Coupling Impedance Modeling Analysis of Grid-Connected Inverters Under Three-Phase Voltage Unbalance

Yang Liu, Haidong Yu, Qihang Wu, Bin Wang (), Lisheng Li and Wenbin Liu
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Yang Liu: State Grid Shandong Electric Power Research Institute, Jinan 250003, China
Haidong Yu: State Grid Shandong Electric Power Research Institute, Jinan 250003, China
Qihang Wu: National Key Laboratory of New Power System Operation and Control, Department of Electrical Engineering Tsinghua University, Beijing 100084, China
Bin Wang: National Key Laboratory of New Power System Operation and Control, Department of Electrical Engineering Tsinghua University, Beijing 100084, China
Lisheng Li: State Grid Shandong Electric Power Research Institute, Jinan 250003, China
Wenbin Liu: State Grid Shandong Electric Power Research Institute, Jinan 250003, China

Energies, 2025, vol. 18, issue 3, 1-13

Abstract: Under the condition of asymmetric system voltage, grid-connected inverters exhibit obvious sequence impedance frequency coupling characteristics, which can easily lead to resonance and the misoperation of protection and control devices. Currently, targeted quantitative analyses are insufficient. To address this limitation, this paper identifies dominant harmonic pairs and develops an analytical model of an inverter’ second-order admittance under unbalanced grid voltage conditions. Considering the influence of the phase-locked loop and current control loop, the sequence impedance characteristics of a grid-connected inverter were quantitatively analyzed. The simulation results verified the accuracy of the model. The conclusion of the paper provides a foundation for subsequent research on the instability mechanism and oscillation suppression strategy of the grid-connected inverter and grid interconnection system.

Keywords: unbalanced three-phase voltages; grid-connected inverter; impedance modeling; frequency coupling (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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