A Unified Reduced-Order Approach for Grid-Interfaced DC/AC Converters

Small-signal impedance/admittance models are vital for stability analysis in systems with dc/ac converters. However, these converters often have higher orders compared to conventional power system devices such as synchronous generators. This complexity can hinder the analysis of grids with a high penetration of converters. Existing model order reduction methods often rely on numerical approximations or piecewise models tailored to specific frequency bands, which have high complexity and limited practical applicability. To address these issues, this article proposes a unified model reduction approach for various grid converters, offering symbolic expressions and covering a wide frequency range up to the Nyquist frequency. The proposed model aims to simplify analysis without sacrificing accuracy, addressing the challenges posed by varying system parameters or operating points. The accuracy of the proposed model is validated through comprehensive theoretical analysis and experimental verification.