“pq theory” control applied to wind turbine trapezoidal PMSG under symmetrical fault

The permanent magnet synchronous generators (PMSG) used in wind turbines usually are machines with trapezoidal electromotive force (EMF) waveforms. The control techniques based on Park´s transformation, decomposing the voltages and currents into d and q axes, are not fully satisfactory when applied to such machines. For this reason, this paper proposes to realize the control of a permanent magnet generator with nonsinusoidal EMF using the “pq” or “instantaneous active and reactive power” theory. The objective is to reduce fluctuations of the generator´s torque and power, and this is done by comparison between the dq and the pq control. On the other hand, the grid-side converter control is still done using the dq technique. The low voltage ride through (LVRT) requirements is considered in the design of the generator control on the case of symmetrical faults. A control technique is used in which the responsibility of maintaining the DC link voltage constant belongs to the generator-side converter 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 a symmetrical voltage sag occurs at the network connection terminals.