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

This paper proposes a new control structure for the grid-interfaced converters to enhance the ancillary services from the emerging electric vehicle (EV) charging stations (CS) under unbalanced and distorted grid conditions. Compared to the existing methods, the proposed control structure is relatively simple yet effective for both regulating the powers and minimizing the 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 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 to the local loads under unbalanced, harmonic distorted grid conditions.