Robust current control scheme for single‐phase PWM rectifiers based on improved μ ‐synthesis in electric locomotive

Abstract

The parameter perturbation of grid-side equivalent inductance is a significant feature of the uncertainty in the single-phase pulse-width modulation rectifiers system for the electric locomotive. This characteristic tends to reduce the robustness of the rectifier system. This study handles these problems in the framework of the structured singular value, which helps to reduce the influence of model parameter perturbation, caused by measurement error and operation condition change, on the robustness. However, the conventional μ-synthesis robust controls only reflect tracking and anti-disturbance performance by weighting functions and ignoring the dynamic response performance. Herein, a direct current control (DCC) scheme based on improved μ-synthesis is proposed. A desired closed-loop transfer function is introduced to the conventional μ-synthesis control structure to ameliorate the performance of the dynamic response. Furthermore, considering the external disturbances on the system control output, a suitable weighting function is used to restrict the external disturbance. The input–output relationship of the generalised open-loop plant can thus be constructed accordingly. The proposed control scheme is compared with the widely applied proportional–integral-based DCC scheme and the conventional μ-synthesis DCC scheme. Hardware-in-the-loop experiment results show promising dynamic performance as well as stronger robustness against parameter perturbation and external disturbances.