Multi-level Bi-directional Buck / Boost Converter

This dissertation presents a novel multi-level bidirectional DC-DC converter topology and the relevant control strategy. After researching many kinds of existing bidirectional DC-DC converter and multi-level converter, and learning from their strong points to offset the weakness, this novel multi-level bidirectional DC-DC converter has many advantages as follows:(1)This converter makes use of the advantages of the multi-level technology so that low-voltage MOSFETs or IGBTs can be used in some relatively high-voltage fields.(2)Buck mode and boost mode can both be achieved in either direction of the converter. Few existing converters have this capability. Further more the ratio of the output voltage and the input voltage can vary in a considerable wide range.(3)This converter is made up of several basic units. Every basic unit is the same to the others, so it is very easy to extend the research achievement to four-level, five-level, and even high levels. Otherwise, the basic unit can be easily displaced if some faults occur.(4)This converter is based on a generalized multilevel converter topology with self voltage balancing, so it can easily achieve level balance automatically.To prove the feasibility of the presented multi-level bidirectional DC-DC converter topology and the relevant control strategy, some simulation research based on the simulation software PSIM is performed. And then, a prototype is made. The curves obtained by simulation and the waves of the prototype firmly prove all the research of this dissertation.