DRU‐HVDC for offshore wind power transmission: A review

• Published in: IET renewable power generation 2024-10, Vol.18 (13), p.2080-2101
• Main Authors: Yu, Lujie, Fu, Ziyu, Li, Rui, Zhu, Jiebei
• Format: Article
• Language: English
• Subjects: high voltage direct current power transmission; wind turbine technology and control
• ISSN: 1752-1416; 1752-1424
• DOI: 10.1049/rpg2.13045

The rapid development of offshore wind farms (OWFs) calls for economical and reliable power transmission technology. This review paper focuses on the diode‐rectifier‐unit based high voltage direct current (DRU‐HVDC) transmission systems. The main technical features of DRU‐HVDC are highlighted and the comparisons with MMC‐HVDC and LCC‐HVDC are conducted. Considering the uncontrollability of DRU and the necessity of offshore wind turbines (WTs) to establish offshore network, the existing decentralized and centralized control strategies are reviewed in detail. For the fully‐grid‐forming converter, the operation principle of the P–V and Q–f power control is explained from the OWF‐DRU level and the WT level, respectively. For the partial‐grid‐forming converter, why the voltage control loop can be eliminated is analysed. Focusing on the start‐up issue caused by the unidirectional‐power‐flow characteristic of DRU, several start‐up solutions are reviewed, including medium voltage alternative current (MVAC) umbilical cable, auxiliary MMC, energy storage for WTs, auxiliary low voltage DC cable. Then considering different fault locations, the fault characteristic and protection of the DRU‐HVDC system is presented, including the offshore AC faults, DRU faults, HVDC faults and onshore AC faults. Finally, the future research topics worth exploring for DRU‐HVDC system are identified. This review paper highlights the main technical features of diode‐rectifier‐unit based high voltage direct current (DRU‐HVDC) and reviews the existing decentralized and centralized control strategies. Focusing on the start‐up issue, several start‐up solutions are reviewed. Then considering different fault locations, the fault characteristic and protection of the DRU‐HVDC system is presented. Finally, the future research topics worth exploring for DRU‐HVDC system are identified.