Solar Buck-Boost Converter Project

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Solar Buck-Boost Converter Project

Post by dangraham » Sun Sep 20, 2020 8:24 am

Hi, I am Dan, I have been working in I.T. and electronics for a while. I have always been interested in using micro controllers and a few years back created some small projects with ATmega chips. I found the coding was a very steep learning curve and could not dedicate enough time to progress. Fast Forward a few years, now I have recently been working on a number of projects where I am based in Thailand, including off-grid solar, marine power and solar systems, electric propulsion etc. A lot of the Chinese equipment here fails or does not operate correctly, for example a lithium cell charger that when CC.CV completes it then allows the cell voltage to rise to Vin @ 19V! So I recently had a look at getting back into micro controllers for building some devices needed. I bought a few ESP8266 boards and started learning micropython, Wow, I love python so much, it is a lot easier to follow than before, although I still have a lot to learn I have built a lot of the introductory projects to familiarise myself and everything has been going well, I have also enrolled onto a professional Python course. Now I need to scope out my first real project that I want to achieve and try to build a DC buck-boost converter for the solar power system on the boat.

The electrical part I am not so concerned with, I have most of the components and have started to build a manually operated converter to test the electrical performance. What I really want now is to use the ESP8266 as the brain for my converter and eventually be able to access the data via the web server.

Below is an overview of the project & required control that I would like to achieve:

Solar input from 8*375W solar panels (200V@21A Max)
BB converter to operate when input V reaches a defined value, and operate at MPPT defined values.
BB converter to output power to a maximum of 150V (my battery bank is 40x 180Ah LifePo4 and BMS will cut at 150V)
Non priority, to access data via web browser (input V, input A, output V, output A, output W, daily KW/h)

I am obviously still in the initial design stages of this project and there are a number of issues that I am trying to workout how to achieve. Being able to discuss these here on the forum will be very beneficial to me and hopefully others that may benefit from such a project. The main objectives I would like to discuss are as follows, I will need software and hardware solutions to achieve these.

Measuring input voltages and current (50V-200V 1A-21A Range)
Measuring output voltages and current (130V-150V 1A-25A Range)
Configuring input start voltage (Solar voltage to start PWM operation, also to start daily harvest data)
Calculating and storing daily power harvest (I have a lot of coding to learn)
Configuring max output voltage so I don't over charge batteries

I also need advice on acquisition an driving of high voltages and power devices from 3.3V logic, i.e. what current sensors, voltage dividers to use and if there are off the shelf components that will make things easier for interfacing with the controller, opto couplers etc. The ESP8266 may not be suitable for the end project due to some limitations, so may need to explore this further.

I know this is probably going to be a complex project but it always appears to be difficult to find information from the beginner type pwm led dimmer to something more complex. Any advice you can offer would be greatly appreciated and I will use this thread to keep my project updated as I proceed. I am not a seasoned coder so advice on how to layout the code requirements on a higher functional level will then allow me to learn the lower level blocks as needed.

Anyone interested in the basics of the buck boost converter this is a good explanation video

Thank you,

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Re: Solar Buck-Boost Converter Project

Post by davef » Sun Sep 20, 2020 10:19 am

Sent you a PM suggesting some other forums.

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Re: Solar Buck-Boost Converter Project

Post by pythoncoder » Sun Sep 20, 2020 12:04 pm

This project evidently requires considerable expertise in electronics - as @davef says, best accessed in other forums.

I would point out that the ESP8266 is not ideally suited to 24/7 operation. It does occasionally crash. Options are to use a software watchdog timer - in which case you need to think through the electrical consequences of its halting and rebooting. Alternatively use hardware which can run 24/7 such as a Pyboard D.
Peter Hinch

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