D02.9 - 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, offering benefits such as galvanic isolation between input and output, and the ability to combine different input/output voltage levels. However, a volt-second imbalance will increase current and potential transformer saturation. This can lead to overheating and semiconductor overload. This paper proposes a new method to identify and reduce the DC bias by measuring only the DC-link voltage at each switching event. Experimental results confirm that the DC bias of 0.5 A on the secondary side results in a 50 mV voltage ripple between both switching events. The DC bias can be eliminated by controlling the Dual Active Bridge with duty cycle control additional to the phase shift control.