The low frequency AC (LFAC) technology is found to be a competitive solution for offshore wind farm integration. This article proposed an LFAC system with a hybrid onshore back-to-back (BtB) converter, for which the diode-based rectifier unit (DRU) and modular multilevel converter (MMC) based inverter are adopted. Then, this article also proposed corresponding control strategies for offshore wind turbines, where the DC link voltage control is implemented on the machine side converter, and the AC voltage of the offshore grid is controlled by the grid side converter based on the fixed reference frame. The small signal analysis for the whole system was carried out based on the equivalent circuit, and the small-signal stability is proven by calculated eigenvalues. And the system responses to typical operating conditions are investigated by time-domain simulations in PSCAD. Thus, the feasibility of the proposed scheme is verified.

中文翻译：

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基于DRU的海上风电场集成低频交流输电方案

低频交流 (LFAC) 技术被认为是海上风电场集成的有竞争力的解决方案。本文提出了一种具有混合陆上背对背 (BtB) 转换器的 LFAC 系统，该系统采用基于二极管的整流器单元 (DRU) 和基于模块化多电平转换器 (MMC) 的逆变器。然后，本文还提出了相应的海上风电机组控制策略，其中直流母线电压控制在机侧变流器上实现，海上电网交流电压由网侧变流器基于固定参考系进行控制。基于等效电路对整个系统进行小信号分析，通过计算特征值证明小信号稳定性。系统对典型操作条件的响应通过 PSCAD 中的时域模拟进行研究。从而验证了所提出方案的可行性。