Load shedding scheme with under-frequency and undervoltage corrective actions to supply high priority loads in islanded microgrids

In the last few years, microgrids have become a potential solution to improve reliability and security in the supply of electricity to power systems. When a microgrid changes its operation mode from grid-connected to islanded, particular attention must be paid by the operation services. In the islanded mode, the microgrids' frequency and voltage may reach undesirable values, harming the security and quality of the operation. This study aims to propose global and local strategies of load shedding to preserve the energy supply to high priority loads within quality standards. The focus of this study is to consider a microgrid operating only with primary control. In this sense, a proper microgrid time-continuous load flow is applied, considering the constant verification of the frequency and the voltage of all buses. Finally, a Monte Carlo simulation is used to validate the proposal presented and to give some indices that quantify the load shed in each period. The results show the superior performance of the proposed strategy compared to a state-of-the-art load shedding solution that does not consider the priority of loads.