Picture of the SKALE process

SKALE – Scalable Charging System for Electric Vehicles

Objectives and Results

In order to be able to shape the transition to electromobility, appropriate charging infrastructure is needed. The problem of large load peaks caused by a large number of electric cars charging at the same time could be solved by coupling the charging points with decentralized renewable energy sources and stationary storage.


A corresponding charging infrastructure with the claim of high scalability and the ability for bidirectional charging is being built and operated at Robert Bosch GmbH. The charging system, a PV system, and a stationary lithium-ion storage unit are connected via a DC power distribution network with a central inverter. Additional vehicles can be charged AC-side. The aforementioned infrastructure is developed and optimized by the cooperation partners Robert Bosch GmbH, PowerInnovation Stromversorgungstechnik GmbH and Elektrotechnisches Institut des KIT for semi-public to private use.


In the project, the ETI at Campus North has the goal and task of developing an intelligent energy management system as well as a simulation and design tool for the charging infrastructure. At the South Campus, the project will conduct studies on the stability of distributed DC grids. In addition, the direct connection to the medium-voltage AC grid will be investigated.


Contents and Approach

First, the system requirements and effective chain interrelationships are implemented in a simulation. The simulation takes into account the electrical variables as well as the characteristic curves and limit values of the components and can simulate site-specific operating strategies. The economic efficiency of the system is also to be taken into account.
Based on the simulation, system interrelationships, efficiencies and simultaneity factors will be analyzed and thus a design recommendation for the demonstrator, which will be set up at Robert Bosch GmbH, will be created. 
Subsequently, based on the previous work, a design tool will be developed that can design and optimize the charging infrastructure including its components for a specific location.
Finally, the simulation and design tool will be validated and optimized and the overall system efficiency will be evaluated using real measured characteristic diagrams acquired by the demonstrator. The evaluation takes into account the efficient use of renewable energies.


KIT is also responsible for setting up the charging infrastructure as a demonstrator at Bosch GmbH.
An intelligent energy management system is being developed to ensure the flawless operation of the charging infrastructure. For this purpose, the corresponding algorithms will be developed and implemented in the demonstrator. Among other things, the influence of inaccuracies in user data will be evaluated.
After the demonstrator has been put into operation and functional tests have been carried out, the testing of the demonstrator will be accompanied. Based on the measurement data, the overall system efficiency, battery cell aging, operating concepts, infrastructure use and vehicle-to-grid application will be analyzed. The analysis takes into account the topics of economic efficiency as well as feasibility of different smart charging strategies.

For the investigation of the novel DC grid with regard to a robust and reliable operation of the DC grid, a detailed simulation model is to be created. The simulation model is to include all connected components with the respective internal circuit structure, so that an analysis and evaluation of the system behavior is possible with high temporal resolution in normal operation and under fault conditions. The results of the investigation are to be taken into account for the design of the prototype.
In addition, a medium-voltage converter for direct connection of the charging infrastructure to the medium-voltage grid is to be designed. In particular, the converter must meet the requirements in terms of efficiency, redundancy and conformity with the grid code. In addition, a small installation space is required for integration in parking garages. The developed concept is to be validated by building a downscaled laboratory demonstrator. 

 

Project Volume

4,3 mio. €
 


Further Information