Swiss demonstrator

The general aim of the Swiss demonstrator is to investigate and enhance the grid operation of a renewable-supplied power distribution grid in the presence of MW-class battery storage and EV charging stations for multiple objectives by using their controllable power electronics converters.

Therefore the fast charging station installed at the EPFL in the frame of the project not only charges electric vehicles, but also collects invaluable information and enables the enhancement of a battery energy storage system (BESS) control framework for the provision of grid services.

What do we learn from this framework? It consists of two layers: one for the estimation of the BESS usage the day ahead and one for the BESS optimal control in real-time to provide various grid services. This control framework includes an advanced forecast algorithm of the EV users’ behavior in terms of (i) the number of sessions per day, (ii) the arrival and departure times, (iii) the initial and final, SoCs (iv) the battery capacities, and (v) the minimum and maximum active power injections (imposed by either the EVCSs’ converters limits or by the EV on-board controller). The first experimental results at the EPFL demonstrate that the real-time control algorithm can accurately track the day-ahead plan.

The profitability of various services provided by the BESS was analyzed for Aigle too and it came up that peak power shaving (PPS) and backup energy storage provision alone, without participating in the frequency containment reserve (FCR) does not justify the purchase of the BESS. The increasing number of EV charging stations impacts the BESS Return on Investment (RoI) due to the fixed transformer size limit while upgrading the transformer will generate cost that needs to be taken into consideration in the BESS viability analysis.

On the basis of the demonstrator, user behavior has also been studied – based on a survey undertaken in the frame of the project, in Switzerland the EV owners are willing to extend their charging time in order to support the energy transition. They do so while the charging time is the more important decision factor for (61% of) them than the cost and the state of charge, i.e., how much their battery is charged. 30% of all participants in the survey would do it even without any compensation while 40% with a price discount