Resilient virtual inertia strategy for frequency support of renewable-based microgrids using a variable structure fuzzy PID controller

Ensuring frequency stability in low-inertia microgrids with high penetration of renewable energy sources (RESs) is a critical challenge, as these sources lack physical inertia and generate variable, unpredictable power. This leads to amplified frequency deviations, further aggravated by nonlinearities and stochastic behavior. Virtual inertia control, which emulates the inertial response of synchronous generators using energy storage, has emerged as a promising solution. However, conventional approaches often lack the responsiveness and robustness required to manage RES uncertainties and system nonlinearities, thereby limiting their effectiveness in dynamic environments. Moreover, the application of variable structure fuzzy logic controllers for load frequency control in renewable-dominated, low-inertia microgrids remains largely underexplored. To address these limitations, this paper proposes a variable structure fuzzy proportional-integral-derivative (VSC-FPID) controller designed for virtual inertia support in low-inertia microgrids. The proposed controller is tested under diverse loading scenarios and nonlinear conditions to ensure comprehensive evaluation. Its parameters are optimally tuned using the particle swarm optimization algorithm to guarantee efficient and robust dynamic performance. Comparative analysis with conventional PID and fuzzy-PID controllers demonstrates the superior capability of the VSC-FPID controller. Simulation results conducted in MATLAB confirm its robustness in regulating frequency under load fluctuations, RES uncertainties, and nonlinear system dynamics, including severe low-inertia and worst-case operating conditions involving simultaneous load and renewable disturbances. The proposed controller consistently outperforms benchmark methods, significantly improving transient and steady-state performance. Specifically, it achieves notable reductions in overshoot, undershoot, and settling time, with up to 60% improvement compared to the nearest competing technique. These results highlight the potential of the VSC-FPID-based virtual inertia control strategy as an effective solution for enhancing frequency stability in renewable-rich, low-inertia microgrids.