Design and simulation of an off-board dc fast charging station for electric vehicle battery

Abstract

Conventional fossil fuel-driven vehicles have caused acute environmental pollution. This demands the obligation of developing automotive industries that manufacture vehicles with lower carbon footprint impact on the environment. In the light of this need, electric vehicles (EVs) appear to be the best-suited alternatives to the conventional internal combustion (IC) engine. Despite having environmental benefit, electric vehicles charging creates a negative impact on the power grid. In this project, the unidirectional off-board level-3 EV charger was designed and simulated in Matlab/Simulink. This off-board charger has been divided into two parts. The first part is AC-DC converter where this part is controlled using voltage control approach to ensure standard grid voltage can be smoothly maintained, and to maintain the DC-link voltage at the constant level. The second part comprises the DC-DC converter, which functioning to ensure the battery can be charged within a specified limit using a constant current/constant voltage approach. From the executed simulation, it can be concluded that the proposed off-board EV charging station for 4 EVs units has been successfully designed and developed. As outcomes, the AC grid voltage has been successfully maintained its smooth sinusoidal waveforms even at full-load conditions. So does with the AC grid current and voltage where the total harmonic distortion (THD) level for both signals is within the permissible limit under the IEEE Standard 519-2014 requirements: under 8% for the bus voltage and under 5% for the current. When the number of EV unit charged is increases up to 4 units, current total harmonic distortion also increases. However, the AC sinusoidal grid voltage can be still smoothly maintained. The DC-link voltage has been also successfully maintained at the 800V constant level. For the battery safety condition, charging can be executed as required without overheating the battery.