| CPC H02J 3/36 (2013.01) [H02J 3/001 (2020.01); H02M 7/48 (2013.01); H02J 2203/00 (2020.01)] | 10 Claims |

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1. A method for suppressing a first high-voltage direct-current (HVDC) commutation failure under an alternative current (AC) system fault, applied to an HVDC transmission system, the method comprising:
obtaining a three-phase voltage of a converter bus in the HVDC transmission system, and calculating a zero-sequence component amplitude and an αβ component amplitude of the three-phase voltage of the converter bus;
obtaining a setting value of an extinction angle of the HVDC transmission system, a per unit value of a short-circuit reactance of a converter, a per unit value of a DC current, a commutation time and an impedance ratio, and calculating a first trigger-angle command for a single-phase fault and a second trigger-angle command for a three-phase fault according to the zero-sequence component amplitude and the αβ component amplitude;
selecting a smaller one of the first trigger angle command and the second trigger angle command as a trigger-angle command for an extinction-angle controller controlling a converter valve in the converter; and
adjusting a trigger angle of the HVDC transmission system by using trigger-angle command for the extinction-angle controller as an upper limit value for an output of the extinction-angle controller of the HVDC transmission system.
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