A flyback converter based partial power processing structure for BESS with voltage/current regulation and battery balancing functionalities

This paper presents a flyback converter based partial power processing structure for battery energy storage system (BESS). It combines both of the battery balancing functionality and power stage regulation functionality into one system. The proposed BESS only have one control variable which is the common duty cycle for all the flyback converters. It is used for the voltage or current regulation. There is no active control for the battery balancing because the current sharing of individual battery is directly proportional to the battery terminal voltage in discharging mode and inversely proportional in charging mode. The unbalanced battery terminal voltages will gradually converge while system running. Beyond these, only a small portion of the total discharging/charging power is processed by the converters. The overall system efficiency can be significantly improved compared to traditional BESSs. Experimental results of a prototype with two batteries verified that the proposed BESS provides satisfied performance.