Average-Value Model of Electric Vehicle Chargers

Analysis of voltage regulation impacts on distribution circuits due to electric vehicle (EV) battery loads requires accurate representation of the charging system. An EV charger consists of power electronic switches with PWM control to achieve desired charging characteristics while minimizing harmonic injections to the secondary service entrance. A detailed device-level model is accurate but it requires a significant amount of time to run due to the high switching frequency of the converter. For this reason, a novel and generic model of EV battery chargers is proposed and developed for evaluating distribution voltage regulation issues. The proposed model is developed based on the average-value modeling (AVM) approach. It includes a rectifier circuit along with PWM control, boost converter and battery banks. Average dynamics of the switching circuit are obtained by averaging the effects of fast switching in the device that occur within a prototypical switching interval. The proposed AVM is validated against a switching model and the actual measurements taken at an EV charging facility and is found to be very accurate in approximating EV charger behavior.