closed loop transfer function active damping

Dear,

I am working on a circuit which consists of inverter subsequent by a filter as shown in the figure, the filter consists of LC and RC as branch for the filter. I have gotten after the filter a sinusoidal waveform because I have placed a resistor as a passive damping, but I would like to make an active damping. I have kept everything of the circuit but I have added a control loop after the filter before the load and send the feedback to the PWM (sin wave), but I don't get the proper result which I excpet.

the only I have done in the control loop is PI controller inserted plus represent the transfer function of the filter by combining the C1 with R+C2 in one leg then make a low pass filter lc.

I have to add an active damping in order to delete the phase delay from the switching inverter plus i want reduce the damping error which happens because i have added a resistor. can you tell me how can i make the active damping control loop. what is the input and output of it?

I don't know what is the input and the output of the active damping?

Thanks, Fadi