A simplified auto-connected electronic transformer (SACET) approach upgrades standard 6-pulse rectifier equipment with 12-pulse characteristics to facilitate harmonic compliance

In this paper, a simplified auto-connected electronic transformer (SACET) is proposed to upgrade standard 6-pulse rectifier equipment with 12-pulse characteristics. The SACET is an auto-connected high frequency transformer powered by a static converter. The system is connected in a shunt manner between the 6-pulse rectifier equipment and the utility. It is shown that SACET suitably alters the characteristic of the 6-pulse rectifier equipment to 12-pulse and achieves cancellation of 5^th and 7^th harmonics. In addition, 11^th and 13 ^th harmonic magnitudes are also significantly reduced. In the event that the SACET faults, the rectifier system characteristics revert to a 6-pulse. The per-unit rating of the SACET is 0.34 and its size and weight are related inversely to the switching frequency. The cancellation of 5^th and 7^th harmonics with the proposed approach is achieved entirely through open loop. Analysis and simulation of the proposed system along with a design example and experimental results from a 480 V, 10 kVA prototype system are presented