Modeling of the HVDC convertor using dynamic phasor under asymmetric faults in the AC system

This paper presents a modeling technique to the HVDC converter under asymmetric conditions using the dynamic phasor. A detailed analysis of the dynamic processes of HVDC converter when asymmetric faults occur in the ac system, including variation of switching instants and unbalanced commutation overlaps is presented. Based on which, an advanced dynamic phasors model for HVDC converters is proposed, which is more suitable for the fault characteristic simulation in large scale HVDC transmission system under asymmetric ac faults. It is verified to be accurate and effective by comparison with results obtained from digital simulation of the detailed electromagnetic transient model of Guiguang II HVDC system in China.