Comparative Assessment of Hybrid Storage Configurations for Voltage and Frequency Support in an Islanded Renewable Microgrid

The increasing integration of renewable energy sources into islanded microgrids introduces operational challenges associated with power variability, limited conventional rotational inertia, and the need for effective energy storage management. Hybrid energy storage systems (HESS) provide a potential approach to addressing these challenges by combining technologies with complementary power and energy characteristics. This paper presents a comparative evaluation of five energy storage and control configurations in an islanded photovoltaic–wind–diesel microgrid comprising a 17 kW photovoltaic system, a 48 kW wind turbine, and a 100 kW diesel generator. The configurations investigated include a battery energy storage system (BESS) operating alone, BESS integrated with superconducting magnetic energy storage (SMES) under constant and dynamic droop control, and a combined BESS–SMES–supercapacitor (SC) system under both control strategies. Particular attention is given to the reported state-of-charge (SOC) operating ranges and total harmonic distortion (THD) results. The BESS-only configuration exhibits an SOC range of 5–92%, corresponding to a range width of 87 percentage points. In comparison, the BESS–SMES–SC configuration employing enhanced dynamic droop control operates within a reported SOC range of 48–74%, giving a range width of 26 percentage points. This represents a 61-percentage-point reduction in SOC-range width relative to the BESS-only configuration. The results suggest that combining complementary storage technologies with dynamic droop control can provide more constrained SOC operation within the configurations examined. The comparative analysis offers a basis for evaluating storage-system selection and control strategies in islanded renewable microgrids. Further validation of harmonic measurements and quantitative voltage and frequency responses is required to establish the broader power-quality and dynamic-stability implications of the findings.