外文翻譯--實際中的諧波和無功補償

1、<p>　　附錄1：外文翻譯及資料</p><p>　　A1.1實際中的諧波和無功補償</p><p><b>　　總述</b></p><p>　　諧波在全世界的公共和工業(yè)網(wǎng)絡(luò)中呈現(xiàn)一種增長的趨勢。這很明顯的和工業(yè)和商業(yè)大廈中用到的非線性裝載和設(shè)備有關(guān)。這些非線性設(shè)備通常是可控硅整流器或二極管整流器，它們會造成電能質(zhì)量的惡化，通常的

2、以下的幾種應(yīng)用中會用到：</p><p>　　-變速驅(qū)動(VSD)</p><p><b>　　-為制造業(yè)和加工業(yè)</b></p><p><b>　　-金屬工業(yè)中的加熱</b></p><p>　　-大廈中的電梯、空調(diào)泵和風扇</p><p>　　-工業(yè)和商業(yè)大廈中的不間斷

3、電源（UPS）</p><p>　　-計算機和其他一些辦公設(shè)備</p><p>　　表1是典型DC驅(qū)動與6脈沖可控硅整流器整流器和表2是與6脈沖二極管整流器的典型的電壓來源變換器驅(qū)動。</p><p>　　同樣整流器在不同斷電源(UPS)可以也被找到。</p><p>　　圖3. 用于開關(guān)方式電源的階段整流器。</p><

4、p>　　在表3是用于開關(guān)方式電源的帶電容的階段整流器。這種電源是用途廣泛在計算機，顯示器和在許多其他電子設(shè)備。</p><p>　　整流器產(chǎn)生在諧波指令和頻率下滿足條件的諧波電流：</p><p><b>　?。?）</b></p><p><b>　　這里：</b></p><p><

5、b>　　=諧波電流的頻率</b></p><p><b>　　=系統(tǒng)的基礎(chǔ)頻率</b></p><p><b>　　=諧波的指令</b></p><p><b>　　=1、2、3…</b></p><p><b>　　=整流器的脈沖數(shù)</b&g

6、t;</p><p>　　如果整流器被連接入大的總線，則諧波電流的振幅可以被計算如下：</p><p><b>　?。?）</b></p><p><b>　　這里：</b></p><p>　　=諧波電流的振幅‘n’</p><p><b>　　=整流器的基礎(chǔ)電流

7、</b></p><p><b>　　=諧波指令數(shù)</b></p><p>　　然而在真正的電網(wǎng)諧波電流比計算可能有比上面慣例(2)更高的振幅。在下個章節(jié)有另外種類一些被測量的諧波電流整流器。</p><p>　　1.1在真正電網(wǎng)中的諧波電流</p><p>　　表4是根本被測量的交流邊，并且諧波電流直流驅(qū)動

8、與它的裝載信息。能被看見第5諧波在這種情況下是28%對根本性的632A，而它的根據(jù)慣例2的理論價值是20%。</p><p>　　圖4 是帶高負荷的直流驅(qū)動中的基波和諧波電流</p><p>　　圖 5 是低負荷直流驅(qū)動中的基波和諧波電流</p><p>　　在表5有與表4一樣，都是直流驅(qū)動，但是現(xiàn)有更低的負載，。然而增加諧波的百分比之后基波電流從2261A被減少到

9、1255A，例如第5諧波電流現(xiàn)在是基波電流的41%相當于515A.但是值得注意的是，諧波電流的絕對值是高在高裝載情況之下。</p><p>　　圖6 是電壓源變換器的標準電流</p><p>　　在表6有8套電壓變換器被連接到380V電網(wǎng)。要展示這個類型變換器諧波增加得算術(shù)測量首先被做了一致變換器然后在主饋線。能被看見的5次諧波是8倍于變換器的數(shù)量。</p><p>

10、;　　表7是與電容使光滑的一臺階段整流器畫的典型的電流。這種諧波電流非常高。</p><p>　　圖7 是帶均勻容性的整流器的電流曲線</p><p>　　典型的調(diào)和分量是3rd~80%， 5th~60%， 7th~45%and 9th~35%。</p><p>　　值得注意的是，零序列諧波在導線積累。在導線上的這些零的序列潮流大于在每個階段的電流。</p&g

11、t;<p><b>　　諧波的作用</b></p><p><b>　　2．1變壓器</b></p><p>　　諧波電流導致銅損耗和磁通損耗的增加。諧波電壓導致鐵損耗的增加。與純粹的正弦電壓、電流相比，諧波會導致更高的溫度。值得注意的是，這些另外的損失由于諧波以電流和頻率的正方形的比例將上升，造成變壓器的減少的根本負載容量。當選擇

12、正確標定功率為了變壓器能供應(yīng)非線性裝載時應(yīng)該做一充分減稅保證變壓器的溫升在容許極限內(nèi)將依然是。而值得注意的是由于諧波引起的損失將根據(jù)消耗的千瓦小時由顧客支付。諧波在變壓器中也可能導致噪聲的增加。</p><p><b>　　2.2 輸電線路</b></p><p>　　輸電線路引起的熱量的損耗取決于維護系統(tǒng)的電流波形，這另外的熱化是由皮層效應(yīng)和鄰近效應(yīng)的二種現(xiàn)象造成的

13、，其中這兩個取決于頻率并且控制著大小和間距。這兩個作用導致交流阻抗的增加，反過來導致的增加。</p><p>　　2．3 電動機和發(fā)電機</p><p>　　諧波電流和電壓的主效應(yīng)是同步機械在轉(zhuǎn)動過程中以熱能的形式造成鐵和銅損耗的增加。這些額外的損失導致機器效率的降低，并且可能影響電機扭矩。 在電動機負載對這樣變異處，是敏感的搏動的扭矩產(chǎn)品可能影響產(chǎn)品質(zhì)量。從敏感裝載的例子一些合成纖維轉(zhuǎn)動

14、和一些金屬運作的應(yīng)用可以被提及。與正弦磁化比較，并且在旋轉(zhuǎn)機械的情況下，諧波可能增加可聽見的噪聲產(chǎn)生。第5和第7的諧波對可能創(chuàng)造機械動擺以第6個諧波頻率在發(fā)電器或在馬達裝載系統(tǒng)。機械動擺是由擺動的扭矩的造成的由于諧波電流和基頻磁場。如果機械共鳴頻率與電子刺激頻率相符，強機械力量可以被發(fā)展，并且有機械損傷的風險。</p><p><b>　　2.4電子設(shè)備</b></p><

15、;p>　　電力電子設(shè)備對電源電壓的諧波畸變是敏感的。這種設(shè)備經(jīng)常同步它的操作對電壓零相交或?qū)﹄妷翰ㄐ蔚钠渌矫妗ｋ妷旱闹C波畸變可能導致電壓轉(zhuǎn)移零相交或改變逐步采用電壓的一個階段高于其他階段成為逐步采用電壓的點。他們都是不同種類的電力電子控制線路的重點。這些點的誤解由控制系統(tǒng)的可能導致控制系統(tǒng)的故障。電信設(shè)備的干擾也可能歸結(jié)于在電力和電信線路之間的引人或電容耦合。計算機和可編程序控制器的電子設(shè)備通常要求總諧波(THD)供應(yīng)比5%一單

16、獨調(diào)和分量較少比3%根本電壓是較少。更高的失真值也許導致控制設(shè)備的故障，可能反過來導致生產(chǎn)和過程中斷，也有可能造成嚴重的經(jīng)濟損失。</p><p>　　2．5功率因數(shù)補償電容器</p><p>　　電容器與其它設(shè)備相較有很大區(qū)別，電容器組的容抗隨頻率升高而降低，因此，電容器組起到吸收高次諧波電流的作用，這將導致電容器組溫度提高并增加絕緣材料的介質(zhì)應(yīng)力。頻繁地切換非線性電磁組件如變壓器會產(chǎn)生

17、諧波電流，這些諧波電流將增加電容器的負擔。應(yīng)當注意的是熔絲通常不是用來當作電容器之過載保護。由諧波引起的發(fā)熱和電壓增加意味著電容器使用壽命的縮短。在電力系統(tǒng)中使用電容器組時，因其容性特點在系統(tǒng)共振情況下可顯著的改變系統(tǒng)阻抗。必需考慮系統(tǒng)產(chǎn)生諧振的可能性。系統(tǒng)諧振將導致諧波電壓和電流會明顯地高于在無諧振情況下出現(xiàn)的諧波電壓和電流。</p><p><b>　　3．總結(jié)</b></p>

18、;<p>　　由大部份案例中可發(fā)現(xiàn)，在公共電網(wǎng)中之諧波畸變水平達到所規(guī)定臨界值以前，諧波問題便已明顯地出現(xiàn)在工業(yè)工廠或商業(yè)用戶中。在用戶系統(tǒng)中，若使用不串接電抗器之電容器組并造成諧振情況，則于裝有電容器組之母線上將導致高電壓畸變。用戶設(shè)備中一些諸如電動機過熱，變壓器過熱及電子設(shè)備誤動作的事情都會發(fā)生。因此對電力用戶而言，迫切需要的是了解可能發(fā)生之諧波問題，并妥善處理使諧波畸變限制在合理范圍內(nèi)。</p><

19、;p>　　計算機仿真計算可針對各種不同電網(wǎng)情況進行快速分析，其輸出結(jié)果可當作設(shè)計之依據(jù)。無論如何，現(xiàn)場之測量不但可以提供可貴之諧波信息，并可當作計算機仿真之輸入值，或者可用來驗證計算結(jié)果之準確性。</p><p>　　譯自《Martti Tuomainen NOKIAN CAPACITRS EN-TH04-11/2004》</p><p>　　A1.2 Harmonics and R

20、eactive Power Compensation in Practice</p><p><b>　　General</b></p><p>　　Harmonics in utility and industrial networks have an increasing trend all over the world.This is clearly relat

21、ed to the increasing use of non-linear loads and devices in industry and in commercial buildings.These non-linear devices are often thyristor or diode rectifiers,which thus contribute to the deterioration of the power qu

22、ality in the networks,can be found for example in the following applications:</p><p>　　-in variable speed drives(VSD)</p><p>　　-for manufacturing and process industry</p><p>　　-for

23、inductive heating in metal industry</p><p>　　-for lifts and air-condition pumps and fans in commercial</p><p><b>　　buildings</b></p><p>　　-in uninteruptable power suppli

24、es(UPS)for computers and other</p><p>　　essential loads in commercial and industrial buildings</p><p>　　-in computers and in other office equipment</p><p>　　In figure 1 there is a t

25、ypical DC-drive with 6-pulse thyristor rectifier and in figure 2 a typical voltage source inverter drive with 6-pulse diode rectifier.</p><p>　　Same rectifiers can be found also in uninterruptible power supp

26、lies(UPS).</p><p>　　Figure 3.One phase rectifier used for Switch Mode Power Supplies.</p><p>　　In figure 3 there is one phase rectifier with capacitive smoothing used for Switch Mode Power Suppl

27、ies.This kind of power supplies are widely used in computers,monitors and in many other electronic equipment.</p><p>　　Rectifiers produce harmonic currents having following harmonic orders or</p><

28、p>　　Frequencies:</p><p><b>　　(1)</b></p><p><b>　　where:</b></p><p>　　=frequency of the harmonic current</p><p>　　=fundamental frequency of th

29、e system</p><p>　　=order of the harmonic</p><p><b>　　=1,2,3,….</b></p><p>　　=pulse number of the rectifier</p><p>　　If the rectifier is connected into an un

30、limited bus the amplitudes of the</p><p>　　harmonic currents can be calculated as follows:</p><p><b>　　(2)</b></p><p><b>　　where:</b></p><p>　　=

31、amplitude of the harmonic current order“n”</p><p>　　=fundamental current of the rectifier</p><p>　　=order of the harmonic</p><p>　　However in real networks harmonic currents can hav

32、e significantly higher amplitudes than calculated with formula(2)above.In next chapter there are some measured harmonic currents of different kind of rectifiers.</p><p>　　1.1 Harmonic currents in real networ

33、ks</p><p>　　In figure 4 the are measured AC-side fundamental and harmonic currents of a DC-drive with its load information.As can be seen the 5th harmonic is in this case 28%corresponding to 632A of the fund

34、amental whereas its theoretical value according to formula 2 is 20%.</p><p>　　Figure 4.Fundamental and harmonic currents of a DC-drive with high load.</p><p>　　Figure 5.Fundamental and harmonic

35、currents of a DC-drive with low load.</p><p>　　In figure 5 there is the same DC-drive than in figure 4 but now with lower load.Fundamental current is decreased from 2261A to 1255A.However the percentages of

36、the harmonics are clearly increased.For example the 5th harmonic current is now 41%of the fundamental current corresponding to 515A.However it should be noted that absolute values of the harmonic currents are higher unde

37、r high load situation</p><p>　　Figure 6.Measured currents of voltage source inverters.</p><p>　　In figure 6 there are 8 sets of voltage source inverters connected to 380V network. To demonstrate

38、 that harmonics of this type inverters add arithmetically measurement was first made at one of the inverters and then at the main feeder. As can be seen 5th harmonic at the main is 8 times higher corresponding to the num

39、ber of the inverters.</p><p>　　In figure 7 there is the typical current drawn by one phase rectifier with capacitive smoothing. Harmonic content of this kind of current is very high.</p><p>　　Fi

40、gure 7.Current drawn by one phase rectifier with capacitive smoothing</p><p>　　Typical harmonic components are 3rd~80%,5th~60%,7th~45%and 9th~35%.</p><p>　　It should be noted that zero sequence

41、harmonics accumulates in theneural wire.These zero sequence currents in neutral wire may reachvalues bigger than currents in each phase.</p><p>　　2.Effects of Harmonics</p><p>　　2.1 Transformers

42、</p><p>　　Harmonic currents cause an increase in copper losses and stray flux losses. Harmonic voltages cause an increase in iron losses. The overall effect is a higher temperature rise, as compared to purel

43、y fundamental sinusoidal current and voltage operation. It shall be noted that these additional losses due to harmonics will rise in proportion to the square of the current and frequency, resulting in decreased fundament

44、al loading capacity of the transformer. When selecting correct rated power for the </p><p>　　2.2 Power Cables</p><p>　　Non-sinusodial currents in conductors will cause more heating than that wha

45、t would be expected for the RMS value of the waveform. This additional heating is caused by two phenomena known as skin effect and proximity effect, both of which depend on frequency as well as conductor size and spacing

46、. These two effects result as an increased ac resistance, which in turn leads to increased x RAC losses.</p><p>　　2.3 Motors and Generators</p><p>　　The main effect of the harmonic currents and

47、voltages in rotating induction and synchronous machinery is increased heating caused by the iron and copper losses at harmonic frequencies. These additional losses lead to decreased machine efficiency and can also affect

48、 the torque developed. Pulsating torque output can affect product quality in cases where motor loads are sensitive to such variations. As examples from sensitive loads some synthetic fibre spinning and some metal working

49、 applications c</p><p>　　2.4 Electronic Equipment</p><p>　　Power electronic equipment is sensitive to harmonic distortion of the supply voltage. This equipment is often synchronising its operati

50、on to the voltage zero crossings or to other aspects of the voltage wave shape. Harmonic distortion of the voltage can lead to the shifting of the voltage</p><p>　　zero crossing or change the point where one

51、 phase to phase voltage becomes higher than an other phase to phase voltage. Both of these are important points for different kind of power electronic circuit controls. Misinterpretation of these points by the control sy

52、stems can lead to the malfunction of the control system. Disturbances of the telecommunication equipment are also possible due to the inductive or capacitive coupling between power and telecommunication lines.</p>

53、<p>　　Computers and some other kind of electronic equipment like programmable controllers require usually that the total harmonic voltagedistortion(THD)of the supply is less than 5%and one individual harmonic compo

54、nent is less than 3%of the fundamental voltage. Higher distortion values may result in misoperation of the control equipment, which in turn can lead to production and process interruptions, which can have high economical

55、 consequences.</p><p>　　2.5 Switchgear and Relaying</p><p>　　Like in other type of equipment too harmonic currents cause also in switchgear additional losses leading to increased heating and red

56、uced fundamental current carrying capability.An increased temperature of some insulating components results in shortening of their lifetime.</p><p>　　Older solid-state tripping devices on low voltage circuit

57、 breakers have responded to the peak currents.This type of tripping devices may cause nuisance tripping in feeders supplying non-linear loads.New tripping devices respond to the RMS values of the current. The response of

58、 the protective relays to the distortion depends a lot on the measuring principle used and there is no any common rules which could be used to describe what is the impact of harmonics on large variety of the relays.Howev

59、er </p><p>　　2.6 Power Factor Correction Capacitors</p><p>　　Capacitors differ from other type of equipment due to its capacitive nature, which can dramatically change the system impedance under

60、 system resonant condition. The reactance of a capacitor bank decreases with the higher frequencies,and therefore,bank acts as a sink for higher harmonic currents.This effect increases the heating and dielectric stress o

61、f the insulation material.Frequent switching of non-linear magnetic components like transformers can produce harmonic currents,which will add to th</p><p>　　The major concern arising from the use of capacito

62、rs in power systems is the possibility of the system resonance.This effect leads to harmonic voltages and currents that are considerably higher than they would be in the case without resonance.</p><p>　　2.6.

63、1 Harmonics and Parallel Resonance</p><p>　　Harmonic currents produced for example by variable speed drives can be amplified up to 10-15 times in parallel resonance circuit formed by the capacitance of the c

64、apacitor bank and the network inductance.</p><p>　　Amplified harmonic currents through the capacitors can lead to internal over heating of the capacitor unit.Please note that currents having higher frequency

65、 than fundamental frequency cause more losses than 50Hz current having same amplitude.An example of parallel resonance circuit with its equivalent circuit is shown in figure 8.</p><p>　　Figure 8.Parallel res

66、onance circuit and its equivalent circuit.</p><p>　　2.6.2 Harmonics and Series Resonance</p><p>　　In case the voltage of the upstream network is distorted the series resonance circuit,formed by

67、capacitance of the capacitor bank and the short circuit inductance of the supplying transformer,can draw high harmonic currents through the capacitors.Series resonance can lead to high voltage distortion levels at low vo

68、ltage side of the transformer.For an example of series resonance circuit please refer to figure 9.</p><p>　　Figure 9.Series resonance circuit and its equivalent circuit.</p><p>　　2.6.3 Recommend

69、ations.</p><p>　　Whenever there is unlinear load(dc-drives,inverters,UPS,all kind of rectifier,etc.)connected to the bus at which capacitor bank is intended to be used care should be taken when designing rea

70、ctive power compensation system.</p><p>　　To avoid parallel or series resonance at low voltage level filter or blocking type capacitor banks should be used.</p><p>　　In cases where there are har

71、monic limits imposed by the utility or generating authorities quite often filter capacitor bank turns out to be necessary to meet requirements like stated for example in IEEE standard 519-1992 or in Engineering Recommend

72、ation G5/3.For typical filter capacitor bank arrangements where there are 3 tuned branches for 5th 7th and 11th harmonic please refer to figure 10.The number of tuned branches depends on the harmonics to be absorbed and

73、on required reactive power to be</p><p>　　To be able to design filter capacitor bank harmonic producing load should be identified and at existing plants harmonic measurement is desirable.</p><p>

74、;　　Figure 10.Reactive power compensation with filter capacitor banks.</p><p>　　According to IEEE 519-1992 individual voltage distortion is allowed to be 3%of the fundamental.If for example at some bus non-li

75、near load has caused an individual voltage distortion which has been measured to be less than 3%without capacitors,it may lead to assumption that any kind of electrical equipment could be connected at the same bus withou

76、t any concern.Please note however,that whenever capacitor bank without any reactors is connected at such bus,there will be a certain parallel and series</p><p>　　In cases where there are no harmonic limits b

77、locking type capacitors can be used.However it should be kept in mind that major part of the harmonics is then injected into the upstream network.For typical blocking type capacitor bank please refer to fig 11.The requir

78、ed number of steps depends on load power factor and target power factor.For the design of blocking capacitor bank voltage distortion limits are usually given.Typical values for low voltage could be for example:U3rd=0,5%U

79、5th=5%and U7th=</p><p>　　Typical detuning frequencies are 204hz corresponding to 6%reactor and 189hz corresponding to 7%reactor respectively.The use of 7%reactors allows normally more non-linear load to be c

80、onnected than the use of 6% reactors.The linearity of the iron core of the reactor should be designed so that saturation is not possible with inrush current and at rated voltage distortion.</p><p>　　Figure 1

81、1.Reactive power compensation with blocking capacitor banks.</p><p>　　When designing reactive power compensation system,for example for a new commercial building,the use the capacitor units having higher rat

82、ed voltage than system voltage(for example 525V units in 400V system)is quite often justified if it is not known what kind of load will come with the tenants.The use of higher rated units enables reactors to be added lat

83、er on if it turns out that load will produce harmonics. Whenever there is a doubt that ambient temperature of the capacitor units may exceed up</p><p>　　3.Conclusions</p><p>　　In most cases harm

84、onic problems show up at the industrial plants or at the commercial customers before distortion level on the utility network reach critical values. Resonance conditions created by the use of the capacitors without reacto

85、rs at the customer’s facilities will lead to high distortion on the low voltage bus where the capacitors are connected on. Problems like motor overheating, transformer heating and malfunction of the electronic equipment

86、within the customer’s facilities are likel</p><p>　　With previous documented cases it has become clear that whenever designing reactive power compensation systems harmonics should be kept in mind. Also it ha

87、s been shown that there are solutions for the problems arising from harmonics. With proper design resonance situations can be avoided and possible emission limits imposed by the utility can be met. </p><p>　

88、　Computer calculations allow a quick look at different network conditions and their output can be used as design data. However measurements at sites provide valuable information and their results can be used as input val