Source Code for Module pypower.poly2pwl

 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  # 
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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  """Converts polynomial cost variable to piecewise linear. 
18  """ 
19   
20  from numpy import ones, zeros, r_ 
21   
22  from idx_cost import MODEL, COST, NCOST, PW_LINEAR 
23   
24  from totcost import totcost 
25   
26   
27 -def poly2pwl(polycost, Pmin, Pmax, npts): 
28      """Converts polynomial cost variable to piecewise linear. 
29   
30      Converts the polynomial cost variable C{polycost} into a piece-wise linear 
31      cost by evaluating at zero and then at C{npts} evenly spaced points between 
32      C{Pmin} and C{Pmax}. If C{Pmin <= 0} (such as for reactive power, where 
33      C{P} really means C{Q}) it just uses C{npts} evenly spaced points between 
34      C{Pmin} and C{Pmax}. 
35      """ 
36      pwlcost = polycost 
37      ## size of piece being changed 
38      m, n = polycost.shape 
39      ## change cost model 
40      pwlcost[:, MODEL]  = PW_LINEAR * ones(m) 
41      ## zero out old data 
42      pwlcost[:, COST:COST + n] = zeros(pwlcost[:, COST:COST + n].shape) 
43      ## change number of data points 
44      pwlcost[:, NCOST]  = npts * ones(m) 
45   
46      for i in range(m): 
47          if Pmin[i] == 0: 
48              step = (Pmax[i] - Pmin[i]) / (npts - 1) 
49              xx = range(Pmin[i], step, Pmax[i]) 
50          elif Pmin[i] > 0: 
51              step = (Pmax[i] - Pmin[i]) / (npts - 2) 
52              xx = r_[0, range(Pmin[i], step, Pmax[i])] 
53          elif Pmin[i] < 0 & Pmax[i] > 0:        ## for when P really means Q 
54              step = (Pmax[i] - Pmin[i]) / (npts - 1) 
55              xx = range(Pmin[i], step, Pmax[i]) 
56          yy = totcost(polycost[i, :], xx) 
57          pwlcost[i,      COST:2:(COST + 2*(npts-1)    )] = xx 
58          pwlcost[i,  (COST+1):2:(COST + 2*(npts-1) + 1)] = yy 
59   
60      return pwlcost 
61