Home > matpower7.0 > lib > opf_branch_flow_fcn.m

opf_branch_flow_fcn

PURPOSE ^

OPF_BRANCH_FLOW_FCN Evaluates AC branch flow constraints and Jacobian.

SYNOPSIS ^

function [h, dh] = opf_branch_flow_fcn(x, mpc, Yf, Yt, il, mpopt)

DESCRIPTION ^

OPF_BRANCH_FLOW_FCN  Evaluates AC branch flow constraints and Jacobian.
   [H, DH] = OPF_BRANCH_FLOW_FCN(X, OM, YF, YT, IL, MPOPT)

   Active power balance equality constraints for AC optimal power flow.
   Computes constraint vectors and their gradients.

   Inputs:
     X : optimization vector
     MPC : MATPOWER case struct
     YF : admittance matrix for "from" end of constrained branches
     YT : admittance matrix for "to" end of constrained branches
     IL : vector of branch indices corresponding to branches with
          flow limits (all others are assumed to be unconstrained).
          YF and YT contain only the rows corresponding to IL.
     MPOPT : MATPOWER options struct

   Outputs:
     H  : vector of inequality constraint values (flow limits)
          where the flow can be apparent power, real power, or
          current, depending on the value of opf.flow_lim in MPOPT
          (only for constrained lines), normally expressed as
          (limit^2 - flow^2), except when opf.flow_lim == 'P',
          in which case it is simply (limit - flow).
     DH : (optional) inequality constraint gradients, column j is
          gradient of H(j)

   Examples:
       h = opf_branch_flow_fcn(x, mpc, Yf, Yt, il, mpopt);
       [h, dh] = opf_branch_flow_fcn(x, mpc, Yf, Yt, il, mpopt);

   See also OPF_BRANCH_FLOW_HESS.

CROSS-REFERENCE INFORMATION ^

This function calls: This function is called by:

SOURCE CODE ^

0001 function [h, dh] = opf_branch_flow_fcn(x, mpc, Yf, Yt, il, mpopt)
0002 %OPF_BRANCH_FLOW_FCN  Evaluates AC branch flow constraints and Jacobian.
0003 %   [H, DH] = OPF_BRANCH_FLOW_FCN(X, OM, YF, YT, IL, MPOPT)
0004 %
0005 %   Active power balance equality constraints for AC optimal power flow.
0006 %   Computes constraint vectors and their gradients.
0007 %
0008 %   Inputs:
0009 %     X : optimization vector
0010 %     MPC : MATPOWER case struct
0011 %     YF : admittance matrix for "from" end of constrained branches
0012 %     YT : admittance matrix for "to" end of constrained branches
0013 %     IL : vector of branch indices corresponding to branches with
0014 %          flow limits (all others are assumed to be unconstrained).
0015 %          YF and YT contain only the rows corresponding to IL.
0016 %     MPOPT : MATPOWER options struct
0017 %
0018 %   Outputs:
0019 %     H  : vector of inequality constraint values (flow limits)
0020 %          where the flow can be apparent power, real power, or
0021 %          current, depending on the value of opf.flow_lim in MPOPT
0022 %          (only for constrained lines), normally expressed as
0023 %          (limit^2 - flow^2), except when opf.flow_lim == 'P',
0024 %          in which case it is simply (limit - flow).
0025 %     DH : (optional) inequality constraint gradients, column j is
0026 %          gradient of H(j)
0027 %
0028 %   Examples:
0029 %       h = opf_branch_flow_fcn(x, mpc, Yf, Yt, il, mpopt);
0030 %       [h, dh] = opf_branch_flow_fcn(x, mpc, Yf, Yt, il, mpopt);
0031 %
0032 %   See also OPF_BRANCH_FLOW_HESS.
0033 
0034 %   MATPOWER
0035 %   Copyright (c) 1996-2018, Power Systems Engineering Research Center (PSERC)
0036 %   by Carlos E. Murillo-Sanchez, PSERC Cornell & Universidad Nacional de Colombia
0037 %   and Ray Zimmerman, PSERC Cornell
0038 %
0039 %   This file is part of MATPOWER.
0040 %   Covered by the 3-clause BSD License (see LICENSE file for details).
0041 %   See https://matpower.org for more info.
0042 
0043 %%----- initialize -----
0044 %% define named indices into data matrices
0045 [F_BUS, T_BUS, BR_R, BR_X, BR_B, RATE_A, RATE_B, RATE_C, ...
0046     TAP, SHIFT, BR_STATUS, PF, QF, PT, QT, MU_SF, MU_ST, ...
0047     ANGMIN, ANGMAX, MU_ANGMIN, MU_ANGMAX] = idx_brch;
0048 
0049 %% unpack data
0050 lim_type = upper(mpopt.opf.flow_lim(1));
0051 branch = mpc.branch;
0052 if mpopt.opf.v_cartesian
0053     [Vr, Vi] = deal(x{:});
0054     V = Vr + 1j * Vi;           %% reconstruct V
0055 else
0056     [Va, Vm] = deal(x{:});
0057     V = Vm .* exp(1j * Va);     %% reconstruct V
0058 end
0059 
0060 %% problem dimensions
0061 nb = length(V);         %% number of buses
0062 nl2 = length(il);       %% number of constrained lines
0063 
0064 %% ----- evaluate constraints -----
0065 if nl2 > 0
0066     flow_max = branch(il, RATE_A) / mpc.baseMVA;
0067     if lim_type ~= 'P'      %% typically use square of flow
0068         flow_max = flow_max.^2;
0069     end
0070     if lim_type == 'I'      %% current magnitude limit, |I|
0071         If = Yf * V;
0072         It = Yt * V;
0073         h = [ If .* conj(If) - flow_max;    %% branch current limits (from bus)
0074               It .* conj(It) - flow_max ];  %% branch current limits (to bus)
0075     else
0076         %% compute branch power flows
0077         Sf = V(branch(il, F_BUS)) .* conj(Yf * V);  %% complex power injected at "from" bus (p.u.)
0078         St = V(branch(il, T_BUS)) .* conj(Yt * V);  %% complex power injected at "to" bus (p.u.)
0079         if lim_type == '2'                      %% active power limit, P squared (Pan Wei)
0080             h = [ real(Sf).^2 - flow_max;       %% branch real power limits (from bus)
0081                   real(St).^2 - flow_max ];     %% branch real power limits (to bus)
0082         elseif lim_type == 'P'                  %% active power limit, P
0083             h = [ real(Sf) - flow_max;          %% branch real power limits (from bus)
0084                   real(St) - flow_max ];        %% branch real power limits (to bus
0085         else                                    %% apparent power limit, |S|
0086             h = [ Sf .* conj(Sf) - flow_max;    %% branch apparent power limits (from bus)
0087                   St .* conj(St) - flow_max ];  %% branch apparent power limits (to bus)
0088         end
0089     end
0090 else
0091     h = zeros(0,1);
0092 end
0093 
0094 %%----- evaluate partials of constraints -----
0095 if nargout > 1
0096     if nl2 > 0
0097         %% compute partials of Flows w.r.t. V
0098         if lim_type == 'I'                      %% current
0099             [dFf_dV1, dFf_dV2, dFt_dV1, dFt_dV2, Ff, Ft] = dIbr_dV(branch(il,:), Yf, Yt, V, mpopt.opf.v_cartesian);
0100         else                                    %% power
0101             [dFf_dV1, dFf_dV2, dFt_dV1, dFt_dV2, Ff, Ft] = dSbr_dV(branch(il,:), Yf, Yt, V, mpopt.opf.v_cartesian);
0102         end
0103         if lim_type == 'P' || lim_type == '2'   %% real part of flow (active power)
0104             dFf_dV1 = real(dFf_dV1);
0105             dFf_dV2 = real(dFf_dV2);
0106             dFt_dV1 = real(dFt_dV1);
0107             dFt_dV2 = real(dFt_dV2);
0108             Ff = real(Ff);
0109             Ft = real(Ft);
0110         end
0111 
0112         if lim_type == 'P'
0113             %% active power
0114             [df_dV1, df_dV2, dt_dV1, dt_dV2] = deal(dFf_dV1, dFf_dV2, dFt_dV1, dFt_dV2);
0115         else
0116             %% squared magnitude of flow (of complex power or current, or real power)
0117             [df_dV1, df_dV2, dt_dV1, dt_dV2] = ...
0118               dAbr_dV(dFf_dV1, dFf_dV2, dFt_dV1, dFt_dV2, Ff, Ft);
0119         end
0120 
0121         %% construct Jacobian of "from" and "to" branch flow ineq constraints
0122         dh = [ df_dV1 df_dV2;                   %% "from" flow limit
0123                dt_dV1 dt_dV2 ];                 %% "to" flow limit
0124     else
0125         dh = sparse(0, 2*nb);
0126     end
0127 end

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