Three types of generator named wound rotor synchronous generator (WRSG), permanent magnet synchronous generator (PMSG) and doubly fed induction generator (DFIG) are usually used in variable speed horizontal axis wind turbines. Synchronous generator with controlled excitation voltage is a proper solution for power production in rotational speed lower than the nominal. In this paper, excitation voltage controller is designed to capture maximum energy of wind and pitch angle controller is designed to regulate the rotational speed of rotor when wind speed is over the rated value. Simulation results are verified by means of HIL (Hardware In the Loop) test setup. In this case, the function of controllers are examined in a turbulent wind condition on a simulator and the performance is analyzed. Finally, it is concluded that MPPT (Maximum Power Point Tracking) algorithm can be performed by controlling the excitation voltage of a synchronous generator in a below rated condition