Study On Hydrodynamic Speed Adjusting System And Its Control Of Wind Turbine

With the development of society and progress of science and technology, theenergy demand of human is continuously increasing. World electricity generation is20181TWh, of which fossil energy accounts for67.8%in2008.As a kind ofnon-renewable energy, the reserve of fossil energy is limited. According tointernational general prediction method, oil resources will run out in40years and gasresources will run out in60years. Excessive consumption of fossil energy results inenergy crisis as well as environmental disruption, and environmental pollutionproblems is increasingly outstanding. In order to resolve energy crisis and protect theecological environment, it is urgent to reduce the fossil energy consumption,vigorously develop new energy and renewable energy, to walk the road of greenenergy and the harmony of the ecological environment.Because of high development and utilization value, wind power has uniqueadvantage in the field of new energy, and attracts more attention of countries aroundthe world. Traditional VSCF wind turbine can’t access to power grid without rectifier-inverter device. However the development direction of wind turbine is large capacity,high efficiency, high reliability and low cost. The increased unit capacity of windturbine increases the manufacturing cost of traditional VSCF wind turbine, decreasesits reliability and shortens its life expectancy at the same time.Hydrodynamic torque converter with adjustable guide vanes is used in thetransmission system of high-power wind turbine. Variable speed input of thetransmission system can be achieved with constant speed output via the regulation ofadjustable guide vanes angle. It is possible that wind wheel can trace optimal speedand the utilization ratio of wind power is higher because of the variable input speed oftransmission system. Constant speed output of the transmission system ensures thespeed of the synchronous generator to maintain synchronous speed， with acharacteristics of stable frequency and no frequency devices, which improvesthe reliability of wind turbine，reduces the cost of power generation， the weight of the wind turbine and the volume of the cabin, and is easy to install.Because of the favorable damping and shock resistance capacity, hydrodynamictransmission components can decrease the peak load and prolong the life oftransmission components and parts. At the same time, it’s significant to broaden theapplication range of hydrodynamic transmission and promote the development ofhydrodynamic transmission that putting hydrodynamic transmission into wind powergeneration.The paper is supported by special foundation project of ministry of education,whose name is study on hydro-mechanical speed adjusting system with adjustableguide vanes of wind turbine (20100061120057).The main research work and relevantconclusions of the paper are as follows:（1）The working principle of wind turbine with hydrodynamic speed adjustingsystem is analyzed. The static mathematical model and the dynamic mathematicmodel of wind turbine transmission system are established respectively.Variable-speed input of hydrodynamic speed adjusting device can be achieved withconstant-speed output via the regulation of adjustable guide vanes angle, thusensuring the high wind energy utilization while maintaining a constant frequency ofsynchronous generators.（2）The influence law of the train parameters on the performance of windturbine transmission system is analyzed based on the static mathematical model ofwind turbine transmission system. Corresponding optimization model is establishedand the structure parameters of transmission system are optimized in order to improvethe efficiency of hydrodynamic speed adjusting transmission system of wind turbine.The comparison between the performance of optimized transmission system and theoriginal shows that the optimization result is better.（3）The operation region of wind turbine with hydrodynamic speed adjustingsystem is divided into constant wind power coefficient zone, constant speed zone andconstant power zone. The transmission of speed、torque and power of wind turbine inconstant wind power coefficient zone are analyzed especially.（4）Dynamic simulation model of transmission system is established byMatlab/simulink software based on the dynamic mathematical model. Thecorresponding control systems are designed according to the characteristic of wind turbine in different operational phases. Transmission system of wind turbine withhydrodynamic speed adjusting system is simulated dynamically under differentstep-wind by Matlab/simulink software.According to the simulation results inconstant wind power coefficient zone, the designed controller can respond to the windchanges rapidly and wind rotor can track the best wind power coefficient..Accordingto the simulation results in constant speed zone, the controller can respond to the windchanges rapidly and ensure that the rotor speed keeps constant.