Effectiveness analysis of twelve sectors of DTC based on a newly modified switching table implemented on a wind turbine DFIG system under variable wind velocity

Abstract

This paper aims to present a novel Direct Torque Control (DTC) strategy based on twelve sectors and a new Modified Switching Table (12-MST-DTC) used to control the Doubly Fed Induction Generator (DFIG) powered by Wind Turbine (WT) and operating under random wind speed. Robustness and fast dynamic performances have made Conventional DTC (C-DTC) popular and widely used, but presents major drawbacks which are high torque and flux ripples. Therefore, the 12-DTC has been proposed in the literature as an improvement but suffers from significant oscillations during super-synchronous operation mode as well as the case of overspeed. The proposed control strategy maintains the performances that offer (C-DTC and 12-DTC) and furthermore minimizes those drawbacks. The newly modified switching table is designed with additional input to cover all WT-DFIG system operation modes (sub-, super- and synchronous modes in addition to the case of over-speed) in order to diminish the flux, torque ripples and THD of the AC-grid injected currents. For optimal operating of variable-speed WT, MPPT algorithm and blade pitch control are invested. Simulation results of the 12-MST-DTC are compared with those of C-DTC and 12-DTC using MATLAB/Simulink environment treating all operation modes of WT-DFIG system and even in case of wind over speeds. The comparison results demonstrate the efficiency of the proposed control strategy in terms of flux/torque ripples and THD reduction, therefore fewer DFIG mechanical vibration and acoustic noise.