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Hi all I use currently the FFT of single voltage or current and I would like to do the same with expressions like : V(n001)-V(n007) or other valid numerical expressions for instance in a current

With trap integration and the alternate solver the crossover voltage can be reduced to 70 V and it is barley able to run to completion. Plotting the voltage across the inductor shows the instability.

That should be crossover voltage. With a low crossover voltage the peak current through B1 is very high (500 W / crossover voltage) before the current starts to drop towards zero at the zero crossing

The required capacitance depends upon the crossover power setting of B1. If the crossover is increased to 50 then only 1 uF is needed. If the crossover is increased to 100 then no capacitance is

Eaglesea Adding a 100uf cap across B1 gets the simulation to run. I think the problem is an oscillation caused by putting a current source in series with an inductor. Dan

Interesting! Andy

That's not quite true. In order for them to captured and printed in the logfile, the braces need to be removed. Then it will work. -- Regards, Tony

Remove all the braces, then it will work as you want. You never need braces anyway with .param directives. If used with .meas xxx param yyy, you will only get one measured value, as you observed.

The reason this happens is the braces on the .meas xxx param yyy lines. That has a special effect of fixing the meas result to the first one. Remove all the braces! You don't ever need them for .param

Thanks for the nudge, Andy! Yep, the give-away was that the values for Ncells was always for the last Voc step. At one point, I did have voltages for Ncells/2, but thought it looked kludgy, and

Eaglesea, This is probably not much of an answer yet to your questions. LTspice has a lot of trouble.? Sometimes I had "timestep too small" aborts, but mostly I see math errors where it displays

Yes, I missed that fact! It shows that I am still human, after all.? :-) So, ignore most of what I wrote that pertains to .AC analysis. Andy

I need to refresh my memory about this.? However, ... Remember that all .MEAS commands are evaluated after all simulations are complete.? I think it means that user-defined PARAMeters hold their

Of course, the error is more likely with me, but: I'm experimenting with a simple solar cell/array simulator I can reuse with larger models. It's working and stable, at a wide range of open circuit

All, Thank you all for the different responses. I truly appreciate it. I am new to LTspice so all comments are educational. for that thank you I have uploaded the schematic, " Modeling Constant Power

Andy, I am surprised at your response; you are typically very on point! The OP stated: “convergence failure when I run transient analysis” That zero crossing… That said, with two devices, I was

For AC analysis of an active network, isn't the "gain" at the operating point used? If so, does that load function provide a stable operating point - that is, can an operating point really be found?

Smoother functions are almost always better, in terms of stability and avoiding instability. What zero crossing?? If it is an .AC analysis that you're doing, there are no zero-crossings.? There are

I am not sure how that relates to the circuit elements and their equations that you used.? But note that the formula for P has a significant discontinuity at V(vout) = 5.? The discontinuity also

LTspice has a constant power load already.? See: https://www.analog.com/en/resources/technical-articles/ltspice-modeling-constant-power-loads.html However, that is intended for .TRAN or .OP or .DC