A multifunction series inductive AC-link universal power converter with reduced-switch count

This paper proposes a new family of series inductive ac-link universal power converter with a lower number of switches compared to other series inductive ac-link universal converters. The number of switches in the proposed three-phase ac-ac configuration is reduced to 18; whereas, the original series inductive ac-link converter requires 24 switches. In this converter, the power is transferred from input to output entirely or partially through a small link inductor. A small capacitor that is placed in parallel with this inductor allows all the switches to benefit from zero-voltage switching (ZVS), which results in significant reduction of switching losses, stresses over the active switches, and electromagnetic interference (EMI). The converter structure enables an input voltage to be stepped up or down, and provides unidirectional power flow. This converter, in which the input and output can be dc, single-phase ac, or multi-phase ac, is capable of functioning in buck, boost, and buck-boost modes of operation. A combination of these operation modes is also feasible. Operating the converter in buck or boost functions leads to substantially decreased inductor link peak current, stress of the switches, and total power-loss compared to other inductive-link universal power converters. Galvanic isolation in the proposed converter can be provided by means of a compact lightweight single-phase high-frequency (HF) transformer connected to the link instead of a low-frequency transformer, which is a prominent contributor to size and weight of a conventional isolated converter. In view of these advantages, the proposed configuration offers improved efficiency, increased power-density, high reliability, reduced total cost, and wide range of operation in terms of input voltage. In this paper, the detailed behavior of the proposed converter is investigated, and performance of the converter is evaluated at various operating points through simulation and experimental results.