单周控制三电平三相四桥臂APF研究

基于多电平的有源电力滤波器能产生多阶梯、低失真的电压波形,特别适合于高压大功率场合。为此提出一种单周控制的三电平三相四桥臂有源电力滤波器,它不需要三相负载电流检测以及繁琐的无功电流和谐波电流计算,控制器结构简单,仅由几个带复位的积分器、比较器、触发器和一些线性元件组成,具有控制精度高、补偿效果好的特点。滤波器工作于恒定开关频率,比较适合于推广到工业应用。在建立数学模型的基础上进行了仿真研究,仿真结果证明其能有效地补偿系统谐波,改善电流总谐波畸变率并提高输电线功率因数。

Study on One-cycle Control Three-level Three-phase Four-leg Active Power Filter

Multilevel active power filter(APF) that provides more than two voltage levels and less distorted waveform offers many benefits in high voltage and high power application field,so a three-level three-phase four-leg APF based on one-cycle control is presented.This scheme does not need any measured quantities of three-phase load currents,and also the complicated calculation of the harmonics and reactive current components are eliminated.By taking advantages of the pulsed and nonlinear nature of switching converters,this scheme achieves instantaneous dynamic control of the average value of a switched variable,more specifically,it takes only one switching cycle for the average value of the switched variable to reach a new steady-state after a transient.There is no steady-state error or dynamic error between the control reference and the average value of the switched variable.The controller is composed of some integrators with reset,flip-flops,comparators and linear components,having the characteristics of high precision and effectual compensation.In addition,it works under constant switching frequency modulation,thus,is desirable for industrial applications.Simulation is carried out on the basis of a mathematic model.The simulation results verify that the APF with one-cycle control can effectually compensate harmonics,improve total harmonic distortion and power factor of transmission lines.