Distributed secondary and tertiary controls for I-V droop-controlled-paralleled DC-DC converters

A hierarchical distributed control method for I-V droop-controlled-paralleled DC-DC converters in DC microgrid is proposed. The control structure includes primary, secondary, and tertiary levels. The secondary control level is used to remove the DC voltage deviation and improve the current sharing accuracy. An improved dynamic consensus algorithm is used in the secondary control to calculate the average values of bus voltage and voltage restoration in distributed control. In the tertiary control level, as the main contribution in this study, the system conversion efficiency is enhanced by using the average restoration value obtained in the secondary control level, instead of using the total load current which needs more communication traffic. When the converters are connected to batteries, the method for the state of charge (SoC) management is proposed so that the SoC balance can be guaranteed. The effectiveness of the proposed method is verified by detailed experimental tests based on four 0.7 kW DC-DC converters.