Challenges in All-DC Offshore Wind Power Plants

Abstract

As the size and distance from shore of new offshore wind power plants (OWPPs) increase, connection to shore using high-voltage (HV) direct-current (DC) technology becomes more cost-effective. Currently, every offshore wind power plant has a collection system based on medium-voltage alternating-current technology. Such systems rely on heavy and bulky low-frequency (i.e., 50 or 60 Hz) transformers: a drawback offshore, where equipment weight and space are restricted. Consequently, there is growing interest in medium-voltage direct-current collection systems, in which low-frequency transformers are replaced with DC/DC converters equipped with lighter and smaller medium-frequency transformers. However, the deployment of all-DC OWPPs still faces several challenges. Based on a very comprehensive and critical literature review, three of them are identified and discussed in this paper. The first challenge is the technological gap at component level. In this work, the DC/DC converter topologies most suitable for application to OWPPs are described and compared. The second challenge is the controllability of DC collection systems. Parallel, series and hybrid DC collection system layouts are presented and discussed. The third challenge is the compliance of all-DC OWPPs with current requirements for their connection to the onshore grids. The three challenges are discussed to highlight current research gaps and potential future directions.

Design and control of all-DC offshore wind power plant with MMC-based DC/DC high-power converters

“…This layout is suitable for large OWPPs, as it makes possible to reduce the conduction losses with a considerable voltage ratio between generation and transmission (e.g. 40) [19]. The collection system's nominal voltage is ±50 kV, and the corresponding cables are DC-HYJQ41-F model, with cross sectional area of 800 mm 2 and resistance of 26.4 mΩ/km at 70 • C [18].…”

Advancements on Grid Compliance in Wind Power: Component & Subsystem Testing, Software-/Hardware-in-the-Loop, and Digital Twins

“…T HE rapid growth of wind power, particularly largescale offshore wind power plants connected through long AC cables or HVDC to shore, is creating challenges for transmission system operators (TSOs) who must establish frameworks and rules for the connection of wind power plants (WPPs) through grid codes and modeling requirements [1], [2]. In addition, the industry is also realizing the need to establish additional regulations for deploying ancillary services from renewable sources (e.g.…”

A hybrid half‐bridge submodule‐based DC–DC modular multilevel converter with a single bidirectional high‐voltage valve

“…The DC–DC converter is the main element in the DC grids to interconnect two DC voltages with different levels with bidirectional power flow capability. The main challenge is to implement high‐voltage high‐power DC–DC converters to meet the requirements of the high‐voltage DC grids [2].…”