Electric flight for individual transport: concepts and proposed solutions

00:00:01: - You're listening to the "PCIM Podcast,"

00:00:03: your podcast on power electronics.

00:00:08: - Hello, everybody, and welcome to the 12th episode

00:00:11: of the "PCIM Podcast," your power electronics podcast,

00:00:14: powered by PCIM.

00:00:16: My name is Marco Jung.

00:00:18: I'm a professor for immobility and electrical infrastructure

00:00:21: at the Bonn-Rhein-Sieg University of Applied Science

00:00:23: at St. Augustine,

00:00:25: as well as head of department converter

00:00:27: and electrical drives at the Fraunhofer Institute

00:00:30: for Energy Economics and Energy System Technology at Kassel.

00:00:35: Both are located in Germany.

00:00:37: Additionally, I'm the chairman of the IEEE joint

00:00:40: IES, IAS, PELS German chapter,

00:00:43: IEEE PELS region eight vice chair, Germany,

00:00:47: and active member of several national

00:00:50: and international communities and committees.

00:00:53: And today, our technical theme is electric flight

00:00:57: for individual transport, concepts and proposed solution.

00:01:01: In this I will discuss with Nina Sorokina

00:01:04: and Wolfgang Bliemetsrieder

00:01:06: from the University of Bundeswehr Munich.

00:01:08: Hello Nina and Wolfgang, how are you?

00:01:12: - Hello, Marco.

00:01:14: We are fine.

00:01:15: Well, I'm fine at least.

00:01:18: I'm eager to record the podcast,

00:01:21: and looking forward to it.

00:01:24: - Great, thank you. Welcome on board.

00:01:27: - Hello, Marco.

00:01:28: Thank you for welcoming and for asking.

00:01:30: I'm also fine and really excited to be here

00:01:32: and to talk about our topic today.

00:01:36: - Great.

00:01:37: So today, it's new for me,

00:01:39: because I have two people on the podcast for the first time.

00:01:43: Nina and Wolfgang, you are both working on your PhD

00:01:47: but before we go into technical details

00:01:49: of your specialized field,

00:01:52: not only I, but also the listeners would like to know

00:01:56: a little bit more about you.

00:01:58: What has your journey been like so far,

00:02:01: and what do you do in your free time?

00:02:05: - My journey so far, I started my technical career

00:02:08: with a classic job training as an electrician.

00:02:11: After that, I was thinking that's not end of the line

00:02:15: and added a secondary school to join university afterwards.

00:02:20: In university then, I go full in

00:02:22: and studied maths and physics

00:02:25: in Ludwig Maximilians University in Munich.

00:02:30: Thereafter, I got the job as a software engineer.

00:02:35: I did classic software for desktop applications,

00:02:40: but I was missing the electrical part

00:02:43: I was doing in my, I started with,

00:02:46: and also I'm very interested in taking it all.

00:02:49: So I had the opportunity to join the

00:02:52: Bundeswehr University in Munich,

00:02:55: the chair of electric energy supply.

00:03:00: So I came here,

00:03:02: and now I have the opportunity to not only do my PhD,

00:03:05: but also work in a project to bring

00:03:09: electric aircraft to the next level.

00:03:12: And about my free time,

00:03:14: I like go hiking and climbing in the mountains.

00:03:19: I have a trip planned to the Puenta

00:03:21: and I'm looking forward to it.

00:03:26: - I have started my education in St. Petersburg

00:03:28: and I have got my bachelor degree at

00:03:31: Technical University of St. Petersburg.

00:03:34: During my master degree,

00:03:36: I have taken part in a double diploma program

00:03:39: between my university

00:03:40: and the Technical University in Ilmenau, Thuringia.

00:03:44: As a result, I have got two master degrees

00:03:46: and wanted to continue my education.

00:03:49: So I have looked for a PhD student

00:03:52: or teacher assistant position in Germany.

00:03:54: As a result I have found job

00:03:57: at the University of Bundeswehr here

00:03:59: and in our project elapsed.

00:04:02: So I have just started to work here.

00:04:04: At my free time I like to read books,

00:04:07: and I'm also a big fan of dancing.

00:04:09: On the weekend, I'm going climbing or bouldering.

00:04:15: - Great, it sounds nice.

00:04:17: Like a good lifestyle.

00:04:22: Electrification of aviation not only enables decarbonization

00:04:26: but also opens up a real alternative in the area

00:04:31: of individual transport, let's say.

00:04:34: Many international research projects

00:04:36: are underway in this area,

00:04:38: but the first products are also appearing on the market.

00:04:43: What current developments are we seeing

00:04:45: in the different flight classes?

00:04:47: Can you give an insight in this?

00:04:52: - So when we are talking about electrical aircraft,

00:04:54: normally we are talking about ultralight aircraft,

00:05:00: about maybe sail planes or motorized sail planes.

00:05:04: And there, we can see several models

00:05:07: that are already available.

00:05:09: So for example, the biggest fair for such a class

00:05:12: of aircraft take place each year in Friedrichshafen,

00:05:16: and you can see it already is at about two halls

00:05:18: are full of different models of electrical planes,

00:05:21: sail planes and maybe drones

00:05:24: that are not only prototypes, but are ready products,

00:05:29: currently at about 250 projects

00:05:33: of electrified planes

00:05:37: developed around the world.

00:05:41: - To add to this maybe,

00:05:42: Nina was talking about ultralight

00:05:44: and glider class of aircrafts.

00:05:46: So there, electric machines are already established

00:05:49: or at least they're the first products coming to the market

00:05:52: and are available.

00:05:54: The next higher class, the regional airliner,

00:05:57: where we are talking around 50 passengers

00:05:59: has also developing undergoing

00:06:01: with concepts of first prototypes in this class,

00:06:05: and they can hit the market in about the next 10 years.

00:06:09: So there's also electrification undergoing

00:06:13: in this next higher level of aircraft.

00:06:18: - And in aviation in particular,

00:06:20: reliability and fail safe operation are paramount.

00:06:25: In many applications, this issue is solved

00:06:27: by radio density in the drive train.

00:06:30: In the podcast, I would like to focus

00:06:33: on flights for everyone,

00:06:34: so that means the ultralight class.

00:06:38: What concepts are currently available

00:06:40: and what we will see in the future?

00:06:45: - Okay, so what currently is available,

00:06:47: the battery is one, fixed devices.

00:06:51: So there are many battery cells

00:06:54: connected in a fixed topology,

00:06:56: and we have one big plus and one big minus pole

00:06:59: where you can throw your energy off the battery.

00:07:04: Additionally, such a battery needs some battery management

00:07:09: so there's also, on top of this,

00:07:12: a battery management system

00:07:15: which can watch individual cells

00:07:17: or parts of the battery and make it safe.

00:07:22: So there's the battery on itself

00:07:25: and then there's on top the battery management

00:07:27: which makes the battery safe as it is possible.

00:07:32: So what we are researching on

00:07:35: is another approach to make this more safe.

00:07:39: What we are doing, we are bringing power electronics

00:07:41: into the battery so that the battery cells are not fixed,

00:07:45: connected, but there are more set switches

00:07:48: in between of them.

00:07:50: So the easiest topology we are working on,

00:07:55: you have the ability to switch each battery cell on and off

00:07:59: and this way, you can adjust the battery voltage

00:08:03: which the battery system provides.

00:08:06: This way, the battery management

00:08:10: is also done in the system itself.

00:08:13: So the battery management system is not on top

00:08:17: of the battery, but it's included in the system.

00:08:22: And with the possibilities to have switches

00:08:25: to regulate the battery,

00:08:29: it's also possible to better predict

00:08:33: the state of the battery.

00:08:35: And this way, it's easier to do the battery management

00:08:39: as you have much more degrees of freedom to interact

00:08:43: with your battery system.

00:08:46: - Wolfgang had said already that

00:08:49: we put power electronics on all the batteries.

00:08:51: And actually, we combine on one platform

00:08:55: the power electronics of the battery management system

00:08:58: and also charging device.

00:09:01: That gives us an opportunity to monitor

00:09:04: state of the batteries just during the whole flight,

00:09:07: and even in times when our aircraft is just in garage,

00:09:13: which means that if we see during our flight

00:09:15: that some of our batteries have over current or over voltage

00:09:20: or maybe they have just too high temperature.

00:09:22: With the help of our technology,

00:09:24: we're able to bypass them,

00:09:26: which means we won't use this batteries anymore

00:09:29: and they won't be dangerous for our aircraft.

00:09:32: We'll still be able to get enough energy from another cell

00:09:35: to land safe,

00:09:36: and that is what we normally mean

00:09:38: when we speak about reliability

00:09:40: and fail safety side of our technology.

00:09:45: Normally we have a fixed battery,

00:09:46: as Wolfgang has said already,

00:09:48: which means that we supply different lines of our motor,

00:09:54: different phrases from the one source.

00:09:56: And in this source, some of battery is failed,

00:10:01: we won't be able anymore to use the whole source.

00:10:04: So only one battery

00:10:06: can lead to the fault in the whole drive train.

00:10:11: In our case,

00:10:12: we can supply different phases from motor,

00:10:15: from separate battery packs.

00:10:17: And even if one phase of our motor won't be active anymore,

00:10:22: it'll be still possible to land,

00:10:25: for example only this two phase

00:10:27: when we are speaking about two phase motor.

00:10:29: In our project actually,

00:10:30: we are developing also a full phase motor

00:10:32: which means that when only one phase

00:10:35: will be deactivated.

00:10:36: Actually, we will still be able

00:10:39: to land really safe.

00:10:43: - So you spoke in the direction of your project,

00:10:46: as I understood, so it's a kind of a new topology,

00:10:50: let's say, in the direction of multi-level.

00:10:53: Can you go a little bit more in technical detail

00:10:57: for the requirements of the power electronic?

00:11:02: - So actually, we are talking not only about multi-level,

00:11:05: we're talking about modular system,

00:11:08: which means that our battery pack has several modules.

00:11:13: Each module has normally 12 cells,

00:11:16: battery cells that are connected in series,

00:11:19: and different number of cells

00:11:22: that are connected in parallel.

00:11:23: So we are able to take maybe only two blocks.

00:11:26: If we want to get maximum voltage of 100 volt

00:11:31: and even take more blocks to get a voltage we need.

00:11:36: Normally we work with 400 volt.

00:11:38: In our case, we don't use semiconductors

00:11:43: that are designed for high voltages

00:11:46: as it is normally used in AC/DC inverters.

00:11:49: We use semiconductors, what's best for us,

00:11:53: that are designed for low voltages at about 20,

00:11:57: maybe 30 volts because actually they are working

00:12:02: only with battery voltage.

00:12:04: And battery voltage is about 4.2 volts only.

00:12:12: - To add to this,

00:12:14: as already said,

00:12:14: we need low voltage MOSFETs,

00:12:17: but at the same time, we have a high count.

00:12:20: So the count is about

00:12:24: several hundred amperes,

00:12:26: so the count project is made for 200 amperes to peak.

00:12:32: So we need MOSFETs which on the one hand

00:12:34: have a really low voltage classification,

00:12:37: but combined with high current.

00:12:40: And to add to this, we of course want low areas on

00:12:44: because on the one side this is of course then

00:12:48: lost energy if we heat up the semiconductors.

00:12:53: But on the other side, it's also the heat,

00:12:57: which is produced there we need to go with of.

00:13:00: So we need a cooling system.

00:13:03: If we use less heat in the power electronics,

00:13:05: we need less heating capability to cool the system.

00:13:09: And yeah, so these special requirements

00:13:14: for the power electronics,

00:13:15: and we hope that if the multilevel system in general

00:13:21: in vehicles will hit the market,

00:13:23: then also that we get more specialized power electronics

00:13:27: for this application.

00:13:30: - It is also important, even if we found a component,

00:13:33: an element of our power electronics

00:13:35: that passed us in the best way

00:13:38: that has perfect characteristics,

00:13:40: we should be sure that this component is suitable

00:13:43: for high reliability applications,

00:13:47: because safety is always on the first place

00:13:50: when we are talking about aircraft.

00:13:55: - Thank you.

00:13:56: We spoke now from hardware, softwares used

00:13:59: and all the software is safety relevant.

00:14:03: Which kind of standards are important?

00:14:05: Which kind of tool chain is useful?

00:14:09: - Okay.

00:14:10: So the standards relevant for this class of airship,

00:14:15: our project is making CS-23 class of airship.

00:14:19: They're also the comes the standards, the DO-178-C

00:14:25: in combination with DO-331.

00:14:28: One is for software development in aviation general

00:14:32: and the DO-331 is an additional document

00:14:37: for model based software development.

00:14:41: Model based software development in general

00:14:43: is highly applicated by the aviation industry

00:14:48: in the recent years.

00:14:50: It's said to be fast and more reliable

00:14:55: than the other approaches.

00:14:56: This is adopted by the industry.

00:15:00: And to talk about the tool chain used

00:15:03: or the tool chain,

00:15:05: there's not the one single tool which can be applied,

00:15:09: but there's always a whole bunch of tools.

00:15:13: So the software is developed

00:15:15: according to the so-called V model.

00:15:17: So on the one side of the V,

00:15:20: you have the development of your software.

00:15:23: On the other side of the V,

00:15:26: comes to the testing of the software.

00:15:28: So each step corresponds to each other.

00:15:31: So high level development is combined

00:15:35: with high level testing.

00:15:36: The tool chain there,

00:15:37: it's desired to have as many steps automated as possible

00:15:41: because for redundant tasks, it's easier to automate them,

00:15:45: also to reduce the risk of failures.

00:15:48: Because if human with repetitive tasks,

00:15:51: errors are more likely.

00:15:53: So to avoid this and also to speed up the process,

00:15:55: automated tasks are desired.

00:15:57: Talk about the tool chain itself,

00:15:59: so there are lots of tools involved,

00:16:02: there's Git involved for version control,

00:16:05: there is Polarion for issue tracking,

00:16:09: there's Jenkins for automated build.

00:16:13: There's Simulink of course

00:16:14: for the development of the models.

00:16:18: This also is mixed up with self design tools.

00:16:22: There's SimPol and mrails

00:16:25: which are developed in Technical University in Munich

00:16:29: together with the University of the Bundeswehr Munich.

00:16:33: So there are a lot of tools,

00:16:35: but as already said,

00:16:37: there's not the one tool which can do all.

00:16:40: And the most critical thing and the most crucial thing

00:16:44: is to build up a tool chain,

00:16:47: where each tool interacts in a correct way with each other.

00:16:51: And those tool chains are also

00:16:53: the main intellectual property of the big aircraft companies

00:16:57: where they have the complete tool chain,

00:17:01: they have the steps where they interact with each other

00:17:06: to get things ready for the certification,

00:17:10: so to build up this is one huge effort to make.

00:17:17: And now I talked a lot about the

00:17:20: software development avionics in general.

00:17:23: For our project, there's the task to develop the software

00:17:26: for the battery system through all the hardware,

00:17:30: the power electronics inside the battery.

00:17:33: We gain a lot of opportunities to interact with the battery

00:17:37: and there is,

00:17:39: we have a combined system.

00:17:41: So we have a modular system,

00:17:43: we have one central battery main controller,

00:17:47: which then interacts with the battery modules,

00:17:50: battery cell controllers.

00:17:52: The task is there to make all the communication

00:17:56: inside the battery and not reintroduce

00:17:58: another single point of failure.

00:18:01: For example, the bus system.

00:18:02: If this fails, all battery modules

00:18:04: does not know of each other,

00:18:06: and are therefore almost out of operation.

00:18:09: So it is a huge task to not reintroduce

00:18:12: a new single point of failure in our modular system.

00:18:15: And most of the effort goes into this task.

00:18:20: - Okay, that sounds nice and really interesting.

00:18:22: So as I understand,

00:18:25: you develop a prototype.

00:18:29: And for me, the question is

00:18:33: which kind of technical readiness level

00:18:35: the prototype will have.

00:18:37: So is it only a demonstration in the lab

00:18:41: or you will implement it in an,

00:18:43: let's say, an aircraft demonstrator?

00:18:47: - So originally our plan was really

00:18:50: to get a real small airplane

00:18:52: and to integrate our developed system in a real aircraft

00:18:56: and to make all possible tests in a real aircraft,

00:19:00: maybe also to fly with it.

00:19:02: Unfortunately, we were not able to get a real plane.

00:19:07: That's why our maximum is

00:19:09: to make all tests in our laboratory

00:19:12: and such a test bench, which is called iron board.

00:19:17: So we'll install full phase model

00:19:21: that we develop in our project

00:19:24: and we'll supply it from our multi-level battery.

00:19:28: But as I have said,

00:19:29: it'll be only laboratory tests, unfortunately.

00:19:33: - That sounds interesting and we are looking forward,

00:19:36: let's see the results.

00:19:38: Hopefully, you will write a paper or publication

00:19:41: and that we have a few insights

00:19:43: more and more in the future.

00:19:45: Thanks, Nina and Wolfgang.

00:19:48: - Thank you, Marco.

00:19:49: - Thank you.

00:19:50: - To all the listeners, wherever you might be,

00:19:53: thank you very much for listening.

00:19:55: We hope you have enjoyed today's episode

00:19:57: and gained some valuable insights.

00:20:00: Make sure to subscribe to our podcast,

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00:20:07: If you would like to share your feedback with us,

00:20:09: please do so via an email to pcim@mesago.com.

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00:20:23: Until then, have a great time.

00:20:26: - We hope you enjoyed this edition of the PCIM podcast.

00:20:29: Together, we'll excel in power electronics.