Analysis on Stability Criterion and Interaction Law of Grid-connected Inverter Control Loop Under Weak Grid Condition

被引：0
|
作者：
Liu F. [1 ]
Liu W. [1 ]
Xu Y. [1 ]
Li Y. [1 ]
机构：
[1] School of Electric Engineering and Automation, Hefei University of Technology, Anhui Province, Hefei
来源：
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | 2023年 / 43卷 / 02期
基金：
中国国家自然科学基金;
关键词：
control loop stability criterion; controller bandwidth; interaction law; ratio of bandwidth; stability boundary; weak grid;
D O I：
10.13334/j.0258-8013.pcsee.220697
中图分类号：
学科分类号：
摘要：
In order to analyze the influence of the interaction between the weak grid and the inverter on the stability of the new energy grid-connected system, this paper divides the current loop open-loop transfer function G0, which is characterized by the closed-loop stability performance of the system, into three links. The three links of impedance, phase-locked loop and current controller are multiplied, and the equivalent loop ratio expression is obtained by combining the phase-locked loop and the grid impedance link and divided by the current controller. The grid-connected inverter control loop stability criterion is proposed based on Nyquist's theorem. When the amplitude of G0 numerator and denominator are equal, the amplitude-frequency curve would generate an intersection point, which is easy to make the system closed-loop gain infinite and unstable. Then, in order to analyze the interaction law among the three links, this paper derives the expression of the bandwidth ratio n of the phase-locked loop and the current controller that satisfies the stability criterion. When the critical value is n, there will be an interaction between each link, which is mainly represented by the overlap of the G0 numerator and denominator amplitude-frequency curves in the Bode plot. The weaker the power grid or the closer the PLL and the current controller bandwidth are, the larger the overlapping area of the frequency curves, the easier it is to cause the closed-loop gain to be infinite, that is, the more likely the system is to be unstable; in addition, when the current controller bandwidth is fixed, the critical value of n is between less than 1 and greater than 1 as the power grid weakens. The bandwidth ratio of the phase-locked loop to the current controller is greater or less than 1, which can make the system remain stable. Finally, the accuracy of the theoretical analysis is verified by Matlab simulation and HIL experiment. ©2023 Chin.Soc.for Elec.Eng.
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页码：466 / 481
页数：15
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