Constant Power Operation Control of Variable Speed Wind Turbine DFIG using Genetic Algorithm

This paper presents a design of pitch controller using Genetic Algorithm (GA) for variable speed wind turbine Doubly Fed Induction Generator (DFIG) . The proposed genetic pitch controller is used to get the proper pitch angle for limiting the mechanical power when the wind speed is greater than the rated wind speed. DFIG is a wound-rotor induction generator where the stator terminals of DFIG are connected directly to the grid and the rotor terminals of DFIG are connected to the mains via a partially rated variable frequency ac/dc/ac converter. The ac/dc/ac converter system consists of a rotor side converter (RSC) and a grid side converter (GSC) connected back-to-back by a DC-link capacitor. The stator voltage orientation (SVO) control algorithms is utilized for RSC which is controlled by hysteresis current controller . While the GSC is controlled by pulse width modulation (PWM). Due to the nature of unpredicted wind speed, determining the right value of pitch angle of wind turbine to limit the mechanical power at any wind speed above the rated wind speed is essential. By controlling the pitch angle of the wind turbine blades, the rotational speed and the output power are regulated at constant value .The system under study is simulated using MATLAB/Simulink package. The digital simulation results under different conditions in terms of the variations of the wind turbine generator show that the output power, rotor speed and torque responses for step change in wind speed prove the effectiveness and powerful of the proposed GA controller for pitch control.