A combined control strategy of a DFIG based on a sensorless power control through modified phase-locked loop and fuzzy logic controllers

This paper presents a study on a sensorless decoupled P-Q control for a doubly fed induction generator (DFIG)-based wind energy conversion system (WECS) with intelligent controllers via Matlab/Simulink. In the absence of mechanical sensors, an algorithm based on modified phase locked loop (MPLL) can estimate the rotor speed and position. An experimental validation of the proposed speed algorithm in steady state was conducted and is presented. In addition, this study focuses on the implementation of fuzzy logic controllers combined with the conventional PI (Proportional-Integral) for the adjustment of active power, reactive power, rotor speed and voltage in dc-link. The combination of fuzzy logic and PI concerns the use of the first as gain tuner of the second one, bearing in mind the significance and simultaneously the difficulty of gain finding. The simulation results of this study are presented to clarify the enhanced effectiveness of the combination of fuzzy logic with PI controllers. Finally, a comparative study between three control strategies, namely, case 1 - 'with mechanical sensors and PI controllers', case 2 - 'sensorless with PI controllers' and case 3 - 'sensorless with fuzzy logic controllers' was conducted and is also presented.