Cost of energy assessment methodology for offshore AC and DC wind power plants

In offshore wind power plants, the losses occurring in the path from the wind turbine to the point of common coupling contribute significantly to the cost of energy. Therefore, a reduction of the losses along this path represents a desirable way to drive down the energy cost. For state-of-the-art AC systems, simply increasing the voltage level in the collection grid has the potential of improving its efficiency. However, since large offshore wind power plants tend towards being connected to shore through HVDC transmission lines, one might extend the DC nature of the high voltage transmission to the collection grid in the attempt of reducing the losses. Nevertheless, both solutions may increase the cost of the system and therefore, their potential benefits must be quantified in the proper way and as accurate as possible. This paper presents a tool to assess the performance of different wind power plant configurations in order to suggest the most appropriate solutions for offshore applications. The advantages of this tool are expressed in terms of configurability, fast computation and increased automation level. The assessment presented in this paper is intended to highlight the potential benefits of adopting DC technologies for offshore wind power developments and the proposed methodology is exemplified by a study case where a standard AC configuration is compared with alternative DC solutions.