Research On The Increasing-state Feedback Control System Based On State Observer Of Three-phase Inverters

Digital control system of three-phase inverter is replacing analog system with more and more advantages. As while, digital control has unavoidable disadvantages, for example, maximum modulation ratio is restrained by the time delay of sampling time and execution time of control algorithm; although state feedback control based on pole-assignment method can improve the dynamic response of inverter, static characteristic is not satisfied. So the increasing-state feedback digital control scheme based on state observer is proposed to solve the problems above.This paper introduces a new state variable to the traditional state feedback control scheme based on pole-assignment method,this new state variable is good to improve the static characteristic of the inverter. Then the increasing-state feedback control schemes both in analog field and digital field for both single-phase inverter and three-phase inverter are presented. To avoid modulation limitation caused by the sampling and calculating time of digital processor, design of state observer is brought in.The two design methods of state observer are introduced, Only discrete method is suitable for one step advance. Key problem of state observer is discussed. Simulations and experiments all prove that the control scheme proposed above can achieve high-dynamic response, highly accurate steady output and less distorted waveform on a three-phase inverter.