AC/DC rectifiers are vital elements in industry. Their uses include HVdc electric energy transmission, uninterruptible power supplies (UPS), electrochemical plants, railway systems, variable speed induction motors, telephone plants, etc. Regrettably, currents I.sub.A, I.sub.B and I.sub.C on the primary side of the transformer feeding the rectifier are distorted, which is penalized worldwide. Conventionally, this distortion is reduced through an apparatus connected either on the primary or secondary side of the transformer. The proposed apparatus, however, is connected on the DC side of the rectifier. It is demonstrated in a laboratory prototype that this apparatus achieves notably low distortion levels (ideally zero) in currents I.sub.A, I.sub.B and I.sub.C, at low cost and with a simple and robust control system, which is capable of handling rapid load variations. It can also be repaired on line without the need to disconnect the system.