Torque ripple minimization and maximum power point tracking of a permanent magnet reluctance generator for wind energy conversion system

A permanent magnet reluctance generator (PMRG), which is the member of switched reluctance machine (SRM) family, has an extremely simple and robust structure: no winding on both rotor and stator. Required flux for energy conversion is provided by magnets buried in stator yokes. Thus, it seems to be suitable for wind energy conversion systems (WECSs) for reducing power generation cost to the level of fossil energy conversion systems. In a PMRG based conventional WECS, the PMRG is often accompanied by a simple diode bridge and a maximum power point tracking (MPPT) controlled converter. This type of converter topology does not allow utilizing any torque ripple minimization strategy. Thus, the system inevitably suffers from large torque ripples due to the doubly salient structure of both stator and rotor of the PMRG. Torque ripples propagate acoustic noise, vibrations, and mechanical stress in the turbine-shaft. Exposing to such ripples may result serious failure or damage in the WECS. In this paper, a novel algorithm consisting of MPPT and torque ripple control has been tested on the PMRG based WECS. The control strategy is applied to the system through an asymmetric half bridge (AHB) converter which is accepted to be a traditional converter for SRMs. The performance of control method has been verified under the conditions of constant and variable wind speed. Both simulation and experiment results prove that the control algorithm with the AHB converter allows significant torque ripple reduction in PMRG based WECS while generating power at its maximum point.