A Flexible Synchronous Switching Method for High-Voltage Frequency Converters

Abstract

The invention discloses a method for flexible synchronous switching of a high-voltage frequency converter, which relates to the field of high-voltage frequency converters. In the stage where the high-voltage frequency converter drives a motor alone, the method first controls the motor to run stably at the grid frequency in an open-loop VF mode, and then adjusts the reactance The output voltage of the inverter at the front end of the reactor changes the voltage at the rear end of the reactor to track the grid voltage and keep the amplitude and phase of the grid voltage consistent before cutting into the grid and entering the stage where the high-voltage inverter and the power frequency grid jointly drive the motor. This approach The voltage at the back end of the reactor remains basically unchanged before and after the power grid is cut in, so that the impact on the motor and the power grid is smaller when the power grid is cut in, and the impact on the power grid, motor, and power devices is smaller than that of the ordinary synchronous switching method, especially in high-voltage large It is more worthy of use when the power drives the motor.

Description

technical field [0001] The invention relates to the field of high-voltage frequency converters, in particular to a method for flexible synchronous switching of high-voltage frequency converters. Background technique [0002] In the case of high-voltage and high-power drive motors, the current impact and torque impact generated by the direct start-up of the motor will have adverse effects on the power supply system and the drive system. Use a high-voltage frequency converter to drive the motor through a reactor to start from zero speed and gradually increase the voltage and speed until it reaches its rated speed, and then switch to power frequency grid power supply operation. [0003] However, in the existing synchronous switching process of frequency conversion and power frequency switching, the motor current fluctuates to a certain extent after the power frequency grid is cut in, the output current of the high-voltage inverter drops rapidly, and the current of the power fre...

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Problems solved by technology

[0003] However, in the existing synchronous switching process of frequency conversion and power frequency switching, the motor current fluctuates to a certain extent after the power frequency grid is cut in, the output current of the high-voltage inverter drops rapidly, and the current of the power frequency grid rises rapidly to provide current for the motor. The power factor is lower than that of the high-voltage inverter, so the switching will have a certain impact on the power frequency grid, especially the power frequency grid with small capacity will have a negative impact, and the rapid change of the reactor current will also cause Generates high voltages that adversely affect power devices

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