该文主要研究了由开环模式耦合引起的统一潮流控制器(UPFC)与系统的强动态交互作用对系统机电振荡模式的影响.建立了含UPFC的多机电力系统闭环互联动态模型,将UPFC与系统分为两个互联开环子系统.当UPFC开环控制模式与开环机电模式在复平面上位置靠近时,相应的两闭环模式彼此相斥并趋向反方向移动,该模式耦合现象可造成闭环机电模式的阻尼严重恶化.依据阻尼转矩分析理论,该文从UPFC向系统中同步机提供阻尼贡献这一角度清晰阐释了开环模式耦合时UPFC对机电模式的动态影响.另外,提出一个量化指标,能够近似估计开环模式耦合情况下两个相关的闭环模式在复平面的相对位移.利用新英格兰10机系统与我国华东某500 kV等值电网算例详细说明和验证了所得结论.该文还比较了UPFC串、并联电压源换流器(VSC)对系统影响的强弱,并分析了UPFC潮流调节与安装地点两个因素对模式耦合的影响.%This paper investigated the impact of strong dynamic interaction caused by modal coupling between unified power flow controller (UPFC) and system on electromechanical oscillation modes (EOMs). A closed-loop interconnected dynamic model of multi-machine power system with a UPFC was derived, and the UPFC and the rest of system were modelled as two interconnected open-loop subsystems. Analysis in the paper indicates that when an open-loop UPFC control mode is close to an open-loop EOM of synchronous generators on the complex plane, two corresponding closed-loop modes intend to repulse each other to move approximatively towards opposite directions. Hence such modal coupling will cause damping of one closed-loop EOM to decrease heavily. The impact of strong dynamic interaction was explained clearly from the point of view that UPFC provide damping torque contribution to each generator according to damping torque analysis method. Moreover, a new quantitative index was proposed to approximately estimate the relative displacement of two corresponding closed-loop modes in complex plane under the condition of open-loop modal coupling. The New England 10-machine power system and a 500 kV actual equivalent power network of Eastern China were used to demonstrate and validated above analysis and conclusions. In addition, this paper compared the effects of series andparallel voltage source converters (VSCs) of UPFC on the system, and the influence of two factors, UPFC power flow regulation and installation location, on mode coupling was also analyzed.
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