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

The dominant problems of stator frequency control for DFIG-DC system are the parameter dependence and dc sampling offset, which will cause power control inaccuracy and fundamental frequency pulsation. In this paper, an air gap flux orientation method is adopted to eliminate the dependence on inductance parameters. The stator frequency and orientation angle are obtained through the stator active power control loop instead of calculating them based on voltage or current model, which can eliminate the sampling offset problem. Through controlling the q-axis air gap flux to be zero, the air gap flux orientation can be achieved. Since the product of stator flux magnitude and stator frequency is constant, the stator frequency can be controlled by regulating the d-axis rotor current directly. In this way, the stator frequency and output power can both be controlled accurately which are validated by the simulation results and experimental results will be done in final paper.