code: def getAugYbus(self, U0, gbus):
          
          j = 0 + 1j
          buses = self.case.connected_buses
          nb = len(buses)
  
          Ybus, _, _ = self.case.getYbus()
  
          # Steady-state bus voltages.
  
          # Calculate equivalent load admittance
          Sd = array([self.case.s_demand(bus) for bus in buses])
          Yd = conj(Sd) / abs(U0)**2
  
          xd_tr = array([g.xd_tr for g in self.dyn_generators])
  
          # Calculate equivalent generator admittance.
          Yg = zeros(nb)
          Yg[gbus] = 1 / (j * xd_tr)
  
          # Add equivalent load and generator admittance to Ybus matrix
          for i in range(nb):
              Ybus[i, i] = Ybus[i, i] + Yg[i] + Yd[i]
  
          return Ybus
docs: Based on AugYbus.m from MatDyn by Stijn Cole, developed at
          Katholieke Universiteit Leuven. See U{http://www.esat.kuleuven.be/
          electa/teaching/matdyn/} for more information.
  
          @rtype: csr_matrix
          @return: The augmented bus admittance matrix.