【作者】 胡金磊；

【导师】 王克文；

【作者基本信息】 郑州大学 ， 电力系统及其自动化， 2005， 硕士

【摘要】 为了进一步考察概率特征根分析的计算误差,本文在多机电力系统动态模型的基础上,定量分析了多系统运行方式下的机电振荡模式的变化特性和阻尼转矩的变化规律,并与概率特征根分析的结果进行了比较。然后结合实际电网,分析了系统参数对小干扰稳定性的影响。 传统的稳定性分析往往基于有限数目的系统运行方式。在电力系统运行过程中,存在着许多随机扰动或不确定因素,系统的机电振荡模式和电磁阻尼转矩也将发生一定程度的变化。定量考查这种变化特性,可为进一步的稳定器配置和计及多运行条件的概率特征值分析提供依据。 模式分析中,主要关心的是发电机对机电振荡模式的参与程度。本文在每台发电机都配有零增益电力系统稳定器(PSS)的基础上,通过计算特征值对PSS增益的灵敏度来分析各发电机对机电振荡模式的参与程度。对八机系统的720个运行方式,重复计算720次。 文中主要分析了每个振荡模式中各发电机参与振荡的强弱顺序。为便于统计研究,按照参与度的概念,将模式中的发电机分为强相关,一般相关及弱相关机组。结果表明,在不同的运行条件下,发电机对机电振荡模式的参与程度一般会发生或多或少的变化;涉及较多参与机组的区域振荡模式更为复杂;但每个模式中的强相关机组在不同运行样本下的参与优势并未改变。与概率特征根分析所得结果一致。 由多机系统表达式,可以确定出PSS直接提供的阻尼转矩的解析表达。仍以八机系统的720个运行方式为样本,计算出每个运行方式下的各个PSS对每个振荡模式提供的阻尼转矩。分析标明,在采用的720运行方式下,各PSS对相应的主振荡模式,总能提供有效的正阻尼,尽管阻尼转矩的大小随相应发电机出力的改变而变化;在某些运行样本下,PSS向其它个别机电模式提供数值不大的负阻尼转矩。与概率特征根分析所得结果一致。 特征值灵敏度定量提供了参数影响的程度和趋势,并为改善系统稳定性提供指导。本文以某实际电网的典型运行方式为基础,计算了特征值对系统运行参数及网络参数的灵敏度,分析了发电机出力、PV电压、线路阻抗、变压器变比等对系统小干扰稳定性的影响。为稳定改善措施的选择提供依据。更多还原

【Abstract】 To further investigate the computational error in the probabilistic eigenvalue analysis, the multi-machine system dynamic model is used in this thesis to quantitatively study the varying characteristic of electromachenic oscillation modes and damping torques under system multi-operating conditions. Obtained result is compared with that of probabilistic eigenvalue analysis. Effects of system parameters on the system small signal stability are also analyzed on a practical system.The conventional stability analysis is usually based on one or several deterministic system operating conditions. However, in power system operation, there are many fluctuations and random factors, as a result, the electromachenic oscillation modes and electric torques will vary in some degree. The quantitatively investigation for the varying characteristics will provide the base for the further PSS settings and the probabilistic eigenvalue analysis involving multi-operating conditions.In modal analysis, the main concern is the participation degree of generators to oscillation modes. In this thesis, with the zero gain PSSs on all machines, the participation degrees of machines to the electromechanical modes are determined by computing the enginvalue sensitivities. For the 720 operating conditions of an eight-machine system, the computation is repeated 720 times.The order that each generator takes participation in oscillation modes is studied. For convenience, generators are classified as strong, moderate and weak related. Results show that the participation degree of generators to electromechanical oscillation modes is changed more or less under different operating conditions; the inter-area mode with more generators involved becomes more complicated; however, with the movement of operating condition, the participation orders of stronger participated generators in corresponding modes are less alterative in. From these, the result obtained from the probabilistic approach is validated.From the generalized multimachine representation, the electrical torque provided directly by PSS can be analytically represented. With the 720 operating conditions of the eight-machine system as samples, the damping torques provided by PSSs are calculated under all operating conditions. From the results, each PSS always providessignificant positive damping to the corresponding main oscillation mode under considered system operating samples, though the value of the damping torque is varied with the change of generator power; under some samples, a PSS may provide much small negative damping torques to other modes. These also indicate that the probabilistic technique is effective.Eigenvalue sensitivities quantitatively indicate the magnitude and trendency of parameter effects, and also give the direction for improving system stability. Based on the typical operating mode of a practical system, eigenvalue sensitivities with respect to system operating parameters and network parameters are computed. Effects of generator powers, PV voltages, line impedances, transformer taps on the system small signal stability are studied. These will provide the selection for the system stability improvement.更多还原