Doubly fed induction generator (DFIG) control process is more complex in the calculations under voltage unbalance condition because of the power oscillations, and the conventional controllers cannot maintain the system in a stable and smooth condition. In this paper, a flexible method is presented to control the DFIG based on an improved extended power theory on the direct power control platform. The proposed method can simultaneously improve electromagnetic torque oscillations, reduce total harmonic distortion (THD) of stator currents and eliminate active or reactive power oscillations by controller of rotor side converter. The main control system relations based on an analytical process are presented. The improved extended power theory method has made the proposed control independent from decomposition of the positive and negative sequence components which provides ease of the calculation and better performance accuracy. Compared to the conventional extended theory, the proposed method is capable to reduce the torque oscillations, reduction of the stator current THD, and eliminating the powers oscillations of the DFIG. Also, In order to maintain the appropriate dynamic response, a switching table is presented according to the proposed method. The simulation results are clearly confirmed that the proposed method improves the DFIG performance in view of the oscillations under the voltage unbalance conditions.

双馈感应发电机(DFIG)控制过程在电压不平衡条件下由于功率振荡计算更加复杂，常规控制器无法保持系统稳定和平滑。在本文中，基于直接功率控制平台上的改进扩展功率理论，提出了一种灵活的控制双馈电机的方法。该方法可以同时改善电磁转矩振荡，降低定子电流的总谐波失真（THD），并通过转子侧变流器的控制器消除有功或无功功率振荡。介绍了基于分析过程的主要控制系统关系。改进的扩展幂理论方法使所提出的控制独立于正序和负序分量的分解，这提供了计算的简便性和更好的性能精度。与传统的扩展理论相比，所提出的方法能够减少转矩振荡，降低定子电流 THD，并消除 DFIG 的功率振荡。此外，为了保持适当的动态响应，根据所提出的方法提出了一个切换表。仿真结果清楚地证实，鉴于电压不平衡条件下的振荡，所提出的方法提高了双馈电机的性能。所提出的方法能够减少转矩振荡，降低定子电流 THD，并消除 DFIG 的功率振荡。此外，为了保持适当的动态响应，根据所提出的方法提出了一个切换表。仿真结果清楚地证实，鉴于电压不平衡条件下的振荡，所提出的方法提高了双馈电机的性能。所提出的方法能够减少转矩振荡，降低定子电流 THD，并消除 DFIG 的功率振荡。此外，为了保持适当的动态响应，根据所提出的方法提出了一个切换表。仿真结果清楚地证实，鉴于电压不平衡条件下的振荡，所提出的方法提高了双馈电机的性能。