Connection of an Offshore Wind Park to HVDC Converter Platform without Using Offshore AC Collector Platforms

Several large scale offshore wind farms are planned to be built far from the shores in the future. High Voltage Direct Current (HVDC) Light by ABB is an effective and reliable way to integrate this large scale wind power production to the grid. An expensive component of offshore wind park HVDC Light technology is offshore AC collector platform. The AC collector platform in the offshore wind farm HVDC link contributes significantly to the cost of the overall project. This paper investigates the comparison between two different AC topologies of an offshore wind farm connection to offshore HVDC converter platforms with and without offshore AC collector platforms. The technical feasibility of the omission of an AC collector platform from offshore wind farms connection to HVDC converter platform is investigated for the first time. In the first topology, the offshore wind farms are connected to an HVDC converter platform through offshore AC collector platforms. An offshore AC collector platform is used to collect energy from the wind farm and step up the voltages for transmission to offshore HVDC converter platform. The offshore AC collector platforms contribute significantly to the total cost and technical complexity of the HVDC connection. In the second topology, the offshore AC collector platform is removed from the circuit and the offshore wind farms are connected directly to offshore HVDC converter platform. The topological alteration of an offshore wind farm HVDC link gives rise to some technical challenges. The short circuit analysis and annual energy loss analysis is performed for these two topologies. The type of wind turbine generators, internal wind farm voltages and the distance between the wind farms and offshore HVDC converter platform are quite important factors that are investigated in this study. The short circuit analysis and loss analysis is performed for two types of wind turbine generators i.e. doubly fed induction generators (DFIG) and full conversion (FC) generators. Two internal wind farm voltage levels i.e. 33 kV and 66 kV, and three different distances i.e. 1 km, 5 km, and 10 km between the wind farms and offshore HVDC converter platform are investigated.