User defined constraints, variables and costs - most.build_model = false; most.solve_model = true;

[lordleoo]

MOST does not support adding custom user-defined constraints, yet.
Indeed MATPOWER allows that through the "add_userfcn" function, but MOST doesn't

A manual work-around is:

1. Building the MOST model, without solving it. that is: set the mpoptions to:
   build_model = true; solve_model = false;

2. Use the functions:
   build the A, L, U and VS variables to add a new constraint; using the functions: init_indexed_name and add_lin_constraint. To understand how they work, you need to take a deep look at the MOST.m file

3. set build_most = false; solve_most = true; and call MOST a second time, with your modified model as the input to MOST

now the bug is here:
line 359 of MOST.m has this if statement:
if mpopt.most.build_model
.
.
.
line 553: om = opt_model
< the remaining some-1000 lines >
end

There is no "ELSE" statement.
the OPT_MODEL was declared the first time inside the if-statement. if for some-reason the program didn't enter this IF statement, then an OM=OPT_MODEL does not exist.
you can not pass an existing (readily built) OM to MOST. The input arguments to MOST are: (MDI) and (MPOPT).

Therefore, there is no way to make use of your modified OM model.
The combination: build_most = false; solve_most = true would throw an error.

The work around is simple though, right before the end of this if-statement, add a single line:
.
.
.
else; om = mdi.om;
end

Note:
you have to add you new constraints and variables with the commands:
init_indexed_name and add_lin_constraint.

modifying the structure: mdi.QP.A, mdi.QP.l, mdi.QP.u
would not help, because they are over-written inside MOST.m

The owners of MOST.m may want to change that kind of behavior, because generating mdi.QP takes a lot of time for large models.

a messy workaround is to build your own A, l and u and call the solver manually and outside most.m, that is:

if UC
[mdo.QP.x, mdo.QP.f, mdo.QP.exitflag, mdo.QP.output, mdo.QP.lambda ] = ...
miqps_matpower( mdi.QP.H, mdi.QP.C, mdi.QP.A, ...
mdi.QP.l, mdi.QP.u, mdi.QP.xmin, mdi.QP.xmax, ...
[], mdi.QP.vtype, mdo.QP.opt);
else
[mdo.QP.x, mdo.QP.f, mdo.QP.exitflag, mdo.QP.output, mdo.QP.lambda ] = ...
qps_matpower( mdi.QP.H, mdi.QP.C, mdi.QP.A, ...
mdi.QP.l, mdi.QP.u, mdi.QP.xmin, mdi.QP.xmax, ...
[], mdo.QP.opt);
end

[rdzman]

See MATPOWER/most#6 and MATPOWER/most#8.