Simultaneous Power Oscillation Damping and Frequency Control in AC Microgrid Considering Renewable Uncertainties: A Coordinated Control of Multiple Robust Controllers with Imperfect Communication

The large integration of renewable energy sources into power systems causes frequency fluctuation, low-frequency oscillations, and deterioration in power system stability. High penetration of wind and solar power also causes a high-frequency nadir and a high rate of change of frequency (ROCOF) after large disturbances. This paper presents a novel simultaneous power oscillation damping and frequency control in grid-connected AC microgrid while taking into consideration of the imperfect communication medium. The coordinated approach-based control scheme is used to enhance the frequency response as well as damping of low-frequency oscillations while maintaining the voltage and frequency in the prescribed range considering renewable uncertainties. In this proposed composite control, the power oscillation damping controller (POD) is based on reactive power modulation, whereas the frequency controller is based on active power modulation. The proposed POD and frequency controller is coordinated with the Linear Quadratic Gaussian (LQG) robust controller to enhance stability and mitigate the communication effect, noise, and time delay. The performance of the composite control scheme is compared by simulation of a grid-connected AC Microgrid by using MATLAB/Simulink software. The simulation result demonstrates the performance of the proposed controller over conventional droop controller for large power flow under different operating conditions, under\over frequency events, and under imperfect communication medium. Such grid support performance is expected to earn new revenue creating opportunities for AC microgrids.