A General P / ω Admittance Modeling Framework for Low-Frequency Oscillation Analysis of Grid-Forming and Grid-Following VSCs

$P$/$\omega $admittance modeling is one of effective techniques to analyze the low-frequency oscillation (LFO). However, existing modeling methods are typically developed for specific control strategies on a case-by-case basis, lacking a general framework. Such case-specific formulations limit the broader applicability of this model in power system studies. To address this limitation, a general$P$/$\omega $admittance modeling framework is proposed based on the equivalence of controlled source and impedance (ECSI). In the proposed framework, the VSC is modeled as a controlled frequency source, which is regulated by both active power and the frequency at the filter terminal, whereas the reactive power-voltage dynamics are modeled as an equivalent admittance in parallel with the line admittance. Such a modeling strategy enables the construction of$P$/$\omega $admittance models for VSCs with diversified controls, using a consistent and intuitive framework. Leveraging the model’s transparency, the LFO characteristics of various VSCs are identified. The case study of a multi-VSC system demonstrates that the proposed model can accurately reflect the interactions among control loops and reveals the characteristics of LFO caused by different controls of VSCs, providing a powerful tool for stability analysis and control design. Finally, comprehensive simulations under various scenarios are conducted to verify the accuracy of the proposed model.