Source Code for Module pypower.modcost

  1  # Copyright (C) 2010-2011 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 
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  7  # or (at your option) any later version. 
  8  # 
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 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  """Modifies generator costs by shifting or scaling (F or X). 
 18  """ 
 19   
 20  import sys 
 21   
 22  from numpy import zeros, ones, arange, dot, cumsum, flatnonzero as find 
 23   
 24  from idx_cost import MODEL, NCOST, PW_LINEAR, POLYNOMIAL, COST 
 25   
 26   
 27 -def modcost(gencost, alpha, modtype='SCALE_F'): 
 28      """Modifies generator costs by shifting or scaling (F or X). 
 29   
 30      For each generator cost F(X) (for real or reactive power) in 
 31      C{gencost}, this function modifies the cost by scaling or shifting 
 32      the function by C{alpha}, depending on the value of C{modtype}, and 
 33      and returns the modified C{gencost}. Rows of C{gencost} can be a mix 
 34      of polynomial or piecewise linear costs. 
 35   
 36      C{modtype} takes one of the 4 possible values (let F_alpha(X) denote the 
 37      the modified function):: 
 38          SCALE_F (default) : F_alpha(X)         == F(X) * ALPHA 
 39          SCALE_X           : F_alpha(X * ALPHA) == F(X) 
 40          SHIFT_F           : F_alpha(X)         == F(X) + ALPHA 
 41          SHIFT_X           : F_alpha(X + ALPHA) == F(X) 
 42   
 43      @author: Ray Zimmerman (PSERC Cornell) 
 44      @author: Richard Lincoln 
 45      """ 
 46      gencost = gencost.copy() 
 47   
 48      ng, m = gencost.shape 
 49      if ng != 0: 
 50          ipwl = find(gencost[:, MODEL] == PW_LINEAR) 
 51          ipol = find(gencost[:, MODEL] == POLYNOMIAL) 
 52          c = gencost[ipol, COST:m] 
 53   
 54          if modtype == 'SCALE_F': 
 55              gencost[ipol, COST:m]       = alpha * c 
 56              gencost[ipwl, COST+1:m:2]   = alpha * gencost[ipwl, COST + 1:m:2] 
 57          elif modtype == 'SCALE_X': 
 58              for k in range(len(ipol)): 
 59                  n = gencost[ipol[k], NCOST].astype(int) 
 60                  for i in range(n): 
 61                      gencost[ipol[k], COST + i] = c[k, i] / alpha**(n - i - 1) 
 62              gencost[ipwl, COST:m - 1:2]   = alpha * gencost[ipwl, COST:m - 1:2] 
 63          elif modtype == 'SHIFT_F': 
 64              for k in range(len(ipol)): 
 65                  n = gencost[ipol[k], NCOST].astype(int) 
 66                  gencost[ipol[k], COST + n - 1] = alpha + c[k, n - 1] 
 67              gencost[ipwl, COST+1:m:2]   = alpha + gencost[ipwl, COST + 1:m:2] 
 68          elif modtype == 'SHIFT_X': 
 69              for k in range(len(ipol)): 
 70                  n = gencost[ipol[k], NCOST].astype(int) 
 71                  gencost[ipol[k], COST:COST + n] = \ 
 72                          polyshift(c[k, :n].T, alpha).T 
 73              gencost[ipwl, COST:m - 1:2]   = alpha + gencost[ipwl, COST:m - 1:2] 
 74          else: 
 75              sys.stderr.write('modcost: "%s" is not a valid modtype\n' % modtype) 
 76   
 77      return gencost 
 78   
 79   
 80 -def polyshift(c, a): 
 81      """Returns the coefficients of a horizontally shifted polynomial. 
 82   
 83      C{d = polyshift(c, a)} shifts to the right by C{a}, the polynomial whose 
 84      coefficients are given in the column vector C{c}. 
 85   
 86      Example: For any polynomial with C{n} coefficients in C{c}, and any values 
 87      for C{x} and shift C{a}, the C{f - f0} should be zero:: 
 88          x = rand 
 89          a = rand 
 90          c = rand(n, 1); 
 91          f0 = polyval(c, x) 
 92          f  = polyval(polyshift(c, a), x+a) 
 93      """ 
 94      n = len(c) 
 95      d = zeros(c.shape) 
 96      A = pow(-a * ones(n), arange(n)) 
 97      b = ones(n) 
 98      for k in range(n): 
 99          d[n - k - 1] = dot(b, c[n - k - 1::-1] * A[:n - k]) 
100          b = cumsum(b[:n - k - 1]) 
101   
102      return d 
103