Home > matpower5.1 > makeYbus.m

makeYbus

PURPOSE ^

MAKEYBUS Builds the bus admittance matrix and branch admittance matrices.

SYNOPSIS ^

function [Ybus, Yf, Yt] = makeYbus(baseMVA, bus, branch)

DESCRIPTION ^

MAKEYBUS   Builds the bus admittance matrix and branch admittance matrices.
   [YBUS, YF, YT] = MAKEYBUS(MPC)
   [YBUS, YF, YT] = MAKEYBUS(BASEMVA, BUS, BRANCH)
   
   Returns the full bus admittance matrix (i.e. for all buses) and the
   matrices YF and YT which, when multiplied by a complex voltage vector,
   yield the vector currents injected into each line from the "from" and
   "to" buses respectively of each line. Does appropriate conversions to p.u.
   Inputs can be a MATPOWER case struct or individual BASEMVA, BUS and
   BRANCH values. Bus numbers must be consecutive beginning at 1 (internal
   ordering).

   See also MAKEJAC, MAKESBUS, EXT2INT.

CROSS-REFERENCE INFORMATION ^

This function calls: This function is called by:

SOURCE CODE ^

0001 function [Ybus, Yf, Yt] = makeYbus(baseMVA, bus, branch)
0002 %MAKEYBUS   Builds the bus admittance matrix and branch admittance matrices.
0003 %   [YBUS, YF, YT] = MAKEYBUS(MPC)
0004 %   [YBUS, YF, YT] = MAKEYBUS(BASEMVA, BUS, BRANCH)
0005 %
0006 %   Returns the full bus admittance matrix (i.e. for all buses) and the
0007 %   matrices YF and YT which, when multiplied by a complex voltage vector,
0008 %   yield the vector currents injected into each line from the "from" and
0009 %   "to" buses respectively of each line. Does appropriate conversions to p.u.
0010 %   Inputs can be a MATPOWER case struct or individual BASEMVA, BUS and
0011 %   BRANCH values. Bus numbers must be consecutive beginning at 1 (internal
0012 %   ordering).
0013 %
0014 %   See also MAKEJAC, MAKESBUS, EXT2INT.
0015 
0016 %   MATPOWER
0017 %   Copyright (c) 1996-2015 by Power System Engineering Research Center (PSERC)
0018 %   by Ray Zimmerman, PSERC Cornell
0019 %
0020 %   $Id: makeYbus.m 2644 2015-03-11 19:34:22Z ray $
0021 %
0022 %   This file is part of MATPOWER.
0023 %   Covered by the 3-clause BSD License (see LICENSE file for details).
0024 %   See http://www.pserc.cornell.edu/matpower/ for more info.
0025 
0026 if nargin < 3
0027     mpc     = baseMVA;
0028     baseMVA = mpc.baseMVA;
0029     bus     = mpc.bus;
0030     branch  = mpc.branch;
0031 end
0032 
0033 %% constants
0034 nb = size(bus, 1);          %% number of buses
0035 nl = size(branch, 1);       %% number of lines
0036 
0037 %% define named indices into bus, branch matrices
0038 [PQ, PV, REF, NONE, BUS_I, BUS_TYPE, PD, QD, GS, BS, BUS_AREA, VM, ...
0039     VA, BASE_KV, ZONE, VMAX, VMIN, LAM_P, LAM_Q, MU_VMAX, MU_VMIN] = idx_bus;
0040 [F_BUS, T_BUS, BR_R, BR_X, BR_B, RATE_A, RATE_B, RATE_C, ...
0041     TAP, SHIFT, BR_STATUS, PF, QF, PT, QT, MU_SF, MU_ST, ...
0042     ANGMIN, ANGMAX, MU_ANGMIN, MU_ANGMAX] = idx_brch;
0043 
0044 %% check that bus numbers are equal to indices to bus (one set of bus numbers)
0045 if any(bus(:, BUS_I) ~= (1:nb)')
0046     error('buses must appear in order by bus number')
0047 end
0048 
0049 %% for each branch, compute the elements of the branch admittance matrix where
0050 %%
0051 %%      | If |   | Yff  Yft |   | Vf |
0052 %%      |    | = |          | * |    |
0053 %%      | It |   | Ytf  Ytt |   | Vt |
0054 %%
0055 stat = branch(:, BR_STATUS);                    %% ones at in-service branches
0056 Ys = stat ./ (branch(:, BR_R) + 1j * branch(:, BR_X));  %% series admittance
0057 Bc = stat .* branch(:, BR_B);                           %% line charging susceptance
0058 tap = ones(nl, 1);                              %% default tap ratio = 1
0059 i = find(branch(:, TAP));                       %% indices of non-zero tap ratios
0060 tap(i) = branch(i, TAP);                        %% assign non-zero tap ratios
0061 tap = tap .* exp(1j*pi/180 * branch(:, SHIFT)); %% add phase shifters
0062 Ytt = Ys + 1j*Bc/2;
0063 Yff = Ytt ./ (tap .* conj(tap));
0064 Yft = - Ys ./ conj(tap);
0065 Ytf = - Ys ./ tap;
0066 
0067 %% compute shunt admittance
0068 %% if Psh is the real power consumed by the shunt at V = 1.0 p.u.
0069 %% and Qsh is the reactive power injected by the shunt at V = 1.0 p.u.
0070 %% then Psh - j Qsh = V * conj(Ysh * V) = conj(Ysh) = Gs - j Bs,
0071 %% i.e. Ysh = Psh + j Qsh, so ...
0072 Ysh = (bus(:, GS) + 1j * bus(:, BS)) / baseMVA; %% vector of shunt admittances
0073 
0074 %% build connection matrices
0075 f = branch(:, F_BUS);                           %% list of "from" buses
0076 t = branch(:, T_BUS);                           %% list of "to" buses
0077 Cf = sparse(1:nl, f, ones(nl, 1), nl, nb);      %% connection matrix for line & from buses
0078 Ct = sparse(1:nl, t, ones(nl, 1), nl, nb);      %% connection matrix for line & to buses
0079 
0080 %% build Yf and Yt such that Yf * V is the vector of complex branch currents injected
0081 %% at each branch's "from" bus, and Yt is the same for the "to" bus end
0082 i = [1:nl; 1:nl]';                              %% double set of row indices
0083 Yf = sparse(i, [f; t], [Yff; Yft], nl, nb);
0084 Yt = sparse(i, [f; t], [Ytf; Ytt], nl, nb);
0085 % Yf = spdiags(Yff, 0, nl, nl) * Cf + spdiags(Yft, 0, nl, nl) * Ct;
0086 % Yt = spdiags(Ytf, 0, nl, nl) * Cf + spdiags(Ytt, 0, nl, nl) * Ct;
0087 
0088 %% build Ybus
0089 Ybus = Cf' * Yf + Ct' * Yt + ...                %% branch admittances
0090         sparse(1:nb, 1:nb, Ysh, nb, nb);        %% shunt admittance

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