Modeling and loading compensation of a rotary valve-controlled pitch system for wind turbines

A rotary valve-controlled pitch system is proposed to regulate the generator power and smooth power fluctuations for a wind turbine. Design details and dynamic modeling of this pitch system are presented and analyzed. A practical loading compensation approach is synthesized and involved in the pitch system to compensate for the external uncertain pitch loads. The proposed pitch system and loading compensation approach have been experimentally evaluated in terms of generator power smoothing and control accuracy. As demonstrated by the comparative experimental results, the proposed pitch system can be used to significantly smooth the generator power fluctuations and hence to improve the power quality as compared with a servo valve-controlled pitch system under the same operating conditions. The loading compensation approach can also be used to significantly attenuate the effects of external pitch loads and improve the robustness and reliability of the pitch system. The proposed pitch system features good control accuracy and cost-efficiency and hence is attractive for applications in modern largescale wind turbines.