@article{LIAO2026, 
author = {Yuming LIAO and Jianyong ZHAO and Zhen HE and Pingping CHEN and Yanxue YU and Min WU and Heng NIAN},
title = {Coupled oscillation stability analysis and improvement of three-phase four-wire distribution systems with high-penetration distributed renewable energy},
year = {2026},
journal = {Experimental Technology and Management},
volume = {43},
number = {10},
pages = {96-104},
keywords = {three-phase four-wire system, quantitative stability analysis method, dual-frequency coupling effect, stability enhancement method},
url = {https://www.sciopen.com/article/10.16791/j.cnki.sjg.2026.10.013},
doi = {10.16791/j.cnki.sjg.2026.10.013},
abstract = {ObjectiveThe high penetration of distributed photovoltaic generation and energy storage has intensified the dynamic interactions between grid-connected converters and low-voltage distribution networks. In three-phase four-wire systems, the integration of single-phase inverters, unbalanced operating conditions, neutral-line impedance, and zero-sequence components further complicates small-signal stability analysis. Existing state-space and impedance-based methods have been primarily developed for three-phase three-wire systems and are insufficient for describing the coupled oscillation characteristics arising from positive-, negative-, and zero-sequence interactions. To address this issue, this study proposes a quantitative stability analysis and improvement method for multinode three-phase four-wire systems with distributed renewable energy integration.MethodsAdmittance models of key components, including single-phase photovoltaic inverters, three-phase four-leg energy storage inverters, grid impedance, line impedance, and impedance loads, were established in the sequence domain. Dual-frequency and sequence-component coupling were considered during the modeling process. Based on the component admittance models and the system topology, an s-domain nodal admittance matrix was constructed for the multinode three-phase four-wire system. Oscillation modes were obtained by solving for the zeros of the determinant of the nodal admittance matrix. To identify the dominant oscillation sources and weak nodes, a nodal participation factor was derived from the modal information of the nodal admittance matrix. In addition, a parameter sensitivity calculation method was developed to quantify the influence of control parameters on the damping and frequency of each oscillation mode. A stability improvement strategy was then designed by jointly considering nodal participation factors and parameter sensitivities. During the optimization process, parameters with a strong influence on unstable modes but a limited influence on other stable modes were selected and adjusted within their allowable ranges.ResultsA Belgian seven-node low-voltage radial distribution feeder equipped with distributed photovoltaic units and a three-phase four-leg energy storage inverter was used for verification. The results show that the oscillation modes of the three-phase four-wire system form coupled mode groups because of interactions among different sequence components and frequencies. Nodal participation factor analysis indicates that photovoltaic units connected to terminal nodes make dominant contributions to the critical oscillation modes. Before optimization, one oscillation mode exhibited insufficient damping, indicating potential instability. After applying the proposed parameter optimization strategy, the phase-locked-loop and current-controller parameters were adjusted in a coordinated manner, and the critical oscillation mode moved into the stable region. Compared with a strategy that adjusts only a single control parameter, the proposed method avoids deteriorating other stable modes and improves the overall stability margin. Time-domain simulation results further show that oscillatory components in the grid-connected current, voltage, and power are rapidly attenuated after parameter optimization. Fast Fourier Transform(FFT) results demonstrate that the total harmonic distortion of the grid-connected current decreases.ConclusionsThe proposed method can accurately characterize the coupled oscillation behavior of three-phase four-wire systems by incorporating dual-frequency and sequence-component coupling into the nodal admittance matrix. The nodal participation factor provides an effective tool for locating oscillation sources and weak nodes, whereas parameter sensitivity analysis offers a quantitative basis for control-parameter optimization. The case study verifies that the proposed stability improvement strategy can suppress coupled oscillations, enhance system damping, and improve the system’s operational stability in three-phase four-wire grid-connected systems with a high penetration of distributed renewable energy.}
}