Efficiency improvement of bidirectional isolated DC/DC converter by current power-factor control

We have already proposed the new control method for the bidirectional isolated dc/dc converter. This method is that the output terminals of two single phase bridge inverter A and B are connected through an isolated transformer, and the pulse width of the inverter of higher d.c. voltage is narrowed to make equal the fundamental a.c. voltage of both inverters. For example, to make the a.c. output voltage of both inverters same, the pulse width of the inverter A is 180 degrees and the pulse width of inverter B is narrowed to 110 degrees. In this paper, the control method which enables the efficiency improvement of dc/dc converter by a current power-factor control will be proposed. In this control system, the phase difference control and the pulse width control are used. The phase of the sine wave current is brought to be in phase with the output a.c. voltage of the low d.c. voltage inverter, and as the result the zero-current switching can be realized.