Fault-tolerant Control of a Wind Turbine with Generator Stator Inter-turn Faults

Abstract

Faults of wind turbine generator electromechanical parts are common and very expensive. This paper introduces a generator fault-tolerant control scheme for variable-speed variable-pitch wind turbines that can be applied regardless to the AC generator used. The focus is on generator stator isolation inter-turn fault that can be diagnosed and characterised before triggering the safety device. An extension of the conventional wind turbine control structure is proposed that prevents the fault propagation while power delivery under fault is deteriorated as less as possible compared to healthy machine conditions. Fault-induced and inherent asymmetries of the generator are estimated and respected by the field-oriented control of the generator to eliminate torque oscillations. An approach for asymmetry detection based on an unscented Kalman filter is proposed. Presented fault-tolerant control strategy is developed taking into account its modular implementation and installation in available control systems of existing wind turbines to extend their exploitable life span and increase energy production. Simulation results for the case of a megawatt class wind turbine are presented.