Advanced control and protection strategies for grid-forming inverters in microgrids—A review

The rising share of inverter-based resources and the associated decline in conventional inertia have intensified interest in grid-forming inverters (GFMIs), which emulate the dynamic behavior of synchronous generators by autonomously establishing local voltage and frequency. This review provides a comprehensive overview of GFMI modeling, spanning both conventional and advanced control strategies, as well as protection schemes that address limited fault-current capability and coordination challenges in low-inertia systems. We also examine different current-limiting and overload protection methods for safeguarding GFMI-based microgrids during severe faults, emphasizing how these approaches balance fast overcurrent suppression with preserving voltage-source behavior. By comparing these approaches under varying grid strengths and operating conditions, the article highlights the trade-off between fast overcurrent suppression and preserving voltage-source characteristics. Simulation results demonstrate that combined virtual impedance and current-limiting strategies enhance fault ride-through, reduce transient oscillations, and facilitate smooth grid support even at high renewable penetration. Through this consolidated discussion of modeling, control, and protection, the review identifies open questions in advanced GFMI design — such as optimized tuning of virtual parameters, multi-inverter coordination, and robust integration of current-limiting algorithms — and suggests future research directions to enable reliable, scalable deployment of GFMI-based solutions in modern power systems.