Port SVN r3646: updates to TInvDynamicVars.CalcGFMYprim (by davismont)

Ref:
git-svn-id: https://svn.code.sf.net/p/electricdss/code/trunk@3646 d8739450-1e93-4ef4-a0af-c327d92816ff

src/Shared/InvDynamics.pas

@@ -246,6 +246,8 @@ procedure TInvDynamicVars.CalcGFMYprim(NPhases: Integer; YMatrix: PCMatrix);
     R1,
     // R2,
     // X2,
+    X1R1,
+    X0R0,
     Isc1,
     Xs,
     Rs,
@@ -260,13 +262,17 @@ procedure TInvDynamicVars.CalcGFMYprim(NPhases: Integer; YMatrix: PCMatrix);
     R1 := X1 / 4; // Uses defaults
     // R2 := R1;     // default Z2 = Z1
     // X2 := X1;
+    R0 := 1.9;
+    X0 := 5.7;
+    X1R1 := X1 / R1;
+    X0R0 := X0 / R0;
     Isc1 := (mKVARating * 1000.0 / (sqrt(3) * RatedkVLL)) / NPhases;
     // Compute R0, X0
     a := 10;
-    b := (4.0 * (R1 + X1 * 3));
+    b := (4.0 * (R1 + (X1 * X0R0)));
     c := (4.0 * (R1 * R1 + X1 * X1) - SQR((sqrt(3) * RatedkVLL * 1000.0) / Isc1));
     R0 := QuadSolver(a, b, c);
-    X0 := R0 * 3;
+    X0 := R0 * X0R0;
     // for Z matrix
     Xs := (2.0 * X1 + X0) / 3.0;
     Rs := (2.0 * R1 + R0) / 3.0;