發(fā)布時(shí)間：2018-10-29 20:59

【摘要】：隨著我國(guó)用電負(fù)荷水平的增加,以及能源區(qū)和負(fù)荷區(qū)的分布嚴(yán)重不均,遠(yuǎn)距離、大功率、跨區(qū)域輸電線(xiàn)路越來(lái)越多地出現(xiàn)我國(guó)的電力系統(tǒng)中,而直流輸電系統(tǒng)具有經(jīng)濟(jì)性好、運(yùn)行性能可靠和不存在交流輸電系統(tǒng)的穩(wěn)定性問(wèn)題等特點(diǎn),非常適合進(jìn)行遠(yuǎn)距離和大功率輸電。研究直流輸電系統(tǒng)過(guò)電壓,確定直流輸電線(xiàn)路的絕緣水平,對(duì)確定我國(guó)的能源安全,保障我國(guó)經(jīng)濟(jì)的發(fā)展具有重大的意義。直流線(xiàn)路接地故障是直流線(xiàn)路上最常見(jiàn)的故障,而且會(huì)產(chǎn)生線(xiàn)路上最嚴(yán)重的過(guò)電壓,因此對(duì)直流輸電系統(tǒng)單極接地過(guò)電壓進(jìn)行計(jì)算研究是有必要的。 本文先對(duì)直流輸電系統(tǒng)單極接地過(guò)電壓的原理進(jìn)行理論分析,找出影響過(guò)電壓的相關(guān)因素。再對(duì)直流輸電系統(tǒng)進(jìn)行電路等效處理,根據(jù)等效電路圖列出各點(diǎn)電壓和電流的狀態(tài)微分方程,用改進(jìn)歐拉法對(duì)典型直流輸電系統(tǒng)單極接地過(guò)電壓進(jìn)行計(jì)算,結(jié)果表明故障點(diǎn)位于線(xiàn)路中點(diǎn)時(shí)會(huì)在非故障極產(chǎn)生最高的過(guò)電壓；線(xiàn)路越短,線(xiàn)路上過(guò)電壓水平越高；故障接地電阻能降低故障時(shí)引起的電壓波的暫態(tài)分量,故障接地電阻越大,過(guò)電壓幅值越小。 為對(duì)直流輸電系統(tǒng)單極接地過(guò)電壓進(jìn)行精確計(jì)算和詳細(xì)分析,選用PSCAD軟件,根據(jù)云廣特高壓直流輸電系統(tǒng)的實(shí)際參數(shù),建立了特高壓直流輸電系統(tǒng)的仿真模型,詳細(xì)計(jì)算了直流濾波器、平波電抗器,線(xiàn)路長(zhǎng)度,故障接地電阻、負(fù)荷水平、大地電阻率和故障位置等因素對(duì)直流輸電系統(tǒng)單極過(guò)電壓的影響,以及故障時(shí)換流站內(nèi)各設(shè)備的過(guò)電壓。計(jì)算結(jié)果表明最大過(guò)電壓出現(xiàn)在故障點(diǎn)為線(xiàn)路中點(diǎn)時(shí),直流濾波器、負(fù)荷水平和大地電阻率對(duì)過(guò)電壓有一定影響,負(fù)荷水平越高,過(guò)電壓越大,大地電阻率越高,過(guò)電壓越低,但是影響不大,平波電抗器電感值和配置方式對(duì)過(guò)電壓有較大影響,電感值越大,過(guò)電壓越小,全部裝設(shè)在極母線(xiàn)性上時(shí)要比分別裝在極母線(xiàn)和中性母線(xiàn)上時(shí)的過(guò)電壓要小,線(xiàn)路長(zhǎng)度和故障接地電阻對(duì)過(guò)電壓的影響與前面用改進(jìn)歐拉法計(jì)算得到的結(jié)論一致,當(dāng)線(xiàn)路長(zhǎng)度為800km時(shí)線(xiàn)路上最大的過(guò)電壓達(dá)到1.7pu,值得引起重視,發(fā)生接地故障時(shí)會(huì)在換流站設(shè)備上產(chǎn)生一定的過(guò)電壓,直流濾波器因更靠近線(xiàn)路端,所以受到的影響較大,當(dāng)故障點(diǎn)位于換流站附近時(shí),會(huì)在其電感上引起較大的過(guò)電壓,對(duì)其絕緣產(chǎn)生威脅,值得引起注意。對(duì)于限制過(guò)電壓的措施,可選擇在線(xiàn)路中點(diǎn)處安裝避雷器,能有效限制過(guò)電壓。
[Abstract]:With the increase of power load level in our country, and the distribution of energy and load areas is seriously uneven, long-distance, high-power, cross-regional transmission lines more and more appear in the power system of our country, but the direct current transmission system has good economy. It is very suitable for long distance and high power transmission due to its reliable operation performance and the absence of stability problems of AC transmission systems. It is of great significance to study the overvoltage of HVDC transmission system and determine the insulation level of HVDC transmission lines to determine the energy security of our country and ensure the economic development of our country. DC grounding fault is the most common fault on DC line, and it will produce the most serious overvoltage on the line. Therefore, it is necessary to calculate the unipolar grounding overvoltage of HVDC transmission system. In this paper, the principle of unipole grounding overvoltage in HVDC system is analyzed theoretically, and the related factors affecting overvoltage are found out. Then the equivalent circuit of HVDC system is treated, according to the equivalent circuit diagram, the state differential equations of voltage and current at each point are listed, and the single-pole grounding overvoltage of typical HVDC transmission system is calculated by improved Euler method. The results show that when the fault point is at the midpoint of the line, the highest overvoltage will be generated at the non-fault pole. The shorter the line is, the higher the over-voltage level on the line is, and the fault grounding resistance can reduce the transient component of the voltage wave caused by the fault, the larger the fault grounding resistance, the smaller the overvoltage amplitude. In order to accurately calculate and analyze the unipolar grounding overvoltage of HVDC system, the simulation model of UHV HVDC system is established according to the actual parameters of Yunguang UHVDC transmission system by using PSCAD software. The effects of DC filter, flat-wave reactor, line length, fault grounding resistance, load level, earth resistivity and fault location on unipolar overvoltage of HVDC transmission system are calculated in detail. And the overvoltage of the equipment in the converter station when the fault. The calculation results show that the DC filter, load level and earth resistivity have a certain influence on the overvoltage when the maximum overvoltage occurs at the fault point. The higher the load level, the greater the overvoltage, the higher the earth resistivity and the lower the overvoltage. However, the influence of the inductance and configuration of the flat-wave reactor on the overvoltage is great. The larger the inductance, the smaller the overvoltage, and the smaller the overvoltage is when all of them are installed on the pole busbar and the neutral bus, respectively. The effect of line length and fault grounding resistance on overvoltage is consistent with the results obtained by the improved Euler method. When the line length is 800km, the maximum overvoltage on the line is 1.7 pu. it is worthy of attention. When grounding fault occurs, a certain overvoltage will be generated on the converter station equipment. Because the DC filter is closer to the line end, it will be greatly affected. When the fault point is near the converter station, it will cause a larger overvoltage on its inductance. The threat to its insulation deserves attention. For the measures to limit the overvoltage, the lightning arrester can be installed at the midpoint of the line, which can effectively limit the overvoltage.
【學(xué)位授予單位】：廣西大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類(lèi)號(hào)】：TM721.1

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