Analysis of Harmonic Interaction in Multi-infeed HVDC System Based on Impedance Method

In this paper, the harmonic impedance model of multi-infeed HVDC transmission system is established. The interaction mechanism of harmonic in inverter side is revealed based on impedance analysis method. Transfer harmonic coupling impedance and transfer harmonic self-impedance are proposed to measure harmonic interaction. The impact of the coupling impedance and the equivalent impedance of ac subsystems on indexes are analyzed respectively. The results show that, the harmonic interaction increase with the decrease of the coupling impedance or growth of difference between the equivalent impedance of ac subsystems; the amplitude difference is the main factor among them. In most cases, transfer harmonic coupling impedance has a better applicability, the other one can only reflect the influence of the equivalent harmonic impedance of other ac subsystems on interaction to a certain DC. The analysis results of three-infeed HVDC transmission test system have verified the correctness of the conclusions.