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Author Topic: Building a Microcontroller based MPPT  (Read 2304 times)
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szabi80
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« on: September 14, 2015, 09:00:22 21:00 »

Hi there!

I spent some time reading and searching through the forum so excuse me if I missed a place where my topic would fit.

I'm working on a MPPT project  which is still in it's planning phase.
One of the most important part of an MPPT is the buck-boost converter which I wish plan first and probably also build a prototype of it to run some tests.

As for now I wish to discuss about building the best possible BB conv. for my project, selecting the right mosfet drivers, and mosfets etc for it.

The Idea is to build an MPPT of approx. 100-120W working with different solar arrays and battery array up to 24V.
I wish to build a system which can work with a wide range of arrays which may feed up to 40-60V, but should also work with lover voltage arrays providing voltages below 20V, so highest currents may reach 6-7A.



Any ideas or ready made reference designs are welcome on this topic!


Thanks!
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fpgaguy
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« Reply #1 on: September 14, 2015, 10:15:12 22:15 »

I think this micro based dcdc design

http://www.microchip.com/DevelopmentTools/ProductDetails.aspx?PartNO=Quarter-Brick-DC/DC-Converter
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Wizpic
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« Reply #2 on: September 14, 2015, 10:19:58 22:19 »

Here are some links I found, When I was planning not tried them yet but it should give you some good ideas and should not be to hard to alter, I like the look of the way the driver is set up, If I was to do it I would use and external ADC like the ADS1115 (16bit) but this is using Arduino and not picmicro. 6-7amps should not be to much trouble, There are plenty of designs based on arduino on the web. A chap called Tim Nolan has covered quite a lot on this he has a youtube blog right from the start to the end. do a search on him


[url]http://mjlorton.com/forum/index.php?topic=68.0][/http://coder-tronics.com/c2000-solar-mppt-tutorial-pt1/url]
[url]http://mjlorton.com/forum/index.php?topic=68.0

[url][/http://www.freechargecontroller.org/url]

Would be interesting to see how you go with this

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micropcb
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« Reply #3 on: September 15, 2015, 10:23:32 10:23 »

A few years ago I happened to be working on a MPPT based solar charge controller design.
The following articles from Silicon Chip were quite useful. You may find them useful too.

http://archive.siliconchip.com.au/cms/A_112794/article.html
http://archive.siliconchip.com.au/cms/A_112335/article.html

Best regards.
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Droneman1982
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« Reply #4 on: September 16, 2015, 02:14:09 14:14 »

I also design and built my own version of a sinchronous buck converter directly driven by the PWM (125KHz) of a PIC16F88. It was able to attain an efficiency of 95+% charge e SLA battery and keep it at trickle charge (13.5V) once topped. The software was written in picbasic.

If you are interested I can share it

here's a video:

https://www.youtube.com/watch?v=udcfKwoB2Gk

PS: the schottly diode is in parallel to a N-type mosfet . The efficiency is 94% because of the power consumptin of the LCD display. It is used only for throubleshooting, when not used it gets disconnected and a jumper deactivates the software routines controlling it
« Last Edit: September 16, 2015, 02:17:10 14:17 by Droneman1982 » Logged
wellnerson1
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« Reply #5 on: September 16, 2015, 05:13:08 17:13 »

See the research article from the Solar Energy Journal
http://www.sciencedirect.com/science/article/pii/S0038092X14000711
This research paper contains real time circuit to implement MPPT
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kreutz
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« Reply #6 on: September 17, 2015, 12:14:09 00:14 »

You can also take a look at the following link for ideas: https://hackaday.io/project/4613-arduino-mppt-solar-charge-controller
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omelette
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« Reply #7 on: September 22, 2015, 10:34:25 10:34 »

I have just ordered one of these - http://www.ebay.com/itm/171709830797?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT.  They are allegedly 95%+ efficient with up to 130W output, most of the hard design work has been done for you,  all you've got left to do is interface it to a MCU controller.  Downside is that it's only good up to 32V.
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xeontory
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« Reply #8 on: October 05, 2015, 08:08:17 08:08 »

Have you considered a small ferrite core transformer with Flyback Converter topology in 100-120W range? You can also try with "Non-isolated Ćuk converter" or a "SEPIC converter" topology for DC-DC up or down conversion. Also, If you can't find schottky diodes in that voltage range, you can use UF4007 or similar series diodes. To meet up high current requirement you can experiment paralleling several diodes with a very small series resistor. Suitable diodes like MUR860 or similar will have low loss up to 8A. Try to get Power MOSFETs with low Rds on resistance. To turn them fully ON /OFF, you can make your own MOSFET driver from two BJTs, use dedicated driver ICs or use MOSFETs that can be driven from 5V output directly. Every time the latter one worked for me. 
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sadman
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« Reply #9 on: October 09, 2015, 09:12:09 09:12 »

I also design and built my own version of a sinchronous buck converter directly driven by the PWM (125KHz) of a PIC16F88. It was able to attain an efficiency of 95+% charge e SLA battery and keep it at trickle charge (13.5V) once topped. The software was written in picbasic.

If you are interested I can share it

here's a video:

https://www.youtube.com/watch?v=udcfKwoB2Gk

PS: the schottly diode is in parallel to a N-type mosfet . The efficiency is 94% because of the power consumptin of the LCD display. It is used only for throubleshooting, when not used it gets disconnected and a jumper deactivates the software routines controlling it

can you please share the project
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Droneman1982
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« Reply #10 on: October 12, 2015, 08:50:22 20:50 »

Yeah. I'm in the office now. I will search for the drawings and picbasic pro code once at home


Posted on: October 09, 2015, 03:24:49 15:24 - Automerged

Heres the schematic files and the bas and hex file for the PIC16F88 microcontroller (remember to set the configuration word to flag the CCP1 device on RB3 port)

Any low-resistance Nchannel mosfet is good for the project (i used surface mount transistors).
I used a half bridge driver to make the buck converter sinchronous attaining efficiences up to 95% with the LCD module sucking some power.

If you want to scale it up you have to change mosfets, shunts, and software constants.
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Wizpic
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« Reply #11 on: October 12, 2015, 09:45:14 21:45 »

Very interesting project, I shall have a read through the code and have a look at the schematic's and PCB
I've seen plenty of Arduino MPPT versions but not many in basic

Plus it's a shame that szabi80 starred the topic and has only made one post, But at least there is plenty of interest from others
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Droneman1982
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« Reply #12 on: October 13, 2015, 10:26:58 10:26 »

I forgot to mention that the LCD module is only for troubleshooting, and once removed the software part controlling it can be disabled by removing a jumper
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sadman
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« Reply #13 on: October 13, 2015, 12:33:48 12:33 »

Yeah. I'm in the office now. I will search for the drawings and picbasic pro code once at home


Posted on: October 09, 2015, 03:24:49 15:24 - Automerged

Heres the schematic files and the bas and hex file for the PIC16F88 microcontroller (remember to set the configuration word to flag the CCP1 device on RB3 port)

Any low-resistance Nchannel mosfet is good for the project (i used surface mount transistors).
I used a half bridge driver to make the buck converter sinchronous attaining efficiences up to 95% with the LCD module sucking some power.

If you want to scale it up you have to change mosfets, shunts, and software constants.


many thanks for such a nice project i have same based on 16F88 by silicon chip but this based on basic language
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szabi80
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« Reply #14 on: November 09, 2015, 07:49:29 19:49 »

Hi Guys!

Thanks for all you effort keeping me updated with ideas and sorry for my inactive period but I'm really busy nowadays :-(
I know it is not an excuse but the main reason I did not reply to any of you is because I simply haven't received any e-mail notification so I thought my topic has no interest and not much time to login and follow up every day.

However meanwhile I spent some hours to plan my first design. I decided to build a BB converter prototype first an only later to interface it with a micro. The idea was to use 2 x LTC4444-5 as the top and bottom drivers for and LTC6102 for current monitor.

My LTC6102 proto board proved that the it is incredible accurate even in a really wide range (see attached pictures) so I definitely want to use them in my project.

At the other hand it looks like the idea using the LTC4444-5 was not as good as my idea regarding the current measurement :-( I have difficulties with this chip since it looks like it can not be driven in a continuous full duty mode which drives me crazy. For example in a boost mode when the buck stage's top mosfet should be permanently on it can not be achieved with this chip so now I probably will re design my board and try using IR2302's.

Hopefully I will have some more time keeping track of this thread and keep you updated guys.
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9thwonder
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« Reply #15 on: November 23, 2015, 06:40:12 18:40 »

Dear Dronman1982 , Kindly Mention which software opens the schematic and pcb. Thanks for sharing Nice MPPT project.
 
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Checksum8
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« Reply #16 on: November 23, 2015, 07:27:16 19:27 »

9th
I was able to open it with Eagle light
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Qiaozhi
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« Reply #17 on: January 27, 2016, 11:07:31 23:07 »

Hi Guys!

Thanks for all you effort keeping me updated with ideas and sorry for my inactive period but I'm really busy nowadays :-(
I know it is not an excuse but the main reason I did not reply to any of you is because I simply haven't received any e-mail notification so I thought my topic has no interest and not much time to login and follow up every day.

However meanwhile I spent some hours to plan my first design. I decided to build a BB converter prototype first an only later to interface it with a micro. The idea was to use 2 x LTC4444-5 as the top and bottom drivers for and LTC6102 for current monitor.

My LTC6102 proto board proved that the it is incredible accurate even in a really wide range (see attached pictures) so I definitely want to use them in my project.

At the other hand it looks like the idea using the LTC4444-5 was not as good as my idea regarding the current measurement :-( I have difficulties with this chip since it looks like it can not be driven in a continuous full duty mode which drives me crazy. For example in a boost mode when the buck stage's top mosfet should be permanently on it can not be achieved with this chip so now I probably will re design my board and try using IR2302's.

Hopefully I will have some more time keeping track of this thread and keep you updated guys.
.
You don't need to use any special ICs to create a simple MPPT solar charger. Unfortunately I cannot share the design with you, but (a few years ago) I successfully designed and built a small system with a boost-converter and an efficient tracking capability, based on a 16F877A with an LCD. The efficiency was at least 98%. It was able to charge both AGM and Lithium Phosphate.

There are a number of tracking methods you can use such as Perturb and Observe (P&O), Incremental Conductance (IC) and Constant Voltage (CV). Try googling maximum power point tracking methods. There are lots of articles and papers to read.
It's a very interesting subject.  Cool
« Last Edit: January 27, 2016, 11:10:00 23:10 by Qiaozhi » Logged
Sushilogic
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« Reply #18 on: January 29, 2016, 04:29:28 04:29 »

There is a design in the February 2016 Silicon Chip magazine - may be worth a look. Its in the E-Books section here : http://www.sonsivri.to/forum/index.php?topic=19993.msg176931#new
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Qiaozhi
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« Reply #19 on: January 29, 2016, 10:31:10 10:31 »

There is a design in the February 2016 Silicon Chip magazine - may be worth a look. Its in the E-Books section here : http://www.sonsivri.to/forum/index.php?topic=19993.msg176931#new

A follow-up article is scheduled in next month's magazine.
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