On Optimizing the Aerodynamic Load Acting on the Turbine Shaft of PMSG-Based Direct-Drive Wind Energy Conversion System

The blade's rotational sampling to the spatial distributed wind velocities will induce 3P oscillating aerodynamic torque during the wind energy generation process. This causes the turbine drive train bare high aerodynamic load because the generator is driven by this aerodynamic torque through it. Moreover, the system's inherent resonant mode will be also induced by the aerodynamic load, causing fatal damage to the whole system. To damp the serious aerodynamic load of the permanent-magnet-synchronous-generator-based direct-drive wind energy conversion system (WECS), a new power control strategy with damping injection is proposed in this paper. The proposed method is realized by adding a compensation torque, which is proportional to the small-signal value of the generator speed, into the system torque control loop. Both the aerodynamic load and the system's inherent resonant mode could be well damped if the proposed method were adopted. Theoretic analysis is verified by experimental results performed by a 10-kW WECS established in the laboratory.