Abstract：The main circuit faults of the four-quadrant rectifier and the corresponding influences were analyzed

and summarized，focusing on the analysis of the voltage and current parameter equations in the pre-charging

process of the intermediate DC link，and the estimation method of the converter input current and the intermediate

DC link voltage was proposed. The estimated parameters were compared with the actual detection results，and the

corresponding fault detection can be carried out by using the performance of different faults in the pre-charging

process. Through simulation and experiment，different faults were simulated and analyzed，and the results show that the fault detection method proposed is effective and feasible.

      Key words：four-quadrant rectifier；pre-charging；intermediate DC link；fault detection