code: def _initial_interior_point(self, buses, generators, xmin, xmax, ny):
          
          Va = self.om.get_var("Va")
          va_refs = [b.v_angle * pi / 180.0 for b in buses
                     if b.type == REFERENCE]
          x0 = (xmin + xmax) / 2.0
  
          x0[Va.i1:Va.iN + 1] = va_refs[0] # Angles set to first reference angle.
  
          if ny > 0:
              yvar = self.om.get_var("y")
  
              # Largest y-value in CCV data
              c = []
              for g in generators:
                  if g.pcost_model == PW_LINEAR:
                      for _, y in g.p_cost:
                          c.append(y)
  
  
              x0[yvar.i1:yvar.iN + 1] = max(c) * 1.1
  
          return x0
docs: Selects an interior initial point for interior point solver.