基于双向谐波电压变动的光伏并网孤岛检测
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摘要
针对传统的被动式光伏并网孤岛检测存在的检测死区问题,提出一种基于双向谐波电压变化量的光伏并网孤岛检测方法。通过分析孤岛前后谐波电压的变动及传统谐波电压检测法的失效机理,提出基于双向谐波电压的孤岛检测策略。利用加窗傅里叶变换同步计算光伏集中并网发电系统送出线路电流及所接母线电压的谐波,从而获得各次谐波功率;由并网运行时谐波功率的正负极性判断各次谐波源方向,并根据正、负最大谐波功率值选择系统侧、光伏侧谐波的特征频次;利用滑动加窗傅里叶变换分析这2个频次的母线谐波电压变化量,建立孤岛检测判据,若系统侧谐波电压减小量和光伏侧谐波电压增加量均满足判据,则发生孤岛。仿真结果验证了所提方法的有效性。该方法不影响并网逆变器输出的电能质量,且能在较严重背景谐波下有效检测孤岛,检测死区较小。
Aiming at the non-detection zone problem of traditional passive islanding detection for grid-connected PV(PhotoVoltaic) system,a detection method based on bi-direction voltage harmonic variation is proposed. With the analysis of voltage harmonic variation before and after islanding and failure mechanism of traditional voltage harmonic detection method,an islanding detection strategy based on bi-direction voltage harmonic is proposed. The windowed Fourier transform is used to calculate the harmonics of outgoing line current and bus voltage in centralized grid-connected PV system,and thus the harmonic power is obtained. The direction of each harmonic source is determined by the positive or negative polarity of harmonic power in grid-connected operation,and the characteristic orders of harmonic at system side and PV side are selected according to the maximum positive and negative harmonic power values. The sliding windowed Fourier transform is adopted to analyze bus voltage harmonic variation of the two orders,and the islanding detection criteria is established. If the reduction of voltage harmonic at system side and the increment at PV side both meet the criteria,there is an island. Simulative results verify the effectiveness of the proposed method. The method does not affect the output power quality of grid-connected inverters,and can effectively detect islands under serious background harmonics with a small non-detection zone.
Aiming at the non-detection zone problem of traditional passive islanding detection for grid-connected PV(PhotoVoltaic) system,a detection method based on bi-direction voltage harmonic variation is proposed. With the analysis of voltage harmonic variation before and after islanding and failure mechanism of traditional voltage harmonic detection method,an islanding detection strategy based on bi-direction voltage harmonic is proposed. The windowed Fourier transform is used to calculate the harmonics of outgoing line current and bus voltage in centralized grid-connected PV system,and thus the harmonic power is obtained. The direction of each harmonic source is determined by the positive or negative polarity of harmonic power in grid-connected operation,and the characteristic orders of harmonic at system side and PV side are selected according to the maximum positive and negative harmonic power values. The sliding windowed Fourier transform is adopted to analyze bus voltage harmonic variation of the two orders,and the islanding detection criteria is established. If the reduction of voltage harmonic at system side and the increment at PV side both meet the criteria,there is an island. Simulative results verify the effectiveness of the proposed method. The method does not affect the output power quality of grid-connected inverters,and can effectively detect islands under serious background harmonics with a small non-detection zone.
引文
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[18]郑涛,王燕萍,袁飞,等.基于工频突变量阻抗测量的新型孤岛检测方法[J].电力自动化设备,2016,36(5):8-13.ZHENG Tao,WANG Yanping,YUAN Fei,et al. Islanding detection based on power-frequency variation impedance[J]. Electric Power Automation Equipment,2016,36(5):8-13.
[19]JANG S I,KIM K H. An islanding detection method for distributed generations using voltage unbalance and total harmonic distortion of current[J]. IEEE Transactions on Power Delivery,2004,19(2):745-752.
[20]徐华电,苏建徽,张军军,等.基于谐波特征与核Fisher判别分析的孤岛检测方法研究[J].电工技术学报,2016,31(3):25-30.XU Huadian,SU Jianhui,ZHANG Junjun,et al. Research on islanding detection based on harmonic characteristics and kernel fisher discriminant analysis[J]. Transactions of China Electrotechnical Society,2016,31(3):25-30.
[2]刘方锐,余蜜,张宇.主动移频法在光伏并网逆变器并联运行下的孤岛检测机理研究[J].中国电机工程学报,2009,29(12):47-51.LIU Fangrui,YU Mi,ZHANG Yu. Islanding detection evaluation for active frequency drifting methods in multiple photovoltaic grid-connected converters[J]. Proceedings of the CSEE,2009,29(12):47-51.
[3]蔡逢煌,郑必伟,王武.结合同步锁相的光伏并网发电系统孤岛检测技术[J].电工技术学报,2012,27(10):202-206.CAI Fenghuang,ZHENG Biwei,WANG Wu. Islanding detection method combined with PLL for photovoltaic grid-connected power system[J]. Transactions of China Electrotechnical Society,2012,27(10):202-206.
[4]ROPP M,LARSON D,MEANDERING S,et al. Discussion of a power line carrier communications-based anti-islanding scheme using a commercial automatic meter reading system[C]∥2006 IEEE 4th World Conference on Photovoltaic Energy Conversion. Waikoloa,HI,USA:[s.n.],2006:2351-2354.
[5]REFERRN M A,USTA O,FIELDING G. Protection against loss of utility grid supply for a dispersed storage and generation unit[J].IEEE Transactions on Power Delivery,1993,8(3):948-954.
[6]赵峰,葸代其.分布式电源并网系统远程孤岛检测方法的研究[J].电源技术,2014,38(3):586-589.ZHAO Feng,XI Daiqi. Analysis of remote islanding detection methods for distributed generation grid-connected systems[J]. Chinese Journal of Power Sources,2014,38(3):586-589.
[7]张凯航,袁越,傅质馨,等.基于正切滑模频移法的孤岛检测方法[J].电力自动化设备,2013,33(12):66-72.ZHANG Kaihang,YUAN Yue,FU Zhixin,et al. Islanding detection based on tangent sliding mode frequency shift method[J]. Electric Power Automation Equipment,2013,33(12):66-72.
[8]刘芙蓉,王辉,康勇,等.滑模频率偏移法的孤岛检测盲区分析[J].电工技术学报,2009,24(2):178-182.LIU Furong,WANG Hui,KANG Yong,et al. Non-detection zone of slip-mode frequency shift method[J]. Transactions of China Electrotechnical Society,2009,24(2):178-182.
[9]张纯江,郭忠南,孟慧英,等.主动电流扰动法在并网发电系统孤岛检测中的应用[J].电工技术学报,2007,22(7):176-180.ZHANG Chunjiang,GUO Zhongnan,MENG Huiying,et al. Active current disturbing method for islanding detection of grid-connected inverters[J]. Transactions of China Electrotechnical Society,2007,22(7):176-180.
[10]丁浩,魏艳君,漆汉宏,等.基于自适应有功电流扰动的孤岛检测[J].电工技术学报,2014,29(8):294-300.DING Hao,WEI Yanjun,QI Hanhong,et al. A novel islanding detection based on adaptive active current disturbance[J]. Transactions of China Electrotechnical Society,2014,29(8):294-300.
[11]贺超,王冕,陈国柱.基于下垂控制的孤岛检测方法及其改进策略[J].电力自动化设备,2015,35(6):87-92.HE Chao,WANG Mian,CHEN Guozhu. Islanding detection based on droop control and its improvement strategy[J]. Electric Power Automation Equipment,2015,35(6):87-92.
[12]杨滔,王鹿军,张冲,等.基于无功电流-频率正反馈的孤岛检测方法[J].电力系统自动化,2012,36(14):193-199.YANG Tao,WANG Lujun,ZHANG Chong,et al. A novel islanding detection method based on positive feedback between reactive current and frequency[J]. Automation of Electric Power Systems,2012,36(14):193-199.
[13]CAI Wen,LIU Bangyin,DUAN Shanxu,et al. An islanding detection method based on dual-frequency harmonic current injection under grid impedance unbalanced condition[J]. IEEE Transactions on Industrial Informatics,2013,9(2):1178-1187.
[14]KARIMI H,YAZDANI A,IRAVANI R. Negative-sequence current injection for fast islanding detection of a distributed resource unit[J]. IEEE Transactions on Power Electronics,2008,23(1):298-307.
[15]贾科,郇凯翔,魏宏升,等.适用于多机集群的外部集中扰动式阻抗测量孤岛检测法[J].电工技术学报,2016,31(13):120-129.JIA Ke,HUAN Kaixiang,WEI Hongsheng,et al. An islanding detection method based on impedance estimation using external centralized disturbances for multi-distributed generation system[J].Transactions of China Electrotechnical Society,2016,31(13):120-129.
[16]YE Zhihong,KOLWALKAR A,ZHANG Yu,et al. Evaluation of anti-islanding schemes based on nondetection zone concept[J]. IEEE Transactions on Power Electronics,2004,19(5):1171-1176.
[17]FRANCESCO J D M,MARCO L,ALBERTO P. Overview of antiislanding algorithms for PV systems:part a passive methods[C]∥12th International Conference:Power Electronics and Motion Control Conference,2006. Portoroz,Slovenia:[s.n.],2007:1878-1883.
[18]郑涛,王燕萍,袁飞,等.基于工频突变量阻抗测量的新型孤岛检测方法[J].电力自动化设备,2016,36(5):8-13.ZHENG Tao,WANG Yanping,YUAN Fei,et al. Islanding detection based on power-frequency variation impedance[J]. Electric Power Automation Equipment,2016,36(5):8-13.
[19]JANG S I,KIM K H. An islanding detection method for distributed generations using voltage unbalance and total harmonic distortion of current[J]. IEEE Transactions on Power Delivery,2004,19(2):745-752.
[20]徐华电,苏建徽,张军军,等.基于谐波特征与核Fisher判别分析的孤岛检测方法研究[J].电工技术学报,2016,31(3):25-30.XU Huadian,SU Jianhui,ZHANG Junjun,et al. Research on islanding detection based on harmonic characteristics and kernel fisher discriminant analysis[J]. Transactions of China Electrotechnical Society,2016,31(3):25-30.