Comparison of the Performance of Vector Control and Direct Power Control of Induction Generator in Wind Energy Conversion System

Abstract

The conventional approach for independent control of active and reactive powers handled by the machine is stator flux oriented vector control with rotor position sensors. The performance of the system in this case depends on the accuracy of computation of the stator flux and the accuracy of the rotor position information derived from the position encoder. In vector control, power is controlled by rotor current injection. Direct power control is a rotor side control of a doubly fed induction generator by which decoupled control of stator active and reactive power can be obtained. It is based on the measurement of active and reactive power on the grid side where voltages and currents are alternating at fixed frequency. The active and reactive powers are made to track references using hysteresis controllers. The measurements are taken on stator side and the control is made on rotor side. This control system eliminates the need for rotor position sensing and gives an excellent dynamic performance with simulation results for a variable speed constant frequency induction generator system. The system can be operated below, at and above synchronous speed. The controlling schemes are explained and the modelling of the complete system is done in MATLAB–SIMULINK.