Low-voltage direct-current(LVDC) distribution is an efficient way to accommodate high penetration of distributed energy generations, energy storage systems, and electronic loads in the distribution systems. This paper presents a topology of dual-active bridge(DAB) converter for bipolar LVDC distribution systems. By employing a dedicated winding connection in the ac-link transformer, the operation of two dc poles on the input side can be fully decoupled. Hence, the DAB can provide the full bipolar-operation capability without using additional active or passive components. In case one pole of the bipolar LVDC distribution is failed due to, e.g., wire disconnection, the dc-link input current of the faulty pole on the input side of the DAB converter can be transferred to the healthy pole immediately, and sustain the power supply to the output side. The validity of the topology and the control proposed in this work is verified by both simulations and experimental results.