A Coordinated Frequency Control in Microgrid Based on Asymmetric Synthetic Inertia Considering Rotational Speed of Wind Turbine

Abstract

AbstractFrequency regulation is an important issue in isolated microgrids with inertia‐less variable renewable energy sources such as wind turbines (WTs) or photovoltaics (PVs) due to the small inertia of the overall system. Synthetic inertia control (SI) using the kinetic energy of WT can provide the microgrid with virtual inertia to mitigate frequency fluctuations. In order to improve the performance of SI, the authors have proposed an asymmetric synthetic inertia control (ASI) in which the virtual moment of inertia is alternating depending on the system frequency and the rate of change of frequency. By increasing the control gain only when the system frequency is moving away from the nominal value, it is expected that ASI contributes to the faster convergence of frequency control. However, another issue is interference between ASI and the rotational speed control for maximum power point tracking of WT. Hence, in this study, a coordinated frequency and rotational speed control strategy was proposed. The rotational speed control can be activated based on a mode‐switching logic when the interference does not occur. The effectiveness of the proposed control strategy was verified by numerical simulations using a microgrid model consisting of diesel engine generators, WTs, a photovoltaic, and a load. © 2023 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.