Capacitance parameter extraction of HVDC converter system by the Method of Moments

Capacitance parameter extraction of converter system is crucial to analyze the voltage distribution of valve tower under different overvoltages (such as lightening, partial discharge, etc) in HVDC converter station. According to the actual dimension of valves, the Method of Moments(MOM) based on the point matching method is applied to extract the capacitances, including the self-capacitances and the mutual capacitances between the valve modules in the valve hall. Firstly the surfaces of conductors are meshed into small area elements, and the surface charge density of each element is considered as a constant. Then the potential coefficient matrix corresponding to elements can be achieved by MOM. The capacitance matrix can be acquired through matrix transformation. The proposed method is flexible and fast compared to the Finite Element Method (FEM) and Boundary Element Method (BEM), since it is unnecessary to solve the conductor surface charge and the electric field. The calculation results agree very well with the capacitance testing experiments.