Abstract

Background: The overall performance of the hybrid electric vehicle is mainly governed by the energy storage systems characteristics with respect to their power and energy density. The batteries have a good energy density, while the Supercapacitor (SC) has a good power density.

Methods: This paper presents a hybrid auxiliary source combined with a battery and the supercapacitor to use both characteristics of auxiliary energy source for Hybrid Electric Vehicle (HEV) application. The PI control technique manages the power flow so that the supercapacitor fulfills the transient power, and the battery supplies the steady-state power. The parameters of controllers are tuned by Ziegler Nichols and the frequency response-based method.

Results: The performance of the controller is evaluated by error coefficients (IAE, ISE, ITAE and ITSE). The model with different tuning parameters is simulated for fixed and variable reference inputs. The speed, dc bus voltage, and error coefficients are evaluated for the battery alone and battery- SC combinations.

Conclusion: The value of error-based parameters suggests that controller parameters tuned by the frequency response-based method provide better results. The error coefficients for batterysupercapacitor combination are lower than battery-alone systems indicating the better performance of hybrid input.

Keywords: Hybrid electric vehicle, battery, super-capacitor, power density, energy density, bidirectional converter, PI control. Z-N tuning, F-R tuning.