Minimum Torque Ripple Control for Brushless Doubly-Fed Induction Generator-DC System Under Power Winding Open-Phase Fault

In order to cope with the severe torque ripple caused by the open-phase fault of the power winding (PW) in the brushless doubly-fed induction generator-dc (BDFIG-DC) system, a novel minimum torque ripple control method is proposed in this article. The proposed method does not rely on additional external hardware devices and can minimize the torque ripple in the faulty system, thereby reducing damage to the machine bearings. Firstly, this article analyzes the harmonic components of the torque caused by PW open-phase fault in details, and derives the simplified torque expression. Secondly, by regulating the 3rd and 5th harmonic currents of PW, a minimum torque ripple control method is proposed. To obtain the real-time reference values of PW 3rd and 5th harmonic currents, the Newton's gradient descent method is adopted. Finally, the effectiveness of the proposed method is proven by comprehensive experimental results on a 5-kVA BDFIG-DC system platform.