刘轩(1995),男,硕士在读,研究方向为振动控制及振动能量收集(E-mail:
王越(1996),男,硕士在读,研究方向为基于振动能量收集的自供电无线传感器设计
吴义鹏(1986),男,博士,副教授,研究方向为自供电电源管理单元的设计及开发
低功耗自供电设备随着物联网技术的不断进步逐渐成为发展主流。基于超级电容搭建的储能模块可应用于低功耗自供电智能设备, 但超级电容的自放电特性会导致存储能量的损失及端电压的下降,不利于低功耗自供电设备的功耗管理及测量。文中建立了所述储能模块的等效可变漏电阻模型,通过实验确定了等效模型中的相关参数并通过Matlab/Simulink数值仿真软件对该储能模块的自放电过程进行了分析。最后对仿真结果进行了分段线性化拟合以便于后续测试误差修正或数学计算,并使用拟合后的等效电路模型预测了自放电期间储能模块的电压变化。该电压变化值与实验所测结果吻合,验证了模型的有效性,为低功耗自供电设备的电源管理单元设计及功耗测量等奠定了基础。
Low-power self-powered equipment has gradually become the mainstream of development with the continuous advancement of Internet of Things technology. Energy storage module based on supercapacitors can be applied to low-power self-powered smart devices, but the self-discharge characteristics of supercapacitors will cause the loss of stored energy and the drop in terminal voltage, which is not conducive to the power consumption of low-power self-powered devices management and measurement. A variable leakage resistance model which is used to analyze the introduced energy storage module is established in this paper. The relevant parameters in the equivalent model are determined through experiments and the self-discharge process of the energy storage module is analyzed by Matlab/Simulink. Finally, the simulation results are fitted with piecewise linearization in order to facilitate subsequent test error correction or mathematical calculations in the future, and the fitted equivalent circuit model is used to predict the voltage of the energy storage module during self-discharge. The voltage variation of the energy storage module predicted by the equivalent model fits well with the experimental data. The work in this paper completes the basical steps for the designation of power management unit and the power consumption measurement in low-power and energy autonomous devices.
低功耗及自供电是物联网时代的发展主流。物联网是互联网络与传感器网络的融合,通过各种传感器实时采集信息并通过各类可能的网络接入,实现物与物、物与人的泛在连接以及对物品和过程的智能化感知、识别和管理。感知层是物联网的核心,通过传感网络获取环境信息[
尽管可充电电池容量高且泄漏率低,但其循环寿命会限制传感器节点的寿命[
超级电容的等效电路模型可模拟并预测自放电现象,其原理是用电路来等效超级电容的内部结构,复杂度低且精度好。其中最简单的是标准R-C模型[
文中设计了基于超级电容器单体且可应用于低功耗自供电设备的储能模块,参考VLR模型建立了该储能模块的等效VLR电路模型,分析了储能模块自放电现象并进行端电压变化预测,最后通过实验验证了该模型的精确性。
对于采用高输出阻抗的环境能量采集器,其电源管理单元一般选用降压型的稳压器,使单元输出如3.3 V,3.6 V之类的稳定直流电压。亚德诺半导体技术公司提供的电源管理芯片LTC3588-1可为上述应用提供较完美的解决方案。LTC3588-1的最大输入电压为20 V,输出电压有1.8 V,2.5 V,3.3 V,3.6 V。考虑到储能模块可能的应用范围,文中采用中国台湾CDA公司的CXHP系列额定电压2.7 V,标称容量0.5 F的10个超级电容器单体串联组成储能模块。其理论额定电压27 V,标称容量0.05 F。但考虑到模块的充放电寿命以及超级电容器单体一致性较差的问题,为提高安全系数,增加安全余量,该模块的实际工作电压不应超过20 V。
实验原理如
实验原理
Principle of the experiment
储能模块由超级电容器单体串联组成,因此仍基于单体的VLR模型[
可变漏电阻模型
The model of variable leakage resistance
初始电压变化量Δ
Schematic diagram of initial voltage variation Δ
综上所述,
充电-电荷再分配状态下储能模块电压
Voltage of energy storage module in charging-redistribution state
需要指出的是,
根据多次实验测试结果,
VLR模型中储能模块的相关参数值
Parameters of the energy storage module in VLR model
实验编号 | |||||
1 | 13.255 2 | 0.047 1 | 0.001 47 | 39 221.93 | 0.006 119 |
2 | 13.729 9 | 0.046 3 | 0.001 38 | 40 722.37 | 0.005 894 |
3 | 13.210 8 | 0.048 4 | 0.001 60 | 40 371.06 | 0.005 945 |
4 | 13.775 1 | 0.045 2 | 0.001 66 | 42 465.87 | 0.005 652 |
5 | 13.533 6 | 0.052 2 | 0.001 64 | 38 659.08 | 0.006 208 |
平均值 | 13.500 9 | 0.047 84 | 0.001 55 | 40 288.06 | 0.005 963 |
用于分析自放电过程的等效电路模型见
自放电分析等效电路
The equivalent circuit of self-discharge analysis
使用直流稳压电源将储能模块充电至20 V,断开电源并在未来3 h内测量储能模块开路电压,自放电过程中储能模块端电压即
自放电状态中储能模块电压
Voltage of energy storage module in self-discharge state
3个分支电流的关系可以通过基尔霍夫电流定律确定,如式(4)所示。
通过确定
其中,主分支电流
微分电容
第二分支电流
联立式(4)—式(9),将建立自放电电流
将储能模块3 h内测得的电压变化值
The relationship between
The relationship between
为了更直观地描述和分析
将
自放电导致的实验电压与其预测电压
Experimental and the calculated voltages caused by self-discharge phenomenon
文中首先搭建了一个基于超级电容器单体的储能模块,建立了用于研究模块自放电现象的VLR模型,并对模型相关参数进行了测试。借助实验测试获得的储能模块自放电电压数据,采用数值仿真软件计算得到模块可变漏电阻值,同时对其进行分段线性化拟合。研究结果可以计算预测基于超级电容器搭建的储能模块的自放电电压,为后续供电设备的电源管理单元设计、功耗优化甚至测试奠定了基础。
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