I'm currently designing a MPPT-Controller that should be as universal as possible.
These converters will be used on a solar boat, a university project.
https://www.hs-emden-leer.de/fileadmin/user_upload/pm-Fotos/Bild_Solarbootregatta_1.jpgEach panel will have it's own MPPT tracker in order to mitigate the effects of certain areas being shadowed.
I'd like to make this MPPT very flexible V
in <= V
out and vice versa and support output currents of 5A or even more.
The planned use-case is like this:
Input: up to 26 OCV @ 7A Short circuit, the output of each panel is isolated
Output: up to 60V, to be safe, the battery charge voltage is 50.4V, variable current output. All outputs will be connected in parallel and charge a LiPo battery.
One
STM32 monitors multiple MPPT-channels and adjusts each channel's output voltage to get maximum power out of each panel.
No. of channels: TBD/expandable (let's say ~6)
All channels are connected to one
common (opto-isolated)
bus (I²C for example).
The user can append extra channels to the MPPT-Mainboard, as needed.
Each module has small DIP switches for configuration / addressing.
In order to make the device as flexible as possible, I'd like to implement one buck boost converter per channel. It would get pretty messy to control each channel directly from the STM32.
Not only would I have to route many control signals, the feedback would also need to "travel" quite a long way.
That's why I laid eyes on the LTC2992
https://www.mouser.de/datasheet/2/609/ltc2992-1504204.pdf to measure V
in, I
in, V
out and I
out.
This would give me pretty much all the data I need for the MPPT algorithm.
Unfortunately I wasn't able to find a suitable digitally controllable boost buck converter IC anywhere that would fulfill my requirements.
I found one that uses resistors as feedback and would otherwise be pretty good: LT8390
[url]https://www.analog.com/media/en/technical-documentation/data-sheets/8390fa.pdf]https://www.analog.com/media/en/technical-documentation/data-sheets/8390fa.pdf] [url]https://www.analog.com/media/en/technical-documentation/data-sheets/8390fa.pdf[/url]
Q: Would it be feasible / possible to control the output voltage using a digital pot? So far I only found ones that go up to 32V anyways.
But maybe I'm going in the wrong direction? Each channel would not only be pretty expensive, they'd be pretty complicated too...
Q: Does anyone have suggestions as to how I should design each channel? I really wouldn't want to use a microcontroller on each channel, to maintain one central control board.
This would make accessing telemetry data easier and I think that it would be a bit more elegant.
