In the case of grid voltages dips， the wind power plants are demanded to keep connected to the grid， and to help the network recover from the fault. This paper focuses on the low voltage ride through（LVRT） control of large-scale wind energy system based usinga multiphase direct drive permanent magnet synchrony generator（PMSG） and three-level converters. The paper analyzes the impact of generator side rectifiers and grid side converters cased by symmetrical or asymmetrical voltage dip. In order to fulfill the LVRT requirement， the energy accumulated in the converters has to be reduced. A control approach is developed， which is implemented by resetting current command and adjusting the speed of PMSG. Finally， a time-domain computer simulation is done for the proposed system. Simulation results confirm the feasibility and validity of the proposed method.