Definition of a Control Scheme for a Coordinated Management of Large Offshore Wind Farms Connected via Hvdc Links

This paper proposes the development of an appropriate control system for the real-time management of large offshore Doubly-Fed Induction Generator (DFIG) based wind farms, connected to the transmission network by Voltage Source Converter High Voltage Direct Current (VSC-HVDC) link. In this plant layout, variable frequency operation lets wind turbines to work on a wider range of wind speed values, limiting the generator slip and improving at the same time the energy production. The VSC-HVDC sending end converter and the DFIGs grid side and rotor side converters are modelled as ideal three-phase voltage generators: the values of some control variables are calculated by a two-step optimization procedure coded in MATLAB® programming language: a central optimizer, which maximizes the overall power production of the whole wind farm and a local optimizer, which gives the appropriate set-point signals for each wind turbine. The aforementioned configuration and the control solutions applied to each wind turbine have been modelled in Simulink® environment. Tests are carried out on a wind farm with 50 wind turbines.