Persistent disturbance rejection of battery/super-capacitor hybrid energy sources applied in hybrid electric vehicles

The hybridization of batteries and super-capacitors (SCs) is prevalent in the study of electrical powered vehicles. SCs, having high specific power, are able to afford large amount of energy in a short period, and thus have been used to satisfy transient load power demands and capture the braking power. In this paper, the SC, also able to afford large number of charge/discharge cycles, is used to absorb persistent sinusoidal disturbances in hybrid electric vehicles. The disturbances stem from the engine torque ripples compensation by the electric machine, which is elaborated in the paper. The disturbances lead to oscillations in the DC bus voltage and in the battery current. The objective is then to attenuate the oscillations by absorbing the disturbances in the SC. Passivity-based control method and error output regulation method for nonlinear systems are exploited to control the DC-DC converters.