A single phase grid integration scheme for battery-supercapacitor AC line hybrid storage system

A transformerless direct single phase grid-connected battery-supercapacitor hybrid energy storage system based on a modified boost inverter configuration and its associated control strategy are proposed in this paper. The proposed control strategy comprises a double loop output voltage controller, active and reactive power droop controller, battery state of charge (SOC) management system based on the extended Kalman filter (EKF) and supercapacitor voltage controller. Simulation results confirm that the proposed system is able to deliver or absorb the required active power and reactive power to or from the grid while allocating the ripple current to the supercapacitor. Furthermore, the system maintains the supercapacitor voltage at a pre-defined value while operating the battery inside a safe operating SOC range.