Smooth switching and flexible quitting method and device for voltage sag treatment device

Abstract

The invention relates to a smooth switching and flexible quitting method and device for a voltage sag treatment device. When an energy storage converter is switched from a grid-connected mode to an off-grid mode for operation, the energy storage converter is enabled to output a voltage the same as a load voltage before sag through a voltage control loop in a control strategy, the mains supply is cut off from a power grid in cooperation with a thyristor gate pole control signal, and smooth switching of power supply of the mains supply to the energy storage converter is completed; when the energy storage converter is switched from the off-grid mode to the grid-connected mode, through the voltage control loop and an automatic synchronization control loop in the control strategy, the voltage of the energy storage converter and the voltage of the power grid are synchronized, a thyristor is triggered to be switched on, the current of the energy storage converter is slowly controlled to be reduced to the current during grid connection, and conversion between the energy storage converter and the power grid line is completed; and when the active power and the reactive power output by the energy storage converter are respectively smaller than threshold values, the energy storage converter flexibly exits. According to the invention, high-quality electric energy supply for a sensitive loadbefore and after sag is realized, and an energy storage converter is prevented from providing large impact current for the sensitive load.

Description

technical field [0001] The invention relates to the field of smooth switching and flexible exit of a voltage sag control device, in particular to a method and device for smooth switching and flexible exit of a voltage sag control device based on a voltage-type control strategy. Background technique [0002] The technical update of electrical equipment puts forward higher requirements for power supply quality, and voltage sag is one of the most frequently occurring and most serious power quality problems. In particular, short-term voltage sags can cause sensitive loads such as logic programmable controllers, precision mechanical tools, and semiconductor production lines to work abnormally or even damage equipment, causing huge economic losses to enterprises. Considering the current economic cost and technical difficulty of voltage sag control, the installation of voltage sag control equipment is the most commonly used voltage sag control technology for sensitive users, and th...

AI Technical Summary

Problems solved by technology

When the voltage sag occurs, the energy storage converter needs to switch its operation mode from PQ control to VF control. If the switch is improper, the impact voltage caused by the mode switch may occur and affect the normal operation of sensitive equipment.

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