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