Incorporating Pulsed Transit Load Through Coordinated Control of Hybrid AC/DC Microgrids

Abstract

The consumption of electricity is expected to have a paradigm shift due in part to the electrification of public transportation. Currently, the penetration of electric vehicles is small but is predicted to increase, including fully electrified buses within each major city’s public transportation system. The electric buses provide many benefits but present a unique problem when the ON/OFF charging scheme is proposed with on route charging. This will create a highly pulsed load profile, which will have power quality, reliability, and stability issues. A community of hybrid AC/DC microgrids is proposed to alleviate the impact of the load via controlling a hybrid energy storage system (ESS). Each bus station will be modeled as a microgrid and will include battery-supercapacitor combinations as distributed resources to be shared among the network as required by the charging needs. The control is split into three modes, ESS Prioritized, Supercapacitor Redistributed, and Grid-Tie modes, which are dependent upon the available resources and the expected charging load. The ESS Prioritized mode is where the supcapacitors and battery are used to handle the load, the Supercapacitor Redistributed mode utilizes the supercapacitor redistribution effect for energy savings, and the Grid-Tie is used to charge the battery and handle the load by using the AC grid.