Supervised bidirectional DC/DC converter for intelligent Hybrid Electric Vehicles energy management

In this paper, an innovative supervisory control strategy for application on HEV energy management has been presented. An implementation for a basic DC/DC converter has been discussed, where a configuration composed by a LV battery and an HV bus fed by a battery has been arranged. The Recovery mode, discussed at length in this paper as an innovative method to overcome high-voltage bus drops due to sudden power peak demands from a traction motor, has been implemented by using a control structure based on a sliding inner current loop and an outer voltage loop, whose stability has been demonstrated by resorting to control theory results. Reported simulation results demonstrate the effectiveness of the proposed approach, considering the ability of the supervisory strategy to automatically switch from Buck to Boost, when an additional power supply is required from the secondary battery source, and return back from Boost to Buck, when the HEV is in normal cruise conditions. Experimental results will shortly follow in order to finely validate the intelligent strategy here discussed. The outlined approach is fully applicable to different DC/DC converter types, because it regulates the duty cycle value, common variable for each converter despite the effective adopted modulation strategy. Besides, an extension of the supervisory control strategy for braking energy recovery is currently under study.