Droop control strategy of a hybrid SEPIC-Cuk converter for bipolar DC microgrid-assisted charging infrastructures

This paper presents a virtual resistance-based droop control strategy for parallel hybrid SEPIC-Cuk bipolar DC-DC converters used as modular PV interfaces in bipolar DC microgrid-assisted charging infrastructures. Each module produces positive and negative bus voltages from a low-voltage DC source, while virtual resistance adjusts its current contribution without high-bandwidth communication. Steady-state relations are used to size the passive components, and a hierarchical droop controller comprising cascaded outer-voltage, inner-voltage, and inner-current loops is implemented. The strategy is validated using two parallel, downscaled converter modules at a total operating power of 400 W. For input voltages between 40 and 75 V and bipolar voltage references up to ± 100 V, the experiments show a predictable redistribution of the pole currents when the virtual resistances are varied, while the bipolar output voltages remain regulated during disturbances in the reference and source voltages. The results establish the feasibility of decentralized current sharing for this converter as a PV-to-bipolar bus interface. That said, application-rated efficiency, scalability, and coordination with MPPT remain topics for further work.