Renewable-fed islanded microgrids rely on cascaded photovoltaic (PV), battery energy storage system (BESS), DC–DC, and DC–AC conversion stages whose ability to maintain regulated load voltage is challenged by upstream outages, renewable shortfall, and compound power-quality disturbances. This paper presents a unified control framework for a dynamic voltage restorer (DVR) that enhances microgrid resilience by combining a synchronverter-based grid-forming reference generator, multi-resonant proportional-resonant controllers, and a supervisory mode-management layer. The proposed scheme coordinates standby, power-quality compensation, and voltage-interruption ride-through within a single architecture. In compensation mode, it mitigates sag/swell, unbalance, and harmonics at the critical-load bus. In interruption mode, it reconfigures the injection transformer and temporarily supplies the protected feeder from the local DC-link, thereby coupling renewable/storage-side energy conversion to AC-side continuity support. The method is evaluated in a MATLAB/Simulink model of a PV-BESS islanded microgrid with DC–DC converters, mixed grid-forming/grid-following inverters, and disturbance-producing loads, and is further validated through OPAL-RT/DSP hardware-in-the-loop experiments to demonstrate implementation feasibility. Under combined disturbances, load-voltage THD and VUF are reduced to 0.469% and 0.22%, respectively. During complete source interruption, restoration times of 14.2 ms for the instantaneous voltage and 32.2 ms for the RMS voltage are achieved with negligible overshoot. Under partial shading, causing a 38.9% PV-voltage drop and a 55.2% uncompensated DC-bus voltage drop, the protected load remains regulated at 1.0 p.u. with 0.0794% THD and 0.0265% VUF. The results show that the proposed controller extends conventional DVR functionality from power-quality compensation to resilience-oriented support in renewable-fed microgrids. |
