# Questions encountered when I conduct simulation of partial shading / power optimizer

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I am now working on simulation works of PV generation caused by partial shading and testing the corresponding recouped effects of the power optimizer.

Here are some questions:

1. What does "Module-independent shading" mean in the report? Any differences or correlations with the "Module-specific partial shading"?

2. Is it possible to let me know the calculation formulas of the "Module-specific partial shading"? I suppose there must be some relationships between it and percentages marked on panels in the 3D model, but not sure the exact ... Since we want to estimate this parameters based on the real construction, it could be very helpful if this relationship can be explained.

3. Likewise, may I know how to calculate the "Mismatch(configuration/shading)"? Some simple formulas or mathematical explanations will help.

Thanks a lot.

Daniel

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Dear Daniel,

ad 2) There is no simple calculation formula here, I am afraid. What we do is really simulating the irradiance on the module surface, with diffuse and direct shadowing, down to substring level. Then we use an IV-model (two-diodes-model or our own "PVSOL" model) to calculate the I-V characteristics of the module under the given conditions. In addition we also calculate the IV characteristics of the module without shadow and remember this value, so that we can determine the losses due to module-specific partial shading afterwards.

You can find more detail here on our help pages:

ad 3) The configuration or shading mismatch is the difference between the actual output power of an PV array (several modules connected together), not regarding ohmic losses, and the sum of the individual output power values of each module at each moment. When you have inhomogeneous shading on the modules, the resulting IV characteristics of the array may be such that it is not possible to hit the MPP for each module. Instead, the overall array MPP will be chosen, and this point may vary more or less from the per-module MPP.

Hope that helps, kind regards,

Martin

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