Gain plot of open loop never crosses 0 dB

Thread Starter

ANIMO

Joined Sep 12, 2020
3
Hi!
Below is the open loop output current to control plot for a CLLC resonant converter(obtained using AC sweep in PSIM) . As you can see the gain curve never crosses the 0 dB line and the phase margin is inf, hence the open loop system is always stable.
Note: switching frequency is around 200kHz, and the resonant frequency is 300kHz.
My question:
  1. Can we use a simple P controller in a closed loop as the OL system is theoretically stable?
  2. Why do we need DC gain in this case? (a friend suggested using a PI controller to give High DC gain)

    1680749390523.png1680751009153.png

Please, let me know if you need any other information, Thanks in Advance.
 
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