UHVDC Converter Valve Integrated Wide-band Equivalent Circuit Models And Application Research

UHVDC converter valve in the operation process may withstand overvoltage which come from the AC and DC systems.With the voltage level and transmission capacity rising,converter valve became larger.As a result,voltage distribution characteristics that interlayer voltage distribution is not uniform become more prominent because of the cumulative effect of uneven voltage distribution between the various parts of valve tower.Therefore,the analysis of the interlayer transient voltage distribution characteristics of the converter valve has important engineering significance in putting forward safe and reasonable voltage equalization methods and improving the stability of the DC system.In this paper,±1100kV UHVDC converter valve is taken as the research object.Wide-band modeling,parameter extraction,simulation verification,interlayer voltage analysis and voltage equalization methods and some other work is done in view of the UHVDC converter valve under steep front impulse voltage insulation type test.First,electrical design of the ±1100kV converter valve and multi-valve insulation test are introduced.Based on the structure of converter valve and characteristics of interlayer transient voltage analysis,UHVDC converter valve unit integrated wideband equivalent circuit model and two-port wideband equivalent circuit model are proposed.Then,in terms of parameter extraction,for lumped parameters,the parameters are extracted by the impedance frequency characteristic fitting method;for parasitic capacitance parameters,unit parasitic capacitance parameters extraction method is proposed,and this method is applied to the parasitic capacitance extraction of the converter valve integrated wideband equivalent circuit model.The port parasitic capacitance of the two-port wideband equivalent circuit model is obtained by iterative calculation on the basis of valve layer unit parasitic capacitance,and the model is validated by simulation.The correctness of the two models are verified by simulation.Based on the two-port wideband equivalent circuit model,the voltage transfer characteristic curve is analyzed in detail,and the influence of each parameter in the model on its transmission characteristics is analyzed.Finally,based on the two-port wideband equivalent circuit model,the influence of each parameter in the model on the transient voltage distribution of the valve tower is simulated and analyzed.The method of voltage equalization is put forward,and the validity of the proposed method is verified by simulation.