Analysis of control interactions in multi-infeed VSC HVDC connections

The number of voltage-source converters connected to the power system is increasing. This has led to concerns about the impact of control interactions between converters and their influence on the system stability. Recent grid codes consider such interactions as low-frequency disturbances between the converters and neglect network dynamics. This paper studies the control interactions and interferences in a multi-infeed power system with two converters. The phenomenon is studied in the frequency domain by using the admittance-based stability assessment. Harmonic stability under different network characteristics is addressed. The analysis shows that resonances in the system can lead to instabilities when appearing within the control bandwidth, thereby implying the necessity to also consider higher-frequency dynamics.