Abstract: In order to improve the utilization of the DC side voltage of the nine-switch converter and reduce the switching loss,a discontinuous space vector pulse width modulation（DSVPWM）is proposed. At the same time,the nine-switch converter is used in the direct-driven wind turbine with permanent-magnet synchronous generator（PMSG）on the grid side to form a parallel grid-side nineswitch converter（GS-NSC）. Based on the theoretical analysis of the parallel GS-NSC control strategy and fault ride-through scheme,a PMSG parallel GS-NSC simulation model is established,and a variety of power grid voltage fault conditions are designed for simulation research. The results show that the parallel GS-NSC can maintain the sine wave characteristics of the grid current under normal working conditions of the grid voltage. Under the condition of power network voltage plummeting,the parallel GS-NSC can inject reactive current into the grid to assist the recovery of the grid voltage,and reduce the power loss of the unloading circuit by increasing the grid-connected current amplitude and reduce the PMSG’s heat dissipation burden. Under the condition of voltage surge,the parallel GS-NSC can dynamically distribute the DC bus voltage to avoid the PMSG from exiting operation due to overvoltage on the DC side.