Bidirectional isolated DC/DC converter using NPC inverters suitable for high power application

We have already proposed a new control method of the bidirectional isolated dc/dc converter with a current resonant circuit which can perform zero-current switching and the power factor improvement by means of pulse width control. This method is that pulse width of the inverter of higher d.c. voltage is narrowed to make equal fundamental a.c. voltage of both inverters. However, in this current resonant circuit, because the reactor becomes large and the resistance increases, there is a problem that improvement of efficiency is not so high. In this paper, to solve these problems, a new bidirectional isolated dc/dc converter using the NPC 3-level inverter will be proposed.