Abstract

Diode-rectifier units based HVDC (DRU-HVDC) transmission systems, which consist of multiple distributed offshore DRUs and an onshore modular multilevel converter (MMC), are promising candidates for delivering offshore wind energy to shores in an efficient and cost-effective way. In case of short-circuit faults in interconnected onshore ac grids, a voltage sag occurs, and it leads to a mismatch between the power delivered from the offshore wind farm and the instantaneous power capacity of the onshore MMC. However, the MMC is required to stay connected riding through the voltage sag and support reactive currents into the faulty ac grid in order to restore the voltage rapidly. In this paper, a communication-free low voltage ride-through (LVRT) strategy is proposed for DRU-HVDC systems for offshore wind farms. With the proposed strategy, the onshore MMC can support reactive currents in accordance with the grid code and track the pre-fault active power as far as possible during the LVRT within the current limit of the MMC. Thereby, the DRU-HVDC system can contribute to not only the voltage restoration but also the rotor angle stability of the onshore ac grid. The validity of the proposed strategy is verified by simulations of a ±200 kV, 400-MW DRU-HVDC based offshore wind farm.

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.