Enhancement in the operation of wind turbine based induction generator by using fuzzy logic based direct torque control

Abstract

This paper compares fuzzy logic controller with conventional PI controller based direct torque control (DTC) for a wind turbine induction generator set. The voltage controlled gating pulses to inverter are of variable frequency by using carrier based PWM with reference to sinusoidal waveform to achieve desired results. The torque and flux estimation block and speed error control block are the heart for this control system. The analysis is developed by using MATLAB/ SIMULINK. The proposed fuzzy based technique is used to maintain smooth torque transform and maintains desired torque even though there is change in generator speed or vice-versa. The system stability and current extraction can be improved by using FLC than PI controller, even under sudden changes in speed and torque of the machine. The torque ripples were less for both PI and FLC based controller scheme compared to previous techniques. Torque surges due to sudden change in speed of machine can also be minimized by using proposed fuzzy controller scheme. The comparisons of PI with FLC for wind turbine based induction generator were studied under 2 cases, in 1st case, constant generator speed and variable change in wind speed, torque and in the 2nd case, variable speed generator and variable speed of wind.