Multistage time-variant electric vehicle load modelling for capturing accurate electric vehicle behaviour and electric vehicle impact on electricity distribution grids

Accurate electric vehicle (EV) load modelling is a daunting task because the proportion and characteristics of these extra electrical loads in the grids are continuously changing. In many recent EV studies, EV load is assumed to be a constant power load to analyse the effect of EV charging on electric network. However, such an assumption would not be effective in real-time application and can give misleading results. This study proposes a multistage time-variant EV load modelling technique based on the characteristics of EV load demand due to EV battery charging. To capture the transitions between different stages of battery charging, the EV loads are modelled with a multistage scheme and implemented ZIP model. A comparative study of energy losses and voltage profile is carried out on the IEEE 69-bus test system for the use of a traditional constant load model, conventional ZIP load model and the proposed multistage time-variant EV load model. Results show that the load models can significantly affect the energy losses and terminal voltages, and provide misrepresentation if EV load is not accurately modelled. Therefore, for proper analysis of EV loads during unidirectional charging, it is essential to have accurate models for predicting true EV behaviour.