A Bidirectional Five-Level Buck PFC Rectifier With Wide Output Range for EV Charging Application

Abstract

AC-to-DC conversion is integral to the two-stage charging interface of electric vehicle (EV) batteries. For such chargers, the use of multilevel rectifiers (MLRs) reduces voltage ratings of power switches, while achieving a high-quality input voltage waveform. Balancing of capacitors in MLRs, however, is an important challenge. In this work, a power factor correction (PFC) five-level rectifier with self-balanced switched capacitors is proposed. Each leg of the presented topology comprises five power switches and one switched capacitor, where the voltage ratings of power switches are equal to the output dc voltage. It does not require an additional filter capacitor on the dc side, as the load appears in parallel always with a switched capacitor of one of the legs. The five-level operation with continuous conduction leads to the elimination of the capacitive filter on the ac-side and inductive filter on the dc-side. This article presents the operating principle, modulation strategy, closed-loop control, and design aspects of the proposed rectifier. The proposed topology is validated through experimental results and a comparison is made with other topologies. Following three features of the proposed topology make it suitable for EV battery charging applications—buck operation with a wide output regulation, the possibility of bidirectional flow of power needed for vehicle-to-grid systems, and easy realization of its three-phase version by simply adding one more leg. These features too have been demonstrated with experimental results.