Optimally Tuned Virtual Synchronous Generator-Based Hybrid SMES-RFB Energy Storage System for Enhanced Frequency Control in an Isolated Microgrid

This paper focuses on the frequency regulation issues in an isolated microgrid due to low system inertia and renewable power fluctuations. An improved Load Frequency Control (LFC) strategy is suggested using a Virtual Synchronous Generator (VSG)-based hybrid energy storage system integrating Superconducting Magnetic Energy Storage (SMES) and Redox Flow Battery (RFB) units. The Fractional-Order PID (FOPID) controller and the VSG parameters are optimally tuned with the recently developed African Vulture Optimization Algorithm (AVOA), using the Integral Time Absolute Error (ITAE) as the performance index. The effectiveness of the suggested algorithm is evaluated by comparison with the renowned Grey Wolf Optimization (GWO) algorithm. The results of MATLAB simulation under multiple scenarios indicate that the proposed microgrid frequency control model with a VSG-based hybrid energy storage unit employing an FOPID controller optimized by AVOA outperforms the other frequency control models consisting of a VSG-based SMES unit and a VSG-based RFB unit; additional validation is obtained through comparison with a conventional PID controller. The parameters variation analysis confirms the robustness of the proposed controller. In addition, the combination of the VSG-based hybrid energy storage unit with AVOA-optimized FOPID and VSG parameters leads to 83.44 percent enhancement in system's frequency response during the settling period as compared to LFC system with VSG-based SMES unit using FOPID controller and 72.53% when compared to the system with VSG-based RFB unit using FOPID controller. Finally, the effectiveness of the suggested system is verified through real-time simulation using the OPAL-RT (OP-4610) platform.