Question: Error, (in DynamicSystems:-EquilibriumPoint) unable to convert the system to an explicit index 1 form

Hi 

I'm trying to find the equilibrium point by using DynamicSystem package here is my code:

pi := Pi; Cb := 1/(50*((1/1200)*220^2*2)*pi); ipu := 1200*10^6/(220*10^3*sqrt(3)); Fnom := 50; Rc := 0.3e-2*((1/1200)*220^2); Lc := (0.8e-1*((1/1200)*220^2))/(2*pi*Fnom); w := 2*pi*50; cf := 0.74e-1*Cb; scr := .2; z := .8; Ln := (1/1200)*z*sind(80)*220^2/(2*pi*Fnom); Rn := (1/1200)*z*cosd(80)*220^2; wlpll := 200; wb := 2*pi*50; kp1 := 1.27*ipu; kp2 := 1.27*ipu; ki1 := 14.25*ipu; ki2 := 14.25*ipu; kpll := wlpll/(3*wb); Tipll := 3^2/wlpll; kipll := kpll/Tipll; KpP := 1; KpQ := .1; Kp := 50; Kq := 5; wad := 200; Kad := 10; wlpP := 200; wlpv := 10; zv := .8; lv := (1/1200)*zv*sind(80)*220^2/(2*pi*50); rv := (1/1200)*zv*cosd(80)*220^2;
wPLL := kpll*atan2(ucqfT, ucdfT)+kipll*Gpll+w;
icdref := KpP*(u(1)-Pm/(1200*10^6))+Kp*GP; icqref := -KpQ*(u(2)-Vm/(0.17963e6))-Kq*GQ; ucdT := ucd*cos(thetaPLL)+ucq*sin(thetaPLL)-rv*(igd*cos(thetaPLL)+igq*sin(thetaPLL))+wPLL*lv*(igq*cos(thetaPLL)-igd*sin(thetaPLL)); ucqT := ucq*cos(thetaPLL)-ucd*sin(thetaPLL)-rv*(igq*cos(thetaPLL)-igd*sin(thetaPLL))-wPLL*lv*(igd*cos(thetaPLL)+igq*sin(thetaPLL)); Vd_c := ucd*cos(thetaPLL)+ucq*sin(thetaPLL)-w*Lc*icq*cos(thetaPLL)+w*Lc*icd*sin(thetaPLL)+kp1*icdref*ipu-kp1*cos(thetaPLL)*icd-kp1*sin(thetaPLL)*icq+ki1*Gd-Kad*(ucd*cos(thetaPLL)+ucq*sin(thetaPLL)-phid); Vq_c := ucq*cos(thetaPLL)-ucd*sin(thetaPLL)+w*Lc*icd*cos(thetaPLL)+w*Lc*icq*sin(thetaPLL)+kp2*icqref*ipu-kp2*cos(thetaPLL)*icq+kp2*sin(thetaPLL)*icd+ki2*Gq-Kad*(ucq*cos(thetaPLL)-ucd*sin(thetaPLL)-phiq); Vd := cos(thetaPLL)*Vd_c-sin(thetaPLL)*Vq_c; Vq := sin(thetaPLL)*Vd_c+cos(thetaPLL)*Vq_c; Upu := 0.17963e6;
icd := x__1(t); icq := x__2(t); ucd := x__3(t); ucq := x__4(t); igd := x__5(t); igq := x__6(t); Gd := x__7(t); Gq := x__8(t); thetaPLL := x__9(t); Gpll := x__10(t); ucdfT := x__11(t); ucqfT := x__12(t); GP := x__13(t); GQ := x__14(t); phid := x__15(t); phiq := x__16(t); Pm := x__17(t); Vm := x__18(t);
sys1 := [diff(x[1](t), t) = Vd/Lc-ucd/Lc-Rc*icd/Lc+w*icq, diff(x[2](t), t) = Vq/Lc-ucq/Lc-Rc*icq/Lc-w*icd, diff(x[3](t), t) = icd/cf-igd/cf+w*ucq, diff(x[4](t), t) = icq/cf-igq/cf-w*ucd, diff(x[5](t), t) = ucd/Ln-Rn*igd/Ln+w*igq-u__3(t)/Ln, diff(x[6](t), t) = ucq/Ln-Rn*igq/Ln-w*igd, diff(x[7](t), t) = icdref*ipu-icd*cos(thetaPLL)+icq*sin(thetaPLL), diff(x[8](t), t) = icqref*ipu-icq*cos(thetaPLL)-icd*sin(thetaPLL), diff(x[9](t), t) = wb*(kpll*atan2(ucqfT, ucdfT)+kipll*Gpll), diff(x[10](t), t) = atan2(ucqfT, ucdfT), diff(x[11](t), t) = ucdT*wlpll-ucdfT*wlpll, diff(x[12](t), t) = ucqT*wlpll-ucqfT*wlpll, diff(x[13](t), t) = u__1(t)-Pm/(1200*10^6), diff(x[14](t), t) = u__2(t)-Vm/(0.17963e6), diff(x[15](t), t) = wad*(ucd*cos(thetaPLL)+ucq*sin(thetaPLL))-wad*phid, diff(x[16](t), t) = wad*(ucq*cos(thetaPLL)-ucd*sin(thetaPLL))-wad*phiq, diff(x[17](t), t) = wlpP*(igd*ucd+igq*ucq)-wlpP*Pm, diff(x[18](t), t) = wlpv*(ucd^2+ucq^2)^.5-wlpv*Vm, y__1(t) = igd*ucd+igq*ucq, y__2(t) = igd*ucq-igq*ucd];
EquilibriumPoint(sys1, [u__1(t), u__2(t), u__3(t)], initialpoint = [u__1(t) = .97, u__2(t) = 1, u__3(t) = Upu, x[1](t) = 0, x[2](t) = 0, x[3](t) = 0, x[4](t) = 0, x[5](t) = 0, x[6](t) = 0, x[7](t) = 0, x[8](t) = 0, x[9](t) = 0, x[10](t) = 0, x[11](t) = 0, x[12](t) = 0, x[13](t) = 0, x[14](t) = 0, x[15](t) = 0, x[16](t) = 0, x[17](t) = 0, x[18](t) = 0]);

but I got this error..

 Error, (in DynamicSystems:-EquilibriumPoint) unable to convert the system to an explicit index 1 form.

anybody faced the same problem?

Thanks,