弱电网中增强LCL逆变器稳定性的虚拟阻抗控制
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摘要
LCL型逆变器广泛应用于新能源发电并网系统中。在弱电网条件下,并网阻抗与控制参数不匹配是导致系统稳定性下降甚至失稳的主要原因。从削弱不匹配程度的角度出发,基于电流双闭环控制模型,分析了并网阻抗影响系统稳定性的作用机理,提出了网侧串联虚拟电感的改进方法。先增大网侧等效滤波电感的值,再进行控制参数设计,降低了并网阻抗对系统稳定性的影响程度,从而改善了系统稳定性。采用Bode图及根轨迹法对比分析了常规及改进控制策略,结果表明:同等弱电网条件下,采用改进方法系统稳定性更好。此外改进方法可以允许并网阻抗在更大范围内波动,提高了系统对弱电网的适应能力。最后采用Matlab/Simulink仿真进行了验证。
LCL inverter has been widely used in grid connected application for renewable power generation. In weak grid,mismatch between grid impedance and control parameters may decrease the system stability, or even lead to instability.Taking the degree of mismatch into account and based on the current double closed-closed loop control model, we analyzed the mechanism of grid impedance affecting the system stability and proposed an improved method of network-side series virtual inductance. The effect of grid impedance on system stability was reduced by increasing the equivalent filter inductance at the grid side before designing the control parameters, which enhances the system stability. The conventional and improved control strategies were compared and analyzed by the Bode diagram and root locus method. The results show that, under the same condition of weak grid, the improved method has better system stability. In addition, the improved method can allow the grid impedance to fluctuate in a larger range and improve the system's adaptability to weak grids. The above conclusions are verified by Matlab/Simulink simulation.
LCL inverter has been widely used in grid connected application for renewable power generation. In weak grid,mismatch between grid impedance and control parameters may decrease the system stability, or even lead to instability.Taking the degree of mismatch into account and based on the current double closed-closed loop control model, we analyzed the mechanism of grid impedance affecting the system stability and proposed an improved method of network-side series virtual inductance. The effect of grid impedance on system stability was reduced by increasing the equivalent filter inductance at the grid side before designing the control parameters, which enhances the system stability. The conventional and improved control strategies were compared and analyzed by the Bode diagram and root locus method. The results show that, under the same condition of weak grid, the improved method has better system stability. In addition, the improved method can allow the grid impedance to fluctuate in a larger range and improve the system's adaptability to weak grids. The above conclusions are verified by Matlab/Simulink simulation.
引文
[1]王玮,李睿,姜久春.面向能源互联网的配电系统规划关键问题研究综述与展望[J].高电压技术,2016,42(7):2028-2036.WANG Wei,LI Rui,JIANG Jiuchun.Key issues and research prospects of distribution system planning orienting to energy internet[J].High Voltage Engineering,2016,42(7):2028-2036.
[2]徐晓宁,周雪松.微网脱/并网运行模式平滑切换控制策略[J].高电压技术,2018,44(8):2754-2760.XU Xiaoning,ZHOU Xuesong.Control strategy for smooth transfer between grid-connected and island operation for micro grid[J].High Voltage Engineering,2018,44(8):2754-2760.
[3]杨兴武,陈磊,牛梦娇.LCL滤波并网逆变器多速率重复控制策略[J].高电压技术,2018,44(10):3231-3240.YANG Xingwu,CHEN Lei,NIU Mengjiao.Multirate repetitive control strategy for grid-connected inverter with LCL filter[J].High Voltage Engineering,2018,44(10):3231-3240.
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[8]殷进军,刘邦银,段善旭.LCL滤波并网逆变器双环控制参数设计与优化[J].电力系统自动化,2013,37(9):123-128.YIN Jinjun,LIU Bangyin,DUAN Shanxu.Design and optimization of double loop control parameters for filtering and grid connected inverters[J].Automation of Electric Power Systems,2013,37(9):123-128.
[9]王学华,阮新波,刘尚伟.抑制电网背景谐波影响的并网逆变器控制策略[J].中国电机工程学报,2011,31(6):7-14.WANG Xuehua,RUAN Xinbo,LIU Shangwei.Control strategy for gird-connected inverter to suppress current distortion effected by background harmonics in grid voltage[J].Proceedings of the CSEE,2011,31(6):7-14.
[10]杨明,周林,张东霞,等.考虑电网阻抗影响的大型光伏电站并网稳定性分析[J].电工技术学报,2013,28(9):214-223.YANG Ming,ZHOU Lin,ZHANG Dongxia,et al.Stability analysis of large-scale photovoltaic power plants for the effect of grid impedance[J].Transactions of China Electrotechnical Society,2013,28(9):214-223.
[11]周林,张密,居秀丽,等.电网阻抗对大型并网光伏系统稳定性影响分析[J].中国电机工程学报,2013,33(34):34-41.ZHOU Lin,ZHANG Mi,JU Xiuli,et al.Stability analysis of large-scale photovoltaic plants due to grid impedances[J].Proceedings of the CSEE,2013,33(34):34-41.
[12]周林,张密,杨明,等.考虑电网阻抗影响的LCL型并网逆变器控制策略[J].太阳能学报,2015,36(9):2146-2151.ZHOU Lin,ZHANG Mi,YANG Ming,et al.Control strategy of LCLgrid connected inverter considering the influence of electrical network impedance[J].Acta Energiae Solaris Sinica,2015,36(9):2146-2151.
[13]SUN J.Impedance-based stability criterion for grid connected inverters[J].IEEE Transactions on Power Electronics,2011,26(11):3075-3078.
[14]YANG D S,RUAN X B,WU H.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]滕宇,王学华,余辉,等.提高LCL型并网逆变器对电网阻抗鲁棒性的阻抗调节方法[J].中国电机工程学报,2015,35(S1):197-204.TENG Yu,WANG Xuehua,YU Hui,et al.A grid impedance shaping method to improve robustness of LCL-type gird-connected inverter against grid impedance variation[J].Proceedings of the CSEE,2015,35(S1):197-204.
[16]许津铭,谢少军,唐婷.弱电网下LCL滤波并网逆变器自适应电流控制[J].中国电机工程学报,2014,34(24):4031-4039.XU Jinming,XIE Shaojun,TANG Ting.An adaptive current control for grid-connected LCL-filtered inverters in weak grid case[J].Proceedings of the CSEE,2014,34(24):4031-4039.
[17]何超杰,赵晋斌,杨旭红,等.弱电网下基于系统敏感度的逆变器自适应控制[J].电网技术,2017,41(1):238-244.HE Chaojie,ZHAO Jinbin,YANG Xuhong,et al.Adaptive control strategy for grid-connected inverter based on system sensitivity in weak grid[J].Power System Technology,2017,41(1):238-244.
[18]刘桂花,石桐,马田源,等.弱电网下光伏并网逆变器自适应准PRD控制方法[J].电网技术,2017,41(1):112-117.LIU Guihua,SHI Tong,MA Tianyuan,et al.Adaptive quasi-PRD control method of grid-connected PV inverter in weak grid[J].Power System Technology,2017,41(1):112-117.
[19]宋吉峰.LCL并网逆变器的设计与控制研究[D].武汉:华中科技大学,2014.SONG Jifeng.Design and control strategy for grid-connected inverter with LCL filter[D].Wuhan,China:Huazhong University of Science and Technology,2014.
[2]徐晓宁,周雪松.微网脱/并网运行模式平滑切换控制策略[J].高电压技术,2018,44(8):2754-2760.XU Xiaoning,ZHOU Xuesong.Control strategy for smooth transfer between grid-connected and island operation for micro grid[J].High Voltage Engineering,2018,44(8):2754-2760.
[3]杨兴武,陈磊,牛梦娇.LCL滤波并网逆变器多速率重复控制策略[J].高电压技术,2018,44(10):3231-3240.YANG Xingwu,CHEN Lei,NIU Mengjiao.Multirate repetitive control strategy for grid-connected inverter with LCL filter[J].High Voltage Engineering,2018,44(10):3231-3240.
[4]刘宝泉,郭华,朱一昕.三相变流器无源阻尼型LCL滤波器的分析与设计[J].电工技术学报,2017,32(2):195-205.LIU Baoquan,GUO Hua,ZHU Yixin.Analysis and design of a passively damping LCL filter in three-phase converters[J].Transactions of China Electrotechnical Society,2017,32(2):195-205.
[5]程林.不同电网条件下并网逆变器稳定性研究[D].南京:南京航空航天大学,2012.CHENG Lin.Research on the stability of grid-connected inverter under different grid conditions[D].Nanjing,China:Nanjing University of Aeronautics and Astronautics,2012.
[6]LEI Y,ZHAO Z M,HE F B,et al.An improved virtual resistance damping method for grid-connected inverters with LCL filters[C]∥2011 IEEE Energy Conversion Congress and Exposition.Phoenix,Argentina:IEEE,2011:3816-3822.
[7]沈国桥,徐德鸿.LCL滤波并网逆变器的分裂电容法电流控制[J].中国电机工程学报,2008,28(18):36-41.SHEN Guoqiao,XU Dehong.Current control for grid-connected inverters by splitting the capacitor of LCL filter[J].Proceedings of the CSEE,2008,28(18):36-41.
[8]殷进军,刘邦银,段善旭.LCL滤波并网逆变器双环控制参数设计与优化[J].电力系统自动化,2013,37(9):123-128.YIN Jinjun,LIU Bangyin,DUAN Shanxu.Design and optimization of double loop control parameters for filtering and grid connected inverters[J].Automation of Electric Power Systems,2013,37(9):123-128.
[9]王学华,阮新波,刘尚伟.抑制电网背景谐波影响的并网逆变器控制策略[J].中国电机工程学报,2011,31(6):7-14.WANG Xuehua,RUAN Xinbo,LIU Shangwei.Control strategy for gird-connected inverter to suppress current distortion effected by background harmonics in grid voltage[J].Proceedings of the CSEE,2011,31(6):7-14.
[10]杨明,周林,张东霞,等.考虑电网阻抗影响的大型光伏电站并网稳定性分析[J].电工技术学报,2013,28(9):214-223.YANG Ming,ZHOU Lin,ZHANG Dongxia,et al.Stability analysis of large-scale photovoltaic power plants for the effect of grid impedance[J].Transactions of China Electrotechnical Society,2013,28(9):214-223.
[11]周林,张密,居秀丽,等.电网阻抗对大型并网光伏系统稳定性影响分析[J].中国电机工程学报,2013,33(34):34-41.ZHOU Lin,ZHANG Mi,JU Xiuli,et al.Stability analysis of large-scale photovoltaic plants due to grid impedances[J].Proceedings of the CSEE,2013,33(34):34-41.
[12]周林,张密,杨明,等.考虑电网阻抗影响的LCL型并网逆变器控制策略[J].太阳能学报,2015,36(9):2146-2151.ZHOU Lin,ZHANG Mi,YANG Ming,et al.Control strategy of LCLgrid connected inverter considering the influence of electrical network impedance[J].Acta Energiae Solaris Sinica,2015,36(9):2146-2151.
[13]SUN J.Impedance-based stability criterion for grid connected inverters[J].IEEE Transactions on Power Electronics,2011,26(11):3075-3078.
[14]YANG D S,RUAN X B,WU H.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]滕宇,王学华,余辉,等.提高LCL型并网逆变器对电网阻抗鲁棒性的阻抗调节方法[J].中国电机工程学报,2015,35(S1):197-204.TENG Yu,WANG Xuehua,YU Hui,et al.A grid impedance shaping method to improve robustness of LCL-type gird-connected inverter against grid impedance variation[J].Proceedings of the CSEE,2015,35(S1):197-204.
[16]许津铭,谢少军,唐婷.弱电网下LCL滤波并网逆变器自适应电流控制[J].中国电机工程学报,2014,34(24):4031-4039.XU Jinming,XIE Shaojun,TANG Ting.An adaptive current control for grid-connected LCL-filtered inverters in weak grid case[J].Proceedings of the CSEE,2014,34(24):4031-4039.
[17]何超杰,赵晋斌,杨旭红,等.弱电网下基于系统敏感度的逆变器自适应控制[J].电网技术,2017,41(1):238-244.HE Chaojie,ZHAO Jinbin,YANG Xuhong,et al.Adaptive control strategy for grid-connected inverter based on system sensitivity in weak grid[J].Power System Technology,2017,41(1):238-244.
[18]刘桂花,石桐,马田源,等.弱电网下光伏并网逆变器自适应准PRD控制方法[J].电网技术,2017,41(1):112-117.LIU Guihua,SHI Tong,MA Tianyuan,et al.Adaptive quasi-PRD control method of grid-connected PV inverter in weak grid[J].Power System Technology,2017,41(1):112-117.
[19]宋吉峰.LCL并网逆变器的设计与控制研究[D].武汉:华中科技大学,2014.SONG Jifeng.Design and control strategy for grid-connected inverter with LCL filter[D].Wuhan,China:Huazhong University of Science and Technology,2014.