Feasibility analysis of offshore wind power plants with DC collection grid

Offshore wind power plants (OWPPs) tend to be larger in size and distant from shore. It is widely accepted that for long distances HVDC links are preferred over HVAC transmission. Accordingly, one possible approach might be to consider not only a DC transmission system but also for the WPP collection grid. In this paper, a technical and economic comparison analysis of the conventional AC OWPP scheme and four proposed DC OWPPs topologies is addressed. Due to the conceptual novelty of DC technologies for OWPPs, uncertainty on electrical parameters and cost functions is relevant. A sensitivity analysis of the cost and efficiency of the components, OWPP rated power, export cable lengths and some economic data is carried out. For this study, a methodology is proposed and implemented in DIgSILENT Power Factory®. To compare conventional AC offshore collector grid and the various proposed DC configurations, an OWPP based on Horn's Rev wind farm is selected as base case. The analysis of the results shows that, in general terms, DC OWPPs present capital costs comparable with conventional AC OWPPs, as well as lower energy losses, concluding that DC collector grid could be of interest for future OWPP installations.