Non-Isolated Bidirectional DC-DC Converters with Multi-Converter Functionality Employing Novel Start-up and Mode Transition Techniques

This work targets reducing the mode transition time drastically, for two of the bidirectional DC–DC converters (BDCs) employed in energy storage systems, simultaneously proposing a smooth start-up process. Two different mode transition techniques are introduced for topology A (proposed) and topology B, respectively, whose transition times are much smaller than the existing transition techniques. Topologies A and B are capable of performing all basic converter operations, i.e. buck, boost, inverting buck–boost and non-inverting buck–boost in bidirectional mode, which allows the operating voltage ranges of both V 1 and V 2 to be increased perceivably. Both topologies are compared based on mode transition methodology, stress on the converter switches, inductor size and rating. A start-up technique is also advocated for both topologies so that the start-up response could be smooth. Two 400 W BDCs are designed with voltage levels of 60 and 120 V and experimentally verified for efficient start-up, mode transition and steady-state operations. Both mode-transition techniques proposed here, take 2 μs for the current reversal on the battery side from +5 to −5 A.