本文關(guān)鍵詞： 電容電流 信號注入法 等值模型 頻率范圍 容量大小 數(shù)字相敏檢波　出處：《西安科技大學》2017年碩士論文　論文類型：學位論文

【摘要】：隨著大規(guī)模的配電網(wǎng)改造及大量電纜線路投入運行,中壓配電網(wǎng)電容電流越來越大。為減少電容電流的危害和提高配電網(wǎng)的運行可靠性,普遍采取在中壓配電網(wǎng)中性點安裝消弧線圈的措施。要合理配置消弧線圈的容量,就必須準確測量中壓配電網(wǎng)的電容電流。目前測量電容電流的方法較多,但是隨著電纜線路比例的增大,中壓配電網(wǎng)對稱度升高,依賴于不對稱度的傳統(tǒng)一次側(cè)測量電容電流方法的測量精度降低甚至無法測量。此外,這些傳統(tǒng)測量方法存在操作繁瑣且不安全的弊端。為此,可采用在二次側(cè)操作、且無需依靠不對稱度保證測量精度的信號注入法測量中壓配電網(wǎng)的電容電流。但是,在現(xiàn)場應(yīng)用中,該方法的測量誤差較大,產(chǎn)生誤差的原因是信號注入法測量電容電流的一些關(guān)鍵技術(shù)仍存在不足,如中壓配電網(wǎng)零序回路的等值模型不夠精確、注入信號的頻率范圍和容量不合適,返回電壓信號的檢測算法不準確等。為了能夠更精確的測量中壓配電網(wǎng)的電容電流,文中在信號注入法測量電容電流原理的基礎(chǔ)上,對信號注入法的幾個關(guān)鍵技術(shù)進行深入研究。首先,對信號注入法中的三頻法、分頻法、掃頻法的測量原理和誤差進行深入分析和仿真驗證,并對每種方法的特點及適用范圍做出綜合評價。其次,以三芯電纜零序參數(shù)頻率特性為基礎(chǔ)分析中壓配電網(wǎng)零序阻抗頻率特性,利用一端口串聯(lián)等值網(wǎng)絡(luò)的方法改進中壓配電網(wǎng)零序回路等值模型,結(jié)合PT模型得到精確的信號注入法測量模型。將傳統(tǒng)的測量模型與精確測量模型進行了比較分析,證明了傳統(tǒng)測量模型的準確性,也說明信號注入法的測量原理并不存在方法誤差。再次,對PT勵磁特性和PT傳變特性進行試驗研究并分析試驗數(shù)據(jù),確定了注入電流信號的頻率范圍�？紤]注入信號衰減和PT容量限制的因素確定了注入信號的容量大小。最后,用數(shù)字相敏檢波技術(shù)(DPSD)來檢測淹沒在中壓配電網(wǎng)中的低信噪比返回電壓信號。設(shè)計檢測算法并通過仿真驗證,發(fā)現(xiàn)DPSD算法有效地抑制了中壓配電網(wǎng)中諧波信號和強噪聲,并準確地將返回電壓信號提取出來。因此,信號注入法測量電容電流的關(guān)鍵技術(shù)研究成果對現(xiàn)場測量和測量儀器的研發(fā)均有指導性意義。
[Abstract]:With the large-scale transformation of the distribution network and a large number of cable lines put into operation, the capacitive current of the medium voltage distribution network is increasing. In order to reduce the harm of the capacitance current and improve the reliability of the distribution network. The measures of installing arc-suppression coil in neutral point of medium voltage distribution network are generally adopted. In order to reasonably configure the capacity of arc-suppression coil, it is necessary to accurately measure the capacitance current of medium voltage distribution network. At present, there are many methods to measure capacitance current. However, with the increase of the proportion of cable lines, the symmetry of medium voltage distribution network increases, and the accuracy of the traditional primary side capacitance current measurement method, which depends on the asymmetry, decreases or even cannot be measured. These traditional measurement methods have the disadvantages of cumbersome and unsafe operation. Therefore, the secondary side operation can be adopted. And the signal injection method which does not depend on asymmetry degree to ensure the measurement accuracy is used to measure the capacitance current of the medium voltage distribution network. However, in the field application, the measurement error of this method is large. The reason of the error is that some key techniques of measuring capacitance current by signal injection method are still insufficient, such as the equivalent model of zero sequence loop in medium voltage distribution network is not accurate enough, the frequency range and capacity of injection signal are not suitable. In order to measure capacitance current of medium voltage distribution network more accurately, the principle of capacitance current is measured by signal injection method. Several key technologies of the signal injection method are studied. Firstly, the measurement principle and error of the three frequency method, the frequency division method and the sweep method are analyzed and simulated. And make a comprehensive evaluation of the characteristics and applicable range of each method. Secondly, based on the frequency characteristics of zero-sequence parameters of three-core cable, the zero-sequence impedance frequency characteristics of medium-voltage distribution network are analyzed. The method of one-port series equivalent network is used to improve the zero-sequence circuit equivalent model of medium voltage distribution network. The accurate signal injection measurement model is obtained by combining the PT model. The accuracy of the traditional measurement model is proved by comparing the traditional measurement model with the accurate measurement model. It also shows that there is no error in the measurement principle of the signal injection method. Thirdly, the excitation characteristics of PT and the transmission characteristics of PT are studied and the test data are analyzed. The frequency range of the injection current signal is determined. The capacity of the injection signal is determined by considering the attenuation of the injection signal and the limit of the PT capacity. Digital phase sensitive detector (DPSD) is used to detect the low signal-to-noise ratio (SNR) return voltage signals submerged in the medium voltage distribution network. The detection algorithm is designed and verified by simulation. It is found that the DPSD algorithm can effectively suppress the harmonic signal and strong noise in the medium voltage distribution network and extract the return voltage signal accurately. The research results of the key technology of measuring capacitive current by signal injection are instructive to the research and development of field measurement and measuring instruments.
【學位授予單位】：西安科技大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM933.1

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