Fault-tolerant control of a blade-pitch wind turbine with inverter-fed generator

A fact is that wind energy is both green and expensive energy. In order to increase its economic competence, wind turbine faults should be reduced and prevented. In wind turbines faults most commonly occur in the gearbox and in the generator system components like power converter or generator electromechanical parts. This paper proposes a fault-tolerant control strategy for variable-speed variable-pitch wind turbines in case of identified and characterized generator electromechanical faults like broken rotor bar or winding inter-turn fault. In particular we propose an upgrade of the torque control loop with flux-angle-based torque modulation. Usage of pitch controller in the low wind speed region is also proposed to intentionally reduce power capture in order to avoid or to postpone the system fault development. Presented fault-tolerant control techniques are developed considering their easy implementation and installation in available control systems of existing wind turbines to extend their life cycle and energy production. Simulation results for the case of 700 kW direct-drive wind turbine and the identified stator winding fault are presented.