基于网络参数等值理论的不对称运行故障分析与计算

发布时间：2018-05-19 07:01

本文选题：对称分量法 + 输电线路解耦　；参考：《广西大学》2017年硕士论文

【摘要】：电力系统在运行过程中,会发生各种不同类型的故障,而电力系统故障的分析计算对于电力系统的规划设计、事故分析以及电力系统的整定运行都有着十分重要的指导作用,所以人们对电力系统故障分析计算方法的研究从来没有停止过。我国电源点和负荷中心分布极其不合理,基于这种基本国情,高压、特高压输电被提上了日程;但出于经济和方便等角度的考虑,高压、特高压输电线路一般不进行换位,这就造成了输电线路三相参数的不对称。本文介绍了一种运用对称分量法来分析计算三相参数不对称的输电线路故障的计算方法,论文从磁链的角度出发,将三相阻抗表示为关于三相电流的关系式,实现了输电线路三相阻抗的解耦。运用网络等值理论,将三相参数不对称的输电线路等效变换为发生了某种类型的断线故障的三相参数对称的输电线路,当三相参数不对称的输电线路有故障发生时,则可以看作是等效变换后的三相参数对称的输电线路发生了复杂故障,对于复杂故障的计算,本文运用对称分量法结合口网络理论来进行分析计算。口网络理论就是把每一个故障点看作是一个故障端口,根据故障端口绘制三序网络图,列写三序节点导纳矩阵,求逆得到三序阻抗矩阵,根据三序阻抗矩阵可以得到三序口阻抗口矩阵,列写三序电压方程和故障边界条件方程,联立方程求解就可以得到故障时的电压电流。三相阻抗是关于三相电流的表达式,当流过输电线路的三相电流发生改变时等效三相阻抗也会发生改变,对于输电线路初始阻抗的计算,假设流过输电线路的初始电流是三相对称的。用初始的输电线路三相阻抗进行故障计算,可以得到初始的故障电压和电流;将流过输电线路的初始故障电流代回输电线路三阻抗公式,又可以求得新的输电线路三相阻抗,从而得到新的输电线路的正负零序导纳,从而可以得到新的三序节点导纳矩阵,求逆得到新的三序阻抗矩阵,根据三序阻抗矩阵可以求得新的三序口阻抗矩阵,列写新的三序电压方程和故障边界条件方程,求解出新的故障电压电流,重复以上步骤,直到前后两次计算的故障电流的百分误差不超过1%;此时,得到的电压、电流就是输电线路三相参数不对称发生故障时的故障电压、电流。通过matlab编程对本文算法进行编程,利用EMTP对系统模型进行仿真,将两者的结果进行比较,验证本文算法的正确性。
[Abstract]:In the process of power system operation, various kinds of faults will occur, and the analysis and calculation of power system faults play an important role in the planning and design of power system, the analysis of accidents and the setting operation of power system. Therefore, the study of power system fault analysis and calculation methods has never stopped. The distribution of power points and load centers in China is extremely unreasonable. Based on this basic situation, high-voltage and ultra-high voltage transmission lines are put on the agenda. However, for reasons of economy and convenience, high-voltage and ultra-high voltage transmission lines generally do not carry out transposition. This results in the asymmetry of three-phase parameters of transmission lines. In this paper, a method of calculating the fault of transmission lines with asymmetric three-phase parameters by using symmetric component method is introduced. In this paper, the three-phase impedance is expressed as the relation of three-phase current from the point of view of flux linkage. The decoupling of three-phase impedance of transmission line is realized. By using the network equivalence theory, the three-phase transmission line with asymmetric parameters is transformed into a transmission line with a certain type of break-line fault. When the three-phase parameter asymmetric transmission line has a fault, It can be regarded as the complex fault of the transmission line with symmetrical three-phase parameters after equivalent transformation. For the calculation of the complex fault, the symmetric component method combined with the theory of port network is used to analyze and calculate the complex fault. The theory of port network is to treat each fault point as a fault port, draw the three-sequence network diagram according to the fault port, write the three-sequence node admittance matrix, and obtain the three-sequence impedance matrix by inverse. According to the three-sequence impedance matrix, the three-sequence impedance port matrix can be obtained, and the three-sequence voltage equation and the fault boundary condition equation can be set up, and the voltage and current in the fault can be obtained by solving the simultaneous equation. Three-phase impedance is the expression of three-phase current. When the three-phase current of transmission line changes, the equivalent three-phase impedance will also change. Assume that the initial current flowing through the transmission line is three-phase symmetric. The initial fault voltage and current can be obtained by using the initial three-phase impedance of the transmission line, and the three-phase impedance formula of the transmission line can be replaced by the initial fault current flowing through the transmission line, and a new three-phase impedance of the transmission line can be obtained. Thus, the positive and negative zero-sequence admittance of a new transmission line can be obtained, a new three-sequence node admittance matrix can be obtained, a new three-sequence impedance matrix can be obtained by inverse, and a new three-sequence impedance matrix can be obtained according to the three-sequence impedance matrix. Write a new three-sequence voltage equation and a fault boundary condition equation, solve the new fault voltage and current, repeat the above steps until the error of the fault current calculated twice before and after is less than 1 percent; in this case, the resulting voltage, Current is the fault voltage and current when the three-phase parameters of transmission line are not symmetrical. The algorithm is programmed by matlab, the system model is simulated by EMTP, and the results are compared to verify the correctness of the algorithm.
【学位授予单位】：广西大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM75

【参考文献】