With the construction of new power systems, the proportion of renewable energy sources such as photovoltaics and wind power connected to 220 kV and below substations through power electronic converters in the power system is gradually increasing. There are more and more devices with nonlinear characteristics on the load side, presenting different harmonic spectra and sustained effects. Long duration harmonic currents cause an increase in capacitor heating. This paper first establishes a thermal physical model of AC parallel filtering capacitors based on the skin effect, analyzes the current distribution of three bus connection methods: conventional connection, 2-split connection, and 3-split connection under 50 Hz and 1000 Hz current conditions, and analyzes the current path of capacitors under different bus connection methods. Secondly, the influence of the number of bus splits on its current density distribution was analyzed, and it was found that the number of bus splits will have an impact on the current density distribution at the end of the bus. Finally, the variation trends of the equivalent resistance and equivalent inductance of the three busbar connection methods under different harmonic frequencies were analyzed. This study has laid a theoretical foundation for the optimization of capacitor unit structure design.