Influence of Reactive Power Flow on the DC-Link Voltage Control in Voltage-Source Converters

This paper analyzes the influence of reactive power flow on the dc-link voltage control in voltage-source converters. The dc-link voltage and reactive power is coupled through the ac side filter based on the power balance. An analytical impedance model is further developed for characterizing the dynamics of the dc-link voltage control, which allows identifying the stability impacts under different reactive power. The impedance-based analysis reveals that the directions of reactive power flow, i.e. the inductive or capacitive reactive power, have reverse impacts on the stability of the dc-link voltage control under a weak grid condition. Case studies on the inductive and capacitive reactive power are carried out, and subsequently validated by using time-domain simulations and experimental tests. The results verify the effectiveness of the impedance model and the stability analysis.