How to Add Linear Constraints to a Simple Transmission Cross Section in a Standard OPF?

[hygge-coder]

Hi Dr. Zimmerman,
Here is my code,

    function [ om ] = userfcn_case9lineartest(om,mpopt,args)
    mpc = om.get_mpc();
    BranchNum = size(mpc.branch, 1);
    line_indices = [1,4,7]; 
    Line_num = length(line_indices);
    A =sparse(1, line_indices, ones(1, Line_num), 1, BranchNum);
    l=-Inf;
    u=300/mpc.baseMVA;
    om = om.add_lin_constraint('line_flow_limit1', A, l, u,{'Pf'});

I want to add a transmission section constraint by limiting the sum of the transmission power of a few transmission lines of the branch matrix, and then apply this simple linear constraint using add_userfcn(mpc, 'formulation', @userfcn_case9lineartest, []); however Since 'Pf' is not the default variable of matpower, unlike the default variable 'Pg' of matpower which is so easy to use, how should I use the add_var statement to reach the optimization of the branch matrix's transmission power
Kind Regards
hygge

[rdzman]

Does toggle_iflims(), described in Section 7.6.2 in the MATPOWER User's Manual do what you want?

[hygge-coder]

Does toggle_iflims(), described in Section 7.6.2 in the MATPOWER User's Manual do what you want?

Dr. Zimmerman, I understand it can be done, but I would like to become more familiar with MATPOWER by writing this example myself. Could you please guide me on how to use the add_var statement to call Pf data? Thank you.

[rdzman]

As you mention, Pf is not a variable, but it is a linear function of the Va variables. It can be computed using the Bf and Pfinj returned by makeBdc() as Pf = Br * Va + Pfinj.

So as you can see here ...

matpower/lib/toggle_iflims.m

Lines 134 to 160 in 0ea0026

	%% form constraints
	ifidx = unique(iflims(:, 1)); %% interface number list
	nifs = length(ifidx); %% number of interfaces
	Aif = sparse(nifs, n);
	lif = zeros(nifs, 1);
	uif = zeros(nifs, 1);
	for k = 1:nifs
	%% extract branch indices
	br = ifmap(ifmap(:, 1) == ifidx(k), 2);
	if isempty(br)
	error('userfcn_iflims_formulation: interface %d has no in-service branches', k);
	end
	d = sign(br);
	br = abs(br);
	Ak = sparse(1, n); %% Ak = sum( d(i) * Bf(i, :) )
	bk = 0; %% bk = sum( d(i) * Pfinj(i) )
	for i = 1:length(br)
	Ak = Ak + d(i) * Bf(br(i), :);
	bk = bk + d(i) * Pfinj(br(i));
	end
	Aif(k, :) = Ak;
	lif(k) = iflims(k, 2) / baseMVA - bk;
	uif(k) = iflims(k, 3) / baseMVA - bk;
	end
	%% add interface constraint
	om.add_lin_constraint('iflims', Aif, lif, uif, {'Va'}); %% nifs

... we use that to build up the constraint matrices and bounds as functions of Va.

[hygge-coder]

Thank you, Dr. Zimmerman. I have resolved the issue, thanks to your assistance. I appreciate your help.