MPPT (Maximum Power point Tracking) is a well known and 
basically simple concept which dynamically matches the 
effective resistance of a load to a power source to obtain 
maximum power transfer at any given time.

The path from "basically simple concept" to "practical 
implementation" takes you via the minefield of "riddled with 
patents" and along other entertaining paths.

The system is useful with power sources whose 
characteristics fluctuate widely. Typically wind turbines 
and solar panels are prime candidates. It's basically an 
"electronic automatic gearbox" that uses an energy converter 
to match load and source impedances.

I am about to implement MPPT for a number of solar powered 
products. One simple method is to insert a buck converter 
between the panel and the battery or load and alter the buck 
PWM ratio dynamically to maximise delivered load power at 
any moment. For a battery a good enough result is usually 
obtained by maximising current. One method is to "dither" 
the output signal and note the power slope. If charge 
current increases with increasing load then the load is 
increased until next iteration.

Processor based and discrete implementations exist. 
Processor based allow of great elegance (or stupidity) but 
discrete may be less patent littered.

Question;    Has anyone any practical experience with MPPT 
either as an end user or as a developer?
Any comments, advice, warnings?
Realised gains = ?

Notionally you can get 30%+ extra from a solar system in low 
sun periods and less at high sun rates. Efficiency of your 
converter is obviously a factor. Where the solar panel is 
not initially well matched to its load even greater gains 
may be possible.



        Russell

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