特高壓直流輸電對交流電網(wǎng)的影響及點(diǎn)估計(jì)法的應(yīng)用研究
發(fā)布時(shí)間：2018-11-10 21:06
【摘要】：特高壓直流輸電具有輸送容量大、送電損耗小等優(yōu)勢,因此在我國得到快速和深入地發(fā)展,被廣泛應(yīng)用于遠(yuǎn)距離、大容量、高電壓輸電中,有力地推動(dòng)我國“西電東送、南北互供、全國聯(lián)網(wǎng)”的電力發(fā)展戰(zhàn)略。當(dāng)直流輸電系統(tǒng)在單極運(yùn)行方式下、處于調(diào)試或換相故障狀態(tài)時(shí),附近中性點(diǎn)接地變壓器中可能流入直流電流,造成直流偏磁。直流偏磁造成勵(lì)磁電流正負(fù)半周不對稱,給變壓器和交流電網(wǎng)的運(yùn)行和安全造成諸多影響,如大量諧波的產(chǎn)生、變壓器損耗增加、局部過熱,變壓器噪聲增大、振動(dòng)加劇等。現(xiàn)如今的電網(wǎng)交直并行,研究特高壓直流輸電單極大地回路運(yùn)行對交流電網(wǎng)造成的各方面影響更具有具有很大的現(xiàn)實(shí)意義。 本文首先對變壓器直流偏磁的機(jī)理以及特高壓直流輸電單極大地回路運(yùn)行方式引起變壓器中性點(diǎn)流入直流電流的原理進(jìn)行了分析和解釋,并對直流偏磁造成變壓器、電網(wǎng)以及相關(guān)設(shè)備的危害和影響進(jìn)行了研究和探討。 本文利用邊界元法和節(jié)點(diǎn)電壓法推導(dǎo)了地表電位分布和中性點(diǎn)入地直流分布的計(jì)算原理,并分析了用CDEGS建模和仿真的各種影響因素。本文以±800kV向上特高壓直流輸電系統(tǒng)及浙江省北部電網(wǎng)為例,研究了其建模過程并仿真計(jì)算了其電位分布及中性點(diǎn)直流電流分布。 本文還引入點(diǎn)估計(jì)法及其相關(guān)理論,介紹了隨機(jī)變量的數(shù)字特征,蒙特卡羅法和點(diǎn)估計(jì)法的計(jì)算原理和步驟。詳細(xì)研究和分析了兩點(diǎn)估計(jì)法和三點(diǎn)估計(jì)法的原理和不同,探討了它們各自的優(yōu)缺點(diǎn)。 根據(jù)引入的點(diǎn)估計(jì)法及相關(guān)理論,文章最后提出了一種基于點(diǎn)估計(jì)法的交流系統(tǒng)中性點(diǎn)直流電流分布計(jì)算方法。將其與CDEGS軟件結(jié)合應(yīng)用于變電站接地電阻計(jì)算以及交流系統(tǒng)中性點(diǎn)直流電流分布計(jì)算中,并通過實(shí)例進(jìn)行驗(yàn)證和分析。實(shí)例證明該方法給出了具有概率意義的結(jié)果,使計(jì)算結(jié)果相較確定性計(jì)算更具實(shí)際意義和參考意義。
[Abstract]:UHVDC transmission has the advantages of large transmission capacity and low transmission loss, so it has been rapidly and deeply developed in China, and has been widely used in long-distance, large-capacity and high-voltage transmission. North-south mutual supply, national networking, "electricity development strategy." When the DC transmission system is in the state of debugging or commutation fault under the unipolar operation mode, the DC current may flow into the nearby neutral grounding transformer, resulting in DC bias. DC bias results in positive and negative half-cycle asymmetry of excitation current, which has a lot of effects on the operation and safety of transformer and AC power network, such as the generation of a large number of harmonics, the increase of transformer loss, the local overheating, the increase of transformer noise and the aggravation of vibration, etc. Nowadays, the power grid is parallel to each other, so it is of great practical significance to study the influence of UHVDC unipolar earth circuit on the AC power grid. In this paper, the mechanism of DC bias of transformer and the principle of transformer neutral point flowing into DC current caused by the operation mode of unipolar earth circuit of UHVDC transmission are analyzed and explained, and the transformer is caused by DC bias. The harm and influence of power grid and related equipment are studied and discussed. In this paper, the calculation principle of ground surface potential distribution and neutral point DC distribution is derived by using boundary element method and node voltage method, and various influencing factors of modeling and simulation with CDEGS are analyzed. In this paper, the modeling process of 鹵800kV upward UHVDC transmission system and the northern power grid of Zhejiang Province are studied and its potential distribution and neutral DC current distribution are simulated and calculated. This paper also introduces the point estimation method and its related theory, introduces the numerical characteristics of random variables, the calculation principle and steps of Monte Carlo method and point estimation method. The principle and difference of two-point estimation and three-point estimation are studied and analyzed in detail, and their respective advantages and disadvantages are discussed. According to the introduced point estimation method and related theory, this paper presents a method to calculate the DC current distribution of neutral point in AC system based on point estimation method. It is combined with CDEGS software to calculate grounding resistance of substation and DC current distribution of neutral point in AC system, and it is verified and analyzed by an example. Examples show that the method gives the results with probabilistic significance and makes the results more practical and reference than deterministic calculation.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TM721.1
[Abstract]:UHVDC transmission has the advantages of large transmission capacity and low transmission loss, so it has been rapidly and deeply developed in China, and has been widely used in long-distance, large-capacity and high-voltage transmission. North-south mutual supply, national networking, "electricity development strategy." When the DC transmission system is in the state of debugging or commutation fault under the unipolar operation mode, the DC current may flow into the nearby neutral grounding transformer, resulting in DC bias. DC bias results in positive and negative half-cycle asymmetry of excitation current, which has a lot of effects on the operation and safety of transformer and AC power network, such as the generation of a large number of harmonics, the increase of transformer loss, the local overheating, the increase of transformer noise and the aggravation of vibration, etc. Nowadays, the power grid is parallel to each other, so it is of great practical significance to study the influence of UHVDC unipolar earth circuit on the AC power grid. In this paper, the mechanism of DC bias of transformer and the principle of transformer neutral point flowing into DC current caused by the operation mode of unipolar earth circuit of UHVDC transmission are analyzed and explained, and the transformer is caused by DC bias. The harm and influence of power grid and related equipment are studied and discussed. In this paper, the calculation principle of ground surface potential distribution and neutral point DC distribution is derived by using boundary element method and node voltage method, and various influencing factors of modeling and simulation with CDEGS are analyzed. In this paper, the modeling process of 鹵800kV upward UHVDC transmission system and the northern power grid of Zhejiang Province are studied and its potential distribution and neutral DC current distribution are simulated and calculated. This paper also introduces the point estimation method and its related theory, introduces the numerical characteristics of random variables, the calculation principle and steps of Monte Carlo method and point estimation method. The principle and difference of two-point estimation and three-point estimation are studied and analyzed in detail, and their respective advantages and disadvantages are discussed. According to the introduced point estimation method and related theory, this paper presents a method to calculate the DC current distribution of neutral point in AC system based on point estimation method. It is combined with CDEGS software to calculate grounding resistance of substation and DC current distribution of neutral point in AC system, and it is verified and analyzed by an example. Examples show that the method gives the results with probabilistic significance and makes the results more practical and reference than deterministic calculation.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TM721.1
【參考文獻(xiàn)】
相關(guān)期刊論文 前10條
1 趙杰;黎小林;呂金壯;曾嶸;牛r，
本文編號：2323614
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