Accurate Determination of Optimal Amount of Charger Capacitors for PHEVs

Nowadays, because of the need to decrease fuel consumption and greenhouse gas emissions and also their capability of exchanging power with the grid and regulating the frequency and voltage of the grid at different times of the day, electric vehicles are used more than before all across the world. It is highly important to pay attention to the efficiency, and decrease in the weight and volume of these vehicles. The chargers of these vehicles can form a huge portion of the volume and weight of these vehicles. DC link capacitors are the large parts of these chargers. Based on the mathematical modeling and relationships of the system, this study focuses on the optimal capacitor value based on the required specifications. In the model presented in this article, the optimal value of DC link capacitor is estimated by taking into account instantaneous input power of the charger, the relationship of the energy balance between the grid and the DC link capacitor, and application of Taylor series to the output of the relationship. The optimal DC link capacitor value is estimated through calculating the DC link voltage, and measuring the exchanged energy and changes of DC Link Voltage during charging. The most considerable advantages of the proposed model are the simplicity of its design together with the minimum weight and volume of the charger due to its low capacitor value. SIMULINK environment of MATLAB software was used to evaluate the proposed model. The simulation results show that the model was successful.