The topology control strategies of wireless sensor networks are very important for reducing the energy consumption of sensor nodes and prolonging the life-span of networks. In this paper, we put forward a minimum-ener...The topology control strategies of wireless sensor networks are very important for reducing the energy consumption of sensor nodes and prolonging the life-span of networks. In this paper, we put forward a minimum-energy path-preserving topology control （MPTC） algorithm based on a concept of none k-redundant edges. MPTC not only resolves the problem of excessive energy consumption because of the unclosed region in small minimum-energy communication network （SMECN）, but also preserves at least one minimum-energy path between every pair of nodes in a wireless sensor network. We also propose an energy-efficient reconfiguration protocol that maintains the minimum-energy path property in the case where the network topology changes dynamically. Finally, we demonstrate the performance improvements of our algorithm through simulation.展开更多
The full bridge zero voltage zero current switching （ FB-ZVZCS ） , which could adjust the output power by keeping the duty ratio of lagging leg constant and changing the duty ratio of leading leg, was a common circu...The full bridge zero voltage zero current switching （ FB-ZVZCS ） , which could adjust the output power by keeping the duty ratio of lagging leg constant and changing the duty ratio of leading leg, was a common circuit of soft switching arc welding inverter power source. However, when the duty ratio of leading leg was reduced to zero, the output power stayed the constant value instead of becoming zero. The working status and waveforms of some major parameters were studied in this paper while the duty ratio of leading leg was zero. It was concluded that the minimum output power of soft switching inverter was related to the charging voltage of paraUel capacitors, and the output power also could be reduced by reducing the duty ratio of lagging leg. A novel two-stage continuous PWM control method that could switch working-mode between full bridge and half bridge was put forward in this paper. This kind of control method could further reduce the output power of soft switching inverter in order to meet the requirement of low heat input of sheet metal welding.展开更多
具备虚拟同步发电机(virtual synchronous generator,VSG)调节能力的统一潮流控制器(unified power flow controller,UPFC)可以为电网提供额外的惯性和阻尼,提高UPFC在新能源输发电领域的竞争力。然而不匹配的换流器输出电压偏移角会增...具备虚拟同步发电机(virtual synchronous generator,VSG)调节能力的统一潮流控制器(unified power flow controller,UPFC)可以为电网提供额外的惯性和阻尼,提高UPFC在新能源输发电领域的竞争力。然而不匹配的换流器输出电压偏移角会增加设备制造成本和额外功率损耗。阐述了VSG型的统一潮流控制器系统,在讨论电压偏移角的大小对UPFC视在功率以及设计参数的影响后,分析了3种典型的电压偏移角控制方案的参数设计。提出了最小容量的参数设计方案以及在上述参数指标限制下以最小功率为目标的偏移角控制策略,并利用数学统计软件(statistical product and service solutions,SPSS)将离线计算得到的偏移角与电压峰值、频率的关系拟合成数学函数,达到简化实时运算的目的;设计了VSG型UPFC的额外储能环节容量参数。最后将提出的参数优化设计以及电压偏移角控制策略与3种典型的电压偏移角算法比较,证明了提出的方法可以进一步优化UPFC设计参数并降低视在功率。展开更多
基金supported by by National Natural Science Founda-tion of China (No. 60702055)Program for New Century ExcellentTalents in University (NCET-07-0914)the Science and Technology Research Project of Chongqing Municipal Education Commission of China (KJ070521)
文摘The topology control strategies of wireless sensor networks are very important for reducing the energy consumption of sensor nodes and prolonging the life-span of networks. In this paper, we put forward a minimum-energy path-preserving topology control （MPTC） algorithm based on a concept of none k-redundant edges. MPTC not only resolves the problem of excessive energy consumption because of the unclosed region in small minimum-energy communication network （SMECN）, but also preserves at least one minimum-energy path between every pair of nodes in a wireless sensor network. We also propose an energy-efficient reconfiguration protocol that maintains the minimum-energy path property in the case where the network topology changes dynamically. Finally, we demonstrate the performance improvements of our algorithm through simulation.
文摘The full bridge zero voltage zero current switching （ FB-ZVZCS ） , which could adjust the output power by keeping the duty ratio of lagging leg constant and changing the duty ratio of leading leg, was a common circuit of soft switching arc welding inverter power source. However, when the duty ratio of leading leg was reduced to zero, the output power stayed the constant value instead of becoming zero. The working status and waveforms of some major parameters were studied in this paper while the duty ratio of leading leg was zero. It was concluded that the minimum output power of soft switching inverter was related to the charging voltage of paraUel capacitors, and the output power also could be reduced by reducing the duty ratio of lagging leg. A novel two-stage continuous PWM control method that could switch working-mode between full bridge and half bridge was put forward in this paper. This kind of control method could further reduce the output power of soft switching inverter in order to meet the requirement of low heat input of sheet metal welding.
文摘具备虚拟同步发电机(virtual synchronous generator,VSG)调节能力的统一潮流控制器(unified power flow controller,UPFC)可以为电网提供额外的惯性和阻尼,提高UPFC在新能源输发电领域的竞争力。然而不匹配的换流器输出电压偏移角会增加设备制造成本和额外功率损耗。阐述了VSG型的统一潮流控制器系统,在讨论电压偏移角的大小对UPFC视在功率以及设计参数的影响后,分析了3种典型的电压偏移角控制方案的参数设计。提出了最小容量的参数设计方案以及在上述参数指标限制下以最小功率为目标的偏移角控制策略,并利用数学统计软件(statistical product and service solutions,SPSS)将离线计算得到的偏移角与电压峰值、频率的关系拟合成数学函数,达到简化实时运算的目的;设计了VSG型UPFC的额外储能环节容量参数。最后将提出的参数优化设计以及电压偏移角控制策略与3种典型的电压偏移角算法比较,证明了提出的方法可以进一步优化UPFC设计参数并降低视在功率。
