Example: Optimal Power Flow

function parse_ac_power_data(filename)
    data = PowerModels.parse_file(filename)
    PowerModels.standardize_cost_terms!(data, order = 2)
    PowerModels.calc_thermal_limits!(data)
    ref = PowerModels.build_ref(data)[:it][:pm][:nw][0]

    arcdict = Dict(a => k for (k, a) in enumerate(ref[:arcs]))
    busdict = Dict(k => i for (i, (k, v)) in enumerate(ref[:bus]))
    gendict = Dict(k => i for (i, (k, v)) in enumerate(ref[:gen]))
    branchdict = Dict(k => i for (i, (k, v)) in enumerate(ref[:branch]))

    return (
        bus = [
            begin
                bus_loads = [ref[:load][l] for l in ref[:bus_loads][k]]
                bus_shunts = [ref[:shunt][s] for s in ref[:bus_shunts][k]]
                pd = sum(load["pd"] for load in bus_loads; init = 0.0)
                gs = sum(shunt["gs"] for shunt in bus_shunts; init = 0.0)
                qd = sum(load["qd"] for load in bus_loads; init = 0.0)
                bs = sum(shunt["bs"] for shunt in bus_shunts; init = 0.0)
                (i = busdict[k], pd = pd, gs = gs, qd = qd, bs = bs)
            end for (k, v) in ref[:bus]
        ],
        gen = [
            (
                i = gendict[k],
                cost1 = v["cost"][1],
                cost2 = v["cost"][2],
                cost3 = v["cost"][3],
                bus = busdict[v["gen_bus"]],
            ) for (k, v) in ref[:gen]
        ],
        arc = [
            (i = k, rate_a = ref[:branch][l]["rate_a"], bus = busdict[i]) for
            (k, (l, i, j)) in enumerate(ref[:arcs])
        ],
        branch = [
            begin
                f_idx = arcdict[i, branch["f_bus"], branch["t_bus"]]
                t_idx = arcdict[i, branch["t_bus"], branch["f_bus"]]
                g, b = PowerModels.calc_branch_y(branch)
                tr, ti = PowerModels.calc_branch_t(branch)
                ttm = tr^2 + ti^2
                g_fr = branch["g_fr"]
                b_fr = branch["b_fr"]
                g_to = branch["g_to"]
                b_to = branch["b_to"]
                c1 = (-g * tr - b * ti) / ttm
                c2 = (-b * tr + g * ti) / ttm
                c3 = (-g * tr + b * ti) / ttm
                c4 = (-b * tr - g * ti) / ttm
                c5 = (g + g_fr) / ttm
                c6 = (b + b_fr) / ttm
                c7 = (g + g_to)
                c8 = (b + b_to)
                (
                    i = branchdict[i],
                    j = 1,
                    f_idx = f_idx,
                    t_idx = t_idx,
                    f_bus = busdict[branch["f_bus"]],
                    t_bus = busdict[branch["t_bus"]],
                    c1 = c1,
                    c2 = c2,
                    c3 = c3,
                    c4 = c4,
                    c5 = c5,
                    c6 = c6,
                    c7 = c7,
                    c8 = c8,
                    rate_a_sq = branch["rate_a"]^2,
                )
            end for (i, branch) in ref[:branch]
        ],
        ref_buses = [busdict[i] for (i, k) in ref[:ref_buses]],
        vmax = [v["vmax"] for (k, v) in ref[:bus]],
        vmin = [v["vmin"] for (k, v) in ref[:bus]],
        pmax = [v["pmax"] for (k, v) in ref[:gen]],
        pmin = [v["pmin"] for (k, v) in ref[:gen]],
        qmax = [v["qmax"] for (k, v) in ref[:gen]],
        qmin = [v["qmin"] for (k, v) in ref[:gen]],
        rate_a = [ref[:branch][l]["rate_a"] for (k, (l, i, j)) in enumerate(ref[:arcs])],
        angmax = [b["angmax"] for (i, b) in ref[:branch]],
        angmin = [b["angmin"] for (i, b) in ref[:branch]],
    )
end

convert_data(data::N, backend) where {names,N<:NamedTuple{names}} =
    NamedTuple{names}(ExaModels.convert_array(d, backend) for d in data)

parse_ac_power_data(filename, backend) =
    convert_data(parse_ac_power_data(filename), backend)

function ac_power_model(filename; backend = nothing, T = Float64)

    data = parse_ac_power_data(filename, backend)

    w = ExaCore(T; backend = backend)

    va = variable(w, length(data.bus);)

    vm = variable(
        w,
        length(data.bus);
        start = fill!(similar(data.bus, Float64), 1.0),
        lvar = data.vmin,
        uvar = data.vmax,
    )
    pg = variable(w, length(data.gen); lvar = data.pmin, uvar = data.pmax)

    qg = variable(w, length(data.gen); lvar = data.qmin, uvar = data.qmax)

    p = variable(w, length(data.arc); lvar = -data.rate_a, uvar = data.rate_a)

    q = variable(w, length(data.arc); lvar = -data.rate_a, uvar = data.rate_a)

    o = objective(w, g.cost1 * pg[g.i]^2 + g.cost2 * pg[g.i] + g.cost3 for g in data.gen)

    c1 = constraint(w, va[i] for i in data.ref_buses)

    c2 = constraint(
        w,
        p[b.f_idx] - b.c5 * vm[b.f_bus]^2 -
        b.c3 * (vm[b.f_bus] * vm[b.t_bus] * cos(va[b.f_bus] - va[b.t_bus])) -
        b.c4 * (vm[b.f_bus] * vm[b.t_bus] * sin(va[b.f_bus] - va[b.t_bus])) for
        b in data.branch
    )

    c3 = constraint(
        w,
        q[b.f_idx] +
        b.c6 * vm[b.f_bus]^2 +
        b.c4 * (vm[b.f_bus] * vm[b.t_bus] * cos(va[b.f_bus] - va[b.t_bus])) -
        b.c3 * (vm[b.f_bus] * vm[b.t_bus] * sin(va[b.f_bus] - va[b.t_bus])) for
        b in data.branch
    )

    c4 = constraint(
        w,
        p[b.t_idx] - b.c7 * vm[b.t_bus]^2 -
        b.c1 * (vm[b.t_bus] * vm[b.f_bus] * cos(va[b.t_bus] - va[b.f_bus])) -
        b.c2 * (vm[b.t_bus] * vm[b.f_bus] * sin(va[b.t_bus] - va[b.f_bus])) for
        b in data.branch
    )

    c5 = constraint(
        w,
        q[b.t_idx] +
        b.c8 * vm[b.t_bus]^2 +
        b.c2 * (vm[b.t_bus] * vm[b.f_bus] * cos(va[b.t_bus] - va[b.f_bus])) -
        b.c1 * (vm[b.t_bus] * vm[b.f_bus] * sin(va[b.t_bus] - va[b.f_bus])) for
        b in data.branch
    )

    c6 = constraint(
        w,
        va[b.f_bus] - va[b.t_bus] for b in data.branch;
        lcon = data.angmin,
        ucon = data.angmax,
    )
    c7 = constraint(
        w,
        p[b.f_idx]^2 + q[b.f_idx]^2 - b.rate_a_sq for b in data.branch;
        lcon = fill!(similar(data.branch, Float64, length(data.branch)), -Inf),
    )
    c8 = constraint(
        w,
        p[b.t_idx]^2 + q[b.t_idx]^2 - b.rate_a_sq for b in data.branch;
        lcon = fill!(similar(data.branch, Float64, length(data.branch)), -Inf),
    )

    c9 = constraint(w, b.pd + b.gs * vm[b.i]^2 for b in data.bus)

    c10 = constraint(w, b.qd - b.bs * vm[b.i]^2 for b in data.bus)

    c11 = constraint!(w, c9, a.bus => p[a.i] for a in data.arc)
    c12 = constraint!(w, c10, a.bus => q[a.i] for a in data.arc)

    c13 = constraint!(w, c9, g.bus => -pg[g.i] for g in data.gen)
    c14 = constraint!(w, c10, g.bus => -qg[g.i] for g in data.gen)

    return ExaModel(w)

end

ac_power_model (generic function with 1 method)

We first download the case file.

using Downloads

case = tempname() * ".m"

Downloads.download(
    "https://raw.githubusercontent.com/power-grid-lib/pglib-opf/dc6be4b2f85ca0e776952ec22cbd4c22396ea5a3/pglib_opf_case3_lmbd.m",
    case,
)

"/tmp/jl_xSREluFe5k.m"

Then, we can model/sovle the problem.

using PowerModels, ExaModels, NLPModelsIpopt

m = ac_power_model(case)
ipopt(m)

"Execution stats: first-order stationary"

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