Performance behaviour of off-shore wind farms with permanent-magnet generators

During the last years, wind turbines using doubly-fed induction generators have remarkably spread all over the world. However, synchronous generators, connected to the grid through full-scale converters, can be exploited. In this way, generator frequency is decoupled from grid frequency, and can follow wind variations, ensuring flexibility. As regards excitation, permanent magnets on rotor can establish the magnetic field, demanding control issues to accessible quantities on stator windings. The presence of full-scale converters allows to decouple generator-side control from grid-side control. This strategy, based on managing variations of power and voltage at both sides of the connection, permits to reduce losses and stresses on the machine. As wind farm size is growing, several requirements are imposed by transmission system operators on voltage and power control from wind farms in different operating conditions. In this work, a control scheme is adopted for permanent-magnet synchronous generators, and its behaviour is evaluated on a real-sized off-shore wind farm. In particular, once connection system is properly projected, various studies are proposed to validate the stability of the dynamic model and to verify the compliance of the plant with connection technical rules.