Abstract
The main purpose of this thesis is focused on the study of an interface between a battery energy storage system and a paralleled DC microgrid with a view to develop to a novel bidirectional dc converter for regulating the DC microgrid. Basically, the major contributions of this thesis can be summarized as follows. First, a new bidirectional dc converter structure is proposed. This new topology can not only achieve electrical isolation and bidirectional power flow capability, but also can be embedded with a voltage multiplier module in high voltage side to obtain N times voltage step up/down, where N is a positive integer greater than is equal to two. Also, starting from N≧2, only one more active switch and one more capacitor are required for increasing/decreasing one more voltage level step up/down. Secondly, to demonstrate the way of increasing the power handling capability, two sets of the proposed bidirectional basic converter are interconnected together such that the high voltage sides are in series and the low voltage sides are in parallel. Meanwhile, the corresponding DC and AC models are derived for feedback controller design. Finally, a 1kW prototype with 400V high side voltage and 48V low side voltage have been constructed to verify the feasibility of the proposed converter. It can be seen that maximum efficiencies are 94.1% and 94.4% for step down and step up operation modes respectively.