【作者】 孔瑾；

【导师】 王葵；

【作者基本信息】 山东大学 ， 电力系统及其自动化， 2013， 硕士

【摘要】 近年来分布式发电技术(Distribution Generation:DG)得到了快速的发展,为提高分布式电源运行的安全性和可靠性,一般都将其并入电网运行。随着DG的并网运行,会使配电系统的短路电流的大小、流向和分布发生较大变化,导致原有馈线保护出现灵敏度降低、拒动、误动等问题,这给配电系统的继电保护提出了新的挑战。因此开展面向智能配电网的继电保护问题研究,在分析智能配电网对继电保护功能要求的基础上,研究相应的保护原理,提出相应的保护算法是十分必要的,对于智能配电网的发展有着重要的意义。分布式电源接入配电系统后,使传统的单电源辐射网络变成了一个多源网络。正常运行时,网络中的潮流分布及系统故障时短路电流的大小、流向和分布,均会发生变化。传统配电系统中保护设备之间建立起来的配合关系被打破,配电网中的自动重合闸的动作行为以及相应的包含DG的智能配电网的孤岛检测方法都将会受到较大的影响。尽管目前也提出了一些针对DG并网运行的自适应重合闸和孤岛检测方案,但是很多方案不够完善,具有一定的局限性,不适用于高渗透率的DG并网的智能配电网的保护要求。本文在总结和借鉴前人研究工作的基础上,面向智能配电网,提出了一种“主从式”变电站级纵联保护方案。该方案以包含DG在内的变电站及所有馈出线为保护区域,在变电站中设置一个站级保护主机,在具有切断短路电流能力的开关处均安装保护从机,从机借助光纤通信通道与主机实现快速可靠的信息交互。在配网系统发生故障时,保护从机基于本地电气量信息计算安装点处的故障方向,保护主机依靠通信系统完成对故障方向信息的收集,并通过故障检测与隔离算法对所收集的信息进行运算处理,判断出故障区段和需要跳开的开关信息,向对应的保护从机下发跳闸指令,最终完成故障的隔离。在智能配电网中,由于大量分布式电源(DG)或微网(MG)的接入,对配电网中的自动重合闸提出了新的挑战。智能配电网发生故障后,为尽快使瞬时性故障电弧消失,提高自动重合闸成功率,减小重合于故障对负荷的影响,应将故障区域内所有的主干线开关、DG或MG的并网开关、负荷分支开关跳开,然后根据预定的自动重合闸策略对跳开的开关进行顺序重合。本文提出的适用于智能配电网自动重合闸的开关分类方法,故障发生后由继电保护系统完成故障的检测和隔离,由位于各开关处的智能终端采集开关位置状态信息,上传至位于变电站监控室内的控制主机,形成开关跳闸信息向量。控制主机根据当前的网络拓扑结构,生成开关类型及关联矩阵,对配电系统中的各个开关进行了标记,通过对矩阵进行计算,完成对待重合开关的自动分类,并将分类结果和重合策略下发至智能终端,以实现预定的自动重合闸策略。配电网节点众多,各种DG投退频繁,导致智能配电网的运行方式灵活多变,尤其当电网中的某些开关断开时,会将电网分为若干性质各异、相互独立的子网,如果子网中的负荷由DG或微网供电,那么该子网就以孤岛的方式运行。孤岛的出现一方面对智能配电网的调度、自动化系统、继电保护系统和自动重合闸等带来较大影响,另一方面孤岛自身运行的安全性和稳定性也存在诸多问题。本文提出了基于可达性矩阵的智能配电网分区及孤岛辨识方法,将配电网整体作为研究对象,结合网络拓扑结构并利用网络中的开关位置状态信息,引入可达性矩阵,对电网进行分区,进而对孤岛进行辨识,判断出孤岛的数量、每个孤岛涵盖的范围,为开展孤岛运行控制与保护研究奠定基础。更多还原

【Abstract】 Distribution generation (DG) technology has been rapidly developed in recent years, in order to improve their security and reliability; distributed generators are normally integrated into power grids. The direction and distribution of the short circuit current in distribution power system has changed a lot due to the introduction of DG, as a result, the existing feeder protection there may be reduced sensitivity, tripping failure, malfunction, and so on, which gives distribution network relay protection many problems. Therefore, it is necessary to carry out related research on protection principle and put forward a protection algorithm, which are of great significance for the smart distribution network in the development and promotion.When distributed generations integrate into the distribution power system, the traditional single power network changes into a multi-source network. The direction and distribution of the short circuit current in distribution power system of normal operation has changed a lot. The cooperation relationship in traditional distribution protection equipments have been broken, the automatic reclosing in distribution network and the island detection method of smart distribution network will be affected. Although some automation reclosing and island detection methods for distribution power system have been put forward, but they can only improve certain aspects with limitations, and can not satisfy the protection requirements of smart distribution network containing DG.On the basis of previous research and longitudinal comparison principle, a new protection scheme which is a kind of substation area longitudinal protection with master-slave structure is presented for smart distribution grid, with the objective to protect the whole distribution substation and all of its outgoing feeders. Every switch in the distribution power system that can cut off short-circuit current is equipped with slave protection device. A host computer of system is set in the substation, which can achieve the interaction of information with slave device by the optical fiber communication network quickly and reliably. When the distribution power system is failure, the fault direction can be obtained from the slave device by calculating local electrical information, which is collected through the communication system and used by fault detection and isolation algorithm. By data operation processing, the host computer can find out the fault section and the breakers needed to be opened, and then send the trap instruction to the slave device so that the fault can be isolated finally.Due to a large number of distributed generations (DG) or micro-grid (MG) integrating into smart distribution network, the automatic reclosing in distribution network meets new challenges. When faults occur in smart distribution network, in order to make the instantaneous fault arc disappear as soon as possible and improve the success rate of automatic reclosing, the main switches, DG branch switches or MG switches and load switches of the fault region should be tripped, then according to the strategy reclose tripped switches sequentially. In this paper a method of circuit breaker classification for smart distribution network is proposed, after fault occurs relay protection system accomplish fault detection and isolation. According to the current network topology the host computer forms the types of circuit switches and corresponding incidence matrix which marks each switch in distribution network, finally complete automatic classification of tripped switches with the calculation of the matrix and transmit the classification results and reclosing strategy to smart terminals in order to realize the automation reclosing strategy.The node types in distribution network are different, all kinds of DG switch and trip frequently, results that smart distribution network operation is flexible, especially when some switches are tripped, the grid will be divided into different and independent subnets, if the loads in subnet power are supplied by DG or MG, the subnet will run in the form of an island. On one hand the island brings great influence on grid dispatching, automation system, relay protection and automation reclosing in smart distribution system, on the other hand, many problems for security and stability of the island exist. In this paper, a network partition and island identification method based on reachability matrix has been put forward, using the switches position information based on the network topology and reachability matrix, so each regional property can be quickly judged, whether the island exists and the number and range of islands. The research in this paper will lay the foundation for island operation control and protection.更多还原