Control of a wind turbine trapezoidal EMF PMSG under network asymmetrical faults

The permanent magnet synchronous generators (PMSG) used in wind turbines usually are machines with trapezoidal electromotive force (EMF) waveforms. The “instantaneous active and reactive power” theory is used to control the nonsinusoidal EMF permanent magnet generator. The objective is to reduce fluctuations of the generator´s torque and power, and this was demonstrated in a previous paper by comparison with the traditional dq control. The grid-side converter control uses the dq technique, since the network voltages are sinusoidal. The low voltage ride through (LVRT) requirements are considered in the design of both the generator side and grid side converter control in the case of asymmetrical faults. The generator-side converter is responsible for maintaining constant the DC link voltage and not to the network side converter as usual. Simulations using Matlab/Simulink show the effectiveness of the techniques proposed here in two cases: one where the wind turbine experiences a step increase in the wind speed and the other when asymmetrical voltage sag occur at the network connection terminals.