Research On Wind Turbine "Variable Speed Constant Frequency" Technology Based On Energy Hydraulic Transmission

With gradual depletion of the traditional fossil fuels and increasing deterioration of the environment, clean energy like wind energy has been paid more and more attention by all over the world. Wind turbine develops from initial constant speed fixed pitch to variable speed variable pitch. In order to capture maximum wind energy and combine to the grid, "variable speed constant frequency" (VSCF) technology is particularly important. This paper researches on wind turbine VSCF technology based on energy hydraulic transmission. Different from the traditional method that uses power electronics technology to realize VSCF, the core idea of VSCF technology based on energy hydraulic transmission is that when the wind speed changes below the rated value, by adjusting the displacement of pump to produce corresponding anti-torque on the rotor, the rotor speed can be maintained at the optimal tip speed ratio and the rotor maximum power capture can be ensured. And regardless of how the rotor speed changes, the generator speed can be stabilized at rating by adjusting the displacement of motor, so as to ensure power frequency constant.The paper is divided into six chapters to research on wind turbine VSCF technology based on energy hydraulic transmission. The main contents of each chapter are as follows:The first chapter introduces the subject research background, expounds the history, status and trend of domestic and foreign wind power development, put forward the subject research significance and the research content.The second chapter does some research on the basic theory about wind turbine VSCF technology based on energy hydraulic transmission. Some wind turbine foundation theories such as Betz theory and blade element theory are introduced. The starting point of VSCF technology is elaborated. And a wind turbine generator system based on energy hydraulic transmission is designed. The feasibility of VSCF in this system is proved theoretically.The third chapter researches the method of maximum power point tracking in energy hydraulic transmission wind turbine generator system, respectively, to direct speed control method, maximum power-speed curve tracking method, optimal torque-speed curve tracking method, climbing search method and best speed method based on the estimation of wind speed. The advantages and disadvantages of each method are compared in this chapter.The fourth chapter researches on modeling and simulation of energy hydraulic transmission system of VSCF wind turbine. The mathematical models of wind speed, transmission system and electrical part are established. The simulation parameter values of each component are calculated. The simulation of wind speed is completed in the Matlab/Simulink software, energy hydraulic transmission system completed in the AMESim software. The simulation results show that VSCF technology based on energy hydraulic transmission can be realized.The fifth chapter does some experimental research on VSCF wind turbine based on energy hydraulic transmission. An energy hydraulic transmission wind turbine VSCF test-bed is designed and built. And the VSCF test is made in this test-bed. The test results verify the feasibility of VSCF technology based on energy hydraulic transmission.The sixth chapter makes a summary of research work and achievements, and points out the subsequent research direction and working content.