Power management control strategy for hybrid energy storage system in a grid-independent hybrid renewable energy system: a hardware-in-loop real-time verification

This study proposes a novel control strategy for a hybrid energy storage system (HESS), as a part of the grid-independent hybrid renewable energy system (HRES) which comprises diverse renewable energy resources and HESS - combination of battery energy storage system (BESS) and supercapacitor energy storage system (SCESS). The proposed control strategy is implemented into two parts: in the first part, HESS controller is designed and implemented to maintain the active power balance among different constituents of HRES and regulate DC-link voltage (V-DC) under surplus power mode and deficit power mode. The low-frequency components of imbalance power are diverted to BESS while the high-frequency components are diverted to SCESS while maintaining the state of charge (SoC) constraints of HESS thereby reducing stress on BESS. In the second part, inverter controller is designed and implemented to maintain AC voltage and frequency within limits in the events of perturbation. The proposed HESS along with its novel control strategy, as implemented in the HRES, is a new proposition in this study. The detailed model of HRES is simulated in MATLAB/Simulink and the results prove the efficacy of the control strategy. Further, hardware-in-loop real-time simulation studies using OPAL-RT real-time simulator demonstrate the feasibility of hardware implementation of HRES with the proposed control strategy.