Arduino Mega 2560 controlled MPPT charge controller for small wind turbine.

Thread Starter

rodv92

Joined May 23, 2011
7
I am in the process of designing a MPPT controller for a wind turbine.
There are plenty of MPPT boards (with BQ24650 MPPT charge controller ICs) but these are fixed voltage MPPT designs tailored for photovoltaic applications.
So I decided to make a simple DC converter (buck boost design, non inverting with two TTL mosfets IRLZ24N and IRLZ44N)

I was wondering if an arduino Mega was up to the task of generating high frequency PWM to drive the mosfets, compute a perturbe and observe algorithm at the same time, and perform charge program duties for a Lead Acid battery.
It will also have to control a relay to switch a dump load in case of high winds to protect an brake the turbine (based on voltage sensing at the rectifier output)
It will be used most of the time in float voltage with no deep cycling.

I am not sure that a single arduino can do all these tasks without influencing the quality of the switching and the somewhat real time operation, if the arduino is busy doing high frequency duty cycle control, even with clever use of interrupts.

So I was wondering if it was possible to offload the charging task to a dedicated charge module / battery discharge protection connected at the MPPT output stage, and use one arduino for switching and another arduino for perturbe and observe tasks (with a comm link between the two) ?

Any advice welcome.
 
Last edited:

dendad

Joined Feb 20, 2016
3,253
I would think an Arduino will be plenty. Even a Nano. There are a great number already on the net. have you Googled it?
Wind turbines do not change quickly.
 

Thread Starter

rodv92

Joined May 23, 2011
7
I would think an Arduino will be plenty. Even a Nano. There are a great number already on the net. have you Googled it?
Wind turbines do not change quickly.
I have looked at plenty of documentation on switching mode buck boost converters.

For duty cycle selection and component choice and sizing :
https://www.powerelectronicsnews.com/technology/the-dc-dc-boost-converter-power-supply-design-tutorial-section-5-1
http://www.ti.com/lit/an/slva372c/slva372c.pdf

For PWM configuration of arduino in high frequency mode:
https://playground.arduino.cc/Main/TimerPWMCheatsheet/

Seems that the max PWM frequency I can use is 62 Khz in fast PWM and 32 Khz in phase correct mode.
So this is a design constraint.

-I will test all these modes with an oscilloscope. obviously I would have to be sure that the duty cycle does not change abruptly or I will spike the voltage / currents and could fry the circuit.
-I wonder if I can implement some kind of snubber to avoid this problem, and also implement some kind of soft start / soft shutdown.
-I have seen that it is important to add a resistor to ground on the gate driving to discharge the gate when the arduino is powered down.
-I will power the arduino with a 5V supercapacitor between the arduino supply module in case of power disconnect to the arduino to give it time to shutdown gracefully. (How I will detect battery disconnect is another problem I have not figured yet, Depends if the voltage is seen on the input of the arduino power regulator when it is fed by the supercapacitor only)
-The dump load will be connected to a relay on the normally closed side to protect the equipment in case of battery disconnect and arduino power loss.
 
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