Patent ID: 11789047

Abstract:
A method for calculating the steady-state fault current of a modular multilevel converter (MMC) comprises calculating the dc-side critical resistance values RA/B, RB/C and RC/D of the MMC based on the bridge arm inductance coefficient k and the ac-side reactance Xac of the MMC; Then, determining the operating modes of the MMC based on RA/B, RB/C and RC/D, and calculating the steady-state dc fault current and the conduction overlap angle respectively under various operating modes without considering the ac-side resistance based on the parameters k, Us, Rdc and the dc-side critical resistance values RA/B, RB/C and RC/D; After that the steady-state AC fault current amplitude and phase angle for each operating mode without considering the AC side resistance are calculated based on the DC current and conduction overlap angle for each operating mode, respectively. Finally, the steady-state AC fault current amplitude and phase angle are calculated for various operating modes considering the AC side resistance.