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MPPT scanning algorithm test

A project log for Micro generator platform for water and wind energy

Open low power motor controller platform for generator applications

Mitja BreznikMitja Breznik 05/05/2019 at 09:240 Comments

Simplest way for me to test different energy conversion functionalities is to build a back-to-back setup. I have coupled two brushless outrunners enclosed in a plexiglass tube for protection. It is not the optimum solution for long term testing, due to heat build-up, but it will suffice for SW testing.

Instead of connecting the generator side of the system to the wind or water turbine I programmed a simple linear speed/torque curve to one of the motors:

set_speed = no_load_speed - ramp_coefficient*motor_current

Parameters of the load curve can be adjusted with a PC GUI. Linear load curve should have a maximum power point at no_load_speed/2. Wind or water turbines tend to have higher order load curves but this simple curve is sufficient for first tests.

I have programmed a simple MPPT algorithm, that measures the generating power over the whole pre-programmed range and then settles at the MPP:
All parameters can be set of the PC GUI application with the modified VESC Tool:
Number of different parameters should ensure that SW could be adapted to a number of different generator applications.

Here is a screenshot of the motor currents/speed during the first MPPT test:

In order to use this algorithm to charge the battery there is feature added which gradually reduces the charging current until reaching full battery voltage.

I will perform the next MPPT test by connecting the generator side to the LiPo battery pack and test the full battery derating function.

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