Design of a 22-kW Transformerless EV Charger With V2G Capabilities and Peak 99.5% Efficiency

This article outlines the design process of a high-efficiency (99.5% peak) transformerless dc electric vehicle fast charger in conjunction with relevant standards on conducted harmonics and leakage current. The topology is a nonisolated transformerless design which allows for the elimination of the additional transformer volume and losses that are present in galvanically isolated topologies. Methods for calculating optimal switching frequency and inductance to minimize loss as a function of chosen switching device and power level are provided. Filter sizing and component values are chosen in conjunction with the previously determined optimal switching frequency and inductance. Heatsink design rationale are then derived. Experimental efficiency, switching waveforms, and output voltage and current quality results are provided. Industrial topology feasibility is shown through experimental adherence to relevant underwriters laboratories (UL), international electrotechnical commission (IEC), institution of engineering and technology (IET), and institute of electrical and electronics engineers (IEEE) standards.