windfarm/mip.py

import numpy as np
import pandas as pd
from scipy.spatial import distance_matrix
from scipy.sparse.csgraph import minimum_spanning_tree
from collections import defaultdict
import random

try:
    import pulp
except ImportError:
    pulp = None


def design_with_mip(
    turbines,
    substation,
    cable_specs=None,
    voltage=66000,
    power_factor=0.95,
    system_params=None,
    max_clusters=None,
    time_limit=300,  # seconds
    evaluate_func=None,
    total_invest_func=None,
    get_max_capacity_func=None,
):
    """
    使用混合整数规划(MIP)优化集电线路布局
    :param turbines: 风机DataFrame
    :param substation: 升压站坐标
    :param cable_specs: 电缆规格
    :param system_params: 系统参数（用于NPV计算）
    :param max_clusters: 最大簇数，默认基于功率计算
    :param time_limit: 求解时间限制（秒）
    :param evaluate_func: 评估函数
    :param total_invest_func: 总投资计算函数
    :param get_max_capacity_func: 获取最大容量函数
    :return: 连接列表和带有簇信息的turbines
    """
    if pulp is None:
        print(
            "WARNING: PuLP library not available. MIP optimization skipped, falling back to MST."
        )
        from main import design_with_mst

        connections = design_with_mst(turbines, substation)
        return connections, turbines

    if get_max_capacity_func:
        max_mw = get_max_capacity_func(cable_specs, voltage, power_factor)
    else:
        max_mw = 100.0  # 默认值
    total_power = turbines["power"].sum()
    if max_clusters is None:
        max_clusters = int(np.ceil(total_power / max_mw))
    n_turbines = len(turbines)

    print(
        f"MIP Model Setup: n_turbines={n_turbines}, max_clusters={max_clusters}, max_mw={max_mw:.2f} MW"
    )

    # 预计算距离矩阵
    all_coords = np.vstack([substation, turbines[["x", "y"]].values])
    dist_matrix_full = distance_matrix(all_coords, all_coords)

    # MIP 模型
    prob = pulp.LpProblem("WindFarmCollectorMIP", pulp.LpMinimize)

    # 创建所有变量和约束的辅助函数
    def assign_var(i, k):
        return pulp.LpVariable(f"assign_{i}_{k}", cat="Binary")

    def cluster_var(k):
        return pulp.LpVariable(f"cluster_{k}", cat="Binary")

    # 目标函数：最小化使用的簇数（越少回路，成本越低）
    prob += pulp.lpSum([cluster_var(k) for k in range(max_clusters)])

    # 约束1：每个风机分配到一个簇
    for i in range(n_turbines):
        prob += pulp.lpSum([assign_var(i, k) for k in range(max_clusters)]) == 1

    # 约束2：簇功率约束（允许20%过载，增加求解器灵活性）
    for k in range(max_clusters):
        cluster_power = pulp.lpSum(
            [turbines.iloc[i]["power"] * assign_var(i, k) for i in range(n_turbines)]
        )
        prob += cluster_power <= max_mw * 1.2 * cluster_var(k)

    # 约束3：如果簇未使用，则无分配
    for k in range(max_clusters):
        for i in range(n_turbines):
            prob += assign_var(i, k) <= cluster_var(k)

    print(
        f"MIP Model: {len(prob.variables())} variables, {len(prob.constraints)} constraints"
    )

    # 求解
    solver = pulp.PULP_CBC_CMD(timeLimit=time_limit, msg=0, warmStart=False)
    print("MIP: Starting to solve...")
    status = prob.solve(solver)
    print(
        f"MIP: Solver status={pulp.LpStatus[prob.status]}, Objective value={pulp.value(prob.objective):.4f}"
    )

    if pulp.LpStatus[prob.status] != "Optimal":
        print(
            f"MIP solver status: {pulp.LpStatus[prob.status]}, solution not found, falling back to MST"
        )
        print(f"Model infeasibility check:")
        print(
            f"Total power: {turbines['power'].sum():.2f} MW, Max cluster capacity: {max_mw:.2f} MW"
        )
        print(f"Number of clusters: {max_clusters}, Number of turbines: {n_turbines}")

        from main import design_with_mst

        connections = design_with_mst(turbines, substation)
        return connections, turbines

    # 提取结果：确定每个簇
    cluster_assign = [-1] * n_turbines
    active_clusters = []
    for k in range(max_clusters):
        if pulp.value(cluster_var(k)) > 0.5:
            active_clusters.append(k)

    # 将每个未分配的风机分配到最近的活跃簇
    for i in range(n_turbines):
        assigned = False
        for k in active_clusters:
            if pulp.value(assign_var(i, k)) > 0.5:
                cluster_assign[i] = k
                assigned = True
                break
        if not assigned and active_clusters:
            # 如果没有分配，分配到距离最近的活跃簇
            dists = [dist_matrix_full[0, i + 1] for k in active_clusters]
            cluster_assign[i] = active_clusters[np.argmin(dists)]

    # 构建连接
    clusters = defaultdict(list)
    for i, c in enumerate(cluster_assign):
        clusters[c].append(i)

    connections = []
    for c, members in clusters.items():
        if len(members) == 0:
            continue
        coords = turbines.iloc[members][["x", "y"]].values
        if len(members) > 1:
            dm = distance_matrix(coords, coords)
            mst = minimum_spanning_tree(dm).toarray()
            for i in range(len(members)):
                for j in range(len(members)):
                    if mst[i, j] > 0:
                        connections.append(
                            (
                                f"turbine_{members[i]}",
                                f"turbine_{members[j]}",
                                mst[i, j],
                            )
                        )
        # 连接到升压站：选择簇中距离升压站最近的风机
        dists = [dist_matrix_full[0, m + 1] for m in members]
        closest = members[np.argmin(dists)]
        connections.append((f"turbine_{closest}", "substation", min(dists)))

    turbines["cluster"] = cluster_assign
    print(
        f"MIP optimization completed successfully, {len(connections)} connections generated"
    )
    return connections, turbines