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Science & Technology Series: Research Spotlight

City engineering academics create new electrical power solution

Through their work on a novel multi-level inverter, City’s Honorary Professor Paul Riley and Professor Keith Pullen, have devised a potentially game-changing solution for controlling the power and speed of a light aircraft electric motor powered by a lithium-ion battery.
by John Stevenson (Senior Communications Officer)


LiBAT demonstration in Garching. The LiBAT battery powers an electric motor with propeller attached.
Powers of up to 3,25kW with currents up to 30 A peak value have been achieved at 2860 rpm in the tests  Photo credit: Wade Million

Engineering academics at City, University of London have created a potentially game-changing multi-level inverter for controlling the power and speed of a light aircraft electric motor powered by a lithium-ion battery.

Paul and Keith supplied the power electronics, while Dr Obrad Dordevic at Liverpool John Moores University (LJMU) developed and implemented converter and motor control for the lithium-ion battery system developed by German companies TWT GmbH and Lion Smart GmbH, in the EU-funded Clean Sky 2 project LiBAT.


The LiBAT project is aimed at designing and assembling a demonstrator of a battery pack with state-of-the-art energy density for an electrically powered glider.

Over the past month, the City academics and Dr Dordevic, who developed and supplied the control system for the electronics technology, have supported Lion Smart to drive a propeller with 3.25kW of power at 30A peak which spun at 2860rpm; enough to keep a glider flying in level flight.

Professor Riley says:

“The integration of multi-level-inverters into the battery as we have done on the LiBAT project is a solution known within the research sector. However, we have taken the bold step of applying it to mobility applications. We are confident that this game-changing technology will transform the battery systems sector for mobile applications.”

The City academics have explored the application of M2LeC multi-level inverter technology - a form of multi-level converter that combines the functions of generating electric motor wave-forms with battery charging and management in a single set of power electronics hardware, where the various functions are performed through software alone.

They have published their findings in the recent research paper, A Qualitative Assessment of a Modified Multilevel Converter Topology M2LeC for Lightweight Low-Cost Electric Propulsion, published in the July 2020 edition of the Engineering journal.

The LiBAT project braids together several important strands which provide the electric power for an electric mobility solution. Lion Smart integrated various components into the battery to create a tuneable alternating current (AC) battery.


Combined with their powerful immersive thermal management, and excellent energy and power performance, the modular design guarantees a scalable system that eliminates the need for chargers or inverters for motoring applications.

Given the low weight and volume of the pack, and with an energy density of 200Wh/kg and 3C continuous discharge currents, the design meets ambitious projects targets.

TWT GmbH coordinated the project, contributed to design and verification and performed simulations of the entire system to predict performance and correct earlier errors. Lion Smart GmbH provided innovative battery prototypes and was pivotal in the system design, prototyping and testing of the battery pack.

Suitable for electrified gliders

Applications for the LiBAT battery can be found in many fields, especially in electric air taxis, hybrid propulsion systems, flexible frequency auxiliary networks, electric vehicles and power tools. It is very suitable for electrified gliders, which were the focus of this research project.

Like many other research projects, LiBAT met several challenging situations during a COVID-19 affected year that culminated in a short-term location change for the final integration tests:

“We are glad that the EU gave us the possibilities to build this extraordinary battery system and supported us along the way. With the immense complications of the pandemic we are all extremely happy and proud to see the battery power the motor live today”,
Dr Jan Dahlhaus, the project coordinator at TWT GmbH, said, at the final demonstration in Garching.

This project has received funding from the Clean Sky 2 Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme under grant agreement No 821226.

The content of this news item is the sole responsibility of the authors, and in no way represents the view of the European Commission or its services.

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