Mechanism Analysis of Modal Resonance in Converter-Based Power Systems

The increasing integration of renewable energy and power electronics has brought various oscillation issues due to open-loop modal resonance, while the essential mechanism of open-loop modal resonance has not been fully discovered yet. In this connection, this paper firstly proposes the concept of participation factor transition (PFT), revealing the existence of PFT in open-loop modal interactions and the necessity of untraceable PFT in modal resonance. Secondly, participation factor transition analysis (PFT analysis) is conducted to investigate the contribution of PFT to modal interactions. Two categories of the PFT phenomenon, named participation factor conservation law (PFCL) and borrowing participation factor law (BPFL), are proposed to explain the essential mechanism of modal interactions in power systems. Participation factor transition index (PFTI) is proposed to determine whether PFT is traceable and then identify the dominant state variables that affect the modal interactions. Additionally, participation factor transition control (PFT control) is proposed to solve the modal resonance based on PFT analysis. Finally, the proposed participation factor transition analysis and control (PFTAC) are validated in two converter-based power systems, which not only verifies the critical role of PFT in modal interactions but also improves the small-signal stability of the power system.