MODEL CONVERSION AND ON-SITE VERIFICATION OF SEQUENCE AND dq IMPEDANCE OF GRID-CONNECTED CONVERTERS CONSIDERING EFFECTS OF REFERENCE FRAME

Li Pengkun; Li Shaolin; Qin Shiyao; Li Qing; Li Chunyan

doi:10.19912/j.0254-0096.tynxb.2025-0196

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Acta Energiae Solaris Sinica ›› 2026, Vol. 47 ›› Issue (1) : 395-405. DOI: 10.19912/j.0254-0096.tynxb.2025-0196

MODEL CONVERSION AND ON-SITE VERIFICATION OF SEQUENCE AND dq IMPEDANCE OF GRID-CONNECTED CONVERTERS CONSIDERING EFFECTS OF REFERENCE FRAME

Li Pengkun, Li Shaolin, Qin Shiyao, Li Qing, Li Chunyan

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Abstract

The impedance models of grid-connected converters mainly include two categories： sequence impedance and dq impedance. However, the existing conversion relationship between these two types of impedances is complex and lacks universality, which does not consider the actual initial phase of the reference frame and limits the cross-checking and practical application of the theoretical impedance models. Therefore, this paper first explores the impact path of the initial phase of the reference frame on impedance modeling mechanistically, then establishes the comprehensive mathematical relationship between dq impedance, MIMO sequence impedance, and equivalent SISO sequence impedance considering the initial phases, and summarizes the universal conversion formulas. Based on this, dq impedance in the negative frequency band is defined, which simplifies the conversion between sequence impedance below the fundamental frequency and dq impedance. The symmetric frequency conjugation characteristics of dq impedance are revealed, and then the universality of the impedance conversion relationship is ensured. Furthermore, the influences of the initial phase on impedance measurement and stability criteria implementation are elaborated. A reference frame phase correction method is proposed, which achieves mutual verification between impedances in any reference frame. Finally, the accuracy and effectiveness of the theoretical analysis are verified through wind turbine simulation and on-site frequency sweeping tests.

Key words

grid-connected converter / sequence impedance / dq impedance / impedance conversion / initial phase of reference frame

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Li Pengkun, Li Shaolin, Qin Shiyao, Li Qing, Li Chunyan. MODEL CONVERSION AND ON-SITE VERIFICATION OF SEQUENCE AND dq IMPEDANCE OF GRID-CONNECTED CONVERTERS CONSIDERING EFFECTS OF REFERENCE FRAME[J]. Acta Energiae Solaris Sinica. 2026, 47(1): 395-405 https://doi.org/10.19912/j.0254-0096.tynxb.2025-0196

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