Analysis of Phase-Locked Loop Low-Frequency Stability in Three-Phase Grid-Connected Power Converters Considering Impedance Interactions
Analysis of Phase-Locked Loop Low-Frequency Stability in Three-Phase Grid-Connected Power Converters Considering Impedance Interactions
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DOI：
10.1109/tie.2014.2334665
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发表时间：
2015
影响因子：
7.7
通讯作者：
D. Dong;B. Wen;D. Boroyevich;P. Mattavelli;Yaosuo Xue
中科院分区：
文献类型：
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作者：
D. Dong;B. Wen;D. Boroyevich;P. Mattavelli;Yaosuo Xue
同步参照系锁相环是实现三相并网变流器控制和并网同步的关键器件。传统的线性锁相环模型可能无法捕捉到不同电网和负载阻抗以及工作模式对锁相环特性，特别是低频动态特性的影响，目前尚未研究。本文提出了一种状态反馈的准静态SRF-PLL模型，该模型可以识别和量化变换器控制系统中固有的频率自同步机制。这种自同步效应主要是由于变流器与电网阻抗和潮流方向的相互作用。分析了不同电网阻抗条件下锁相环的低频非线性行为，形成了评估分布式发电机组大渗透水平、弱电网、微电网和大无功功耗对锁相环频率稳定性影响的框架。具体而言，研究了孤岛条件下变换器系统的锁相环行为，以解释早期出版物和行业报告中的锁相环不稳定性问题和相关的孤岛检测方法。
Synchronous reference frame (SRF) phase-locked loop (PLL) is a critical component for the control and grid synchronization of three-phase grid-connected power converters. The PLL behaviors, especially its low-frequency dynamics, influenced by different grid and load impedances as well as operation mode have not been investigated yet, which may not be captured by conventional linear PLL models. In this paper, we propose a state-feedback quasi-static SRF-PLL model, which can identify and quantify the inherent frequency self-synchronization mechanism in the converter control system. This self-synchronization effect is essentially due to the converter interactions with grid impedance and power flow directions. The low-frequency nonlinear behaviors of the PLL under different grid impedance conditions are then analyzed, which forms the framework of evaluating the impacts of the large penetration level of distributed generation units, weak grid, microgrid, and large reactive power consumption in terms of the frequency stability of PLL. Specifically, the PLL behavior of the converter system under islanded condition is investigated to explain the PLL instability issues and the related islanding-detection methods in early publications and industry reports.