Resilient Fast-Charging Parks for Heavy-Duty Vehicles

The electrification of the transport sector will require a huge expansion of fast-charging infrastructure in the medium-voltage range. According to forecasts by the Electric Mobility Control Center, approximately 440,000 to 843,000 public charging points for passenger cars will be needed by 2030. In particular, at high-traffic locations along transport routes, charging stations will need to integrate 2 to 6 charging points for heavy-duty vehicles in addition to the charging points for passenger cars. These in particular pose a major challenge in accordance with the megawatt charging system standard due to their potential charging capacity of 1 to 3 MVA, as this causes the required charging capacity to skyrocket and can amount to up to 30 MVA depending on the location of the charging station. Charging stations with power requirements comparable to those of small towns will therefore be built along transport routes. At the heart of this innovation is local energy distribution with direct current at medium-voltage level.

Initial Situation

The Megawatt Charging Standard (MCS) allows charging capacities of 1 to 3 MVA per charging point and thus currents of up to 3 kA. Technical solutions for setting up these charging points up to 1 MW already exist today, but there are no system concepts that pursue a holistic and technically and economically sustainable scalable approach.

Optimizing economic efficiency and resource efficiency requires consideration of all components and the entire system technology. This project aims to implement a system-optimized approach and develop the necessary components. Cost optimization, increased efficiency, and resource conservation are key factors, both during installation and operation. The core demonstrators are therefore the central rectifier, which feeds a DC bus of 3 to 5 kV, and galvanically isolated DC converters, which establish the connection between the vehicle and the DC bus. The exact voltage range will be determined as part of the concept study at the beginning of the project.

Objective

The fast-charging parks are considered hybrid power plants. This means that both battery storage and PV systems are integrated into the system design. The large area potential of car parks allows for PV systems to be installed as parking lot roofing in the order of 1 MW. Since solar power generation correlates very well with peak transportation times, load peaks in the power grid can be buffered and the fast-charging park's own consumption can be increased. The fast-charging park remains operational even in the event of a grid failure and could also be available to emergency and rescue vehicles for a further period of time, or be used as a decentralized power storage facility via the public grid for other critical consumers.

Approach

The core of the innovation consists of transferring energy in the charging station via a multiport direct current (DC) distribution network with a voltage of 3–5 kV. This is connected to the medium-voltage or transmission grid via central rectifiers that serve the grid. Insulating DC converters are connected to the charging points in the charging station. The high currents resulting from MCS charging pose a major technical challenge here, both from a system and a component perspective. Therefore, in addition to the power electronics demonstrators, inductive components and DC protection elements are being developed in this project.The isolating DC converters to be developed in this project should be able to be used not only for their main function as charging electronics, but also for connecting photovoltaic generators. The focus of the grid rectifiers to be developed is on the efficiency of the grid-friendly control technology, the modular design, and bidirectionality in order to ensure stability in the grid of the future.

The approach chosen in the project, which involves a high DC distribution voltage in the DC bus, reduces the use of resources in the area of cables and other system components. At the same time, the lower currents reduce operating losses. The consortium will develop and build the central components (grid rectifiers, DC converters, semiconductors, windings, and DC switching devices) for the system in the corresponding voltage class and test them on a laboratory scale.

The “ReNew” project is funded by the Federal Ministry of Economic Affairs and Energy (BMWE).