畢業(yè)設(shè)計（論文）電力負(fù)載的無功測控電路設(shè)計

1、長江大學(xué)畢業(yè)論文（設(shè)計）題目名稱：電力負(fù)載的無功測控電路設(shè)計 題目類型： 畢業(yè)設(shè)計 學(xué)生姓名： 院（系）： 電子信息學(xué)院 專業(yè)班級： 指導(dǎo)教師： 時間： 2010年4月1日至2010年5月23日 目錄畢業(yè)設(shè)計任務(wù)書.i文獻(xiàn)綜述ii指導(dǎo)老師審查意見答辯會議記錄評閱教師評語中外文摘要長江大學(xué)畢業(yè)設(shè)計(論文)任務(wù)書學(xué)院（系）電子信息學(xué)院 專業(yè) 儀器 班級 10601 學(xué)生姓名 指導(dǎo)教師/職稱 1. 畢業(yè)設(shè)計(論文)題目：電力負(fù)載的無功測控電路設(shè)計2. 畢業(yè)設(shè)計（論文）起止時間：2010年03月01日2010年6月10日3畢業(yè)設(shè)計(論文)所需資料及原始數(shù)據(jù)（指導(dǎo)教師選定部分）1.基于msp430系列單

2、片機(jī)的智能無功補(bǔ)償控制器 2. 關(guān)于低壓無功補(bǔ)償裝置的探討 3. 配電系統(tǒng)無功補(bǔ)償技術(shù)方案比較 4.電網(wǎng)功率因數(shù)的測量及無功自動補(bǔ)償控制 4畢業(yè)設(shè)計(論文)應(yīng)完成的主要內(nèi)容了解實際電力負(fù)載的功率因數(shù)低的特性，分析由此造成的供電與用戶的影響與損失。運用學(xué)過的知識，用電壓，電流互感器進(jìn)行發(fā)電機(jī)與電網(wǎng)的電壓.電流.功率及相位的測量。運用單片機(jī)作比較計算并進(jìn)行無功補(bǔ)償（并聯(lián)電容）。5畢業(yè)設(shè)計(論文)的目標(biāo)及具體要求5.1.配電系統(tǒng)無功補(bǔ)償?shù)姆治觯?.2. 配電系統(tǒng)無功功率的實用檢測電路設(shè)計；5.3.無功補(bǔ)償?shù)耐肚锌刂疲?.4. 配電系統(tǒng)無功補(bǔ)償?shù)谋Ｗo(hù)電路。6、完成畢業(yè)設(shè)計(論文)所需的條件及上機(jī)時數(shù)要

3、求計算機(jī)圖書館的各種圖書及雜志網(wǎng)上數(shù)據(jù)庫上機(jī)150學(xué)時任務(wù)書批準(zhǔn)日期 2010 年 03 月 01日 教研室(系)主任(簽字) 任務(wù)書下達(dá)日期 2010 年 03月 11日 指導(dǎo)教師(簽字) 龍從玉 完成任務(wù)日期 2010 年6月 10日 學(xué)生（簽名） yangtze river university wen wen xian graduates of comprehensive statetitle name: reactive power load measurement and control circuit design department: electronic informati

4、onprofessional-level classes: instrument 10 601 student name: wang lin hua teach teachers: long congyu-teacher completion date :2010-5-3 reactive power load measurement and control circuit design literature review student: wang linhua, electronic information instructor: long congyu , telecommunicati

5、ons institute fist. introduction i wrote this article is to introduce the current status of power system and power compensation in power system problems. mainly related to the power system reactive power compensation in the area. reactive power load measurement and control circuit design literature

6、review low-voltage reactive power compensation reactive power load is an important part of compensation. improve low-voltage compensation, not only can reduce the level of reactive power compensation on the pressure, but also improve the utilization of the user distribution transformers to improve p

7、ower factor and voltage quality of the user, and can effectively reduce power losses, thus reducing electricity bills . reactive power compensation and power supply departments of user benefit. existing reactive power compensation device type a lot, but basically by the detection unit, control unit,

8、 execution units, and power component. the task detection unit is detected from the network and network power factor directly or indirectly related to the parameters, and to give as gifts this parameter signals and control unit, the control unit to be compared with the control target value. make swi

9、tching decisions. implementation unit is based switching decisions by switching switch (ac contactor) control of capacitor switching, compensation to complete the task.second, the main at present, the low voltage reactive power compensation devices are static and dynamic compensation device compensa

10、tion of two, the control method are: power factor control, reactive power (or reactive current) control and other control methods. static and dynamic reactive power compensation reactive power compensation. static var compensator svc means that when the reactive changes, control changes to control t

11、he capacitor according to the group switching to achieve the required reactive power compensation, the response normally greater than 5 seconds. capacitor switching is accomplished by the contactor, due to capacitor inrush current withstand capability and the discharge time, capacitor grade, contact

12、ors operating frequency, life and other factors, so there is much to be desired: ( 1) there is a level of compensation, timing, and thus compensation accuracy, the time when the load changes frequently (such as rolling, high-power electric furnace, etc.), to follow is not strong. (2) the input capac

13、itor can be no surge. for contactor + reactor program, a larger increase in losses for capacitive touch device program, a high accident rate, but also a great influence on the life of the capacitor. (3) run noisy. (4) as part of the load control contactor coil is in the switching process, will produ

14、ce sparks and high harmonics, resulting in interference, affect the compensation device reliability and service life. static reactive power compensation equipment and some use of composite switch as the closing and breaking circuit current component, which uses silicon and contacts (or high-capacity

15、 relays) in parallel, when you need input capacitor, the first by the scr conduction circuit, no inrush current into the capacitor, and then contacts (or high-capacity relays) conduction circuit, controllable silicon out of operation. removal of the action when the capacitor is the opposite order. b

16、ecause of the inherent characteristics of the components used, limitations, when the controller detects reactive change needs switching capacity of the capacitor must, we must delay a certain time (response time greater than 5 s) for switching. therefore, static reactive power compensation is a long

17、er delay switching for reactive compensation. in addition, the operation was found, due to high current flows through the relay contacts regularly, and frequent switching, make contact burning, bonding occurs. relay contacts will occur shake off timely, high harmonic generation, on the controller to

18、 work greater impact. dynamic reactive power compensation (thyristor switched capacitor tsc): as the svc is kind of long-latency switching method, which is determined by its reactive change frequently and vary greatly in the case, can not meet the requirements. in modern power electronic devices and

19、 digital control technology support, with fast switching capability of dynamic reactive power compensation device can quickly. tracking compensation of reactive power changes. static and dynamic compensation equipment circuit structure is the same, but the dynamic compensation is dynamic compensatio

20、n controller to control the fast-pass thyristor .broken, no surge in power capacitor switching. reactive power regulator replaced electromagnetic ac contactors to change this component, making the performance of the compensation device has been a qualitative leap to a capacitor bank switching time r

21、educed by a few hundred milliseconds to 20,30 ms . that is, l 2 個 a cycle is complete a capacitor bank switching, so do the amount of reactive power compensation can quickly follow changes in actual demand. as the reactive power regulator is a non-contact capacitive switch long life, so that no surg

22、e capacitors impact the process of investment, no operating over-voltage, arc-free capacitor renewed removal process, the whole long life, maintenance of small and can be removed in the capacitor after the discharge to any what input voltage again. frequent switching capacitor can be divided into ph

23、ase compensation. power factor control and reactive power (reactive current) control whether static var compensation, or the dynamic reactive power compensation, require a controller to complete the network parameters of the measurement, control capacitor banks switching. most of static reactive pow

24、er compensation device is a contactor switch element, the controller issued a traffic signal switches to control contactors or off closing open. dynamic reactive power compensation device to thyristors as switching elements, the controller issued a trigger signal to the thyristor. reactive power com

25、pensation device has power factor control and reactive power (no reactive current) control in two ways, each of the following features: power factor control power factor control is to meet the requirements for power factor control objectives, so that the grid power factor to meet the requirements. p

26、ower factor controller on the grid voltage and current sample testing, analysis and calculation of power by the current value, with the current power factor values with the switching threshold set for comparison to determine whether investment, removal of capacitors, or maintaining the status quo un

27、changed. suppose the power factor before compensation 0.9. when the input threshold is set to = 0.9, the controller detects the current power factor is less than 0.9, to issue instructions, input of a compensation capacitor. if the compensated power factor 0(負(fù)載呈感性) =t-t/2= =0(負(fù)載呈阻性) 0(負(fù)載呈容性) 功率因數(shù)的計算

28、：為使cpu有能力和時間實施自診斷和二次開發(fā)，本文對cos 的運算采用查表技術(shù)c設(shè)市電工頻5o hz(周期20ms)，t=10ms，則cos=c0弧節(jié) cos*t=cos（*t/t-/2）事先離線使 按一定步長 遞增，并由上式計算得tcos查詢表，存人eprom。其中把t折算為地址，地址內(nèi)容為cos 值。這樣當(dāng)采樣回路測得 時，就可將其轉(zhuǎn)化為地址，查表即得對應(yīng)的cos 。過程論述理解關(guān)于無功功率補(bǔ)償?shù)膸讉€概念1.1 正弦交流電中的無功功率定義正弦電流中的無功功率定義為: 習(xí)慣上認(rèn)為它是由電路中的儲能元件(電容或電感)引起。在交流電一個周期的一部份時間內(nèi)，儲能元件從電源吸收能量，另一部時間內(nèi)將能

29、量返回電源，理想的無損失儲能元件在整個周期q平均功率是零。也就是說在外電路和電感或電容之間雖有能量的來回交換，但在儲能元件上并沒有能量的消耗。無功功率與儲能元件相關(guān)聯(lián)。我們可計算功率因數(shù)： 1.2 電力系統(tǒng)中無功功率及功率因數(shù)電力網(wǎng)除了要負(fù)擔(dān)用電負(fù)荷的有功功率p，還要負(fù)擔(dān)負(fù)荷的無功功率q。 無功功率o和視a功率s之間存在下述關(guān)系: 然而：被定義為電力網(wǎng)的功率囚數(shù)，其物理意義是線路的視在功率s供給有功功率的消耗所占百分?jǐn)?shù)。在電力網(wǎng)的運行中，我們所希望的是功率因數(shù)越大越好，如能做到這一點，則電路中的視在功率將人部分用來供給有功功率，以減少無功功率的消耗。1.2.1 如何提高電力系統(tǒng)功率因數(shù)功率因數(shù)

30、還可以表示成個述形式:注：u:為線電壓，l為:線電流。 可見，在一定的電壓和電流卜，提高cos，其輸出的有功功率將增大。因此，改善功率因數(shù)是充分發(fā)揮沒備潛力，提高設(shè)備的利用率的有效方法。1.2.2 補(bǔ)償電容以減少線路損失電力網(wǎng)的電壓損失可以表示為: 可看出，影響u的因數(shù)四個:線路的有功功率p、無功功率o,電阻r和電抗x。如果采用容抗為x。的電容來補(bǔ)償，則電壓損失為:故采用補(bǔ)償電容提高功率因數(shù)后，電壓損失u減小，改善了電壓質(zhì)量。電力系統(tǒng)無功補(bǔ)償?shù)脑?2. 3. 1配電網(wǎng)無功補(bǔ)償問題的提出 在電力系統(tǒng)中，由于電感、電容元件的存在，不僅系統(tǒng)中存在著有功功率，而且存在無功功率。雖然無功功率本身不消耗

31、能量，它的能量只是在電源及負(fù)載間進(jìn)行傳輸交換，但是在這種能量交換的過程會引起電能的損耗。并使電網(wǎng)的視在功率增大，這將對系統(tǒng)產(chǎn)生以下一系列負(fù)面影響:(1) 電網(wǎng)總電流增加，從而會使電力系統(tǒng)。中的元件，如變壓器、電器設(shè)備、導(dǎo)線等容量增大，使用戶內(nèi)部的起動控制設(shè)備、量測儀表等規(guī)格、尺寸增大，因而使初投資費用增大。在傳送同樣的用功功率情況下，總電流的增大，使設(shè)備及線路的損耗增加，使線路及變壓器的電壓損失增大。(2) 電網(wǎng)的無功容量不足，會造成負(fù)荷端的供電電壓低，影響正常生產(chǎn)和生活用電;反之，無功容量過剩，會造成電網(wǎng)的運行電壓過高，電壓波動率過大。(3) 降低了電網(wǎng)的功率因數(shù)造成大量電能損耗，當(dāng)功率因數(shù)

32、由0.8下降到0.6時，電能損耗將近提高了一倍。(4) 對電力系統(tǒng)的發(fā)電設(shè)備來說，無功電流的增大，對發(fā)電機(jī)轉(zhuǎn)子的去磁效應(yīng)增加，電壓降低，如過度增加勵磁電流，則使轉(zhuǎn)子繞組超過允許溫升。為了保證轉(zhuǎn)子繞組正常工作，發(fā)電機(jī)就不允許達(dá)到預(yù)定的出力。此外，原動機(jī)的效率是按照有功功率衡量的，當(dāng)發(fā)電機(jī)發(fā)出的視在功率一定時，無功功率的增加，會導(dǎo)致原動機(jī)效率的相對降低。目前，隨著電力電子技術(shù)的迅速發(fā)展，工廠大量使用大功率開關(guān)器件組成的設(shè)備對大型、沖擊型負(fù)載供電，這使電能質(zhì)量問題日益嚴(yán)重。如果，不進(jìn)行無功補(bǔ)償，在正常運行時，會反復(fù)地使負(fù)載的無功功率在很大的范圍內(nèi)波動，這不僅使電氣設(shè)備得不到充分的利用，網(wǎng)絡(luò)傳輸能力下

33、降，損耗增加，甚至還會導(dǎo)致設(shè)備損壞、系統(tǒng)癱瘓。2.3.2 無功補(bǔ)償向量圖在工業(yè)和生活用電負(fù)載中，阻感負(fù)載占有很大的比例:異步電動機(jī)、變壓器、螢光燈等都是典型的阻感負(fù)載。異步電動機(jī)和變壓器所消耗的無功功率在電力系統(tǒng)所提供的無功功率中占有很高的比重。電力系統(tǒng)的電抗器和架空線等也要消耗一些無功功率;同時，各種諧波源也要消耗一定的無功功率。阻感負(fù)載可看作電阻r與電感l(wèi)串聯(lián)的電路，其功率因數(shù)為 無功功率測控電路總體設(shè)計思路該無功補(bǔ)償器是以無功功率為判斷依據(jù)。如何進(jìn)行無功補(bǔ)償？設(shè)定系統(tǒng)所需要達(dá)到的無功功率要求，通過對系統(tǒng)的無功功率的檢測，并以此作為是否補(bǔ)償無功的標(biāo)準(zhǔn)。處理所采集的數(shù)據(jù)。顯示當(dāng)前系統(tǒng)的狀態(tài)參

34、數(shù)，如何保護(hù)補(bǔ)償裝置？怎樣處理高壓和低壓的電氣連接所產(chǎn)生的干擾和抑制諧波？重點就是如何測量無功功率，如何投切電容？總的解決方法是將無功補(bǔ)償分為三個組成部分，功率因數(shù)自動調(diào)節(jié)器執(zhí)行機(jī)構(gòu)調(diào)節(jié)對象該無功設(shè)計思路：通過互感器采集數(shù)據(jù)，經(jīng)過組合電路對電壓與電流的過零比較產(chǎn)生其相對落后時間查 差，送入單片機(jī)，進(jìn)行分析，計算，判斷，對執(zhí)行機(jī)構(gòu)進(jìn)行控制無功的投入與切除。這樣就可以實現(xiàn)對負(fù)載的無功補(bǔ)償。 該無功補(bǔ)償器為單相補(bǔ)償。3.1 無功功率補(bǔ)償原理圖無功檢測電容組負(fù)載為單環(huán)閉合回路，當(dāng)設(shè)定參數(shù)則可以自動調(diào)節(jié)無功功率，無功檢測的數(shù)據(jù)與設(shè)定值的比較結(jié)果決定電容組的投切。3.2單相無功補(bǔ)償?shù)脑?.3無功補(bǔ)償?shù)目?/p>

35、圖：電壓傳感器a/d轉(zhuǎn)換 單片機(jī)開關(guān)投切控制電路電容組投切光隔離復(fù)合開關(guān)電流傳感器功率檢測電路顯示eeprom 硬件電路的設(shè)計硬件電路分為三大塊：采樣系統(tǒng)，控制系統(tǒng)，執(zhí)行系統(tǒng)。分別分擔(dān)各自的必要功能并構(gòu)成一個完整的無功補(bǔ)償電路。4.1采樣系統(tǒng) 該無功補(bǔ)償器是以無功功率為判斷依據(jù)而進(jìn)行無功的投切。無功補(bǔ)償器關(guān)鍵在對無功功率的采集，樣無功功率因數(shù)。4.1.1 功率因數(shù)的測量4.1.1.1信號調(diào)理電路的設(shè)計信號調(diào)理電路主要完成強(qiáng)電信號與弱電信號之間的隔離和變換，該電路包括互感器信號轉(zhuǎn)換電路、1)互感器信號轉(zhuǎn)換電路選擇帶8位的ad轉(zhuǎn)換器，其ad轉(zhuǎn)換的域值電壓為33 v，其最大轉(zhuǎn)換時間為。因此對于選擇的

36、交流傳感器，其采樣精度應(yīng)與選擇帶8位的ad轉(zhuǎn)換器采樣精度相匹配。另外，電壓、電流傳感器的功用主要在于從主電路上適當(dāng)?shù)闹坊蚬?jié)點處對其電壓或電流值進(jìn)行采樣，并將控制電路與主電路進(jìn)行隔離。因此，傳感器的選取就要考慮到主電路及控制電路的電壓(或電流)等級。對于容量為100 kvar，電壓等級為380 v220 v的三相靜止補(bǔ)償器，所需的電流參數(shù)為系統(tǒng)對電網(wǎng)的輸出無功電流參數(shù)，因此，選用北京星格公司研制的精密電壓傳感器spt304和精密電流傳感器sct260sh304是一款電壓輸出型精密電壓傳感器，其額定輸人為380 v，額定輸出為125 v，線性范圍為0450 v，最大輸人電壓為570 v，精度為0

37、2(一40+75)，相移5度sct2601是一款電流輸出型精密電流互感器，其額定輸人為600 a，額定輸出為100 ma，線性范圍為0720 a，非線性度01 ，相移05。(補(bǔ)償前)。使用電路如圖2所示，互感器副邊電路為電流電壓變換電路，調(diào)節(jié)圖中反饋電阻r和r的值可得到所需的電壓輸出(一125 v+125 v)：電容c2是400至1 000 pf的小電容，用來去耦、濾波和相位調(diào)節(jié)。2) 采集功率因數(shù)的電路將比較器輸出的兩路矩形波信號u1和u2經(jīng)與門74ls08相與，輸出波形再同u1一起送異或門74ls86，其輸出波形即顯示了相位差角的大?。▓D2-1）。然后將信號輸入89c51單片機(jī)的int0口。先通過軟件對寄存器ie賦值，使int0口關(guān)中斷。這是因為，定時器/計數(shù)器0檢測89c51的int0口，通過定時器工作方式寄存器tmod來控制定時器/計數(shù)器0的工作方式和操作模式，通過定時器控制寄存器tcon來控制它們的工作狀態(tài)。由于程序需要當(dāng)int0腳由低電平變?yōu)楦唠娖綍r，定時器/計數(shù)器0開始計時，為了消除外部干擾，須先將int0口關(guān)中斷。定時器/計數(shù)器0選擇工作方式一，將定時器工作方式寄存器tmod