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My research interests and activities

My perception of research in this field

I am not pretending to challenge the view of several professors and experts in the field, but I am entitled to some personal views :-). Here are the main points that fuel my research.

Combining machine design and control

The days of electrical machine design separated from electrical drives are soon to be over. Reality tells us that modern applications like renewable energy generation, electric traction, robotics and others cannot survive without power electronics. Much is still to be gained in designing a machine+converter system, rather than an optimization of the single components.

Drives are very intelligent devices

Electric drives are extremely powerful devices in terms of computational capabilities, and they become better and better as the microprocessor/FPGA technology improves. Said that, the typical control structures for electrical machines do not typically require much computation (unless you work on predictive control, but that is another chapter of discussion). This means that there might be a lot of unused computation, which could be exploited for real-time condition monitoring of electrical machines and drives, as well as for improving real-time estimation of electrical parameters.

Estimating parameters is an evergreen

I am an extreme fan(atic) of automatic procedures for the estimation of electrical (and why not, mechanical) parameters in drive systems. That is for the simple reason that control algorithms require a series of information that typically is not available in machine nameplate data. Someone, or rather something, has to retrieve that information.

I truly love when the converter is able to automatically extract all the relevant control parameters by performing autonomous injection of voltages and post-processing of currents. All of this just by software, based on few elementary nameplate data. And mind you, it must run without relying on information on speed and position of the rotor, as required by sensorless control algorithms.

As new electrical machine designs are proposed and built all over the world, the challenge of making the automatic estimation procedures as general as possible, while maintaining their reliability, is evident. Call it an influence of my past industrial experience, if you want - but I believe this is a real challenge.

Multi-phase machines are coming (and may have already passed you)

I am also leaning towards the benefits of using multi-phase machines (where the number of phases is greater than three) in applications where it makes sense, and there are many. There is a lot to discuss about this, but what I like the most is: 1) winding factors are generally better than corresponding three-phase machine designs, with harmonics located at higher frequency and with lower amplitude, and 2) there is a possibility of implementing true fault tolerance, which means running at a reduced number of phases without being forced to stop the whole drive system. Be aware that this second point requires a combined research effort of machine design, converter design, health condition monitoring, control reconfiguration, and so on... separate scientific efforts are just not enough.

On reducing the costs...

Throughout the years, I have been listening to many research works and presentations aiming at "reducing the costs" of a machine, a drive, or both. What is your definition of cost? Mine is very close to this one. I do not consider any other definition worthwhile.

Co-supervision of Ph.D. students

Note: until I officially become a Docent, I cannot operate as the main supervisor of Ph.D. students. Therefore, for the time being I act as co-supervisor of the following Ph.D. projects. Mind you: avoiding the burden of main supervision may be relieving sometimes :-). But I will become a main supervisor, eventually...

1. Giovanni Zanuso, "CALM - Collaborating network of large electrical machines", 2016-2021

Ph.D. project running at KTH under the main supervision of Prof. Viktoria Fodor. This project aims at performing local condition monitoring of the ageing of stator winding insulation, through techniques of stator current oversampling and post-processing in electrical drives. At the same time, the project tries to create a vision/infrastructure for the communication and exploitation of the condition monitoring information among several drives employed in the same industrial process. Process optimization and predictive maintenance are among the final goals. The project has a web page describing our collaboration with industry and VINNOVA.

2. Kristian Rönnberg, "NECEM - Next generation cool electrical machines", 2017-2022

Industrial Ph.D. project running at ABB Corporate Research, Västeräs, Sweden. The main supervisor is Associate Professor Christophe Duwig. This project is financed through SSF (Stiftelsen of Strategisk Forskning), and aims at introducing innovation in the design of cooling systems for electrical machines, by means of computational fluido-dynamic simulations.

3. Gustaf Falk Olson, "Parameter estimation of multiphase electrical machines", 2019-2024

This project runs at KTH, with the main aim of estimating the critical electrical parameters of multiphase machines for control purposes by means of software algorithms. The focus is half on the time-varying parameters (resistances or flux from the permanent magnets, for example), and half on the often-neglected, current-ripple-related leakage inductances. The path to achieve a statistically robust estimation seem to go through the use of output error identification algorithms.

4. Yixuan Wu, "Control of multiphase electrical machines in normal and post-fault operation", 2019-2024

This project runs at KTH, with the main aim of implementing a true fault tolerance system in a multiphase drive. True fault tolerance is interpreted as the ability of the drive system to exclude a faulty phase only and continue the drive operation with the remaining healthy phases, without necessarily shutting down other phases. It is not as straightforward as we describe it...

5. Mesfin Tilahune Tessema, "Control of multiphase electrical machines", 2019-2024

This project runs for 50% at Addis Ababa University in Ethiopia, and for 50% at KTH, with funding coming from the Swedish agency SIDA (Styrelsen för internationellt utvecklingssamarbete). The aim is to develop a control strategy for multiphase machines, with special interest in machines with the ability to reconfigure their number of phases or poles. Potential applications of such machines are found in the automotive scenario.

6. Omer Ikram Ul Haq, "ReWinD - Reconfigurable Winding electric Drive", 2020-2025

Industrial Ph.D. project running at ABB Corporate Research, Västerås, Sweden. This project is financed through SSF (Stiftelsen of Strategisk Forskning), and aims at analysing multiphase machines with the ability to reconfigure their number of phases or poles with the industrial perspective of an electric drive supplier. In particular, the project should cover the analysis of benefits/drawback of reconfigurable multiphase machines for specific applications, and implement a control strategy in the ABB industrial drives to cope with the on-the-fly reconfiguration of the number of phases or poles.

7. Smrutiekha Sahoo, "HECARRUS - Hybrid ElectriC smAll commuteR aiRcraft conceptUal deSign", 2017-2021

This project runs at Mälardalens högskola in Västerås, Sweden and is funded by the European Union's Horizon 2020 Research and Innovation Programme "Clean Sky 2" under Grant Agreement 865089. I have been asked to join the co-supervision team just in 2020, to give a helping hand for defining the design criteria and optimization procedure for electrical propulsion system components in hybrid electric aircraft conceptual designs.

M.Sc. thesis projects, B.Sc. thesis projects, individual project courses, internships, etc.

I usually have at hand a list of possible projects, either internal or in connection with industry. Feel free to contact me for further details. Keep in mind that I am particularly keen on laboratory experience for the students, so most probably my proposals will contain some "hands-on" work.