A new Hybrid power electronics on-load tap changer for power transformer

Traditional power transformer on-load tap changer (OLTC) works with mechanical switches have issues of electrical contact and mechanical part wearing, as well as speed limit. Full power electronics OLTC (Full-PE-OLTC) have been proposed to improve its performance, but the high cost of semiconductor components have been imposing a bottle neck for its practical application. The concept of hybrid power electronics tap-changer (Hybrid-OLTC) have been proposed for power transformer with relatively lower cost. However, problems remain to be solved to avoid arcing when commutating current from mechanical switch to semiconductor. This paper presents a new Hybrid-OLTC design to enable arc-free commutation of current. Practical design requirements on current and voltage stress level are also discussed with solution provided. Experimental result with 2 tap switches setup is provided to verify the theoretical result, as well as to provide reference data for full system design.