Intelligent Design of Low Voltage Side Circuit in Active Electronic Current Transformer英语论文.doc

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1、Intelligent Design of Low Voltage Side Circuit in Active Electronic Current TransformerABSTRACTWith the development of power industry and the increase of voltage level, many problems of electromagnetic current transformer had emerged, thus the concept of electronic current transformer was proposed b

2、y International Electro-technical Commission (IEC) in order to solve those questions. Thereinto, the active electronic current transformer is considered as the most feasible. However, many disadvantages such as high cost, low generality and intelligence were encountered when using Normal Integrated

3、Circuit in the low-voltage side. A new designing method of low-voltage side circuit is introduced in this paper. It takes advantage of Digital Signal Processor（DSP）s powerful data process ability to realize precise analysis and data processing. Moreover, the periphery circuit of this method is much

4、simpler than above methods. Some particular functions such as frequency measurement and harmonic analysis could also be provided by using this method. The functions of local display and remote communication could be selected in accordance with requirement. The measuring result indicates that the rat

5、ion error satisfies the national standard of 0.1 class transformer. And this method is quite general for its flexibility of the numbers of monitoring parameter in the high-voltage side and the bits of analog-to-digital convert.KEYWORDS: Electronic current transformer, DSP, Frequency measurement, Har

6、monic analysisINTRODUCTIONAs an important part of protecting and metering systems, the accuracy of current transformer is strongly relative with the security and reliability of power system.Conventional electromagnetic current transformers (CT), which are now frequently used in the power system, cou

7、ld ensure the accuracy and reliability required for metering and protection. But with the problem of difficult insulation and the effect of the saturation, the conventional current transformer is more and more unfit for the development of modern power system.Then many measurement techniques have bee

8、n developed in order to solve above disadvantages of conventional current transformers. Recently, many achievements have been acquired in the optical current measurement field due to the appearance of integrates circuit and the fiber transmission. After investigation and analysis of the present curr

9、ent measurement methods, the concept of electronic current transformer (ECT) was proposed by IEC. According to the definition of IEC, the sensor of electronic current transformers can be conventional current transformer, Rogowski coil or optical device. The new electronic current transformers could

10、be divided into active ECT and inactive ECT. And the difference is illustrated as following.If the optical device is utilized in the electronic current transformer, the signals can be acquired and transmitted in the high voltage side without power supply, thus it is the inactive electronic current t

11、ransformer. And the other name is Optical Current Transformer. But there is a long way to go before this transformer can be put into practice since the accuracy of the transformer is likely to be affected by the circumstance and material. On the other hand, the active electronic current transformer

12、cant work without power supply. And the construction of the system is shown in Fig.1.Low voltage circuitHigh voltage circuitFiber TransmissionPower supplyHigh voltage side circuitLow voltage side circuitFig.1 Construction of the systemAs shown in Fig.1, there are three parts in the ECT, which are th

13、e high voltage side circuit, optical transmission part and low voltage side circuit. For the application of the optical fiber in the signal transmission between the high voltage side circuit and the low voltage side circuit, the ECT has many advantages such as simple and reliable insulation structur

14、e, perfect Electro-magnetic anti-interference ability, no Electro-magnetic saturation problem, light weight and easy interface with other digital device, etc. After many years study in the active electronic current transformer, great progress has been made in this sort of ECT. In order to adapt the

15、analog devices and instruments, the output of low voltage system of this ECT mostly is analog voltage signals, which is counteract the development of the digital current transformer. In this paper, a Motorola DSP is used in the design of low voltage side circuit of active ECT, and then the advantage

16、 of DSPs powerful data process ability and the advanced technology of program have been taken in the low voltage of ECT in order to realize precise analysis. In addition to the function of frequency calculation and the simple structure, the output of ECT is digital signals . Because of above charact

17、eristics, this ECT will be superior to many other ECTs. And the automatic level of power system could be improved by using this method.SYSTEM DESIGNThe low-voltage side circuit is designed to deal with the optical signals that are transmitted by optical fiber from high-voltage side circuit. Besides

18、the optoelectronic converters and the control circuit, the main element of the low-voltage side circuit is a digital signal processor (DSP) unit, including data collection and separation, signal processing, display and transmission. In order to process optical signals successfully, we should know th

19、e characteristics of signals derived from the high-voltage side circuit. In this ECT, two fibers are utilized to connect the high-voltage side circuit and the low-voltage side circuit , one fiber is utilized to transmit data signals, and the other one is used to carry synchronous clock signals.Four

20、different detecting parameters are converted into digital signals in this high-voltage side circuit, they are multiplied in single fiber, and then to be transmitted to the low-voltage side circuit. The first parameter in this serial signal is the temperature of the circumstance, and then is the prot

21、ecting current signal and the measuring current signal, the decuple measurement current signal, which is used in weak signal test, is the last one. There is a time interval of 64s between two group signals , and the time interval between different parameters of the same group is about 10s.HARDWARE D

22、ESIGNWe will distinguish every signal according to above characteristics. The structure of the low-voltage side circuit is shown in Fig2. As an optical signal receiver, HFBR-2412 is introduced in this system in order to convert optical signal into electrical signal in the low-voltage side circuit.Co

23、mmunication with PCDSPControl signalOpto-electric converterHigh-voltage side circuitclockfiberclockLocal DisplaydatedateLow voltage side circuitFig2. Structure of systemA control signal is triggered as a synchronization signal of DSP in this circuit.Many internal peripherals are selected in the desi

24、gn, such modules as Serial Peripheral Interface (SPI), Asynchronous Serial Communication Interface (SCI) and General Purpose Input/ Output (GPIO). The functions of above modules are listed below:1 SPISPI is multiplied in the low voltage circuit. Data collection and separation could be achieved by th

25、is interface when the DSP is configured as a server mode. This is an outstanding character in my design. And local display could also be driven by using this Interface, but at this time the DSP is configured as a master.2 SCIThe acquired original data and the calculating results of DSP should be tra

26、nsmitted to computer via the SCI. The calibration of the ECT and the monitor of the DSP could also be realized via communication between the computer and the DSP.3 GPIOThis pin, which is used as one of the address bus, can also detect the symbol of the first parameter of the compound signals , and t

27、hen it will help SPI to separate signals successfully.SOFTWARE DESIGNData collection and process could be realized in this part, and then the results should be displayed locally or transmitted remotely which can be selected at last. Of course, many special functions such as frequency measurement, fl

28、exible multi-parameters processing and harmonic analysis, can also be provided.In software design, the interrupt of the GPIO should be detected before the data is collected in the DSP. And the result of the last time will be selected in location display or long-distance transmission before data proc

29、essing has been finished. Interrupt 1 is an external interrupt, when the interrupt 1 is opened and triggered the program will enter the interrupt 1 service routine, then the results of the FFT and the collected data will be sent to the computer; interrupt 2 is a GPIO interrupt, which makes sure that

30、 the compound data can be read by the DSP in order. After display the results of FFT, a new loop will begin. In order to improving the accuracy of the system, temperature compensation algorithm will be introduced at the end.Some functions such as frequency measurement and harmonic analysis could als

31、o be provided in this part. Because of the fixed time interval between every data of D/A convert, we can get the frequency of input signal by calculating the numbers of the data in one cycle. And the harmonic analysis is possible by using FFT methods. In general, all these intelligent characters in

32、this paper such as adjustable number of parameters or the bits of AD component could be achieved due to the application of the DSP in the low-voltage side circuit.MEASUREMENT RESULTSThe accuracy of testing system has been calibrated by virtual instrument. The measurement results of system are shown

33、in Table 1. The output of the virtual instrument is the true value, while the output of the DSP is the testing value.Table1 Measurement resultsMeasuring point(%)True value(V)Test value(V)Ratio(%)Ratio(%)50.06070.0605-3.236-0.330200.23620.2363-0.3290.0591001.21241.21270.3430.0261201.48971.48940.330-0

34、.0181. Original ratio error2. Ratio error after line fitting.ERROR ANALYSISIn order to improve the system accuracy, the ratio error in the small signals should be decreased. Although ratio accuracy of 0.1 class can be met at the 120% of measuring range in the system, the ratio error is still increas

35、ing, which may be caused by exceeding valid converter range of A/D chip.CONCLUSIONSA new active electronic current transformer is presented in this paper. Motorola DSP, the hard core of the system could finish the requirement of the data collection, signal separation and data processing, and many in

36、telligent functions such as frequency measurement and harmonic analysis could also be achieved by using its strong data processing ability. The testing results show that the ratio error of above method satisfies the national standard of 0.1-class transformer.英语谚语警句100句精选Proverbs are the daughters of

37、 daily experience.谚语是日常经验的结晶。1. Look before you leap./Second thoughts are best. 三思而后行。/再想而后行。2. Great minds think alike; (heroes have similar views.) 英雄所见略同。 3. We shall never have friends if we expect to find them without fault.欲求完美无缺的朋友必然成为孤家寡人。4. What you sow, you must mow. 种瓜得瓜，种豆得豆。5. A beggar

38、can never be bankrupt.天无绝人之路。6.A friend in need is a friend indeed.患难见真情。7. No news is good news. 没有消息就是好消息。8. No cross, no crown. 不经历风雨,怎么见彩虹。9. The more haste, the less speed. /Haste makes waste.欲速则不达。10. Victory belongs to the most persevering. 坚持就是胜利！11. A young idler, an old beggar. 少壮不努力，老大徒伤悲

39、。12. Put ones foot in ones mouth. 说话不得体。13. It is no use crying over spilt milk.覆水难收/悔恨已晚/木已成舟,回天乏力。14. Content is better than riches. 知足常乐。15. No gains without pains. 没有辛苦就没有收获。16. The more a man knows, the more he is inclined to be modest. 大智若愚。17. All roads lead to Rome .条条大路通罗马。18. A snow year,

40、a rich year. 瑞雪兆丰年。19. Never say die! 永不言败！20. The best mirror is a friends eye. 朋友的眼睛是最好的镜子。 21. Faith will move mountain. 精诚所至，金石为开。 22. A life without a friend is a life without a sun. 人生没有朋友，犹如生活没有了太阳。 23. Great wits have short memories.贵人多忘事。 24. Do well and have well. 善有善报。25. A bad thing neve

41、r dies. 坏事传千年。26. Four eyes see more than two. 人多识广/集思广益。27. Diligence is the parent of success. 勤劳是成功的根本。28. Water dropping day by day wears the hardest rock away.滴水穿石。29. Hope for the best, but prepare for the worst. 抱最好的愿望，做最坏的打算。 30. While there is life, there is hope. /Debt is better than death

42、. 留得青山在，不怕没柴烧。/有生命就有希望。31. Where there is a will, there is a way. 功夫不负有心人。/有志者事竟成。32. Where there is great love, there are always miracles. 哪里有真爱存在，哪里就有奇迹。33. Where there is smoke, there is fire. 无风不起浪。34. One boy is a boy, two boys half a boy, three boys no boy.一个和尚挑水喝，两个和尚抬水喝，三个和尚没水喝。35. A stitch

43、in time saves nine. 及时缝一针能省九针。/小洞不补，大洞吃苦。36. Never too old to learn, never too late to turn. 亡羊补牢，为时不晚。37. Dont claim to know what you dont know. 不要不懂装懂。38. Do in Rome as Roman do. 入乡随俗。39. Rome was not built in a day. 冰冻三尺，非一日之寒。40. Sharpening your axe will not delay your job of cutting wood. 磨刀不误砍

44、柴工。 41. Things of a kind come together, people a mind fall into a group. 物以类聚,人以群分。 42. One mans meat is another mans poison. 萝卜白菜,各有所爱。43. like author like book.文如其人。46. Like for like. 惺惺相惜。47. Like teacher like pupil. 有其师必有其徒。48. Gods that run many hares kill none.贪多必失。49. Practice makes perfect.

45、熟能生巧。50. Actions speak louder than words. 行胜于言。51. You cannot eat your cake and have it. 鱼与熊掌，不可兼得。52. One loses by pride and gains by modesty. 满招损,谦受益。53. Love me, love my dog. 爱屋及乌。54. An apple a day keeps the doctor away. 每日一苹果远离医生。55. Time past cannot be called back again. 时光不倒流。56. A drop of wa

46、ter cannot make a sea, and a tree cannot make a wood. 滴水不成海，独木不成林。57. If you venture nothing, you will have nothing. 不入虎穴,焉得虎子。58.The tree is known by its fruit. 观其行知其人。59. All work no play makes Jack a dull boy. 只会用功不玩耍,聪明的孩子也变傻。60. The pot calls the kettle black. 五十步笑百步。61. Unkindness often reacts

47、 on the unkind person. 恶有恶报。62. Todays work should never be left over till tomorrow. 今日事今日毕。63. Nothing so bad but might have been worse. 塞翁失马,焉知非福。 64. God helps those who help themselves. 自助者天助。65. Complacency is the enemy of study. 学习的敌人是自己的满足。66. A fox may grow gray, but never good.江山易改，本性难移。67.

48、 A friend without faults will never be found. 没有十全十美的朋友。68. A good beginning is half done. 良好的开端是成功的一半。69. A good book is the best of friends, the same today and forever. 一本好书，相伴一生。70. A good medicine tastes bitter. 良药苦口。71. A leopard cannot change its spots.积习难改。72. A little knowledge is a dangerous thing. 一知半解，自欺欺人。73. All good things come to an end. 天下没有不散的筵席。74. Justice has long arms. 天网恢恢，疏而不漏。75A man becomes learned by asking questions. 不耻下问才能有学问。76. A man