【作者】 张杰；

【导师】 罗隆福；

【作者基本信息】 湖南大学 ， 电气工程， 2010， 博士

【摘要】 换流变压器是直流输电系统中的重大技术装备,为了从根本上解决传统直流输电网侧滤波所不能解决的谐波与无功对换流变压器的不良影响,“自耦补偿与谐波屏蔽换流变压器”(简称新型换流变压器)以及相应的感应滤波技术被提出,并获得了专利。目前该专利的推广应用已获得湖南省“十五”、“十一五”重大科技专项(05GK1002-1)、(06GK1003-1)以及国家自然科学基金(50907018)资助。为了实现该专利的工程化,需要完成大量的理论分析和科学试验工作。由于换流变压器的可靠性与可用性对于整个直流输电系统来说很关键,其安全运行与否,将直接关系到整个直流输电系统能否连续、可靠和稳定地工作。因此本论文围绕着新型换流变压器的故障建模和保护原理开展了下面的研究工作：详细研究了新型换流变压器的接线方案、结构型式及其工作原理。分析了直流输电新技术研究平台的构造以及平台各部分的功能,并介绍了新型换流变压器和与之配套的滤波装置的参数。基于直流输电新技术研究平台,对传统直流输电以及基于新型换流变压器的直流输电系统在谐波抑制、节能降耗、减振降噪、改善换相方面进行了实验对比研究,对比结果表明基于新型换流变压器的直流输电系统相对于传统直流输电在这些方面具有明显的优越性,从而表明了新型换流变压器原理的正确性,具有良好的应用前景。与传统的换流变压器相比,新型换流变压器具有独特的绕组联结方式,而在现有的电力系统仿真软件中所用的均是传统意义上的变压器模型,没有具有特殊绕组联结方式的新型换流变压器仿真模型。本论文基于互耦的概念,把新型换流变压器看作多个线圈的耦合,从而建立了新型换流变压器的多线圈耦合模型。在此基础上,根据新型换流变压器特殊的接线方式,结合有限元仿真软件,采用MATLAB里的多线圈耦合模块分别设计了新型换流变压器正常状态和发生内部故障时的仿真模型,并设计了非线性电感支路来模拟新型换流变压器铁心饱和特性,从而设计出能仿真新型换流变压器正常运行、内外部故障、励磁涌流的通用仿真模型。新型换流变压器具有特殊的绕组连接方式,因此需要研究合适的数学方法来推导新型换流变压器正常状态和内部故障数学模型,并计算其任意的内外部短路故障。电网络分析中的稀疏列表法和添加法在建立电网络方程方面各有特色,但是关于如何应用稀疏列表法或添加法建立含互感支路的电网络方程以及根据节点或支路的变化应用稀疏列表法或添加法形成新网络方程的方法目前还没有相关文献介绍。本论文将新型换流变压器看作含互感支路的网络,根据新型换流变压器特殊的绕组连接方式和相应的耦合电路,首次分别将稀疏列表法和添加法应用于建立含互感支路的电网络方程,从而建立了新型换流变压器正常状态的基本数学模型。为了便于在实际工程中灵活运用,对基本模型进行拓展,建立了更为详细的计及中性点接地阻抗的节点拓展模型、计及副边角接三角形绕组抽头处滤波装置的支路拓展模型。基于所建立的正常状态数学模型,根据电网络有向图节点或支路的变化,分别采用稀疏列表法和添加法建立了新型换流变压器内部故障数学模型而且对新型换流变压器各种内外部短路故障进行了计算。在研究常规变压器差动保护原理的基础上,对新型换流变压器差动保护原理进行了研究。在分析新型换流变压器绕组接线方案和三绕组之间特定匝比关系的基础上,根据新型换流变压器是否接滤波装置,分别推导出了相应的新型换流变压器两侧电流关系,进而分别提出两种差动保护接线的理论方程式,据此给出了相应的模拟式和微机式差动保护接线方案图。详细对比分析了新型换流变压器正常运行、内外部故障状况时两种保护接线方案的动作特性,并根据差动保护方案动作特性分析结果选择出适合新型换流变压器的差动保护接线方案。对新型换流变压器励磁涌流产生机理进行了研究,并从电路基本原理的角度对励磁涌流有可能引起新型换流变压器差动保护方案误动的根本原因进行了分析,鉴于差动保护方案在鉴别新型换流变压器励磁涌流方面的不足,对一种抛开差动保护思路、综合利用变压器电压和电流信息量的新型微机型变压器保护方案—基于模型的变压器保护原理进行了研究,在数学推理验证该保护原理同样适用于新型换流变压器的前提下,将该保护原理的思路运用于新型换流变压器保护方案设计中,从而制定了基于模型的单相和三相新型换流变压器微机主保护方案。考虑到微机保护工作时用差分代替微分引起的误差可能会使新型换流变压器保护误动,对已建立的保护判据动作特性方程进行梯形积分来构成新的保护判据。更多还原

【Abstract】 Converter transformers are important technical equipments. Traditional HVDC set filters in net side to eliminate harmonic, but this filtering method couldn’t solve the problem that harmonic and reactive components bring negative effects to converter transformers. In order to solve problem radically, coupling-compensation and harmonic-shielding converter transformer, that is the new converter transformer, and its corresponding inducing filter technology are put forward. It is a patent, and its application has been funded by the key science & technology project of the Tenth Five Year Plan(05GK 1002-1) and of the Eleventh Five Year Plan of Hunan Province(06GK1003-1) and National Natural Science Foundation of China(50907018).In order to apply the patent into projects, there are lots of academic analyses and scientific test work need to be finished. The reliability and usability of converter transformers are very important to the whole HVDC system, and the safety of converter transformers operation influences the continuity, credibility and stability of whole HVDC system. So, this thesis surrounds faulty model building and protection principle for new converter transformer to develop following work:The wiring scheme, structure type and operating principle are studied in detail. The structure and function of each part of one platform for research of new technology in HVDC are analyzed, and the parameters of the new converter transformer and corresponding filters are introduced. Based on the platform, the HVDC based on new converter transformer and traditional HVDC are contrasted by experiments in the aspects of eliminating harmonic, saving energy and lowering costs, decreasing vibration and noises, and improving phase conversion, the results of which show the HVDC based on the new converter transformer has obvious advantage in the above aspects, which indicate that principle of the new converter transformer is correct and has good applied foreground.Compared with the traditional converter transformer, the new converter transformer has unique connection mode. But the exiting simulation soft wares don’t directly provide the simulation model for the new converter transformer with special winding wiring mode. Based on the coupling concept, this thesis regard the new converter transformer as mutual coupling multi-coils, and then the models of mutual coupling multi-coils are established, based on which, according to the special winding wiring mode of the new converter transformer, with a finite element simulation software, multi-coil coupling module of MATLAB was used to design the normal and internal faulty simulation model of the new converter transformer separately, and a nonlinear inductance branch was designed to simulate the characteristic of saturated core of the new converter transformer. So the universal simulation models which could simulate normal operation, external and internal faulty and inrush current of the new converter transformer have been designed.The new converter transformer has special winding wiring mode, so it is essential to study appropriate mathematical methods to derive normal and internal faulty mathematical models, calculate arbitrary external and internal faults of the new converter transformer. Sparse tabular method and additive process in electric network analysis have different advantages in the aspect of establishing network equations, but how to use sparse tabular method or additive process to build the equations of electric network containing coupled branches and form new equations according to the changes of nodes or branches are not introduced in any article at present. this thesis regarded the new converter transformer as a electric network containing coupled branches, according to winding wiring mode and corresponding coupled circuit of which, this thesis respectively adopts sparse tabular and additive process to directly build the equations of electric network containing coupled branches, and the normal condition’s basic mathematical model of the new converter transformer is established. Considering that models can be selected flexibly in practical projects, through evolution of the basic mathematical model, the node evolution model including the earth impedance of the neutral point, the branch evolution model including the filters connected with the secondary corner delta winding’s tap are established respectively. Based on normal mathematical model, according to the change of nodes or branches, sparse tabular method and additive process are used respectively not only to build the interior fault condition’s mathematical models but also calculate all kinds of inner and external faults of the new converter transformer.Based on the study of principle of differential protection for ordinary transformer, the principles of differential protection for new converter transformer are researched. Based on the analysis on the special windings wiring mode and turns ration relation of the new converter transformer, according to the filters connected or not connected to the new converter transformer, the relation between bilateral currents of the new converter transformer were separately gotten, and based on which, two differential protection wiring schemes were separately put forward, and corresponding simulation and microcomputer differential protection wiring schemes were separately put forward too. The action characteristic of two differential protection wiring schemes were analyzed and compared according to all kinds of operation condition of the new converter transformer, and according to the results, the differential protection wiring scheme which is better has been selected.Mechanism of inrush current of the new converter transformer are studied, and the ultimate reasons why inrush current maybe cause the differential protection scheme act incorrectly has been analyzed from the angle of basic principle of the circuit. Considering the shortage of differential protection scheme in distinguishing inrush current of the new converter transformer, the principle of a new microcomputer protection scheme based on the transformer model which casts the method of differential protection and utilize synthetically the information of voltages and currents of a transformer is studied. The protection scheme based on the transformer model was proved to be also suitable for the new converter transformer by mathematic illation. Based on this precondition, this thesis applied the protection scheme based on the transformer model to the protection scheme design for single-phase and three-phase new converter transformers. Considering the use of difference instead of differential possibly maybe cause prodigious error and malfunction when microcomputer protection devices run, the new criterion was instituted by applying the trapezoidal integration to the old action equations.更多还原