A novel pitch angle control system is proposed to smooth output power and drive-train torque fluctuations for wind turbine. This system is characterized by an outer open control loop for enhancing the direct pitching motion and an intrinsic hydro-mechanical position control loop offering the benefit of sensor-less pitch control. A pragmatic design procedure is provided and several key design parameters are determined or optimized. Modeling, stability analysis and dynamic characteristics of this pitch control system are also presented. Comparative experimental results have validated the effectiveness and efficiency of this system in power and torque regulations. (C) 2015 Elsevier Ltd. All rights reserved.