交流电网故障引发线路换相换流器高压直流(Line Commutated Converter High Voltage Direct Current,LCC-HVDC)换相失败,改变了原有交流电网工频变化量方向保护动作特性。针对这一问题,建立了由电压源换流器高压直流(Voltage Source Con...交流电网故障引发线路换相换流器高压直流(Line Commutated Converter High Voltage Direct Current,LCC-HVDC)换相失败,改变了原有交流电网工频变化量方向保护动作特性。针对这一问题,建立了由电压源换流器高压直流(Voltage Source Converter HVDC,VSC-HVDC)系统与LCC-HVDC系统组成的混合多馈入直流(bybrid multi-infeed HVDC,HMIDC)输电系统模型,并与馈入同一交流电网的单条LCC-HVDC的交直流系统进行对比分析。结合分析工频变化量方向保护原理的特点,定量分析了在两种不同输电结构,同一换相失败情况下的等值工频变化量阻抗特性。基于PSCAD/EMTDC对两种不同结构的直流输电系统,以同一故障引发换相失败进行仿真分析,验证了理论分析的准确性和有效性。表明该HMIDC系统能改善LCC-HVDC换相失败对工频变化量方向保护的影响;理论分析方法为电网直流规划提供了评估依据。展开更多
Zhengzhou is a developing city in China, that is heavily polluted by high levels of particulate matter. In this study, fine particulate matter （PM2.5） was collected and analyzed for their chemical composition （solu...Zhengzhou is a developing city in China, that is heavily polluted by high levels of particulate matter. In this study, fine particulate matter （PM2.5） was collected and analyzed for their chemical composition （soluble ions, elements, elemental carbon （EC） and organic carbon （OC）） in an industrial district of Zhengzhou in 2010. The average concentrations of PM2.5 were 181, 122, 186 and 211 μg/m3 for spring, summer, autumn and winter, respectively, with an annual average of 175 μg/m3, far exceeding the PM2.5 regulation of USA National Air Quality Standards （15 μg/m3）. The dominant components of PM2.5 in Zhengzhou were secondary ions （sulphate and nitrate） and carbon fractions. Soluble ions, total carbon and elements contributed 41%, 13% and 3% of PM2.5 mass, respectively. Soil dust, secondary aerosol and coal combustion, each contributing about 26%, 24% and 23% of total PM2.5 mass, were the major sources of PM2.5, according to the result of positive matrix factorization analysis. A mixed source of biomass burning, oil combustion and incineration contributed 13% of PM2.5. Fine particulate matter arising from vehicles and industry contributed about 10% and 4% of PM2.5, respectively.展开更多
文摘交流电网故障引发线路换相换流器高压直流(Line Commutated Converter High Voltage Direct Current,LCC-HVDC)换相失败,改变了原有交流电网工频变化量方向保护动作特性。针对这一问题,建立了由电压源换流器高压直流(Voltage Source Converter HVDC,VSC-HVDC)系统与LCC-HVDC系统组成的混合多馈入直流(bybrid multi-infeed HVDC,HMIDC)输电系统模型,并与馈入同一交流电网的单条LCC-HVDC的交直流系统进行对比分析。结合分析工频变化量方向保护原理的特点,定量分析了在两种不同输电结构,同一换相失败情况下的等值工频变化量阻抗特性。基于PSCAD/EMTDC对两种不同结构的直流输电系统,以同一故障引发换相失败进行仿真分析,验证了理论分析的准确性和有效性。表明该HMIDC系统能改善LCC-HVDC换相失败对工频变化量方向保护的影响;理论分析方法为电网直流规划提供了评估依据。
基金part of the Science and Technology Plan Project in Zhengzhou funded by Henan Administration of Foreign Experts Affairs and Science and Technology Bureau of Zhengzhou City (grant no.094SYJH36069)support from Peking University and Taiwan Yunlin University of Science and Technology
文摘Zhengzhou is a developing city in China, that is heavily polluted by high levels of particulate matter. In this study, fine particulate matter （PM2.5） was collected and analyzed for their chemical composition （soluble ions, elements, elemental carbon （EC） and organic carbon （OC）） in an industrial district of Zhengzhou in 2010. The average concentrations of PM2.5 were 181, 122, 186 and 211 μg/m3 for spring, summer, autumn and winter, respectively, with an annual average of 175 μg/m3, far exceeding the PM2.5 regulation of USA National Air Quality Standards （15 μg/m3）. The dominant components of PM2.5 in Zhengzhou were secondary ions （sulphate and nitrate） and carbon fractions. Soluble ions, total carbon and elements contributed 41%, 13% and 3% of PM2.5 mass, respectively. Soil dust, secondary aerosol and coal combustion, each contributing about 26%, 24% and 23% of total PM2.5 mass, were the major sources of PM2.5, according to the result of positive matrix factorization analysis. A mixed source of biomass burning, oil combustion and incineration contributed 13% of PM2.5. Fine particulate matter arising from vehicles and industry contributed about 10% and 4% of PM2.5, respectively.
