Low Voltage Ride-through Control Strategy of a Doubly Fed Induction Generator Wind Turbine With Series Grid-side Converter

Doubly fed induction generator(DFIG) is very sensitive to grid faults.Its low voltage ride-through(LVRT) technology attracts more and more attention in recent years.The reason for rotor over current was analyzed in this paper.On the basis of this and combined with the new configuration of a DFIG system with series grid-side converter(SGSC),a "zero voltage vector" improved control strategy during normal grid condition and an improved fault control strategy allowing DFIG to ride through the grid faults were proposed.By controlling the output voltage of SGSC to suppress the transient DC flux and negative sequence flux components in the stator flux and also by controlling the rotor-side converter(RSC) to further restrain the stator and rotor currents,a successful ride-through during grid faults was achieved.Simulation on a 2 MW DFIG system with SGSC under symmetrical and unsymmetrical grid faults was performed.The LVRT performance of the proposed control strategy was also compared with the traditional "crowbar protection" strategy and the improved excitation control strategy.Simulation results demonstrate that the proposed control strategy can make the DFIG system with SGSC achieve zero voltage ride-through.The DFIG system has good LVRT performance.