具备黑启动和构网能力的远海风电经DRU-MMC送出方案

Remote Offshore Wind Power Transmission Scheme Based on Diode Rectifier Unit and Modular Multilevel Converter with Black-start and Grid-forming Capability

由于具有成本低、体积重量小和可靠性高等特点,送端采用二极管整流器(DRU)、受端采用模块化多电平换流器(MMC)的送出方案在远海风电送出领域备受关注。鉴于DRU不能构建交流电网且无法倒送有功功率,文中提出一种具备黑启动和构网能力的远海风电经DRU-MMC送出方案。所提方案在DRU-MMC送出技术的基础上增加了常规小容量电压源型辅助换流器、耗能单元和必要的快速开关,通过直流海缆复用和快速开关倒闸重构拓扑,分别构建黑启动电源低压回路和风电传输高压回路,实现黑启动和功率传输2种工况在线切换;提出辅助换流器在不同运行阶段的构网控制策略,解决海上交流电网构建、DRU无功补偿和谐波抑制等问题,消除DRU-MMC送出方案对风电场类型的限制。最后,通过经济性分析和算例仿真,验证了所提方案的优越性和有效性。

Due to the characteristics of low cost,small size and weight,and high reliability,the transmission scheme using the diode rectifier unit(DRU)at the sending end and the modular multilevel converter(MMC)at the receiving end has attracted much attention in the field of offshore wind power transmission.Since DRU cannot form an AC power grid and provide reverse active power,this paper proposes a remote offshore wind power transmission scheme based on DRU-MMC with black-start and gridforming capability.The proposed scheme adds conventional small-capacity voltage-source auxiliary converters,energy-dissipating units,and necessary fast switches on the basis of DRU-MMC transmission technology.With the multiplexing of DC marine cables and the topology reconstruction by the fast switch switching operations,the low-voltage circuit for the black-start power supply and the high-voltage circuit for wind power transmission are constructed respectively,and the online-switching between the black-start condition and the power transmission condition is realized.The grid-forming control strategies of the auxiliary converter in different operation stages are proposed to solve the formation of the offshore AC power grid,the reactive power compensation and harmonics suppression of the DRU.Moreover,the restriction of the DRU-MMC transmission scheme on the type of wind farm is eliminated by the proposed scheme.Finally,the superiority and the effectiveness of the proposed scheme are verified by means of economic analysis and case simulation.