Modular Battery Balancing and Power Flow Management Using Isolated Multi-Port DC-DC Converter with Active Power Sharing Control

This paper describes a Modular Multiport Converter (MMC), including an active charge balancing unit with isolated power converters while achieving the desired power exchange between the multi-ports of a common AC-link hybrid converter. The MMC includes multiple battery modules connected to individual H-bridges and interfaced to the common high-frequency AC link. The AC link consists of a multi-winding high-frequency transformer with multiple primary windings for the battery module H-bridges and a secondary winding for in-terfacing Electric Vehicle (EV) loads through another secondary H-bridge converter. The MMC control strategy includes a hybrid control approach, where active charge balance is achieved amongst the battery modules based on their State-of-Charge (SOC) using a Pulse Width Modulation (PWM) control. The individual duty ratios of the input-side H-bridges are selected for the active charge balancing based on their respective SOC levels. The hybrid control approach includes a single-phase shift control for achieving bi-directional power exchange between the input-side H-bridges and the secondary H-bridge while maintaining the EV terminal voltage. The effectiveness of the topology is validated using the PLECS simulation tool by analysing different battery packs and varying load and charging conditions with the proposed closed-loop control.