说明：  This paper proposes an open switch faults detection and localization algorithm for shunt three phase active filter topology. It mainly details converter configuration and examines a simple and reliable optimised fault diagnosis method. The con verter topology is based on classical three-leg active power filter topology. A ne w fault diagnosis method is proposed, based on classical currents measurements. It includes combinatory logic to analyse and validate error signals. A Hysteresis Control is applied before and after fault detection, which avoids any controller reconfiguration. Simulation results obtained with Matlab/Simulink/Plecs tools prove the effectiveness of this method.