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
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摘要
传统新能源并网逆变器接入弱电网易发生谐波振荡等交互稳定性问题。该文采用谐波线性化方法建立虚拟同步发电机的小信号序阻抗模型,对比分析虚拟同步发电机和传统并网逆变器的序阻抗特性。传统并网逆变器的序阻抗在中频段显容性且阻抗幅值较大;而虚拟同步发电机的序阻抗基本呈感性且阻抗幅值较小,与电网的阻抗特性基本一致。基于序阻抗模型和奈奎斯特稳定判据分析电网强弱、逆变器并网台数和锁相环带宽对虚拟同步发电机和传统并网逆变器并网系统稳定性的影响。稳定性分析结果表明,在弱电网下或者高渗透率新能源发电下,传统并网逆变器容易失稳,而VSG并网系统依旧可以稳定运行且无锁相环的约束。因此,从系统稳定性的角度来说,VSG比传统并网逆变器更适合应用于弱电网下或者高渗透率新能源发电中。最后,通过实验验证该文分析的正确性。
Traditional renewable energy grid-connected inverters are vulnerable to harmonic oscillations and other interaction stability problems when they are connected to weak grids. Firstly, the small-signal sequence impedance model of the virtual synchronous generator(VSG) was built and the sequence impedance characteristics of the VSG and the traditional grid-connected inverter were compared and analyzed. The sequence impedance of the traditional grid-connected inverter is mainly capacitive in the middle-frequency area and the impedance amplitude is quite high. However, the sequence impedance of the VSG is generally inductive and the impedance amplitude is quite low,which is consistent with the impedance characteristics of the grid. Then, based on the sequence impedance model and the Nyquist stability criterion, the influence of weakness the grid,the parallel number of inverters and phase locked loop(PLL)bandwidth on the stability of the VSG and the traditional grid-connected inverter system was analyzed. The stability analysis results show that the traditional grid-connected inverter loses stability easily while the VSG still works well and with no PLL restriction under the weak grid condition or with large number of inverters connected to the grid. Therefore,the VSG is more suitable to achieve high penetration renewable energy generation in the weak grid than the traditionalgrid-connected inverter from the point of view of system stability. Finally, experiment results validated the analysis.
Traditional renewable energy grid-connected inverters are vulnerable to harmonic oscillations and other interaction stability problems when they are connected to weak grids. Firstly, the small-signal sequence impedance model of the virtual synchronous generator(VSG) was built and the sequence impedance characteristics of the VSG and the traditional grid-connected inverter were compared and analyzed. The sequence impedance of the traditional grid-connected inverter is mainly capacitive in the middle-frequency area and the impedance amplitude is quite high. However, the sequence impedance of the VSG is generally inductive and the impedance amplitude is quite low,which is consistent with the impedance characteristics of the grid. Then, based on the sequence impedance model and the Nyquist stability criterion, the influence of weakness the grid,the parallel number of inverters and phase locked loop(PLL)bandwidth on the stability of the VSG and the traditional grid-connected inverter system was analyzed. The stability analysis results show that the traditional grid-connected inverter loses stability easily while the VSG still works well and with no PLL restriction under the weak grid condition or with large number of inverters connected to the grid. Therefore,the VSG is more suitable to achieve high penetration renewable energy generation in the weak grid than the traditionalgrid-connected inverter from the point of view of system stability. Finally, experiment results validated the analysis.
引文
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[23]Vieto I,Sun Jian.Impedance modeling of doubly-fed induction generators[C]//Proceedings of the 17th European Conference on Power Electronics and Applications.Geneva,Switzerland:IEEE,2015:1-10.
[24]苏剑,刘海涛,吴鸣,等.分布式电源与微电网并网技术[M].北京:中国电力出版社,2015:86-92.Su Jian,Liu Haitao,Wu Ming,et al.Distributed generation and micro-grid grid-connected technologies[M].Beijing:China Electric Power Press,2015:86-92(in Chinese).
[25]伍文华,陈燕东,罗安,等.海岛VSC-HVDC输电系统直流阻抗建模、振荡分析与抑制方法[J].中国电机工程学报,2018,38(15):4359-4368.Wu Wenhua,Chen Yandong,Luo An,et al.DC impedance modeling,oscillation analysis and suppression method for VSC-HVDC system in the field of islands power supply[J].Proceedings of the CSEE,2018,38(15):4359-4368(in Chinese).
[2]陈燕东,罗安,陈智勇,等.一种快速无功支撑的阻容性逆变器并联控制方法[J].中国电机工程学报,2014,34(30):5296-5305.Chen Yandong,Luo An,Chen Zhiyong,et al.A rapid reactive power control method for parallel inverters using resistive-capacitive output impedance[J].Proceedings of the CSEE,2014,34(30):5296-5305(in Chinese).
[3]Wen Bo,Dong Dong,Boroyevich D,et al.Impedancebased analysis of grid-synchronization stability for three-phase paralleled converters[J].IEEE Transactions on Power Electronics,2016,31(1):26-38.
[4]谢小荣,刘华坤,贺静波,等.直驱风机风电场与交流电网相互作用引发次同步振荡的机理与特性分析[J].中国电机工程学报,2016,36(9):2366-2372.Xie Xiaorong,Liu Huakun,He Jingbo,et al.Mechanism and characteristics of subsynchronousoscillation caused by the interaction between full-converter wind turbines and AC systems[J].Proceedings of the CSEE,2016,36(9):2366-2372(in Chinese).
[5]Wen Bo,Boroyevich D,Burgos R,et al.Analysis of D-Qsmall-signal impedanceof grid-tied inverters[J].IEEETransactions on Power Electronics,2016,31(1):675-687.
[6]吕志鹏,盛万兴,钟庆昌,等.虚拟同步发电机及其在微电网中的应用[J].中国电机工程学报,2014,34(16):2591-2603.LüZhipeng,Sheng Wanxing,Zhong Qingchang,et al.Virtual synchronous generator and its applications in micro-grid[J].Proceedings of the CSEE,2014,34(16):2591-2603(in Chinese).
[7]吕志鹏,盛万兴,刘海涛,等.虚拟同步机技术在电力系统中的应用与挑战[J].中国电机工程学报,2017,37(2):349-359.LüZhipeng,Sheng Wanxing,Liu Haitao,et al.Application and challenge of virtual synchronous machine technology in power system[J].Proceedings of the CSEE,2017,37(2):349-359(in Chinese).
[8]Chen Yong,Hesse R,Turschner D,et al.Improving the grid power quality using virtual synchronous machines[C]//Proceedings of the 2011 International Conference on Power Engineering,Energy and Electrical Drives.Malaga,Spain:IEEE,2011.
[9]Gao Fang,Iravani M R.A control strategy for a distributed generation unit in grid-connected and autonomous modes of operation[J].IEEE Transactions on Power Delivery,2008,23(2):850-859.
[10]Zhong Qingchang,Weiss G.Synchronverters:inverters that mimic synchronous generators[J].IEEE Transactions on Industrial Electronics,2011,58(4):1259-1267.
[11]伍文华,陈燕东,罗安,等.一种直流微网双向并网变换器虚拟惯性控制策略[J].中国电机工程学报,2017,37(2):360-371.Wu Wenhua,Chen Yandong,Luo An,et al.A virtual inertia control strategy for bidirectional grid-connected converters in DC micro-grids[J].Proceedings of the CSEE,2017,37(2):360-371(in Chinese).
[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-HVDCbased on virtual synchronous machine technology[J].Proceedings of the CSEE,2017,37(2):534-543(in Chinese).
[13]Arani M F M,El-Saadany E F.Implementing virtual inertia in DFIG-based wind power generation[J].IEEETransactions on Power Systems,2013,28(2):1373-1384.
[14]Wu Heng,Ruan Xinbo,Yang Dongsheng,et al.Small-signal modeling and parameters designfor virtual synchronous generators[J].IEEE Transactions on Industrial Electronics,2016,63(7):4292-4303.
[15]Du Yan,Guerrero J M,Chang Liuchen,et al.Modeling,analysis,and design of a frequency-droop-based virtual synchronous generator for microgrid applications[C]//Proceedings of 2013 IEEEECCE Asia Downunder.Melbourne,VIC,Australia:IEEE,2013.
[16]Hu Changbin,Chen Kaiyu,Luo Shanna,et al.Small signal modeling and stability analysis of virtual synchronous generators[C]//Proceedings of the20th International Conference on Electrical Machines and Systems.Sydney,NSW,Australia:IEEE,2017.
[17]颜湘武,刘正男,张波,等.具有同步发电机特性的并联逆变器小信号稳定性分析[J].电网技术,2016,40(3):910-917.Yan Xiangwu,Liu Zhengnan,Zhang Bo,et al.Small-signal stability analysis of parallel inverters with synchronous generator characteristics[J].Power System Technology,2016,40(3):910-917(in Chinese).
[18]Cespedes M,Sun Jian.Impedance modeling and analysis of grid-connected voltage-source converters[J].IEEETransactions on Power Electronics,2014,29(3):1254-1261.
[19]Sun Jian.Impedance-based stability criterion for grid-connected inverters[J].IEEE Transactions on Power Electronics,2011,26(11):3075-3078.
[20]王赟程,陈新,张旸,等.三相并网逆变器锁相环频率特性分析及其稳定性研究[J].中国电机工程学报,2017,37(13):3843-3853.Wang Yuncheng,Chen Xin,Zhang Yang,et al.Frequency characteristics analysis and stability research of phase locked loop for three-phase grid-connected inverters[J].Proceedings of the CSEE,2017,37(13):3843-3853(in Chinese).
[21]Sun Jian,Liu Hanchao.Impedance modeling and analysis of modular multilevel converters[C]//Proceedings of the IEEE 17th Workshop on Control and Modeling for Power Electronics.Trondheim,Norway:IEEE,2016.
[22]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.
[23]Vieto I,Sun Jian.Impedance modeling of doubly-fed induction generators[C]//Proceedings of the 17th European Conference on Power Electronics and Applications.Geneva,Switzerland:IEEE,2015:1-10.
[24]苏剑,刘海涛,吴鸣,等.分布式电源与微电网并网技术[M].北京:中国电力出版社,2015:86-92.Su Jian,Liu Haitao,Wu Ming,et al.Distributed generation and micro-grid grid-connected technologies[M].Beijing:China Electric Power Press,2015:86-92(in Chinese).
[25]伍文华,陈燕东,罗安,等.海岛VSC-HVDC输电系统直流阻抗建模、振荡分析与抑制方法[J].中国电机工程学报,2018,38(15):4359-4368.Wu Wenhua,Chen Yandong,Luo An,et al.DC impedance modeling,oscillation analysis and suppression method for VSC-HVDC system in the field of islands power supply[J].Proceedings of the CSEE,2018,38(15):4359-4368(in Chinese).
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