Two-port Equivalent Circuit Model for UHVDC Converter Valves

UHVDC converter valves during operation mayexperience overvoltage, which come from the AC or DC systemsto which they are connected. Therefore, building an equivalentcircuit model (ECM) for the converter valve to analyze theinterlayer transient voltage distribution characteristics has importantengineering significance for safe and reasonable voltageequalization methods and improving the stability of the DCsystem. This paper proposes a two-port equivalent circuit modelfor ?1100 kV converter valve based on the structure of thevalve and parameter extraction methods presented. In terms oflumped parameters, integrated ECMs for valve layers are builtthrough impedance-frequency characteristic analysis; in termsof parasitic capacitance parameters, port equivalent parasiticcapacitance parameters are obtained by terminal capacitancemethod and iterative equivalence methods proposed in thispaper. By combining integrated ECMs of valve layers and portequivalent parasitic capacitances, the two-port ECM is obtained.Simulations are carried out to test the effectiveness of the twoportECM. Using the ECM, the voltage transmission characteristicsand their influencing factors are analyzed, dependingon which corresponding voltage equalization method is proposedin this paper, and the effect of this method is verified throughsimulation.