{ind, cap, res}={l i'[t]==(Subscript[v, l])[t],(Subscript[v, c])'[t]==1/c i[t],r i[t]==(Subscript[v, r])[t]};
kirchhoff=(Subscript[v, l])[t]+(Subscript[v, c])[t]+(Subscript[v, r])[t]==(Subscript[v, s])[t];

circuit=StateSpaceModel[{ind,cap,res,kirchhoff},{i[t],(Subscript[v, l])[t],(Subscript[v, c])[t],(Subscript[v, r])[t]},{(Subscript[v, s])[t]},{(Subscript[v, r])[t]},t]

circuit=circuit/.{r->4,c->1/1000,l->1/100};

y0=OutputResponse[circuit,Sin[2 Pi 60 t],{t,0,.3},Method->{"NDSolve",AccuracyGoal->7}];
Plot[y0,{t,0,.1},ImageSize->Medium]

k=Simplify@StateFeedbackGains[circuit,{re+I im,re-I im}];
csys=SystemsModelStateFeedbackConnect[circuit,k];

TransferFunctionPoles[circuit]

y1=OutputResponse[csys/. {re->-800,im->100 (Sqrt[6])},Sin[2 π 60 t],{t,0,.2}];
y2=OutputResponse[csys/. {re->-200,im->800},Sin[2 π 60 t],{t,0,.2}];

Plot[{y0,y1,y2},{t,0,.1},PlotRange->All,PlotStyle->{Dashed,Thick,Thick,Thick},PlotLegends->{"OpenLoop","Increased Re","Increased Im"},ImageSize->Medium]