CN-122026773-A - Alternating-current excitation system, speed changing unit and method for improving reliability of stator short-circuit switch

CN122026773ACN 122026773 ACN122026773 ACN 122026773ACN-122026773-A

Abstract

The invention relates to an alternating current excitation system, a speed changing unit and a method for improving the reliability of a stator short-circuit switch, belonging to the technical field of self-starting of speed changing energy storage units and aiming at solving the technical problems that the breaking time of the stator short-circuit switch is long and the service life is short; the capacitor is connected in the middle direct current link, the chopper is connected in the middle direct current link, each phase line of the unit side converter and the network side converter comprises a full-control power device and a free-wheeling diode, the power supply is cut off after the minimum rotation speed under the grid-connected condition of the power system is met in the self-starting process of the variable-speed energy storage unit, the free-wheeling diode in the unit side converter is converted into a rectifying module, and the alternating-current excitation system realizes the flux removal through the inversion of the network side converter, the chopper and the inversion of the network side converter and the chopper in the frequency conversion device.

Inventors

LIANG GUOCAI
WANG CHUN
WU PEIZHI
GUO XIAOYUAN
WANG XU
ZHENG YUCHEN
ZHANG YIHAO
WANG ZHIYUAN

Assignees

中国电建集团北京勘测设计研究院有限公司
河北丰宁抽水蓄能有限公司

Dates

Publication Date: 20260512
Application Date: 20260210

Claims (19)

1. The utility model provides an improve stator short circuit switch's alternating current excitation system, includes frequency conversion device, its characterized in that, frequency conversion device includes: The generator set side converter is in three-phase connection with a generator motor of the variable speed energy storage unit, and outputs a power source P1 with adjustable three-phase voltage and frequency to a rotor winding of the generator motor; The two ends of the middle direct current link are connected with the unit side converter; the capacitor is connected in the middle direct current link; the chopper is connected in the middle direct current link; each phase line of the unit side converter comprises two fully-controlled power devices connected in series, and each fully-controlled power device is connected with a freewheel diode in parallel; In the self-starting process of the variable speed energy storage unit, after the rotating speed of the variable speed energy storage unit is accelerated to the lowest rotating speed under the condition of meeting the grid connection condition with the electric power system, the power source P1 is cut off, the unit-side converter is converted into a rectifying module, and the alternating current excitation system realizes the flux removal through the rectifying module and a chopper in the frequency conversion device.
2. The AC excitation system of claim 1, wherein the capacitance is selected from the group consisting of an organic dielectric capacitor, an inorganic dielectric capacitor, an electrolytic capacitor, an electrothermal capacitor, and an air dielectric capacitor.
3. The alternating current excitation system of claim 1, wherein the freewheeling diode is selected from the group consisting of a normal rectifier diode, a fast recovery diode, a Schottky diode, and a high power freewheeling diode.
4. The ac excitation system of claim 1, wherein the chopper includes a chopper work switch and a chopper resistor, the chopper work switch being in series with the chopper resistor.
5. The utility model provides an improve stator short circuit switch's alternating current excitation system, includes frequency conversion device, its characterized in that, frequency conversion device includes: The generator set side converter is in three-phase connection with a generator motor of the variable speed energy storage unit, and outputs a power source P1 with adjustable three-phase voltage and frequency to a rotor winding of the generator motor; The two ends of the middle direct current link are connected with the unit side converter; the capacitor is connected in the middle direct current link; the two ends of the network side converter are connected with the middle direct current link; each phase line of the unit side converter comprises two fully-controlled power devices connected in series, and each fully-controlled power device is connected with a freewheel diode in parallel; In the self-starting process of the variable speed energy storage unit, after the rotating speed of the variable speed energy storage unit is accelerated to the lowest rotating speed under the condition of meeting the grid connection condition of the electric power system, the power source P1 is cut off, the unit side converter is converted into a rectifying module, and the alternating current excitation system realizes the flux removal through the inversion of the rectifying module and the grid side converter in the frequency conversion device.
6. The ac excitation system of claim 5, wherein each phase line of the grid-side converter comprises two fully-controlled power devices in series, each fully-controlled power device being connected in parallel with a freewheeling diode.
7. The utility model provides an improve stator short circuit switch's alternating current excitation system, includes frequency conversion device, its characterized in that, frequency conversion device includes: The generator set side converter is in three-phase connection with a generator motor of the variable speed energy storage unit, and outputs a power source P1 with adjustable three-phase voltage and frequency to a rotor winding of the generator motor; The two ends of the middle direct current link are connected with the unit side converter; the capacitor is connected in the middle direct current link; the chopper is connected in the middle direct current link; the two ends of the network side converter are connected with the middle direct current link; each phase line of the unit side converter comprises two fully-controlled power devices connected in series, and each fully-controlled power device is connected with a freewheel diode in parallel; In the self-starting process of the variable speed energy storage unit, after the rotating speed of the variable speed energy storage unit is accelerated to the lowest rotating speed under the condition of meeting the grid connection condition of the electric power system, the power source P1 is cut off, the unit side converter is converted into a rectifying module, and the alternating current excitation system realizes the flux removal through the rectifying module and a grid side converter inverter and a chopper in the frequency conversion device.
8. The ac excitation system of claim 7, wherein the chopper includes a chopper work switch and a chopper resistor, the chopper work switch being in series with the chopper resistor; Each phase line of the network side converter comprises two fully-controlled power devices connected in series, and each fully-controlled power device is connected with a freewheel diode in parallel.
9. The ac excitation system of claim 7, further comprising an excitation transformer in series with the frequency conversion device of the grid-side converter, the unit-side converter, the capacitor in the intermediate dc link, and the chopper.
10. The ac excitation system of claim 7, further comprising an ac circuit breaker in series with the excitation transformer.
11. The speed changing unit is characterized by comprising the alternating current excitation system for improving the reliability of the stator short-circuit switch, a generator motor, the stator short-circuit switch and a main transformer, wherein a stator winding of the generator motor is connected with the stator short-circuit switch; the alternating-current excitation system is connected in series between the main transformer and the generator motor; The input end of the alternating current excitation system is connected with a phase change switch, one end of the phase change switch is connected with a main transformer, and the other end of the phase change switch is connected with a generator circuit breaker.
12. The speed changing unit is characterized by comprising the alternating current excitation system for improving the reliability of the stator short-circuit switch, a generator motor, the stator short-circuit switch and a main transformer, wherein a stator winding of the generator motor is connected with the stator short-circuit switch; the alternating-current excitation system is connected in series between the main transformer and the generator motor; The input end of the alternating current excitation system is connected with a phase change switch, one end of the phase change switch is connected with a main transformer, and the other end of the phase change switch is connected with a generator circuit breaker.
13. The speed changing unit is characterized by comprising the alternating current excitation system for improving the reliability of the stator short-circuit switch, a generator motor, the stator short-circuit switch and a main transformer, wherein a stator winding of the generator motor is connected with the stator short-circuit switch; the alternating-current excitation system is connected in series between the main transformer and the generator motor; The input end of the alternating current excitation system is connected with a phase change switch, one end of the phase change switch is connected with a main transformer, and the other end of the phase change switch is connected with a generator circuit breaker.
14. A transmission set according to claim 11 or 12 or 13, wherein the phase change switch is connected in series with the generator circuit breaker.
15. A method for improving reliability of a stator shorting switch, applied to the speed changing unit of claim 11, comprising: Responding to a starting command of the unit, and pre-charging the variable frequency device, wherein after the pre-charging is finished; switching to a pumping working condition by using a phase change switch, and closing a stator short-circuit switch; The variable speed energy storage unit is started, and a starting power supply provides a power supply P1 with adjustable voltage and frequency for a rotor winding of a generator motor by an alternating current excitation system so as to increase the rotating speed of the unit; When the rotating speed of the unit rises to meet the minimum allowable rotating speed condition of the unit and the grid connection of the power system, the frequency conversion device stops providing the power supply P1 for the rotor winding; The unit side converter is converted into a rectifying module, and meanwhile, the working switch of the chopper is controlled to be conducted, so that the magnetic field energy stored in the stator winding is consumed in the form of heat energy on the chopper resistor; breaking the stator short-circuit switch when the current flowing through the stator short-circuit switch meets the set condition; After the stator short-circuit switch is disconnected, the frequency conversion device is put into operation again, the voltage, frequency and phase of the stator outlet end are regulated through control of the power supply P1, and after the unit meets the grid-connected condition with the power system, the generator breaker is closed, and the unit is connected with the power system; After the exhaust of the standby group volute is completed, the guide vane and the ball valve are opened, and active power is absorbed from the power grid, the self-starting of the pumping working condition of the unit is completed.
16. A method for improving reliability of a stator shorting switch, applied to the speed changing unit of claim 12, comprising: Responding to a starting command of the unit, and pre-charging the variable frequency device, wherein after the pre-charging is finished; switching to a pumping working condition by using a phase change switch, and closing a stator short-circuit switch; The variable speed energy storage unit is started, and a starting power supply provides a power supply P1 with adjustable voltage and frequency for a rotor winding of a generator motor by an alternating current excitation system so as to increase the rotating speed of the unit; When the rotating speed of the unit rises to meet the minimum allowable rotating speed condition of the unit and the grid connection of the power system, the frequency conversion device stops providing the power supply P1 for the rotor winding; The unit side converter is converted into a rectifying module, and meanwhile, the grid side converter in the frequency conversion device is subjected to inversion control, so that the magnetic field energy stored by the stator winding is fed back to the power system through the rectifying module, the grid side converter and the exciting transformer, and further the magnetic field energy consumption is realized; breaking the stator short-circuit switch when the current flowing through the stator short-circuit switch meets the set condition; After the stator short-circuit switch is disconnected, the frequency conversion device is put into operation again, the voltage, frequency and phase of the stator outlet end are regulated through control of the power supply P1, and after the unit meets the grid-connected condition with the power system, the generator breaker is closed, and the unit is connected with the power system; After the exhaust of the standby group volute is completed, the guide vane and the ball valve are opened, and active power is absorbed from the power grid, the self-starting of the pumping working condition of the unit is completed.
17. A method for improving reliability of a stator shorting switch, applied to the speed changing unit of claim 13, comprising: Responding to a starting command of the unit, and pre-charging the variable frequency device, wherein after the pre-charging is finished; switching to a pumping working condition by using a phase change switch, and closing a stator short-circuit switch; The variable speed energy storage unit is started, and a starting power supply provides a power supply P1 with adjustable voltage and frequency for a rotor winding of a generator motor by an alternating current excitation system so as to increase the rotating speed of the unit; When the rotating speed of the unit rises to meet the minimum allowable rotating speed condition of the unit and the grid connection of the power system, the frequency conversion device stops providing the power supply P1 for the rotor winding; The inverter control is carried out on a network side converter in the frequency conversion device, so that the magnetic field energy stored in the stator winding is fed back to the power system through the rectification module, the network side converter and the exciting transformer, and the consumption of the magnetic field energy part is further realized; after time delay, stopping the inversion control of the network-side converter in the frequency conversion device, and putting into a chopper; breaking the stator short-circuit switch when the current flowing through the stator short-circuit switch meets the set condition; After the stator short-circuit switch is disconnected, the frequency conversion device is put into operation again, the voltage, frequency and phase of the stator outlet end are regulated through control of the power supply P1, and after the unit meets the grid-connected condition with the power system, the generator breaker is closed, and the unit is connected with the power system; After the exhaust of the standby group volute is completed, the guide vane and the ball valve are opened, and active power is absorbed from the power grid, the self-starting of the pumping working condition of the unit is completed.
18. The method according to any one of claims 15 to 17, wherein, The time for which the current flowing through the stator short-circuit switch decays to meet the set condition is adjusted by changing the delay time for turning on the chopper operating switch and/or changing the resistance value of the chopper resistor.
19. The method according to any one of claims 15 to 17, wherein, The stator short-circuit switch is an alternating current switch.

Description

Alternating-current excitation system, speed changing unit and method for improving reliability of stator short-circuit switch Technical Field The invention relates to the technical field of self-starting of variable speed energy storage units, in particular to an alternating current excitation system for improving reliability of a stator short circuit switch, a variable speed unit and a method. Background With the rapid development of socioeconomic performance, the proportion of renewable energy sources in the power grid is continuously rising. Renewable energy sources such as wind power, photovoltaic power generation and the like have strong intermittence and uncertainty due to the influence of environmental factors such as geographic positions, climate conditions and the like, so that the problems of reduced power quality, increased frequency modulation peak staggering difficulty and the like are caused. In order to inhibit the fluctuation of the output of the intermittent power supply and ensure the reliable operation of a power grid, an energy storage power supply needs to be added in a power system. Pumped storage power stations are developed on a large scale due to their good adjustability and operational flexibility. At present, most of the pumped storage power stations adopt a conventional pumped storage mode, namely a synchronous motor is used, the motor rotation speed is fixed and can only run in a synchronous rotation speed state, and as the motor rotation speed cannot be adjusted, the power of the system cannot be adjusted, so that the running efficiency is reduced. The variable-speed pumped storage unit of the alternating-current excitation motor mainly comprises the capability of automatically tracking the frequency change of a power grid, continuously adjusting input power through smooth speed regulation under the working condition of a water pump, providing corresponding frequency automatic control capacity for a system, adjusting the rotating speed and active power by changing the frequency of the output voltage of an alternating-current excitation system, enabling the unit to work in an optimal operation area under the working condition of a water turbine, and enabling the variable-speed pumped storage unit to have wider adaptive water head and output power variation range and wider stable operation area, realizing zero-speed starting through short circuit of a stator winding without depending on expensive auxiliary equipment. The alternating-current excitation variable-speed energy storage unit mainly comprises a generator motor, an alternating-current excitation system, a main transformer and the like, and in the self-starting process of the alternating-current excitation variable-speed energy storage unit under the pumping working condition, the frequency conversion device of the alternating-current excitation system is firstly precharged and is switched to the pumping working condition, and a stator short-circuit switch of the generator motor is closed. The alternating-current excitation variable-speed energy storage unit starts the unit according to the asynchronous motor principle, and a starting power supply provides a power supply with adjustable voltage and frequency for a rotor winding by an alternating-current excitation system, so that the rotating speed of the unit is accelerated and improved. After the rotating speed of the unit rises to meet the minimum allowable rotating speed condition of the unit and the grid connection of the electric power system, stopping providing a power supply for the rotor winding, breaking the stator short-circuit switch when the current of the stator short-circuit switch is approximately zero, and after the stator short-circuit switch is disconnected. The frequency conversion device is put into operation again, the voltage, the frequency and the phase of the stator outlet end are regulated through the control of the power supply, after the unit meets the grid-connected condition with the power system, the unit and the power system are connected in a grid mode, the standby unit volute is exhausted, the guide vane and the ball valve are opened, and the active power is absorbed from the power grid, and the pumping working condition of the unit is started automatically. However, in the breaking process of the stator short-circuit switch, because the stator short-circuit switch is an alternating current switch, the allowable operation times, the safety and the service life of the switch can be ensured when the stator short-circuit switch works within the power frequency range. However, when the stator short-circuit switch is disconnected in a direct current state, the safety and the service life of the stator short-circuit switch are affected. When the stator short-circuit switch is in breaking operation in a direct current state, if the direct current value flowing through the stator short-circuit switch is too large, the stator short-circuit switch