The amorphous I/Au composite nanofilms were prepared by low vacuum direct current sputtering(LVDCS) method. The optimized preparation technologies contain growth pressure, time, gaseous environment and annealing condi...The amorphous I/Au composite nanofilms were prepared by low vacuum direct current sputtering(LVDCS) method. The optimized preparation technologies contain growth pressure, time, gaseous environment and annealing conditions. The maximum fluorescence emission(λmax^em) of I/Au nanofilms was observed at wavelength of 375 nm, and the intensity of fluorescence emission peak of annealed I/Au films was smaller than that of unannealed one due to fewer amorphous Au nanoparticles, caused by annealing treatment. In the UV-Vis absorption spectra, the intensity of UV-Vis absorption peak of annealed I/Au nanofilms is larger than that of the unannealed one. This work also developed a new way to grow I/Au composite fluorescent thin films.展开更多
In this paper some photovoltaic, PV, conversion chains architectures for on-grid applications have been proposed and the advantage of the direct use of a Low Voltage Direct Current (LVDC) bus for the DC loads has been...In this paper some photovoltaic, PV, conversion chains architectures for on-grid applications have been proposed and the advantage of the direct use of a Low Voltage Direct Current (LVDC) bus for the DC loads has been shown. The evaluation of the efficiency of the proposed chains compared to the classical one was performed. It is shown that LVDC use instead of standard AC plugs, in numerous applications, is promising in future. The registered annual saved energy can exceed 25% of the PV generated energy. This important rate, the need of better services at lower economic cost and environmental burden will incite to make reflection about industry and supplies’ future standards.展开更多
随着分布式发电装置和电力电子设备在低压配电系统的广泛应用,采用直流供电方式的低压系统又显现出优越性,并引起学者的关注。迄今为止,学者们对低压直流系统的系统结构、负荷的兼容性、负荷模型、电能质量与可靠性、保护和控制、节能...随着分布式发电装置和电力电子设备在低压配电系统的广泛应用,采用直流供电方式的低压系统又显现出优越性,并引起学者的关注。迄今为止,学者们对低压直流系统的系统结构、负荷的兼容性、负荷模型、电能质量与可靠性、保护和控制、节能型评估等方面进行的初步研究表明:低压直流供电系统可以兼容目前大部分的低压负荷,可以对暂态过程进行有效的控制,并提高供电的连续性;特别是在具有分布式发电装置(如太阳能电池、风力发电、燃料电池)的低压系统中,低压直流(low voltage direct current,LVDC)供电系统在降低系统电能损耗、增强供电连续性和可靠性、提高电能质量方面,与交流系统相比,具有优越性,并且系统结构得以简化。同时,该文提出并讨论了低压直流系统需要进一步研究的问题。展开更多
多端口固态变压器(solid state transformer,SST)是多电压等级交直流混合配电网的核心设备。模块化多电平(modular multilevel converter,MMC)型SST可构建中压交流、中压直流和低压直流等端口,其中压直流端口可接入中压直流配电网及构...多端口固态变压器(solid state transformer,SST)是多电压等级交直流混合配电网的核心设备。模块化多电平(modular multilevel converter,MMC)型SST可构建中压交流、中压直流和低压直流等端口,其中压直流端口可接入中压直流配电网及构成多区域交流配电网的柔性互联,从而提升区域网络间功率灵活调节能力。对于低压侧,具有不平衡运行能力的真双极直流母线能够满足低压用户对多电压等级、供电可靠及用电安全等需求,而常规的MMC-SST仅能提供单极或伪双极低压直流端口。因此,文中提出一种真双极型MMC-SST拓扑及基于主动环流注入的桥臂电压平衡优化运行方案,该结构同时具备中压交流、中压直流及低压真双极直流等端口。文中的主要工作包括:简述真双极型MMC-SST连接方式,并基于能量平衡原理,探索低压真双极运行工作机理;建立基于环流的动态模型,揭示双极不平衡功率、桥臂电容电压及环流之间的耦合关系;基于环流注入的稳态模型,获得基于主动环流注入的桥臂电压平衡运行方法,并优化注入环流的幅值和相位;提出基于环流主动注入的桥臂电容电压平衡控制策略。最后,搭建2MVA的MMC-SST仿真模型及4.8kVA的MMC-SST实验样机,验证所提拓扑及控制的可行性和有效性。展开更多
基金Funded by the National Natural Science Foundation of China(No.21676015)
文摘The amorphous I/Au composite nanofilms were prepared by low vacuum direct current sputtering(LVDCS) method. The optimized preparation technologies contain growth pressure, time, gaseous environment and annealing conditions. The maximum fluorescence emission(λmax^em) of I/Au nanofilms was observed at wavelength of 375 nm, and the intensity of fluorescence emission peak of annealed I/Au films was smaller than that of unannealed one due to fewer amorphous Au nanoparticles, caused by annealing treatment. In the UV-Vis absorption spectra, the intensity of UV-Vis absorption peak of annealed I/Au nanofilms is larger than that of the unannealed one. This work also developed a new way to grow I/Au composite fluorescent thin films.
文摘In this paper some photovoltaic, PV, conversion chains architectures for on-grid applications have been proposed and the advantage of the direct use of a Low Voltage Direct Current (LVDC) bus for the DC loads has been shown. The evaluation of the efficiency of the proposed chains compared to the classical one was performed. It is shown that LVDC use instead of standard AC plugs, in numerous applications, is promising in future. The registered annual saved energy can exceed 25% of the PV generated energy. This important rate, the need of better services at lower economic cost and environmental burden will incite to make reflection about industry and supplies’ future standards.
文摘随着分布式发电装置和电力电子设备在低压配电系统的广泛应用,采用直流供电方式的低压系统又显现出优越性,并引起学者的关注。迄今为止,学者们对低压直流系统的系统结构、负荷的兼容性、负荷模型、电能质量与可靠性、保护和控制、节能型评估等方面进行的初步研究表明:低压直流供电系统可以兼容目前大部分的低压负荷,可以对暂态过程进行有效的控制,并提高供电的连续性;特别是在具有分布式发电装置(如太阳能电池、风力发电、燃料电池)的低压系统中,低压直流(low voltage direct current,LVDC)供电系统在降低系统电能损耗、增强供电连续性和可靠性、提高电能质量方面,与交流系统相比,具有优越性,并且系统结构得以简化。同时,该文提出并讨论了低压直流系统需要进一步研究的问题。
文摘多端口固态变压器(solid state transformer,SST)是多电压等级交直流混合配电网的核心设备。模块化多电平(modular multilevel converter,MMC)型SST可构建中压交流、中压直流和低压直流等端口,其中压直流端口可接入中压直流配电网及构成多区域交流配电网的柔性互联,从而提升区域网络间功率灵活调节能力。对于低压侧,具有不平衡运行能力的真双极直流母线能够满足低压用户对多电压等级、供电可靠及用电安全等需求,而常规的MMC-SST仅能提供单极或伪双极低压直流端口。因此,文中提出一种真双极型MMC-SST拓扑及基于主动环流注入的桥臂电压平衡优化运行方案,该结构同时具备中压交流、中压直流及低压真双极直流等端口。文中的主要工作包括:简述真双极型MMC-SST连接方式,并基于能量平衡原理,探索低压真双极运行工作机理;建立基于环流的动态模型,揭示双极不平衡功率、桥臂电容电压及环流之间的耦合关系;基于环流注入的稳态模型,获得基于主动环流注入的桥臂电压平衡运行方法,并优化注入环流的幅值和相位;提出基于环流主动注入的桥臂电容电压平衡控制策略。最后,搭建2MVA的MMC-SST仿真模型及4.8kVA的MMC-SST实验样机,验证所提拓扑及控制的可行性和有效性。
