Hierarchical control scheme for proportional power sharing and robust operation in multiple virtual synchronization-based DC/DC converters

Virtual synchronization control can be applied to DC/DC converter for enhanced inertia support by imitating the rotor dynamics of the synchronous generator (SG). However, efficient power sharing and robust operation ability cannot be guaranteed in a multiple parallel-operated DC/DC converters system. This paper proposes the hierarchical control scheme to achieve higher efficiency and superior anti-disturbance ability for multiple DC/DC converters with virtual synchronization-based control. The primary control layer enables proportional power sharing by using improved virtual synchronization control for each DC/DC converter, which aims at eliminating the influence of line parameter mismatch among converters. The secondary control layer deals with DC voltage stability improvement through the extended disturbance-observer-based backstepping control with the consideration of external power fluctuation on the whole system. Two control levels are integrated as the hierarchical control architecture to realize different control objectives in different time scales, while only neighbouring communications and DC voltage information are needed among the system. Simulations on PSCAD/EMTDC are conducted and show that the load power is accurately and proportionally shared, while system oscillations are eliminated with the extended disturbance-observer-based backstepping control, which validates the advantages of the proposed hierarchical control scheme.