A novel fault-tolerant four-leg AC/AC converter capable of compensating unbalanced source/load

A novel reduced switch count AC/AC converter is proposed in this paper which can compensate for unbalanced characteristics of both the input AC source and the output three-phase load. The proposed converter satisfies all the expectations of an ideal robust converter such as unity input power factor, low THD sinusoidal input current and output voltage and fast dynamic response even under serious fault conditions which may occur in one/two phase(s) of the converter source/leg. Being capable of properly supplying the load even under two-phase grid-side fault, the backup batteries do not go into frequent charge/discharge cycling. This increases the battery life considerably. Based on frequency isolation, two modes of operation are defined and the proper control system is designed. The validity of performance of the proposed converter is tested and verified through simulation.