Fast DC-Bias Current Control of Dual Active Bridge Converters With Feedforward Compensation

In bi-directional dual active bridge (DAB) converters, the current flowing through the transformer generates significant DC-bias currents when the load of the converter changes, leading to unavoidable magnetic saturation of the high-frequency transformer. In this brief, the cause of the DC-bias current is briefly explained, and then a method of fast recovery control for this current is presented. By adjusting the phase shift ratio and duty cycle of the secondary-side squared voltage simultaneously in a feedforward matter, the DC-bias current as well as the magnetic saturation of the transformer can be effectively suppressed during the transient process. Extensive experimental results as compared to the existing control methods validate the effectiveness of proposed feedforward method.