Robust PI controller design for frequency stabilisation in a hybrid microgrid system considering parameter uncertainties and communication time delay

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. One of the major issues in the operation of an islanded microgrid is the frequency deviations caused by the variation of power production coming from non-dispatchable renewable energy sources. Using an appropriate control system may allow the system to deal with the frequency deviation and allow the system frequency to be restored to its rated value. A wide-area system frequency controller sends a control signal to each of the dispatchable generating sources to enforce the frequency control by using communication channels. However, the communication channels are susceptible to the time delays, which affect the performance of the frequency control system and potentially the system security. Also, the system parameters are uncertain due to the error in the modelling, variation in network topology, generations, loads etc. This study proposes a robust proportional and integral (PI) system frequency controller based on Kharitonov theorem (KT) considering the time delay of the communication system and the system parametric uncertainties. Simulation results demonstrate that the KT-based controller model has enhanced robustness compared to the conventional approaches of controller design.