Management of power excess in wind turbine system

Variable speed wind turbine generators provide the opportunity to capture more power than fixed speed turbines. However also the limitation of the produced power is an important issue. The paper is focused on the management of the power in excess in a variable-speed wind turbine equipped with a PMSG (Permanent Magnet Synchronous Generator) connected to the grid through a back-to-back converter. It is investigated the role of the braking chopper to dissipate the power in excess that can not be injected in the grid and the blade pitch control to limit the aerodynamic power in above-rated wind speeds in order to keep the turbine within its design limits. The interaction between the blade pitch control and the braking chopper is discussed. Finally, some simulation results in the case of a ramping wind speed and under real wind conditions are reported.