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Towards a fast-uptake of mEdium/Low-voltage eLectric power trains

Periodic Reporting for period 2 - TELL (Towards a fast-uptake of mEdium/Low-voltage eLectric power trains)

Reporting period: 2020-06-01 to 2021-11-30

The TELL project addresses the optimisation and large-scale manufacturing of low and medium voltage electric powertrain solutions, with focus on high efficiency, compact packaging and low cost. Three main applications are targeted:
• Small-to-medium segment electric cars
• Hybrid electric cars with a low voltage add-on electric propulsion system
• The lightweight urban mobility sector, e.g. electric quadricycles
The project aims
• to develop innovative, integrated and modular powertrain solutions targeting the 2030 requirements of urban electric vehicles across different brands and regional markets
• to enhance efficiency, range, reliability, safety, dependability, by applying emerging semiconductor technologies and a low-voltage approach
• to demonstrate the TELL powertrains within an innovative electric vehicle architecture developed in previous projects and featuring high degree of security, user friendliness and acceptance
• to develop production methods targeting high-volume automotive-quality manufacturing at affordable cost
The TELL powertrains will be demonstrated on two electric vehicle platforms: i) a four-wheel-drive vehicle operated at a nominal voltage of 100 V by a Si MOSFET based inverter; and ii) a two-wheel-drive vehicle operated at a nominal voltage of 48 V by an inverter based on GaN and Silicon semiconductor technology, including a comparison of both sources regarding usability in the near future.
The cooperation between 5 partners from three countries was passionate and very successful.
In the course of the first period (M01-M18), TELL has completed the powertrain specifications and the reference vehicle for urban mobility has been developed. The low-cost electrical system based on 48 V machine has been designed and the performances have been calculated. The requirements of the Medium-Voltage powertrain made of NewGen MOSFET inverter and SynRMaPM machine have been defined.

In the second reporting period (M19-M36) the following work has been performed:
• The 48V electric machine and inverter development (prototyping and evaluation) have been completed. The complete electric system has been evaluated and validated.
• The GaN power module development was initiated to provide the design rules for future applications of the GaN technology at the same time as its maturity develops.
• A highly efficient and cost-effective powertrain has been developed, made by:
o A cutting-edge technology inverter based on 150V Si MOSFET with DBC power modules and able to optimally control synchronous motors.
o A novel synchronous motor mostly based on reluctance and assisted by permanent magnets.
• Both motor and inverter have been developed considering the efficiency and performance but also manufacturing aspects to ensure a cost effective solution.
• The development of three different vehicles integrating a 4WD operating at 100V and one vehicle mule developed so that a 4WD powertrain at 100V and 4WD powertrain at 48V could be easily interchanged.
• Advanced and Robust Control Algorithms in the two powertrains
• The implementation of a quantum secured protection of the E-E architecture
• Validate the performance of the vehicles with the 4WD different powertrain architectures.

The electrotechnical studies allowed to fix the main parameters of the electric machine, by dimensioning the main components of the machine for powers between 30kW and 35kW requested (dimensions of the stator and the rotor, magnets position, maximum theoretical temperature of electric conductors and magnets). The machine design has been done to ensure an optimal integration on 2WD vehicles. The manufacturing and the evaluations (electric and thermal) of the electric machine have been done.
Development of a power module based on bare die MOSFETs allowed the operational inverter to be evaluated on the electrical machine. The start of the development of power module based on embedded MOSFET showed promising result in terms of thermal resistance (equivalent or best than conventional assembly) and conduction losses thanks to an optimized routing allowed by driving circuitry and first stage filtering close to MOSFET, enabling the use of 150V blocking MOSFETs instead of 200V. This resulted in better efficiency and higher power density of the inverter.
The study with simulation of the GaN power module showed reduced commutation losses because of the missing reverse recovery losses in GaN HEMTs (to be confirmed with real part testing coming in the next project: Multi-Moby). Nevertheless, preliminary mock-up assembly has been performed without problems during manual process.
The development and validation of a highly efficient and cost effective Medium-Voltage (100Vdc) power train made by an innovative inverter and a novel synchronous reluctance electric motor assisted by permanent magnets has been completed. The provided prototypes of the powertrain were integrated on 4WD demonstrator vehicle.

The gained knowhow within TELL will be included in academic sector for industry-related education and helps the industry partners to strengthen the market position and to adapt their products towards the market needs. These products will be implemented in the supply chain of urban electric vehicles in the near future.
For the dissemination, the project joined the E-VOLVE cluster for joint presentations and created several newsletters. The website was updated continuously and 6 publications were submitted, 4 of them already published in open access. The dissemination work will continue after the project end and 2 more conferences are already planned.
The TELL project targeted and achieved progress beyond state of the art in different segments of the value chain.
• Semiconductor components (switches)
o The used technologies for the bare die samples within the TELL project are leading edge in many key parameters.
• Inverters and motors
o Integration of new power stage, combined with the optimized inverter layout, achieved unsurpassed efficiency levels.
o Another remarkable result is the strengthened reluctance torque of SynRMaPM technology. It was possible to increase the reluctance torque contribution and reduce the rest which is generated by permanent magnets. This was achieved without compromise on performances and efficiency, leading to an excellent cost/performance ratio.
• Algorithms
o Goal in TELL was the real-time implementation of advanced vehicle control algorithms based on nonlinear model predictive control.
o This was achieved by detailed research in many chapters of the vehicle control (evolutionary research based on already proven concepts).
o Progress beyond state of the art can be clearly stated proven by several publications in peer reviewed journals.
All the developments made in the TELL project are fully integrated with the product development roadmaps within the enterprises of the consortium (GSME, IFAT, IFEVS, VEEM). All in all, the vehicles, the two powertrain systems and the Electrical and Electronic architecture, developed in the TELL project validate the specific impact to maximise the efficiency at low speed in urban driving cycles.