Investigation of Frequency Domain Analysis Methods for Converter-Driven Stability Evaluation of Converter-Dominated Meshed Systems

This paper investigates the frequency domain analysis methods to analyse converter-driven stability in meshed networks. For the analysis in frequency domain, the complete network is modelled in frequency domain as an impedance matrix. Where the converter impedances are obtained numerically using perturbation injection approach and the passive components are modelled analytically forming a discreet frequency dependent network impedance matrix. Network impedance matrix is manipulated and bode plots are employed to obtain the stability conclusions from the frequency domain stability analysis methods. Stability analysis in EMT tool is used as benchmark to validate the results obtained in frequency domain methods. Two exemplary cases are presented where the frequency domain methods are applied. A comparison of the robustness of these methods is carried out. Comparison shows that extended impedance based analysis method (EIbSC) is the most intuitive to analyse the root cause of an instability. Given that the assumption of no right hand plane poles, then positive mode damping method (PMD) is appropriate. However, both EIbSC and PMD methods showed inconsistencies in their stability prediction. Generalized nyquist criterion (GNC) proved to be the most robust method to analyse converter-driven stability in meshed systems.