Quasi-resonant fast on-load two tap changing stabilizer: towards the AC soft switching

On load tap-changing AC stabilizers are widely used to procure slow acting voltage compensation to critical loads located in areas served by poor electrical lines. Typically, the response time is in the 100 ms order and the tap change happens normally at a frequency of one per minute or per hour. Nowadays, the continuous growth of current and voltage capabilities of the IGBT permits exploration of the feasibility of tap changers able to operate at a rate of several changes every half cycle, which would open these converters to new uses in the power quality world. This paper presents a detailed analysis of a new topology with switches working under soft AC commutation in order to reduce losses. A 100 VA prototype has been built and tested.