Topology and Control of an Enhanced Dual-Active Bridge Converter With Inherent Bipolar Operation Capability for LVDC Distribution Systems

Low-voltage direct current (LVDC) distribution is an efficient way to accommodate high penetration of renewable energy sources, energy storage systems, and electronic loads in the distribution systems. This article presents an enhanced 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 full bipolar operation capability on the input side without additional power-semiconductor devices or magnetic components. The positive- and negative-pole dc currents on the input side could be independently controlled by the dedicated differential- and common-mode current controllers. Hence, in case one pole of the bipolar LVDC distribution is failed due to, e.g., damage of cable, 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 effectiveness of the topology and the current control scheme proposed in this work are verified through simulations and experiments on a fabricated 7.2 kW 600 V SiC converter prototype. In asymmetric operations, the proposed three-phase DAB (DAB3) converter presents efficiency boost up to 1.5% compared with the conventional system with a DAB3 converter and a voltage balancer attributed to the reduced stage of power conversion.