How to talk to charging stations

It is essential to utilize the power grids more evenly with intelligent and flexible charging control of e-vehicle fleets. This not only avoids bottlenecks in the power supply, but can also lead to a reduction in costs for consumers thanks to possible savings in grid expansion.

When entire e-vehicle fleets are charged overnight with high peak loads, for example, by delivery or utility services, this presents distribution grid operators with not inconsiderable challenges. One potential risk is that without smart grid planning, supply and demand of renewable energies will be out of balance at peak times – and charging processes can thus not be fully carried out.

To prevent this, a dynamic, grid-side control of charging was developed as part of the federally funded research project “Netz_eLog” (intelligent grid integration of electrified logistics). In the process, a consortium of Reiner Lemoine Institut, E.DIS Netz GmbH and IAV investigated at a Deutsche Post DHL Group distribution center what flexibility potential e-mobility offers for the power grid and how these possibilities can be used in a grid-serving and transparent manner.

«In view of the increasing volatile feed-in of renewable energies, the use of flexibilities is becoming increasingly important for the power grid. Standardized, grid-serving controllability and advance planning of e-mobility in the distribution grid would significantly increase planning reliability for operators.»

Lola Wybieralski — Software Requirements Analyst at IAV

IoT platform for custom-fit communication

As a project partner, IAV has developed an IoT platform that enables interoperable communication between the systems involved in the project. The company took into account all the requirements of the distribution network and fleet operators and implemented an ideal control model for optimal charging of the logistics fleet in the form of a software-as-a-service application. Future values from forecasts and knowledge from past charging behavior were incorporated.

For IAV, the challenge was to provide completely new loading management software during ongoing operations at Swiss Post without disrupting the logistics group’s processes. To minimize any risk, IAV engineers had set up a quality assurance environment in advance at the development center in Gifhorn to test the software modules.

Thanks to the stable software architecture, trouble-free operation of the DHL site was possible throughout – the key measurement data in the area of e-mobility and buildings could be transmitted securely and visualized via the front end. This provided the charging control and individual settings.

Web sockets were used for data transfer between charging stations and backend. The interfaces for control commands from the network operator were provided via MQTT. Information from the site consumption was transmitted via HTTPS through installed measuring devices on the building. The process and format of the message transmission to the charging station were defined via Open Charge Point Protocol (OCPP).

More flexibility, lower costs

During the three-year term of the “Netz_eLog” project (2019 – 2022), four strategies were developed and successfully tested, and their effects on the site were precisely analyzed.

It is now possible, for example, to reduce the peak load by up to 50 percent by adjusting the charging strategy, resulting in immediate cost reductions for consumers. Intelligent control can avoid grid expansion even as the vehicle fleet continues to grow, and so electricity grid operators can also save costs.

Similarly, the power of the charging stations can be completely limited or ramped up to the maximum level by means of control – depending on the available electrical energy in the grid. For grid operators, tests of high-load time windows also yielded valuable conclusions in terms of flexibility.

«We have integrated the logistical criteria of the fleet operator and the requirements of the network operator into the charging control system. This is the first time that these two data streams have flowed together in one system - a real turning point.»

Frank Maerzke — Team Leader EV-Fleet Services at IAV

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