Dynamic Modeling and Improved Control of DFIG under Unbalanced and Distorted Grid Voltage Conditions

This paper presents an enhanced control strategy for the DFIG-based wind turbines under unbalanced and distorted grid voltage conditions. An integrated mathematical model of DFIG is set up, based on which four alternative control targets and their corresponding rotor current references are calculated and assigned. A novel current controller, consisting of a conventional PI regulator and a dual-frequency resonant compensator, tuned at twice and six times the grid frequency, is designed to regulate the fundamental and the fifth- and seventh-order harmonic components simultaneously. Simulation studies verify the effectiveness of the suggested control strategies in improving the fault ride through capability of a DFIG system under such adverse grid voltage conditions.