Grey wolf optimization approach for enhancing the transient stability of microgrid using fractional-order PID-based inertia injection controller

High penetration of inverter-based renewable energy sources (RESs) in the microgrid reduces the system inertia. As a result, sudden load fluctuations or unwanted disturbances in the power network increase the rate of change of frequency and this may lead to system instability. Virtual inertia (VI) controller with energy storage system is generally used to improve system inertia and frequency stability of the microgrid. Existing several VI controllers are able to improve the transient performance of the system, but these solutions come with increased settling time and increased steady-state error. To improve the transient performance, a concept of power injection controller is developed. In this paper, an inertia injection controller based on fractional-order proportional-integral-derivative (FOPID-IIC) is proposed to improve the system transient performance. This controller injects inertia power to the microgrid associated with photovoltaic system to improve transient stability and to reduce settling time. The parameters of proposed controller are optimized by Grey wolf optimization technique. Furthermore, the performance of the proposed controller has been analysed and its superiority has been established compared to conventional VI control methods for different loading conditions considering high RES injection. Effect of nonlinearities like governor dead band, and generation rate constraints on the system performance is also studied.