Frequency control in an islanded hybrid microgrid using frequency response analysis tools

Abstract

A hybrid microgrid has numerous decentralised control loops. Therefore, coordination among hybrid microgrid subsystems with desired performance is essential. This study presents a practical control approach for efficient tuning of proportional–integral (PI) controllers and leads compensators in islanded hybrid microgrids. This method is based on the frequency response characteristic and root-locus trajectory. It is used to minimise the frequency deviations of an AC hybrid microgrid. The presented well-tuned controllers are tuned based on droop mechanism, and coordination among hybrid microgrid subsystems with desired damping coefficient and stability margin. Then, the system performance is analysed under several disturbances. The results are compared with PI controllers tuned by Ziegler–Nichols method. As well, the robustness of the proposed approach in a wide range of parameter changes is investigated. Eigenvalue analysis and simulation results show that the minimum frequency deviations and desired relative stability of the hybrid microgrid subsystems are achieved by the proposed controllers. To show generality and efficiency of the proposed approach, the presented method is applied to a different hybrid microgrid model used in the literature. For this purpose, in order to control the frequency deviations in the stand-alone mode, presented well-tuned controller is compared with intelligent fuzzy and particle swarm optimisation-fuzzy controllers.