This paper presents a direct frequency control for offshore wind farms (OWFs) connected to the diode-rectifier-based (DR-based) high voltage direct current (HVDC) link. The frequency control is guaranteed through reactive power balance at the DR station without a capacitor bank placed at the DR station; while AC-voltage magnitude is clamped by the DR, provided that the HVDC link voltage is imposed by the onshore inverter. The control system is implemented by a voltage source converter (VSC) connected to the DR station. The VSC is also used to compensate harmonic currents, leading to passive AC-filters being also removed from the DR station. The proposed control system provides comparative advantages in terms of DR station volume and OWF installation cost with other centralized controls where besides a VSC, a high-voltage large capacitor bank is needed to be placed at the DR station. A new average-value model (AVM) of the DR system is derived to test the proposed frequency control, while the stability of the system is evaluated through a small-signal analysis. The proposed control system performance and the accuracy of the proposed AVM are verified through a detailed switching model of the system using operation of a cascaded H-bridge VSC.

中文翻译：

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基于二极管整流器的 HVDC 连接的海上风电场频率控制

本文介绍了对连接到基于二极管整流器（基于 DR）的高压直流 (HVDC) 链路的海上风电场 (OWF) 的直接频率控制。变频站通过无功平衡保证频率控制，无需在变频站放置电容器组；而交流电压幅度由 DR 钳位，前提是 HVDC 链路电压由陆上逆变器施加。控制系统由连接到 DR 站的电压源转换器 (VSC) 实现。VSC 也用于补偿谐波电流，导致无源交流滤波器也从 DR 站中移除。建议的控制系统在 DR 站容量和 OWF 安装成本方面与其他集中控制相比具有比较优势，其中除了 VSC，DR 站需要放置一个高压大电容器组。推导出了 DR 系统的新平均值模型 (AVM) 来测试所提出的频率控制，同时通过小信号分析评估系统的稳定性。所提出的控制系统性能和所提出的 AVM 的准确性通过使用级联 H 桥 VSC 的操作的系统的详细切换模型进行验证。