What you have drawn is one of those Phd. diodes except without Rd.
What do you mean by PhD diodes, idealized diodes? Something that takes into consideration the bulk resistance? Rd is not mentioned in the link, but they do have a circuit with an idealized diode with a source voltage and a resistance they call "R". They show several methods of calculating that current. I used a source voltage of 340 volts and calculated the Vf at R=0 to be 1.53 volts and at R=100 Vf is 1.35 volts. Those figures appear reasonable, don't they? Vf doesn't change much either.
Have a look at this. Read far enough to see the curves defining the parts that make up Vf. You will find that by adding Rd you get the slope I defined earlier which will limit the current and increase the time constant. Also matches the spice models.
I think you are referring to piecewise linear models. I don't think you have enough segments in your model to be viable at those high currents. I would use a graphical method instead. Don't forget that the transient pulse period is very, very small.
https://en.wikipedia.org/wiki/Diode..._voltage_source_and_current-limiting_resistor[/quote]
Ratch