A novel continuously variable-speed offshore wind turbine with magnetorheological transmission for optimal power extraction

Abstract

ABSTRACT The paper introduces a novel magnetorheological transmission (MT) type offshore wind turbine (OWT), which integrates the MT into the traditional-geared train to construct a controllable power split type continuously variable gear train for the OWT. The design and construction of the MT-OWT are proposed. The continuous regulation of the transmission speed of the drive train is achieved by controlling the current of the MT. Then, a generalized utilization coefficient of wind power is defined to describe the overall efficiency of the OWT. A cooperative control strategy is proposed to track the optimal power points and capture the optimal wind kinetic energy with the best energy transmission efficiency by adjusting the electromagnetic torque and the MT of the OWT. The feasibility of the MT-OWT is verified through simulations. The results indicate that the maximum loads in the proposed MT-OWT can be reduced to be around 70% of the GT-OWT when adequate control is applied. Also, the generalized utilization coefficient of wind power can be well maintained around the rated value of around 0.45 and the generator speed can be well maintained around the rated value of around 1000 rpm (105 rad/s) regardless of the variations of the wind speeds and the turbine rotor speeds when using the proposed MT-OWT as compared with conventional OWT.