I am attempting to design a DC-AC inverter for my third year project. I have successfully simulated the inverter on PSIM with an inner loop current controller and an outer voltage control loop (see attached images). However, when I attempt to use op amps for the PID circuit, the simulation just doesn't run as desired. I get a constant dc 5V output. Kindly help in this regard.

Parameters:
Input voltage = 400V output = 230 rms, 50Hz. Switching freq = 50khz.
1st image: conceptual design
2nd image output of conceptual design
3rd image pid using op amps (does not run as desired).

Integral time constant = R9C3
Proportional gain = R9.R10/(R8.R11)
All unspecified resistances are 10k.

 

You need to look at all the signals in the loop to determine at what point the voltages do not seem correct.

Troubleshooting a malfunctioning design is one of the more important tasks of a design engineer. and this is a good opportunity to hone your skills.