Electromagnetic Design And Temperature Field Analysis Of Megawatt High-speed Permanent Magnet Wind Power Generator

In the wind power generation system, generators as the main part of energyconversion, has been studied widely. At present, the mainstream type ofgenerators for wind field are doubly-fed wind power generator and direct-drivepermanent magnet wind power generator. The technology of doubly-fed windpower generator is relatively mature, but it has the problem of the complexstructure, poor reliability, and the poor low voltage ride-through capability.The direct-drive permanent magnet wind power generator can solve theseproblems, but it has the problem of big volume that result in high cost inpermanent magnet and money. To cure the above problems, high-speedpermanent magnet wind power generator with its high speed, small volume,high efficiency advantages has been used in the wind field, and also been aresearch hotspot for wind turbine manufacturer.Megawatt high-speed permanent magnet wind power generator comparedwith direct-drive permanent magnet wind power generator and wind powergenerator with a single stage gearbox, the peed increases extremely. The speedincreases from10~20r/min for low-speed direct-drive permanent magnetwind power generator or250~500r/min for wind power generator with asingle stage gearbox to1000~2000r/min for high-speed permanent magnetwind power generator. This high speed will inevitably affect the fixed of rotorpermanent magnet. To solve the problem, this paper studied a kind ofimproved rotor structure, and through the finite element analysis software, tooptimize the design of the structure. The main research contents are as follow.Firstly, this paper analyzed the differences of traditional surface mounttype and tangential rotor structure. On this basis, combined with the characteristics of high speed motor, an improved pole shoe rotor structure isstudied. Based on magnetic circuit method, the high-speed generator wasdesigned. And then the initial model was analyzed by the software of Ansoft.Secondly, according to the problem of the poor sine air gap flux density,big cogging torque and so on, puts forward a kind of optimization method ofoptimizing the pole shoe shape to optimize the performance of the generator.And through this method, optimized the generator with the target ofminimizing the cogging torque and gave the comparison of the optimizedresults. To ensure that the permanent magnet cannot be demagnetized,combined with superconducting closed loop flux conservation principle,analyses the maximum transient short-circuit current of three-phase short-circuit. On this basis, the demagnetization of the permanent magnet wasanalyzed.Thirdly, the generator adopts a pole shoe rotor structure, the eddy currentloss of the surface of rotor pole shoe is larger. In order to facilitate the heatthat produced by the eddy current loss, the rotor axial ventilation slot hadbeen opened radial vent hole in the design of the generator. According to thefluid flow and heat transfer mechanism, combined with the finite elementsoftware, the flow velocity distribution of the generator was analyzed and theaffection of radial vent holes in cooler was confirmed. On this basis, thetemperature of the rotor was calculated by the method of fluid-temperatureinteraction. The calculation results show that pole shoe rotor temperature in areasonable range, will not affect the performance of a permanent magnet. Theresults provided a valuable reference for the generator prototype production.Finally, a prototype of the generator was produced. Through the testingdata verified that the design satisfied the customer requirement. The testingdata also showed that the design calculation was accuracy. In the end, the testmethods were introduced and the results were analyzed.