Combination UFLS and UVLS Aim to Restore Frequency and Voltage Stability Simultaneously

Microgrids have become a popular technology in recent years due to their environmental compatibility. Microgrids can be operated in two modes: grid-connected and islanded. Due to the integration of this technology with distribution networks, ensuring the correct operation of microgrids is very important. The main challenge in the power grid is the balance between generation and consumption, which must always be under control. In the case of large-scale disturbances in the microgrid, the stability of the system is at risk and if not controlled, it can lead to collapse or even extended blackouts. Load shedding in the microgrid is performed with the aim of curtailing lower priority loads so that the balance between generation and demand is equalized and the stability of the system is maintained and restored. The main objective of this paper is to simultaneously use two important parameters, namely frequency and voltage, to evaluate the state of the network affected by islanding and overload. Using this method, it is possible to simultaneously restore the frequency and voltage in the islanded microgrid within the allowable range. The performance and effectiveness of this method have been simulated and investigated in a 13-bus IEEE network.