Coupled-Inductor-Based Buck-Type Converter With Autonomous Voltage Balancing for Bipolar DC Microgrid

To maintain the stability and balance of the output voltage of the bipolar system under unbalanced loads, this letter proposes a novel buck converter with bipolar outputs, where only one "switch circuit" is on the input side while two diode rectifiers and two LC filters are on the output side. Instead of two independent filter inductors, one coupled inductor is adopted. As a result, the bipolar output voltages can be balanced autonomously under any load conditions without extra components or voltage-balancing control loop. Meanwhile, the wide voltage regulation range and easy control of the traditional buck converter are reserved. The autonomous voltage-balancing mechanization and the coupling coefficient effect are analyzed. The proposed coupled inductor method can be applied to other buck-type converters, such as the phase-shifted full-bridge (PSFB) converter. Finally, an experimental prototype of the bipolar PSFB converter is built to verify the feasibility and advantage of the proposed converter.