DC-Bias Elimination in High-Frequency Dual Active Bridge DC/DC Converters through Single-Sided Measurements

This paper addresses the issue of DC bias in high-frequency Dual Active Bridges DC/DC converters. Dual Active Bridges are widely used in various applications because they offer benefits such as galvanic isolation between input and output, and the ability to combine different input/output voltage levels. However, an imbalance of the voltage across the magnetizing inductance causes an increase in transformer current and potential saturation. This can lead to overheating and semiconductor overload. This paper proposes a novel method for detecting and migrating DC bias through measurement of only the DC-link voltage during each switching event. Experimental results confirm that a DC bias of 0.5 A on the secondary side results in a 30 mV DC-link voltage ripple between both switching events on the primary side. To eliminate the DC bias, duty cycle control is applied in conjunction with phase shift control during operation of the Dual Active Bridge.