Synchronous PWM Modulation to Eliminate Circulating Power in Bidirectional Dual-Active-Bridge Converter

To solve the problem of circulating power of dual active bridge (DAB) DC-DC converter over a wide voltage conversion ratio, this paper proposes a novel synchronous PWM (S-PWM) modulation. Existence of circulating power increases current stress of devices and decreases efficiency, especially under light load conditions. Several modulation methods have been proposed to overcome the problem. They can reduce or eliminate either input or output side circulating power. In contrast, S-PWM not only eliminates both sides circulating power and reduces current stress, but also achieves zero-current-switching (ZCS) turn-on for all switches and ZCS turn-off for most across the full power range. No auxiliary or snubber circuits are increased. In addition, the control can be simplified so the transmitted power is related to only one variable. The S-PWM has four cases under different gain and power conditions. The detailed operation principle and modes of DAB under S-PWM are analyzed in the paper. In addition, four modulations in literature are discussed, and corresponding comparative analyses with S-PWM are given. Finally, a laboratory prototype is built to verify advantages and effectiveness of the proposed modulation.