Sorry I mis-typed, you probably want to leave v(inp) alone (don't reference it to 'ref') but you do want to change v(internode) to v(internode,ref). There still seems to be some other problem, though, at temperatures other than 25. I don't have time to look any further right now.
--- In LTspice@..., "hamed" <l0st_l0rd@...> wrote:
[snip]
I also tried these formula in the circuit :
gidiode internode ref value={i0*(exp(v(internode)/({vt}*(v(tcell)+273)))-1)}
but the strange thing is that the by increasing the temperature, the open circuit voltage will increase which shouldn't be !!!
If you look at the standard diode formula I = Is * exp(qV/kT) it seems like the voltage -should- go up with increasing T, but that neglects the temperature dependence of Is, which is quite strong. If you don't model that then Voc will go up with temperature. Another reason to use the standard diode model.
-Fred
--- In LTspice@..., "qrx3" <fredh@...> wrote:
Hello Hamed,
While I would also advise you to use a standard diode model instead of building your own, I may be able to shed some light on your difficulty.
Note that your derived values for ISC and VOC are generated in relation to the reference input 'ref'. However when you use these values in your formulae you are using the value relative to ground:
log((v(isc)/{i0})+1)
The same is true when you use the input voltage:
(v(inp)*iscr)/1000)
I have not tried to run your circuit, but I strongly suspect this is why it would work for a single cell where ref = ground and not for a second cell where ref != ground.
I think the most sensible fix would be to reference eisc and evoc to ground instead of ref, so you can observe the values externally if you want and not have to subtract the ref voltage. Then change "v(inp)" for example to "v(inp,ref)" where needed.
I suggest that if you had drawn this as a circuit instead of writing a netlist these issues would have been quickly apparent, but maybe not.
Cheers,
Fred
--- In LTspice@..., "hamed" <l0st_l0rd@> wrote:
Dear friends
in the file below you can find an arbitrary solar cell.
When I put two cells in parallel the answer is correct and when I put them in
series I see a distortion.
I think the problem is related to the diode behavioral model.
I will be thankful if any of you could help me.
sincerely,
Hamed
