Ultra-high power density wireless charging for maritime applications

This project has developed design methods and control strategies for achieving increased power density of technology for inductive power transfer (IPT) at high power levels. The motivation for this development has been to enable utilization of IPT technology in maritime transport applications with high power density requirements. The general target of the project was to achieve a 50 % improvement in power density compared to a previously demonstrated IPT technology for high power battery charging applications, targeting a power density of the coils of 3 kW/kg. This as been achieved by developing a systematic approach for multi-domain modelling and methodologies for multi-objective optimization of components, system configurations and control strategies for IPT technology in maritime transport applications. The results obtained within the project demonstrate that the main target in terms of power density is achievable and that the performance can be improved even beyond the initial expectations. A laboratory prototype developed within the project has achieved a power density of more than 4 kW/kg, exceeding the initial development target by more than 33 %. At the same time, the activities in the project have identified several challenges for controlling the power flow in systems optimized for low weight by using a minimum number of components. Therefore, several methods for ensuring stable and accurate control of the power flow in such IPT systems have been developed within the project. These methods ensure that the system can be controlled to avoid or damp critical oscillations frequencies that can appear under certain operating conditions. The theoretical analysis and the methods for system design, modelling and control developed in the project provide a scientific basis for further industrial research and future development of solutions with significantly improved performance compared to the technology that has previously been demonstrated by relevant industries.

The project has enabled a coordinated development of knowledge and scientific capabilities for the involved research partners, which can be utilized for further joint research on new applications of inductive power transfer systems and other advanced power conversion systems. For the industry partners, as well as other industrial interests within the field of inductive power transfer and/or public transport, successful utilization of the results in future product development can open new markets and generate new business opportunities. Some of these opportunities might require further industrial developments of materials, components and systems, which can benefit from the knowledge developed by the research partners and open for further application-oriented research and development projects driven by the needs of the industry. Such outcomes can have significant impact on future technology development towards enabling utilization of wireless IPT technology in systems where low weight is of critical importance. In the context of the project, this can allow for further development of environmentally friendly and autonomous maritime transport solutions enabled by IPT technology. Furthermore, most of the results from the project can also be utilized for a wide range of other potential applications of high power IPT technology, including battery charging for road vehicles as well as off-road vehicles and construction machinery.

The purpose of this project is to advance the scientific basis for design of wireless inductive power transfer (IPT) systems for battery charging in applications with high power density requirements. By enabling more compact designs with high power transfer capacity, the project will allow for new applications of IPT technology in maritime transportation, especially for autonomous systems and high speed passenger vessels with battery propulsion, where low onboard weight is of critical importance. For achieving this objective, the project targets a power density of 3 kW/kg for the on-board coil, representing a 50 % improvement compared to publicly available information about optimized design of IPT systems, and an average power density of 2 kW/kg for the on-board installation. The targets will be achieved by developing a systematic approach for multi-domain modelling and methodologies for multi-objective optimization of components and system configurations. The optimization methods will be defined to identify possible advantages of utilizing alternative materials as well as various electromagnetic constructions, including asymmetric designs and/or designs without magnetic materials in the on-board coil. Thus, potential degrees of freedom in the design will be utilized to ensure minimized weight of the on-board installation, while still fulfilling demanding requirements for relative movements during operation. Since the necessary component ratings as well as the resulting losses and associated cooling requirements of IPT systems designed for handling a wide range of operating conditions depend significantly on the applied control strategy, the control system design also has to be carefully considered to ensure feasibility of ultra-high power density solutions. Thus, accurate dynamic models and corresponding methods for design and tuning of the control strategy must be developed to ensure that the full potential for minimization of on-board weight can be realized.