适用于低频输配电系统的新型模块化多电平交交变流器关键技术研究

In the area of long distance transmission of offshore wind power and subsea power distribution system for the deep sea oil and gas resource exploitation, low frequency power transmission and distribution system has a broad application prospect, belonging to the forefront technology and in a vital demand. Different from the MMC based converter in the flexible HVDC technology, the research on the AC/AC converter, which is the key point of the Low frequency power transmission and distribution system, is far from mature. Aiming at the shortcomings of the existing converter, the research group proposes a modular multilevel converter based AC/AC converter labeled as Y-MMC. The Y-MMC can decouple the frequency components of single phase, have no circulating current path, simplify the complexity of control system and improve the whole efficiency and economic benefit of the converter.. Based on the AC/AC converter Y-MMC, this project aims to carry out systematic and thorough researches on: 1) the modeling and control strategy of the Y-MMC AC/AC converter; 2) the fault ride-through capability of the Y-MMC AC/AC converter; 3) the virtual synchronous generator characteristics of the Y-MMC AC/AC converter; 4) the stability and optimal operation of the Y-MMC AC/AC converter; 5) the electromagnetic transient simulation and physical experiment research of the Y-MMC AC/AC converter; .the researches can provide theory and application basis for the AC/AC converter applied to high-voltage and high-power conversion field, promote the process of the low frequency power transmission and distribution technology and make a contribution to the development of the renewable energy and construction of the strong smart grid.

低频输配电系统在海上风电远距离传输、深海油气资源开发的海底输配电系统等领域具有广阔的应用前景，属于具有国家重大需求并处于学科发展前沿的技术领域。作为低频输配电系统中的核心装置，交交变流器的主电路拓扑远未成熟，相关技术研究方兴未艾。针对现有变流器的不足，本项目组提出了基于MMC的直接交交变换装置Y-MMC。Y-MMC可实现单相输入输出频率解耦，不存在环流通道，在降低系统复杂性的同时，大幅提升变流器的工作效率与经济效益。立足于该拓扑，本项目将深入研究下述内容：1）Y-MMC的建模及控制策略；2）Y-MMC的故障穿越技术；3）Y-MMC的虚拟同步机技术；4）Y-MMC的稳定性及优化控制；5）Y-MMC的电磁暂态仿真及物理实验研究。本项目的基础性应用研究，为高电压大功率场景下的交交变流器技术提供理论与应用基础，推动低频输配电技术的研究进程，为国家新能源电力发展与坚强智能电网建设提供自主创新型技术。

随着低频输配电系统在海上风电系统等应用中受到越来越多的重视，基于新型换流器的海上风电系统稳定性研究与控制性能提升已经成为当前的一大热点。本项目以新型变流器拓扑—Y-MMC变流器的提出为基础，在验证了其具有的技术经济性能及市场竞争力和行业应用前景后，综合研究了采用Y-MMC变流器的海上分频风电系统的相关控制策略。项目从Y-MMC的工作原理及数学模型的建立入手，系统的提出了相应的Y-MMC变流器控制方案，并在此基础上，深入研究了Y-MMC的故障穿越、虚拟同步机技术、稳定性及控制优化、电磁暂态仿真与实验验证等关键性技术。此外，在完成项目既定计划的基础上，Y-MMC变流器的启动预充电控制策略也得到了研究。项目所提的控制及优化策略均已得到Matlab/Simulink的仿真验证，Y-MMC系统也已完成样机研制，相关实验验证正在进行。本项目将理论研究和物理实验研究成果应用于新型低频输配电领域，将对未来海上低频输配电技术的发展具有重要推进意义。