Source Code for Module pypower.polycost

 1  # Copyright (C) 2009-2011 Power System Engineering Research Center (PSERC) 
 2  # Copyright (C) 2011 Richard Lincoln 
 3  # 
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 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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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  """Evaluates polynomial generator cost & derivatives. 
18  """ 
19   
20  import sys 
21   
22  from numpy import zeros, arange, flatnonzero as find 
23   
24  from idx_cost import MODEL, NCOST, PW_LINEAR, COST 
25   
26   
27 -def polycost(gencost, Pg, der=0): 
28      """Evaluates polynomial generator cost & derivatives. 
29   
30      C{f = polycost(gencost, Pg)} returns the vector of costs evaluated at C{Pg} 
31   
32      C{df = polycost(gencost, Pg, 1)} returns the vector of first derivatives 
33      of costs evaluated at C{Pg} 
34   
35      C{d2f = polycost(gencost, Pg, 2)} returns the vector of second derivatives 
36      of costs evaluated at C{Pg} 
37   
38      C{gencost} must contain only polynomial costs 
39      C{Pg} is in MW, not p.u. (works for C{Qg} too) 
40   
41      @author: Ray Zimmerman (PSERC Cornell) 
42      @author: Richard Lincoln 
43      """ 
44      if any(gencost[:, MODEL] == PW_LINEAR): 
45          sys.stderr.write('polycost: all costs must be polynomial\n') 
46   
47      ng = len(Pg) 
48      maxN = max( gencost[:, NCOST].astype(int) ) 
49      minN = min( gencost[:, NCOST].astype(int) ) 
50   
51      ## form coefficient matrix where 1st column is constant term, 2nd linear, etc. 
52      c = zeros((ng, maxN)) 
53      for n in arange(minN, maxN + 1): 
54          k = find(gencost[:, NCOST] == n)   ## cost with n coefficients 
55          c[k, :n] = gencost[k, (COST + n - 1):COST - 1:-1] 
56   
57      ## do derivatives 
58      for d in range(1, der + 1): 
59          if c.shape[1] >= 2: 
60              c = c[:, 1:maxN - d + 1] 
61          else: 
62              c = zeros((ng, 1)) 
63              break 
64   
65          for k in range(2, maxN - d + 1): 
66              c[:, k-1] = c[:, k-1] * k 
67   
68      ## evaluate polynomial 
69      if len(c) == 0: 
70          f = zeros(Pg.shape) 
71      else: 
72          f = c[:, :1].flatten()  ## constant term 
73          for k in range(1, c.shape[1]): 
74              f = f + c[:, k] * Pg**k 
75   
76      return f 
77