Coordinated Frequency Regulation Using Solar Forecasting Based Virtual Inertia Control for Islanded Microgrids

Power system inertia helps the grid to maintain frequency stability. However, as photovoltaic (PV) generation continuously displaces synchronous generators (SGs) and reduces system inertia, it may result in system failure. Virtual inertia control (VIC) technology has drawn increasing attention because it enables PVs to increase system inertia by mimicking the characteristics of SGs. Energy sources are needed to implement the VIC strategy. Energy storage systems (ESS) can be used to provide such energy. However, the high-cost is still hindering its large-scale adoption. Although constant reserve power in PV has recently been proposed as an alternative for ESS, it can cause unnecessary power losses during the PV system working at a stable state. This paper proposes a forecasting-based VIC (FB-VIC) and coordinated reserve strategy. FB-VIC enables the PVs to serve as an alternative inertia supplier without using ESS. PV generation is pre-reserved based on the solar forecasting results, either at PV plant about to be shaded for local curtailment or other unshaded PV plants providing virtual inertia. The coordinated reserve strategy decides how much to reserve at the selected PV plant. It makes the system more robust to forecasting errors. The simulation results reveal that the proposed method can improve system inertia and suppress the frequency variation in a shorter time.