2023年全國碩士研究生考試考研英語一試題真題(含答案詳解+作文范文)_第1頁
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1、<p><b>  附 錄</b></p><p><b>  附錄A 外文資料</b></p><p>  Data Collection</p><p>  At present,the management of China’s colleges and universities’ apartments a

2、re developing toward standardization and market development,accidents have occurred in electricity,while some colleges and universities have installed apartment energy metering control system,however,these systems monito

3、r the prevalence of low level,billing accuracy is low,electricity-sharing,the network number of the drawbacks of low extent.Therefore,improving the Energy Measurement monitoring device has become more urg</p><

4、p>  Data acquisition, also known as data acquisition, is the use of a device that collect data from outside the system and enter into an interface within the system.Data acquisition technology is widely cited in the v

5、arious fields.Such as camera, microphone, all data collection tools.Data is being collected has been converted to electrical signals of various physical quantities such as temperature, water level, wind speed, pressure,

6、etc., can be analog, it can be digital.Sample collection generally </p><p>  Digital signal processor (DSP) to the high-speed data processing ability and strong peripherals interface, more and more widely us

7、ed in power quality analysis field, in order to improve the real-time and reliability.The DSP and microcomputer as the center of the system, realize the power system signal collection and analysis. This paper based on th

8、e FFT algorithm with window interpolation electric system harmonic analysis, improves the accuracy of the power quality parameters. In electricity par</p><p>  The system consists of two main components, mai

9、nly complete data acquisition and logic control.To synchronous sampling and A/D converter circuit priority . The DSP development board(SY-5402EVM),complete data processing. THE signal after transformer, op-amp into A/D

10、converter, using DSP multi-channel buffer (McBSP) and serial port (A/D connected, data collection and operations. At the same time, adopt PLL circuit implementation synchronous sampling, can prevent well due to sampling

11、synchronizati</p><p>  The realization method of ac sample:In the field of power quality analysis,The fast Fourier transform (FFT) algorithm analysis of electric system harmonic is commonly used.and the FFT

12、algorithm to signal a strict requirements synchronous sampling. The synchronous sampling influence: it's difficult to accomplish synchronous sampling and integer a period truncation in the actual measurement, so ther

13、e was a affect the measurement accuracy of the frequency spectrum leakage problem. The signal has to</p><p>  On the fundamental reactive current and harmonic current detection, there are mainly 2 ways: Firs

14、t, the instantaneous reactive power theory based method, the second is based on adaptive cancellation techniques.In addition, there are other non-mainstream approach, such as fast Fourier transform method, wavelet transf

15、orm.</p><p>  Instantaneous power theory based on the method of offensive principles are: a three-phase current detection and load phase voltage A, the coordinate transformation, two-phase stationary coordin

16、ate system the current value, calculate the instantaneous active and instantaneous reactive power ip iq,then after coordinate transformation, three-phase fundamental active current, with the final load current minus the

17、fundamental current, active power and harmonic currents are fundamental iah, ibhi, ich.</p><p>  From:Principles of Data Acquisitio </p><p><b>  數(shù)據(jù)采集</b></p><p>  目前,我國

18、高校公寓管理正在向著正規(guī)化、市場化發(fā)展,在不斷提高學(xué)生方便用電的同時(shí),用電事故頻有發(fā)生,雖然部分高校公寓已經(jīng)安裝了電能計(jì)量監(jiān)控系統(tǒng),但這些系統(tǒng)普遍存在著監(jiān)控程度低、計(jì)費(fèi)精度不高、電費(fèi)均分、網(wǎng)絡(luò)程度低等諸多端。因此,對(duì)于電能計(jì)量監(jiān)控裝置的改進(jìn)變得更加緊急。本課題以高校學(xué)生公寓宿舍電能計(jì)量監(jiān)控系統(tǒng)為研究對(duì)象,設(shè)計(jì)了對(duì)學(xué)生公寓的電能數(shù)據(jù)采集器。</p><p>  數(shù)據(jù)采集,又稱數(shù)據(jù)獲取,是利用一種裝置,從系統(tǒng)外部采集

19、數(shù)據(jù)并輸入到系統(tǒng)內(nèi)部的一個(gè)接口。數(shù)據(jù)采 集技術(shù)廣泛引用在各個(gè)領(lǐng)域。比如攝像頭,麥克風(fēng),都是數(shù)據(jù)采集工具。</p><p>  被采集數(shù)據(jù)是已被轉(zhuǎn)換為電訊號(hào)的各種物理量,如溫度、水位、風(fēng)速、壓力等,可以是模擬量,也可以是數(shù)字量。采集一般是采樣方式,即隔一定時(shí)間(稱采樣周期)對(duì)同一點(diǎn)數(shù)據(jù)重復(fù)采集。采集的數(shù)據(jù)大多是瞬時(shí)值,也可是某段時(shí)間內(nèi)的一個(gè)特征值。準(zhǔn)確的數(shù)據(jù)量測是數(shù)據(jù)采集的基礎(chǔ)。數(shù)據(jù)量測方法有接觸式和非接觸式,檢測

20、元件多種多樣。不論哪種方法和元件,均以不影響被測對(duì)象狀態(tài)和測量環(huán)境為前提,以保證數(shù)據(jù)的正確性。數(shù)據(jù)采集含義很廣,包抱對(duì)面狀連續(xù)物理量的采集。在計(jì)算機(jī)輔助制圖、測圖、設(shè)計(jì)中,對(duì)圖形或圖像數(shù)字化過程也可稱為數(shù)據(jù)采集,此時(shí)被采集的是幾何量(或包括物理量,如灰度)數(shù)據(jù)。在互聯(lián)網(wǎng)行業(yè)快速發(fā)展的今天,數(shù)據(jù)采集已經(jīng)被廣泛應(yīng)用于互聯(lián)網(wǎng)及分布式領(lǐng)域,數(shù)據(jù)采集領(lǐng)域已經(jīng)發(fā)生了重要的變化。首先,分布式控制應(yīng)用場合中的智能數(shù)據(jù)采集系統(tǒng)在國內(nèi)外已經(jīng)取得了長足的發(fā)展

21、。其次,總線兼容型數(shù)據(jù)采集插件的數(shù)量不斷增大,與個(gè)人計(jì)算機(jī)兼容的數(shù)據(jù)采集系統(tǒng)的數(shù)量也在增加。國內(nèi)外各種數(shù)據(jù)采集機(jī)先后問世,將數(shù)據(jù)采集帶入了一個(gè)全新的時(shí)代。</p><p>  數(shù)字信號(hào)處理器(DSP)以其高速的數(shù)據(jù)處理能力和強(qiáng)大的外設(shè)接口,越來越廣泛地被使用于電能質(zhì)量分析領(lǐng)域,以提高系統(tǒng)的實(shí)時(shí)性和可靠性。本系統(tǒng)以DSP和單片機(jī)為心,實(shí)現(xiàn)了對(duì)系統(tǒng)中信號(hào)的采集和分析。本文采用基于加窗插值的FFT算法分析系統(tǒng)諧波,提高

22、了各項(xiàng)電能質(zhì)量參數(shù)的準(zhǔn)確性。在電能參數(shù)采集電路中,采用高精度的互感器和改進(jìn)的軟件同步交流采樣方法進(jìn)行電力參數(shù)的采集。</p><p>  系統(tǒng)硬件由兩大部分組成,主要完成數(shù)據(jù)采集和邏輯控制任務(wù),以同步采樣和A/D轉(zhuǎn)換電路為主。一塊DSP開發(fā)板(SY-5402EVM),完成數(shù)據(jù)的處理。信號(hào)經(jīng)過互感器、運(yùn)放送入A/D轉(zhuǎn)換器,利用DSP的多通道緩沖串口(McBSP)與A/D相連,進(jìn)行數(shù)據(jù)的采集和運(yùn)算。同時(shí),采用鎖相環(huán)電

23、路實(shí)現(xiàn)同步采樣,能很好地抑制由于采樣不同步而造成的測量誤差。系統(tǒng)總體框圖這里的A/D轉(zhuǎn)換器選用的是Analog Devices(AD)公司的AD73360。該芯片具有六個(gè)模擬量輸入通道,每個(gè)通道可以輸出16位的數(shù)字量。六通道同時(shí)采樣,同時(shí)轉(zhuǎn)換,分時(shí)傳輸,有效地減少了由于采樣時(shí)間不同而產(chǎn)生的相位誤差。SY-5402EVM板載的DSP芯片是TI公司的16位定點(diǎn)數(shù)字信號(hào)處理器TMS320VC5402。它具有很高的性價(jià)比并提供高速、雙向、多通道

24、帶緩沖串口,可用來與系統(tǒng)中的其它的串行器件直接接口。</p><p>  交流采樣的實(shí)現(xiàn)方法:在電能質(zhì)量分析領(lǐng)域中,常采用基于快速傅立葉變換(FFT)的算法分析系統(tǒng)諧波,而FFT算法要求對(duì)信號(hào)進(jìn)行嚴(yán)格的同步采樣。非同步采樣的影響:在實(shí)際測量時(shí)很難做到同步采樣和整數(shù)個(gè)周期截?cái)?,因此出現(xiàn)了影響測量準(zhǔn)確性的頻譜泄漏問題。在實(shí)際的測量中,所要處理的信號(hào)都是經(jīng)過采樣和A/D轉(zhuǎn)換得到的有限長數(shù)字序列,相當(dāng)于對(duì)原始信號(hào)乘以一個(gè)

25、矩形窗加以截?cái)?。時(shí)域的截?cái)鄷?huì)造成頻域的展寬,頻譜發(fā)生泄漏。在非同步采樣時(shí),由于實(shí)際信號(hào)的各次諧波分量不能正好落在頻率分辨點(diǎn)上,而是落在某兩個(gè)頻率分辨點(diǎn)之間。但是FFT的頻譜是離散的,只在各采樣點(diǎn)有頻譜,而在其它地方都沒有。這樣通過FFT并不能直接得到各次諧波分量的準(zhǔn)確值,而只能以臨近的頻率分辨點(diǎn)的值來近似代替,會(huì)造成柵欄效應(yīng)誤差。同步采樣的實(shí)現(xiàn)方法:根據(jù)提供采樣信號(hào)方式不同,同步采樣法又分為軟件同步采樣法和硬件同步采樣法兩種。軟件同步采

26、樣法是由微控制器(MCU)或DSP提供同步采樣脈沖,先測出被測信號(hào)的周期T,則采樣間隔Δt=T/N(N為一周內(nèi)的采樣點(diǎn)數(shù)),由此確定定時(shí)器的計(jì)數(shù)值,用定時(shí)中斷方式實(shí)現(xiàn)同步采樣。該方法的優(yōu)點(diǎn)是無需硬件同步電路,結(jié)構(gòu)簡單。</p><p>  關(guān)于基波無功電流和諧波電流的檢測,目前主要有2種方法:一是基于瞬時(shí)無功功率理論的方法,二是基于自適應(yīng)對(duì)消技術(shù)的方法。此外,還有其他一些非主流的方法,如,快速傅立葉變換的方法,小

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