This paper presents a control strategy for fuel cell/energy storage power generation system during voltage sag conditions. The hybrid DC power sources are connected to grid using power electronic converters include DC-DC converter and grid connected voltage source inverter. The power from hybrid power sources is controlled during voltage sag by designing of control strategy for DC-DC converter. Moreover, a robust control strategy of voltage source converter for both positive and negative symmetrical components is presented to control of inverter current under unbalanced voltage sag. Simulation results for 25 KW PEM fuel cell of TALEGHAN site are given to show the response of system under voltage sag and illustrate the performance including active power control and voltage sag ride-through capability of the proposed control strategy.