多端多电平柔性直流系统在海上风电场中的应用

针对交流输电技术和传统直流输电技术在海上风电场应用中的不足，以及保障岛上负荷正常供电的要求，提出了多个海上风电场及岛上负荷经多端多电平柔性直流系统并网的策略。建立了d-q旋转坐标系下的VSC-HVDC数学模型，并且设计了各换流站的控制策略。仿真结果表明，风电场经多端直流系统与陆上电网实现了互联，风电场发力不足时功率反转，即陆上电网向岛上负荷供电，保障了岛上负荷的正常供电。该并网方式灵活可靠，是海上风电场及岛上负荷与陆上电网的最优联接方式。

VSC-MTDC system based on MMC for offshore wind farms

In view of the drawbacks of application of AC power transmission technology and traditional HVDC transmission technology in the offshore wind farms and to meet the needs of ensuring the normal power supply on the island, a strategy that the flexible multi-HVDC transmission system based on MMC which can be used in the wind farm is adopted. The mathematical model of VSC-HVDC is established under the d-q rotating coordinate system, and the control methods for converter stations are designed. Simulation results show that the VSC-MTDC system is good at the connection between offshore wind farms and grid. When the power generated by wind farm is insufficient, the grids supply power to the load on the island. This way of grid connecting is flexible, and it is the best way for the connection between the wind farm on the island and land-based power grids.