A New Control Algorithm Method Based on DPC to Improve Power Quality of DFIG in Unbalance Grid Voltage Conditions

Abstract

Conventional direct power control methods in unbalanced grid voltage conditions have undesirable effects on the performance and power quality of wind power plants based on DFIG. In this paper, a control algorithm based on direct power control method for DFIG is presented on unbalanced grid voltage conditions with the aim of reducing the output power oscillations and current THD of back-to-back converters. For this purpose, the oscillatory component of DC link power in an unbalanced condition at the grid voltage is identified from its fixed value and is added as the compensator to the input power reference value to the hysteresis controller as part of the grid side converter controller. In addition to reducing the power oscillations of GSC and its current THD, the proposed method decreases the current THD from DFIG and does not impose any additional oscillation in different parts of DFIG. The proposed control algorithm is simply implemented on conventional direct power control methods in unbalanced grid voltage conditions to improve its performance. Also, the results show that using the proposed method, in addition to controlling the output power of the DFIG and back-to-back converter, the output power oscillations and THD current of the back-to-back converters can be reduced simultaneously and the output current has become more like a sinusoidal form.