Enhanced Performance of Charging Stations via Converter Control under Unbalanced and Harmonic Distorted Grids

Abstract

This article proposes a new control structure for grid-interfaced converters to enhance ancillary services from emerging electric vehicle (EV) charging stations (CS) under unbalanced and distorted grid conditions. Compared to existing methods, the proposed control structure is relatively simple yet effective for both regulating powers and minimizing harmonics under unbalanced and distorted grid conditions. A simple direct predictive control methodology is proposed where the positive fundamental component of currents is controlled for power regulation while other negative sequence or harmonic current components are set to zeros. Consequently, the charging station operation is enhanced with efficient ancillary services to the electric grid. The novelty originates from a simple predictive control structure in an abc-natural frame without adding any decoupled or separated current-component controllers. Comparative studies on both Matlab/Simulink platform and OPAL-RT-based real-time system among proportional integral (PI) control, finite predictive control, and the proposed method are conducted to verify the efficacy of the proposed structure. The comparative results show that the control structure improves the control performance and significantly enhances the support for the local loads under unbalanced, harmonic distorted grid conditions.