Influence of a workplace electric vehicle charging station's design and control on grid impact

With the increasing adoption of electric vehicles (EV), the electricity grid is majorly impacted due to its uncertain charging requirements, especially when there is a high penetration of distributed renewable energy sources such as photovoltaic systems (PV). Along with solutions including intelligent control of electric load with a battery energy storage system (BESS), an optimal design of the EV charging infrastructure is vital. Simulative analysis could help to evaluate the costs, self-sufficiency, self-consumption and grid impact indicators. However, grid impact indicators have not been evaluated for EV charging stations so far. This paper deals with a DC-coupled EV charging infrastructure that is connected to a PV array, BESS and the electricity grid. The system is evaluated for a workplace environment. The charging infrastructure includes a variable number of AC and DC charging points. A load shifting algorithm is introduced in case the PV, BESS and grid inverter cannot cover the load. Furthermore, a charging algorithm which maximizes self-consumption is introduced. Economic optima with and without the charging strategy are used as reference systems for evaluating the grid inverter's and battery's sizes as well as number of charging points influencing electricity costs and grid impact indicators. The results show that according to seasons in Germany, the southerly oriented PV of 15° tilt cannot cover the load between November and February and depends on the grid irrespective of the number of charging points and battery size. With the help of a selfconsumption maximizing charging strategy, the grid impact can be significantly reduced. The charging strategy has a far more positive influence than the variation of component sizes. A BESS can slightly increase the charging strategy's positive influence but has not shown economical advantage in the considered scenarios.