Authors
Junli Zhang, Wenting Hou, Geli Zhang, Shuhan He, Ruoxi Cai
Published in
Scientific reports. Jun 27, 2026. Epub Jun 27, 2026.
Abstract
Under weak grid scenarios, wide variations of grid impedance distort resonance characteristics of LCL-type grid-connected inverters. Digital control delays introduce phase lag, which easily causes damping polarity reversal in conventional capacitor-current-feedback active damping strategies. From the perspective of impedance stability, this paper reveals that control delays produce frequency-dependent resistive components in equivalent damping impedance. The analytical boundary of positive-negative resistance transition is derived, which dominates the weak-grid adaptability of inverters. Accordingly, an impedance reshaping strategy based on phase-lead delay compensation is proposed. Embedded in the feedback loop, the phase-lead network extends the valid positive-resistance frequency region and decouples the inherent coupling between LCL resonance frequency and sampling frequency. The critical frequency is lifted from [Formula: see text] to above [Formula: see text], and the system maintains a stability margin over 45° within 0-10 mH grid inductance range. A quasi-proportional-resonant cascaded current regulator is further designed to suppress background harmonic interference. Simulation and experimental tests on a 5 kW prototype verify the superior performance. When grid inductance steps from 0 to 8 mH, grid-connected current THD remains below 2.8%, and transient response completes within two fundamental cycles. This study provides theoretical guidance and practical solution for stable grid integration of high-penetration renewable energy systems.
PMID:
42365071
Bibliographic data and abstract were imported from PubMed on 28 Jun 2026.
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