电工技术学报  2023, Vol. 38 Issue (zk1): 18-31    DOI: 10.19595/j.cnki.1000-6753.tces.L10069
电力系统与综合能源 |
频率突变影响下基于Lyapunov法的孤岛微电网暂态稳定性分析
李锡林, 查晓明, 田震, 黄萌, 胡宇飞
武汉大学电气与自动化学院 武汉 430072
Lyapunov Based Transient Stability Analysis of Islanded Microgrid under the Influence of Frequency Abrupt Change
Li Xilin, Zha Xiaoming, Tian Zhen, Huang Meng, Hu Yufei
School of Electrical Engineering and Automation Wuhan University Wuhan 430072 China
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摘要 以电力电子变流器为主导的微电网作为一种灵活、可靠的分布式能源消纳和集成方式,近年来越来越受到关注。由于缺少电网稳定的电压和频率支撑,孤岛微电网在故障扰动下易出现暂态失稳现象。考虑锁相环受扰瞬间的被动频率突变和下垂控制器无功环影响,该文建立了由构网型和跟网型逆变器共同组成的孤岛微电网的改进暂态模型,改善了暂态模型精度。在此基础上,构建了一种二次型Lyapunov函数,用于孤岛微电网的暂态稳定性分析。通过待定系数,减小了非耗散区的影响,从而改善了传统Lyapunov方法的保守性。利用Lyapunov稳定判据,对不同形式扰动下的功角稳定边界进行了估计,分析了孤岛微电网对不同形式扰动的敏感度,揭示了系统参数对暂态稳定性的影响。最后,利用Matlab/Simulink仿真和基于RT-Lab的硬件在环实验对该文所提方法进行了验证。
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李锡林
查晓明
田震
黄萌
胡宇飞
关键词 并网逆变器孤岛微电网同步稳定性频率突变Lyapunov稳定判据    
Abstract:As an effective and reliable distributed energy integration and consumption mode, converter-based microgrids can operate in grid-connected mode and islanded mode Due to the lack of stable voltage and frequency support, the islanded microgrid is prone to lose stability under fault disturbance. Besides, various converters with different control types interact with each other in the microgrid, making the system easier to lose stability. The interactions of GFL-VSC and GFM-VSC in the islanded microgrid system and their effects on system stability are rarely analyzed in the former studies. In addition, due to the negative damping characteristics of GFL-VSC, the analysis methods of the previous studies are quite conservative. A new Lyapunov analysis method based on quadratic form principle considering PLL frequency mutation effect is proposed in this paper, which provides a conservatively improved stability region estimation.
Firstly, a conventional second order nonlinear mathematical model of GFL-VSC parallel GFM-VSC system considering the effect of reactive power loop is established. Simulation comparison shows that the conventional model has some transient errors. Secondly, a passive frequency mutation effect widely exists in GFL-VSCs is revealed, which is caused by the proportional controller of PLL. By deducing a unified frequency mutation formula for different types of large disturbances, a modified model considering frequency mutation effect is obtained, which greatly improves the transient-state error of the existing conventional model. Third, considering the influence of reactive power loop on the output voltage of GFM-VSC, a new parametric Lyapunov function based on quadratic form theory is proposed. By undetermined coefficient, the obtained dissipation interval is larger than that of conventional Lyapunov function. Therefore, a less conservative estimation of the transient stable domain of islanded microgrid system can be obtained. The less-conservatism of the proposed method is mathematical proved. Fourthly, considering the frequency mutation effect and combining with the obtained stable domain, the power angle stability range corresponding to different disturbance forms is derived, and the conclusion is drawn that the sensitivity of the system to different disturbance forms is different. Fifth, from the point of view of physical mechanism, the influence of dynamic interaction between GFL-VSC and GFM-VSC on the stability of the islanded microgrid system is explored, and corresponding to the terms in the state space equation. Sixth, based on the proposed Lyapunov's method, the size of transient stable domain of the islanded microgrid system is derived and compared to analyze the influence of different network parameters and controller parameters on the stability of the islanded microgrid system. Finally, the proposed method is verified by MATLAB/Simulink simulation and the RT-Lab based hardware-in-loop experiments.
The following conclusions can be drawn from this paper: (1) The output frequency of the PLL will mutate due to the sudden change of voltage at the PCC when the converter is disturbed under large disturbance. Conventional modeling method ignore this phenomenon, which leads to transient model errors and potential misjudgment of stability. (2) Based on the different frequency mutation mechanism of different disturbances, the sensitivity of the islanded microgrid system to different forms of disturbances is different. The sensitivity order is voltage disturbance>current disturbance>inductance disturbance>phase disturbance. The higher the sensitivity, the more likely the system instability occurs. (3) The larger the voltage reference value, the stronger the system stability. The smaller the current reference value, droop coefficient and line inductance, the stronger the system stability will be. The influence of PLL's parameters on the stability is more complex and not a monotonous relationship. The larger the reactive load and reactive droop coefficient, the worse the system stability.
Key wordsGrid-connected inverter    islanded microgrid    synchronization stability    frequency mutation    Lyapunov stability criterion   
收稿日期: 2023-01-09      出版日期: 2023-11-09
PACS: TM464  
基金资助:国家重点研发计划项目(2022YFB2402701)和国家自然科学基金青年项目(52007134)资助
通讯作者: 查晓明 男,1967年生,博士,教授,博士生导师,研究方向为大功率电力电子装置等。E-mail:xmzha@whu.edu.cn   
作者简介: 李锡林 男,1999年生,博士研究生,研究方向为电力电子化电力系统暂态稳定性分析E-mail:snplee@whu.edu.cn
引用本文:   
李锡林, 查晓明, 田震, 黄萌, 胡宇飞. 频率突变影响下基于Lyapunov法的孤岛微电网暂态稳定性分析[J]. 电工技术学报, 2023, 38(zk1): 18-31. Li Xilin, Zha Xiaoming, Tian Zhen, Huang Meng, Hu Yufei. Lyapunov Based Transient Stability Analysis of Islanded Microgrid under the Influence of Frequency Abrupt Change. Transactions of China Electrotechnical Society, 2023, 38(zk1): 18-31.
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