High-voltage frequency conversion system for starting permanent magnet synchronous motor

Abstract

A high-voltage frequency conversion system for starting permanent magnet synchronous motors comprises a high-voltage frequency converter and switching equipment, a plurality of 6kV power switch cabinets, permanent magnet synchronous motors A-F and a unit DCS control system, and the high-voltage frequency converter and switching equipment comprises a high-voltage frequency converter I, a high-voltage frequency converter II, an isolating switch QS21, an isolating switch QS22, an isolating switch QS23 and vacuum contactors KM11-KM16. The isolation switches are QS11 to QS16; starting and switching control commands of the high-voltage frequency converter and the switching equipment are from a unit DCS (Distributed Control System); the beneficial effects of the utility model are that the high-voltage frequency converter and the switching device can achieve the purpose of starting six permanent magnet synchronous motors in sequence, thereby saving the initial investment cost of the device; the high-voltage frequency converter I and the high-voltage frequency converter II are standby for each other, normal starting of the permanent magnet synchronous motor is not affected when one frequency converter breaks down, and the reliability of the starting system is high; the switching logic of the starting system of the permanent-magnet synchronous motor is clear and easy to realize.

Description

Technical Field

[0001] The utility model belongs to the technical field of high-voltage frequency converter application, and relates to a high-voltage frequency conversion system for starting a permanent magnet synchronous motor, including the composition and function of the system. Background Art

[0002] The traditional drive mode of medium-speed coal mills in thermal power plants generally adopts asynchronous motor + coupling + vertical shaft bevel gearbox (reducer) type. The motor is arranged horizontally and the coal mill is arranged vertically. The vertical shaft bevel gearbox realizes torque transmission and drive direction change. The drive chain is long and the efficiency is low. The rated capacity of the asynchronous motor is selected according to the rated operating conditions. Its nameplate power is relatively large. When the coal mill runs at a low load rate, the operating efficiency and power factor of the asynchronous motor drop significantly.

[0003] The rotor of the permanent magnet synchronous motor is a permanent magnet, without a rotor winding coil, and there is no rotor current during steady-state operation. Therefore, the permanent magnet synchronous motor has a high efficiency within the load range of 25% to 120% of the rated load. At the same time, the stator winding of the permanent magnet synchronous motor has a resistive load characteristic, and the power factor of the motor is close to 1. It can maintain a high power factor within the load range of 20% to 120%, and the energy-saving effect is significant when running at light load.

[0004] Although permanent magnet synchronous motors have the characteristics of high power factor and high operating efficiency, they cannot be started directly like asynchronous motors. Most permanent magnet synchronous motors need to adopt variable frequency starting method. The frequency converter changes the power frequency of the input motor, thereby changing the speed of the stator rotating magnetic field, and gradually increasing the frequency of the frequency converter output power supply. The motor speed increases accordingly until the permanent magnet synchronous motor is brought to the synchronous speed and the start is completed.

[0005] The number of medium-speed coal mills configured for each unit of a thermal power plant varies according to the size of the unit capacity. A 600MW unit is generally equipped with 6 medium-speed coal mills, and each coal mill is equipped with 1 permanent magnet synchronous motor. A high-voltage inverter is set to meet the starting requirements of the permanent magnet synchronous motor. If each permanent magnet synchronous motor is equipped with a set of high-voltage inverters, the wiring is simple and clear, but the high-voltage inverter is only used for starting. When the motor is operating normally, the high-voltage inverter is out of operation. The economic efficiency of this solution is poor. The number and wiring type of high-voltage inverters need to be determined by comprehensively considering the reliability, rationality and economy of the permanent magnet synchronous motor starting system. Utility Model Content

[0006] The utility model aims at an application scenario in which a unit of a thermal power plant is equipped with 6 medium-speed coal mills, each of which is driven by a permanent magnet synchronous motor. The purpose of the utility model is to provide a starting system that can meet the starting requirements of the permanent magnet synchronous motor and has high reliability, while taking into account the rationality and economy of the equipment configuration.

[0007] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0008] It includes a high-voltage frequency converter and switching equipment, several 6kV power switch cabinets, permanent magnet synchronous motors A~F and a unit DCS control system. The high-voltage frequency converter and switching equipment include a high-voltage frequency converter I, a high-voltage frequency converter II, an isolating switch QS21, an isolating switch QS22, an isolating switch QS23, vacuum contactors KM11~KM16, and isolating switches QS11~QS16; the high-voltage frequency converter I and the high-voltage frequency converter II of the high-voltage frequency converter and switching equipment are respectively connected to a 6kV power switch cabinet; the start-up and switching control commands of the high-voltage frequency converter and switching equipment come from the unit DCS control system, and the permanent magnet synchronous motors A~F are respectively connected to a 6kV power switch cabinet;

[0009] The 6kV power switch cabinet connected to the high-voltage frequency converter I is connected to the power input terminal of the high-voltage frequency converter I, the output terminal of the high-voltage frequency converter I is connected to the input terminal of the isolating switch QS21, the output terminal of QS21 is connected to the input terminals of the vacuum contactor KM11, the vacuum contactor KM12, the vacuum contactor KM13 and the isolating switch QS23, the output terminal of the vacuum contactor KM11 is connected to the input terminal of the isolating switch QS11, and the output terminal of the isolating switch QS11 is connected to the 6kV power supply connected to the permanent magnet synchronous motor A through a cable. On the switch cabinet; the output end of the vacuum contactor KM12 is connected to the input end of the isolating switch QS12, and the output end of the isolating switch QS12 is connected to the 6kV power switch cabinet connected to the permanent magnet synchronous motor B through a cable; the output end of the vacuum contactor KM13 is connected to the input end of the isolating switch QS13, and the output end of the isolating switch QS13 is connected to the 6kV power switch cabinet connected to the permanent magnet synchronous motor C through a cable; the output end of the isolating switch QS23 is connected to the output end of the isolating switch QS22 through a copper busbar;

[0010] The 6kV power switch cabinet connected to the high-voltage frequency converter II is connected to the power input end of the high-voltage frequency converter II, the output end of the high-voltage frequency converter II is connected to the input end of the isolating switch QS22, the output end of QS22 is connected to the input ends of the vacuum contactor KM14, the vacuum contactor KM15, the vacuum contactor KM16 and the output end of the isolating switch QS23, the output end of the vacuum contactor KM14 is connected to the input end of the isolating switch QS14, and the output end of the isolating switch QS14 is connected to the 6kV power switch cabinet connected to the permanent magnet synchronous motor D through a cable; the output end of the vacuum contactor KM15 is connected to the input end of the isolating switch QS15, and the output end of the isolating switch QS15 is connected to the 6kV power switch cabinet connected to the permanent magnet synchronous motor E through a cable; the output end of the vacuum contactor KM16 is connected to the input end of the isolating switch QS16, and the output end of the isolating switch QS16 is connected to the 6kV power switch cabinet connected to the permanent magnet synchronous motor F through a cable;

[0011] Permanent magnet synchronous motors A to F are connected to the 6kV power switch cabinet through cables;

[0012] The unit DCS control system sends the start / stop commands and switching commands to the high-voltage inverter and switching equipment through hard wiring. At the same time, the equipment operation and fault feedback information is sent to the unit DCS control system.

[0013] Furthermore, the several 6kV power switch cabinets are respectively equipped with 6kV vacuum circuit breakers, and the several 6kV power switch cabinets provide power for the high-voltage inverter I, the high-voltage inverter II and the permanent magnet synchronous motors A~F respectively.

[0014] Furthermore, the permanent magnet synchronous motors A to F correspond to one medium-speed coal mill respectively.

[0015] Furthermore, through the operator station of the control system, the operator of the unit DCS control system can manually control the start and stop of each permanent magnet synchronous motor and monitor the equipment operation status. The unit DCS control system sends the start, exit, and start switching commands to the high-voltage frequency converter I and the high-voltage frequency converter II; the closing and opening commands are sent to the vacuum contactors KM11~KM16, 6kV vacuum circuit breaker QF21 and 6kV vacuum circuit breaker QF22. At the same time, the equipment operation and fault feedback information are sent to the unit DCS control system.

[0016] The utility model has the following beneficial effects:

[0017] 1. One set of high-voltage frequency converter and switching equipment can realize the purpose of starting 6 permanent magnet synchronous motors in sequence, saving the initial investment cost of the equipment;

[0018] 2. High-voltage inverter I and high-voltage inverter II serve as backup for each other. If one inverter fails, it will not affect the normal starting of the permanent magnet synchronous motor. The reliability of the starting system is high;

[0019] 3. The switching logic of the permanent magnet synchronous motor starting system is clear and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Attached Figure 1 : A connection diagram of the utility model;

[0021] Attached Figure 2 : Wiring diagram of the utility model. DETAILED DESCRIPTION

[0022] Combined with the drawings of the utility model, the technical scheme of the implementation of the example new model is clearly and completely described. Obviously, the described implementation examples are only partial examples of the utility model, not all. Based on the specific implementation scheme of the utility model, other implementation examples obtained by ordinary technicians in this field without making creative improvements are all within the scope of protection of the utility model.

[0023] There are 8 6kV power switch cabinets, namely 6kV power switch cabinet 11, 6kV power switch cabinet 12, 6kV power switch cabinet 13, 6kV power switch cabinet 14, 6kV power switch cabinet 15, 6kV power switch cabinet 16, 6kV power switch cabinet 21 and 6kV power switch cabinet 22. Mainly considering that there are 6 feeders, they are numbered from 11 to 16, which makes it easy to identify different types of feeders.

[0024] See attached Figure 1 and Figure 2 , high-voltage frequency converter I, isolating switch QS21, isolating switch QS22, isolating switch QS11, isolating switch QS12, isolating switch QS13, vacuum contactor KM11, vacuum contactor KM12, vacuum contactor KM13 constitute high-voltage frequency converter and switching cabinet I; high-voltage frequency converter II, isolating switch QS23, isolating switch QS14, isolating switch QS15, isolating switch QS16, vacuum contactor KM14, vacuum contactor KM15, vacuum contactor KM16 constitute high-voltage frequency converter and switching cabinet II; high-voltage frequency converter and switching cabinet I and high-voltage frequency converter and switching cabinet II together constitute high-voltage frequency converter and switching equipment.

[0025] High-voltage inverter I and high-voltage inverter II are the core equipment of this utility model, which are required to have vector control function, high starting torque, good low-frequency torque characteristics, high frequency control accuracy, etc. For example, the BP series inverter of Jingji Technology Co., Ltd. can meet the starting requirements of permanent magnet synchronous motors.

[0026] 6kV power switch cabinet 21 and 6kV power switch cabinet 22: The cabinets are equipped with 6kV vacuum circuit breakers QF21 and QF22 to provide power for high-voltage inverters and switching equipment. The 6kV power switch cabinet 21 provides power for high-voltage inverter I, and the 6kV power switch cabinet 22 provides power for high-voltage inverter II.

[0027] 6kV power switch cabinets 11~16: 6kV vacuum circuit breakers QF11~QF16 are configured in the cabinets to provide normal operating power for the permanent magnet synchronous motors. Among them, 6kV power switch cabinet 11 provides power for permanent magnet synchronous motor A, 6kV power switch cabinet 12 provides power for permanent magnet synchronous motor B, 6kV power switch cabinet 13 provides power for permanent magnet synchronous motor C, 6kV power switch cabinet 14 provides power for permanent magnet synchronous motor D, 6kV power switch cabinet 15 provides power for permanent magnet synchronous motor E, and 6kV power switch cabinet 16 provides power for permanent magnet synchronous motor F.

[0028] The 6kV power switch cabinet 21 provides power to the high-voltage inverter 1 and is connected to the power input terminal of the high-voltage inverter 1. The output terminal of the high-voltage inverter 1 is connected to the input terminal of the isolating switch QS21. The output terminal of the isolating switch QS21 is connected to the input terminals of the vacuum contactors KM11, KM12, KM13 and the isolating switch QS23. The output terminal of the vacuum contactor KM11 is connected to the input terminal of the isolating switch QS11. The output terminal of the isolating switch QS11 is connected to the 6kV power supply through a cable. The switch cabinet 11 is connected; the output end of the vacuum contactor KM12 is connected to the input end of the isolating switch QS12, and the output end of the isolating switch QS12 is connected to the 6kV power switch cabinet 12 through a cable; the output end of the vacuum contactor KM13 is connected to the input end of the isolating switch QS13, and the output end of the isolating switch QS13 is connected to the 6kV power switch cabinet 13 through a cable; the output end of the isolating switch QS23 is connected to the output end of the isolating switch QS22 of the high-voltage frequency conversion and switching cabinet II through a copper busbar.

[0029] The 6kV power switch cabinet 22 provides power for the high-voltage frequency converter II and is connected to the power input terminal of the high-voltage frequency converter II. The output terminal of the high-voltage frequency converter II is connected to the input terminal of the isolating switch QS22. The output terminal of QS22 is connected to the input terminals of the vacuum contactor KM14, the vacuum contactor KM15, the vacuum contactor KM16 and the output terminal of the isolating switch QS23. The output terminal of the vacuum contactor KM14 is connected to the input terminal of the isolating switch QS14, and the output terminal of the isolating switch QS14 is connected to the 6kV power switch cabinet 14 through a cable; the output terminal of the vacuum contactor KM15 is connected to the input terminal of the isolating switch QS15, and the output terminal of the isolating switch QS15 is connected to the 6kV power switch cabinet 15 through a cable; the output terminal of the vacuum contactor KM16 is connected to the input terminal of the isolating switch QS16, and the output terminal of the isolating switch QS16 is connected to the 6kV power switch cabinet 16 through a cable.

[0030] The 6kV power switch cabinet 11 is connected to the permanent magnet synchronous motor A through a cable;

[0031] The 6kV power switch cabinet 12 is connected to the permanent magnet synchronous motor B through a cable;

[0032] The 6kV power switch cabinet 13 is connected to the permanent magnet synchronous motor C through a cable;

[0033] The 6kV power switch cabinet 14 is connected to the permanent magnet synchronous motor D through a cable;

[0034] The 6kV power switch cabinet 15 is connected to the permanent magnet synchronous motor E through a cable;

[0035] The 6kV power switch cabinet 16 is connected to the permanent magnet synchronous motor F through a cable.

[0036] The unit DCS control system sends the start / stop commands and switching commands to the high-voltage inverter and switching equipment through hard wiring. At the same time, the equipment operation and fault feedback information is sent to the unit DCS control system.

[0037] Starting and switching operation sequence of permanent magnet synchronous motor.

[0038] By adopting the configuration scheme of the utility model, permanent magnet synchronous motors A~F can be started in sequence according to the operation requirements. Isolating switches QS21, QS22, QS23, and QS11~QS16 are local manual operation devices, and the operation principle is as follows: when both high-voltage inverter I and high-voltage inverter II are available, close the isolating switches QS21 and QS22, and open the isolating switch QS23; when high-voltage inverter I is available and high-voltage inverter II is not available, close the isolating switches QS21 and QS23, and open the isolating switch QS22; when high-voltage inverter II is available and high-voltage inverter I is not available, close the isolating switches QS22 and QS23, and open the isolating switch QS21; if permanent magnet synchronous motors A~F need to be started, close the isolating switches QS11~QS16, and when a synchronous motor fails or is under maintenance, the corresponding isolating switch is placed in the open state.

[0039] Taking permanent magnet synchronous motor A as an example to illustrate the starting and switching operation sequence, the starting and switching operation sequence of other motors is similar. When the high-voltage frequency converter I is available, first close the 6kV vacuum circuit breaker QF21, close the vacuum contactor KM11, start the high-voltage frequency converter I, set the output power frequency of the high-voltage frequency converter I to 0.1Hz, drive the permanent magnet synchronous motor A to rotate, gradually increase the frequency of the output power supply, drag the rotor of the permanent magnet synchronous motor A to increase the speed until the rated speed is reached, and the unit DCS control system sends a start switching command to the high-voltage frequency converter I. After receiving the switching command, the high-voltage frequency converter I sends a signal to close the circuit breaker QF11 and open the vacuum contactor KM11. The permanent magnet synchronous motor A switches to the industrial frequency operation mode, opens the vacuum contactor KM11, exits the high-voltage frequency converter I, opens the vacuum circuit breaker QF21, completes the start of the permanent magnet synchronous motor A and switches to industrial frequency operation. If high-voltage inverter I is not available, but high-voltage inverter II is available, the permanent magnet synchronous motor A can be started by using high-voltage inverter II. First, close the 6kV circuit breaker QF22, close the vacuum contactor KM11, start the high-voltage inverter II, set the output power frequency of the high-voltage inverter II to 0.1Hz, drive the permanent magnet synchronous motor A to rotate, gradually increase the frequency of the output power, drag the rotor of the permanent magnet synchronous motor A to increase the speed until the rated speed is reached, and the unit DCS control system sends a start switching command to the high-voltage inverter II. After receiving the switching command, the high-voltage inverter II sends a signal to close the circuit breaker QF11 and open the vacuum contactor KM11. The permanent magnet synchronous motor A switches to the industrial frequency operation mode, opens the vacuum contactor KM11, exits the high-voltage inverter II, opens the vacuum circuit breaker QF22, completes the start of the permanent magnet synchronous motor A and switches to industrial frequency operation. In this way, the purpose of starting any permanent magnet synchronous motor with any high-voltage frequency converter is achieved. The failure of a single frequency converter will not affect the starting of the permanent magnet synchronous motor, thereby improving the reliability of the variable frequency starting system. Six permanent magnet synchronous motors are equipped with one set of high-voltage frequency converter and switching equipment, which meets the starting requirements of six permanent magnet synchronous motors. Compared with the configuration of six sets of frequency converters, the initial investment cost of the project is reduced and the economy is good. Therefore, the configuration scheme of using the "two-to-six" high-voltage frequency conversion system to start six permanent magnet synchronous motors has excellent reliability, safety and economy, and can be widely promoted and applied in similar projects.

Claims

1. A high voltage frequency conversion system for starting a permanent magnet synchronous motor, characterized in that: It includes a high-voltage frequency converter and switching equipment, several 6kV power switch cabinets, permanent magnet synchronous motors A~F and a unit DCS control system. The high-voltage frequency converter and switching equipment include a high-voltage frequency converter I, a high-voltage frequency converter II, an isolating switch QS21, an isolating switch QS22, an isolating switch QS23, vacuum contactors KM11~KM16, and isolating switches QS11~QS16; the high-voltage frequency converter I and the high-voltage frequency converter II of the high-voltage frequency converter and switching equipment are respectively connected to a 6kV power switch cabinet; the start-up and switching control commands of the high-voltage frequency converter and switching equipment come from the unit DCS control system, and the permanent magnet synchronous motors A~F are respectively connected to a 6kV power switch cabinet; The 6kV power switch cabinet connected to the high-voltage frequency converter I is connected to the power input terminal of the high-voltage frequency converter I, the output terminal of the high-voltage frequency converter I is connected to the input terminal of the isolating switch QS21, the output terminal of QS21 is connected to the input terminals of the vacuum contactor KM11, the vacuum contactor KM12, the vacuum contactor KM13 and the isolating switch QS23, the output terminal of the vacuum contactor KM11 is connected to the input terminal of the isolating switch QS11, and the output terminal of the isolating switch QS11 is connected to the 6kV power supply connected to the permanent magnet synchronous motor A through a cable. On the switch cabinet; the output end of the vacuum contactor KM12 is connected to the input end of the isolating switch QS12, and the output end of the isolating switch QS12 is connected to the 6kV power switch cabinet connected to the permanent magnet synchronous motor B through a cable; the output end of the vacuum contactor KM13 is connected to the input end of the isolating switch QS13, and the output end of the isolating switch QS13 is connected to the 6kV power switch cabinet connected to the permanent magnet synchronous motor C through a cable; the output end of the isolating switch QS23 is connected to the output end of the isolating switch QS22 through a copper busbar; The 6kV power switch cabinet connected to the high-voltage frequency converter II is connected to the power input end of the high-voltage frequency converter II, the output end of the high-voltage frequency converter II is connected to the input end of the isolating switch QS22, the output end of QS22 is connected to the input ends of the vacuum contactor KM14, the vacuum contactor KM15, the vacuum contactor KM16 and the output end of the isolating switch QS23, the output end of the vacuum contactor KM14 is connected to the input end of the isolating switch QS14, and the output end of the isolating switch QS14 is connected to the 6kV power switch cabinet connected to the permanent magnet synchronous motor D through a cable; the output end of the vacuum contactor KM15 is connected to the input end of the isolating switch QS15, and the output end of the isolating switch QS15 is connected to the 6kV power switch cabinet connected to the permanent magnet synchronous motor E through a cable; the output end of the vacuum contactor KM16 is connected to the input end of the isolating switch QS16, and the output end of the isolating switch QS16 is connected to the 6kV power switch cabinet connected to the permanent magnet synchronous motor F through a cable; Permanent magnet synchronous motors A to F are connected to the 6kV power switch cabinet through cables; The unit DCS control system is connected to the high-voltage inverter and switching equipment through hard wiring.

2. A high voltage frequency conversion system for starting a permanent magnet synchronous motor according to claim 1, characterized in that: The several 6kV power switch cabinets are respectively equipped with 6kV vacuum circuit breakers, and the several 6kV power switch cabinets provide power for high-voltage inverter I, high-voltage inverter II and permanent magnet synchronous motors A to F respectively.

3. A high voltage frequency conversion system for starting a permanent magnet synchronous motor according to claim 1, characterized in that: The permanent magnet synchronous motors A to F correspond to one medium speed coal mill respectively.

4. The high-voltage frequency conversion system for starting a permanent magnet synchronous motor according to claim 1, characterized in that: The DCS control system of the unit, through the operator station of the control system, the operating personnel can manually control the start and stop of each permanent magnet synchronous motor and monitor the equipment operation status. The DCS control system of the unit sends the start, exit and start switching commands to the high-voltage frequency converter I and the high-voltage frequency converter II; the closing and opening commands are sent to the vacuum contactors KM11~KM16, 6kV vacuum circuit breaker QF21 and 6kV vacuum circuit breaker QF22. At the same time, the equipment operation and fault feedback information are sent to the DCS control system of the unit.

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