Research On Intelligent Reactive Power Compensator Based On Contactor Switched Capacitor At The Zreo-Crossing Point

This paper studies the solution of the negative effect of reactive power compensation device based on contactor switched capacitor, with the dynamic reactive power compensation of high voltage power grid under the conditions of slight load changes as the background. Research can effectively control the adverse effects of inrush current and voltage flicker generated by the capacitor at the switching transient moment, ensure that it meets the conditions of reactive power compensation system and achieves security and stability of the grid. This paper develops a research program of an intelligent reactive power compensation device based on contactor switched capacitor at the zero crossing point, builds a hardware control circuit of intelligent reactive power compensation and gives the relevant control strategies.The switching strategy for capacitor under grounded Y connection, ungrounded Y connection and triangle connection is proposed based on the analyses of the basic principles of contactor synchronous switching shunt capacitor. Through theoretical derivation of non-synchronous switching transient, the influence of ambient temperature on the response time of the contactor is discussed to give the design rules of reactance ratio at different conditions of current distortion rate, providing theoretical reference for the control of zero-crossing switching contactors.As the urgent requirement of the inhibition of the negative effect of contactor switched capacitor, a control system based on STM32F103VBT6 is build, including signal conditioning circuit, zero crossing point detection circuit, temperature detection circuit, driving circuit and data storage circuit, laying the hardware basis for the reactive power calculation and the relevant switching strategy.A voltage and current sampling signal detection algorithm is developed based on instantaneous reactive power theory, fully considering the grid accuracy requirement for the over-voltage and reactive power compensation, the improved sliding window iterative algorithm is taken to reduce accumulated error of the voltage and current detection signals, a switching strategy based on the improved nine domains method is put forward to analyze the software algorithm and system topology.Build contactor switched capacitor physical hardware platform. The variation of response time at the specific experimental conditions is taken as a reference volume to develop a C-based zero-crossing control algorithm. Simulation and experimental results show that the research can effectively control the capacitor switching at the zero crossing point, greatly reduce the transient shock at the contactor switching transient moment thus verifying the effectiveness and feasibility of proposed solutions.