Abstract: PSASP and BPA are the commonly used short-circuit calculation programs in China. Even under the same calculation modes and calculation conditions, their computed results could be different. This article analyzed the reasons for this difference by using theoretical analysis and simulation calculations. It focused on the effective value, short-circuit capacity, short-circuits ratio, and effectively short-circuit ratio of the proper computing methods for the short-circuit current in the AC/DC power system. This paper gives two suggestions: when calculating the short-circuit current based on the power flow, the equivalent impedance corresponding to the DC power could be included in the node impedance matrix used in the short-circuit calculation. When calculating the short-circuit ratio and effectively short-circuit ratio indicators.It might be better to use the short-circuit capacity calculation result which was figured out by using the Thevenin equivalent method based on the network-based mode when the converter bus voltage is 1.0 p.u. . The result of this study could help to improve the application of short-circuit calculation theory in power systems.

    Key words: AC/DC power system; power-flow based short-circuit calculation; network-based short-circuit calculation; Thevenin equivalent method; superposition method