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I have 6kw PV panel, in case of partial shading it's capacity reduces to 3kw. But, the MPPT tracker I designed it specifically for that 6kw rating, now because of partial shading the same MPPT tracker is not extracting full power from the panel, it's extracting about 1/3rd of its peak 3kw rating, and it's not even a local peak to blame it on the algorithm, it's less than the local peak power that's being extracted. So, I think it's the problem of the dc-dc converter inside the mppt tracker block? Can y'all share some insight?

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  • \$\begingroup\$ What makes you think the panel power is merely halved during partial shading? Actual measurements? \$\endgroup\$
    – user16324
    Apr 25, 2022 at 11:45
  • \$\begingroup\$ @user_1818839 yes \$\endgroup\$
    – Macroeng
    Apr 25, 2022 at 11:58
  • \$\begingroup\$ @fraxinus said, "All-serial with no reverse diodes is...bad." If anybody comes here wondering why it's bad: A PV cell acts like a light-dependent current source in parallel with a diode that shunts the current when the external circuit provides no more favorable path. electronics.stackexchange.com/q/236898/69405 The only "forward" path for current in a series string of cells is through all of the current sources. Shading any one cell limits the current for the entire string. Adding a parallel diode in the opposite direction provides a path for current to bypass the shaded cell. \$\endgroup\$ Apr 25, 2022 at 14:21

2 Answers 2

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  1. A lot of MPPT controllers have a voltage/current range where they perform optimally and a much wider range where they perform "somewhat".

You may be operating in this wider range when the array is partially shaded.

  1. How exactly your panel array is wired? Do your panels have reverse diodes? All-serial with no reverse diodes is especially bad when partially shaded.

  2. Do your panels trace the Sun or are stationary? How much do you expect at the time of the day when they are shaded, should there be no shade?

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If your MPPT controller can control the load so it matches the rise in PV output impedance when shaded then your energy conversion will be optimal. This demands you regulate PV voltage with solar power changes and you must control the charger to design its input impedance to be match that of the PV or higher if the demand for power changes. This follows the rules of energy conversion and maximal power transfer theorem.

How you do this is your choice and how you measured and verified your TBD design is unknown.

e.g. Pulsed Voc/Isc=Zout or hunt for lowest delta V/I or ...

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