Comparative analysis of modular multiport power electronic transformer topologies

Conventional line-frequency transformers are a key element in the current power transmission system. Although they are a relatively cheap and well established technology, they are not able to provide new functionalities demanded by the power system operator. Solid State Transformers (SSTs), also called Power Electronic Transformers (PETs) are power electronics-based arrangements able to provide, in addition to the basic functions of a conventional transformer, new functionalities like harmonics, reactive power and imbalance compensation, and power flow control. This paper addresses a comparative analysis of modular PET topologies, including the popular CHB-based approach and MMC-based topologies. Criteria for the evaluation will include aspects like the number of cells required, ratings of the power devices, number and type of the PET ports and design requirements for passive elements.