Compensation network forward gain

[zereshki]

Need help for control loop

Hello.
for design a voltage mode control compensation network of smps I need calculate forward gain (G) in 1+GH equation that H is compensation network Gain.
that for forward gain we have : G = Vin * (Ns/Np) * Gm
where:
Ns/Np= trans ratio
Gm= modulator gain

suppose a half bridge smps designed to work for 175 to 280 Volt AC:

1-for Vin which on of this equation must be used:
Vin= 175*√2
or
Vin= 280*√2
2- for half bridge is it necessary consider /2 factor : Vin= (Vac*√2) / 2 or not?
3- in out-put LC filter I use iron powder core for L (314uH). because of non linear BH curve of iron powder cores, by increasing Load that cause increase of inductance current, that make decrease L, so Flc=1/(2π√LC) resonance frequency will be increased. in compensation network design which LC frequency must be used, Flc_max or Flc_min ?

regards

 

[zereshki]

:sad:
No body to help?!

 

[mtwieg]

In practice when the response of your plant (the converter) is variable (which it always is), you'll usually have to design the compensation for worst case scenarios. I usually use matlab scripts to show me the closed loop stability under all extreme conditions and just manually adjust the compensation network until things look right.