Composite Duty Modulation of Dual Active Bridge Converters to Minimize Output Voltage Ripples and Inductor RMS Currents

To reduce output voltage ripples and inductor rms currents, a composite duty modulation (CDM) scheme of dual active bridge (DAB) converters is proposed, which can overcome the limits of fundamental duty modulation under light load and multiorder reactive-current suppression strategy under heavy load. The output voltage ripple and inductor current of the DAB converter are represented by a generalized averaging model considering the second harmonic component. The proposed CDM scheme can be implemented easily by modulating the duty ratio of the ac voltage not requiring a complex modeling process, offline calculation, and additional current sensor. The improved CDM scheme has also been proposed to optimize CDM performance when the voltage conversion ratio approaches unity under light load. The output voltage ripple optimization, inductor rms current suppression, and efficiency improvement of the proposed method are validated by simulation and experimental comparisons with other modulation schemes under different voltage conversion ratios and load conditions.