A Hybrid Cascaded Multilevel Converter Based on Three-Level Cells for Battery Energy Management Applied in Electric Vehicles

In order to produce more voltage levels and meet the requirement of the motor drive in electric vehicles (EVs), a hybrid cascaded multilevel converter based on three-level (TL) cells is proposed in this paper. In each unit, there is a battery and two series-connected capacitors, which hold a half of the battery voltage, respectively. Each TL cell is controlled to be connected or bypassed by a converter unit because of the modular structure. Three voltage levels can be produced when the TL cell is connected. All TL cells are cascaded to produce a staircase dc voltage, and an H-bridge is utilized to alternate the direction of it to form the ac output voltage. Compared to similar converter based on half-bridge arms, the proposed topology is able to produce more voltage levels with same number of battery modules. Voltage balances among TL cells and between two capacitors in each TL cell are both realized by a proposed overall control strategy. Experiments are provided to show the validity of the analysis.