Immittance-based frequency-domain method for sub synchronous torsional resonance analysis

Immittance-based frequency-domain analysis has been widely applied in the assessment of electrical and converter-driven resonance stability. This paper extends the scope of this method by introducing its application to torsional resonance stability, thereby establishing a unified analytical framework for evaluating both electrical and mechanical resonance phenomena. The proposed framework integrates theoretical foundations with structured methodological procedures, enabling a systematic approach to resonance stability assessment in frequency domain. To demonstrate its practical relevance, the framework is evaluated through detailed case studies based on the Swedish transmission system and Electromagnetic Transient (EMT) simulations. The results confirm the method’s accuracy and…