I am investigating MPPT charge controllers modules for wind turbines. I came to the conclusion that my MPPT controller design investigations are more fitted to wind turbine MPPT than solar. I need validation or advice for the 3 points detailed below.
(I've got a 3 phase, permanent magnet generator, unknown rating, at hand. I only know the stator resistance (75 ohm phase to phase 70mH, inductance phase to phase, and number of poles (12), and the weight of the generator, ~3 kg, steel casing)
the cheap BQ24650 module I am planning to buy is a fixed voltage MPPT design.
(that is, we can set the MPPT to a fixed voltage using a potentiometer. That is indeed ok when we know the MPP in the product specs, which is not the case here)
this the product name on aliexpress : "DYKB BQ24650 10A MPPT Solar Panel Controller Lithium Battery Li-Ion LiFePO4 Lead Acid Charging 12V 24V Buck Module Adjustable"
I studied the BQ24650 datasheet and the specific implementation of this module. As is said, there is a potentiometer on a voltage divider to make the MPPSET pin of the chip at 1.2V while the input voltage is set at the solar panel MPP using a lab supply. The second potentiometer allows to set the charge voltage.
I plan to find the MPP on the field for a given stable wind condition by connecting the output of the wind turbine after the rectifier/capacitor/filter stage to a high power wirewound potentiometer and a wattmeter. While changing the resistance, The DC voltage at the max power point on the wattmeter would be the MPP voltage, that i'll use then on the bench power supply to set the MPPT potentiometer of the module. Is that a sound method ?
I'll plan to switch a dump load in parallel to the MPPT module if the voltage exceeds 24V DC at the MPPT input, to protect the MPPT module from over voltage, and as a braking method for the turbine. Load increases -> torque increases -> RPM decreases -> voltage decreases. for that, I plan using a switchable power resistor bank, adding more resistors in parallel if wind speed keep increasing. The goal being not to drop the voltage too much (to allow battery charging and load servicing if the need arises)
For all switching purposes, should I use solid state relays or conventional relays ?
I'll plan to try to make a simulink model as I was adivsed here, I found an MPPT algorithm, but it's based on the perturb and observe method for solar applications. I could not find yet a model using fixed voltage MPPT.