Islanded Microgrid Frequency Control Using Flywheel Energy Storage Considering Loss Optimization

The increasing penetration of renewable energy resources in islanded microgrids reduces system inertia and makes frequency stability more vulnerable to generation and load disturbances. Among available energy storage technologies, flywheel energy storage systems (FESSs) provide rapid bidirectional power exchange and are therefore well suited for primary frequency regulation. However, continuous operation at high rotational speeds produces considerable standby losses and reduces storage efficiency. This paper proposes an online control strategy that jointly addresses microgrid frequency regulation and FESS loss minimization. A nonlinear islanded microgrid model comprising a wind turbine generator, diesel generator, FESS, and dynamic loads is developed in MATLAB/Simulink. Using short-term wind speed forecasting and online operating-condition analysis, the proposed method determines the optimal FESS operating speed over each prediction horizon to reduce energy losses while maintaining sufficient power reserve for frequency support. The speed reference is continuously adjusted using a dedicated controller whose parameters are optimally tuned using the Particle Swarm Optimization (PSO) algorithm. Simulation results under varying wind and load conditions show that the proposed strategy maintains microgrid frequency stability while significantly reducing FESS energy losses compared with conventional frequency-control methods, thereby improving the overall operational efficiency of the islanded microgrid.