Comprehensive Analysis of a Flyback Converter for Voltage Equalization of Battery Strings

Battery energy storage systems has been used in many applications involving distributed generation and microgrids. Due to the low voltage level of a single battery, the batteries are connected in series as a string. Since the voltage level of an individual battery can suffer overvoltage during the charging/discharging processes, a voltage equalization system must be implemented. In the literature, it is possible of identifying Flyback converter as one of the most selected converters as voltage equalizer. However, the theoretical analysis of the Flyback converter in this application is not profound and then, the design equations are not presented. This paper presents a comprehensive analysis of the Flyback converter for the voltage equalization of a battery string. It is presented the operating stages, main ideal waveforms, design equations and preliminary experimental results of a Flyback converter operating with 48 V input/output voltage, 100 W rated power, 50 kHz switching frequency for the voltage equalization of four 12 V-battery string.