With the increasing scale of new energy grid, active power distribution network dynamic voltage stability and dynamic power supply quality control and other issues become increasingly prominent, the interaction between the dynamic characteristics of the permanent magnet direct-drive permanent magnet synchronous generator and the power grid has important influence on the stability of the power system. More and more switching devices in the wind farm have brought new challenges to the control strategy of the fan. Based on the RT-LAB platform, this paper implements the real-time simulation of the sub-microsecond step of the permanent magnet direct drive fan by using FPGA real-time simulator, which provides a fast and effective verification method for the verification and optimization of direct drive fans. Finally, the simulation results demonstrate the effectiveness of the small step hardware in-loop simulation method. This work is supported by National Natural Science Foundation of China (No. 51477099).