Sequence Impedance Modeling and Stability Analysis of Load Converter with Virtual Inertia Control Connected to Weak Grid
Liu Yifeng1, Zhou Xiaoping1, Hong Lerong1, Xia Haitao1, Tian Hao2
1. National Electric Power Conversion and Control Engineering Technology Research Center Hunan University Changsha 410082 China; 2. State Grid Qianjiang Electric Power Company Qianjiang 433100 China
Abstract：Both load virtual synchronous machine (LVSM) and load converter based on DC-link capacitor virtual inertia control (DLCVIC-LC) can enhance the power system inertia. However, inevitably, there are some interaction problems like harmonic resonance in weak grids. In this paper, considering the DC-link voltage dynamics and frequency-coupling effects, the general sequence impedance formulas for three-phase load converters were derived. Then, the precise sequence impedance models were built for impedance characteristics comparison analysis of LVSM and DLCVIC-LC. The analysis shows that the positive-sequence impedance of LVSM is generally inductive, which is basically consistent with the grid impedance characteristics and hardly causes harmonic resonance. In contrast, the positive-sequence impedance of LCVIC is negative-resistive-capacitive (i.e., phase angle is between -180° and -90°) in the middle-frequency band, which is likely to cause harmonic oscillation in weak grids. Furthermore, based on the derived model and Nyquist stability criterion, the effects of grid impedance and other control parameters on the stability of the two load converters connected to the grid were analyzed. Finally, experiments were performed to validate the analysis.
刘一锋, 周小平, 洪乐荣, 夏海涛, 田皓. 虚拟惯性控制的负荷变换器接入弱电网的序阻抗建模与稳定性分析[J]. 电工技术学报, 2021, 36(4): 843-856.
Liu Yifeng, Zhou Xiaoping, Hong Lerong, Xia Haitao, Tian Hao. Sequence Impedance Modeling and Stability Analysis of Load Converter with Virtual Inertia Control Connected to Weak Grid. Transactions of China Electrotechnical Society, 2021, 36(4): 843-856.
[1] 郑天文, 陈来军, 陈天一, 等. 虚拟同步发电机技术及展望[J]. 电力系统自动化, 2015, 39(21): 165-175. Zheng Tianwen, Chen Laijun, Chen Tianyi, et al.Review and prospect of virtual synchronous generator technologies[J]. Automation of Electric Power Systems, 2015, 39(21): 165-175. [2] Zhong Qingchang, Weiss G.Synchronverters: inver- ters that mimic synchronous generators[J]. IEEE Transactions on Industrial Electronics, 2011, 58(4): 1259-1267. [3] 张玉治, 张辉, 贺大为, 等. 具有同步发电机特性的微电网逆变器控制[J]. 电工技术学报, 2014, 29(7): 261-268. Zhang Yuzhi, Zhang Hui, He Dawei, et al.Control strategy of micro grid converters with synchronous generator characteristic[J]. Transactions of China Electrotechnical Society, 2014, 29(7): 261-268. [4] 孟建辉, 彭嘉琳, 王毅, 等. 多约束下光储系统的灵活虚拟惯性控制方法[J]. 电工技术学报, 2019, 34(14): 3046-3058. Meng Jianhui, Peng Jialin, Wang Yi, et al.Multi- constrained flexible virtual inertial control method for photovoltaic energy storage system[J]. Transa- ctions of China Electrotechnical Society, 2019, 34(14): 3046-3058. [5] Zhong Qingchang, Ma Zhenyu, Ming Wenlong, et al.Grid-friendly wind power systems based on the synchronverter technology[J]. Energy Conversion and Management, 2015, 8(9): 719-726. [6] Aouini R, Marinescu B, Kilani K B, et al.Synch- ronverter-based emulation and control of HVDC transmission[J]. IEEE Transactions on Power Systems, 2016, 31(1): 278-286. [7] 钟庆昌. 虚拟同步机与自主电力系统[J]. 中国电机工程学报, 2017, 37(2): 336-348. Zhong Qingchang.Virtual synchronous machines and autonomous power systems[J]. Proceedings of the CSEE, 2017, 37(2): 336-348. [8] Zhong Qingchang, Ma Zhenyu, Nguyen P L.PWM- controlled rectifiers without the need of an extra synchronisation unit[C]//IECON 2012-38th Annual Conference on IEEE Industrial Electronics Society, Montreal, QC, Canada, 2012: 691-695. [9] 胡文强, 吴在军, 窦晓波, 等. 负荷虚拟同步机及其低电压故障穿越控制[J]. 电力系统自动化, 2018, 43(9): 100-107. Hu Wenqiang, Wu Zaijun, Dou Xiaobo, et al.Load virtual synchronous machine and its low voltage ride-through control[J]. Automation of Electric Power Systems, 2018, 43(9): 100-107. [10] 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. [11] 刘其辉, 逯胜建. 参与微电网调频的电动汽车虚拟同步机充放电控制策略[J]. 电力系统自动化, 2018, 42(9): 171-179. Liu Qihui, Lu Shengjian.Charging and discharging control strategy based on virtual synchronous machine for electrical vehichlesparticipating in frequency regulation of microgrid[J]. Automation of Electric Power Systems, 2018, 42(9): 171-179. [12] 高丙团, 夏超鹏, 张磊, 等. 基于虚拟同步电机技术的VSC-HVDC整流侧建模及参数设计[J]. 中国电机工程学报, 2017, 37(2): 534-543. Gao Bingtuan, Xia Chaopeng, Zhang Lei, et al.Modeling and parameters design for rectifier side of VSC-HVDC based on virtual synchronous machine technology[J]. Proceedings of the CSEE, 2017, 37(2): 534-543. [13] Fang Jingyang, Li Hongchang, Tang Yi, et al.Distri- buted power system virtual inertia implemented by grid-connected power converters[J]. IEEE Transactions on Power Electronics, 2018, 33(10): 8488-8499. [14] Fang Jingyang, Lin Pengfeng, Li Hongchang, et al.An improved virtual inertia control for three-phase voltage source converters connected to a weak grid[J]. IEEE Transactions on Power Electronics, 2019, 34(9): 8660-8670. [15] Liserre M, Teodorescu R, Blaabjerg F.Stability of photovoltaic and wind turbine grid-connected inverters for a large set of grid impedance values[J]. IEEE Transa- ctions on Power Electronics, 2006, 21(1): 263-272. [16] 黄云辉, 宋泽凡, 唐金瑞, 等. 连接弱电网的并网变换器直流电压时间尺度稳定器的设计与分析[J]. 电工技术学报, 2018, 33(增刊1): 185-192. Huang Yunhui, Song Zefan, Tang Jinrui, et al.Design and analysis of DC-link voltage stabilizer for voltage source converter as connected to weak grid[J]. Transactions of China Electrotechnical Society, 2018, 33(S1): 185-192. [17] 谢志为, 陈燕东, 伍文华, 等. 弱电网下多逆变器并网系统的全局高频振荡抑制方法[J]. 电工技术学报, 2020, 35(4): 885-895. Xie Zhiwei, Chen Yandong, Wu Wenhua, et al.A global high-frequency oscillation suppression method for multi-inverter grid-connected system in weak grid[J]. Transactions of China Electrotechnical Society, 2020, 35(4): 885-895. [18] 张学广, 夏丹妮, 陈文佳, 等. 三相并网变流器弱电网下频率耦合抑制控制方法[J]. 电工技术学报, 2019, 34(12): 4559-4571. Zhang Xueguang, Xia Danni, Chen Wenjia, et al.Frequency coupling suppression control method for three-phase grid-connected converter under weak grid[J]. Transactions of China Electrotechnical Society, 2019, 34(12): 4559-4571. [19] Wen Bo, Boroyevich D, Burgos R, et al.Small-signal stability analysis of three-phase AC systems in the presence of constant power loads based on measured d-q frame impedances[J]. IEEE Transactions on Power Electronics, 2015, 30(10): 5952-5963. [20] Wen Bo, Boroyevich D, Mattavelli P, et al.Impedance- based analysis of grid-synchronization stability for three-phase paralleled converters[J]. IEEE Transa- ctions on Power Electronics, 2016, 31(1): 26-38. [21] Lu Dapeng, Wang Xiongfei, Blaabjerg F.Impedance- based analysis of DC-link voltage dynamics in voltage-source converters[J]. IEEE Transactions on Power Electronics, 2019, 34(4): 3973-3985. [22] Li Chi, Burgos R, Wen Bo, et al.Analysis of STATCOM small-signal impedance in the synch- ronous D-Q frame[J]. IEEE Journal of Emerging and Selected Topics in Power Electronics, 2020, 8(2): 1894-1910. [23] Sun Jian.Small-signal methods for AC distributed power systems: a review[J]. IEEE Transactions on Power Electronics, 2009, 24(11): 2545-2554. [24] Cespedes M, Sun Jian.Impedance modeling and analysis of grid-connected voltage-source converters[J]. IEEE Transactions on Power Electronics, 2014, 29(3): 1254-1261. [25] Liu Hanchao, Sun Jian.Voltage stability and control of offshore wind farms with AC collection and HVDC transmission[J]. IEEE Journal of Emerging and Selected Topics in Power Electronics, 2014, 2(4): 1181-1189. [26] 张明远, 肖仕武, 田恬, 等. 基于阻抗灵敏度的直驱风电场并网次同步振荡影响因素及参数调整分析[J]. 电网技术, 2018, 42(9): 2768-2777. Zhang Mingyuan, Xiao Shiwu, Tian Tian, et al.Analysis of SSO influencing factors and parameter adjustment for grid-connected full-converter wind farm based on impedance sensitivity[J]. Power System Technology, 2018, 42(9): 2768-2777. [27] 刘津铭, 陈燕东, 伍文华, 等. 孤岛微电网序阻抗建模与高频振荡抑制[J]. 电工技术学报, 2020, 35(7): 1538-1552. Liu Jinming, Chen Yandong, Wu Wenhua, et al.Sequence impedance modeling and high-frequency oscillation suppression method for island micro- grid[J]. Transactions of China Electrotechnical Society, 2020, 35(7): 1538-1552. [28] 伍文华, 陈燕东, 周乐明, 等. 虚拟同步发电机接入弱电网的序阻抗建模与稳定性分析[J]. 中国电机工程学报, 2019, 39(6): 1560-1571. Wu Wenhua, Chen Yandong, Zhou Leming, et al.Sequence impedance modeling and stability analysis for virtual synchronous generator connected to the weak grid[J]. Proceedings of the CSEE, 2019, 39(6): 1560-1571. [29] 伍文华, 周乐明, 陈燕东, 等. 序阻抗视角下虚拟同步发电机与传统并网逆变器的稳定性对比分析[J]. 中国电机工程学报, 2019, 39(5): 1411-1420. Wu Wenhua, Zhou Leming, Chen Yandong, et al.Stability comparison and analysis between the virtual synchronous generator and the traditional grid- connected inverter in the view of sequence impedance[J]. Proceedings of the CSEE, 2019, 39(5): 1411-1420. [30] Wang Xiongfei, Blaabjerg F, Harmonic stability in power electronic-based power systems: concept, modeling, and analysis[J]. IEEE Transactions on Smart Grid, 2019, 10(3): 2858-2870. [31] Rygg A, Molinas M, Zhang Chen, et al.A modified sequence-domain impedance definition and its equi- valence 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] Rygg A, Molinas M, Zhang Chen, et al.On the equivalence and impact on stability of impedance modelling of power electronic converters in different domains[J]. IEEE Journal of Emerging and Selected Topics in Power Electronics, 2017, 5(4): 1444-1454. [33] Wang Xiongfei, Harnefors L, Blaabjerg F.A unified impedance model of grid-connected voltage-source converters[J]. IEEE Transactions on Power Electro- nics, 2018, 33(2): 1775-1787.
2021, Vol. 36 
