传统单相三电平整流器的开关器件较多;两电平整流器开关器件相对少,但其交流侧输入滤波电感体积大,开关频率相对较高导致功率器件损耗增大,工作效率有所降低。针对上述问题,文中提出级联、电平等效、镜像、去冗余等三电平电路拓扑方案,...传统单相三电平整流器的开关器件较多;两电平整流器开关器件相对少,但其交流侧输入滤波电感体积大,开关频率相对较高导致功率器件损耗增大,工作效率有所降低。针对上述问题,文中提出级联、电平等效、镜像、去冗余等三电平电路拓扑方案,并以两电平伪图腾柱式功率因数校正电路(pseudo totem-pole power factor correction,PTP-PFC)为例进行上述拓扑方案的推导过程分析,提出一类三电平PTP-PFC电路。首先,对所提新型单相三电平PTP-PFC变换器进行工作原理分析,并提出一种适合此类拓扑的调制方法;其次,对所提拓扑进行功率器件数量、电压应力、损耗等方面分析和对比,总结出各电路特性;最后,设计输出电压400V、功率1kW的3种三电平PTP-PFC实验样机,实验结果证明级联、电平等效、镜像、去冗余等三电平电路拓扑方案的有效性,同时验证所提三电平PTP-PFC电路理论分析的正确性和工程应用的可行性。展开更多
The fractal dimensions in different topological spaces of polyferric chloride-humic acid （PFC-HA） flocs, formed in flocculating different kinds of humic acids （HA） water at different initial pH （9.0, 7.0, 5.0） a...The fractal dimensions in different topological spaces of polyferric chloride-humic acid （PFC-HA） flocs, formed in flocculating different kinds of humic acids （HA） water at different initial pH （9.0, 7.0, 5.0） and PFC dosages, were calculated by effective densitymaximum diameter, image analysis, and N2 absorption-desorption methods, respectively. The mass fractal dimensions （De） of PFC-HA floes were calculated by bi-logarithm relation of effective density with maximum diameter and Logan empirical equation. The Df value was more than 2.0 at initial pH of 7,0, which was 11% and 13% higher than those at pH 9.0 and 5.0, respecively, indicating the most compact flocs formed in flocculated HA water at initial pH of 7.0. The image analysis for those flocs indicates that after flocculating the HA water at initial pH greater than 7.0 with PFC flocculant, the fractal dimensions of D2 （logA vs. logdL） and D3 （logVsphere vs. logdL） of PFC-HA floes decreased with the increase of PFC dosages, and PFC-HA floes showed a gradually looser structure. At the optimum dosage of PFC, the D2 （logA vs. logdL） values of the flocs show 14%-43% difference with their corresponding Dr, and they even had different tendency with the change of initial pH values. However, the D2 values of the floes formed at three different initial pH in HA solution had a same tendency with the corresponding Df. Based on fractal Frenkel-Halsey-HiU （FHH） adsorption and desorption equations, the pore surface fractal dimensions （Ds） for dried powders of PFC-HA flocs formed in HA water with initial pH 9.0 and 7.0 were all close to 2.9421, and the Ds values of flocs formed at initial pH 5.0 were less than 2.3746. It indicated that the pore surface fractal dimensions of PFC-HA floes dried powder mainly show the irregularity from the mesopore-size distribution and marcopore-size distribution.展开更多
针对现有第4类LLC谐振型DC-DC变流器拓扑种类繁多,研究芜杂的现状,该文在总结第4类LLC谐振型变流器基本特性及分析方法的基础上,从模块电路功能辨识的角度出发,将该类变流器拓扑重新统一构建在一个由若干基本功能电路模块组成的宏模型内...针对现有第4类LLC谐振型DC-DC变流器拓扑种类繁多,研究芜杂的现状,该文在总结第4类LLC谐振型变流器基本特性及分析方法的基础上,从模块电路功能辨识的角度出发,将该类变流器拓扑重新统一构建在一个由若干基本功能电路模块组成的宏模型内,并探求归纳其所有基于此宏模型的功能电路模块准同构拓扑形式。这些拓扑形式保留了第4类LLC谐振型DC-DC变流器的特征和优点,可根据输入输出及磁隔离要求而分类,并具有各自适用的应用场合,是电力电子系统集成优选拓扑类。进而,这些拓扑可柔性改造成诸多变形形式,从而适用于一些特殊应用,例如高压输入及高效率多路输出场合。最后,用一个适用于不间断电源(uninterruptible power supply,UPS)系统后备模式直直转换的样机验证第4类LLC谐振型DC-DC变流器准同构拓扑及变形形式的多样性和在工业应用中的有效性。展开更多
文摘传统单相三电平整流器的开关器件较多;两电平整流器开关器件相对少,但其交流侧输入滤波电感体积大,开关频率相对较高导致功率器件损耗增大,工作效率有所降低。针对上述问题,文中提出级联、电平等效、镜像、去冗余等三电平电路拓扑方案,并以两电平伪图腾柱式功率因数校正电路(pseudo totem-pole power factor correction,PTP-PFC)为例进行上述拓扑方案的推导过程分析,提出一类三电平PTP-PFC电路。首先,对所提新型单相三电平PTP-PFC变换器进行工作原理分析,并提出一种适合此类拓扑的调制方法;其次,对所提拓扑进行功率器件数量、电压应力、损耗等方面分析和对比,总结出各电路特性;最后,设计输出电压400V、功率1kW的3种三电平PTP-PFC实验样机,实验结果证明级联、电平等效、镜像、去冗余等三电平电路拓扑方案的有效性,同时验证所提三电平PTP-PFC电路理论分析的正确性和工程应用的可行性。
基金supported by the National Natural Science Foundation of China (No. 20407004, 50578012, 50178009)the High-Tech Research and Development Program (863) of China (No. 2007AA06Z301)+2 种基金the Fok Ying Tung Education Foundation of National Education Ministry of China (No. 91078)the Beijing Municipal Commission of Education Project, Program for New Cen- tury Excellent Talents in University (No. NCET-06-0120)the Beijing Nova of Science and Technology, Beijing Key Subject (No. XK100220555).
文摘The fractal dimensions in different topological spaces of polyferric chloride-humic acid （PFC-HA） flocs, formed in flocculating different kinds of humic acids （HA） water at different initial pH （9.0, 7.0, 5.0） and PFC dosages, were calculated by effective densitymaximum diameter, image analysis, and N2 absorption-desorption methods, respectively. The mass fractal dimensions （De） of PFC-HA floes were calculated by bi-logarithm relation of effective density with maximum diameter and Logan empirical equation. The Df value was more than 2.0 at initial pH of 7,0, which was 11% and 13% higher than those at pH 9.0 and 5.0, respecively, indicating the most compact flocs formed in flocculated HA water at initial pH of 7.0. The image analysis for those flocs indicates that after flocculating the HA water at initial pH greater than 7.0 with PFC flocculant, the fractal dimensions of D2 （logA vs. logdL） and D3 （logVsphere vs. logdL） of PFC-HA floes decreased with the increase of PFC dosages, and PFC-HA floes showed a gradually looser structure. At the optimum dosage of PFC, the D2 （logA vs. logdL） values of the flocs show 14%-43% difference with their corresponding Dr, and they even had different tendency with the change of initial pH values. However, the D2 values of the floes formed at three different initial pH in HA solution had a same tendency with the corresponding Df. Based on fractal Frenkel-Halsey-HiU （FHH） adsorption and desorption equations, the pore surface fractal dimensions （Ds） for dried powders of PFC-HA flocs formed in HA water with initial pH 9.0 and 7.0 were all close to 2.9421, and the Ds values of flocs formed at initial pH 5.0 were less than 2.3746. It indicated that the pore surface fractal dimensions of PFC-HA floes dried powder mainly show the irregularity from the mesopore-size distribution and marcopore-size distribution.
文摘针对现有第4类LLC谐振型DC-DC变流器拓扑种类繁多,研究芜杂的现状,该文在总结第4类LLC谐振型变流器基本特性及分析方法的基础上,从模块电路功能辨识的角度出发,将该类变流器拓扑重新统一构建在一个由若干基本功能电路模块组成的宏模型内,并探求归纳其所有基于此宏模型的功能电路模块准同构拓扑形式。这些拓扑形式保留了第4类LLC谐振型DC-DC变流器的特征和优点,可根据输入输出及磁隔离要求而分类,并具有各自适用的应用场合,是电力电子系统集成优选拓扑类。进而,这些拓扑可柔性改造成诸多变形形式,从而适用于一些特殊应用,例如高压输入及高效率多路输出场合。最后,用一个适用于不间断电源(uninterruptible power supply,UPS)系统后备模式直直转换的样机验证第4类LLC谐振型DC-DC变流器准同构拓扑及变形形式的多样性和在工业应用中的有效性。
