【正文】 e proficient in its use to continue with this text. It is a useful mathematical tool, however,and should be learned. Finding the area under the positive pulse of a sine wave using integration, we havewhere ∫?is the sign of integration, 0 and p are the limits of integration, Am sin a is the function to be integrated, and da indicates that we are integrating with respect to a. Integrating, we obtainSince we know the area under the positive (or negative) pulse, we can easily determine the average value of the positive (or negative) region of a sine wave pulse by applying Eq. ():
For the waveform of Fig. ,
EXAMPLE Determine the average value of the sinusoidal waveform of Fig. .Solution: By inspection it is fairly obvious thatthe average value of a pure sinusoidal waveform over one full cycle iszero.EXAMPLE Determine the average value of the waveform of Fig. .Solution: The peaktopeak value of the sinusoidal function is16 mV +2 mV
= 18 mV. The peak amplitude of the sinusoidal waveform is, therefore, 18 mV/2
= 9 mV. Counting down 9 mV from 2 mV(or 9 mV up from 16 mV) results in an average or dc level of 7 mV,as noted by the dashed line of Fig. .EXAMPLE Determine the average value of the waveform of Fig. .Solution:EXAMPLE For the waveform of Fig. , determine whether the average value is positive or negative, and determine its approximate value.Solution: From the appearance of the waveform, the average value is positive and in the vicinity of 2 mV. Occasionally, judgments of this type will have to be made.InstrumentationThe dc level or average value of any waveform can be found using a digital multimeter (DMM) or an oscilloscope. For purely dc circuits,simply set the DMM on dc, and read the voltage or current are limited to voltage levels using the sequence of steps listed below:1. First choose GND from the DCGNDAC option list associated with each vertical channel. The GND option blocks any signal to which the oscilloscope probe may be connected from entering the oscilloscope and responds with just a horizontal line. Set the resulting line in the middle of the vertical axis on the horizontal axis, as shown in Fig. (a).2. Apply the oscilloscope probe to the voltage to be measured (if not already connected), and switch to the DC option. If a dc voltage is present, the horizontal line will shift up or down, as demonstrated in Fig. (b). Multiplying the shift by the vertical sensitivity will result in the dc voltage. An upward shift is a positive voltage (higher potential at the red or positive lead of the oscilloscope), while a downward shift is a negative voltage (lower potential at the red or positive lead of the oscilloscope). In general,1. Using the GND option, reset the horizontal line to the middle of the screen.2. Switch to AC (all dc ponents of the signal to which the probe is connected will be blocked from entering the oscilloscope— only the alternating, or changing, ponents will be displayed).Note the location of some definitive point on the waveform, such as the bottom of the halfwave rectified waveform of Fig. (a)。 附錄 A the equivalent dc value. In the analysis of electronic circuits to be considered in a later course, both dc and ac sources of voltage will be applied to the same work. It will then be necessary to know or determine the dc (or average value) and ac ponents of the voltage or current in various parts of the system.EXAMPLE Determine the average value of the waveforms of Fig. .FIG. Example .Solutions:a. By inspection, the area above the axis equals the area below over one cycle, resulting in an average value of zero volts.b. Using Eq.():as shown in Fig. .In reality, the waveform of Fig. (b) is simply the square wave of Fig. (a) with a dc shift of 4 V。除了上網(wǎng)或是圖書館查找了一些相關(guān)方面的資料以外，在完成整個論文的過程中，董老師對于我們的畢業(yè)設(shè)計細(xì)心的指導(dǎo)和不懈的支持，幾乎是有求必應(yīng)，在此表達衷心的感謝。希望這次的經(jīng)歷能讓我在以后學(xué)習(xí)中激勵我繼續(xù)進步。 參考文獻[1] 陳伯時主編《電力拖動自動控制系統(tǒng)》第 2 版﹒北京：機械工業(yè)出版社，1992[2] 彭鴻才主編《電機原理與拖動》北京：機械工業(yè)出版社，1998[3] 王兆安、黃俊主編《電力電子技術(shù)》第 4 版 ﹒北京：機械工業(yè)出版社，1996[4] 王離九主編《電力拖動自動控制系統(tǒng)》武漢：華中理工大學(xué)出版社，1991[5] 吳麒《自動控制原理》北京：機械工業(yè)出版社，1990[6] 謝宗安主編《自動控制系統(tǒng)》重慶：重慶大學(xué)出版社，1996[7] 馮垛生，鄧則名主編《電力拖動自動控制系統(tǒng)》廣州：廣東高等教育出版社，1998[8] Leonhard,W《Control of Electrical Drives 3rd ed》SpringerVerlag,2022[9] 陳伯時等《雙閉環(huán)調(diào)速系統(tǒng)的工程設(shè)計（講座） 》冶金自動化，1983（1） 、 （2）[10] 賴福新《電機控制系統(tǒng)》上海：上海交通大學(xué)出版社，1995[11] 秦祖蔭編《電力電子技術(shù)基礎(chǔ)》西安：西安交通大學(xué)電器教研室，1990[12] Murphy J M D and Turnbull F G《Power Electronic Control of AC Motors》Pergamon Press,1988[13] 林渭勛主編﹒電力電子技術(shù)基礎(chǔ)[M]﹒北京：機械工業(yè)出版社，1990[15] 《電力電子變流技術(shù)》 黃俊 機械工業(yè)出版社 2022 致 謝經(jīng)過三個多月的學(xué)習(xí)和實踐，我們在董老師的悉心幫助下，比較順利的完成了本次設(shè)計,并把平時所學(xué)習(xí)到的東西用在了我們的設(shè)計中，使我的受益匪淺。再次深深體會到書本上的知識是遠(yuǎn)遠(yuǎn)不夠的，要更加深入得了解控制領(lǐng)域需要不斷的學(xué)習(xí)和實踐，才能夠保持與時俱進。通過這次學(xué)習(xí)，本人進一步熟悉了電力拖動自動控制系統(tǒng)及電力電子技術(shù)的基本理論，加深了對一些比較抽象的理論知識的理解，對直流調(diào)速系統(tǒng)的基本結(jié)構(gòu)、各控制單元的工作原理、系統(tǒng)的性能特點都有了更深入的理解。為使系統(tǒng)的穩(wěn)態(tài)性能更好，該系統(tǒng)采用無靜差調(diào)節(jié)，即轉(zhuǎn)速調(diào)節(jié)器采用比例積分調(diào)節(jié)器（PI 調(diào)節(jié)器） ，使系統(tǒng)保證恒速運行，以保證滿足更嚴(yán)格的生產(chǎn)要求。實驗結(jié)果表明經(jīng)過該設(shè)計系統(tǒng)改進，與其為單閉環(huán)系統(tǒng)相比：機械特性偏硬，快速起制動，突加負(fù)載動態(tài)速將小。因此 式（711 ）??? 式（712）??? 校驗近似條件，電流環(huán)截止頻率 ?（1） 晶閘管裝置傳遞函數(shù)近似條件 13cisWT?現(xiàn)在 滿足近似條件???（2） 忽略反電動勢對電流環(huán)影響的條件 13mlciT?現(xiàn)在 滿足近似條件 ciT Wss?????（3） 小時間常數(shù)近似處理條件：13cisoiWT?現(xiàn)在 滿足近似條1 WsT?????件 電流調(diào)節(jié)器原理圖如下所示，按所有運算放大器取 各電阻和電容值計算如下：04Rk???0取30..56iiCFFR????.取0??0.按照上述參數(shù)，電流環(huán)可以達到 動態(tài)指標(biāo)為 滿足設(shè)計要求。%176。%176。i 39。2n 電流環(huán) 39。nRK?04Rk?????? 若取 ， 39。fidnKI?? 則 39。MIdTG~TAUn*R0C+ASiiLV+ct 圖 72 雙閉環(huán)控制系統(tǒng)結(jié)構(gòu)圖 為了獲得良好的靜動態(tài)性能，雙閉環(huán)調(diào)速系統(tǒng)的兩個調(diào)節(jié)器一般都采用 PI 調(diào)節(jié)器，其原理圖示于圖 72。這就是說把轉(zhuǎn)速調(diào)節(jié)器的輸出作為電流調(diào)節(jié)器的輸入，再用電流調(diào)節(jié)器的輸出去控制晶閘管整流器的觸發(fā)裝置。通常首先給定最小電流 以 A 為單位；再利用它計算所需的總電感量，以 mH 為單位，減mindI去電樞電感，即得平波電抗應(yīng)有的電感值。（2）設(shè)置平波電抗器。為了避免或減輕這種影響，須采用抑制電流脈動的措施。第 6 章 計算主電路的平波電抗器量 主電路電抗器總電感量的計算整流電路的脈動數(shù) m= ，其數(shù)目總是有限的，比直流電機每對極下?lián)Q向片的數(shù)目要少的多，因此，除非主電路電感 L=∞ 否則，VM 系統(tǒng)的電流脈