A Modulation Strategy for Wide Voltage Output in DAB-Based DC-DC Modular Multilevel Converter for DEAP Wave Energy Conversion

This paper presents an investigation on modulation modes for dual active bridge modules stacked in a 10-kV input parallel output series converter for energy extraction in dielectric electroactive polymer (DEAP) wave energy converters. The converter requirements for energy harvesting with DEAPs are derived, and the operating areas and limitations of each modulation mode are compared. A hybrid modulation strategy consisting of several variable frequency modulation modes is proposed, which is capable of operating over a wide voltage and current range at high-efficiency levels as required by the DEAP harvesting cycles. Through loss calculations using an experimentally validated loss model and by including both material and converter losses in the harvesting cycle, it is shown that the hybrid modulation method increases the energy output of low-strain cycles by 25%.