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基于幅值的电压暂降特征量检测方法

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Smart Grld 第29卷第5期 2013年5月 文章编号:1674—3814(2013)05—0024—06 电网与清洁能源 Power System and Clean Energy Vol_29 No.5 Mav 2013 中图分类号:TM714.2 文献标志码:A 基于幅值的电压暂降特征量检测方法 付学 谦1,陈皓勇,,黄良毅2 (1.华南X_r-大学电力学院,广东广州 510640;2.海南电网公司调度通信中心,海南海口570003) Detection Method of Voltage Sag Characterizations Based on Peak Value FU Xue—qian ,CHEN Hao—yong。,HUANG Liang-yi (1.School of Electirc Power,South China University of Technology,Guangzhou 510640,Guangdong,China;2.Dispatching and Communication Center,Hainan Power Grid Corporation,Haikou 570003,Hainan,China) ABSTRACT:After studying the existing detection methods for voltage sag characterizations,a new voltage—sag detection technique based on the peak value is put forward.Through a low-pass filter,phase locking and a square root circuit,the amplitude of the fundamental wave of sagging voltage can be voltage sag as the effective value of power frequency voltage somewhere in system sud denly drops down to 10%一90%of its rating value and recovers to normal state in the following 10 ms~l min.Short duration of voltage sag can cause irreversible damage to sensitive equipment and impose signiicantf economic calculated quickly and then the angle of a phase jump can be calculated quickly accordingly.Compared with the dq transform losses due to unexpected interruptions of industiral method widely used in DVR devices,this method can obviously reduce the delay time and determine the voltage sag characteriza- tions quickly and accurately as wel1.The results of MATLAB simulation results very the validity of the methods. production process.The economic loss caused by voltage sag in USA is about 12 ̄26 billion dollars every ye . KEY WORDS:voltage sag;power quality;peak value Voltage sag is regarded as the most harmful power quality disturbance which effects the safe operation of power equipments.The harm caused by voltage sag in modern society mainly includes the 摘要:分析了现有的电压暂降检测方法,提出了基于幅值的 电压暂降特征量检测新方法。该方法通过低通滤波器、根锁 相和开平方等环节可快速推导出暂降基波电压的幅值,然后 根据暂降基波电压幅值快速推导出相位跳变角。与DVR装置 中广泛采用的瞬时电压d口分解法比较,该方法的延时明显减 少,可以对电压暂降的特征量进行迅速、准确判断。MATLAB 仿真结果证明了该方法的有效性。 following four aspects: 1)a great impact on people’s daily life; 2)a damaging impact on IT industy,aboutr 80% of senrers down and 45%of clients’data loss or error are related to voltage sag; 关键词:电压暂降;电能质量;幅值 3)a great harm on sensitive industrial users; Voltage sag is the situation where the effective 4)a great impact on electircal devices widely used in modem society. In order to assess the influence of voltage sags accurately,a new sensitivity evaluation method for value of vohage drops down sharply and then recovers in a short period of time,which often lasts 0.5 cycles to 1 minute in power systemt”.IEEE standard defines sensitive equipment based on fuzzy theory due to voltage sags is proposed in paperI31. 基金项目:国家高技术研究发展计划(863计划)资助项目 (2012AA050201)。 Voltage sag is always companied by a phase Project Supported by the National Hi sh Technology Research and Development Program of China(863 Program)(2012AA050201). jump,which most equipments are not sensitive to. However,to those power electronic converters whose Smart Grid 第29卷第5期 电网与清洁能源 trigger time is decided by phase information,a phase jump will do great harm to their normal operation.A phase jump is often caused by the unbalance in three phases.As a result,both the amplitude of voltage sag and L the angle of phase jump must be measured accurately. Several approaches have been proposed in the foreign literature for voltage sag detectiont4 ̄1.Voltage measurement is often expressed in rms values.The disadvantage of the rIBS method is that a window of historical data has to be obtained,processed and then only can a mitigation signal be sent to the hardware. Limitations associated with this method are discussed in .d-q transform is widely applied in DVR, which transforms the three phase voltage in abc frame to d—q frame.The d-q transform only suits for three phase symmetrical voltage.Other two virtual phase voltage can be constructed from the sagged phase voltage,but delay of a quarter of period time will be inevitablet。”. A new voltage-sag detection technique based on the peak value is described in this paper.Through a low-pass filter,phase locking and a square root circuit,the amplitude of the fundamentla wave of sagging voltage can be calculated quickly while the angle of a phase jump can also be calculated quickly according to this.Compared to the d—q transform method widely used in DVR devices,this kind of method can decrease delay time obviously and can decide the vohage sag characterizations quickly and accurately as wel1. Peak Value Evaluation Method The peak voltage can be used to record voltage sag.THE following equation can be used to calculated voltage sag: Umak=maxI (t— )I (1) O<r<l Where u(t)is the sampled waveforln,and T is an integer of one half cycle .The value of is compared with reference voltage value to determine whether voltage sag Occurs or not. 2 Transient voltage d-q decompo- sition In the case of a symmetric three——phase three—— wire circuit,it provides a three-phase voltage waveform with the same waveform,each 120 electrical degrees apart.Single—phase power can be constructed as a vitrual three-phase system.Taking a phase voltage na as the reference,other two virtual phase voltage are delayed in time by one-third and two——thirds of one cycle of the electric current.It delays 60。as“ ,then ub 一 — c・ Transform the three-phase voltage to the d-q axis. Ⅱ c /zb (2) c sin∞ sin 号盯)sin 吾丌) …s —s 百)-… 号盯) (3) Where sin tot,cos tot is the sine and cosine signal in the same phase with the grid voltage before the disturbance by a PLL and a sine,cosine signal circuit. After transformation,the original fundamental positive sequence component corresponds to DC component.Using low-pass filter to the direct flow from the d—q axis component,as 【 ] (4) Where is the RMS value of voltage sag,o/is the angle of phase hop.The value of voltage sag and the angle of phase hop can be calculated by the DC component of d—q axis. 3 研 (5) …a ) (6) hTis method requires the virtual three——phase system consturcted from the sagged voltage,so the principle is not simple enough.There is a three—phase transformation process with complex computation. Smart Grid 付学谦,等:基于幅值的电压暂降特征量检测方法 Vol_29 No.5 3 A new method of measuring the Vo Itage sag based on the peak val ue 3.1 Basic theory When voltage sag Occurs on power system,fault signal is often on the basis of the fundamental sinus— oidal superimposed decay of non-periodic component and a large number of high—frequency components. The input voltage signal filtering,pure sinusoidal signal can be obtaine. Voltage signal is assumed ua=Upsin tot (7) Where Ma is the sampling voltage waveform,Up is the amplitude of the voltage sampling.to=2 ̄f,f=50 Hz.M by the derivative can be the cosine signal Ub of the phase voltage b= ot = lp‘ cos(c, (8) If they are sent to two separate multipliers and squared,the following two equations can be obtained, Ual=k sin tot (9) /Zbl=k COS tot (10) Where k is the muhiplication factor of the multipliers. It is easy to obtain the square of the input vohage peak value by adding hte equation(9)and(10) uvl=ua ̄+Ubl 后 sin2 tot+k COS 2 tot= (11) In order to measure the peak value,the signal “p1 is fed to a square root circuit.Then the output of the square root circuit is M = = 。 (12) Where k 1 is the multiplication factor of the square root circuit.If the multiplication factors of the multiplier 低通滤波器 Fig.1 Schematic of the new detection method based on peak value and the square root circuit are selected properly,the value of constant k l can be set as 11 The output voltage of the detector“p2 is equal to the peak value of the input voltage Up.Because the detector is based on the concept of an orthogonal function pair,it is called“orthogonal detector”. Voltage sag is always companied by phase hop, setting the phase angle is 0 after the voltage sag. According to the voltage amplitude measured can be 0btained. si删 cos (14) The angle of phase hop is as, or=O-tot (15) Using trigonometric formulas poor comers available, sin a=sin(0一tot 1= sin 0 cos tot-cos 0 sin tot (16) …rcsi aa eos 一 ~f) (17) This method does not require complex coordinate transformation compared to the transient voltage d—‘q decomposition by greatly reduced computation. 3.2 Error analysis This method is印plied to the derivation of the sine signal,a discrete digital instead of continuous analog is applicated in practical computation, differential discrete digital instead of derivation.The difference of/,t can be expressed as 垒 (18) A卜 0厶 At is small to desirable as (19) Let the sampling period be ,Ts used instead of At. (20) then, 五n ,a=吾 ips1n ∞ 华c。s(£'£ (21) M-M =一b —卫h'ot t=— so2 U= 1 p s cin譬cZ 。0s ott(22) Smart Grid 第29卷第5期 电网与清洁能源 In the case of Ii}1 equal to voltage amplitude is Amplitude tested can be obtained =“:+五}= obtained. 2 (sin 姗 4 sin 丁wT,…2叫 (23)  ̄PTr V=Up4/—sin2— 4 ̄ :toT,2 (24) 刍= f in + sin(mot+O.)l+ / 2 \\一 n  ∞ 一一 The formula of relative error can be generated, ×1o0% (25) 6=I 1一 4 ̄2toT.2 x100% (26) It is clear that, 躲 1—0 ccJ  sin 譬= (27) Therefore,the error caused actual calculation only on the sampling period Ts.As long as Ts is small enough,the error can be controlled to within the required. 3.3 Influence of grid frequency fluctuations For the gad frequency fluctuations, changing to∞1 can be assumed. ∑tl M =Up sin 1t(28) ‰ =to'U.c0s 1£ (29) ,cu .In the case of l equal to 1,the voltage amplitude is obtained. Up2=Up (30) Obviously ura is not equal to Up,the test resuhs by the frequency fluctuations. 3.4 lnfluence of harmonics When the detection voltage contains harmonics, the vohage signal is, “a=∑ sn=l in(nzot+0.) (31) Ub='-Uta/ot=∑ …s(删抖 ) (32) n=l Let Ol is equal to 0,you can a= sin +∑ sin(nxat+0.) (33) n=2 Ub-Up COS ott+ up∑U ncos(nott+O.) (34) /- ̄p(COS ott+ 一。。 (删£+ )l  甜  —r c (O 35) By the formula(35) shows that when the i 一一 nput甜  signal contains harmonics,the measured output voltage will be superimposed voltage irpple. 4 Comparison of Simulation Resul—— tS of Detection By using MATLAB simulation tools,we can 之 .^simulate the situation of the voltage when single——伽{砉抛 。啪珈珈莩。 phase ground short circuit occurs on frequency operation in power system.Simulation parameters are as:u=31 lsin(100wt),voltage sag occurs at =(0.06- 0.10)s.the amplitude of the voltage is 155 V and the angle of phase transition is 30。after the voltage sag. Detection methods are new methods and transient voltage d-q decomposition.Simulation of the voltage sag waveforms and test results are as follows. 00 0.O2 0.04 0.06 0.O8 0.10 0.12 0.14 0.16 0.18 0 20 tls Fig・2 Voltage sag wave form with 30 phase angle jump Figure 3 shows the temporary use of the new method of voltage sag in the value of the results of testing.Figure 4 shows the transient d-q decomposi- tion of the voltage drop in the value of the voltage sag test results.From the simulation curve indicated that the two methods are in the 0.06 s when the detected voltage sag,temporary decline in value around are 155 V.Figure 3 shows the detection of the temporary decline in value,the voltage amplitude sag in the beginning and ending time,there was greater .一  Smart Grid 付学谦,等:基于幅值的电压暂降特征量检测方法 Vo1.29 No5 .350 300 250 2o0 150 100 50 8 Fig.3 Detection resuIt of the voltage sag magnitude using the new detection method 》 S Fig.4 Detection r uIt of the voltage sag magnitude using d-q transform metht ̄l “overshoot”.The reason is that sag in the voltage waveform at the beginning and end time is not continuous,the new method during the derivation, the derivative is not continuous at the mutation Occurs. DVR compensation device works at 90%of the temporary decline in value as the start threshold.New approach detects amplitude from the occu/Tence of occasional drop down to 9O%only 1 ms when transient voltage d-q decomposition detects amplitude from the occurrence of occasional drop down to 9O%3.3 ms. Compensation for the actual DVR time compensation device is 2 ms,so new method can meet real—time DVR compensation device requirements. Figure 5 shows simulation results,deteetion of the phase angle jump into jump from 0。to 30。,then return to 0。or so b ooo 002 o04 0.06 0.O8 0.10 0】2 0.14 0.16 018 02O t|s } ig.5 Detection slIIt of the phasc angle jump of voltage sag using the new detection meth ̄M Detection of the new method of simulation data recorded in the maximum amplitude of the voltage sag is 155.603 921 497 031 and voltage error is 0.603 92 1 497 03 1.The minimum amplitude of the voltage sag is 154.392 1 16 458 543 and the error is 0.607 883 541 457.The maximum relative error of the value of voltage sag is as follows。 ’ig 6 I)etectiun result of the phase angle jump of voltage g using 叫transform method ×100%= 0.607 883 541 457 155 ×lO0%= 0.003 9 (36) M l’LAB simulation results show that the new method based on the peak of the voltage sag detection can accurately and quickly detect the amplitude and phase of the voltage.Practical application of the Dynamic Voltage Restorer compensation time is 2 ms, so transient voltage d——q decomposition can not meet the real——time requirements of DVR compensation device.This new method only applies to the ideal sinusoidal voltage.For severe distortion of the voltage signal we need to increase before the test session a narrowband filter to extract the fundamental signa1. 5 Conclusions The new method based on the peak of the voltage sag detection can quickly detect the fundamental voltage amplitude and phase angle jump through the lock,low-pass filter circuits and other aspects of peaceful evolution.This will improve the DVR compensation effect. The method can be used for single phase and Smart Grid 第29卷第5期 电网与清洁能源 three phase voltage.Single-phase voltage detection does not require construction phase voltage,and the method overcomes the shortcomings that the data is not synchronized of the traditional detection methods, so that the DVR can greatly improve the dynamic response・ Test results are from the impact of changes in grid frequency. References 【1】IEC 61000-2-2 EMC Environment:Compatibility levels for low—frequency conducted disturbances and signalling in public low~voltage power supply systems[S].International Standard,1 990. [2]SHEN Guang,CHEN Yun~ping,Li Xin.Study of distri— bution network voltage sags using a real—time power quality monitoring system[J].High Voltage Engineering, 2006,32(5):97—99. [3]CHEN Ping,YANG Hong-geng.Sensitivity evaluation of sensitive equipment based on fuzzy theory due to voltage sags[J].Power System and Clean Energy,2009,25(6): 23-27. I4】WANG Jin,YANG Chun,LIU Xia,et a1.Simulation and comparison of voltage sag detection algorithms in distribution networks[J].Power System and Clean Energy,2012,28 (3):21—25. [5]HE Yan,ZHANG Hu,MA Li-shan,et a1.Research and simulation of detection of single—phase DVR based on compensation[J].Power System and Clean Eneryg,201 1, 27(1):35—38. 【6】PILlJAY P,BHATI'ACHRJEE A.Application of wavelets to model short—terrn power system disturbances[J].IEEE Transaction on Power Systems,1996,11(4):2031—2037. 【7】WILKINSON W A,COX M D.Discrete wavelet analysis of power system transients[J].IEEE Transaction on Power Systems,1996,11(4):2038—2044. 【8】LIU Yun—chan,HUANG Chun,OU Li-quan.Method for unbalanced voltage sags detection based on dq transform . Proceedings of t he Chinese Society of Universities for Electric Power System and Automation,2007,19(3):721~ 76. [9】XIAO Xiang—ning,XU Yong—hai,Liu Lian—guang.Si~ mulation and analysis of voltage sag mitigation using active series voltage injection[C]#International Conference on Power System Technology.Perth,WA.2000:1317—1322. 『10】TUNABOYLU N S,COLLINS J R E R,CHANEY P R. Voltage disturbance evaluation using the missing voltage technique[CY/8th International Conference on Harmonies and Quality of Power.Athens,1998:577~582. [1 1】ZHANG Qing-chao,XIAO Yu-long.An improved detection method of voltage sag ̄1.Transactions of China Electrotech- nical Society,2006,21(2):123—126. 『121 RAJ NAID00,PRAGASEN PILLAY.A new method of voltage sag and swell detection[J].IEEE Transaction on Power Delivery,2007,22(2):1056-1063. 【13】MUHAMAD MANSOR,NASRUDIN ABDULRAHIM.Vol- tage sag detection a survey【c]//Technical Postgraduates (TECHPOS)2009 International Conference for Digital Object Identiifer.Kuala Lumpu,2009:1—6. 收稿日期:2013—02—12。 作者简介: FU Xue—qian(1985一).was bona in Hebei Province.China.He received the B.S.,M.S.degrees,in the Department of Power Engineering and the Department of Electrical Engineering from North China Electricity Power University(NCEPU)in 2008,201 1,respectively.Now he is pursuing a Ph.D.degree in the School of Electrical Engineering, South China University of Technology,and his research areas of interest include distributed generation systems and power quality analysis; CHENHao-yong(I97 ),(SM’10)was borninHunanProvince, China.He received the B.S.,M.S.and Ph.D.degrees in electircal engineering from Xi’an Jiaotong University,Xi’an,China,in 1995, 1997,and 2000,respectively.He is with the School of Electircal Engineering,South China University of Technology,Guangzhou, China,where he is now a professor.His areas of interest include power markets,power system optimal operation/planning,smart grid,and computational intelligence applications. (编辑冯露) 

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