Subsynchronous Resonance Analysis in Multi-Bus Multi-VSC Power System Based on Two-Port Network Modeling Method

This paper proposes a subsynchronous resonance (SSR) mode analysis method for the converter-based power system. In the system, the converters are modeled as multiple-input multiple-output admittance matrices, which essentially are two-port networks. Thus, the system including the grid impedances can be modeled as the connections of two-port networks, where the SSR mode can be identified by applying the impedance-based stability analysis method. To further distinguish the contributions of converter control dynamics to the SSR mode, the nodal admittance matrix is systematically obtained by applying the graph theory. Then, the modal impedances of the system can be derived and analyzed with the participation factors of each bus and the eigenvalue sensitivities to the specific entry in admittance matrix, which enable to quantify the contributions of network components to the SSR mode, and the theoretical analysis is validated by a case study.