中文摘要：

多端直流输电能够实现多电源供电、多落点受电,是一种灵活、快捷的输电方式,是海上大规模风电场的发展方向。本文详细分析了海上风电场多端直流网的拓扑结构,对各种拓扑结构的线路容量、直流断路器数量、线路利用率、是否需要海上平台等问题进行了研究。在对各种拓扑结构分析对比的基础上,推荐了一种风电场环形拓扑,该拓扑需要断路器数量少（等于风电场的个数）,增加了风电场与电网之间功率控制的柔性,是一种优化的拓扑结构,在输电线路故障时,通过断路器和隔离开关的控制,风电场仍可以向电网发电,提高了系统的灵活性和冗余性,并进行了算例验证。文中推荐的拓扑结构对大规模海上风电场多端直流网的运行控制有一定的指导意义。

英文摘要：

Multiterminal HVDC is a flexible transmission method which supports multi power supply and multi power consumption. It is the trend of large offshore wind farms. Topologies of multiterminal HVDC- VSC transmission for large offshore wind farms were investigated. Various topologies were analyzed according to a number of criteria,including lines rating,number of HVDC circuit breakers,lines utilization and necessity of an offshore platform. A recommended topological structure was given based on the comparison. Wind farms ring topology（ WFRT） is a optimal topology,which minimises the number of HVDC circuit breakers. The wind farm can still work by breakers and isolators in the event of a circuit fault.Flexibility and redundancy is improved,and case study is given in the situation. The recommended topology has some guiding significance in the running control of multiterminal DC networks.