柔性直流配电网保护技术研究

发布时间：2018-12-13 12:27

【摘要】：当前国内外学者对柔性直流配电网的研究刚开始起步,柔性直流配电网的应用仍受限于缺乏关键技术、运行经验以及相关标准。本文以应用于城市的柔性直流配电网为研究对象,采用理论分析与PSCAD/EMTDC仿真验证相结合的方法,系统的分析了柔性直流配电网的系统架构和控制策略,研究了系统的接地方式和故障特性,并提出了一种新的继电保护方案。本文首先分析了应用于柔性直流配电系统的关键设备如整流器、逆变器、直流变压器,直流断路器,以及分布式电源光伏发电和风力发电并网的模型。提出了一种柔性直流配电系统的启动控制策略,以避免启动过程中过流对电力电子器件造成损害。提出了一种保护系统与控制系统的协调策略,以确保故障被隔离后,非故障区域能够正常运行。其次,在研究了直流不平衡电压恢复的理论的基础上分析了联接变压器的接地方式对换流器交流侧不同位置单相接地故障和直流侧单极接地故障的影响。与以往分析方法不同,为了提高系统运行可靠性,在分析系统故障时,考虑了IGBT不闭锁的情况。并讨论了在实际应用中如何确保IGBT运行在不闭锁状态下。分析结果表明,接地方式对系统的故障过程和故障恢复过程有很大影响。分析方法和结论为柔性直流配网的接地方式选取、保护方案配置提供了参考。在此基础上确立了柔性直流配电系统的接地系统配置。第三,在特定的接地方式下,在不闭锁换流站的前提下研究了该系统中压直流侧发生极间短路和单极接地短路故障时的故障特性,并分析了故障对其他区域的影响以及故障点过渡电阻的大小可能对故障特性产生的影响。第四,提出了一种新的继电保护方案。针对会产生过流并危害电力电子装置的极间短路故障和小电阻接地故障,设计了通过比较相邻保护安装处测得的线路电流状态值来判别故障区间的主保护。针对系统可能出现的大电阻接地故障情况,设计了以电压不平衡量作为启动判据,通过比较任何相邻保护安装处测得的不平衡电流状态值来实现故障定位和故障隔离的后备保护。针对可能出现的保护拒动或通信装置失灵现象设计了第一级远后备保护和第二级远后备保护,各级保护通过时间上的配合来避免同时动作。最后,对本文所做的研究进行了总结。
[Abstract]:At present, the domestic and foreign scholars have just begun to study the flexible DC distribution network, the application of the flexible DC distribution network is still limited by the lack of key technology, operation experience and related standards. In this paper, the flexible DC distribution network applied in cities is taken as the research object, and the system architecture and control strategy of the flexible DC distribution network are systematically analyzed by combining theoretical analysis with PSCAD/EMTDC simulation. The grounding mode and fault characteristics of the system are studied, and a new relay protection scheme is proposed. In this paper, the models of the key equipment used in the flexible DC distribution system such as rectifier, inverter, DC transformer, DC circuit breaker, distributed power generation and wind power generation are analyzed. A startup control strategy for flexible DC distribution system is proposed to avoid overcurrent damage to power electronic devices during startup. A coordination strategy between the protection system and the control system is proposed to ensure the normal operation of the non-fault area after the fault is isolated. Secondly, based on the research of the theory of DC unbalanced voltage recovery, the influence of the grounding mode of the transformer on the single-phase grounding fault of AC side and single-pole grounding fault of DC side is analyzed. In order to improve the operational reliability of the system, the condition that IGBT is not locked is considered in the analysis of the system fault, which is different from the previous analysis methods. How to ensure that IGBT runs without locking in practical application is discussed. The analysis results show that the grounding mode has great influence on the fault process and fault recovery process of the system. The analysis methods and conclusions provide a reference for the selection of the grounding mode and the configuration of the protection scheme for the flexible DC distribution network. On this basis, the grounding system configuration of flexible DC distribution system is established. Thirdly, the fault characteristics of interpole short-circuit and single-pole earthing short-circuit in the voltage DC side of the system are studied under the special grounding mode and without locking the converter station. The influence of fault on other regions and the influence of the size of fault point transition resistance on the fault characteristics are analyzed. Fourth, a new relay protection scheme is proposed. In view of the inter-pole short circuit fault and the small resistance grounding fault which will cause over-current and harm to power electronic devices, the main protection in fault zone is determined by comparing the current state values of the line measured at the adjacent protection installation. The voltage unbalance is used as the starting criterion for the possible grounding fault of large resistance in the system. The back-up protection for fault location and fault isolation is realized by comparing the unbalanced current state values measured at any adjacent protection installation. The first stage remote backup protection and the second stage remote backup protection are designed in view of the possible failure of protection or communication device. All levels of protection avoid simultaneous action through the cooperation of time. Finally, the research done in this paper is summarized.
【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】：TM721.1

【参考文献】