Influence of quadrature signal generation and current limitation on the performance of single-phase grid-forming EV chargers

This paper investigates the stability implications of quadrature signal generation methods for single-phase grid-forming (GFM) control in embedded electric vehicle (EV) chargers with small connection inductance. Two approaches are compared: the widely used Second-Order Generalized Integrator (SOGI) and the proposed Virtual Phase Generator (VPG). A pole-zero analysis reveals that SOGI-based implementations can introduce right-half-plane poles, leading to potential instability, whereas VPG ensures a stable closed-loop response across the studied parameter range. Building on this analysis, a current control strategy with dynamic saturation is proposed to protect the converter during severe grid disturbances. Simulation results confirm the method’s robustness, demonstrating smooth resynchronization, effective overcurrent limitation, and preservation of steady-state performance. These findings highlight the VPG-based approach as a reliable foundation for single-phase GFM control in EV chargers.