多频失步场景下失步振荡中心特性与定位判据研究

发布时间：2019-06-10 19:29

【摘要】：近年来,随着特高压线路的不断建成投运,在提高电力系统输电上限的同时,也给电网的安全稳定运行带来更多不确定因素。区域电网的局部故障极有可能通过大区电网间的联络线快速远距离传播,引发严重连锁故障。并且随着电力系统运行方式日益复杂,电力系统失步后的失稳模式从传统的两频失步向多频失步转变的趋势越发显著,传统基于两频失步模型研究所得与失步振荡中心有关结论及判据其适用性存疑。因此亟需在多频失步场景下搭建电力系统失步振荡模型,研究失步振荡中心变化规律。本文在查阅了国内外大量文献资料的基础上,结合国家电网公司大电网重大专项(2012-2015)、国家电网公司总部科技项目(2016-2018),围绕多频失步场景下失步振荡中心特性与定位判据,开展了深入的研究。本文主要研究内容与成果如下:(1)搭建了多频失步场景下两种典型的失步振荡模型,基于所搭建的模型详细推导了多频失步场景下电压、电流及其频率的解析表达式。并发现在多频失步振荡过程中系统中任一点处的电压、电流及其频率与系统内等值电源电压幅值比、电源频差以及该点在系统内所处位置密切相关。(2)基于所得到的电气量解析表达式,通过数值仿真及实际电网算例仿真分析得到了在多频失步振荡场景下失步振荡中心的电压频率的变化特性。具体而言就是如果不同的观测点位于失步振荡中心的同一侧,那么这些观测点的电压频率波形的波动方向一致;如果线路上不同的观测点位于失步振荡中心的异侧,那么这些点电压频率波形的波动方向相反。(3)分析了电力系统内部可能对失步振荡中心动态迁移造成影响的因素。研究发现电力系统网架结构变化、电力系统内部配置的串联补偿器因故障退出运行均会改变电网等值阻抗,从而造成失步振荡中心的动态迁移;不恰当的切负荷操作则会因为对故障后的系统带来二次冲击,改变电力系统主导振荡模式,从而引发失步振荡中心动态迁移;而静止无功补偿器由于无法提供足够数量的无功支撑而会被闭锁退出运行,不会对失步振荡中心动态迁移造成影响。(4)基于所得失步振荡中心电压频率特性,本文给出了多频失步场景下失步振荡中心定位及动态迁移判据。首先对电压频率数据进行时间尺度对标的预处理,从而减少所需要计算分析的特征参数数量,简化了定位判据的实施流程。IEEE标准算例及某地区实际电网算例仿真验证了所提多频失步场景下失步振荡中心定位判据的快速性与准确性。
[Abstract]:In recent years, with the continuous completion and operation of UHV lines, while increasing the transmission upper limit of power system, it also brings more uncertain factors to the safe and stable operation of power grid. The local fault of regional power grid is likely to propagate quickly and remotely through the tie line between large area power grid, which will lead to serious chain fault. With the increasing complexity of the operation mode of the power system, the instability mode of the power system after losing step becomes more and more obvious from the traditional two-frequency out-of-step to the multi-frequency out-of-step. Based on the two-frequency out-of-step model, the traditional conclusions and criteria related to the out-of-step oscillation center are in doubt. Therefore, it is urgent to build the out-of-step oscillation model of power system in the multi-frequency out-of-step scenario, and to study the variation law of the out-of-step oscillation center. On the basis of consulting a large number of literature at home and abroad, this paper combines the major projects of the State Grid Company (2012 / 2015) and the Science and Technology Project of the headquarters of the State Grid Company (2016 / 2018). Based on the characteristics and positioning criteria of out-of-step oscillations in multi-frequency out-of-step scenarios, the characteristics and positioning criteria of out-of-step oscillations are deeply studied. The main contents and achievements of this paper are as follows: (1) two typical out-of-step oscillations models in multi-frequency out-of-step scenarios are built, and the analytical expressions of voltage, current and frequency in multi-frequency out-of-step scenarios are derived in detail. It is found that the voltage, current and frequency at any point in the system during the multi-frequency out-of-step oscillation are proportional to the amplitude of the equivalent power supply voltage in the system. The frequency difference of the power supply and the position of the point in the system are closely related. (2) based on the analytical expression of the electrical quantity, Through numerical simulation and simulation analysis of practical power grid examples, the variation characteristics of voltage frequency of out-of-step oscillation center in multi-frequency out-of-step oscillation scene are obtained. Specifically, if different observation points are located on the same side of the out-of-step oscillation center, then the fluctuation direction of the voltage frequency waveform of these observation points is the same. If different observation points on the line are located on the different side of the out-of-step oscillatory center, then the fluctuation direction of the voltage frequency waveform of these points is opposite. (3) the factors that may affect the dynamic migration of the out-of-step oscillatory center in the power system are analyzed. It is found that the change of power system grid structure and the failure of series compensator in power system will change the equivalent impedance of power network, which will lead to the dynamic migration of out-of-step oscillatory center. The improper load shedding operation will change the dominant oscillation mode of the power system because of the secondary impact on the system after the fault, which will lead to the dynamic migration of the out-of-step oscillatory center. However, the static reactive power compensator will be locked out of operation because it can not provide a sufficient amount of reactive power support, which will not affect the dynamic migration of the out-of-step oscillatory center. (4) based on the voltage and frequency characteristics of the out-of-step oscillatory center, In this paper, the criteria of center location and dynamic migration of out-of-step oscillations in multi-frequency out-of-step scenarios are given. First, the voltage frequency data is preprocessed by time scale to reduce the number of characteristic parameters that need to be calculated and analyzed. The implementation flow of the positioning criterion is simplified. The simulation results of the IEEE standard example and the actual power grid example in a certain area verify the rapidity and accuracy of the proposed out-of-step oscillatory center location criterion in the multi-frequency out-of-step scenario.
【学位授予单位】：武汉大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM712

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