Comprehensive energy efficiency analysis of series hybrid electric vehicles with dual-phase-shift-controlled DC-DC converter

Abstract

By considering converter fundamental operating principles, the paper first derives a complete set of analytic expressions of the overall power losses of a conventional Dual Active Bridge (DAB) bi-directional DC-DC converter under Dual Phase Shift (DPS) control. Expressions for conduction and switching losses in the electronic devices acting as the converter switches, and copper and core losses in the isolation transformer, are derived and accounted for in the DC-DC converter model. DPS control involves many more converter operating conditions, in comparison to the more common single-phase-shift (SPS) control, which makes the analytic power loss characterization of a DPS-controlled converter an arduous task. Subsequently and by employing the derived analytic converter power loss model with exemplary parameter values, the paper analyzes the efficiency of a high-fidelity full hybrid electric vehicle (HEV) model that includes a DAB DC-DC converter, under a wide range of realistic driving conditions and converter operation, including low- to high-speed driving, and converter DPS operation. Two popular hybrid powertrain energy management schemes, the Thermostat and Power Follower control strategies, are used to simulate the vehicle model to reinforce the range of realistic vehicle operating conditions. The results show that in series HEV applications more accurate modeling of DC-DC converter models than conventional constant efficiency models is required to predict converter losses, and also the fidelity in the characterization of converter losses can have a significant impact on the vehicle fuel consumption prediction.