Source Code for Module pypower.makePTDF

 1  # Copyright (C) 2006-2011 Power System Engineering Research Center (PSERC) 
 2  # Copyright (C) 2011 Richard Lincoln 
 3  # 
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16   
17  """Builds the DC PTDF matrix for a given choice of slack. 
18  """ 
19   
20  from sys import stderr 
21   
22  from numpy import zeros, arange, isscalar, dot, ix_, flatnonzero as find 
23   
24  from numpy.linalg import solve 
25   
26  from idx_bus import BUS_TYPE, REF, BUS_I 
27  from makeBdc import makeBdc 
28   
29   
30 -def makePTDF(baseMVA, bus, branch, slack=None): 
31      """Builds the DC PTDF matrix for a given choice of slack. 
32   
33      Returns the DC PTDF matrix for a given choice of slack. The matrix is 
34      C{nbr x nb}, where C{nbr} is the number of branches and C{nb} is the 
35      number of buses. The C{slack} can be a scalar (single slack bus) or an 
36      C{nb x 1} column vector of weights specifying the proportion of the 
37      slack taken up at each bus. If the C{slack} is not specified the 
38      reference bus is used by default. 
39   
40      For convenience, C{slack} can also be an C{nb x nb} matrix, where each 
41      column specifies how the slack should be handled for injections 
42      at that bus. 
43   
44      @see: L{makeLODF} 
45   
46      @author: Ray Zimmerman (PSERC Cornell) 
47      @author: Richard Lincoln 
48      """ 
49      ## use reference bus for slack by default 
50      if slack is None: 
51          slack = find(bus[:, BUS_TYPE] == REF) 
52          slack = slack[0] 
53   
54      ## set the slack bus to be used to compute initial PTDF 
55      if isscalar(slack): 
56          slack_bus = slack 
57      else: 
58          slack_bus = 0      ## use bus 1 for temp slack bus 
59   
60      nb = bus.shape[0] 
61      nbr = branch.shape[0] 
62      noref = arange(1, nb)      ## use bus 1 for voltage angle reference 
63      noslack = find(arange(nb) != slack_bus) 
64   
65      ## check that bus numbers are equal to indices to bus (one set of bus numbers) 
66      if any(bus[:, BUS_I] != arange(nb)): 
67          stderr.write('makePTDF: buses must be numbered consecutively') 
68   
69      ## compute PTDF for single slack_bus 
70      Bbus, Bf, _, _ = makeBdc(baseMVA, bus, branch) 
71      Bbus, Bf = Bbus.todense(), Bf.todense() 
72      H = zeros((nbr, nb)) 
73      H[:, noslack] = solve( Bbus[ix_(noslack, noref)].T, Bf[:, noref].T ).T 
74      #             = Bf[:, noref] * inv(Bbus[ix_(noslack, noref)]) 
75   
76      ## distribute slack, if requested 
77      if not isscalar(slack): 
78          if len(slack.shape) == 1:  ## slack is a vector of weights 
79              slack = slack / sum(slack)   ## normalize weights 
80   
81              ## conceptually, we want to do ... 
82              ##    H = H * (eye(nb, nb) - slack * ones((1, nb))) 
83              ## ... we just do it more efficiently 
84              v = dot(H, slack) 
85              for k in range(nb): 
86                  H[:, k] = H[:, k] - v 
87          else: 
88              H = dot(H, slack) 
89   
90      return H 
91