预防潮流转移引起连锁跳闸的紧急控制策略研究

发布时间：2018-10-12 17:41

【摘要】：伴随我国电力事业的不断发展,各区域电网之间的功率交换越来越频繁,使得线路的负担日益加重。在此背景下,因故障等因素而发生潮流转移进一步恶化了线路的工作条件,增加了发生连锁跳闸的风险。为此,本文研究预防潮流转移引起连锁跳闸的紧急控制策略,保证后备保护正确动作从而避免发生大停电事故,提高电力系统的安全运行水平。本文首先基于多支路切除的潮流转移特征,推导了线路潮流计算式,快速识别网络中的转移潮流。通过分析正常线路上潮流的组成以及各切除支路间转移潮流的分布差异,给出分别利用等效潮流和虚拟支路模型的方法来简化开断潮流的虚拟折返过程,进而得到识别故障后转移潮流的计算式。然后根据线路潮流的构成,分别提出了基于等效潮流的严重线路搜索算法和基于潮流转移密集度(FTIL)的严重线路搜索算法。前者采用等效潮流重新建立了一种新的路径搜索方案,创造性地将路径搜索扩展到多支路切除情况。同时采用路径扩展和修正相结合的闭环搜索策略,避免发生漏选;后者引入FTIL定义了广义潮流转移严重区,以此简化多支路潮流转移的分布,并基于广度优先搜索(BFS)算法界定该区域。将FTIL作为启发项引入BFS的终止条件,使节点扩展自动规避FTIL较小的区域,提高搜索严重线路的效率。针对线路过载问题,建立了基于虚拟控制单元与启发式搜索的减载方案。该方法首先利用同心松弛原理对网络进行缩减,筛选出优先参与调整过程的设备和元件;其次引入虚拟控制单位的概念,有效辨识出过载线路间的减载效果差异,提高传统灵敏度算法的分辨率。然后结合等量切机、切负荷控制策略,提出了最优可控单元的启发式搜索方法、最佳控制单元调整量的计算方法以及控制流程;最后采用轮次调整逐步朝着最优减载的方向进行调整直至过载消除,物理意义明确。其中每轮调整的最优控制点与调整量计算简单、快速,并在每轮调整末期将过载量进行反馈,实现闭环控制。最后以IEEE标准测试系统为例,对本文所提的算法进行了验证和分析。仿真结果表明,将故障扩展到多条线路情况,所提算法均能够达到预期效果,为预防潮流转移导致的大停电事故提供了较为完整的紧急控制策略,进一步提高了电网的安全稳定性。
[Abstract]:With the development of the electric power industry in China, the power exchange between the regional power grids is becoming more and more frequent, which makes the burden of the transmission line more and more serious. In this context, power flow transfer due to fault and other factors further deteriorate the working conditions of the line, and increases the risk of chain tripping. Therefore, this paper studies the emergency control strategy to prevent chain tripping caused by power flow transfer, to ensure the correct action of backup protection and to avoid power outages, and to improve the level of safe operation of power system. In this paper, based on the characteristics of multi-branch power flow transfer, a power flow calculation formula is derived to identify the power flow in the network quickly. By analyzing the composition of the power flow on the normal line and the distribution difference of the transfer power flow among the excised branches, the method of using the equivalent power flow and the virtual branch model to simplify the virtual reentry process of the power flow on the open fault is given respectively. Then, the calculation formula of power flow after fault identification is obtained. Then, according to the structure of line power flow, the algorithm of serious line search based on equivalent power flow and the algorithm of serious line search based on (FTIL) of power flow transfer intensity are proposed respectively. In the former, a new path search scheme is re-established by using equivalent power flow, and the path search is creatively extended to the case of multi-branch cutting. At the same time, the closed loop search strategy combined with path expansion and correction is adopted to avoid leakage. The latter uses FTIL to define the generalized power flow transfer serious area, which simplifies the distribution of multi-branch power flow transfer. And based on the breadth-first search (BFS) algorithm to define the region. By introducing FTIL as an heuristic term into the termination condition of BFS, the node can expand to avoid the smaller area of FTIL automatically, and improve the efficiency of searching serious circuit. A load reduction scheme based on virtual control unit (VCU) and heuristic search is proposed to solve the problem of line overload. Firstly, the network is reduced by the concentric relaxation principle, and the equipment and components that participate in the adjustment process are selected first. Secondly, the concept of virtual control unit is introduced to effectively identify the difference of load reduction effect between overload lines. Improve the resolution of traditional sensitivity algorithm. Then the heuristic search method of the optimal controllable unit, the calculation method of the optimal control unit's adjustment quantity and the control flow are put forward in combination with the constant cutting machine and the load control strategy. Finally, the cycle adjustment is adopted to adjust to the optimal load reduction direction until the overload is eliminated, and the physical meaning is clear. The calculation of the optimal control point and the adjustment amount is simple and fast, and the overloading is fed back at the end of each adjustment to realize the closed-loop control. Finally, the IEEE standard test system is taken as an example to verify and analyze the proposed algorithm. The simulation results show that the proposed algorithm can achieve the desired results by extending the fault to multiple transmission lines and provides a more complete emergency control strategy for the prevention of blackout caused by power flow transfer. It further improves the safety and stability of the power grid.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM761;TM744

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