Receiving the good news from Luca Peretti back in 2022, I said to myself, “Yes! I finally joined a unique environment: the postdoctoral program focusing on total loss minimization. In the coming two years, I am going to dive into a new task at KTH Royal Institute of Technology.” I even said to myself that I am going to write a book by delicately presenting my experience from the rural mountains of Ethiopia all the way to China and then to Europe: Call it a personal biography if you may.
However, Youtube videos make it unbelievably terrible, and darkness shackles you to loneliness. Thus, I was in fear of the freezing weather. I asked everyone to gain knowledge about how to survive the winter. Yes, I received particularly useful comments on how to prepare for the winter. I also remember the Game of Thrones movie “Winter is Coming!” Man, this movie is a hell of a movie! It gave me a humble time during the Corona Outbreak. Once you start the game of the throne, there is no middle ground! Either you win or you lose. Anyhow, my appreciation goes to Matt, Yixuan, and Luca for giving me a remarkably useful suggestion. Therefore, I bought a winter jacket, shoes, etc. and prepared and geared up well.
My frustration with winter didn’t last long—I actually enjoyed my first snow and winter experience. It was truly fascinating! If there’s one thing I regret, it’s not trying ice skating. That would have been an unforgettable memory. My humble advice? Don’t trust those YouTube videos! They made it look terrifying, and I still hold a grudge against them for that.That said, be prepared for winter. Investing in the right clothing is essential to surviving and enjoying the season.
Having said a bit about my experience on the dark nights of Stockholm, let me take you to our project. First thing is first, I have been able to understand the concept of semiconductor loss and ways of improving semiconductor loss, either from a PWM perspective or a technological perspective. The semiconductor switching losses are directly proportional to the switching frequency of the inverter. Thus, having a reduced switching frequency is one of the approaches that could be adopted for motor drives. However, the noise and harmonic content of the motor current are vital to be considered. Therefore, a means of optimizing the switching frequency, loss, and current harmonic content is necessary. The introduction of selective harmonic elimination, the variable switching frequency approach, synchronous optimal PWM (SOPWM), and other approaches provide an alternative mechanism without changing the semiconductor technology. These approaches are somehow computationally intensive. Therefore, a less computationally intensive approach with good performance is vital. Proper modeling of the harmonic content of the motor current as well as the semiconductor losses of the inverter is equally vital.
The second approach involves utilizing wide-bandgap semiconductor devices, which are becoming essential in modern motor drives. Advanced semiconductor technologies like Silicon Carbide (SiC) and Gallium Nitride (GaN) enable operation at exceptionally high switching frequencies (in the MHz range). This results in reduced harmonics while simultaneously minimizing switching losses. Among these, GaN stands out for its superior performance. However, its blocking voltage capability limits its practical applications. For instance, commercially available GaN devices typically have a 650V blocking voltage, while companies like Infineon have developed GaN HEMTs with a blocking voltage range of 100V to 700V. The adoption of wide-bandgap technologies also facilitates the use of computationally efficient PWM techniques, such as Space Vector PWM (SVPWM) and carrier-based sinusoidal PWM. I had the privilege of working with Aurobay on leveraging GaN technology for loss minimization, which was an incredibly rewarding experience for me.
FPGA also provides a better digital control strategy. As such, I have been reading about how to implement the FPGA, which is fun to work on. Additional knowledge is accumulated along the way! My experience with FPGA programming has been quite surprising. While understanding the basics of FPGA programming wasn’t too difficult, working with the FMC112 ADC from ABACO turned out to be far more complex than expected. The manufacturer-provided code for the device is intricate, and I spent a significant amount of time trying to understand and debug it.
Despite my efforts, I kept encountering issues. Sometimes, I could receive the signal, but other times, it was completely absent. As a result, the AXI_STREAM_FIFO remained empty. Even when the signal was present, the data read from the FIFO was often zero, leaving me frustrated and confused—how was this even happening? After extensive debugging, I discovered that the problem originated in a specific section of the system, which I refer to as the “red box” in the data processing flow as shown in Fig. 1. If the system failed at this point, everything downstream would collapse. Further investigation suggested that the issue might be related to ADC triggering.
After struggling for a long time without a clear solution—despite reaching out to the manufacturer’s support—I decided to take a different approach. I bypassed the “red box” entirely and designed my own custom FIFO. My implementation takes the 16-bit signal from the FMC112, converts it to 64-bit, and incorporates a 64-depth FIFO memory, allowing for smoother data handling.
Fig. 1. A block representation of the ADC implementation
The newly designed FIFO successfully resolved my issue, allowing me to disable the “red box” from ABACO. What a relief after spending such a long- and frustrating-time debugging FPGA programming and deciphering the inner workings of the ABACO FMC112 model! Despite the challenges, this experience turned out to be incredibly valuable. It not only deepened my understanding of FPGA programming but also sharpened my problem-solving skills. Looking back, it was a tough but rewarding journey. The following figure shows the custom designed RTL.
Fig. 2. Designed 16to64 bit FIFO with a FIFO depth of 64
One important lesson I’ve learned is that failure is valuable. You can’t fail unless you take the initiative to start something. In this sense, my repeated struggles with implementing the ADC turned out to be an opportunity—it pushed me to dive deeper into FPGA programming and expand my understanding of this powerful technology. Had I succeeded immediately, I wouldn’t have explored FPGA programming in such depth. In retrospection, the challenges were not setbacks but a new path to greater knowledge and expertise.
In conclusion, this opportunity has truly opened new avenues for progress, from sensorless control of electrical machines to drivetrain loss modeling and the development of optimized drive systems. It has been a transformative experience, expanding my knowledge and skills in advanced motor drive technology.
in the last two weeks I have been visiting two very different conferences back to back.
The first one is ICEM 2024, the international conference on electrical machines, a biannual conference on electrical machines and drives. I would dare to say that it is the most relevant conference on our field in Europe. It was this time held in Turin, Italy at the Politechnico di Torino. I went there to present preliminary results I got from an exchange stay at the University of Bologna. But this conference was more like a gathering of everyone. I met all the people I have met in all the conferences in the last five years including most of the professors from all the papers I was reading. This means that other than presenting and listening to potentially relevant presentations for my work, the breaks were times to say hello to known faces and get to know new ones.
A major part of research is collaboration since nobody can do everything. So, running around and find out what other people are working on is an integral part of attending a conference. Of course, it is also a good chance to meet people from industry and see which problems they are trying to solve. If you want, to break out from the academic bubble.
As you can imagine, such a conference day can be very exhausting. Luckily, the social dinner was held at MAUTO, the italian museum of automobiles. Since Turin is the city of the car manufacturer FIAT, there is a long tradition this industry. While receiving a fancy italian dinner with local dishes, it is a great opportunity to unwind and chat with the fellows.
Social Dinner at ICEM 2024
Porjus hydro-power plant original 1910 station.
After this week, I needed a break and spend the weekend in north Italy for some relaxing days before continuing to the STandUP academy in Luleå. STandUP for energy is an organization in Sweden funding research in energy related topics. On this annual gathering, researchers from KTH, Uppsala Universitet, Svenska Landbruks Universitet and Luleå Tekiska Universitet gather and discuss their results. As part of this, we visited the newly constructed hydro-power plant in Rengård, the wind-power plant in Markbygden and the larger hydro-power plant in Porjus.
I was very impressed by the implications of our energy production on the landscape and the environment but also by the technology and current questions.
A big misconception in the academic world is that working hard and working smart are the same. Well, they are not.
You could also entitle this post “Save yourself before it is too late.” It is a message to those falling into the spiral of death in academia.
We need to go back in time: it is the winter 2008-2009, and I am a doctoral student at the University of Padova, temporarily dispatched to ABB Corporate Research in Västerås, Sweden, for five months. This is the same place where I got my first employment in 2010 and where I stayed for eight years of my professional life.
During that period, ABB advertised a researcher position in the team. Many candidates came to Västerås for the interview. In one case, the team manager asked me to join the candidate’s technical presentation and then asked me to talk privately to this person to understand him more from a personality standpoint. I was culturally closer to this person than the manager, so he relied on that to know more about the candidate.
The manager and I discussed my conversation with the candidate afterward. He asked me what I thought of the candidate. I said, “Well, he knows his technical part and is a hard-working guy.”
The manager looked at me and said, “I do not want hard workers; I want smart workers. I want someone who does the job excellently and then leaves the premises to do something else at home.” He was not joking.
When I terminated my period at ABB and returned to Italy to complete my studies, I was involved in a workshop where the local industry and the university met to discuss the future of electrical machines and drives. My former supervisor, prof. Zigliotto, was with me, too. I remember him talking to one of the CEOs of the participating industry. This CEO told him: “Look, when I receive a CV from a student of your university, I look at the grade the student has received from you. I know that your grades are a summary of the person’s technical skills, personality, and humanity. If the student has low grades in your course, I exclude it immediately even if the other grades are excellent.”
These two examples have permanently shaped my professional life. Needless to say, I have an enormous amount of respect for people who carry on their work in such a way that technical achievements are just a part of a well-rounded, healthy, and happy life, inside and outside the office.
It is sad to see how these simple concepts of life are neglected everywhere. You do not need to go far to see people working 24/7 and being “socially incompetent”… and for what? A name on an article? Glory? But who is giving you glory? Other 24/7 monkeys?
My stand is this:
If you need to work 24/7 to make a career, you are not smart. You are evidently missing the technical skills to do your job and go home.
If you work 24/7 because you have collected too many different tasks, you cannot envision a clear path for your career. Think smart and eliminate unnecessary tasks.
If you work 24/7 because you want to publish more than everyone else, question yourself if your publications have an impact. And I do not mean the number of references from other 24/7 monkey articles. I mean impact as a change in society or industry. Are you contributing to a better future for everyone?
If you work 24/7 because you think that everyone else does it and therefore you should do it too, then you are a 24/7 monkey. Too late.
Every person I recruit goes through an adjustment period when they realize the way I work. I bring the challenge to them immediately from the start:
I want your work to have an impact in society or industry.
Publications will follow your impact. Quality over quantity.
Be smart and have a life outside the office. Take days off and vacations to cool down.
If you reflect on it, these three points are the most challenging job task ever. I ask you to change the world with breakthrough solutions in an 8-hour working day, excluding weekends and vacations.
If you manage to do that, you will have my respect. If you don’t, well, we tried. But at least you are not a 24/7 monkey.
now in July Sweden goes into some form of hibernation and with it KTH as well. July is the month where most Swedish work places take summer vacation, including KTH. The reason to this is likely the climate here. With the long and dark winter behind, now is the time of (moderately) warm weather and long sunny days, with only four hours of night in Stockholm.
All teaching end by the end of May, examinations take place in the first half of June. In the second half of June falls “Midsommar”, the most important celebration in Sweden. People celebrate the summer and life outside. Just have a look yourself:
Midsommar pole, but one of the rings fell down.
The summer is a time to relax and recharge the batteries. While many Swedish families have a summer house in a remote area, others go into the mountainous areas to get a change of tapestry. A big portion of the students use this time to do some work for earning some income for the rest of the year or conduct a paid internship at a company to gain some experience.
With august, people are coming back to work with the new semester starting usually at the end of it, hopefully well rested and full of energy.
Hi everyone! Last week, I paid a visit to the Power Electronics Machines and Drives (PEMD) conference in Nottingham. The East Midlands is an area in which the spirit of Sir Henry Royce of Rolls-Royce is still lingering. The company hosts a big R&D site just outside of Nottingham in Derby, and its engineers constitute a portion of the many industrial delegates who were participating in the conference. The conference is likely my last as a Ph.D. student, and my feeling of belonging to the electrical machines and drives community has definitely grown since I first participated in a similar conference more than four years ago.
Nottingham, the home of Robin Hood.
PEMD 2024 opening at Nottingham University.
After four and half years of research, you leave quite some remaining in your digital libraries. So when it’s time to summarize your work in a thesis and get ready for your post-PhD life, it is necessary to engage in a bit of clean-up and dust-off process.
The first association of this process that came to my mind was an activity known as “döstäda” in Swedish, which literally means “death-clean” in English. Interestingly enough, I found out that there does not really seem to exist any corresponding word for this activity in English. However, the excellent newspaper The Local, which writes about Swedish news and customs in English, describes it very well: “The uniquely Swedish practice of ‘Döstädning’ (death-cleaning) is a method of decluttering based on which objects will be of value to loved ones after your death”, which is pretty much what any doctoral student has to do towards the end of his or her research education.
The thesis at KTH can be written as either a monography or a compilation of the peer-reviewed research papers that you have published. In my case, I have opted for the compilation. Practically, it means that I will weld all the papers in my portfolio together, and the main challenge is to ensure appropriate adhesion between all the bits and pieces. To begin with, why did we study the particular subjects? Using a top-down perspective, problems identified in the industry and within previous research set the ground. My method of ushering the reader through the text then becomes more introspective, which makes quite a lot of sense. Think of it as a natural evolution in research. Once you have your results in place, you need to assess your own work and then improve on it, meaning you first need to identify its weaknesses. This process ties quite well to a maxim, attributed to Sir Henry Royce of Rolls-Royce, that I saw on a wall of the conference center of Nottingham University the other day:
“Strive for perfection in everything you do. Take the best that exists and make it better. When it does not exist, design it.”
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Fig. 1. A block representation of the ADC implementation
