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| A Sub-Synchronous Oscillation Suppression Strategy for the Grid-Forming Converter Based on Grid-Connected Current Feedback |
| Zhang Qi1, Liu Junliang1, Chen Bing1,2, Du Xiong1, Zou Xiaoming2,3 |
1. State Key Laboratory of Power Transmission Equipment Technology Chongqing University Chongqing 400044 China;
2. Jiangsu Electric Power Test Research Institute Co. Ltd Nanjing 211103 China;
3. State Grid Jiangsu Electric Power Co. Ltd Research Institute Nanjing 211103 China |
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Abstract Similar to synchronous generators, the grid-forming converter mostly uses power synchronization or inertial synchronization control strategies, which can provide inertia and damping support to the grid. However, the similar external characteristics of the grid-forming converter and synchronous generator result in its susceptibility to sub-synchronous oscillations when connected to the grid through aseries capacitor compensation line. In view of this, this paper carries out a comprehensive research work on the stability analysis and sub-synchronous oscillation suppression strategy for the grid-forming converter connected to the grid via a series capacitor compensation line.
Firstly, the self-impedance and the accompanying impedance models of the grid-forming converter are established by using the complex variable representation method. The self-impedance and the accompanying impedance are verified using the frequency scanning method, and the scanning results were consistent with the analytical model, verifying the correctness of both. The established the self-impedance and the accompanying impedance models can accurately explain and characterize the single-frequency input and dual-frequency output of the grid-forming converter. Afterwards, the equivalent impedance model of the system with single input and single output of the grid-forming converter is derived, taking into account the frequency coupling effect and the influence of the series complementary lines.
Secondly, the stability of the grid-connected system at different series compensation degrees is analysed by using the Nyquist stability criterion based on an equivalent impedance model that accounts for thefrequency coupling effect. It is found that the larger series compensation degree is, the worse the system stability is. In addition, the impedance stability analysis taking into account the frequency coupling effect is more accurate under certain operating conditions.
Then, a current feedback-based impedance reshaping strategy is proposed for the phenomenon of sub-synchronous oscillations generated by the interaction between the grid-forming converter and the series-complementary line. The strategy is that the grid-connected current passes through the notch filter and the feedback coefficient as part of the modulation wave output to achieve system impedance reshaping. The function of the trap filter is to maintain the fundamental frequency output impedance and avoid the working point offset of the converter. And the current feedback coefficient was introduced into the equivalent impedance model, the feedback coefficient-frequency binary equivalent impedance model was established, and the amplitude-phase contour stability criterion was used to parameterize the current feedback coefficients. It is found that the larger the feedback coefficient k is, the larger the phase margin of the system is, and the more stable the system is. In addition, after the system is shaped by impedance, the phase-frequency curve moves down as a whole, especially in the frequency band below 50 Hz, the phase-frequency curve moves down greatly, resulting in the phase difference at the resonance point less than 180°, and the oscillation is suppressed.
Finally, the grid-connected system model of the grid-forming converter via series-complementary line is built through simulation and experiment, and the impedance remodeling control strategy is implemented on the damping controller to verify the correctness of the theoretical analysis as well as the parameter design. This study draws the following conclusions. (1) The interaction between the grid-forming converter and the series compensation line is easy to cause sub-synchronous oscillation, and the greater the series compensation degree, the higher the oscillation risk. In addition, under certain operating conditions, impedance analyses that take into account frequency coupling effect are more accurate and their influence cannot be ignored. (2) The amplitude-phase contour plot can be used to determine intuitively the influence of the feedback coefficient k on the operating characteristics of the system and to derive the range of values of the feedback coefficient k parameter when the system is in a stable or unstable state.
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Received: 03 August 2024
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[1] 余果, 吴军, 夏热, 等. 构网型变流器技术的发展现状与趋势研究[J]. 综合智慧能源, 2022, 44(9): 65-70.
Yu Guo, Wu Jun, Xia Re, et al.Study on the status quo and development trend of grid-forming converter technology[J]. Integrated Intelligent Energy, 2022, 44(9): 65-70.
[2] Huang Linbin, Xin Huanhai, Li Zhiyi, et al.Grid-synchronization stability analysis and loop shaping for PLL-based power converters with different reactive power control[J]. IEEE Transactions on Smart Grid, 2020, 11(1): 501-516.
[3] 陈露洁, 徐式蕴, 孙华东, 等. 高比例电力电子电力系统宽频带振荡研究综述[J]. 中国电机工程学报, 2021, 41(7): 2297-2310.
Chen Lujie, Xu Shiyun, Sun Huadong, et al.A survey on wide-frequency oscillation for power systems with high penetration of power electronics[J]. Proceedings of the CSEE, 2021, 41(7): 2297-2310.
[4] Liu Qing, Caldognetto T, Buso S.Review and comparison of grid-tied inverter controllers in microgrids[J]. IEEE Transactions on Power Electronics, 2020, 35(7): 7624-7639.
[5] 许诘翊, 刘威, 刘树, 等. 电力系统变流器构网控制技术的现状与发展趋势[J]. 电网技术, 2022, 46(9): 3586-3595.
Xu Jieyi, Liu Wei, Liu Shu, et al.Current state and development trends of power system converter grid-forming control technology[J]. Power System Techno-logy, 2022, 46(9): 3586-3595.
[6] 曹炜, 钦焕乘, 陆建忠, 等. 新型电力系统下虚拟同步机的定位和应用前景展望[J]. 电力系统自动化, 2023, 47(4): 190-207.
Cao Wei, Qin Huancheng, Lu Jianzhong, et al.Orientation and application prospect of virtual synchronous generator in new power system[J]. Automation of Electric Power Systems, 2023, 47(4): 190-207.
[7] Mohandes B, El Moursi M S, Hatziargyriou N, et al. A review of power system flexibility with high penetration of renewables[J]. IEEE Transactions on Power Systems, 2019, 34(4): 3140-3155.
[8] Peng Qiao, Jiang Qin, Yang Yongheng, et al.On the stability of power electronics-dominated systems: challenges and potential solutions[J]. IEEE Transactions on Industry Applications, 2019, 55(6): 7657-7670.
[9] 詹长江, 吴恒, 王雄飞, 等. 构网型变流器稳定性研究综述[J]. 中国电机工程学报, 2023, 43(6): 2339-2359.
Zhan Changjiang, Wu Heng, Wang Xiongfei, et al.An overview of stability studies of grid-forming voltage source converters[J]. Proceedings of the CSEE, 2023, 43(6): 2339-2359.
[10] Zhao Fangzhou, Wang Xiongfei, Zhu Tianhua.Low-frequency passivity-based analysis and damping of power-synchronization controlled grid-forming inverter[J]. IEEE Journal of Emerging and Selected Topics in Power Electronics, 2023, 11(2): 1542-1554.
[11] 熊小玲, 李昕悦, 周琰, 等. 基于陷波器的构网型换流器同步频率谐振抑制策略[J]. 电工技术学报, 2024, 39(12): 3827-3839.
Xiong Xiaoling, Li Xinyue, Zhou Yan, et al.Synchronous frequency resonance suppression of grid-forming converter based on notch filter[J]. Transactions of China Electrotechnical Society, 2024, 39(12): 3827-3839.
[12] 秦世耀, 齐琛, 李少林, 等. 电压源型构网风电机组研究现状及展望[J]. 中国电机工程学报, 2023, 43(4): 1314-1334.
Qin Shiyao, Qi Chen, Li Shaolin, et al.Review of the voltage-source grid forming wind turbine[J]. Proceedings of the CSEE, 2023, 43(4): 1314-1334.
[13] 潘子迅, 杨晓峰, 赵锐, 等. 不平衡电网下虚拟同步机的多模式协调策略[J]. 电工技术学报, 2023, 38(16): 4274-4285.
Pan Zixun, Yang Xiaofeng, Zhao Rui, et al.Multi-mode coordination control of virtual synchronous generator under unbalanced power grid[J]. Transactions of China Electrotechnical Society, 2023, 38(16): 4274-4285.
[14] 王祺, 张泽轲, 郭杰帅, 等. 新型电力系统主动构网机理与技术路径[J]. 中国电机工程学报, 2024, 44(2): 504-517.
Wang Qi, Zhang Zeke, Guo Jieshuai, et al.Mechanism and technical path of active grid-forming of new type power system[J]. Proceedings of the CSEE, 2024, 44(2): 504-517.
[15] Xu Haizhen, Yu Changzhou, Liu Chun, et al.An improved virtual inertia algorithm of virtual synchronous generator[J]. Journal of Modern Power Systems and Clean Energy, 2020, 8(2): 377-386.
[16] 杨伊茜, 陈杰, 万雨朦, 等. 电网电压前馈控制VSG的阻抗建模与并网稳定性分析[J]. 电力工程技术, 2021, 40(6): 52-61.
Yang Yiqian, Chen Jie, Wan Yumeng, et al.The impedance modelling and stability analysis of VSG with grid voltage feedforward control[J]. Electric Power Engineering Technology, 2021, 40(6): 52-61.
[17] Leon A E, Mauricio J M.Virtual synchronous generator for VSC-HVDC stations with DC voltage control[J]. IEEE Transactions on Power Systems, 2023, 38(1): 728-738.
[18] 高本锋, 邓鹏程, 孙大卫, 等. 基于匹配控制的构网型直驱风电场次同步振荡机理与特性研究[J]. 电工技术学报, 2024, 39(9): 2755-2770.
Gao Benfeng, Deng Pengcheng, Sun Dawei, et al.Mechanism and characteristics of subsynchronous oscillation of grid-forming direct-drive wind farm based on matching control[J]. Transactions of China Electrotechnical Society, 2024, 39(9): 2755-2770.
[19] 谢震, 杨曙昕, 代鹏程, 等. 构网型全功率风电机组网侧变流器耦合分析及抑制策略[J]. 电工技术学报, 2023, 38(14): 3745-3758, 3768.
Xie Zhen, Yang Shuxin, Dai Pengcheng, et al.Grid-side coupling analysis and suppression strategy of grid-forming full-power wind turbines[J]. Transactions of China Electrotechnical Society, 2023, 38(14): 3745-3758, 3768.
[20] Xu Yunyang, Nian Heng, Hu Bin, et al.Impedance modeling and stability analysis of VSG controlled type-IV wind turbine system[J]. IEEE Transactions on Energy Conversion, 2021, 36(4): 3438-3448.
[21] 殷桂梁, 董浩, 代亚超, 等. 光伏微网中虚拟同步发电机参数自适应控制策略[J]. 电网技术, 2020, 44(1): 192-199.
Yin Guiliang, Dong Hao, Dai Yachao, et al.Adaptive control strategy of VSG parameters in photovoltaic microgrid[J]. Power System Technology, 2020, 44(1): 192-199.
[22] Zhou Xinyi, Cheng Shu, Wu Xun, et al.Influence of photovoltaic power plants based on VSG technology on low frequency oscillation of multi-machine power systems[J]. IEEE Transactions on Power Delivery, 2022, 37(6): 5376-5384.
[23] 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): 1411-1421.
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): 1411-1421.
[24] 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.
[25] 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.
[26] Sun Jian, Li Mingjie, Zhang Zhigang, et al.Renewable energy transmission by HVDC across the continent: system challenges and opportunities[J]. CSEE Journal of Power and Energy Systems, 2017, 3(4): 353-364.
[27] 杜程茂, 杜雄, 苏婧媛, 等. 定子电流控制的双馈风机导纳建模与次同步振荡风险分析[J]. 电力系统自动化, 2023, 47(13): 159-167.
Du Chengmao, Du Xiong, Su Jingyuan, et al.Admittance modeling and subsynchronous oscillation risk analysis of DFIG-based wind turbine with stator current control[J]. Automation of Electric Power Systems, 2023, 47(13): 159-167.
[28] Wu Wenhua, Zhou Leming, Chen Yandong, et al.Sequence-impedance-based stability comparison between VSGs and traditional grid-connected inverters[J]. IEEE Transactions on Power Electronics, 2019, 34(1): 46-52.
[29] Li Gaoxiang, Chen Yandong, Luo An, et al.Analysis and mitigation of subsynchronous resonance in series-compensated grid-connected system controlled by a virtual synchronous generator[J]. IEEE Transactions on Power Electronics, 2020, 35(10): 11096-11107.
[30] 刘欣, 郭志博, 贾焦心, 等. 基于序阻抗的虚拟同步发电机并网稳定性分析及虚拟阻抗设计[J]. 电工技术学报, 2023, 38(15): 4130-4146.
Liu Xin, Guo Zhibo, Jia Jiaoxin, et al.Stability analysis and virtual impedance design of virtual synchronous machine based on sequence impedance[J]. Transactions of China Electrotechnical Society, 2023, 38(15): 4130-4146.
[31] 王国宁, 杜雄, 邹小明, 等. 用于三相并网逆变器稳定性分析的自导纳和伴随导纳建模[J]. 中国电机工程学报, 2017, 37(14): 3973-3981, 4275.
Wang Guoning, Du Xiong, Zou Xiaoming, et al.Self and accompanying admittance model for three-phase grid-tied inverter stability analysis[J]. Proceedings of the CSEE, 2017, 37(14): 3973-3981, 4275.
[32] Zou Xiaoming, Du Xiong, Tai Hengming.Two-variable admittance model for D-PMSG-based wind turbine and stability criterion based on magnitude and phase contour plot[J]. IEEE Transactions on Power Electronics, 2020, 35(2): 1484-1498. |
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2025, Vol. 40 
