Electrical behaviour

[klerindias]

I made some simulation and results for me seems not correct.

Result for I/V curve:

http://img194.imageshack.us/img194/9451/pvsysterror1.jpg

and here result for P/V curve:

http://img23.imageshack.us/img23/4545/pvsysterror2.jpg

[sebstein]

Hello,

what in your optinion is not correct in this case? The shape of the reverse I-V-curve is defined by the "Secondary parameters".

In your case a module WITHOUT bypass diodes has been defined, thats why it look different than common I-V-curves with partial shading.

[klerindias]

Why we have weird values: 172W 269C?

Here is real module with removed bypass diodes and shaded 1 cell, I/V curve:

http://img585.imageshack.us/img585/6607/1cellshadednodiodes.jpg

[André Mermoud]

I don't know how you obtained this curve.

But of course, it is strongly dependent on the reverse charactersitics of the shaded cell.

When I tried to establish experimentally this little (very rough) quadratic model by forcing a fixed reverse voltage to the cell, the measurements were difficult as when heating up, the cell's conductance increased with the temperature, therefore dramatically increasing the current and so on up to the destruction if I did not disconnect within some few seconds. It is probable that your shaded cell's voltage saturates at around -10 V or -11V, and this will indeed result in your observed curve.

However this tool is a pedagogical one (for explaining the phenomenon). Fortunately the exact behaviour in this region doesn't arise in the real life, due to the protecting diodes. Otherwise you would often have cell's destructions due to Hot-spots !

[LashiN]

I had the same problem here, but my question not in the strange shape of the curve.

Am asking about what is controlling the shaded cell behavior?

In other words, what is the factor that makes the shaded cell acts as a load and move in the reverse voltage direction leading to hot spot, or force other cells connected to it in series. Because the curve contains the two situations, so how can I know which situation the cell will have?

[André Mermoud]

As they are connected in series, all the cells in the module are submitted to the same current.

Now if this current is forced over the Isc of a given cell (horizontal line on the graph above), this cell is reverse-biased and "consumes" power (positive current, negative voltage).