混合直流输电直流侧谐波分析及滤波器设计
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摘要
为评估混合直流输电直流侧电压质量,解析其谐波成分和幅值计算等效电路,该文采用平均开关状态法分析MMC,调制理论分析LCC产生的谐波,推导各次谐波的幅值计算表达式,简化等效电路。在此基础上,分析了LC滤波后的波形和谐波成分,在交流侧三相不平衡度较大时,LC滤波器平抑低频谐波效果差;为抑制因三相不平衡引起的直流侧低频脉动,设计了两种3阶低通滤波器,并对比了它们与LC滤波器在滤波效果和动态响应时间上的差别,结果表明巴特沃斯滤波器的指标最佳。利用MATLAB/Simulink软件建立了混合直流输电模型,仿真结果显示所推导的谐波幅值计算表达式和等效电路能正确反映直流侧的谐波特征,所设计的滤波器能更好地消除低频谐波。
In order to evaluate the voltage quality of direct current(DC) side in hybrid high voltage direct current(HVDC) transmission, the harmonic component and amplitude calculation equivalent circuit of the DC side in HVDC are analyzed. The average switching state method is used to analyze modular multilevel converter(MMC)and the modulation theory is applied to analyze the harmonics generated by line commutated converter(LCC).Then, amplitude calculation expression and simplified equivalent circuit of each harmonic are derived. On this basis, the LC filtering waveform and harmonic components are further examined and the result shows that the LC filter has poor effect in suppressing the low-frequency harmonics under the large alternating current(AC)three-phase unbalance factor. Thus two kinds of third-order low-pass filters are designed to suppress low frequency fluctuation of DC side caused by three-phase unbalance. Comparing the difference of the filtering effect and the dynamic response time between the designed filters and LC filter, the results show that the Butterworth filter has the best index. The hybrid HVDC transmission model is established by using MATLAB/Simulink software. The simulation results show that the derived harmonic amplitude calculation expression and equivalent circuit can correctly reflect the harmonic characteristics of the DC side, and the designed filters has better effect in eliminating the low frequency harmonics.
In order to evaluate the voltage quality of direct current(DC) side in hybrid high voltage direct current(HVDC) transmission, the harmonic component and amplitude calculation equivalent circuit of the DC side in HVDC are analyzed. The average switching state method is used to analyze modular multilevel converter(MMC)and the modulation theory is applied to analyze the harmonics generated by line commutated converter(LCC).Then, amplitude calculation expression and simplified equivalent circuit of each harmonic are derived. On this basis, the LC filtering waveform and harmonic components are further examined and the result shows that the LC filter has poor effect in suppressing the low-frequency harmonics under the large alternating current(AC)three-phase unbalance factor. Thus two kinds of third-order low-pass filters are designed to suppress low frequency fluctuation of DC side caused by three-phase unbalance. Comparing the difference of the filtering effect and the dynamic response time between the designed filters and LC filter, the results show that the Butterworth filter has the best index. The hybrid HVDC transmission model is established by using MATLAB/Simulink software. The simulation results show that the derived harmonic amplitude calculation expression and equivalent circuit can correctly reflect the harmonic characteristics of the DC side, and the designed filters has better effect in eliminating the low frequency harmonics.
引文
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[13]陈鹏伟,肖湘宁,陶顺.直流微网电能质量问题探讨[J].电力系统自动化,2016,40(10):148-158.CHEN Peng-wei,XIANG Xiang-ning,TAO Shun.Discussion on power quality problems for DC microgrid[J].Automation of Electric Power Systems,2016,40(10):148-158.
[14]王佳佳,周念成,王强钢,等.电网电压不平衡下串联型12脉波整流装置的频域谐波建模[J].电工技术学报,2015,30(5):69-78.WANG Jia-jia,ZHOU Nian-cheng,WANG Qiang-gang,et al.Frequency-domain harmonic modeling of the series12-pulse rectifier under unbalanced voltage condition[J].Transactions of China Electrotechnical Society,2015,30(5):69-78.
[15]张哲任,徐政,薛英林.LCC-MMC混合直流输电系统直流侧谐波电流计算[J].电力系统自动化,2014,38(23):65-70.ZHANG Zhe-ren,XU Zheng,XUE Ying-lin.Calculation of DC side harmonics currents for LCCMMC hybrid HVDC transmission system[J].Automation of Electric Power Systems,2014,38(23):65-70.
[16]郭春义,刘文静,赵成勇,等.混合直流输电系统的参数优化方法[J].电力系统自动化,2015(11):96-102.GUO Chun-yi,LIU Wen-jing,ZHAO Cheng-yong,et al.Parameters optimization method of hybrid HVDCtransmission system[J].Automation of Electric Power Systems,2015,39(11):96-102.
[2]韦延方,卫志农,孙国强,等.一种新型的高压直流输电技术--MMC-HVDC[J].电力自动化设备,2012,32(7):1-9.WEI Yan-fang,WEI Zhi-nong,SUN Guo-qiang,et al.New HVDC power transmission technology:MMC-HVDC[J].Electric Power Automation Equipment,2012,32(7):1-9.
[3]宋强,饶宏.柔性直流输电换流器的分析与设计[M].北京:清华大学出版社,2015.SONG Qiang,RAO Hong.Analysis and design of the converters in VSC-HVDC system[M].Beijing:Tsinghua University Press,2015.
[4]刘剑,邰能灵,范春菊,等.柔性直流输电线路故障处理与保护技术评述[J].电力系统自动化,2015(20):158-167.LIU Jian,TAI Neng-ling,FAN Chun-ju,et al.Comments on fault handling and protection technology for VSC-HVDCtransmission lines[J].Automation of Electric Power Systems,2015,39(20):158-167.
[5]李英彪,卜广全,王姗姗,等.张北柔直电网工程直流线路短路过程中直流过电压分析[J].中国电机工程学报,2017,37(12):3391-3399.LI Ying-biao,BU Guang-quan,WANG Shan-shan,et al.Analysis of DC overvoltage caused by DC short-circuit fault in Zhangbei VSC-based DC grid[J].Proceedings of the CSEE,2017,37(12):3391-3399.
[6]赵成勇,郭春义,刘文静.混合直流输电[M].科学出版社,2014.ZHAO Cheng-yong,GUO Chun-yi,LIU Wen-jing.Hybrid HVDC system[M].Beijing:Science Press,2014.
[7]唐庚,徐政,薛英林.LCC-MMC混合高压直流输电系统[J].电工技术学报,2013,28(10):301-310.TANG Geng,XU Zheng,XUE Ying-lin.A LCC-MMChybrid HVDC transmission system[J].Transactions of China Electrotechnical Society,2013,28(10):301-310.
[8]翟冬玲,韩民晓,严稳利,等.DFIG型海上风电混合直流送出的控制策略[J].电力自动化设备,2015,35(2):42-48.ZHAI Dong-ling,HAN Min-xiao,YAN Wen-li,et al.Control of offshore DFIG-based wind farm with hybrid HVDC transmission[J].Electric Power Automation Equipment,2015,35(2):42-48.
[9]黄伟煌,饶宏,黄莹,等.一种基于常规直流输电系统的混合直流改造方案[J].中国电机工程学报,2017,37(10):2861-2868.HUANG Wei-huang,RAO Hong,HUANG Ying,et al.Anovel refurbishment scheme for reforming the existing LCC-HVDC to hybrid HVDC[J].Proceedings of the CSEE,2017,37(10):2861-2868.
[10]MOBARREZ M,KASHANI M G,BHATTACHARYA S.A novel control approach for protection of multiterminal VSC-Based HVDC transmission system against dc faults[J].IEEE Transactions on Industry Applications,2016,52(5):4108-4116.
[11]孙孝峰,韩瑞静,龚钢,等.考虑阻性有源滤波器等效输出阻抗的背景谐波抑制方案优化[J].中国电机工程学报,2015,35(18):4736-4743.SUN Xiao-feng,HAN Rui-jing,GONG Gang,et al.Anovel control strategy for background harmonic damping considering the equivalent output impedance of resistive active power filters[J].Proceedings of the CSEE,2015,35(18):4736-4743.
[12]焦晋荣,贾清泉,王宁,等.柔性直流配电网纹波形成机理与叠加特性[J].电网技术,2017(6):1726-1733.JIAO Jin-rong,JIA Qing-quan,WANG Ning,et al.Ripple formation mechanism and superimposition characteristics for flexible DC distribution network[J].Power System Technology,2017(6):1726-1733.
[13]陈鹏伟,肖湘宁,陶顺.直流微网电能质量问题探讨[J].电力系统自动化,2016,40(10):148-158.CHEN Peng-wei,XIANG Xiang-ning,TAO Shun.Discussion on power quality problems for DC microgrid[J].Automation of Electric Power Systems,2016,40(10):148-158.
[14]王佳佳,周念成,王强钢,等.电网电压不平衡下串联型12脉波整流装置的频域谐波建模[J].电工技术学报,2015,30(5):69-78.WANG Jia-jia,ZHOU Nian-cheng,WANG Qiang-gang,et al.Frequency-domain harmonic modeling of the series12-pulse rectifier under unbalanced voltage condition[J].Transactions of China Electrotechnical Society,2015,30(5):69-78.
[15]张哲任,徐政,薛英林.LCC-MMC混合直流输电系统直流侧谐波电流计算[J].电力系统自动化,2014,38(23):65-70.ZHANG Zhe-ren,XU Zheng,XUE Ying-lin.Calculation of DC side harmonics currents for LCCMMC hybrid HVDC transmission system[J].Automation of Electric Power Systems,2014,38(23):65-70.
[16]郭春义,刘文静,赵成勇,等.混合直流输电系统的参数优化方法[J].电力系统自动化,2015(11):96-102.GUO Chun-yi,LIU Wen-jing,ZHAO Cheng-yong,et al.Parameters optimization method of hybrid HVDCtransmission system[J].Automation of Electric Power Systems,2015,39(11):96-102.