Integrated Transformerless EV Charger With Symmetrical Modulation

This article introduces a modulation technique that nearly eliminates the common-mode (CM) leakage currents in the transformerless (nonisolated) dual-inverter single-phase charger. This improvement allows for the safe use and commercialization of the transformerless charger, making superior charger efficiency, power density, and cost possible. The CM model of the system is derived to guide the choice of the modulation scheme. Simulations are conducted to validate the CM performance predictions derived analytically. Finally, an experimental 6.6-kW charger prototype is presented to verify the CM leakage current elimination. The experimental results show not only that the proposed modulation meets the required standards regarding CM currents, but also that it does so by a wide margin, and it even outperforms the isolated system used for comparison.