Speed control for direct drive permanent magnet wind turbine

Burning of fossil fuels to generate electricity is one of the fundamental causes of global warming. Wind energy has substantial potential due to the availability of wind and due to its non-polluting nature. The upward demand for wind energy has enabled considerable improvement in wind turbine technology. Among the wind turbine technologies available, permanent magnet technology is becoming more attractive due to its improved performance. Besides, the decreasing cost of power electronics is making permanent magnet machines with a full-scale power converter more viable for the direct-drive wind generators. In this paper, a control strategy to minimize the effect of changes in wind velocity and prevent over-speeding is proposed for direct drive permanent magnet wind turbine. For the gearless turbine, a mechanical shaft with speed control is designed to control the vibration and fluctuation due to changes in wind velocity. The simulation is done using PSCAD/EMTDC environment and the results obtained show the ability of the proposed control system to mitigate the effect of changes in wind velocity.