Direct Power Control of Grid Connected Double-Fed Induction Generator in Wind Energy Conversion System

Abstract

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 is presented. 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 modeling of the Doubly Fed Induction Generator (DFIG) system is discussed in this paper. The power is controlled by rotor current injection. The controlling scheme is explained and the modeling of the complete system is done in MATLAB-SIMULINK. The performance of this control technique is observed in wind power applications. Optimum power control and pitch angle control for wind turbine is proposed and the response of generator speed, pitch angle, optimum power, turbine torque, stator current, stator and rotor powers for different wind speeds are shown by simulation results. The direction of stator and rotor power flow is explained with simulation results.