Direct Power Magnitude Control of DFIG-DC System Without Orientation Control

This article presents a novel direct power magnitude control of doubly fed induction generator-DC system without orientation control. The stator frequency is directly given and the angle of synchronized d-q frame is generated by the integral of stator frequency. The relationship between the stator power and rotor current vector is revealed in this article. Based on this positive correlation, the output power is easily controlled by the d-axis rotor current, and the q-axis rotor current is controlled flexibly to achieve the smooth switching from no output power to rated power. In accordance with the small-signal model, the relationship between decoupling control and coupling control is presented, and the principle to select the reference of q-axis rotor current is verified. Furthermore, the improved direct resonant control for torque ripple and harmonic current mitigation can still be applied in this novel control method. Finally, the experiment results are presented to validate the proposed method.