19 January 2023
CEA and Renault develop wide-bandgap-based bidirectional on-board charger for EVs
CEA (the French Atomic and Renewable Energy Commission) and Renault Group are working on future generations of vehicle-to-grid (V2G), the bidirectional exchange technology that enables electric vehicles to restore part of the electricity stored in their batteries to optimize the operation of the grid and compensate for the intermittent nature of renewable energies.
To this end, the CEA and Renault Group have jointly developed a new electronic power converter architecture directly integrated into the charger of electric vehicles. The result of nearly three years of research and the subject of 11 joint patents, this power converter, developed from innovative materials and more compact, should reduce energy losses by 30%, improve the vehicle’s recharging time and guarantee the battery’s durability. Also, it will be bidirectional by storing energy from the electricity network.
The CEA and Renault Group R&D teams have combined their expertise in on-board power electronics, in particular in wide-bandgap semiconductor materials, whether gallium nitride (GaN) or silicon carbide (SiC).
As a result, the new architecture based on the wide-bandgap semiconductor materials makes it possible to reduce energy losses by 30% during conversion, and to reduce heating by the same amount, making it easier to cool the conversion system.
Reducing the volume of the loader
In addition, the engineers’ work to optimize the active (semiconductors) and passive (capacitors and wound inductive components) components has enabled a reduction in the volume and cost of the charger. Due to the use of ferrite materials, dedicated to high frequency, and a shaping injection process (power injection molding), the converter has become more compact.
Towards more performance
This new converter architecture offers a charging capacity of up to 22kW in three-phase mode, allowing for faster charging of the vehicle while ensuring the durability of the battery. It also allows the charger to be bidirectional, so that the energy stored in the battery can be fed back into the grid or used to supply the energy needs of an autonomous house, provided that the house is equipped with a bidirectional meter. The solution is compatible with the electromagnetic compatibility (EMC) standards of the networks and the car.
“This project with the CEA has exceeded our expectations by confirming the ability to achieve the expected performance in terms of efficiency and compactness,” says Jean-François Salessy, VP advanced engineering, Renault Group. “It opens up strong prospects for power electronics, which is a real challenge in the electric vehicle, in order to make the best use of the batteries’ capacities. With bidirectional charging, the vehicle serves the electrical network and enables the end consumer to reduce energy costs,” he adds.
“We were able to bring together Renault Group’s system vision for the electrification of the vehicle and the drive train, and the skills of our teams in converter architectures and components; in the end, we implemented an architecture adapted to the needs and with high added value,” says CEA-Leti’s CEO Sébastien Dauvé.
“The use of innovative materials with joint Renault Group-CEA patents on the charger made it possible to manufacture the dedicated transformer, which is a key component in this type of development, as it allows for a reduction in volume with performance that goes beyond the state of the art,” says CEA-Liten’s CEO François Legalland.
Leti highlights progress in GaN power electronics