Design and Control of Three Phase Active Front End Converter fed Isolated Voltage Balancer for Bipolar DC Microgrid

An efficient and reliable bipolar DC distribution system is gaining traction in a variety of DC microgrid applications due to the development of distributed energy systems and energy storage. This paper addresses voltage imbalances and power flow difficulties in a recently introduced Bipolar DC Microgrid (BDM). A novel control approach is introduced for an isolated full-bridge-type voltage balancing circuit fed by a three-phase active front-end converter. The subsequent section also includes design instructions. The inherent advantages of the proposed isolated voltage balancer using the Phase Shifted Full Bridge (PSFB) converter and the Buck-Boost Bipolar Balancer are the galvanic isolation and high voltage gain due to the transformer turns ratio, making it suitable for high voltage and high power applications. Moreover, soft switching is achieved by employing phase-shift control for the primary active bridge, thereby enhancing conversion efficiency. A dual loop PI control of the voltage balancing converter and a traditional dual loop $dq$ control of the active front-end converter are presented to reduce voltage imbalances in a bipolar DC microgrid. The imbalance in bipolar DC buses in microgrids occurs due to uneven loading, unequal integration of renewable sources, and distributed energy storage elements. Extensive simulation studies have been conducted to validate the proposal in various disturbance scenarios.