Modelling of a dc fast charging station for electric vehicles

Abstract

The trend of the energy sectors around the globe is to lean more towards alternative and renewable sources of energy due to the increase in carbon emissions and inevitable shortage of fossil fuel-based sources. Among those technologies are Electric Vehicles (EVs), which are a green emission free replacement for the traditional Internal Combustion Engine (ICE) vehicle. The charging infrastructure is a major concern among potential EV customers, with emphasis on fast charging ability, especially for highways and long-distance commutations. In this project, modelling of a DC Fast Charging (DCFC) EV Station is designed and modelled using Matlab/Simulink software. The developed DCFC model comprises 2 main conversion stages which are the AC/DC stage as well as the DC/DC stage for regulating and charging the EVs. The control method used for the AC/DC convertor is the synchronous frame reference voltage & reactive current control, while the charging control is a Constant Current/Constant Voltage (CCCV) control. An LCL filter was designed for the harmonic mitigation as it shows superior performance to traditional L and LC filters. The DCFC station was simulated for the case of 2 EVs charging and 4 EVs charging. The results obtained show the state of charge (SoC) of the EV battery has been successfully charged from 35% to 85% SoC in 16.6 minutes, in which considered as an acceptable fast charging time according to the market standards. Also, the AC grid current in both cases of simulation had a THD of lower then 8%. Finally, the DC bus voltage was successfully maintained at a constant voltage level, 600V. The presented simulation results proved that the developed model with its applied control strategies demonstrated the principle work of a DCFC EV system.