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This paper addresses the stability issues caused by the dc-link voltage control of grid-connected voltage-source converters. An analytical impedance model is developed first for capturing the interactions between the dc-link voltage control and ac current control of converters, which enables to identify different stability impacts of the dc-link voltage control in the rectifier and inverter operation modes of converters. The impedance model is further transformed from the dq-frame to the αβ-frame, which allows characterizing the frequency-coupling effects of the dc-link voltage control dynamics. The impedance-based analysis reveals that the dc-link voltage control may cause low-frequency oscillations in the rectifier mode and high-frequency oscillations in the inverter mode. Case studies on the rectifier and inverter operation modes are presented, and subsequently validated by using time-domain simulations and experimental tests. The close correlations between the measured results and theoretical analysis demonstrate the effectiveness of the impedance model and stability analysis.
Lu et al. (Mon,) studied this question.