Battery balancing algorithm for parallel operation of single phase UPS inverters

A current sharing method considering battery state of charge (SOC) for single phase uninterruptable power supply (UPS) module is proposed. Each of UPS module system is consists of single master and multi slave modules. A master module performs output voltage control and current sharing algorithm considering the battery SOC of each of the UPS modules. In current sharing algorithm, current commands are generated for eliminating SOC difference of batteries of each modules. However, the slave modules control the only output current which is generated by master module. As the output load current is shared by battery SOC of UPS module, the utilization of the battery is increased in parallel UPS system. The validity of proposed method is verified by simulation results.