Comparison of Voltage Balancers for DAB Converters in Bipolar Residential DC Microgrids

Bipolar dc microgrids have been increasingly adopted in different applications due to their versatility in scaling to higher power levels while maintaining the same safety requirements as lower voltage unipolar ones. On the other hand, power imbalance, commonly faced in bipolar systems, can lead to undesirable voltage deviations that may trigger protection devices, cause corrosion, and increase risks of electric shock. To address this issue, several voltage balancing solutions have been proposed, including self-balancing dc-dc converters, and others active balancers. Both approaches are different in terms of hardware implementation, efficiency, and complexity. In this paper, a two-switch buck/boost voltage balancer and a self-balanced current-fed dual active bridge (CF-DAB) converter are experimentally compared for applications in bipolar dc microgrids. Experimental results are presented using a 5-kW prototype. The results demonstrate that both solutions offer different opportunities for system optimization. However, the processed rms current analysis shows the self-balanced solution providing advantages in terms of efficiency, while the conventional buck/boost balancer offers a more cost-effective solution.