Technical and economical evaluation of distributed AC power collection for Off-shore Wind Power Plants

The paper outlines a technical and economical comparison of two power collection concepts for off-shore wind farms: an innovative distributed concept versus the commonly used centralized power collection. In contrast to centralized power collection on a single and large platform, integrated and compact switchgear and transformer modules enable the distribution of power collection across multiple strings of interconnected wind turbine generators. The increasing size of the new generation of wind turbines above 4 MW and the corresponding large tower structures allows distribution of such modules throughout the array grid. Distributed power collection reduces capital expenditure by eliminating the need for a single large off-shore platform and allows a step-wise development of the wind farm over time. The wind farm studied in the paper is assumed to have a final capacity of 624 MW with power collection at 72kV AC and export cables at 220kV AC. The paper also presents the electrical aspects of wind power plant grid connection as a result of load flow studies, including an assessment for reactive power compensation. Keywords-Offshore; 72 kV collection grid; offshore platform; compact switchgear; GIS