Direct grid connection of a slip-permanent magnet wind turbine generator

The slip-permanent magnet generator offers potential for direct-driven, direct-to-grid sub-100 kW wind turbine generators. This reduces complexity and cost, as well as maintenance requirements. A major challenge, however, is to synchronise the generator to the grid without the benefit of turbine torque control. This paper presents the simulation and testing of a synchronisation controller designed to achieve this goal. Simulations are used to determine acceptable conditions for synchronisation and to evaluate two speed control approaches, based on loading the generator with a resistor bank. A thyristor-based control strategy is shown to operate effectively, even under turbulent wind conditions. Experimental tests of the system show that the synchronisation mechanism works correctly - good agreement with simulation results is achieved.