电工技术学报  2024, Vol. 39 Issue (14): 4519-4534    DOI: 10.19595/j.cnki.1000-6753.tces.230793
电力电子 |
结合特征根及模态分析法的逆变器多机并网系统谐波扰动响应分析
李戎1, 李建文1, 李永刚1, 孙伟2
1.新能源电力系统国家重点实验室(华北电力大学) 保定 071003;
2.国网河北省电力有限公司保定供电分公司 保定 071000
Analysis of Harmonic Disturbance Response of Multi-Inverter Grid-Connected System Combining Characteristic Root and Modal Analysis Method
Li Rong1, Li Jianwen1, Li Yonggang1, Sun Wei2
1. State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University Baoding 071003 China;
2. Baoding Power Supply Subsidiary Company of State Grid Hebei Electric Power Supply Co. Ltd Baoding 071000 China
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摘要 为了从本质上解释逆变器多机并网系统受到宽频谐波扰动后的动态行为,该文理论推导特征根与系统稳态和暂态响应的解析解,进而利用单个逆变器并网的实例验证了采用特征根分析系统谐波响应的可行性。针对逆变器多机并网系统,阐明特征根与谐振模态的对应关系,使得利用模态分析方法既能解析系统内部支路对不同谐振模态的可激励性和可观测性,又能视系统为一个整体对其稳定性进行分析。最后,通过仿真与实验验证了结合特征根分析逆变器并网系统动态行为的正确性及有效性。
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关键词 特征根谐波扰动模态分析方法稳态响应暂态响应    
Abstract:The broadband oscillation caused by the interaction of a high proportion of new energy connected to the grid, grid impedance and load is a typical system stability problem. In recent years, some overvoltage phenomena have been difficult to classify into the classical stability problems. The electromagnetic transient process driving this phenomenon differs from the power-angle relationship on the rotor-side generator models using phase-locked loops (PLLs).
To explain the dynamic behavior of inverter grid-connected systems disturbed by broadband harmonics, this paper derives a mathematical expression that characterizes the system's response to harmonic disturbances and analyzes the response's characteristics. Furthermore, the feasibility of analyzing harmonic responses using characteristic roots is verified by an example of a single inverter connected to the grid. The relationship between the characteristic root and the resonance mode is clarified for multi-inverter grid-connected systems. Finally, the dynamic behavior analysis is verified by simulation and experiments.
The harmonic disturbance response expression is derived according to the characteristic roots and the harmonic disturbance. It is found that the system's response comprises two waveforms: the steady-state response and the transient response. The resonance characteristics of these two responses differ, with the magnitude of the resonance peak closely related to the damping coefficient ξ. A large peak occurs when ξ is close to 0, gradually decreasing as ξ increases, and no steady-state response resonance peak is observed when ξ>0.7.
The characteristic root can effectively describe the harmonic disturbance response of inverter grid-connected systems. The dynamic behavior of the system after disturbance can be quantitatively analyzed by calculating the damping coefficient value. When multiple inverters are connected to the grid, the impedance-based system modeling method provides convenience for analyzing the stability of the inverter grid-connected system. The series and parallel resonance points in high-order networks are obtained by modal analysis. Accordingly, the characteristic roots of the system are obtained by converting the memory elements in the matrix from the frequency domain to the s domain, offering a simple and reusable approach to characterize coupling relationships within high-order networks and analyze system stability.
The proposed method is verified using a single inverter connected to the grid and three inverters with different parameters to be connected to the grid. It is found that the parameter design of a single inverter can meet grid-connected harmonic requirements. However, when multiple inverters are connected to the grid, the damping coefficient of a single inverter decreases with the number of parallel inverters. A smaller damping coefficient makes the system less capable of actively suppressing harmonic oscillations. The slow attenuation of transient components results in a significantly increased waveform distortion rate over a short period of time.
The following conclusions can be obtained through simulation and experiments: (1) As an analytical tool for finding system characteristic roots and traversing system resonance frequencies, the modal analysis method can provide numerical solutions and modal impedance curves simply and quickly. (2) The characteristic roots of the system can effectively describe the dynamic behavior of the system after disturbance. (3) A small damping coefficient renders the system susceptible to severe harmonic oscillations and deepens waveform distortion in a short period.
Key wordsCharacteristic root    harmonic disturbance    modal analysis method    steady-state response    transient response   
收稿日期: 2023-05-30     
PACS: TM464  
基金资助:中央高校基本科研业务费专项资金资助项目(2023MS109)
通讯作者: 李建文, 女,1983年生,副教授,硕士生导师,研究方向为新型配电网下电能质量分析与治理。E-mail: ljw_ncepu@163.com   
作者简介: 李戎, 男,1998年生,博士研究生,研究方向为逆变器建模、谐波劣化分析等。E-mail: lr_ncepu@163.com
引用本文:   
李戎, 李建文, 李永刚, 孙伟. 结合特征根及模态分析法的逆变器多机并网系统谐波扰动响应分析[J]. 电工技术学报, 2024, 39(14): 4519-4534. Li Rong, Li Jianwen, Li Yonggang, Sun Wei. Analysis of Harmonic Disturbance Response of Multi-Inverter Grid-Connected System Combining Characteristic Root and Modal Analysis Method. Transactions of China Electrotechnical Society, 2024, 39(14): 4519-4534.
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