Power Smoothing Control Strategy of Direct-driven Permanent Magnet Synchronous Generator for Wind Turbine With Pitch Angle Control and Torque Dynamic Control

The uncertainty of wind energy and the inherent features of the wind turbine make the output active power of the wind-power generator fluctuate with the change of the wind speed, which affects the output power quality of the wind turbine and even the stability of the power grid. Based on analyzing of the operational characteristics about the direct-driven permanent magnet synchronous generator (DD-PMSG), an active power smoothing control strategy had been proposed through the pitch angle control and variable speed control of the generator in all operating regions. Considering the stochastic behavior of the wind energy and the highly nonlinear feature of the DD-PMSG, the pitch angle controller had been investigated based on the fuzzy theory and the generator torque dynamic sliding-mode controller. The operational characteristics of a DD-PMSG with the fuzzy pitch angle control and the torque dynamic sliding-mode control were studied through the computer simulation. The simulation results show that the speed operation range of the wind turbine can be effectively controlled by the fuzzy pitch angle control strategy and the output active power of the generator can be smoothed by the dynamic sliding-mode control strategy. Compared with the traditional maximum power point tracking (MPPT) control strategy, the proposed control strategy can effectively reduce the output active power fluctuations of the DD-PMSG and limit the operation range of the generator speed.