Matlab analysis of OLTCs DRSSTCs and untuned primary SSTCs

This plot shows the efficiency
of my DRSSTC, at a coupling of 0.1 with and without the secondary loss. I think
you can figure out which one is which ;^). The x axis is the drive frequency,
in rad/sec with the resonant frequency held constant at 375K.

This one is the same thing,
except the k is 0.28

This plot shows efficiency on
the y axis, and time on the x axis for an OLTC without secondary loss. Blue is
k=0.28, red is k=0.1. The reason the plot is not smooth is that efficiency is
defined as energy in c2/initial energy in c1.

This is for a SSTC with an
untuned primary. The k is 0.35 and the resonant frequency is the same for the
red line, and doubled for the blue one. The higher frequency works better, due
to less magnifying current. The peak Efficiency is at the poles not the zero,
even though the secondary's capacitive current partially cancels magnetizing
current. Because of the hard switching at high current, the efficiency might go
down 1/2 or 1%, but the effect is negligible.

The secondary inductor and
toroid are the same for all three coils, (with the exception of the blue line
on the last one, because the secondary inductance is down by a factor of 4) and
the energy transfer is also the same. The amount of IGBTs is also the same, so
the OLTC and DRSSTC with k of 0.28 should be a little more efficient, but it
would cost more IGBTs. The drive voltage for the DRSSTC is 400 volts, and the
primary voltage for the OLTC is 700 volts.

There is also the cost of capacitors.
DRSSTCs only need a quarter of the amount of capacitors that the OLTC needs,
but the untuned primary SSTCs don't need any. As far as cost goes, untuned
primary SSTCs might do best, but they would be slightly less efficient, and
designing it might be tough because of hard switching at high current, and the
huge current offset.

Here are the Matlab files

DRSSTC script OLTC script
untuned primary SSTC script Matlab
model