單相特高壓自耦變壓器直流偏磁電磁特性研究
本文選題:特高壓變壓器 + 直流偏磁 ; 參考:《華北電力大學(xué)(北京)》2017年博士論文
【摘要】:高壓直流輸電和磁暴現(xiàn)象引起的變壓器直流偏磁效應(yīng)嚴(yán)重影響變壓器的安全運(yùn)行。特高壓電網(wǎng)采用八分裂導(dǎo)線,電阻小,更易遭受直流擾動(dòng)的侵害。特高壓變壓器作為特高壓電網(wǎng)的關(guān)鍵設(shè)備,其運(yùn)行的可靠性與安全性直接關(guān)乎整個(gè)電網(wǎng)的正常運(yùn)行。為此,本文針對(duì)特高壓變壓器的直流偏磁問(wèn)題進(jìn)行了計(jì)算與分析。主要研究?jī)?nèi)容和取得的成果如下:基于特高壓變壓器鐵心材料的高導(dǎo)磁性和強(qiáng)非線性特性,提出了基于空載簡(jiǎn)化電路模型下的分段解析法,進(jìn)行直流偏磁條件下計(jì)算結(jié)果準(zhǔn)確性問(wèn)題的研究與分析。繼而以解析解的計(jì)算結(jié)果為基準(zhǔn),對(duì)比分析四階龍格庫(kù)塔法的數(shù)值計(jì)算結(jié)果。結(jié)果表明,在特高壓變壓器的直流偏磁數(shù)值計(jì)算中,可通過(guò)人為增大串聯(lián)電阻和適當(dāng)減小計(jì)算時(shí)間步長(zhǎng)來(lái)獲得較為準(zhǔn)確的直流偏磁特性。該研究結(jié)果為實(shí)際特高壓變壓器進(jìn)行基于場(chǎng)路耦合法的直流偏磁計(jì)算提供了一種有效解決方法。根據(jù)特高壓變壓器實(shí)際的結(jié)構(gòu)參數(shù)和電氣連接方式,建立變壓器的場(chǎng)路耦合模型,分析串聯(lián)電阻值和時(shí)間步長(zhǎng)對(duì)直流偏磁計(jì)算結(jié)果的影響。人為增加一個(gè)串聯(lián)電阻,改變了變壓器本身的電路結(jié)構(gòu),導(dǎo)致串聯(lián)電阻后側(cè)的電壓偏離所施加的額定交流電壓。因此,提出電壓補(bǔ)償原理,進(jìn)行電壓補(bǔ)償?shù)牡?jì)算。計(jì)算結(jié)果表明,電壓補(bǔ)償可有效消除串聯(lián)電阻值導(dǎo)致的電流計(jì)算偏差。在此基礎(chǔ)上,進(jìn)行特高壓變壓器不同直流偏磁電流下的空載直流偏磁仿真計(jì)算,獲得勵(lì)磁電流和磁場(chǎng)特性。為提高特高壓變壓器空載直流偏磁計(jì)算效率,提出了一種基于動(dòng)態(tài)電感-勵(lì)磁電流曲線的空載直流偏磁快速計(jì)算方法,該方法避免了不同直流偏磁電流情況下重復(fù)進(jìn)行磁場(chǎng)模型的動(dòng)態(tài)電感的求解。通過(guò)與場(chǎng)路耦合算法計(jì)算結(jié)果的對(duì)比,驗(yàn)證了該方法的正確性和有效性。同時(shí),該方法大大節(jié)省了計(jì)算時(shí)間,提高了計(jì)算效率,為變壓器的直流偏磁計(jì)算提供了一種快速簡(jiǎn)便的計(jì)算方法。針對(duì)特高壓變壓器負(fù)載運(yùn)行方式下的直流偏磁問(wèn)題進(jìn)行研究與分析。增大原邊串聯(lián)電阻,可使原邊電流中直流分量的計(jì)算結(jié)果接近于直流偏磁電流理論值,提高計(jì)算結(jié)果的準(zhǔn)確性。分析直流偏磁情況下不同負(fù)載電阻對(duì)特高壓變壓器高、中壓繞組電流的影響,獲得了負(fù)載由過(guò)載到額定,再到輕載直至空載運(yùn)行狀態(tài)下高、中壓繞組中電流的變化規(guī)律。進(jìn)行不同直流偏磁電流時(shí)負(fù)載運(yùn)行方式下的直流偏磁計(jì)算和電流特性分析;诓煌绷髌烹娏飨掠(jì)算得到的空載與負(fù)載電流,進(jìn)行無(wú)功功率和渦流損耗計(jì)算及其特性分析,為特高壓變壓器耐受直流偏磁能力的評(píng)估提供參考。本文所開展的研究工作為進(jìn)行特高壓變壓器直流偏磁條件下的溫升計(jì)算奠定了計(jì)算基礎(chǔ)。
[Abstract]:The DC bias of transformers caused by HVDC transmission and magnetic storm seriously affects the safe operation of transformers. UHV power grid adopts eight-split conductors with low resistance and is more vulnerable to DC disturbance. As the key equipment of UHV power network, UHV transformer's reliability and safety are directly related to the normal operation of the whole power network. In this paper, the DC bias of UHV transformer is calculated and analyzed. The main research contents and achievements are as follows: based on the high conductance magnetic and nonlinear characteristics of UHV transformer core material, a piecewise analytical method based on no-load simplified circuit model is proposed. The accuracy of calculation results under DC bias is studied and analyzed. Then the numerical results of the fourth order Runge-Kutta method are compared and analyzed on the basis of the analytical solution. The results show that in the numerical calculation of DC bias of UHV transformers, the more accurate DC bias characteristics can be obtained by artificially increasing the series resistance and appropriately reducing the calculation time step. The results provide an effective solution for DC bias calculation of UHV transformers based on field-circuit coupling method. According to the actual structure parameters and electrical connection mode of UHV transformer, the field circuit coupling model of transformer is established, and the influence of series resistance and time step on the calculation result of DC bias magnetic field is analyzed. Artificially adding a series resistor changes the circuit structure of the transformer itself and causes the voltage at the rear side of the series resistance to deviate from the rated AC voltage applied. Therefore, the principle of voltage compensation is put forward, and the iterative calculation of voltage compensation is carried out. The calculation results show that voltage compensation can effectively eliminate the current calculation deviation caused by series resistance. On this basis, the simulation calculation of no-load DC bias magnetic field of UHV transformer under different DC bias current is carried out, and the excitation current and magnetic field characteristics are obtained. In order to improve the efficiency of no-load DC bias calculation of UHV transformer, a fast calculation method of no-load DC bias based on dynamic inductor-excitation current curve is proposed. This method avoids repeated calculation of the dynamic inductance of the magnetic field model under different DC bias current. The correctness and validity of the method are verified by comparing with the results of the field circuit coupling algorithm. At the same time, this method greatly saves calculation time and improves calculation efficiency. It provides a fast and simple calculation method for DC bias calculation of transformer. The DC bias of UHV transformer under load operation mode is studied and analyzed. The calculation results of DC component in the primary edge current can be close to the theoretical value of DC bias current and the accuracy of the calculation result can be improved by increasing the primary edge series resistance. This paper analyzes the influence of different load resistance on the current of UHV transformer under the condition of DC bias magnetic field, and obtains the variation rule of the load from overload to rating, from light load to high running state of no-load, and middle voltage winding. The calculation of DC bias and the analysis of current characteristics under different load operation modes are carried out. Based on the calculation of no-load and load current under different DC bias magnetoelectric current, the reactive power and eddy current loss are calculated and their characteristics are analyzed, which provides a reference for the evaluation of DC bias resistance of UHV transformer. The research work in this paper lays a foundation for the calculation of temperature rise of UHV transformer under DC bias.
【學(xué)位授予單位】:華北電力大學(xué)(北京)
【學(xué)位級(jí)別】:博士
【學(xué)位授予年份】:2017
【分類號(hào)】:TM411.3
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