Research On Control Algorithm Of Power Quality Conditioner

In the low-voltage distribution network system,there are two major power quality problems: harmonics and three-phase unbalance,which always brings damage to the power system.The power quality conditioner is a power electronic device that is currently effective and widely used to suppress power quality problem,it has fast real-time performance,high compensation accuracy and strong anti-interference characteristics.At present,the research on three-phase three-wire power quality conditioner has matured,but most of China's distribution network adopts three-phase four-wire power supply line.Therefore,the research on the compensation of power quality problems by three-phase four-wire power quality conditioner begins gradually received attention.In this thesis,the three-phase four-wire power quality conditioner is taken as the research object,the four-bridge inverter is taken as the main circuit form,and the state space equation under low frequency state is established.The key technologies for studying three-phase four-wire power quality conditioner are: compensation current command signal detection algorithm and compensation current tracking control algorithm.In the ip-iq detection algorithm based on instantaneous reactive power,the Butterworth filter is commonly used for filtering.However,the inherent delay characteristics of the Butterworth filter make the detection algorithm less accurate in real time.Therefore,the ip-iq algorithm based on Kalman filter is proposed.And a discrete state equation and measurement equation for Kalman filter based on ip-iq transform are established.The ip-iq algorithm based on Kalman filter and Butterworth filter are compared by Matlab simulation.The real-time performance of the former is better than the latter.This thesis introduces the basic structure,principles,advantages and disadvantages of PID control and the working principle of Active Disturbance Rejection Control(ADRC).A compensation current tracking control based on nonlinear auto disturbance rejection control is proposed.According to the characteristics of ADRC,which does not depend on the exact model,can compensate the internal disturbance and external disturbance at the same time,the mathematical model suitable for the ADRC is constructed.The first-order nonlinear auto disturbance rejection controller is designed to tracking control the three phases A,B and C respectively.The tracking control of the N-phase is carried out by hysteresis comparison control.On this basis,the stability of nonlinear auto-disturbance is analyzed.Based on Matlab simulation platform,build a three-phase four-wire power quality conditioner simulation model.The compensation effects of nonlinear ADRC and PID control are analyzed by simulation.It is verified that nonlinear ADRC is superior to PID control in tracking speed,compensation effect and anti-interference characteristics.