This paper proposes a robust method for frequency control in an islanded microgrid facing solar unit uncertainties. Here, microgrids with photovoltaic panels, battery energy storage systems, diesel generators, and fuel cells are considered. This paper focuses on the frequency constancy of stand-alone microgrids for reaction to these uncertainties. There are so many ways to control the frequency of microgrids, such as the PI control method, but these methods can't be useful in the case of uncertain systems. Due to the small scale of energy generation, the microgrid inertia changes with these uncertainties. Robust control is a method for frequency control that can be used in a situation of uncertainties, perturbations and frequency instability. In this article H_∞ frequency control is used for a microgrid with a dual peak load profile in the case of different coefficient penetrations of the solar panel. The results demonstrated that the battery energy storage system's coefficient penetration and the solar cell significantly affect microgrid frequency. A smart algorithm is proposed to determine the best coefficient penetration value for battery energy storage system available electricity and solar panels. Manuscript profile