Design, operation and control of novel electrical concepts for offshore wind power plants

Abstract

Offshore wind is an emerging energy sector with a huge potential to be tapped in the near future. Offshore Wind Power Plants (OWPPs) are becoming increasingly relevant in Europe and worldwide mainly because the wind speeds are potentially higher and smoother than their onshore counterpart, which leads to higher wind power generation. Moreover, OWPPs have less space limitations constraints, so that it allows the possibility of using larger wind turbines. Nowadays, environmental and social aspects are forcing OWPPs to be constructed further from shore, (which usually leads to deeper waters) and the trend is expected to continue in the coming years. Several studies have demonstrated that if the distance between an OWPP and its grid connection point at the Point of Common Coupling (PCC) exceeds a certain critical distance (approximately 55-70 km), HVDC transmission becomes a more interesting solution than HVAC, since reduce cable energy losses and decrease reactive power requirements. This trend towards larger OWPPs located further away from shore is posing some technical, economic and political challenges that must be overcome to be fully competitive in the longer term compared to other energy sources. Today, there is an important concern about reducing the current Levelised Cost Of Energy (LCOE) of offshore wind projects by improving system reliability and availability, reducing O&M costs and/or increasing energy generation. This thesis aims to propose novel electrical WPP concepts more cost-effective than the existing ones and to comprehensive analyse their technical and economic feasibility. Specific challenges related to the design, optimisation, modelling, operation and control of these new concepts will be addressed in the study. All the concepts presented throughout this thesis, are focused on the collector grid of an OWPP, which encompasses all the necessary equipment to collect the power generated by the wind turbines and to export it to the offshore transmission HVDC platform. The first novel WPP ...