Research On Magnetic Field And Temperature Field At The End Of Synchronous Condenser Used In UHVDC Power Transmission

The synchronous condenser(SC)used in ultra-high voltage direct current(UHVDC)power transmission has the advantages of large capacity,strong voltage support ability and simple maintenance,which can quickly provide large capacity of dynamic reactive power to the system and improve the operation stability of the power grid.However,compared with conventional motors,the end structure of the SC used in UHVDC power transmission is more complex and the specifications of operation security requirements are higher,which lead to the increase of the leakage magnetic flux and the heating of the structures at the end of the SC.If the SC temperature is too high,it will lead to material characteristics degradation and insulation damage,affecting its operating performance and service life.As one of the core structures at the end of the SC,the magnetic shield can provide a low magnetic resistance circuit for the leakage magnetic flux,thus reducing the magnetic flux density and loss of the other end structures.In addition,the SC used in UHVDC power transmission pays more attention to its transient reactive power response ability,and the stator end leakage reactance is the basis for solving electromagnetic transient parameters and analyzing the transient reactive power support ability.Therefore,this paper has carried out researches on the end magnetic field,end leakage reactance,loss and temperature field of the SC used in UHVDC power transmission.The research results have certain reference significance for improving the distribution of magnetic field and temperature at the end of the SC and developing a larger capacity SC.The main work of this paper is shown as follows:(1)Taking a 300Mvar SC used in UHVDC power transmission as the research object,three-dimensional transient nonlinear magnetic finite element model at the end of the SC considering magnetic saturation is established,and the calculation method of solving the end magnetic field and eddy current loss are introduced.(2)The model of the three-dimensional electromagnetic field at the end of the SC is solved,and the distribution of the end leakage magnetic field of the SC is obtained,and the influence of leading phase depths of SC on the end leakage magnetic field distribution is studied.(3)The variation law of the end leakage flux and eddy current loss of the end structures with the thickness of the magnetic shield is revealed,and the positions of the maximum magnetic flux density and loss density of the end structure are obtained.(4)Three calculation methods of the stator end leakage reactance are derived:energy method,flux linkage method and empirical formula method,and the law of the stator end leakage reactance with the variation of magnetic shield thickness is analyzed.In addition,the stator end leakage reactance is calculated by using the frozen permeability method under different working conditions.(5)The finite element model of three-dimensional steady-state temperature field at the end of SC is established and the ventilation and cooling system at the end of SC is introduced.In addition,the temperature distribution law of each end structure under different working conditions is analyzed,and the hottest point of the end structure temperature is determined,and the correctness of the calculation model in this paper is verified.