PI controller design for pitch control of large wind turbine generator

In large horizontal axis wind turbines blade pitch control is important in order to keep the structural loads within design limits at high wind speed. The system dynamics is highly oscillatory along with the time delay in the hydraulic pressure driven pitch control system and in certain turbine configurations and operating conditions, it may have inverse response dynamics which make the system further difficult to control. In this paper a proportional-integral (PI) controller for pitch angle control is proposed which is based on direct synthesis (DS) approach for achieving a desired response. The PI controller is derived from the DS controller by an approximate frequency response matching. The method is illustrated through examples taken from the literature and compared with a method prevalent in the literature.