CRA Based Robust Digital Current Controller for AC/DC PWM Converter

This paper proposes a robust digital current control method using characteristic ratio assignment (CRA) for a single phase parallel AC/DC PWM converter using in electric train. CRA has the ability to deal directly with the overshoot and speed of step response in an all-pole system with arbitrary order, which is based on certain relationships between the coefficients of characteristic polynomial and the transient responses. Such CRA method is applied to PWM converter to overcome the sampling limit in a usual digital system, which causes the stability problem and slow response speed. And error-space feedback approach is used to keep very low AC current tracking error and no phase delay. Finally the validity of proposed controller is verified through the PSiM simulation and experimental results.