Fu Chuang

HVDC converter modeling and harmonic calculation under asymmetric faults in the AC system

After a detailed analysis of the dynamic processes in the HVDC converter when asymmetric faults occur in the ac system, a sequence-component model of converter based on the advanced switching functions is present. Furthermore, a linear direct method of harmonic calculation is proposed. In this method, both the effect of the harmonic interaction between the ac and dc system and the dynamic processes in the converter are considered. It is demonstrated that quantitative analysis basis for harmonic suppression, filter configuration and setting calculation of relaying can be provided by this method which is verified by comparison with the results obtained by dynamic simulation.

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 convertors 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.

Study on the impedance-frequency characteristic of HVDC converter under asymmetric faults in the AC system

In a HVDC transmission system, faults occur in the ac system can result in the variation of impedance-frequency characteristic of the HVDC converter. In this paper, an advanced switching function model of HVDC converter, which considers the effect of the interactions between the ac and dc system and the unbalanced operating conditions of the converter, is presented. Based on this model, a method for calculation of the impedance-frequency characteristic of the HVDC converter under the asymmetric faults conditions is proposed. The method is verified by comparison with the results obtained from calculation and digital simulation using PSCAD/EMTDC.