The steelmaking converter dusting fan system is the main equipment of the steelmaking production dusting system. In order to ensure the normal operation of the equipment and avoid safety accidents and economic losses caused by abnormal power supply, a dual power supply switching device for the converter fan power supply and distribution system is proposed. The voltage abnormality detection method, switching timing selection and triggering control strategy of the switching device are analyzed. A simulation example based on MATLAB/Simulink proves the correctness of the phase angle difference between the standby power supply and the residual induced electromotive force and the dynamic switching strategy.