Control and Modulation Method for Leakage Current Mitigation in Single-Phase Non-Isolated EV Charger

Recently, electric vehicle (EV) charging technology has been evolved to address the environmental challenges, with a particular attention to the non-isolated EV chargers for their potential to improve efficiency and reduce both size and cost. However, the absence of an isolation barrier in the system raises the challenge of human safety and electromagnetic compatibility. This paper conducts a detailed analysis of common mode voltage (CMV), identifying the impact of various CMV sources on leakage current. To mitigate the leakage current, a direct leakage current control method is proposed, which employs low frequency CMV injection by a power converter. The leakage current flowing into the ground wire is directly measured and utilized as a feedback of the controller. Then, the CMV reference of the power converter is synthesized by a proposed two-dimensional space vector pulse-width modulation (2DSVPWM). The high frequency CMV ripple is minimized by utilizing only two voltage levels. The effectiveness of the proposed methods is validated through experiments with a single-phase two/three-level AC-DC converter, demonstrating the attenuation of both high and low frequency leakage current.