功率阈值逻辑

功率阈值逻辑

概述

本节介绍如何设计和实现功率阈值逻辑，实现对设备能耗的智能监控。学习完成后，您将能够：

• 设计多级功率阈值架构
• 实现阈值触发和自动响应
• 结合时间条件优化控制策略
• 构建灵活的阈值配置管理系统

Threshold Architecture

功率值
▲
│  CRITICAL: 2000W ──┼────────────────────── 过载保护，立即断电
│                     │
│  WARNING: 1500W ───┼──────────────── 告警通知，关注负载
│                     │
│  NORMAL: 800W ─────┼─────────── 正常运行范围
│                     │
│  LOW: 50W ─────────┼───── 待机/低功耗
│                     │
│  OFF: 5W ──────────┼─ 设备关闭/断电
│
└──────────────────────────────────────────► 时间

Multi-Level Threshold Implementation

配置式阈值管理

// Function: 多级阈值检测引擎
// 支持灵活的阈值配置

// 阈值配置 (可从 Flow/Global Context 动态加载)
var thresholds = context.get("powerThresholds") || {
    device: {
        "shellyplus1pm-LINE1": {
            critical: { max: 2000, action: "shutdown" },
            warning: { max: 1500, action: "notify" },
            normal: { min: 50, max: 1500 },
            standby: { max: 50 }
        },
        "tasmota-socket1": {
            critical: { max: 2500, action: "shutdown" },
            warning: { max: 2000, action: "notify" },
            normal: { min: 100, max: 2000 },
            standby: { max: 100 }
        }
    },
    default: {
        critical: { max: 2000, action: "shutdown" },
        warning: { max: 1500, action: "notify" },
        normal: { min: 10, max: 1500 },
        standby: { max: 10 }
    }
};

// 获取设备 ID
var deviceId = msg.payload.device || "unknown";

// 获取当前功率
var power = msg.payload.power;
if (power === undefined || power === null) {
    return null;
}

// 获取设备阈值配置
var deviceThreshold = thresholds.device[deviceId] || thresholds.default;

// 获取上次状态
var lastState = context.get("powerState_" + deviceId) || "unknown";

// 判断当前状态
var currentState;
if (power > deviceThreshold.critical.max) {
    currentState = "critical";
} else if (power > deviceThreshold.warning.max) {
    currentState = "warning";
} else if (power >= deviceThreshold.normal.min) {
    currentState = "normal";
} else if (power >= deviceThreshold.standby.max) {
    currentState = "standby";
} else {
    currentState = "off";
}

// 状态变化检测
var stateChanged = (currentState !== lastState);

if (stateChanged) {
    context.set("powerState_" + deviceId, currentState);
    node.status({
        fill: currentState === "critical" ? "red" :
              currentState === "warning" ? "yellow" : "green",
        shape: "dot",
        text: currentState
    });
}

// 构建结果
msg.payload = {
    device: deviceId,
    power: power,
    state: currentState,
    state_changed: stateChanged,
    previous_state: lastState,
    threshold_config: deviceThreshold,
    action_required: currentState === "critical" || currentState === "warning",
    timestamp: Date.now()
};

// 触发告警的附加信息
if (currentState === "critical" && deviceThreshold.critical.action === "shutdown") {
    msg.shutdown = true;
}
if (currentState === "warning") {
    msg.alert = true;
}

return msg;

Time-Aware Thresholds

根据时间段调整阈值

// Function: 时间感知的阈值调整

var now = new Date();
var hour = now.getHours();

// 按时间段调整阈值 (白天/夜晚)
var timeConfig = {
    // 工作时间 (08:00-20:00): 正常阈值
    workday: {
        warning: 2000,
        critical: 2500
    },
    // 非工作时间 (20:00-08:00): 更敏感的阈值
    night: {
        warning: 500,     // 夜间设备应低功耗
        critical: 1000    // 超过 1000W 可能异常
    }
};

// 判断当前时段
var isNight = (hour >= 20 || hour < 8);
var config = isNight ? timeConfig.night : timeConfig.workday;

var power = msg.payload.power;

var state = "normal";
if (power > config.critical) {
    state = "critical";
} else if (power > config.warning) {
    state = "warning";
}

// 夜间模式下异常更敏感
if (isNight && state === "warning") {
    // 夜间告警升级
    msg.severity = "high";
} else {
    msg.severity = "normal";
}

msg.payload = {
    power: power,
    state: state,
    period: isNight ? "night" : "workday",
    thresholds: config,
    severity: msg.severity,
    timestamp: Date.now()
};

return msg;

Cumulative Consumption Control

基于累计电量的控制

// Function: 累计电量控制
// 当日用电量超过设定值时触发

var todayKwh = msg.payload.today_kwh || 0;
var deviceId = msg.payload.device || "unknown";

// 每日用电量上限配置 (kWh)
var DAILY_LIMIT = {
    "shellyplus1pm-LINE1": 10,
    "shellyplus1pm-LINE2": 5,
    "default": 8
};

var limit = DAILY_LIMIT[deviceId] || DAILY_LIMIT.default;

// 检测日期变更，重置累计
var today = new Date().toISOString().split('T')[0];
var lastDate = context.get("lastDate_" + deviceId);

if (lastDate !== today) {
    context.set("lastDate_" + deviceId, today);
    context.set("dailyAlert_" + deviceId, false);
}

if (todayKwh > limit) {
    var alreadyAlerted = context.get("dailyAlert_" + deviceId) || false;

    if (!alreadyAlerted) {
        context.set("dailyAlert_" + deviceId, true);

        msg.payload = {
            device: deviceId,
            type: "daily_limit",
            current_kwh: todayKwh,
            limit_kwh: limit,
            exceeded_by: (todayKwh - limit).toFixed(2),
            message: "设备 " + deviceId + " 今日用电量 " + todayKwh +
                     "kWh 已超过限额 " + limit + "kWh",
            timestamp: Date.now()
        };

        return msg;
    }
}

return null;  // 未超过限额或已告警

Dynamic Threshold Configuration

通过 Node-RED Dashboard 动态调整阈值

// Function: 接收 Dashboard 滑条/输入组件传来的阈值更新
// 输入: {"device":"shellyplus1pm-LINE1","threshold":"warning","value":1800}

var config = msg.payload;
if (config.device && config.threshold && config.value) {
    var thresholds = context.get("powerThresholds") || {};

    if (!thresholds.device) {
        thresholds.device = {};
    }
    if (!thresholds.device[config.device]) {
        thresholds.device[config.device] = {};
    }

    thresholds.device[config.device][config.threshold] = {
        max: Number(config.value),
        action: config.threshold === "critical" ? "shutdown" : "notify"
    };

    context.set("powerThresholds", thresholds);

    node.log("Threshold updated: " + config.device +
             " " + config.threshold + " = " + config.value + "W");

    msg.payload = {
        status: "ok",
        message: "阈值已更新"
    };

    return msg;
}

验证

# 1. 模拟功率过载
mosquitto_pub -t "tele/tasmota/socket1/SENSOR" \
  -m '{"ENERGY":{"Power":2100,"Voltage":223,"Current":9.4}}'

# 2. 检查是否触发 critical 状态和 shutdown 动作
# Node-RED Debug 面板应显示 state: "critical"

# 3. 恢复模拟正常值
mosquitto_pub -t "tele/tasmota/socket1/SENSOR" \
  -m '{"ENERGY":{"Power":800,"Voltage":223,"Current":3.6}}'

# 4. 状态应恢复为 normal

Common Customer Questions

Q1: 阈值设置多大合适？

取决于设备类型和场景：

• 照明回路: 500-1000W
• 办公设备: 1500-2000W
• 空调/电机: 2000-3500W
• 建议先采集一周数据后根据实际值调整阈值

Q2: 如何避免功率瞬态波动导致误触发？

在 Function 中引入去抖逻辑：连续 N 次超过阈值才触发动作，或使用阈值持续时间判定（如超过阈值持续 30 秒）。

最佳实践

✅ 推荐做法:

• 使用多级阈值（正常/警告/严重）分级响应
• 结合时间条件调整阈值灵敏度
• 实现去抖逻辑避免瞬态误触发
• 阈值配置可从 Dashboard 动态调整

❌ 避免做法:

• 单一固定阈值不适用于所有场景
• 忽略设备启动电流（瞬时峰值）
• 无去抖逻辑导致频繁告警
• 阈值硬编码在 Function 中

Summary

1. 多级阈值提供 normal/warning/critical 分级响应
2. 时间感知根据白天/夜间调整阈值灵敏度
3. 累计电量控制防止单日过度用电
4. 去抖逻辑避免瞬态波动误触发
5. 阈值可通过 Node-RED Dashboard 动态调整

References

• Node-RED Context 文档
• Node-RED Dashboard 文档