Source Code for Module pypower.makeYbus

  1  # Copyright (C) 1996-2011 Power System Engineering Research Center (PSERC) 
  2  # Copyright (C) 2011 Richard Lincoln 
  3  # 
  4  # PYPOWER is free software: you can redistribute it and/or modify 
  5  # it under the terms of the GNU General Public License as published 
  6  # by the Free Software Foundation, either version 3 of the License, 
  7  # or (at your option) any later version. 
  8  # 
  9  # PYPOWER is distributed in the hope that it will be useful, 
 10  # but WITHOUT ANY WARRANTY; without even the implied warranty of 
 11  # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 
 12  # GNU General Public License for more details. 
 13  # 
 14  # You should have received a copy of the GNU General Public License 
 15  # along with PYPOWER. If not, see <http://www.gnu.org/licenses/>. 
 16   
 17  """Builds the bus admittance matrix and branch admittance matrices. 
 18  """ 
 19   
 20  from sys import stderr 
 21   
 22  from numpy import ones, conj, nonzero, any, exp, pi, r_ 
 23  from scipy.sparse import csr_matrix 
 24   
 25  from idx_bus import BUS_I, GS, BS 
 26  from idx_brch import F_BUS, T_BUS, BR_R, BR_X, BR_B, BR_STATUS, SHIFT, TAP 
 27   
 28   
 29 -def makeYbus(baseMVA, bus, branch): 
 30      """Builds the bus admittance matrix and branch admittance matrices. 
 31   
 32      Returns the full bus admittance matrix (i.e. for all buses) and the 
 33      matrices C{Yf} and C{Yt} which, when multiplied by a complex voltage 
 34      vector, yield the vector currents injected into each line from the 
 35      "from" and "to" buses respectively of each line. Does appropriate 
 36      conversions to p.u. 
 37   
 38      @see: L{makeSbus} 
 39   
 40      @author: Ray Zimmerman (PSERC Cornell) 
 41      @author: Richard Lincoln 
 42      """ 
 43      ## constants 
 44      nb = bus.shape[0]          ## number of buses 
 45      nl = branch.shape[0]       ## number of lines 
 46   
 47      ## check that bus numbers are equal to indices to bus (one set of bus nums) 
 48      if any(bus[:, BUS_I] != range(nb)): 
 49          stderr.write('buses must appear in order by bus number\n') 
 50   
 51      ## for each branch, compute the elements of the branch admittance matrix where 
 52      ## 
 53      ##      | If |   | Yff  Yft |   | Vf | 
 54      ##      |    | = |          | * |    | 
 55      ##      | It |   | Ytf  Ytt |   | Vt | 
 56      ## 
 57      stat = branch[:, BR_STATUS]              ## ones at in-service branches 
 58      Ys = stat / (branch[:, BR_R] + 1j * branch[:, BR_X])  ## series admittance 
 59      Bc = stat * branch[:, BR_B]              ## line charging susceptance 
 60      tap = ones(nl)                           ## default tap ratio = 1 
 61      i = nonzero(branch[:, TAP])              ## indices of non-zero tap ratios 
 62      tap[i] = branch[i, TAP]                  ## assign non-zero tap ratios 
 63      tap = tap * exp(1j * pi / 180 * branch[:, SHIFT]) ## add phase shifters 
 64   
 65      Ytt = Ys + 1j * Bc / 2 
 66      Yff = Ytt / (tap * conj(tap)) 
 67      Yft = - Ys / conj(tap) 
 68      Ytf = - Ys / tap 
 69   
 70      ## compute shunt admittance 
 71      ## if Psh is the real power consumed by the shunt at V = 1.0 p.u. 
 72      ## and Qsh is the reactive power injected by the shunt at V = 1.0 p.u. 
 73      ## then Psh - j Qsh = V * conj(Ysh * V) = conj(Ysh) = Gs - j Bs, 
 74      ## i.e. Ysh = Psh + j Qsh, so ... 
 75      ## vector of shunt admittances 
 76      Ysh = (bus[:, GS] + 1j * bus[:, BS]) / baseMVA 
 77   
 78      ## build connection matrices 
 79      f = branch[:, F_BUS]                           ## list of "from" buses 
 80      t = branch[:, T_BUS]                           ## list of "to" buses 
 81      ## connection matrix for line & from buses 
 82      Cf = csr_matrix((ones(nl), (range(nl), f)), (nl, nb)) 
 83      ## connection matrix for line & to buses 
 84      Ct = csr_matrix((ones(nl), (range(nl), t)), (nl, nb)) 
 85   
 86      ## build Yf and Yt such that Yf * V is the vector of complex branch currents injected 
 87      ## at each branch's "from" bus, and Yt is the same for the "to" bus end 
 88      i = r_[range(nl), range(nl)]                   ## double set of row indices 
 89   
 90      Yf = csr_matrix((r_[Yff, Yft], (i, r_[f, t])), (nl, nb)) 
 91      Yt = csr_matrix((r_[Ytf, Ytt], (i, r_[f, t])), (nl, nb)) 
 92      # Yf = spdiags(Yff, 0, nl, nl) * Cf + spdiags(Yft, 0, nl, nl) * Ct 
 93      # Yt = spdiags(Ytf, 0, nl, nl) * Cf + spdiags(Ytt, 0, nl, nl) * Ct 
 94   
 95      ## build Ybus 
 96      Ybus = Cf.T * Yf + Ct.T * Yt + \ 
 97          csr_matrix((Ysh, (range(nb), range(nb))), (nb, nb)) 
 98   
 99      return Ybus, Yf, Yt 
100