Instantaneous torque ripple control and maximum power extraction in a permanent magnet reluctance generator driven wind energy conversion system

A usual wind energy conversion system (WECS) suffers from significant amount of torque ripples even if the wind velocity remains constant. These torque ripples propagate mechanical stress in the turbine-generator drive train and may eventually lead to the failure of its various components. This research paper presents a unified control strategy which yields maximum power from WECS while minimizing the torque ripple through the instantaneous torque control. The permanent magnet reluctance generator (PMRG) employed in this research has a substantial advantage over a switched reluctance generator (SRG) that it does not require an external source for excitation. However similar to SRG, PMRG also exhibits large torque ripples. The torque ripple minimization in this research work has been achieved by controlling the torque distribution in the commuting phases of the generator. The generator torque is estimated through the pre-calculated phase reluctances obtained from the finite element analysis. The reference torque is generated by a maximum power point tracking (MPPT) algorithm in order to operate at the maximum efficiency. The effectiveness and superiority of the proposed unified control system has been established by comparing the results with the conventional controller that provides only MPPT.