Hybrid Power Transmission Technology in a Wind Turbine Generation System

The direct-drive hydraulic pump suffers the disadvantages of large displacement and difficulty of manufacture. This paper thus proposes a hybrid power transmission technology that utilizes a single-stage gear transmission and low-speed hydraulic pump. The transmission technology reduces the displacement of the hydraulic pump and retains the torque-stable feature of a hydrostatic transmission. This paper designs the basic structure of a hybrid power transmission system and constructs the system model using the AMESim and MATLAB software. Under the grid-connected circumstance, the variable-speed constant-frequency control algorithm when the wind speed is below the rated value and the pitch control algorithm when the wind speed is above the rated value are simulated and analyzed. A 20-kW prototype has been developed. The simulation and the experimental data demonstrate that a hybrid power transmission meets the demands in various working conditions and stabilizes the torque of a wind turbine generation system.