Study on a novel hydraulic variable-pitch system of wind turbine

The structure and the principle of a novel hydraulic variable-pitch system of wind turbine are analyzed in this paper. Since the hydraulic circuits during opening pitch and closing pitch are different, the linear mathematic models for hydraulic variable-pitch mechanism among the two different operating processes are built up respectively. Due to the different processes, the simulation model of the hydraulic variable-pitch system is designed by using Matlab/Simulink circumstance and the system dynamic responses to referenced sine curves are obtained to evaluate the validity of the proposed mathematic models. Simulation results show that the proposed system models are reasonable and effectual for designing an electro-hydraulic variable-pitch system. Furthermore the conclusion is obtained that different control strategies should be used from opening pitch to closing pitch. As a result, the mathematic models are useful to design and develop a practical hydraulic variable-pitch system.