Bidirectional modular multilevel DC-DC converter control and efficiency improvements through separate module control method

Abstract

This paper introduces a separate control method for modules of the bidirectional modular multilevel dc-dc power converter in order to improve overall converter efficiency. The proposed multilevel power converter topology is based on a Dual Active Bridge (DAB) converter as elementary electrical building block - module. Using efficiency curves it is determined how the modules should be separately controlled in order to decrease the total power converter losses, thus optimizing the total efficiency. The bidirectional modular multilevel dc-dc converter finds its application in energy extraction from Electro Active Polymer Wave Energy Converters (EAPWECs). It is shown that achieved power converter efficiency improvements have significant impact on the produced power in EAPWEC systems. Efficiencies of the power converter are modeled and verified with experimental measurements on the DAB module to support loss model.