电压源型直流电网协调控制策略与直流故障特性研究

发布时间：2018-03-07 19:20

本文选题：电压源型直流电网　切入点：直流电网控制策略　出处：《华中科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：世界各国已经开始了能源结构的调整,可再生能源相对于传统能源所具备的优势使其得到快速发展。可再生能源发电技术的研究和大规模应用给电力系统带来了新的挑战和机遇,如何应对大规模可再生能源接入电力系统后远距离传输以及及时消纳等问题,成为学界热烈探讨的议题。相比于交流输电技术,直流输电技术更适合于非同步交流系统的互联、大容量可再生能源远距离输电等应用场合。从直流输电技术的发展历程来看,电压源型直流电网技术将会是直流输电技术在未来的发展方向。本文选取了电压源型直流电网协调控制策略和直流故障特性两个切入点,采用PSCAD/EMTDC这一仿真软件对这两部分内容进行研究,完成的研究工作及取得主要研究成果包括:介绍了直流电网建模中使用的两种电压源型换流器,研究了能够模拟稳态特性和故障特性的两电平电压源型换流器和模块化多电平换流器快速模型;比较研究了环形、辐射型、网状和混合式等不同拓扑直流电网的灵活性和经济性,研究表明,各类拓扑直流电网均具备其适用的应用场景。基于采用混合式拓扑的五端直流电网,研究了主从控制、主从备用控制、直流电压偏差控制和直流电压下垂控制等直流电网控制策略及其特性;在此基础上提出了一种主从-下垂协调控制策略,五端直流电网算例仿真研究表明,采用主从-下垂协调控制策略,在输入功率波动、换流站功率反向等情况下,能够精确跟踪电压和功率指令值,在主换流站退出运行的工况下能够快速平稳地转换至新的控制模式。分别建立了环形、辐射型和网状等三种典型拓扑直流电网,仿真研究了不同换流站出口处直流极间短路故障时直流电网短路电流特性。结果表明,直流电网中短路电流上升速度极快、峰值极大,最大短路电流的分布和峰值大小与直流电网拓扑、故障点位置和线路参数相关。建立了混合式高压直流断路器详细与简化仿真模型,针对连接交流电压源、交流负荷、永磁式直驱风力发电机或双馈式感应风力发电机的单个直流节点极间短路故障,仿真研究了该类型断路器开断故障电流的暂态过程,验证了其开断能力。
[Abstract]:Countries around the world have begun to adjust their energy structure. The rapid development of renewable energy is due to its advantages over traditional energy. The research and large-scale application of renewable energy power generation technology bring new challenges and opportunities to the power system. How to deal with the problems of long-distance transmission and timely absorption after large-scale renewable energy access to power systems has become a hot topic in academic circles. Compared with AC transmission technology, DC transmission technology is more suitable for the interconnection of asynchronous AC systems. Large capacity renewable energy long-distance transmission and other applications. From the development of DC transmission technology, Voltage source DC network technology will be the future development direction of HVDC transmission technology. In this paper, the coordinated control strategy and DC fault characteristics of voltage source DC power network are selected. The PSCAD/EMTDC simulation software is used to study these two parts. The research work and the main research results are as follows: two voltage source converters used in DC network modeling are introduced. The fast models of two-level voltage source converter and modularized multilevel converter which can simulate steady and fault characteristics are studied. The flexibility and economy of different topology DC networks, such as mesh network and hybrid DC network, are studied. It is shown that all kinds of topological DC networks have their applicable application scenarios. Based on the five-terminal DC network with hybrid topology, the master-slave control is studied. The main slave backup control, DC voltage deviation control, DC voltage droop control and other DC voltage droop control strategies and their characteristics are proposed, and a master-slave droop coordination control strategy is proposed. By adopting master-slave droop coordinated control strategy, the voltage and power instruction values can be accurately tracked in the case of input power fluctuation and converter station power reverse, etc. When the main converter station is out of operation, it can quickly and smoothly switch to the new control mode. Three typical topology direct current networks, ring, radiation and mesh, are established respectively. The characteristics of short-circuit current in DC network with short-circuit fault between DC poles at the outlet of different converter stations are studied by simulation. The results show that the short-circuit current in DC network is rising very fast and the peak value is very high. The distribution and peak value of maximum short-circuit current are related to DC network topology, fault location and line parameters. A detailed and simplified simulation model for hybrid HVDC circuit breakers is established to connect AC voltage source and AC load. The short-circuit fault between the poles of a single DC node of a permanent magnet direct-drive wind generator or a doubly-fed induction wind generator is studied. The transient process of the on-off fault current of this type of circuit breaker is simulated and its breaking capacity is verified.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM721.1

【参考文献】