MPPT Solar Controller - PIC based

Thread Starter

StephanG

Joined May 21, 2017
22
Hi,
I need help for my MPPT (Maximum Power Point Tracking) Solar Controller project.
The MPPT Controller should be PIC MCU based.
I need help in the choosing the circuit (design) for the DC-DC converter and programing the PIC.
I want the PIC to program in mikroC or CCS C.
I attached an block schematic of the controller.
*Own work.
mppt_block_00.png mppt_block_02.png
 

Kermit2

Joined Feb 5, 2010
4,162
It's a simple math problem at the center of the tracker

Volts X amps = watts
You repeatedly check those two values of the solar panels.
If it falls below a programmed set point you change PWM duty cycle so wattage delivered stays near max.
To much current draw and the solar panel voltage collapses quickly to zero. When the load wants less power the array voltage will rise. This condition is much harder to optimize with MPPT.
A discharged battery that can pull more amps than the array can provide is the prime candidate for MPPT. After the demand for current drops lower than the panels max output the DC - DC converter efficiency becomes most important.
 

crutschow

Joined Mar 14, 2008
34,281
If the solar panel voltage is always greater than the battery voltage, a simple buck converter configuration is the easiest and most efficient way to do the converter.

The MPPT algorithm constantly slightly changes the converter duty-cycle up and then down, and calculates the input power from the input voltage and current for each duty-cycle.
It then moves the duty-cycle in the direction of the maximum power and again slight adjusts the duty-cycle around this point.
It continually keeps doing this and adjusting the duty cycle so that the system is operating at the maximum power point on the input.
This point will change, of course, with the amount of solar reaching the panel.

One approach to do this in a Micro is with a series of If-Then-Else statements using a Fuzzy Logic approach.

You also need to monitor the battery voltage and reduce the duty-cycle when the battery reaches its charged voltage.

Why are you powering the MCU from the grid?
Can't you just power it from the battery?
 
Last edited:

Thread Starter

StephanG

Joined May 21, 2017
22
If the solar panel voltage is always greater than the battery voltage, a simple buck converter configuration is the easiest and most efficient way to do the converter.

The MPPT algorithm constantly slightly changes the converter duty-cycle up and then down, and calculates the input power from the input voltage and current for each duty-cycle.
It then moves the duty-cycle in the direction of the maximum power and again slight adjusts the duty-cycle around this point.
It continually keeps doing this and adjusting the duty cycle so that the system is operating at the maximum power point on the input.
This point will change, of course, with the amount of solar reaching the panel.

One approach to do this in a Micro is with a series of If-Then-Else statements using a Fuzzy Logic approach.

You also need to monitor the battery voltage and reduce the duty-cycle when the battery reaches its charged voltage.

Why are you powering the MCU from the grid?
Can't you just power it from the battery?
The powering from grid is used when the battery is empty. This should be switched automatically.
 

Thread Starter

StephanG

Joined May 21, 2017
22
I think to use an buck-boost, because when there is less sun the voltage of the PV falls less then the battery voltage.
 

crutschow

Joined Mar 14, 2008
34,281
The powering from grid is used when the battery is empty. This should be switched automatically.
You should never run the battery down to the point where it couldn't provide the small amount of power the electronics takes.
I think to use an buck-boost, because when there is less sun the voltage of the PV falls less then the battery voltage.
Okay.
Just be aware that they are significantly more complicated than a simple buck regulator.
 

Thread Starter

StephanG

Joined May 21, 2017
22
I thought to make something like this.
And combination of two DC-DC converters.
The Q1 is controlled with PWM of the MCU, the duty cycle is set according the maximum power point of the PV.
The duty cycle of PWM signal to Q2 is set to make 12V for the battery.
I don't have tested this yet.
If somebody has an opinion about this design, feel free to wrote.

https://easyeda.com/export_352ef705...idthIncrease=0&version=4.5.2&_t=1495489898188

 

Thread Starter

StephanG

Joined May 21, 2017
22
You should never run the battery down to the point where it couldn't provide the small amount of power the electronics takes.
Okay.
Just be aware that they are significantly more complicated than a simple buck regulator.
I also want to make the solar controlled to be used without battery, for example to be directly connected to an inverter.
 

IMP002017

Joined Jan 28, 2017
192
I follow a person on Youtube that has a lot to do with Boost and Buck with many things related to Solar and might be something you would want to search though to see if there is something there that might help you. or give you an idea on what may and may not work.

He does a load of Videos and some are things that he buys from Banggood or ebay. Most items are provided to him I think over a Donation part of the channel but just because you watch them you don't have to pay to watch like some other people have moved on to.
This link is where he plays with some Super Caps that he wants to use with his Solar systems.


I am not sure if that is helpful or not.I have had many videos and didn't get far enough back in my history to find the ones on the systems he uses. He even has designed a battery charger system that others have taken the design from and even built PCB cloanes from that he has Open source.

James
 

MrAl

Joined Jun 17, 2014
11,389
Hi,

You should show the specs of your solar array. That helps determine the type of converter to use.
Most arrays used with 12v batteries will put out around 20v or so open circuit. Most likely you can use a buck because if the voltage goes down too low it means there is very little insolation so it wont do much good to switch to a boost mode anyway. You can check your solar panel specs though.
 
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