Power conditioning system control strategy for cascaded H-bridge converter battery energy storage system

Large capability for a cascaded H-bridge converter battery energy storage system is one of the effective tools to solve the grid-connection problem of renewable energy resource such as large-scale wind farm. The power conditioning system (PCS) control strategy is used proportional-resonant regulator to implement the control with decoupled current control for instantaneous power. The balancing control of the state of charge (SOC) is divided into individual balancing control between bridges is implemented by means of the proportional controller and cluster control between three phases is based on the zero-sequence-voltage injection. The system designed in high-power medium voltage 6.6kV combining 30 LiFePO4 (lithium iron phosphate) battery units with cascaded H-bridge multilevel inverter. The simulation results of SOC balancing control was carried out. As a result, a steady-state error of PCS can be smaller and three-phase output power balancing has been achieved, thus, a system simulation model has verified the effectiveness of control strategy. The waveforms of PCS in quadrant operation show voltage and current at active power 1MW.