计及无功电压环节的VSG虚拟转矩及振荡失稳机理分析
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摘要
通过模拟同步发电机的机电暂态过程,虚拟同步发电机(VSG)技术成为并网逆变器接入电网的一个颇具吸引力的方案。然而,VSG也存在功率振荡现象,相关机理的研究有待开展。文中借鉴传统电力系统中的转矩分析理论,建立了计及无功电压环节的VSG小信号模型,并结合振荡模态,重新定义了虚拟转矩系数。然后,通过分析该系数与稳定性之间的关系,从数学上证明虚拟阻尼转矩不足将导致VSG出现功率振荡失稳。之后,以鲁棒下垂控制的VSG为例,给出了虚拟转矩系数的计算方法,并在PSCAD/EMTDC和VSG实验平台验证了该结论的正确性。最后,从系统初始状态、线路参数及控制器参数等多个角度出发,讨论了VSG无功电压环节对虚拟转矩系数及系统小信号稳定性的影响,可为VSG控制器设计和系统小信号稳定性分析提供依据。
Virtual synchronous generator(VSG)has become an attractive scheme for connecting inverters with grids by simulating electromechanical transient process of synchronous generators.However,there also exists power oscillation problems in the VSG,and the related research on oscillation mechanism is needed.Based on the theory of torque analysis in the traditional power system,this paper establishes a small-signal model of VSG with reactive power-voltage controller.Combined with the oscillation mode,the virtual torque coefficient is redefined.Then the relationship between the virtual torque coefficient and VSG stability is analyzed.It is mathematically proved that the lack of virtual damping torque will lead to power oscillation instability of VSG.Taking the VSG with robust droop control as an example,the calculation method of virtual torque coefficient is given,and the conclusion is verified through PSCAD/EMTDC simulation and physical experiment.Finally,this paper discusses the effect of VSG with reactive power-voltage controller on the virtual torque coefficient and system smallsignal stability from different perspectives,such as the initial state of the system,line parameters and controller parameters.The research is beneficial to the VSG controller design and the system small-signal stability analysis.
Virtual synchronous generator(VSG)has become an attractive scheme for connecting inverters with grids by simulating electromechanical transient process of synchronous generators.However,there also exists power oscillation problems in the VSG,and the related research on oscillation mechanism is needed.Based on the theory of torque analysis in the traditional power system,this paper establishes a small-signal model of VSG with reactive power-voltage controller.Combined with the oscillation mode,the virtual torque coefficient is redefined.Then the relationship between the virtual torque coefficient and VSG stability is analyzed.It is mathematically proved that the lack of virtual damping torque will lead to power oscillation instability of VSG.Taking the VSG with robust droop control as an example,the calculation method of virtual torque coefficient is given,and the conclusion is verified through PSCAD/EMTDC simulation and physical experiment.Finally,this paper discusses the effect of VSG with reactive power-voltage controller on the virtual torque coefficient and system smallsignal stability from different perspectives,such as the initial state of the system,line parameters and controller parameters.The research is beneficial to the VSG controller design and the system small-signal stability analysis.
引文
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[5]陈昕,张昌华,黄琦.引入功率微分项下垂控制的微电网小信号稳定性分析[J].电力系统自动化,2017,41(3):46-53.DOI:10.7500/AEPS20160322010.CHEN Xin,ZHANG Changhua,HUANG Qi.Small-signal stability analysis of parallel inverter system with power differential term droop control[J].Automation of Electric Power Systems,2017,41(3):46-53.DOI:10.7500/AEPS20160322010.
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[12]李武华,王金华,杨贺雅,等.虚拟同步发电机的功率动态耦合机理及同步频率谐振抑制策略[J].中国电机工程学报,2017,37(2):381-391.LI Wuhua,WANG Jinhua,YANG Heya,et al.Dynamic coupling mechanism and resonance suppression of synchronous frequency for virtual synchronous generators[J].Proceedings of the CSEE,2017,37(2):381-391.
[13]WANG Yanbo,WANG Xiongfei,BLAABJERG F,et al.Harmonic instability assessment using state-space modeling and participation analysis in inverter-fed power systems[J].IEEE Transactions on Industrial Electronics,2017,64(1):806-816.
[14]WU Heng,RUAN Xinbo,YANG Dongsheng,et al.Smallsignal modeling and parameters design for virtual synchronous generators[J].IEEE Transactions on Industrial Electronics,2016,63(7):4292-4303.
[15]李明烜,王跃,徐宁一,等.松弛小功角约束条件的虚拟同步发电机功率解耦策略[J].电力系统自动化,2018,42(9):59-68.DOI:10.7500/AEPS20171116001.LI Mingxuan,WANG Yue,XU Ningyi,et al.Power decoupling strategy for virtual synchronous generator relaxing condition of small power angle[J].Automation of Electric Power Systems,2018,42(9):59-68.DOI:10.7500/AEPS20171116001.
[16]WANG Xiongfei,BLAABJERG F,WU Weimin.Modeling and analysis of harmonic stability in an AC power-electronics-based power system[J].IEEE Transactions on Power Electronics,2014,29(12):6421-6432.
[17]辛焕海,李子恒,董炜,等.三相变流器并网系统的广义阻抗及稳定判据[J].中国电机工程学报,2017,37(5):1277-1293.XIN Huanhai,LI Ziheng,DONG Wei,et al.Generalizedimpedance and stability criterion for grid-connected converters[J].Proceedings of the CSEE,2017,37(5):1277-1293.
[18]KUNDUR P.Power system stability and control[M].New York,USA:McGraw-Hill,1994.
[19]陈昕,张昌华,黄琦,等.与SG具有一致响应的VSG小信号建模和分析[J].电力自动化设备,2017,37(11):78-85.CHEN Xin,ZHANG Changhua,HUANG Qi,et al.Smallsignal modeling for virtual synchronous generators consistent with synchronous generator and analysis[J].Electric Power Automation Equipment,2017,37(11):78-85.
[20]TAN Shulong,GENG Hua,YANG Geng.Phillips-Heffron model for current-controlled power electronic generation unit[J].Journal of Modern Power Systems and Clean Energy,2018,6(3):582-594.
[21]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.LZhipeng,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.
[22]袁小明,程时杰,胡家兵.电力电子化电力系统多尺度电压功角动态稳定问题[J].中国电机工程学报,2016,36(19):5145-5154.YUAN Xiaoming,CHENG Shijie,HU Jiabing.Multi-time scale voltage and power angle dynamics in power electronics dominated large power systems[J].Proceedings of the CSEE,2016,36(19):5145-5154.
[23]HUANG Yunhui,YUAN Xiaoming,HU Jiabing,et al.DC-bus voltage control stability affected by AC-bus voltage control in VSCs connected to weak AC grids[J].IEEE Journal of Emerging and Selected Topics in Power Electronics,2016,4(2):445-458.
[24]HUANG L,XIN H,WANG Z.Damping low-frequency oscillations through VSC-HVDC stations operated as virtual synchronous machines[J/OL].IEEE Transactions on Power Electronics[2018-09-21].https://ieeexplore.ieee.org/document/8443108.
[25]付强,杜文娟,王海风.多虚拟同步发电机接入对电力系统机电振荡模式的影响[J].中国电机工程学报,2018,38(19):5615-5624.FU Qiang,DU Wenjuan,WANG Haifeng.Influence of multi virtual synchronous generators on power system electromechanical oscillation mode[J].Proceedings of the CSEE,2018,38(19):5615-5624.
[26]DU Wenjuan,WANG Haifeng,XIAO L Y.Power system small-signal stability as affected by grid-connected photovoltaic generation[J].European Transactions on Electrical Power,2012,22(5):688-703.
[27]肖凡,张昌华.逆变器潮流计算节点类型等效及鲁棒下垂节点的潮流计算[J].电力系统自动化,2018,42(10):75-81.DOI:10.7500/AEPS20170918003.XIAO Fan,ZHANG Changhua.Equivalence of inverter node type in power flow calculation and power flow calculation for robust droop control node[J].Automation of Electric Power Systems,2018,42(10):75-81.DOI:10.7500/AEPS20170918003.
[28]彭克,王成山,李琰,等.典型中低压微电网算例系统设计[J].电力系统自动化,2011,35(18):31-35.PENG Ke,WANG Chengshan,LI Yan,et al.Design of a typical medium-low voltage microgrid network[J].Automation of Electric Power Systems,2011,35(18):31-35.
[2]刘杨华,吴政球,涂有庆,等.分布式发电及其并网技术综述[J].电网技术,2008,32(15):71-76.LIU Yanghua,WU Zhengqiu,TU Youqing,et al.A survey on distributed generation and its networking technology[J].Power System Technology,2008,32(15):71-76.
[3]鲁宗相,王彩霞,闵勇,等.微电网研究综述[J].电力系统自动化,2007,31(19):100-107.LU Zongxiang,WANG Caixia,MIN Yong,et al.Overview on microgrid research[J].Automation of Electric Power Systems,2007,31(19):100-107.
[4]ZHONG Qingchang.Robust droop controller for accurate proportional load sharing among inverters operated in parallel[J].IEEE Transactions on Industrial Electronics,2013,60(4):1281-1290.
[5]陈昕,张昌华,黄琦.引入功率微分项下垂控制的微电网小信号稳定性分析[J].电力系统自动化,2017,41(3):46-53.DOI:10.7500/AEPS20160322010.CHEN Xin,ZHANG Changhua,HUANG Qi.Small-signal stability analysis of parallel inverter system with power differential term droop control[J].Automation of Electric Power Systems,2017,41(3):46-53.DOI:10.7500/AEPS20160322010.
[6]CHEN Yong,HESSE R,TURSCHNER D,et al.Improving the grid power quality using virtual synchronous machines[C]//International Conference on Power Engineering,Energy and Electrical Drives,May 11-13,2011,Malaga,Spain:1-6.
[7]ZHONG Qingchang,WEISS G.Synchronverters:inverters that mimic synchronous generators[J].IEEE Transactions on Industrial Electronics,2011,58(4):1259-1267.
[8]D’ARCO S,SUUL J A.Equivalence of virtual synchronous machines and frequency-droops for converter-based microgrids[J].IEEE Transactions on Smart Grid,2014,5(1):394-395.
[9]SAKIMOTO K,MIURA Y,ISE T.Stabilization of a power system including inverter-type distributed generators by a virtual synchronous generator[J].Electrical Engineering in Japan,2014,187(3):7-17.
[10]LIU Jia,MIURA Y,ISE T.Comparison of dynamic characteristics between virtual synchronous generator and droop control in inverter-based distributed generators[J].IEEETransactions on Power Electronics,2016,31(5):3600-3611.
[11]RASHEDUZZAMAN M,MUELLER J A,KIMBALL J W.An accurate small-signal model of inverter-dominated islanded microgrids using dq reference frame[J].IEEE Journal of Emerging and Selected Topics in Power Electronics,2014,2(4):1070-1080.
[12]李武华,王金华,杨贺雅,等.虚拟同步发电机的功率动态耦合机理及同步频率谐振抑制策略[J].中国电机工程学报,2017,37(2):381-391.LI Wuhua,WANG Jinhua,YANG Heya,et al.Dynamic coupling mechanism and resonance suppression of synchronous frequency for virtual synchronous generators[J].Proceedings of the CSEE,2017,37(2):381-391.
[13]WANG Yanbo,WANG Xiongfei,BLAABJERG F,et al.Harmonic instability assessment using state-space modeling and participation analysis in inverter-fed power systems[J].IEEE Transactions on Industrial Electronics,2017,64(1):806-816.
[14]WU Heng,RUAN Xinbo,YANG Dongsheng,et al.Smallsignal modeling and parameters design for virtual synchronous generators[J].IEEE Transactions on Industrial Electronics,2016,63(7):4292-4303.
[15]李明烜,王跃,徐宁一,等.松弛小功角约束条件的虚拟同步发电机功率解耦策略[J].电力系统自动化,2018,42(9):59-68.DOI:10.7500/AEPS20171116001.LI Mingxuan,WANG Yue,XU Ningyi,et al.Power decoupling strategy for virtual synchronous generator relaxing condition of small power angle[J].Automation of Electric Power Systems,2018,42(9):59-68.DOI:10.7500/AEPS20171116001.
[16]WANG Xiongfei,BLAABJERG F,WU Weimin.Modeling and analysis of harmonic stability in an AC power-electronics-based power system[J].IEEE Transactions on Power Electronics,2014,29(12):6421-6432.
[17]辛焕海,李子恒,董炜,等.三相变流器并网系统的广义阻抗及稳定判据[J].中国电机工程学报,2017,37(5):1277-1293.XIN Huanhai,LI Ziheng,DONG Wei,et al.Generalizedimpedance and stability criterion for grid-connected converters[J].Proceedings of the CSEE,2017,37(5):1277-1293.
[18]KUNDUR P.Power system stability and control[M].New York,USA:McGraw-Hill,1994.
[19]陈昕,张昌华,黄琦,等.与SG具有一致响应的VSG小信号建模和分析[J].电力自动化设备,2017,37(11):78-85.CHEN Xin,ZHANG Changhua,HUANG Qi,et al.Smallsignal modeling for virtual synchronous generators consistent with synchronous generator and analysis[J].Electric Power Automation Equipment,2017,37(11):78-85.
[20]TAN Shulong,GENG Hua,YANG Geng.Phillips-Heffron model for current-controlled power electronic generation unit[J].Journal of Modern Power Systems and Clean Energy,2018,6(3):582-594.
[21]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.LZhipeng,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.
[22]袁小明,程时杰,胡家兵.电力电子化电力系统多尺度电压功角动态稳定问题[J].中国电机工程学报,2016,36(19):5145-5154.YUAN Xiaoming,CHENG Shijie,HU Jiabing.Multi-time scale voltage and power angle dynamics in power electronics dominated large power systems[J].Proceedings of the CSEE,2016,36(19):5145-5154.
[23]HUANG Yunhui,YUAN Xiaoming,HU Jiabing,et al.DC-bus voltage control stability affected by AC-bus voltage control in VSCs connected to weak AC grids[J].IEEE Journal of Emerging and Selected Topics in Power Electronics,2016,4(2):445-458.
[24]HUANG L,XIN H,WANG Z.Damping low-frequency oscillations through VSC-HVDC stations operated as virtual synchronous machines[J/OL].IEEE Transactions on Power Electronics[2018-09-21].https://ieeexplore.ieee.org/document/8443108.
[25]付强,杜文娟,王海风.多虚拟同步发电机接入对电力系统机电振荡模式的影响[J].中国电机工程学报,2018,38(19):5615-5624.FU Qiang,DU Wenjuan,WANG Haifeng.Influence of multi virtual synchronous generators on power system electromechanical oscillation mode[J].Proceedings of the CSEE,2018,38(19):5615-5624.
[26]DU Wenjuan,WANG Haifeng,XIAO L Y.Power system small-signal stability as affected by grid-connected photovoltaic generation[J].European Transactions on Electrical Power,2012,22(5):688-703.
[27]肖凡,张昌华.逆变器潮流计算节点类型等效及鲁棒下垂节点的潮流计算[J].电力系统自动化,2018,42(10):75-81.DOI:10.7500/AEPS20170918003.XIAO Fan,ZHANG Changhua.Equivalence of inverter node type in power flow calculation and power flow calculation for robust droop control node[J].Automation of Electric Power Systems,2018,42(10):75-81.DOI:10.7500/AEPS20170918003.
[28]彭克,王成山,李琰,等.典型中低压微电网算例系统设计[J].电力系统自动化,2011,35(18):31-35.PENG Ke,WANG Chengshan,LI Yan,et al.Design of a typical medium-low voltage microgrid network[J].Automation of Electric Power Systems,2011,35(18):31-35.