Power conversion and control with zero AC current harmonics by means of a time-variable transformer

A new unified approach to the synthesis of bidirectional (AC ¿ DC) power conversion and control is presented, in which, in contrast to conventional methods, zero current harmonics are created at the AC source. The desired conversion is achieved by coupling a load that includes an electromotive force to an AC source by means of a time-variable transformer (TVT). The transfer ratio of the TVT is controlled such that the equivalent load is viewed by the AC source as a linear impedance; consequently, the current waveform is not distorted. It is also possible to operate this system in a capacitive mode in order to improve the power factor, even if the load does not include capacitance.