Impact of unbalance voltage dips on the behavior of voltage source inverters

This paper discusses the impact of balanced and unbalanced voltage dips on grid connected voltage source inverters, usually found in wind turbines. A Kalman filter synchronization method is used to provide an accurate and fast extraction of the voltage positive sequence under unbalanced voltage dips. Also, it minimize the transient effects due voltage-phase-jumps. In addition, two current controllers are compared e evaluated. Simulation results demonstrate that the conventional PI control has a poor performance during unbalanced faults and that the synchronization method play an important role to improve the VSI low voltage ride-through capability.