Abstract
A diode rectifier-modular multilevel converter AC/DC hub (DR-MMC Hub) is proposed to integrate offshore wind power to the onshore DC network and offshore production platforms (e.g., oil/gas and hydrogen production plants) with different DC voltage levels. The DR and MMCs are connected in parallel at the offshore AC collection network to integrate offshore wind power, and in series at the DC terminals of the offshore production platform and the onshore DC network. Compared with conventional parallel-connected DR-MMC HVDC systems, the proposed DR-MMC hub reduces the required MMC converter rating, leading to lower investment cost and power loss. System control of the DR-MMC AC/DC hub is designed based on the operation requirements of the offshore production platform, considering different control modes (power control or DC voltage control). System behaviors and requirements during AC and DC faults are investigated, and hybrid MMCs with half-bridge and full-bridge sub-modules (HBSMs and FBSMs) are used for safe operation during DC faults. Simulation results based on PSCAD/EMTDC validate the operation of the DR-MMC hub.
Highlights
The global energy transition from fossil fuels to renewable and sustainable alternatives is accelerating, with increased interest in developing offshore wind energy
To overcome the above challenges, a diode rectifier (DR)-modular multilevel converters (MMCs) AC/DC Hub (DR-MMC Hub) with the DR and MMCs connected in parallel at the AC side, and in series at the DC side, is proposed to transmit offshore wind power to an onshore DC network and an offshore production platform with different DC voltage levels
A DR-MMC AC/DC Hub comprised of series-connected DR and MMC for connecting offshore wind farms with onshore DC network and offshore production platform is proposed in this paper
Summary
The global energy transition from fossil fuels to renewable and sustainable alternatives is accelerating, with increased interest in developing offshore wind energy. A hybrid AC/DC hub composed of the LCC and MMC in series connection has been proposed for onshore wind-power integration and interconnection of two DC networks with different DC voltages [14], but this hub is not suitable for offshore applications due to the large footprint and heavyweight of the LCC, which needs a strong AC grid for commutation. To overcome the above challenges, a DR-MMC AC/DC Hub (DR-MMC Hub) with the DR and MMCs connected in parallel at the AC side, and in series at the DC side, is proposed to transmit offshore wind power to an onshore DC network and an offshore production platform with different DC voltage levels. Based on the operation requirement of the offshore production platform, comprehensive operating conditions of the proposed DR-MMC Hub are investigated, considering the different control modes (power control or DC voltage control).
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