This paper investigates the influence of the measurement accuracy of the wind sensors on a wind energy conversion system (WECS) performance. Specifically, the wind speed and direction sensors installed at the end of the nacelle of a three blades horizontal axis wind turbine are considered. Due to the turbulence in the wake behind the wind turbine blades, wind direction measurement is highly affected; whereas, satisfactorily accurate measurement of the wind speed can be obtained from sensors at the rear part of the turbine. Moreover, any discrepancy caused by the rotating rotor at the wind speed measurement is known with satisfactory accuracy from the rotor aerodynamic model and thus, can be taken into consideration in the processing of the data obtained. Therefore, if the required information for both MPPT and yawing control is obtained by the wind speed, WECS can be driven to a satisfactory performance. On the contrary, if WECS operation and specifically yawing control is based on direct wind direction measurement with sensors installed at the rear part of the nacelle, may result to high discrepancies from the optimum performance. Thus, a combined control technique of accurate MPPT, optimization of the electrical generator efficiency and reliable yaw control can provide maximum electric energy production of the WECS and reduction of the cut-in wind speed towards the low wind speed range. Several simulation results are presented in order to demonstrate the effectiveness and operational improvement of the suggested control scheme.