windgen.org vawt discussion

crazyguy wrote:

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Question.

When someone says" I 'm running with  mppt mode off and 50% duty cycle."

When on 50% duty cycle is it just the series FET being driven by the PWM, just chopping up the DC and no involvement of the Micro?

What if you just sensed the current or the rpm and drove the series FET that way?    

example   low rpm low current draw = 100% duty cycle, high rpm high current draw 50% duty cycle.

Or how about a wind speed to rpm ratio sensor to adjust the duty cycle?

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 My board was deisnged to be an instrument for research, so it has many modes of operation.  On of them is a fixed duty cycle mode where you just command the processor to hold the duty cycle at some fixed percentage.  The microprocessor is still involved in that it generates the clock, but it doesn't make any adjustments based on inputs in that mode.

You wouldn't want to start with 100% duty cycle beause it might keep the turbine from starting up.

There are many possible circuits and approaches to the problem.  A microcontroller chip with a bunch of A/D inputs, PWM outputs, and other features costs about $5.00.  It doesn't take very many op-amps, resistors, caps, or comparitor chips to quickly add up to the same cost with a lot less capability and flexibility.