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Smart Converters for Optimized Power Usage and Storage

Periodic Reporting for period 3 - SCOPUS (Smart Converters for Optimized Power Usage and Storage)

Reporting period: 2021-10-01 to 2022-09-30

With the advent of high fuel prices, the global warming problem, and high operating costs there is a marked trend within the aerospace industry to move towards cleaner, more efficient, and lower maintenance aircraft design. One of the prime movers in this arena is the substantial electrification of the aircraft to replace hydraulic or pneumatic functions with electrical ones, as in the concepts of the More Electric Aircraft (MEA) and of the All-Electric Aircraft (AEA).
The development and implementation of advanced technologies which allow for energy efficient solutions with reduced environmental impact is of extreme importance: higher power conversion efficiency and better fuel usage, improved availability and safety and increased flexibility in space allocation at the A/C level, will result in lower operational costs and better performances of the MEA.
The SCOPUS project goal is an optimised and compact bidirectional and modular DC/DC converter, developed for straightforward integration in the modern decentralized smart electrical system of the More Electric Aircraft (MEA). The DC/DC converters employ wide bandgap semiconductors and soft-switching techniques (ZVS, ZCS resonant transitions) to achieve operation at higher switching frequencies thus allowing the reduction of size and mass of the converter passive devices, thus justifying, and accelerating the adoption of the innovative smart DC/DC converter and creating market opportunities for the European industry in face of emerging competitors in line with Clean Sky objectives.
The SCOPUS smart DC/DC converter also enable the implementation of intelligent energy management strategies in the diverse operational scenarios through the on-board controller, contributing to improve the electrical power network quality through the integration with supercapacitors and batteries but also with the A/C Health and Usage Monitoring System (HUMS).
The action concluded with the production of four bi-directional DC/DC converter modules rated 5kW, conceived to support parallel operation up to 20kW. The converters have undergone functional testing; completion of module testing and multi-module operation characterisation have been postponed due to scheduling constraints by the covid-19 pandemic and its subsequent effects.
The SCOPUS project Partners have designed, developed, manufactured, and tested the SCOPUS converters following the design flow of an aircraft-grade product.
The development started from the analysis of the requirements specification provided by the TM at the onset of the project. System level requirements were reviewed and equipment requirements derived. Existing and state-of-the-art technologies and designs were explored and the converter design continued through the architecture definition.
After the review of the requirements and the completion of the architecture design, the project Partners focused on the converter design, which included preliminary design - validation of equipment requirements and compliance with the preliminary design, analysis, and validation of the key components with a focus on magnetics, preliminary design analyses and 3D model – followed by a detailed design phase.
During the detailed design phase, the preliminary analyses were further refined and results confirmed; developed detailed CAD drawings, energy management controls, supervision, etc. The reliability of the converter was evaluated based on MIL-HDBK-217F supplemented by the VITA51.1 standard, and the improvements areas of the MTBF were highlighted for further developments. The safety of the converter has been analysed and safety-critical events have been investigated and redundancies introduced into the design. Safety critical events such as loss of isolation between the HV and LV sides of the converter have been thoroughly investigated and mitigated.
The project concluded with the manufacturing, assembly, and integration of four DC/DC converter modules. Environmental testing and multi-module operation characterisation of the bi-directional power converter were deferred due to scheduling constraints.
The impacts on project exploitation and dissemination due to covid-19 have been unavoidable, for example the Farnborough Airshow 2020 has been held in digital format. The Partners have communicated the SCOPUS project through social media and their company presentation. Posters have been presented at Le Bourget 2019, the Dubai Air Show 2019 and Farnborough 2022.
The University of Seville contributed to the dissemination of the project achievements through publications and one PhD thesis.
In the past years, several research and development programmes have initiated the concept of the More Electric Aircraft and All Electric Aircraft. In the H2020 framework several programmes are studying improved converters with higher power density, improved thermal solutions, advanced energy management and advanced power grids to increase the technology maturity in these areas. The SCOPUS project faced serious challenges in supporting the application of these concepts and developments beyond the state-of-the-art.
- Switching technologies for A/C power converters: the architecture of the SCOPUS converter is modular, highly flexible and includes a sophisticated controller capable of supporting alternative modulation techniques.
- High power density modular converters for the MEA: the SCOPUS converter adopted the three-phase DAB topology to achieve the maximum power density (5kW is the maximum power of a single module). Further investigations are required to confirm the power density that can be achieved through optimisation of the EMI filters.
- Wide Bandgap Transistors for use in demanding applications: one of the main objectives of SCOPUS is the effective implementation of wide bandgap devices in an aircraft power converter. SiC devices have been employed on the SCOPUS converter with excellent results.
- Robust modulation and control strategies for A/C electrical converters: the SCOPUS converter adopts a modular and highly flexible architecture and a sophisticated controller capable of supporting alternative modulation techniques is implemented. Further activity is foreseen for the development of ad-hoc strategies for the synchronization of the interleaved modules.
- Hardware In the Loop testing for accelerated integration of complex A/C equipment was exploited in the project
- EMI/EMC analysis and design techniques: design strategies aimed to optimize the size of EMI filters require further investigation.
By addressing the above challenges, the SCOPUS project contributed to technological advances for on-board power conversion. The expected impact of SCOPUS is totally aligned with the main goals of the strategy of the H2020 and its innovation and implementation will contribute to achieve the roadmap H2030 and H2050 related to the reduction of noise and emissions. Potentially, the power converter can be applied not only to different aeronautic platforms, small, medium, and big aircrafts, and helicopters, but also to the new concept of autonomous more- and all-electric aircrafts, and to trains, ships, and vehicle as well thus creating market opportunities for the European industry in face of emerging competitors in line with Clean Sky objectives.
Further developments are being considered by the project Partners.