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| Analysis of Static Var Generator Considering the Impacts of Internal Dynamics and Frequency Coupling |
| Li Longcan1, Xiong Xiaoling1, Luo Bochen1, Zhao Chengyong1, Xu Ying2, Lei Tianxiang2 |
1. School of Electrical and Electronic Engineering North China Electric Power University Beijing 102206 China;
2. State Grid Economic and Technological Research Institute Co. Ltd Beijing 102209 China |
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Abstract Due to its compensation capabilities and fast dynamic response times, the cascaded H-bridge static var generator (SVG) has become widely adopted for enhancing power quality and providing reactive power in modern power systems. However, as a power electronic device predominantly governed by control-driven dynamics, the SVG faces the risk of oscillations. In addition, the mechanisms of wideband oscillations in SVG systems remain insufficiently understood, and effective stability enhancement techniques are lacking.
This paper analyzes the cascaded H-bridge SVG's nonlinear and strongly coupled internal dynamic characteristics. Focusing on the low-frequency range below the switching frequency, a harmonic state-space (HSS) complex vector impedance model is developed, incorporating the influence of multiple control loops. A detailed time-domain model is constructed to simulate the system's behavior, and frequency scanning is conducted using Matlab/Simulink. Furthermore, considering the system's frequency coupling relationships, the dynamic interactions of internal currents, output voltages, and three-phase capacitor voltages and their coupling grid impedance are examined. Accordingly, an equivalent single-input single-output impedance model is constructed. A stability analysis of the SVG is performed to evaluate the impact of various control loops and their associated parameters on system stability.
The phase-locked loop (PLL) is critical in determining system stability. Consequently, a quantitative analysis of the PLL parameters is conducted for parameter design and optimization. In contrast, the inter-phase voltage balancing loop has a minor influence on system stability. This paper proposes a voltage feedforward impedance reshaping strategy to mitigate the stability challenges associated with SVG grid integration. This approach targets the oscillations introduced by the dominant control loop (the PLL), which can offset its impact. However, since this method involves high-order integration, it is prone to causing system instability. Therefore, an optimized control strategy is proposed, effectively reducing the negative resistance region caused by the PLL, thereby enhancing the overall stability of the grid-connected system. A hardware-in-the-loop experiment is implemented using the RT-LAB platform. The experimental results verify the effectiveness of the proposed methods in improving system stability.
The key conclusions of this study are as follows. (1) The PLL and its control parameters significantly influence the system's oscillation risk based on the developed HSS impedance model for multi-frequency coupling in the cascaded H-bridge SVG. In contrast, the inter-phase voltage balancing loop and its control parameters exhibit a negligible impact. (2) The design of the PLL bandwidth needs to consider two critical factors: a considerable PLL bandwidth that reduces stability margins and a PLL bandwidth that aligns with the global voltage balancing loop bandwidth. As a result, additional oscillations from coupling are introduced. (3) A voltage feedforward-based impedance-shaping control strategy is proposed. This strategy mitigates the negative resistance region caused by the PLL, significantly improving the stability of the SVG system. This paper provides measures for the design and optimization of SVG systems.
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Received: 29 November 2024
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[1] 王兆安, 杨君, 刘进军, 等. 谐波抑制和无功功率补偿[M]. 2版. 北京: 机械工业出版社, 2006.
[2] 张旸, 沈梦娇, 陈新, 等. 基于双谐波线性化的级联H桥静止无功发生装置序阻抗建模与分析[J]. 电工技术学报, 2019, 34(20): 4334-4346.
Zhang Yang, Shen Mengjiao, Chen Xin, et al.Sequence impedance modeling and analysis of cascaded H-bridge static var generator based on double-harmonic linearization[J]. Transactions of China Electrotechnical Society, 2019, 34(20): 4334-4346.
[3] 陈鸿琳, 熊馨瑶, 余浩, 等. SVG对海上风电交流并网系统稳定性影响分析[J]. 电力系统保护与控制, 2022, 50(19): 119-129.
Chen Honglin, Xiong Xinyao, Yu Hao, et al.Analysis on the influence of an SVG on the stability of AC grid-connected offshore wind farms[J]. Power System Protection and Control, 2022, 50(19): 119-129.
[4] 杨铭, 曹武, 赵剑锋, 等. 受控电压/电流源型变流器混合多机暂态电压支撑策略[J]. 电工技术学报, 2023, 38(19): 5207-5223, 5240.
Yang Ming, Cao Wu, Zhao Jianfeng, et al.Transient voltage support strategy for hybrid multi-converter of controlled voltage/current source converter[J]. Transa- ctions of China Electrotechnical Society, 2023, 38(19): 5207-5223, 5240.
[5] Akagi H.Classification, terminology, and application of the modular multilevel cascade converter (MMCC)[J]. IEEE Transactions on Power Electronics, 2011, 26(11): 3119-3130.
[6] 单庆晓, 李永东, 潘孟春. 级联型逆变器的新进展[J]. 电工技术学报, 2004, 19(2): 1-9.
Shan Qingxiao, Li Yongdong, Pan Mengchun.A review on cascaded inverter[J]. Transactions of China Electrotechnical Society, 2004, 19(2): 1-9.
[7] 熊小玲, 罗博晨, 刘京波, 等. 计及SVG的双馈风电场高频阻抗建模及振荡分析[J]. 电网技术, 2023, 47(7): 2905-2917.
Xiong Xiaoling, Luo Bochen, Liu Jingbo, et al.High frequency impedance modeling and oscillation analysis of DFIG-based station considering SVG[J]. Power System Technology, 2023, 47(7): 2905-2917.
[8] 张前进, 周林, 李海啸, 等. 考虑SVG补偿装置的大型光伏并网系统振荡分析与抑制[J]. 中国电机工程学报, 2019, 39(9): 2636-2644.
Zhang Qianjin, Zhou Lin, Li Haixiao, et al.Oscillation analysis and suppression of large-scale grid-connected photovoltaic system considering SVG equipment[J]. Proceedings of the CSEE, 2019, 39(9): 2636-2644.
[9] 于雁南, 杨荣峰, 严继池, 等. 级联H桥静止无功发生器的多变量自抗扰解耦控制[J]. 中国电机工程学报, 2016, 36(8): 2233-2241.
Yu Yannan, Yang Rongfeng, Yan Jichi, et al.Multiple-input multiple-output decoupling control schemes of static var generator with cascaded H- bridge based on active disturbance rejection control[J]. Proceedings of the CSEE, 2016, 36(8): 2233-2241.
[10] Bergna-Diaz G, Freytes J, Guillaud X, et al.Generalized voltage-based state-space modeling of modular multilevel converters with constant equili- brium in steady state[J]. IEEE Journal of Emerging and Selected Topics in Power Electronics, 2018, 6(2): 707-725.
[11] 年珩, 朱茂玮, 徐韵扬, 等. 基于谐波传递矩阵的MMC换流站频率耦合特性建模与分析[J]. 电力系统自动化, 2020, 44(6): 75-83.
Nian Heng, Zhu Maowei, Xu Yunyang, et al.Modeling and analysis of frequency coupling characteristic for MMC station based on harmonic transfer matrices[J]. Automation of Electric Power Systems, 2020, 44(6): 75-83.
[12] 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 impe- dance[J]. Transactions of China Electrotechnical Society, 2023, 38(15): 4130-4146.
[13] 高本锋, 沈雨思, 宋瑞华, 等. 虚拟同步机控制模块化多电平变流器阻抗建模及次/超同步振荡稳定性分析[J]. 电工技术学报, 2025, 40(2): 559-573.
Gao Benfeng, Shen Yusi, Song Ruihua, et al.Impedance modeling and sub/super synchronous oscillation stability analysis of modular multilevel converter under virtual synchronous generator control[J]. Transactions of China Electrotechnical Society, 2025, 40(2): 559-573.
[14] 宗皓翔, 张琛, 吕敬, 等. MMC多入多出阻抗及其在不对称小扰动稳定分析中的应用[J]. 中国电机工程学报, 2022, 42(15): 5649-5664.
Zong Haoxiang, Zhang Chen, Lü Jing, et al.MMC MIMO impedance and its application in the asymmetric small-signal stability analysis[J]. Pro- ceedings of the CSEE, 2022, 42(15): 5649-5664.
[15] Zhang Chen, Molinas M, Føyen S, et al.Harmonic- domain SISO equivalent impedance modeling and stability analysis of a single-phase grid-connected VSC[J]. IEEE Transactions on Power Electronics, 2020, 35(9): 9770-9783.
[16] Wu Heng, Wang Xiongfei, Kocewiak Ł H.Impedance- based stability analysis of voltage-controlled MMCs feeding linear AC systems[J]. IEEE Journal of Emerging and Selected Topics in Power Electronics, 2020, 8(4): 4060-4074.
[17] Wu Heng, Wang Xiongfei.Dynamic impact of zero-sequence circulating current on modular multilevel converters: complex-valued AC impedance modeling and analysis[J]. IEEE Journal of Emerging and Selected Topics in Power Electronics, 2020, 8(2): 1947-1963.
[18] 王杨, 夏菲, 田旭, 等. 基于谐波状态空间的高压直流输电系统SISO阻抗建模及稳定性分析[J]. 中国电机工程学报, 2024, 44(5): 1985-1999.
Wang Yang, Xia Fei, Tian Xu, et al.SISO impedance modeling and stability analysis of HVDC system based on harmonic state space[J]. Proceedings of the CSEE, 2024, 44(5): 1985-1999.
[19] 张旸, 孙龙庭, 陈新, 等. 集成静止无功发生装置的直驱风场序阻抗网络模型与稳定性分析[J]. 中国电机工程学报, 2020, 40(9): 2877-2891.
Zhang Yang, Sun Longting, Chen Xin, et al.Sequence impedance network model and stability analysis for direct-drive wind farm with static var generator[J]. Proceedings of the CSEE, 2020, 40(9): 2877-2891.
[20] 任必兴, 杜文娟, 王海风. 静止同步补偿器与直驱永磁风机的次同步控制交互研究[J]. 电工技术学报, 2018, 33(24): 5884-5896.
Ren Bixing, Du Wenjuan, Wang Haifeng.Analysis on sub-synchronous control interaction between static synchronous compensator and permanent magnet synchronous generator[J]. Transactions of China Electrotechnical Society, 2018, 33(24): 5884-5896.
[21] 周佩朋, 李光范, 宋瑞华, 等. 直驱风机与静止无功发生器的次同步振荡特性及交互作用分析[J]. 中国电机工程学报, 2018, 38(15): 4369-4378, 4637.
Zhou Peipeng, Li Guangfan, Song Ruihua, et al.Subsynchronous oscillation characteristics and intera- ctions of direct drive permanent magnet synchronous generator and static var generator[J]. Proceedings of the CSEE, 2018, 38(15): 4369-4378, 4637.
[22] 胡鹏, 艾欣, 肖仕武, 等. 静止无功发生器序阻抗建模及对次同步振荡影响因素的分析[J]. 电工技术学报, 2020, 35(17): 3703-3713.
Hu Peng, Ai Xin, Xiao Shiwu, et al.Sequence impedance of static var generator and\r analysis of influencing factors on subsynchronous oscillation[J]. Transactions of China Electrotechnical Society, 2020, 35(17): 3703-3713.
[23] Zhang Yang, Yang Yongheng, Chen Xin, et al.Intelligent parameter design-based impedance opti- mization of STATCOM to mitigate resonance in wind farms[J]. IEEE Journal of Emerging and Selected Topics in Power Electronics, 2021, 9(3): 3201-3215.
[24] 邢纪奎, 袁辉, 代江, 等. 抑制新能源次/超同步振荡的SVG鲁棒自适应控制参数设计方法[J]. 电力自动化设备, 2024, 44(8): 160-167.
Xing Jikui, Yuan Hui, Dai Jiang, et al.Design method of robust adaptive control parameter of SVG to suppress sub/sup-synchronous oscillation caused by new energy[J]. Electric Power Automation Equipment, 2024, 44(8): 160-167.
[25] 陈继开, 郝鑫, 常旗峰, 等. 考虑SVG控制模式的风电场系统中频谐振分析与抑制[J]. 电力自动化设备, 2023, 43(9): 39-46.
Chen Jikai, Hao Xin, Chang Qifeng, et al.Analysis and suppression of medium frequency resonance of wind farm system considering SVG control modes[J]. Electric Power Automation Equipment, 2023, 43(9): 39-46.
[26] 张东辉, 陈新, 杨舒婷, 等. 含静止无功补偿装置的光伏电站高频谐振分析及抑制策略研究[J]. 中国电机工程学报, 2023, 43(24): 9580-9594.
Zhang Donghui, Chen Xin, Yang Shuting, et al.Analysis of high-frequency resonance and suppression strategy of photovoltaic power plant with static reactive power compensation device[J]. Proceedings of the CSEE, 2023, 43(24): 9580-9594.
[27] Zhang Yang, Chen Xin, Sun Jian.Sequence impe- dance modeling and analysis of MMC in single-star configuration[J]. IEEE Transactions on Power Elec- tronics, 2020, 35(1): 334-346.
[28] Akagi H, Inoue S, Yoshii T.Control and performance of a transformerless cascade PWM STATCOM with star configuration[J]. IEEE Transactions on Industry Applications, 2007, 43(4): 1041-1049.
[29] Sun Jian, Liu Hanchao.Sequence impedance modeling of modular multilevel converters[J]. IEEE Journal of Emerging and Selected Topics in Power Electronics, 2017, 5(4): 1427-1443.
[30] Wen Bo, Boroyevich D, Burgos R, et al.Analysis of D-Q small-signal impedance of grid-tied inverters[J]. IEEE Transactions on Power Electronics, 2016, 31(1): 675-687.
[31] 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.
[32] 王震, 程鹏, 贾利民. 基于对称控制的三相并网变流器单输入单输出阻抗建模与分析[J]. 电工技术学报, 2024, 39(6): 1777-1791.
Wang Zhen, Cheng Peng, Jia Limin.Single-input single-output impedance modeling and analysis of three-phase grid-tied converter based on symmetric control[J]. Transactions of China Electrotechnical Society, 2024, 39(6): 1777-1791. |
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2025, Vol. 40 
