基于单输入单输出等效序阻抗的微网VSG并网稳定性分析及虚拟阻抗设计

doi:10.19595/j.cnki.1000-6753.tces.230077

Abstract
Figure/Table
References (0)
Related Citation (15)

Download: PDF (4486 KB) HTML (1 KB)
Export: BibTeX | EndNote (RIS)

Abstract

In microgrid with high penetration of distributed generation, the generalized Nyquist criterion based on return rate matrix or return difference matrix is often used to analyse the grid-connection stability of virtual synchronous generator (VSG), but the calculation process is complicated. Besides, existing studies have not identified the root cause of the instability of VSG's integration into the strong grid, and the mechanism analysis of the influence of frequency coupling effect on the output impedance characteristics of VSG remains to be deepened. In terms of stability improvement, existing virtual impedance design methods do not take full advantage of the characteristics of VSG output impedance and its interaction with the grid impedance, and there is still room for further simplification. Therefore, this paper conducts a comprehensive and systematic research on the mechanism analysis of microgrid VSG grid-connection stability and the design method of virtual impedance.
Firstly, on the basis of obtaining VSG output sequence impedance matrix, this paper analyses the grid-connection stability of VSG by establishing single input single output (SISO) equivalent model and combining with Nyquist criterion. Secondly, based on the established SISO equivalent sequence impedance model, the influence mechanism of frequency coupling effect on the output impedance characteristics of VSG and the root cause of the instability of VSG's integration into the strong grid are compared and analysed. Finally, based on the above mechanism analysis, this paper proposes a virtual impedance simplified design method to improve system stability, from the perspective of improving the amplitude margin of the system, this method directly uses the interaction relationship between SISO equivalent output impedance and grid impedance to realize the quantitative calculation of virtual impedance, which simplifies the design process of virtual impedance.
The results are as follows: first, the stability analysis method based on SISO equivalent sequence impedance model can easily obtain accurate stability analysis results, the results show that the instability of the system is caused by the sub-synchronous oscillation near the fundamental frequency of 50Hz. Second, the influence of frequency coupling effect on VSG positive sequence output impedance is mainly concentrated around the fundamental frequency 50Hz. Considering the frequency coupling effect before and after, VSG positive sequence impedance changes from capacitive to inductive in the frequency band affected by frequency coupling effect. Lastly, near the critical frequency point where VSG's positive sequence output impedance shows negative resistance capacitance, the influence of grid inductance changes on its impedance characteristics can be ignored. Therefore, the virtual impedance design method based on SISO equivalent sequence impedance proposed in this paper can quickly and accurately obtain the critical threshold of virtual inductance.
The following conclusions can be drawn from the above results: (1) The stability analysis method of VSG grid-connection system based on the SISO equivalent sequence impedance model can simplify the analysis process and lay a foundation for the subsequent quantitative design of virtual impedance. (2) Although the frequency coupling effect only affects the positive sequence impedance characteristics near the fundamental frequency 50Hz, but this is the key to judging the stability of the VSG grid-connection. Through further analysis, the negative resistance capacitance of VSG positive sequence output impedance in a specific frequency band is the root cause of the instability of VSG's integration into the strong grid, the virtual impedance value can be quantitatively designed according to this point to improve the system stability margin. (3) On the basis of the above conclusions, this paper proposes a virtual impedance simplified design method based on the SISO equivalent sequence impedance model. From the perspective of improving the amplitude margin of the system, this method can be used to design virtual inductance directly by calculating or measuring VSG positive sequence output impedance. It avoids the repeated iteration and complex calculation required by traditional methods, and has good applicability to different grid impedance and control parameters.

Key words： VSG SISO equivalent sequence impedance model frequency coupling effect stability analysis virtual impedance design

Received: 18 January 2023

PACS:

TM712

	Service

	E-mail this article
	Add to my bookshelf
	Add to citation manager
	E-mail Alert
	RSS
	Articles by authors
	Liu Xin
	Guo Zhibo
	Jia Jiaoxin
	Wang Litong

Cite this article:

Liu Xin,Guo Zhibo,Jia Jiaoxin等. Microgrid VSG Grid-Connection Stability Analysis and Virtual Impedance Design Based on Single-Input Single-Output Equivalent Sequence Impedance[J]. Transactions of China Electrotechnical Society, 0, (): 20235427-20235427.

URL:

https://dgjsxb.ces-transaction.com/EN/10.19595/j.cnki.1000-6753.tces.230077 OR https://dgjsxb.ces-transaction.com/EN/Y0/V/I/20235427

[1] 任碧莹, 邱姣姣, 刘欢, 等. 基于虚拟同步发电机双机并联系统的参数自调节优化控制策略[J]. 电工技术学报, 2019, 34(1): 128-138
Ren Biying, Qiu Jiaojiao, Liu Huan, et al.Optimization control strategy of self-adjusting parameter based on dual-parallel virtual synchronous generators[J]. Transactions of China Electrotechnical Society, 2019, 34(1): 128-138
[2] 缪惠宇, 梅飞, 张宸宇, 等. 基于虚拟阻抗的虚拟同步整流器三相不平衡控制策略[J]. 电工技术学报, 2019, 34(17): 3622-3630
Miao Huiyu, Mei Fei, Zhang Chenyu, et al.Three phase unbalanced control strategy for virtual synchronous rectifier based on virtual impedance[J]. Transactions of China Electrotechnical Society, 2019, 34(17): 3622-3630
[3] 于彦雪, 关万琳, 陈晓光, 等. 基于序阻抗的虚拟同步机同步频率谐振现象[J]. 电工技术学报, 2022, 37(10): 2584-2595
Yu Yanxue, Guan Wanlin, Chen Xiaoguang, et al.Synchronous frequency resonance in virtual synchronous generator based on sequence-impedance[J]. Transactions of China Electrotechnical Society, 2022, 37(10): 2584-2595
[4] Kalcon G O, Adam G P, Anaya-Lara O, et al.Small-signal stability analysis of multi-terminal VSC-based DC transmission systems[J]. IEEE Transactions on Power Systems, 2012, 27(4): 1818-1830.
[5] 邹小明, 杜雄, 王国宁, 等. 三相并网逆变器频率耦合机理分析及稳定性判定[J]. 电力系统自动化, 2018, 42(18): 57-63
Zou Xiaoming, Du Xiong, Wang Guoning, et al.Frequency coupling mechanism analysis and stability judgement for three-phase grid-connected inverter[J]. Automation of Electric Power Systems, 2018, 42(18): 57-63
[6] 年珩, 杨洪雨. 不平衡运行工况下并网逆变器的阻抗建模及稳定性分析[J]. 电力系统自动化, 2016, 40(10): 76-83
Nian Heng, Yang Hongyu.Impedance modeling and stability analysis of grid-connected inverters under unbalanced operation conditions[J]. Automation of Electric Power Systems, 2016, 40(10): 76-83
[7] R. D. Middlebrook, “Input filter considerations in design and application of switching regulators,” in Proc. IEEE Ind. Appl. Soc. Annu. Meeting, 1976, pp. 366-382.
[8] Sun Jian.Impedance-based stability criterion for grid-connected inverters[J]. IEEE Transactions on Power Electronics, 2011, 26(11): 3075-3078.
[9] Wu Wenhua, Chen Yandong, Zhou Leming, et al.Sequence impedance modeling and stability comparative analysis of voltage-controlled VSGs and current-controlled VSGs[J]. IEEE Transactions on Industrial Electronics, 2019, 66(8): 6460-6472.
[10] Peng Yang, Yin Taiyuan, Li Mingxuan, et al.A sequence impedance modeling of VSG with consideration of inner loops control[C]//2019 4th IEEE Workshop on the Electronic Grid (eGRID), Xiamen, China, 2020: 1-5.
[11] Shi Kai, Wang Yu, Sun Yuxin, et al.Frequency-coupled impedance modeling of virtual synchronous generators[J]. IEEE Transactions on Power Systems, 2021, 36(4): 3692-3700.
[12] Kazem Bakhshizadeh M, Wang Xiongfei, Blaabjerg F, et al.Couplings in phase domain impedance modeling of grid-connected converters[J]. IEEE Transactions on Power Electronics, 2016, 31(10): 6792-6796.
[13] Wen Bo, Boroyevich D, Burgos R, et al.Inverse nyquist stability criterion for grid-tied inverters[J]. IEEE Transactions on Power Electronics, 2017, 32(2): 1548-1556.
[14] 李信栋, 苟兴宇. 多输入多输出线性定常系统稳定裕度的分析与改进[J]. 控制理论与应用, 2014, 31(1): 105-111
Li Xindong, Gou Xingyu.Analysis and improvement of stability margin for multi-input multi-output linear time-invariant systems[J]. Control Theory & Applications, 2014, 31(1): 105-111
[15] 李彪. 基于谐波线性化的三相并网逆变器系统建模和稳定性分析[D]. 重庆: 重庆大学, .
[16] Zhang Chen, Cai Xu, Rygg A, et al.Sequence domain SISO equivalent models of a grid-tied voltage source converter system for small-signal stability analysis[J]. IEEE Transactions on Energy Conversion, 2018, 33(2): 741-749.
[17] 武相强, 王赟程, 陈新, 等. 考虑频率耦合效应的三相并网逆变器序阻抗模型及其交互稳定性研究[J]. 中国电机工程学报, 2020, 40(5): 1605-1616.
Wu Xiangqiang, Wang Yuncheng, Chen Xin, et al.Sequence impedance model and interaction stability research of three-phase grid-connected inverters with considering coupling effects[J]. Proceedings of the CSEE, 2020, 40(5): 1605-1616.
[18] 杜燕, 赵韩广, 杨向真, 等. 考虑频率耦合效应的虚拟同步发电机序阻抗建模[J]. 电源学报, 2020, 18(6): 42-49.
Du Yan, Zhao Hanguang, Yang Xiangzhen, et al.Sequence impedance modeling of virtual synchronous generator considering frequency coupling effect[J]. Journal of Power Supply, 2020, 18(6): 42-49.
[19] Yang Dongsheng, Ruan Xinbo, Wu Heng.Impedance shaping of the grid-connected inverter with LCL filter to improve its adaptability to the weak grid condition[J]. IEEE Transactions on Power Electronics, 2014, 29(11): 5795-5805.
[20] 郭强, 周琛力, 李山. 面向电流源型PWM整流器直流侧电压的多环路控制策略[J]. 电工技术学报, 2022, 37(8): 2051-2063.
Guo Qiang, Zhou Chenli, Li Shan.A multiple loops control strategy based on DC link voltage of current source PWM rectifiers[J]. Transactions of China Electrotechnical Society, 2022, 37(8): 2051-2063.
[21] 游逍遥, 刘和平, 苗轶如, 等. 带恒功率负载的双极性直流系统稳定性分析及其有源阻尼方法[J]. 电工技术学报, 2022, 37(4): 918-930.
You Xiaoyao, Liu Heping, Miao Yiru, et al.Stability analysis and active damping method of the bipolar DC system with constant power loads[J]. Transactions of China Electrotechnical Society, 2022, 37(4): 918-930.
[22] Zhang Xueguang, Xia Danni, Fu Zhichao, et al.An improved feedforward control method considering PLL dynamics to improve weak grid stability of grid-connected inverters[J]. IEEE Transactions on Industry Applications, 2018, 54(5): 5143-5151.
[23] 徐健, 曹鑫, 郝振洋, 等. 基于电网谐波电压前馈的虚拟同步整流器电流谐波抑制方法[J]. 电工技术学报, 2022, 37(8): 2018-2029.
Xu Jian, Cao Xin, Hao Zhenyang, et al.A harmonic-current suppression method for virtual synchronous rectifier based on feedforward of grid harmonic voltage[J]. Transactions of China Electrotechnical Society, 2022, 37(8): 2018-2029.
[24] 袁敞, 丛诗学, 徐衍会. 应用于微电网的并网逆变器虚拟阻抗控制技术综述[J]. 电力系统保护与控制, 2017, 45(9): 144-154.
Yuan Chang, Cong Shixue, Xu Yanhui.Overview on grid-connected inverter virtual impedance technology for microgrid[J]. Power System Protection and Control, 2017, 45(9): 144-154.
[25] Wen Tiliang, Zou Xudong, Zhu Donghai, et al.Comprehensive perspective on virtual inductor for improved power decoupling of virtual synchronous generator control[J]. IET Renewable Power Generation, 2020, 14(4): 485-494.
[26] 代维, 秦文萍, 任春光, 等. 含同步机微网中基于解耦下垂的自适应虚拟阻抗控制[J]. 中国电机工程学报, 2020, 40(14): 4486-4495.
Dai Wei, Qin Wenping, Ren Chunguang, et al.Adaptive virtual impedance control based on decoupling droop in microgrid with synchronous generators[J]. Proceedings of the CSEE, 2020, 40(14): 4486-4495.
[27] 周兵凯, 杨晓峰, 李继成, 等. 一种用于优化LC-DAB级联系统稳定性的虚拟阻抗控制技术[J]. 电工技术学报, 2021, 36(18): 3946-3956.
Zhou Bingkai, Yang Xiaofeng, Li Jicheng, et al.Virtual impedance control technology for stability optimization of LC-DAB cascaded system[J]. Transactions of China Electrotechnical Society, 2021, 36(18): 3946-3956.
[28] 石荣亮, 张兴, 徐海珍, 等. 光储柴独立微电网中的虚拟同步发电机控制策略[J]. 电工技术学报, 2017, 32(23): 127-139.
Shi Rongliang, Zhang Xing, Xu Haizhen, et al.A control strategy for islanded photovoltaic-battery-diesel microgrid based on virtual synchronous generator[J]. Transactions of China Electrotechnical Society, 2017, 32(23): 127-139.
[29] 温春雪, 黄耀智, 胡长斌, 等. 虚拟同步发电机接口变换器并联运行虚拟阻抗自适应控制[J]. 电工技术学报, 2020, 35(增刊2): 494-502.
Wen Chunxue, Huang Yaozhi, Hu Changbin, et al.Adaptive control of virtual impedance in parallel operation of virtual synchronous generator interface converter[J]. Transactions of China Electrotechnical Society, 2020, 35(S2): 494-502.
[30] 杜燕, 朱轲, 杨向真, 等. 考虑频率耦合的VSG虚拟阻抗优化设计[J]. 高电压技术, 2022, 48(12): 5057-5067.
Du Yan, Zhu Ke, Yang Xiangzhen, et al.Optimal design of virtual synchronous generator virtual impedance considering frequency coupling[J]. High Voltage Engineering, 2022, 48(12): 5057-5067.
[31] Rygg A, Molinas M, Zhang Chen, et al.A modified sequence-domain impedance definition and its equivalence to the dq-domain impedance definition for the stability analysis of AC power electronic systems[J]. IEEE Journal of Emerging and Selected Topics in Power Electronics, 2016, 4(4): 1383-1396.
[32] 胡寿松. 自动控制原理[M]. 7版. 北京: 科学出版社, 2019.
[33] Etxegarai A, Eguia P, Torres E, et al.Impact of wind power in isolated power systems[C]//2012 16th IEEE Mediterranean Electrotechnical Conference, Yasmine Hammamet, Tunisia, 2012: 63-66.
[34] Cao Wenchao, Ma Yiwei, Wang F.Sequence-impedance-based harmonic stability analysis and controller parameter design of three-phase inverter-based multibus AC power systems[J]. IEEE Transactions on Power Electronics, 2017, 32(10): 7674-7693.
[35] 屈子森, 蔡云旖, 杨欢, 等. 基于自适应虚拟阻抗的虚拟同步机功率解耦控制策略[J]. 电力系统自动化, 2018, 42(17): 58-66.
Qu Zisen, Cai Yunyi, Yang Huan, et al.Strategy of power decoupling control for virtual synchronous generator based on adaptive virtual impedances[J]. Automation of Electric Power Systems, 2018, 42(17): 58-66.
[36] 陈杰, 闫震宇, 赵冰, 等. 下垂控制三相逆变器阻抗建模与并网特性分析[J]. 中国电机工程学报, 2019, 39(16): 4846-4856.
Chen Jie, Yan Zhenyu, Zhao Bing, et al.On the impedance modelling and grid-connected characteristics of the three-phase droop controlled inverter[J]. Proceedings of the CSEE, 2019, 39(16): 4846-4856.
[37] Yang Yaqian, Xu Jiazhu, Li Chang, et al.A new virtual inductance control method for frequency stabilization of grid-forming virtual synchronous generators[J]. IEEE Transactions on Industrial Electronics, 2023, 70(1): 441-451.
[38] Familiant Y A, Huang Jing, Corzine K A, et al.New techniques for measuring impedance characteristics of three-phase AC power systems[J]. IEEE Transactions on Power Electronics, 2009, 24(7): 1802-1810.
[39] 谢少军, 季林, 许津铭. 并网逆变器电网阻抗检测技术综述[J]. 电网技术, 2015, 39(2): 320-326.
Xie Shaojun, Ji Lin, Xu Jinming.Review of grid impedance estimation for gird-connected inverter[J]. Power System Technology, 2015, 39(2): 320-326.
[40] 李杨, 帅智康, 方俊彬, 等. 基于阻抗测量的多逆变器系统稳定性校验方法[J]. 电力系统自动化, 2021, 45(11): 95-101.
Li Yang, Shuai Zhikang, Fang Junbin, et al.Stability check method for multi-inverter system based on impedance measurement[J]. Automation of Electric Power Systems, 2021, 45(11): 95-101.
[41] Timbus A V, Rodriguez P, Teodorescu R, et al.Line impedance estimation using active and reactive power variations[C]//2007 IEEE Power Electronics Specialists Conference, Orlando, FL, USA, 2007: 1273-1279.