An Improved Method of DC Bus Voltage Pulsation Suppression for Asymmetric Wind Power PMSG Systems With a Compensation Unit in Parallel

This paper proposes an improved method of simultaneously suppressing the second harmonic (2h) dc-bus voltage pulsation and torque ripple by a compensation unit in parallel with the dc bus in the wind power permanent magnet synchronous generator (PMSG) system with asymmetric impedance. Compared to the existing methods, the proposed method uses fewer power devices and requires a much lower compensation current. These results in a lower power rating, lower power switch and copper losses, and a smaller compensation inductor in the compensation unit. In addition, the corresponding compensation current control is much simpler to operate. Overall, it is an effective method of suppressing the 2h dc bus voltage, although a dc voltage source is required in the compensation unit. The compensation effectiveness has been experimentally verified on a prototype asymmetric PMSG with inherent asymmetry and deliberately introduced asymmetries.