The energy storage system used in electric vehicles or plug-in hybrids remains the weak link: very expensive, limited in autonomy, slow to recharge. Today, the main axis of progress is undoubtedly based on the development of embedded energy storage systems. One of the promising solutions proposed by car manufacturers and scientific researchers is the hybridization of energy sources. The particular goal of this solution is to combine two complementary storage technologies, or to be more precise, a specific high energy technology for the main source on the one hand and a specific high power technology on the other hand as a second technology. This hybridization allows us to exploit the benefits of both storage components and gives degrees of freedom in system design.
Context and challenges
Current storages do not achieve both a good battery life and an on-board power that is compatible with the desired performance of an electric vehicle (for example, the acceleration and charging requirements as well as the lifetime requirements of the vehicle. battery). Pathways for improving their performance can be envisaged by using secondary power sources, such as supercapacitors. This solution is based mainly on the combination of an energy-oriented and a power-oriented storage, where the power distribution is managed by one or more power converters. Hybridization of the sources makes it possible to have Hybrid Energy Storage Systems HESS hybrid energy storage solutions that are more efficient than the so-called single-source versions, whether from an electrical performance, compactness, or other point of view. lifetime or overall cost of use. For HESS, the choice of an appropriate energy management strategy (EMS) is necessary to ensure optimum performance of the entire electric power train.
Project objectives to address the identified issues
The main objective is to optimize the Total Cost of Ownership (TCO) of an EV by improving battery life and the use of a synchronous variable reluctance machine.
The project aims to strengthen knowledge transfer, networking and collaboration between companies and higher education institutions. On the basis of these ideas, the specific objectives are:
Development of the right technical combination of battery and electric machine, which allows the EV to be accepted by customers.
Evaluation of the influence of energy management strategies on the sizing and lifetime of a HESS (Hybrid Energy Storage System) source.
Development of intelligent energy management strategies based on predictive algorithms to improve battery life.
Selection and design of a compact power converter for HESS composed of li-ion batteries and a supercapacitor.
Development of optimal control for synchronous machines with variable reluctance, while minimizing the impact of current harmonics on battery life.
Construction of a small scale electric traction test bench based on a hybrid battery/supercapacitor source and a synchronous variable reluctance machine.
Development of a holistic model for energy management and prediction of the lifetime of the hybrid source.
Refining and validating the battery model developed for batteries using cycling and programmed impedance tests, combined with other in situ methods.
Development of test equipment dedicated to advanced in situ diagnosis of batteries for cell ageing.
Prediction of the life span of Li-ion batteries and their comparison in hybrid and single source use.
The proposed solution will be based on the use of a hybrid source combining the advantages of two complementary technologies in terms of specific power and energy density, as shown in the figure below. The system will consist of a li-ion battery and supercapacitors. A bidirectional DC/DC converter will be required on the supercapacitor side to ensure power sharing between the two storage units. This system is coupled to a synchronous variable reluctance synchronous machine without permanent magnets that will be used for vehicle traction. This machine is coupled to a DC/AC converter to control the speed of the electric vehicle.
The consortium relies on three main academic partners (INSA Strasbourg, Hochschule Karlsruhe and Hochschule Trier) and three associated partners (Centrale Lille, Université de Nantes and Sheffield Hallam University), with complementary skills. The CCI will support the dissemination activities of the VEHICLE project to industrialists in France and the Upper Rhine thanks to their proximity to companies in Baden-Württemberg in Germany. In Rhineland-Palatinate, Commercial Vehicle Cluster - Nutzfahrzeug GmbH (CVC - Südwest Kaiserlautern) will be associated and will act as a relay for member companies in the automotive sector.