Direct Leakage Current Control Method of Single-Phase Non-Isolated EV Charger

Recently, electric vehicle (EV) and its charging technology have been studied with the aim of improving environmental issues. Among them, a non-isolated charger is getting attention for its potential to enhance efficiency while reducing size and cost. However, the absence of an isolation barrier in the charging system raises the challenge of leakage current. Through a comprehensive analysis of common mode voltage (CMV), this paper identifies that a low-frequency CMV generates a leakage current and poses a touch current hazard, which is difficult to attenuate by passive filters. To overcome this issue, a novel direct leakage current control method is proposed which synthesizes low-frequency CMV using a power converter. The leakage current flowing into the ground wire is directly measured and employed as a feedback of the controller. Utilizing a plant model from the common mode equivalent circuit, the controller is designed in a form of band-pass filter. The proposed control method is verified through experiments using a single-phase AC-DC converter, attenuating touch current to satisfy IEC 61851-23 standard.