| The distributed generation system which is based on a high speed permanent magnet generator(HSPMG)driven by a micro gas turbine has not only high efficiency,little pollution,simple structure,low construction and maintenance costs of the micro gas turbine system,but also small size,high power density and transmission efficiency of HSPMG.Therefore,more and more scholars pay attention to it.For this distributed generation system,since the output power frequency of HSPMG is generally hundreds of Hertz or even more than 1000 Hz,the output power can not be used by normal user directly,and the converter device is necessary for the system.As the nonlinear switch-type load,the converter can affect the generator seriously.In this paper,taking an HSPMG as an example,some problems in the operation of HSPMG connected with converter are studied in depth.Firstly,taking an 117kW,60000 rpm HSPMG as an example,the two-dimensional finite element electromagnetic field analysis model,mathematical model and three-dimensional fluid-temperature coupling analysis model of the generator are established.The test platform of generator is built,and the electromagnetic performance and temperature rise of the generator under three-phase balanced light load and no-load conditions at different speeds are tested respectively.By comparing the experimental data with the calculation results,the accuracy of the used models is verified.Secondly,in order to more accurately analyze the influence of characteristic high frequency time harmonics produced by converter on the generator performance,the variations of generator electromagnetic performance and temperature distribution are studied when the winding contains different amplitude and frequency of time harmonics respectively.The influence laws of different characteristic high frequency harmonics on generator electromagnetic and temperature performance parameters are obtained,and its influence mechanism of these harmonics is revealed.Based on the analytic algorithm,the coupling mechanism between the characteristic high frequency time harmonics and the space harmonic magnetic field of the generator is revealed.It can provide theoretical support for optimizing the control strategy of converter.Thirdly,in order to rapidly analyze the influence of the control strategy of the converter on the performance of the generator,based on the analytical method and the dynamic coupling circuit method,the dynamic state space model of the integrated system of the generator and converter is established.The losses,output performance and temperature field of the generator under different fixed switching frequency control strategies are studied.The influence mechanism of the multi-frequency coupling harmonic current produced by the converter on the generator when the switching frequency of converter changes,and determines the optimal fixed switching frequency control strategy,which provides references for the optimal design of the distributed generation system.Finally,in order to study the effects of unbalanced load on losses and temperature rise of high speed permanent magnet generator,based on the two-dimensional finite element electromagnetic field analysis model,the losses of the generator are analyzed in depth,and the key factors affecting the total loss of the generator under unbalanced load are obtained.The influence of unbalanced load on the key part temperature of the generator is studied,and the resistant limit of unbalanced load of the generator is determined,which provides references for the optimization design of the high speed permanent magnet generator. |
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