The main purpose of the present paper is to build a robust synergestic control of the permanent magnet synchronous machine (PMSM), that drives a flywheel to form an energy storage system that is integrated into a hybrid PV-wind system. The biggest inconvenience of the exploitation of clean sustainable sources like solar and wind energies is the continuous variation of the weather conditions, appearing as a frequent change in the wind currents (wind speed) and solar radiations. This problem causes a fluctuation in electricity production by the wind turbines and photovoltaic panels, which is a serious drawback particularly in the isolated standalone system when the system is incapable of generating demanding power. Thus, the use of hybrid system with more than one source, especially when it is supported by an energy storage system like FESS, is an effective solution for this drawback. It is able to re-generate power when the hybrid PV-wind system cannot generate enough electricity. Moreover, the synergetic control guarantees fast response, asymptotic stability of the closed-loop system in the all-range operating condition, and system robustness in presence of parameter variation. Computational simulation results confirm that the proposed method consistently outperforms other techniques and proves its effectiveness and benefits of using such a system.