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Suppose I have a 75w solar panel. At full sun shine it is giving 17 volts 4.41 Amperes 17 × 4.41 = 75 watt. My MPPT controller converts it to 12 volts and 6.25 Amperes 12 × 6.25 = 75 watt. I know that MPPT is droping 17v to 12 by setting the switching PWM duty cycle.

The thing I can't understand is how the MPPT is compensating the voltage in current? How it is making 6.25 Amperes when there is only 4.41 Amperes available? It will be very helpful if any one can explain it using using the buck converter circuit.

I searched whole Internet but I could not find any answer to this question. Or maybe there are good answers but I am unable to understand them.

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    \$\begingroup\$ Can you please take the time to properly structure your question? A "…" doesn't add to readability, whereas a paragraph (add an empty line between sentences where there is a logical break) would help. It's pretty annoying to search for your real question in your unstructured block of text \$\endgroup\$ – Marcus Müller Dec 14 '16 at 17:46
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    \$\begingroup\$ And don't claim "I searched the whole internet". That's several petabyte of data. No human can do that in their lifetime. You just didn't find something; that's no shame, but not worth a mention, either. Instead, explain what you've understood so far, so that we don't have to start an answer by explaining everything, but can focus on what you did not understand. \$\endgroup\$ – Marcus Müller Dec 14 '16 at 17:48
  • \$\begingroup\$ You have already answered your question 17V * 4.41A = 12V * 6.25A. And yes a buck converter does it all. \$\endgroup\$ – Marko Buršič Dec 14 '16 at 19:44
  • \$\begingroup\$ In a buck converter, energy is stored in the inductor when current flows through it. During the part of the switching cycle when the high side FET is off, current continues to flow as the energy in the inductor is transferred to the load. But the current in this case flows up from ground, through the synchronous switch or diode, through the inductor, to the load. So the current delivered to the load is greater than the current delivered by the source. \$\endgroup\$ – mkeith Dec 15 '16 at 8:27
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You need to familiarize yourself with the operation of PV cells. Here is a plot of the typical PV curves: pv curves You can see that maximum power occurs when the current is not at its maximum value. The point of MPPT is to obtain the maximum power from the PV cell, i.e. maximize the efficiency. This is achieved by driving the PV cell at the MPP, either by current or voltage control. That is where the extra power is coming from. Instead of being used for something unrelated to your purposes, it gets converted into electrical power.

As for the current, it follows the curves. The current is not conserved in the PV system. As you can see from the plot, the current can take a multitude of values.

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You forgot an important thing: the PV is normally connected with a DCDC converter. That is why you can use the duty cycle to control it.

For 17V to 12V, you need a buck converter (buck-boost also works!).

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