| Energy and environment are pressing problems that must be settled by human beings for future survival and development.Wind power has preferable economic and social benefits because of its cleanliness and free pollution,short construction period, flexible investment and few occupation of land.At present,there are big gaps between china and developed countries in wind turbine's theory and application research, because wind power has disadvantage with thermal power and hydropower in cost, power quality,equipment manufacture and control technology.Research of wind turbine in china is very weak and many advanced wind turbine technologies are not solved such as high power capacity,pitch control and advanced brake system etc.Thus, almost all advanced large-scale wind turbines are imported from overseas.In all,the wind power technology and its equipment research become a hot spot topic for technical circles and enterprise.Wind turbine is a comprehensive system engineering of high technology which deals with aerodynamics,automatic control,mechanical drive and generator etc. Nowadays,the research hot pots of wind power are focused on electrical parts,few on mechanical parts.Wind turbine a machine-electricity-liquid associated equipment,and mechanical part is an important part in it.Research of wind turbine focus on electrical parts as well as on mechanical parts,make the technology's development balance.This thesis has studied the brake system of wind-driven generator.A new conceptual hybrid electric brake system(HEBS)that combines a contact conventional hydraulic brake system(CBS)and a contactless Eddy current brake(ECB)system is proposed in the paper.The primary contents and original contributions of this thesis are as follows:(1)A new conceptual hybrid electric brake system(HEBS)that combines a contact conventional hydraulic brake system(CBS)and a contactless Eddy current brake(ECB)system is proposed to aim at problems of CBS.Three constructions are proposed based on installation of the CBS.①CBS installs on the low-speed shaft.②CBS installs on the high-speed shaft.③CBS installs both on the low-speed shaft and the high-speed shaft.After analyzing the force of the three constructions,drawn conclusion that③is the optimal.(2)The flexible shaft model of the brake system based on the spring-mass-damper system are used to analyze the dynamics of the brake system.The proposed model is adequate to describe dynamic behaviors and is easy to simulate by computer.(3)Calculated the 3D eddy current field of the rectangular electromagnet brake system with the Maxwell3D in the ANSOFT software.The distribution of the intensity of magnetic Induction is analyzed,and the impact of magnetic Induction on distribution of the magnetic field is studied.These will benefit to optimal design.(4)Aiming at the character of the new conceptual brake system,two controllers were proposed to control ECB and CBS respectively.To solve the upper bound of uncertainties and eliminate the chattering phenomenon,a fuzzy neural network control system which combines the sliding mode control is proposed.(5)A 600KW HAWT is simulated using the analysis method,the result of the comparison with the three different installing places is obtained and their differences are discussed.The third method needs less braking torque and smaller impact load in gear.So it is the optimal choice.ECB is also simulated using the analysis method. After comparing of brake tracking performance of the ECB without a fuzzy neural network sliding mode controller and with a fuzzy neural network sliding mode controller,drawn conclusion that the later is has fast step response,no overshoot.So the controller meets the requirement at all. |
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