The three level neural point clamed isolation bidirectional DC-DC converter

Dual active bridge isolated bidirectional DC-DC converters-DAB-IBDCs, with the two-way power flow ability and high frequency isolation, can match the different level voltage resource easily, and are the critical unit to connect the different power such as battery, generator and loads etc. The three level neural point clamp-3L-NPC IBDC can fulfills high voltage converting with lower rated power devices, and can increase the power rate extent remarkably and improve the electromagnetic compatibility as the same. In this paper the control strategies of 3L-NPC IBDC were invested in detail and the operation modes were divided two types according to relationship between the duty cycle of the inner bridge and the phase shift ratio of the two bridges. The current, output voltage and transfer power characteristics are analyzed and analytical expression is given according the three sub-modes under model respectively. The current of the neural point must be kept balance to ensure the two clamp capacitors have the approximately equal voltage in one period in the both operation modes. The results show that the 3L-NPC IBDC is feasible and have a good prospect in the high power converters.