An amplitude- and rate-saturated collective pitch controller for wind turbine systems

This paper proposes a new collective pitch controller for wind turbine systems to maintain the generator speed constant at the rated value in the region above the rated wind speed. It provides the command of the collective pitch angle to the wind turbine system, and one can impose explicit limits on the magnitude and the rate-of-change of the pitch angle command. In addition, the controller involves a variable gain that realizes non-overshooting convergence from the large errors in the generator speed and accurate regulation of the generator speed near the rated value. This controller is an extension of an amplitude- and rate-saturated controller previously proposed by the authors. It is combined with a state and disturbance observer and a lookup table-based feedforward. The proposed controller is validated through a software simulator FAST emulating a three-bladed horizontal-axis wind turbine system.