特高压直流输电对交流电网的影响及点估计法的应用研究
发布时间：2018-11-10 21:06
【摘要】：特高压直流输电具有输送容量大、送电损耗小等优势,因此在我国得到快速和深入地发展,被广泛应用于远距离、大容量、高电压输电中,有力地推动我国“西电东送、南北互供、全国联网”的电力发展战略。当直流输电系统在单极运行方式下、处于调试或换相故障状态时,附近中性点接地变压器中可能流入直流电流,造成直流偏磁。直流偏磁造成励磁电流正负半周不对称,给变压器和交流电网的运行和安全造成诸多影响,如大量谐波的产生、变压器损耗增加、局部过热,变压器噪声增大、振动加剧等。现如今的电网交直并行,研究特高压直流输电单极大地回路运行对交流电网造成的各方面影响更具有具有很大的现实意义。 本文首先对变压器直流偏磁的机理以及特高压直流输电单极大地回路运行方式引起变压器中性点流入直流电流的原理进行了分析和解释,并对直流偏磁造成变压器、电网以及相关设备的危害和影响进行了研究和探讨。 本文利用边界元法和节点电压法推导了地表电位分布和中性点入地直流分布的计算原理,并分析了用CDEGS建模和仿真的各种影响因素。本文以±800kV向上特高压直流输电系统及浙江省北部电网为例,研究了其建模过程并仿真计算了其电位分布及中性点直流电流分布。 本文还引入点估计法及其相关理论,介绍了随机变量的数字特征,蒙特卡罗法和点估计法的计算原理和步骤。详细研究和分析了两点估计法和三点估计法的原理和不同,探讨了它们各自的优缺点。 根据引入的点估计法及相关理论,文章最后提出了一种基于点估计法的交流系统中性点直流电流分布计算方法。将其与CDEGS软件结合应用于变电站接地电阻计算以及交流系统中性点直流电流分布计算中,并通过实例进行验证和分析。实例证明该方法给出了具有概率意义的结果,使计算结果相较确定性计算更具实际意义和参考意义。
[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 卤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.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：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 卤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.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM721.1
【参考文献】
相关期刊论文 前10条
1 赵杰;黎小林;吕金壮;曾嵘;牛r，
本文编号：2323614
本文链接：https://www.wllwen.com/kejilunwen/dianlilw/2323614.html
教材专著
