Reliability Evaluation Modeling of Multi-Port Power Electronic Transformer Based on Cascaded H-Bridge

Multi-port power electronic transformer (MP-PET) is a new AC-DC conversion equipment, which reliability would directly determine the power supply reliability of the AC-DC distribution network. Thus, considering historical operating conditions, this paper evaluates the reliability of MP-PETs based on cascaded H-bridge. Firstly, combined with the control strategy, the analytical methods to calculate the power loss of different ports in MP-PETs are proposed. Then, junction temperature fluctuations of different links of MP-PETs are analyzed based on the Foster thermal resistance model. On this basis, the reliability model of the MP-PET is established, in which the fatigue accumulations of components are fully considered. Finally, the numerical results show that the weak links of the cascaded H-bridge MP-PET are mainly the components of the inverter and cascaded links, which reliability could be improved by proper redundancy.