An Active Balancer of Currents for Bipolar DC Power Grids

DC power grids (DCPGs) are gaining more significance, predominantly due to the natural DC operation of technologies such as renewables, energy storage systems, and electric vehicles. Particularly, thanks to power electronics, bipolar DCPGs are gaining more preponderance since they enable reducing power losses, increasing power density, and averting power quality problems of AC power grids. Also, by adding power electronics, it is possible to establish different voltage levels to be adapted to different DC loads. However, since it is difficult to ensure balanced operating power for all loads in a bipolar DCPG, current imbalances emerge. This paper proposes an active balancer of currents (ABC), which is used to ensure balanced source currents in bipolar DCPGs, along with the corresponding power control theory. The ABC has two two-wire power interfaces, both linked in shunt to the DCPG, and both can be controlled to operate in bidirectional buck or boost modes. The validation was performed considering distinct current imbalances from the load point of view, permitting the verification of the correct operation of the ABC for balancing the current in the power source.