【作者】 赵清华；

【导师】 王华奎；

【作者基本信息】 太原理工大学 ， 电路与系统， 2010， 博士

【摘要】 无线传感器网络具有多跳性、能够自组织网络、无需基础设施支持的优点,在军事、民用领域都有着广阔的应用前景。然而,传感器网络节点数目庞大,分布区域广、部署环境复杂或危险,无法利用人工更换电池的方式来补充电能。所以解决无线传感器网络能量问题并对能量进行充分、合理的利用是我们研究的重点。本文的主要工作如下。1.采用低功耗的无线收发射频芯片nRF401和AT89C2051-12PU单片机,研制出一种体积小、成本低的无线传感器节点。该节点上携带有照度传感器和温度传感器,能够获取环境中的照度信息和温度信息,并测试出无线传感器节点在不同条件下的传输距离。结合无线传感器节点研制过程中遇到的困难,总结出无线传感器节点在设计和制作过程中应注意的问题。2.分析了太阳能电池及光伏系统的特性,发现光伏电池工作在最大功率点时,输出性能是最好的,如果能使光伏电池一直工作在最大功率点附近,则能更高效地给传感器节点供能。在设计中引进了最大功率点跟踪算法。3.分析了超级电容器和锂离子电池的原理及特性,并对超级电容器和锂离子电池混合使用的可行性进行了分析。分析结果表明将锂离子电池与超级电容器混合使用,可以减小锂离子电池的输出电流和充放电次数,降低内部损耗,延长放电时间,延缓失效进程。超级电容器和锂离子电池混合使用,可以扬长避短,优势互补,形成高容量、高功率、长寿命的混合储能系统,将扩展锂离子电池和超级电容器的应用空间。4.分析了太阳能光伏电池的温度效应。发现太阳能电池中80%的光能转化为热能,20%的光能转化为电能。同时发现太阳能电池的温度升高影响其本身的工作效率。为了更充分地利用太阳能,减少温度升高对太阳能电池的影响,构建了光伏-温差混合能量管理系统。温差电池吸收光伏电池产生的热能并转化为电能,这不仅降低了光伏电池的温度,而且提高了光伏电池的输出电压和峰值功率。给系统增加电能的产出。在相同条件下,通过理论和实验验证,光伏电池单能量转化子系统与光伏-温差双能量转化子系统相比较,混合能源中光伏电池的背面温度最大可降低13℃;光伏电池的开路电压最大升高了304mV;光伏电池的效率提高了5.2%。充分体现了混合能源的优势,提高了光伏电池的发电效率并实现余热利用。因此,光伏-温差混合能量管理系统能为节点带来更多能量。但温差电池本身产生电压并不高,除了夏天之外,在一年的其它季节,温差电池输出的电压很难达到升压电路的启动工作电压,如果用温差电池直接向超级电容器充电,超级电容器中存储的电量也不会很多,为了尽可能多的利用能量,设计中采用了超低压升压技术。5.通过对太阳能光伏电池输出特性的分析研究,发现在太阳能电池遇到多云天气或每天的早晨、黄昏,光照强度较低,输出功率低,虽然无法直接为传感器节点供电,但这部分能量持续的时间还比较长,如果不加以利用,必然是一种浪费。提出了太阳能光伏电池不同功率分段利用的思想,设计了太阳能光伏电池的能量高效收集电路。实验结果表明,应用了太阳能电池功率分段思想能够更有效地利用环境能量,提高了太阳能光伏电池的使用效率。6.针对所设计的四代能量管理系统中均存在一个问题:能耗较高。设计了节能的能量管理系统。通过对单片机进行控制,使超级电容器仅仅在放电的时间内单片机开始工作,超级电容器放电完毕单片机停止工作,从而降低能量管理系统的能耗。7.针对温差电池输出功率较低的缺点,研制出四块太阳能光伏电池为无线传感器节点供电的能量管理系统,将无线传感器节点周围的太阳能得以充分利用。在标准光强下,测试了基于传感器节点的单一能量管理系统和混合能量管理系统的整体性能,实验结果表明,所设计的能量管理系统各个部分能够协调工作,整个系统输出稳定,能够保证传感器节点的正常工作。更多还原

【Abstract】 Wireless sensor network has the virtues of multi-hop, self-organization and infrastructureless, so it can offer many useful applications in military and civil field. However, so many tiny sensor nodes are distributed widely at the dangerous or complex topography, that there is no way to change batteries to supply energy. So,to solve energy problems in wireless sensor networks and to use energy fully and rationaly is the focus of our research.The main contents are listed as follows:1. Using low-power wireless RF transceiver chip nRF401 and AT89C2051-12PU single-chip microcomputer (SCM), there developed small, low-cost wireless sensor nodes, which carry a light sensor and temperature sensor that are able to obtain the information environment illumination and temperature information, and to test out the transmission distance under different conditions. Combined with the difficulties in the process of researching, some problems that should be paid attention in designing and producing the wireless sensor nodes have been concluded.2. After analyzing the characteristics of the solar cells and photovoltaic system, it is found that when around the point of maximum power, the photovoltaic shows best output characteristics. If possible to make the photovoltaic working around the point of the point of maximum power, it can supply energy to sensor nodes more efficiently. In the design maximum power point tracking algorithm has been introducted.3. The principle and characteristics of ultra-capacitors and lithium-ion batteries and the feasibility of using them together are analyzed. The results show that if the lithium-ion batteries and ultra-capacitors are mixed used, the frequency of the lithium-ion battery’s’charging and discharging, the output current and the internal loss will be reduced, the discharge time will be extended, and the process of failure will slow down. The mix can avoid weaknesses, and complete each other to form a high-capacity, high power, long-life hybrid energy storage system. The application space of lithium-ion battery and ultracapacitor will be extended.4. The temperature effect of photovoltaic is analyzed. It was found that the solar cells convert 80% of light to heat, 20% of the light energy into electrical energy. The temperature of solar cells affects their own productivity. To utilize solar energy more fully, to reduce the temperature’s affected to the solar cells. A photovoltaic - thermal hybrid power management system was constructed. The thermoelectric batteries absorb heat which are generated by photovoltaic cells and converted it into electricity; it will not only reduce the temperature of photovoltaic, but also increase the output voltage and the peak power to increase the power output of the system. Through the theoretical and experimental validation, compared to a single photovoltaic energy conversion subsystem, in the photovoltaic - thermal energy conversion subsystem, the back temperature of photovoltaic can decrease 13℃at most; the largest voltage in the open circuit of photovoltaic increase 304mV; the efficiency of photovoltaic are improved by 5.2% under the same conditions. The advantages of energy mix are fully embodied, the efficiency of photovoltaic are improved compared to the generate electricity and waste heat utilization is achieved. Therefore, the photovoltaic - thermal hybrid energy management system can bring more energy to the node. But the voltage that the thermoelectric battery produced is not high, unless in the summer, the output voltage of the battery temperature is difficult to achieve the step-up circuit voltage to start operating, so if the super capacitor charged by the thermoelectric battery directly, the super-capacitors will store a little power. In the design, the ultra-low-voltage boost technology was used in order to use the energy as much as possible.5. Through the analysis of the solar cells output characteristics, it is found that when in daily days, or at dawn and sunset of everyday, light intensity and output power are much lower. Although it’s not possible to supply energy to the sensor nodes directly, this part of energy lasts quite long time. Without efficient usage, it is sure to cause a huge waste. An idea that solar cells use different power has been proposed. A circuit in which the solar cells collect energy efficiently has been designed. Experimental results show that the application of solar cells power sub-thought takes fuller advantages of environmental energy and improves the utilization efficiency of solar photovoltaic cells. 6. There exists a common problem of high energy consumption in the designed four-generation energy management system.. Aimed at this problem, an energy-saving energy management system is designed. Through controlling the SCM to make it start working within the discharge time of the ultracapacitor and stop as the the discharge is completed. Thus the energy consumption of energy management systems is successfully reduced.7. Aimed at the shortcomings of the thermotelecric battery’s low output power, a energy management system which contains four photovoltaic to provide energy for wireless sensor nodes is designed. Thus making full use of the solar energy around the nodes.Under standard light intensity, tests of both the single and hybrid management systems’overfall performance have been made (both two systems are based on sensor nodes). Experimental results show that every part of the designed system coordinate the work, the system’s output is stable, and the system can guarantee the sensor nodes work normally.更多还原