Impedance and Stability Analysis of Voltage-Source Converter Interconnection Based on a Universal Admittance Model

A universal admittance model of voltage-source converter applicable to various DQ-frame-based control architectures is developed from the sequence-domain complex space vector analysis. The lumped sequence admittances of converter interconnection considering multicoupling effects are derived based on the converter admittance model, in which two coefficients are defined to quantify the cross-coupling effect between the ac and dc networks. From the universal model, the converter admittances with three typical control architectures and the lumped admittances of converter interconnection are calculated, compared, and verified with time-domain point-by-point simulations. Experiments are also conducted for further verification. Stabilities of the converter interconnection with the three typical control architectures are analyzed and compared. The obtained results indicate that introducing the outer dc voltage control can not only reinforce the coupling between ac and dc circuits but also degrade the stability performance of ac and dc circuits both.