function Sbus = makeSbus(baseMVA, bus, gen)%MAKESBUS   Builds the vector of complex bus power injections.%   Sbus = makeSbus(baseMVA, bus, gen) returns the vector of complex bus%   power injections, that is, generation minus load. Power is expressed%   in per unit.%   MATPOWER%   $Id: makeSbus.m,v 1.4 2004/08/23 20:56:41 ray Exp $%   by Ray Zimmerman, PSERC Cornell%   Copyright (c) 1996-2004 by Power System Engineering Research Center (PSERC)%   See http://www.pserc.cornell.edu/matpower/ for more info.%% constantsj = sqrt(-1);%% define named indices into bus, gen matrices[PQ, PV, REF, NONE, BUS_I, BUS_TYPE, PD, QD, GS, BS, BUS_AREA, VM, ...    VA, BASE_KV, ZONE, VMAX, VMIN, LAM_P, LAM_Q, MU_VMAX, MU_VMIN] = idx_bus;[GEN_BUS, PG, QG, QMAX, QMIN, VG, MBASE, ...    GEN_STATUS, PMAX, PMIN, MU_PMAX, MU_PMIN, MU_QMAX, MU_QMIN] = idx_gen;%% generator infoon = find(gen(:, GEN_STATUS) > 0);      %% which generators are on?gbus = gen(on, GEN_BUS);                %% what buses are they at?%% form net complex bus power injection vectornb = size(bus, 1);ngon = size(on, 1);Cg = sparse(gbus, [1:ngon]', ones(ngon, 1), nb, ngon);  %% connection matrix                                                        %% element i, j is 1 if                                                        %% gen on(j) at bus i is ONSbus =  ( Cg * (gen(on, PG) + j * gen(on, QG)) ...  %% power injected by generators            - (bus(:, PD) + j * bus(:, QD)) ) / ... %% plus power injected by loads        baseMVA;                                    %% converted to p.u.return;