Control of a trapezoidal EMF PMSG under asymmetrical faults

A new control of a grid connected permanent magnet synchronous generator (PMSG) for wind turbines based on the Instantaneous Power Theory (pq Theory) is proposed. Given the PMSG trapezoidal electromotive force (EMF), the proposed pq control is advantageous over those based on the Park transformation, because it reduces the electromagnetic torque ripple and eliminates the calculation of sinusoidal functions. It is simpler and efficient and well adapted to medium power wind turbines. Back-to-back voltage source converters with space vector PWM modulation connect this generator to the grid. A trapezoidal EMF reference curve is generated as a function of the measured rotor position. The DC link voltage is controlled at the generator side, ensuring its control even in the presence of asymmetrical voltage sag at the grid connection. A wind turbine maximum turbine power point (MTPP) following strategy is also implemented. The complete system has been modeled in Matlab/Simulink. A test bench was build with a 3 kW PMSG that included a wind turbine emulator to drive the PMSG. Simulated and experimental results are presented that validate the proposed control strategy.