DC/DC with MPPT for solar panels

[jderson]

Type "sun tracking" into the search tool.

[iw2fvo]

Type "sun tracking" into the search tool.

I am really searching for a basic code that allows to maintain the max power output from a PV. So the V*I ( pv parameters) is to be maintained to the max . I plan to play with the duty cycle of the DC DC in order to "track" that max power out from the PV.
I do not want to track the sun position during the day by rotating the PV.

Thanks.
Ambrogio

[ScaleRobotics]

Pic Assembly code example - scroll down page to MPPT-4.2:
http://www.drgw.net/workshop/MPPT/mppt.html

http://www.electro-tech-online.com/m...-picbasic.html C code

http://electronicdesign.com/Articles...ArticleID=6262 LTC1149

http://www.solarbuildings.ca/c/sbn/f...for%20MPPT.pdf nice paper on subject

Hopefully one of these will help. Keep us posted on your project. I have an interest, as I have a couple C-40 charge controllers for this system. MPPT would be nice!

[ScaleRobotics]

One more link http://www.wseas.us/e-library/transa...008/27-545.pdf

And some good information, if you look hard enough here. With some C examples in the .rar files https://sites.google.com/a/l2na.com/...me/attachments

[iw2fvo]

Thanks for the links you have sent to me.
It is a lot to read and very interesting.
I would like to submit a concept for having reply and discussion:
All the documentation talks about the peaking of the PV power output by control the V*I product at its maximum possible level.
What do you think if the program will adjust the dc_dc duty cycle just to peak the battery current at max level ? The target is to inject the max possible current in the battery for recharging and so, why do not try to get it at its maximum ?
Thanks
Ambrogio

[ScaleRobotics]

Hello iw2fvo,

I have not really read the documentation I linked yet, (really just browsed it). You might be saying the same thing, but it is my understanding that MPPT senses battery voltage, calculates what charging voltage is required, based on that, converts PV voltage and current to match what the battery needs for charging. This would be the highest current available to charge the batteries.

For instance,
Assume your battery is low, at around 11.5 volts. A MPPT takes PV output at 16.9 volts at 7.1 amps and converts it, so that what the battery gets is no longer 7.1 amps at 12.5 volts, (which standard charge controllers will do) but 9.6 amps at about 12.5 volts using MPPT. If you bring the amps up higher, you drop the voltage, and if you drop the voltage much lower, you won't be able to have the current flow into the batteries.

Here is one last link that explains in very general terms how MPPT works. It is not great, but I have not found a better general explanation. http://www.solar-electric.com/charge_controls/mppt.htm

[iw2fvo]

Hi Scalerobotics,

That is a very good site. Thanks.
I do have to learn a lot of things ! and then I have to make a breadboard and I have start to write the code for the PIC micro.
Thanks again
Ambrogio
IW2FVO

[ScaleRobotics]

I do have to learn a lot of things !

Me too. But that's what this forum is all about! MPPT is pretty complex and it's use is specialized. That is, the main use would seem to be power generation such as Photovoltaics, and wind power. Things that give varying voltages, where you want to use every extra mA of power. Most articles seem to be within research, and engineering colleges, rather than people doing such things in their garrage. But I am sure more people are doing just that. It is somewhat a new technology, so within a year or two, there will be others documenting more on how its done, I am sure.

I did a search on open source mppt, and a pretty detailed project, but not much explanation is given here: http://solarcar.stanford.edu/blog/news/455 go to the download section. You may be able to ask Sasha about a paper on the MPPT portion of the solar car project. If you get any more information, please share it. It looks like they plan to release more information later on the subject.

Pretty cool pictures of the car at the very bottom of the link.