, a reactor L1, a reactor L2, and a starting bus.

[0008] The high-voltage bus section I is electrically connected to the high-voltage bus section III via circuit breaker QF1, and the high-voltage bus section I is electrically connected to the motor M1 via circuit breaker QF2;

[0009] The high-voltage busbar section II is electrically connected to the high-voltage busbar section III via circuit breaker QF3, and the high-voltage busbar section II is electrically connected to the motor M2 via circuit breaker QF4;

[0010] The high-voltage bus section III is connected to the starting bus in sequence via disconnector QS3, frequency converter VFD1, and reactor L1. The high-voltage bus section III is connected to the starting bus in sequence via disconnector QS4, frequency converter VFD2, and reactor L2.

[0011] The starting bus is electrically connected to motor M1 via circuit breaker QF5, and the starting bus is electrically connected to motor M2 via circuit breaker QF6.

[0012] Preferably, circuit breaker QF1 is electrically connected to high-voltage bus section III via disconnector switch QS2, and circuit breaker QF3 is electrically connected to high-voltage bus section III via disconnector switch QS1.

[0013] Preferably, electrical interlocks are provided between circuit breakers QF1 and QF3, between disconnectors QS1 and QS2, between disconnectors QS3 and QS4, and between disconnectors QS5 and QS6.

[0014] Preferably, the disconnecting switches QS1-QS6 are all high-voltage disconnecting trolleys installed inside the high-voltage disconnecting cabinet.

[0015] Preferably, both frequency converters VFD1 and VFD2 are high-voltage frequency converters.

[0016] Preferably, both motor M1 and motor M2 are high-voltage asynchronous motors.

[0017] Preferably, reactors L1 and L2 are both synchronous reactors.

[0018] Preferably, the circuit breakers QF1-QF6 are all withdrawable high-voltage vacuum circuit breakers.

[0019] The beneficial effects of this utility model are:

[0020] 1. By utilizing disconnecting switches (high-voltage disconnecting trolleys), power distribution is achieved for high-voltage bus section I and high-voltage bus section II, as well as for the starting bus. This enables the variable frequency two-to-two soft start function of the high-voltage motor control system for two motor units. There is no need to switch the power supply of the two bus sections, nor is it necessary to collect the voltage transformer (PT) signal of the bus section where the starting motor is located. Compared with the traditional variable frequency soft start solution, it can reduce the one-time investment of high-voltage switchgear, improve the utilization efficiency of equipment, reduce the space occupation of the high-voltage motor control system, and reduce the complexity of the motor drive system and the variable frequency soft start system.

[0021] 2. Excellent scalability: When multiple motors need to be started on high-voltage bus section I and high-voltage bus section II, the two-to-two system can be expanded into a two-to-multiple variable frequency soft start control circuit by adding motors to the starting bus. When multiple motors need to be started on multiple bus sections, a disconnecting switch can be added to high-voltage bus section III as the incoming cabinet of the frequency converter, and a disconnecting switch can be added to the starting bus section as the starting cabinet of the motor, thereby expanding it into a multi-to-multiple variable frequency soft start control circuit. Attached Figure Description

[0022] Figure 1 This is a circuit diagram of the present invention;

[0023] Figure 2 A schematic diagram of an existing two-to-two soft starter control circuit with multiple high-voltage switchgear.

[0024] Figure 3 This is a schematic diagram of an existing two-to-two soft-start control circuit with a voltage transformer (PT). Detailed Implementation

[0025] 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.

[0026] like Figure 1 As shown, the power distribution of the segmented power supply bus (high voltage bus section I and high voltage bus section II) and the power distribution of the starting bus section are realized by using high voltage isolation trolleys (isolation switches QS1-QS6).

[0027] Specifically, the following components are included: two high-voltage frequency converters (VFD1 and VFD2), each high-voltage circuit breaker (QF1-QF6), a high-voltage isolating trolley (isolating switches QS1-QS6), segmented busbars (high-voltage busbar section I and high-voltage busbar section II), and two motors (motors M1 and M2). Figure 1The two inverters are electrically connected to form a two-to-two inverter soft-start control circuit that allows two inverters to selectively soft-start two motors. That is, the two inverters serve as backups for each other, and either inverter, through appropriate operation, can perform soft-start control for any selected motor.

[0028] To better illustrate this utility model, the technical solution for soft-start control of two high-voltage motors using a two-to-two variable frequency soft-start control circuit is described below. Two-to-two variable frequency soft start refers to two frequency converters starting two motors. Two-to-multiple variable frequency soft start refers to two frequency converters starting multiple motors.

[0029] Circuit breakers QF1-QF6 are withdrawable vacuum circuit breakers in high-voltage switchgear.

[0030] Disconnecting switches QS1-QS6 are high-voltage isolation trolleys inside the high-voltage isolation cabinet.

[0031] Circuit breakers QF1 and QF2 are electrically connected to section I of the high-voltage busbar, and circuit breakers QF3 and QF4 are electrically connected to section II of the high-voltage busbar.

[0032] Disconnecting switches QS1-QS4 are electrically connected to section III of the high-voltage busbar, and disconnecting switches QS5 and QS6, circuit breaker QF5, and circuit breaker QF6 are electrically connected to the starting busbar.

[0033] Electrical interlocks are provided between circuit breakers QF1 and QF3, between disconnectors QS1 and QS2, between disconnectors QS3 and QS4, and between disconnectors QS5 and QS6. These electrical interlocks mean that two switches in the same group cannot be in the closed state at the same time.

[0034] Both frequency converters VFD1 and VFD2 are high-voltage frequency converters, and both reactors L1 and L2 are synchronous reactors, forming two sets of high-voltage frequency converter soft start devices, which serve as backups for each other. The power of the frequency converters is selected based on the maximum load during application. Both motors M1 and M2 are high-voltage asynchronous motors.

[0035] By utilizing four high-voltage isolating trolleys (isolating switches QS1-QS4) to distribute the power from high-voltage bus section I and high-voltage bus section II into high-voltage bus section III, which supplies power to two high-voltage frequency converters (frequency converters VFD1 and VFD2), and by using two high-voltage isolating trolleys (isolating switches QS5 and QS6) and two high-voltage circuit breakers (circuit breakers QF5 and QF6) to form a starting bus section, the power distribution for starting the two motors is achieved. This ultimately constitutes a two-to-two frequency converter soft-start control circuit where two frequency converters can mutually select and soft-start two 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.

[0036] Since frequency converters operate intermittently when used as soft starters, and only one frequency converter is in operation at any given time, if two frequency converters (VFD1 and VFD2) and the high-voltage switchgear (circuit breakers QF1-QF4) of the segmented power bus (high-voltage bus section I and high-voltage bus section II) are in the same room and close to each other, the isolating switches QS1 and QS2 can be removed. The circuit breaker trolleys of circuit breakers QF1 and QF3 can be switched to the "maintenance position" or "operating position" to achieve mutual isolation between the two frequency converters.

[0037] Before the motor starts, all high-voltage circuit breakers and high-voltage isolation trolleys are initially in the "maintenance position".

[0038] The soft-start process for each motor is similar; for example, the VFD1 inverter soft-starts motor M1.

[0039] (1) After the process preparation of the motor M1 drive system is complete, the corresponding circuit breakers QF1, QF2 and disconnecting switches QS2, QS3, QS6 and circuit breaker QF6 are operated to the "working position".

[0040] (2) First, control the circuit breaker QF6 to close to select motor M1, then remotely control the circuit breaker QF1 to close. The frequency converter VFD1 will charge first. After charging is completed and self-test is completed, the frequency converter is "ready".

[0041] (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 QF2. At this time, the high-voltage bus section I 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 QF2 is in the closed state, it controls the circuit breaker QF6 to open. At the same time, the frequency converter VFD1 locks and stops the motor, completing the entire starting process of the motor M1. This process achieves seamless synchronous switching. Finally, the circuit breaker QF1 is disconnected as needed.

[0042] When the frequency converter VFD1 needs to start the motor M2, the above operations are required for circuit breakers QF3 (equivalent to QF1), QF4 (equivalent to QF2), QF5 (equivalent to QF6), disconnecting switch QS1 (equivalent to QS2), and disconnecting switch QS3 (equivalent to QS4).

[0043] This soft start control circuit structure is not limited to the above two-to-two inverter soft start control circuit. When multiple motors need to be started on two bus sections, the two-to-two system can be expanded into a two-to-multiple inverter soft start control circuit by adding a high-voltage circuit breaker on the starting bus section. When multiple motors need to be started on multiple bus sections, a high-voltage isolating trolley (isolating switch) can be added to the high-voltage bus section III as the inverter's incoming line cabinet, and a high-voltage isolating trolley (isolating switch) can be added to the starting bus section as the motor's starting cabinet, thereby expanding it into a multi-to-multiple inverter soft start control circuit.

[0044] like Figure 2 The diagram shows an existing two-to-two soft-start control circuit with multiple high-voltage switchgear. It requires providing two power supplies to the input sides of the frequency converters (VFD1 and VFD2) on both high-voltage busbar I and high-voltage busbar II, and configuring two high-voltage switchgear (circuit breakers) on the output side of each frequency converter to select between two motors (motor M1 and motor M2). The two-to-two soft-start control is achieved through ten high-voltage switchgear (circuit breakers QF1-QF10), which increases the complexity of the control logic of the high-voltage switchgear and also increases the initial investment in the high-voltage switchgear equipment.

[0045] like Figure 3 The diagram shows a schematic of an existing two-to-two soft-start control circuit with voltage transformers (PTs). It requires frequency converters (VFD1 and VFD2) to collect the secondary voltage signals of the voltage transformers (PTs) on each bus section. This can save two high-voltage switchgear units. However, the frequency converters need to be equipped with a voltage disconnection detection circuit to ensure that they do not trip erroneously when the secondary voltage circuit of the voltage transformers (PTs) is disconnected, increasing the complexity of the secondary circuit and the control complexity of the motor control system.

[0046] This soft-start control circuit structure significantly reduces the number of high-voltage switchgear units used, while the use of a lower-cost high-voltage isolation trolley can still meet the soft-start requirements. Multiple bus sections are powered by a circuit breaker to supply power to high-voltage bus section III, which in turn powers the frequency converter. The motor is then started using a starting bus connected to the frequency converter. This results in a clearer control logic and allows for easy expansion.

[0047] By utilizing a high-voltage isolation trolley to achieve power distribution across the segmented power supply bus and the starting bus section, the variable frequency two-to-two soft start function of the high-voltage motor control system for both units is realized. There is no need to switch the power supply between the two bus sections, nor is it necessary to collect the voltage transformer (PT) signal from the bus section where the starting motor is located. Compared to traditional variable frequency soft start solutions, this reduces the initial investment in high-voltage switchgear, improves equipment utilization efficiency, and reduces the system's space requirements. It also reduces the complexity of the motor drive system and the variable frequency soft start system.

[0048] 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 high-voltage variable frequency soft-start control circuit structure, characterized in that, It includes high-voltage busbar section I, high-voltage busbar section II, high-voltage busbar section III, motor M1, motor M2, frequency converter VFD1, frequency converter VFD2, reactor L1, reactor L2, and starting busbar; The high-voltage bus section I is electrically connected to the high-voltage bus section III via circuit breaker QF1, and the high-voltage bus section I is electrically connected to the motor M1 via circuit breaker QF2; The high-voltage busbar section II is electrically connected to the high-voltage busbar section III via circuit breaker QF3, and the high-voltage busbar section II is electrically connected to the motor M2 via circuit breaker QF4; The high-voltage bus section III is connected to the starting bus in sequence via disconnector QS3, frequency converter VFD1, and reactor L1. The high-voltage bus section III is connected to the starting bus in sequence via disconnector QS4, frequency converter VFD2, and reactor L2. The starting bus is electrically connected to motor M1 via circuit breaker QF5, and the starting bus is electrically connected to motor M2 via circuit breaker QF6.

2. The high-voltage frequency converter soft-start control circuit structure according to claim 1, characterized in that, The circuit breaker QF1 is electrically connected to the high-voltage bus section III via the disconnecting switch QS2, and the circuit breaker QF3 is electrically connected to the high-voltage bus section III via the disconnecting switch QS1.

3. The high-voltage frequency converter soft-start control circuit structure according to claim 2, characterized in that, Electrical interlocks are provided between circuit breakers QF1 and QF3, between disconnectors QS1 and QS2, between disconnectors QS3 and QS4, and between disconnectors QS5 and QS6.

4. The high-voltage frequency converter soft-start control circuit structure according to claim 2, characterized in that, The disconnect switches QS1-QS6 are all high-voltage isolation trolleys installed inside the high-voltage isolation cabinet.

5. The high-voltage frequency converter soft-start control circuit structure according to claim 1, characterized in that, Both frequency converters VFD1 and VFD2 are high-voltage frequency converters.

6. The high-voltage frequency converter soft-start control circuit structure according to claim 1, characterized in that, Both motors M1 and M2 are high-voltage asynchronous motors.

7. The high-voltage frequency converter soft-start control circuit structure according to claim 1, characterized in that, Both reactors L1 and L2 are synchronous reactors.

8. The high-voltage frequency converter soft-start control circuit structure according to claim 1, characterized in that, The circuit breakers QF1-QF6 are all withdrawable high-voltage vacuum circuit breakers.

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