多端柔性直流输电拓扑及控制策略的研究

发布时间：2018-06-05 14:58

本文选题：多端柔性直流输电 + 拓扑优化　；参考：《华北电力大学(北京)》2017年硕士论文

【摘要】：柔性直流输电拥有灵活的控制技术,其理论上可运用的范围十分广泛。然而由于兴起时间较短,其理论研究不充分,工程运用范围仍十分有限,在优化拓扑或改进控制系统,减少换流站损耗、发挥改善交流系统电能质量的作用、简化换流器结构从而提高经济效益等方面都有较大发展空间。本文采用分层控制的思路,从系统级,换流器级和阀级三个层面分别研究了多端柔性直流输电系统(Voltage Source Converter multi-terminal DC,VSC-MTDC)的拓扑及控制策略,对其进行了优化,改进和创新。主要研究内容包括:(1)研究多端柔性直流输电系统的系统级拓扑,分析串联结构不适合用于电压源换流器的原因,以及采用并联型结构的优点;分析保持直流输电系统稳定的要素,研究系统级控制策略,对直流电压斜率控制进行深入研究,提出基于直流电压控制的各个换流站功率的最优分配方法;研究系统级辅助控制策略,提出系统启停控制策略,降压运行控制策略。(2)在换流站级层面,通过对柔性直流输电换流站的数学建模,分析其间接电流控制和直接电流控制策略,研究换流站连接不同性质网络时的控制策略,提出采用电压源换流器对交流系统进行无功补偿和有源滤波的控制方式,并进行仿真验证。(3)在阀级层面,研究两电平及三电平VSC拓扑,根据两电平VSC方波控制原理,提出二极管箝位型三电平换流器实现七电平方波控制的方法,并仿真验证可行;分析目前多电平换流器存在的不足,提出一种能同时进行变压和逆变的多电平逆变器,为了进一步简化多电平逆变器的结构,提升逆变器的稳定性,设计出另一种非隔离型多电平逆变器,并搭建仿真模型验证可行。
[Abstract]:Flexible DC transmission has flexible control technology, which can be widely used in theory. However, due to its short rise time, insufficient theoretical research and limited engineering application, it can reduce converter station losses and improve the power quality of AC system by optimizing topology or improving control system. There is much room for development in simplifying the converter structure and improving economic efficiency. In this paper, the topology and control strategy of VSC-MTDC in multi-terminal flexible DC transmission system are studied from three levels: system level, converter level and valve level. The topology and control strategy of VSC-MTDC are optimized, improved and innovated. The main research contents include: (1) study the system level topology of multi-terminal flexible direct current transmission system, analyze the reason why series structure is not suitable for voltage source converter, and the advantages of parallel structure; The factors of maintaining the stability of HVDC transmission system are analyzed, the control strategy of system level is studied, the DC voltage slope control is deeply studied, and the optimal power distribution method of each converter station based on DC voltage control is put forward. The system level auxiliary control strategy is studied, and the system startup and stop control strategy and the step-down operation control strategy are put forward. At the converter station level, the indirect current control and direct current control strategy are analyzed through the mathematical modeling of the flexible direct current transmission converter station. In this paper, the control strategy of converter station connected with different networks is studied, and the control mode of reactive power compensation and active filter for AC system with voltage source converter is put forward, and the simulation is carried out to verify that the voltage source converter is at the valve level. The two-level and three-level VSC topologies are studied. According to the principle of two-level VSC square-wave control, a seven-level square-wave control method of diode clamped three-level converter is proposed, and the feasibility of simulation is verified, and the shortcomings of multilevel converter are analyzed. In order to simplify the structure of multilevel inverter and enhance the stability of inverter, another non-isolated multilevel inverter is designed. And build simulation model to verify the feasibility.
【学位授予单位】：华北电力大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM721.1

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