Improved Torque Ripple Suppression Strategy for Brushless Doubly Fed Induction Generator-DC System Considering Winding Harmonic Loss

In the brushless doubly fed induction generator dc (BDFIG-DC) system, the machine windings contain significant harmonic components due to the three-phase diode rectifier connected to the power winding (PW), resulting in torque ripple and harmonic loss. To overcome these drawbacks, this study first analyzes the mechanisms of torque ripple and harmonic loss in detail. A winding harmonic loss Lagrange function is then constructed under the constraints of torque ripple suppression to solve for the optimized PW harmonic current references. Finally, a torque ripple suppression strategy considering the winding harmonic loss is proposed. Compared with the traditional torque ripple suppression strategies, the proposed strategy not only suppresses torque ripple but also minimizes winding harmonic loss. Consequently, the machine operating stability and efficiency can be significantly improved. The proposed strategy has been successfully implemented on a 5-kW BDFIG-DC platform, and its effectiveness has been verified through experimental results.