4. Dynamic Security Assessment of Low-inertia Microgrids Based on the Concept of Virtual Inertia Control

Renewable energy sources (RESs) are growing rapidly and highly penetrated in microgrids (μGs). However, there are some impacts resulting from integrating RESs such as power fluctuations caused by the intermittent nature of RESs, and lack of system inertia resulting from replacement of synchronous generators with RESs. Hence, in order to cope with this challenge and benefit from a maximum capacity of the RESs, this chapter presents a new frequency control strategy based on a virtual inertia control to emulate virtual inertia into the μG control loop, thus stabilizing μG frequency during high penetration of RESs. Moreover, the proposed virtual inertia control system based on an optimal proportional–integral (PI) controller is coordinated with digital over/underfrequency relay to improve the frequency stability and maintain the dynamic security of the μG considering high penetration of RESs. The studied system simulation results are conducted using MATLAB/Simulink^® software to validate the efficacy of the proposed coordination scheme. Results endorsed that the proposed coordination scheme can efficiently regulate the μG frequency and ensure robust performance to maintain the dynamic security of μG with high penetration of RESs for various contingencies.