交直流输电系统—直流功率调制技术的研究

发布时间：2018-01-20 00:12

本文关键词： 交直流电力系统小扰动分析低频振荡直流功率调制　出处：《南京理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：高压直流输电(HVDC)在远距离、大容量输电中具有明显优势。为实现区域电网互联,高压直流输电已成为我国电网的重要组成部分,同时也使电网结构和运行特性更加复杂,需要有效的方法来保证系统稳定运行。在交流输电的基础上,利用直流输电可控性强的特点,能够提高电网运行的稳定性。直流功率调制是一种附加的直流系统控制方式,用于拓展直流线路的控制能力。在交流系统受到扰动时,它根据交流系统的状态变化来调节直流线路的输送功率,以增强系统的阻尼,抑制输电线路的功率振荡,从而提高互联系统的稳定性。本文的主要工作如下:(1)分析了两端直流输电系统的基本原理、数学模型和不同控制方式的运行特性,阐述了交直流电力系统潮流计算和时域暂态分析的原理、方法和步骤,采用统一迭代法完成了潮流计算,本文采用交替求解法进行交直流电力系统的暂态仿真。(2)论述了低频振荡的表现形式及其产生机理,讨论了低频振荡的分析方法。推导了 Prony法的数学模型,完成了参数的选取,包括采样频率、时间长度以及模型阶次等。通过算例分析,验证了本文算法及程序的正确性。(3)建立了直流控制系统模型,包括换流器的定电流控制、定功率控制、定电压控制、定关断角控制等基本控制方式。建立了直流功率调制器模型。用线性化方法分析了直流功率调制对电力系统小扰动稳定性的影响,详述了小扰动稳定分析的步骤。(4)以四机两区域系统模型为研究对象,分析了直流功率调制对电力系统暂态稳定性的影响。计算结果表明直流功率调制可以有效地抑制功率振荡,提高系统的稳定性。
[Abstract]:HVDC (HVDC) has obvious advantages in long distance and large capacity transmission. In order to realize the interconnection of regional power grid, HVDC has become an important part of our power network. At the same time, it also makes the power network structure and operation characteristics more complex, need effective methods to ensure the stable operation of the system. On the basis of AC transmission, using the characteristics of high controllability of DC transmission. DC power modulation is a kind of additional DC system control method, which is used to expand the control ability of DC line. When the AC system is disturbed, DC power modulation can improve the stability of the power system. It adjusts the transmission power of DC line according to the state change of AC system, in order to enhance the damping of the system and restrain the power oscillation of transmission line. In order to improve the stability of interconnected systems, the main work of this paper is as follows: 1) the basic principles, mathematical models and operation characteristics of different control modes of HVDC systems are analyzed. The principle, method and procedure of power flow calculation and time-domain transient analysis of AC / DC power system are described. The unified iterative method is used to complete the power flow calculation. In this paper, alternating solution method is used to simulate the transient state of AC / DC power system. This paper discusses the analytical method of low frequency oscillation, deduces the mathematical model of Prony method, and completes the selection of parameters, including sampling frequency, time length and the order of model, etc. The correctness of the algorithm and program is verified. (3) the DC control system model is established, including constant current control, constant power control and constant voltage control of converter. The DC power modulator model is established and the influence of DC power modulation on the small disturbance stability of power system is analyzed by linearization method. The procedure of small disturbance stability analysis is described in detail. (4) the four-machine two-region system model is taken as the research object. The effect of DC power modulation on the transient stability of power system is analyzed. The results show that DC power modulation can effectively suppress the power oscillation and improve the stability of the power system.
【学位授予单位】：南京理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM721.1

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