Robust Online Fuzzy PID Design Based on Improved Differential Evolution for Islanded Microgrid Frequency Control Considering Nonlinear Factors and Uncertainties

In this paper, a robust fuzzy PID controller which is called online fuzzy PID (OFPID), for frequency control of an islanded microgrid is proposed. The proposed controller strategy is such that the fuzzy PID coefficients are automatically adjusted by fuzzy set theory at each time. To improve the performance of the proposed controller, the proposed improved differential evolution (IDE) algorithm which has suitable convergence speed in nonlinear functions optimization is used to optimal tune of its parameters including coefficients, membership functions, fuzzy rules weight and rules in three stages. To robust controller design in different operation points, the OFPID controller parameters is optimized by considering the uncertainties on some microgrid component parameters. The motivation for the proposed this control strategy is combination of fuzzy theory feature and IDE optimization algorithm to reduce control efforts and find better fuzzy system to achieve robust performance of microgrid frequency control. The test microgrid, is composed of distributed generation units such as diesel generators, photovoltaic, fuel cells with electrolyzer and wind turbine, as well as energy storage units such as flywheel and battery. In order to get closer to the frequency response of real microgrid, nonlinear factors on the distributed generation and energy storage sources have been considered. Simulation results by applying different disturbances show the good performance of the proposed OFPID controller than the optimized PID and classical fuzzy PID controllers.