Module operating point

josealjim

Hello,

I'm starting with PV systems and even though I have read lot of theory, there are still some points that I don't understand. I hope you could help me with that.

Lets suppose a 36 cells module with 2 bypass diodes:

Attachment not found.

When one cell is shaded it starts consuming power (or generating less), acting as a load. This power consumed is limited by the bypass diode connected in parallel (-0.7v).
When the bypass diode is active, the sub-module (cells protected by bypass) produce 0v.

When the diode is not active (v1-v2<0.7) the sub-module gives voltage according to the current it has to swallow.

The inverter can set the operating point by varying the load. At the module's graph, we can see that even with shadow, the week sub-module can generate 10 v by operating at current bellow 1 A

Attachment not found.

I don't understand that. How one sub-module can produce its normal voltage even being shaded just by operating bellow certain current. I thought there were two possibilities:

- bypass active: 0.5 v drop because the diode. The current flows without problem. The week cell dissipates the power from the cells within the same diode.
- bypass reversed: the current pass though the sub-module, the voltage and current are modified at each cells according to each cell status

What about that third one?
- bypass reversed (current bellow 1 A): the sub-module gives 10v

Could you guys explain me how the inverter acts to obtain 10 volts from that shaded sub-module and what is going on on that situation inside the module.

If the sub-module is shaded, how can it give 10 v?

THANK YOU IN ADVANCE

josealjim

Module operating point

Hello,

I'm starting with PV systems and even though I have read lot of theory, there are still some points that I don't understand. I hope you could help me with that.

Lets suppose a 36 cells module with 2 bypass diodes

When one cell is shaded it starts consuming power (or generating less), acting as a load. This power consumed is limited by the bypass diode connected in parallel (-0.7v).
When the bypass diode is active, the sub-module (cells protected by bypass) produce 0v.

When the diode is not active (v1-v2<0.7) the sub-module gives voltage according to the current it has to swallow.

The inverter can set the operating point by varying the load. At the module's graph, we can see that even with shadow, the week sub-module can generate 10 v by operating at current bellow 1 A

Attachment not found.

I don't understand that. How one sub-module can produce its normal voltage even being shaded just by operating bellow certain current. I thought there were two possibilities:

- bypass active: 0.5 v drop because the diode. The current flows without problem. The week cell dissipates the power from the cells within the same diode.
- bypass reversed: the current pass though the sub-module, the voltage and current are modified at each cells according to each cell status

What about that third one?
- bypass reversed (current bellow 1 A): the sub-module gives 10v

Could you guys explain me how the inverter acts to obtain 10 volts from that shaded sub-module and what is going on on that situation inside the module.

If the sub-module is shaded, how can it give 10 v?

THANK YOU IN ADVANCE