Model Predictive Control of a New Common-Mode Current Free EV Charger with a Wide Output Voltage Range

Non-isolated electric vehicle (EV) chargers are gaining popularity due to their enhanced efficiency, power density, reduced cost and smaller footprint. However, the lack of an isolation barrier in the charging system poses challenges such as the generation of a large common-mode (CM) current and touch current hazards, which cause serious safety concerns for the end-user. On the other hand, an EV charger should have a wide output voltage range to support different EV battery pack voltages. This paper presents a new non-isolated EV battery charger that minimizes CM current and ensures compatibility with a wide voltage range of EV battery packs. The proposed topology comprises two stages: an AC-DC converter stage for power factor correction (PFC) and a DC-DC converter stage for charging the battery at its nominal voltage. The AC-DC converter stage consists of a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\boldsymbol{3}-\phi$</tex>, four-wire full-bridge converter with a split DC-link, whose midpoint is connected to the mains neutral. This provides very stable potential at the DC-link rails. The DC-DC converter stage consists of a three-level (3L) buck converter. The discrete-time model of the proposed charger is derived and employed in the model predictive control algorithm to control the charger effectively. The simulation results are presented to verify the operation and performance of the proposed charger.