| Abstract |
A new isolated DC-DC converter is presented suited for high voltage applications. It is based on theseries connection of NPC inverter cells, using semiconductor devices with lower voltage blockingcapability than the total input voltage. The galvanic isolation is realized using multiple MFtransformers, each designed for a fraction of the global power. The output comprises multiple dioderectifiers connected in series. The circuit uses a capacitive voltage divider at its input, allowing anactive balancing of the intermediate levels according the principle of the current diverter. Thebalancing half bridges allow an N-1 mode of operation in case of a fault or disconnection of one of theseries connected cells.The used 3-Level NPC topology for the half bridges allows in addition the continuous variability ofthe total voltage transformation ratio. The operation principle is verified by simulation, completed by asmall scale experimental set-up. Three- and four-stage topologies are used in the study, but theprinciple can be extended to a high number of modules, making the topology suitable for very highvoltage levels, where structures with redundancy (N-1) can be designed. |
