A novel hybrid energy storage system using the multi-source inverter

Abstract

This paper introduces a new active Hybrid Energy Storage System (HESS) topology which utilizes the multi-source inverter to interconnect a battery and an ultracapacitor directly to the three-phase load without the use of any additional power electronic converters or DC/DC converters. A new control strategy has been developed which periodically switches the operating mode of the multi-source inverter at a high frequency in order to maintain smooth current sharing. A duty cycle can also be selected to bias the use of one energy storage device over another which enables control over the discharge rate of the two sources. Closed-loop control simulations for an Urban Dynamometer Driving Schedule (UDDS) with torque and speed references driving an electric machine have been performed to verify the operation principle of this novel HESS topology. The influence of the additional control parameters on the source currents and their State of Charge (SOC) has been further investigated through simulations. Moreover, experiments in open-loop control with a scaled-down prototype and a R-L load have been carried out and validated the theoretical influence of the new control on the input DC currents. By an appropriate choice of the new control parameters, the average battery current and the battery current ripple can be reduced by up to 90% and 60% respectively compared to traditional electrified powertrains that only uses a single energy source.