【作者】 李慧玲；

【导师】 余贻鑫；

【作者基本信息】 天津大学 ， 电力系统及其自动化， 2005， 硕士

【摘要】 近年来世界上频频发生电力系统因电压失稳而导致系统崩溃,造成大面积停电的事故,这些事故的发生一般是由于长线路重负荷、负荷大量集中的受端系统突然失去较大电源以及受端负荷的增长过快等情况引起的。同时随着电力市场的快速发展,电力系统的运行愈发接近其稳定极限,因此系统出现电压失稳的可能性也随之大大增加。为了减少和避免由于电压失稳而引起电力事故的发生,电力系统的研究人员已经进行了大量的工作。逐点法是被广泛采用的方法,但由于它对偶然事故表中所列的各种运行条件都需依次检验其安全性,这样使得计算工作量很大,限制了分析潜在偶然事故的数量。因此利用“域”的方法研究系统的电压稳定性逐渐得到了重视,它不仅为运行人员提供了系统的整体稳定性测度,同时也可以避免大量复杂的在线计算。由于电压失稳主要表现为鞍-节点分岔,即单调失稳,因此研究静态电压稳定域边界是本论文的一项主要内容。电力系统在注入空间是一个维数极高的典型的非线性系统,在全维空间内研究静态电压稳定域是不现实的。同时在实际电力系统的生产运行中,电力部门的调度运行人员习惯于关注某些关键线路的传输功率极限,用此来判断系统的电压稳定性。因此我们选择在割集空间上研究静态电压稳定域,这种方法既达到了使复杂电力系统降维的目的,又方便了运行人员对于系统稳定性的监视。由于电压稳定问题的局部性质,系统基于静态电压稳定的弱节点的分布在地理上也呈相对集中的状况,因此我们可以据此确定一个或几个临界割集将相对集中的某一部分弱节点与系统的其他部分分隔开,监控这些割集上线路的潮流就能有效地获得系统的电压稳定性状况。仿真分析表明,给定系统网络结构,在不同的负荷增长方式和发电分配方式下,割集空间静态电压稳定域的边界可近似描述为一个或少数几个超平面,此时保证电压稳定的系统的运行点均位于所有临界割集超平面之内侧,而系统的电压不稳定运行点必位于一临界割集的超平面之外侧。超平面形式的电压稳定域边界表达式为在线安全监视、评估和优化提供了简明、方便的解析工具。最后基于上述电力系统割集空间静态电压稳定域的理论,本文阐述了电力系统电压稳定域在线监控软件模块的框架和编制。更多还原

【Abstract】 In recent years voltage instability has aroused several blackouts. It is mainly dueto long-distance transmission lines and heavy loads, loss of electrical source at sinkwith concentrative load or load increasing quickly at sink. In addition with theworld-wide development of electric market, the systems are more often operating neartheir stability limits and there is large probability of voltage instability. In order toreduce or even avoid blackouts led by voltage instability, researchers have done a lotof work. Although the ‘point-wise’ approach has been widely used in the past, it needsto check the security of operation condition for every contingency in contingency set,which is time-consuming. Hence gradually we pay more attention to the“region-wise” approach. It will not only provide systematic and global information foroperators but also avoid enormous complicated computations online. Because voltageinstability is mainly relative to saddle-node bifurcation, static voltage stability region(SVSR) boundary is our focus in the thesis. Since SVSR in injection space is with strong nonlinearity and extremely largedimension, it is difficult to describe it through a simple analytical expression in thewhole space. Moreover operators have been monitoring stability constraints throughpower flows on critical branches for long time. Therefore displaying SVSR in cut-setspace is our choice. It not only offers an efficient dimension reduction method butalso is convenient to monitor power systems voltage stability margin. As we all know, voltage instability comes of essentially a local part of powersystem. And usually weak nodes also centralize in a certain part of system, which isconvenient for us to determine the cut-set. We can choose right critical cut-set(s) toseparate the system into two parts i.e. the region(s) with weak nodes and the rest ofthe power system. By monitoring the power flows on the branches in the criticalcut-set(s) we can get more useful information about power system voltage stability.Studies on various power systems with different operating conditions haveshowed that SVSR boundary in cut-set complex power space can be approximated byone or several hyper-planes with satisfactory accuracy. All operating points that canguarantee system voltage stability are within the region restricted by the hyper-planesin cut-set complex power spaces. Points that lead to static voltage instability areexcluded from the region. The hyper-plane which describes the boundary of SVSR incut-set power space makes it very easy to analyze, assess and optimize power system.Finally based on static voltage stability region in cut-set space theory mentionedabove, we have put forward the framework of power system stability region real timeanalysis package.更多还原