Forecasting Based Virtual Inertia Control of PV Systems for Islanded Micro-Grid

Grid frequency stability is maintained by the power system inertia. However, as the converter interfaced photovoltaic (PV) generation increases, the system inertia reduces. This may result in system failures, especially for islanded micro-grid. Virtual inertial control (VIC) technology, which enables PVs to mimic the characteristics of synchronous generators (SG), has drawn increasing attention. Nevertheless, the implementation of a traditional VSG strategy typically requires a constant PV power reserve, causing unnecessary production loss during system steady states. Although VIC can also be effectively implemented by utilizing an energy storage system (ESS). The high cost is still hindering its large-scale integration. In this paper, a forecasting based virtual inertia control (FB-VIC) strategy is proposed, which enables the PV system to serve as an alternative inertia supplier without using any ESS. PV generation is pre-reserved based on the load forecasting results. The reserved PV power and SG are coordinated to perform frequency regulation. A simulation model is built to simulate the proposed FB-VIC method during a system contingency. The simulation results reveal that the proposed method can reduce the instantaneous SG power capacity over 40%. In addition, the proposed control method limits the frequency oscillation in a smaller range, which improves the system dynamic stability.