A new full pq control of a wind turbine trapezoidal EMF permanent magnet synchronous generator

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 vector PWM modulation connect this generator to the grid. Synchronization and control of the power flow are based on the pq Theory with proportional-resonant current regulators on the grid-side, and proportional-integral current regulators on the generator-side. A trapezoidal EMF reference curve is generated as a function of the measured rotor position. The DC link voltage is controlled on the generator-side, ensuring its control even in the presence of symmetrical voltage sag at the grid connection. A wind turbine Maximum Power Point Tracking (MPPT) strategy is also implemented. The complete system has been modeled in Matlab/Simulink. A test bench was constructed with a 3 kW PMSG. A wind turbine emulator was built to drive the PMSG emulating the characteristics of a wind turbine. Simulated and experimental results are presented that validate the proposed control strategy.