Master–slave DC droop control for paralleling auxiliary DC/DC converters in electric bus applications

Abstract

This study reviews the causes of power losses in a DC/DC converter, relates those losses with efficiency profiles, and details different strategies for maximising efficiency when several converters are placed in parallel. The research is focused on electric bus applications, where several converters are usually connected in parallel in order to fulfil the power requirements of the bus models. In a bus, the low‐voltage DC link (28 V) resembles a microgrid that has some generators (DC/DC converters), an energy storage system (lead–acid batteries) and certain loads. To share the converters’ output power, a droop control is proposed. Furthermore, traditional droop control is improved by adding a master–slave control. The proposed master–slave droop control improves efficiency by more than 3% at low power with no additional hardware. Experimental results show how two 5 kW converters work in parallel using the proposed control.