State of charge and state of power management in a hybrid energy storage system by the self-tuned dynamic exponent and the fuzzy-based dynamic PI controller

The study converges the system stability for the steady-state and transient state simultaneously. The battery and compressed air storage systems are considered to address the steady power demand, on the other hand, flywheel and supercapacitor-based storage unit functions to minimize the transient system fluctuation. The study derives the integrated state variables of the hybrid unit to implement the proposed control strategies. The paper proposes a self - tuned dynamic exponent control strategy to regulate the charge equalization among the battery and compressed air, as they possess a large energy per unit volume. Similarly to regulate the high power content of the flywheel and supercapacitor, a fuzzy tuned dynamic PI is proposed. The proposed strategies ensure an efficient decentralized control among the hybrid units. The designed system under study integrated with the control strategies is tested under the critical operational constraints of load and generation. Further the improvement of the system stability is analyzed using the Nyquist's stability criterion.