Abstract：The grid shows the characteristics of weak grid due to scattered high power distributed power generation device. The grid impedance will affect the robust stability of the grid-connected inverters and lead to harmonic resonance as well as the instability of the system. The output impedance model of LCL-filtered single-phase grid-connected inverter was derived, and the study of stability based on impedance analysis was presented in the paper. In order to increase the phase margin of the grid-connected inverters, a novel impedance phase compensation control strategy was proposed, and the detailed implementation and parameter design of the impedance phase compensation control method was depicted. The effect of PLL loop, digital control delay, and the impedance phase compensation control on the output impedance characteristic was analyzed in quantity. The fundamental frequency phase effect of impedance phase compensation control was also analyzed. Finally combining impulse response based grid impedance online measurement and the impedance-phased dynamic control scheme was introduced, and the effectiveness of the impedance-phased dynamic control was verified by experiment.
[1] 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 Transactions on Power Electronics,2006,21(1):263-272. [2] Abeyasekera T,Johnson C M,Atkinson D J.Suppression of line voltage related distortion in current controlled grid connected inverters[J].IEEE Transactions on Power Electronics,2005,20(6):1393-1401. [3] Midtsund T,Suul J A,Undeland T.Evaluation of current controller performance and stability for voltage source converters connected to a weak grid[J].IEEE International Symposium on Power Electronics for Distributed Generation Systems,2010,24(1):382-388. [4] Xu Jinming,Xie Shaojun,Tang Ting.Evaluations of current control in weak grid case for grid-connected LCL-filtered inverter[J].IET Power Electronics,2013,6(2):227-234. [5] Xu Jinming,Xie Shaojun,Tang Ting.Improved control strategy with grid-voltage feedforward for LCL-filter-based inverter connected to weak grid[J].IET Power Electronics,2014,7(10):2660-2671. [6] 张战彬,翟红霞,徐华博,等.光伏电站多逆变器并网系统输出谐波研究[J].电力系统保护与控制,2016,44(14):142-146. Zhang Zhanbin,Zhai Hongxia,Xu Huabo,et al.Study on output harmonic of multi-inverter grid-connected in photovoltaic plant[J].Power System Protection and Control,2016,44(14):142-146. [7] Sun J.AC power electronic systems:stability and power quality[C]//Workshop on Control & Modeling for Power Electronics,2008:1-10. [8] 段晓丽,罗耀华,游江,等.基于阻抗分析的三相逆变器负载不平衡控制[J].电工技术学报,2012,27(12):56-62. Duan Xiaoli,Luo Yaohua,You Jiang,et al.Control strategy based on impedance analysis for three-phase inverter with unbalanced load [J].Transactions of China Electrotechnical Society,2012,27(12):56-62. [9] Cespedes M,Sun Jian.Adaptive control of grid-connected inverters based on online grid impedance measurements[J].IEEE Transactions on Sustainable Energy,2014,5(2):516-523. [10]田鹏,宣文华,牛益国.基于陷波控制的LCL型光伏并网逆变器谐波谐振抑制研究[J].电力系统保护与控制,2016,44(14):82-88. Tian Peng,Xuan Wenhua,Niu Yiguo.Suppression of harmonic resonance for photovoltaic grid-connected inverter with LCL filter based on notch filter control[J].Power System Protection and Control,2016,44(14):82-88. [11]曾正,赵荣祥,吕志鹏,等.光伏并网逆变器的阻抗重塑与谐波谐振抑制[J].中国电机工程学报,2014,34(27):4547-4558. Zeng Zheng,Zhao Rongxiang,Lü Zhipeng,et al.Impedance reshaping of grid-tied inverters to damp the series and parallel harmonic resonances of photovoltaic systems[J].Proceedings of the CSEE,2014,34(27):4547-4558. [12]陈新,韦徵,胡雪峰,等.三相并网逆变器LCL滤波器的研究及新型有源阻尼控制[J].电工技术学报,2014,29(6):71-79. Chen Xin,Wei Zheng,Hu Xuefeng,et al.Research on LCL filter in three-phase grid-connected inverter and novel active damping control strategy[J].Transactions of China Electrotechnical Society,2014,29(6):71-79. [13]陈新,张旸,王赟程.基于阻抗分析法研究光伏并网逆变器与电网的动态交互影响[J].中国电机工程学报,2014,34(27):4559-4567. Chen Xin,Zhang Yang,Wang Yuncheng.A study of dynamic interaction between PV grid-connected inverters and the grid based on the impedance analysis method[J].Proceedings of the CSEE,2014,34(27):4559-4567. [14]Yang Dongsheng,Ruan Xinbo,Wu Heng.Impedance shaping of the grid-connected inverter with LCL filter to improve its adaptability to the weak grid condition[J].IEEE Transactions on Power Electronics,2014,29(11):5795-5805. [15]张庆海,罗安,陈燕东,等.并联逆变器输出阻抗分析及电压控制策略[J].电工技术学报,2014,29(6):98-105. Zhang Qinghai,Luo An,Chen Yandong,et al.Analysis of output impedance for parallel inverters and voltage control strategy[J].Transactions of China Electrotechnical Society,2014,29(6):98-105. [16]张力,任小永,阮新波.基于虚拟阻抗且提高系统带宽的抑制两级式逆变器中二次谐波电流的控制策略[J].电工技术学报,2014,29(6):136-144. Zhang Li,Ren Xiaoyong,Ruan Xinbo.Control strategy to improve the bandwidth and reduce the second harmonic current in the two-stage inverter based on virtual impedance[J].Transactions of China Electrotechnical Society,2014,29(6):136-144. [17]杨立滨,张海宁,李春来,等.基于虚拟导纳的大型光伏电站谐波抑制策略研究[J].电力系统保护与控制,2016,44(18):120-126. Yang Libin,Zhang Haining,Li Chunlai,et al.Harmonic suppression strategy of large-scale photovoltaic plants based on virtual admittance[J].Power System Protection and Control,2016,44(18):120-126. [18]吴恒,阮新波,杨东升.弱电网条件下锁相环对LCL型并网逆变器稳定性的影响研究及锁相环参数设计[J].中国电机工程学报,2014,34(30):5259-5268. Wu Heng,Ruan Xinbo,Yang Dongsheng.Research on the stability caused by phase-locked loop for LCL-type grid-connected inverter in weak grid condition[J].Proceedings of the CSEE,2014,34(30):5259-5268. [19]Sun Jian.Impedance-based stability criterion for grid-connected inverters[J].IEEE Transactions on Power Electronics,2011,26(11):3075-3078. [20]Cespedes M,Sun Jian.Online grid impedance identification for adaptive control of grid-connected inverters[C]//IEEE Energy Conversion Congress & Exposition,2012:914-921. [21]Xie Ming,Ding Kang.Corrections for frequency,amplitude and phase in a fast fourier transform of a harmonic signal[J].Mechanical Systems and Signal Processing,1996,10(2):211-221.
2017, Vol. 32 
