Bidirectional converter with high frequency isolation feasible to solid state transformer applications

Abstract

This paper presents a new three-port ac-dc converter topology based on the bidirectional version of the three-state switching cell (3SSC) and neutral point clamped (NPC) with Dual Active Bridge (DAB) fea- sible to interconnect an AC link, a DC link and photovoltaic panels. The three port converter operates as solid state transformer (SST). It the primary side switches voltage and current stresses are reduced due to NPC and 3SSC characteristics. Some operating ranges presented Zero Voltage Switching (ZVS). Modulation strategy and control are presented. For the drive control was implemented five control loops: PFC (Power Factor Correction); full voltage and balancing voltages acroos port 2 capacitors; magnetiza- tion current and voltage on port 3. A 33.33 kW converter with the peak value of the AC voltage is 9.35 kV and DC voltage at port 3 is 800 V with a DC bus voltage at port 2 of 22 kV has been simulated. A comparative loss studies with other converter topologies is also made. The proposed topology presented efficiency of 97.2%.