Magnetic integration of discrete-coupled inductors in single-phase direct PWM AC-AC converters

Recently, novel direct pulse width modulated (PWM) ac-ac converters using coupled inductors with switching cell structure have been introduced as an alternative to the conventional ac- ac converter topology. The converters can effectively solve the commutation problem associated with the conventional direct PWM ac-ac converters. However, the two coupled inductors used in the topology make the converters less attractive for use in practical applications. This paper proposes magnetic integration of the discrete-coupled inductors in single-phase ac-ac converters. The dc offset fluxes generated by the common-mode currents are cancelled out perfectly when the windings on the common core are appropriately arranged, resulting in ac flux only. The proposed inductor shows significant improvements over discrete-coupled inductors, in that the proposed inductor does not have an air gap, it exhibits symmetrical winding currents, and it has smaller volume with large current handling capability. The proposed inductor can handle an unlimited amount of current due to the absence of core saturation caused by the current and is well suitable for high power ac-ac conversion applications. The performance evaluation and comparison of the experimental results show that the net volume of the coupled magnetic components can be reduced by more than 50% with the proposed integration scheme.