A Novel Power-Angle Control Method of DFIG-DC System Based on Regulating Air Gap Flux Vector

This article presents a novel power-angle control method of the doubly fed induction generator dc system based on regulating the air gap flux vector. The relationship between the angle of air gap electromotive force (EMF) vector and the stator output power is revealed in this article, which can be used for controlling the output power directly. Since the stator frequency is determined by the rotating speed of air gap flux vector and the output power is determined by the angle of air gap EMF vector, the stator frequency can be generated by the power control loop that can avoid the classical voltage model or current model and reduce the parameter dependence. The stator frequency can be regulated through the d-axis rotor current since the product of the stator frequency and the d-axis rotor current is constant. Furthermore, the improved direct resonant control for torque ripple and harmonic current mitigation can still be applied in this novel control method because air gap flux orientation is achieved through controlling the q-axis air gap flux to be zero. Finally, the experimental results are presented to validate the proposed control method.