A Three phase Transformerless Buck Boost AC/AC converter for Induction motor fed drive applications

This paper proposes a three phase transformerless AC/AC converter which can perform both buck and boost operations based on the voltage requirements. This AC/AC converter is mainly proposed for the three phase induction motor drives with the intention to reduce the high inrush current of the conventional motor used in industrial applications. The merits of the proposed AC/AC converter can be understood with the fact that the use of magnetic elements are eliminated and the voltage stress of the active switches can be reduced to half the supply voltage by carefully choosing the capacitor values. In addition, the voltage applied to the load increases/decreases gradually thereby preventing the high inrush current from affecting the load. The bidirectional operation of this converter is possible by taking a common reference point between the supply and the load side voltages. This particular feature points out an added advantage for this proposed converter. In this paper the performance of the proposed converter is analyzed by simulating the results for a 110/220 V, 1 KW induction motor.