Maybe if you skip the low part of the wind curve it is possible to use a square function instead. If that is true than perhaps it's possible to use a square root function on the current signal going to the batteries and than use the speed signal as it is as feed forward to the PWM circuit.
The goal is not to lower cut in. It's more like getting a higher cut in. The stator was made for 48 V but I want to use it for 12 V.[ Parent ]
That is that way I do it. I take speed and use a multiplier to get a voltage proportional to speed squared. I assume battery volts is constant so output power is proportional to current.
I use a servo loop to track the current to the speed squared reference so that my output power tracks the square of the speed.
I also find that my props work best with falling tsr with wind speed but other props may not behave the same way. I am inclined to think that most as constructed here do behave that way and it is one of the reasons why the direct matching scheme works better than it otherwise would. In any case props are very tolerant and any reasonable match to the ideal loading will be so much better than no attempt so absolute perfection in the tracking is not very necessary.
Flux.[ Parent ]
I don't understand what you mean by servo loop. Do you have some additional circuitry between the current feedback and the PWM?[ Parent ]
This way the current is proportional to the reference signal.
Interesting things to watch for are that if the "speed squared" signal limits then the mill goes to constant current ( run away and avoid it). If the current signal limits then it aims for constant speed and that is nice to hold the things under control and induce a measure of stall at the furling point.
For those trying to follow this but not completely understanding, it is no way a mppt controller. It is a controller to force an alternator power out to follow speed cubed at the input. It has to be set up to match a given machine. The set up is not difficult, you have to set the pwm at cut in ( error amplifier offset) and set the current gain of the current amplifier to get the correct pwm at full load.
Flux[ Parent ]
Recently posted on Solar MPPT controller design. Function ended up maxing only current. Controller Cycle time on solar panel could be relatively fast, as in fraction of a second.
With wind maxing out only current should work also. Have not spent much time on the thinking. Realizing the delay loop is much longer than solar. At Lower power, longer control loop delays.
Since your speed is based on loading I wold skip it. Maximize on current going into the battery. Forget everything else (as a MPPT function, pay attention to other things for battery charging controller:).
My back ground is Micro, so I would recommend using intelligence in a micro to control this wind MPPT.
Have fun, Scott.[ Parent ]
Now I'm thinking of using a digital potentiometer to deal with the delay. It could go up or down almost like a regulator with an integrating search. [ Parent ]
Not surprised you say that. After the fact the software is much easier to change vs hardware. Intelligence in micro is superior to analog logic. Everything has a price. Micro is typically cheaper than analog logic.
In the mid 70's fist used a micro. This summer for a project selected a "New one". Figured it would take two weeks to learn and write the page of code. No biggie. A month later still learning, little writing. Documentation is honorable!-( 6 weeks coding completed. Wow, way off on that one.
