A novel three-phase traction power supply system is proposed to eliminate the adverse effects caused by electric phase separation in catenary and accomplish a unifying manner of traction power supply for rail transit....A novel three-phase traction power supply system is proposed to eliminate the adverse effects caused by electric phase separation in catenary and accomplish a unifying manner of traction power supply for rail transit.With the application of two-stage three-phase continuous power supply structure,the electrical characteristics exhibit new features differing from the existing traction system.In this work,the principle for voltage levels determining two-stage network is dissected in accordance with the requirements of traction network and electric locomotive.The equivalent model of three-phase traction system is built for deducing the formula of current distribution and voltage losses.Based on the chain network model of the traction network,a simulation model is established to analyze the electrical characteristics such as traction current distribution,voltage losses,system equivalent impedance,voltage distribution,voltage unbalance and regenerative energy utilization.In a few words,quite a lot traction current of about 99%is undertaken by long-section cable network.The proportion of system voltage losses is small attributed to the two-stage three-phase power supply structure,and the voltage unbal-ance caused by impedance asymmetry of traction network is less than 1‰.In addition,the utilization rate of regenerative energy for locomotive achieves a significant promotion of over 97%.展开更多
Through analysis of the current situation and newly-increased production capacity-of the oil refining industry of China, this Paper discusses both the continuous expansion trend and the serious excess of production ca...Through analysis of the current situation and newly-increased production capacity-of the oil refining industry of China, this Paper discusses both the continuous expansion trend and the serious excess of production capacity of the oil refining industry of China. Due to the entry of the Chinese economy into the new normal,the accelerated substitution of old energy by new energy and rigid restrictions composed of low carbon and environmental protection requirements, the oil demand of China will continue to increase overall, but the growth will obviously slow down. At the same time, the newly-increased production capacity in Shandong and coastal region will continuously expand, the supply and demand contradiction will intensify, and the structural excess production capacity of the oil refining industry of China will be prominent. It is suggested that the government should attach great importance to the production capacity of the oil refining industry at the macro level, and deeply carry forward the supply side structural reform, and that enterprises should speed up technical innovation,enhance regional and layout optimization, adapt to market changes and adjust product structure, control oil refining but increase chemical engineering, improve product quality and production efficiency, and constantly promote the international competitiveness of the Chinese petrochemical industry.展开更多
基金This research was supported by the Science and Technology Plan Project of Sichuan Province(No.21YYJC3324)the Science and Technology Plan Project of Sichuan Province(No.2022YFQ0104).
文摘A novel three-phase traction power supply system is proposed to eliminate the adverse effects caused by electric phase separation in catenary and accomplish a unifying manner of traction power supply for rail transit.With the application of two-stage three-phase continuous power supply structure,the electrical characteristics exhibit new features differing from the existing traction system.In this work,the principle for voltage levels determining two-stage network is dissected in accordance with the requirements of traction network and electric locomotive.The equivalent model of three-phase traction system is built for deducing the formula of current distribution and voltage losses.Based on the chain network model of the traction network,a simulation model is established to analyze the electrical characteristics such as traction current distribution,voltage losses,system equivalent impedance,voltage distribution,voltage unbalance and regenerative energy utilization.In a few words,quite a lot traction current of about 99%is undertaken by long-section cable network.The proportion of system voltage losses is small attributed to the two-stage three-phase power supply structure,and the voltage unbal-ance caused by impedance asymmetry of traction network is less than 1‰.In addition,the utilization rate of regenerative energy for locomotive achieves a significant promotion of over 97%.
文摘Through analysis of the current situation and newly-increased production capacity-of the oil refining industry of China, this Paper discusses both the continuous expansion trend and the serious excess of production capacity of the oil refining industry of China. Due to the entry of the Chinese economy into the new normal,the accelerated substitution of old energy by new energy and rigid restrictions composed of low carbon and environmental protection requirements, the oil demand of China will continue to increase overall, but the growth will obviously slow down. At the same time, the newly-increased production capacity in Shandong and coastal region will continuously expand, the supply and demand contradiction will intensify, and the structural excess production capacity of the oil refining industry of China will be prominent. It is suggested that the government should attach great importance to the production capacity of the oil refining industry at the macro level, and deeply carry forward the supply side structural reform, and that enterprises should speed up technical innovation,enhance regional and layout optimization, adapt to market changes and adjust product structure, control oil refining but increase chemical engineering, improve product quality and production efficiency, and constantly promote the international competitiveness of the Chinese petrochemical industry.
