This paper suggested a robust frequency control in an isolated microgrid system. Renewable energy sources, load changes and wind power fluctuations can extremely effect on the frequency of microgrid system. So, there are a few challenges have been emerged in case of facing the microgrid frequency control issue. In response to these challenges, a new robust technique called Electro-Search Optimization has been introduced in this paper for optimal online tuning of the controller's gains. The proposed system has been examined on the controller's performance and robustness in presence of various step load perturbation and change in wind power. Final results are compared with particle swarm optimization technique and conventional integral controller. It is shown that the adaptive Electro-Search Optimization approach due to considering parametric/structured uncertainties gives superior robustness and performance than particle swarm technique and fixed - integral control.