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.

An electric vehicle (EV) charging system is usually implemented in two stages: a power factor correction (PFC) rectifier stage, followed by a DC-DC converter. For such power conversion, multilevel rectifiers (MLRs) offer advantages compared to a two-level rectifier, such as reducing voltage ratings of power switches and yielding high-quality input voltage waveform. In MLRs, one of the most challenging aspects is balancing the capacitors' voltages. This article proposes a self-balancing five-level PFC rectifier with the possibility of single/multiple outputs. The proposed rectifier performs buck operation and offers a wide output voltage regulation, which is suitable for EV battery charging. The five-level operation of proposed buck rectifier with continuous conduction mode (CCM) leads to elimination of the inductive filter on the DC side and the capacitive filter on the AC side. This article presents the operating principle, modulation strategy, closed-loop control and experimental validation of the proposed topology.

The battery charging power electronics interface of an electric vehicle (EV) must be capable of bidirectional power flow to enable both grid-to-vehicle (G2V) and vehicle-to-grid (V2G) operations. In the presence of a single/three-phase AC supply, the front-end of the EV charger employs a power factor correction (PFC) rectifier, which should have the bidirectional capability to facilitate V2G mode. A conventional active rectifier functions in boost mode while performing PFC and voltage regulation. In most of the currently available EVs, however, the battery nominal voltage is low and, hence, a downstream high step-down DC-DC converter and high voltage DC bus capacitor are required in the charging interface. To overcome these issues, this work proposes a bidirectional AC-to-DC buck rectifier topology that can operate in G2V and V2G modes, both in single- and three-phase versions. The proposed topology utilizes the switched capacitors principle to achieve self-balancing of voltages in the capacitors. In addition, it is highly modular in structure. This paper describes the proposed topology, its working and modulation and its applications. The hardware proto model is used to validate the proposed power converter and the control approach to achieve PFC and voltage regulation. In addition, a comparison with other topologies is presented to demonstrate its competence.

This paper proposes a new reduced switch-count power cell for a regenerative Cascaded H-Bridge (CHB) motor drive that reduces the number of switching devices per power cell from ten switches to six switches. The proposed power cell employs a Four-Switch Three Phase Inverter (FSTPI) at the front-end and a half-bridge inverter at the output of the power cell. The new configuration introduces four challenges: cell input current unbalance, input low order harmonics, DC-link voltage capacitor balancing, and switching harmonics. This paper analyzes and addresses these issues to ensure proper operation, control, and compliance with grid connection standards. The solutions are verified through simulation studies of a 3kV CHB motor drive and experimental validation with a single power cell setup. The results show the possibility of replacing the traditional power cell with a proposed cell, effectively reducing the required number of switches from ten to six.