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RISS 인기검색어
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- 저자 : Chunwei Guo (검색결과 5 건)
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Effects of Cloud Microphysical Latent Heat on a Heavy Rainstorm in Beijing
Chunwei Guo,Hui Xiao,Huiling Yang,Liang Zhai,Xiangchen Kong 한국기상학회 2019 Asia-Pacific Journal of Atmospheric Sciences Vol.55 No.3
The latent heat produced by cloud microphysical processes can greatly affect the thermal and dynamic structure of the atmosphere, as well as the development and evolution of clouds and precipitation. In this study, to examine the consequences of different kinds of latent heat produced by microphysical processes, four sensitivity tests were conducted based on the control simulation results of a heavy rainstorm occurred in Beijing on 21 July 2012 using theWeather Research and Forecasting Model (WRF).Without the latent heat absorption of evaporation, the convective cloud system developed stronger, and the accumulated precipitation amount increased.Without the latent heat release of deposition, the transit time of the surface front was delayed; in addition, the convective cloud system developed weakly. The accumulated conversion amounts of microphysical processes and the accumulated rainfall amount in the deposition adiabatic test were far less than those in the other tests.Without the latent heat of melting and freezing, the convective cloud system did not change substantially, and there was only a minor effect on precipitation. Hydrometeor production exhibited some changes related to precipitation in the five tests. The latent heat produced by the convective system varied substantially in the five tests with a change in the latent heat budget.
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A Novel Zero-Voltage-Switching Push-Pull Forward Converter with a Parallel Resonant Network
Chunwei Cai,Chunyu Shi,Yuxing Guo,Zi Yang,Fangang Meng 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.1
A novel zero-voltage-switching (ZVS) push-pull forward converter with a parallel resonant network is presented in this paper. The novel topology can provide a releasing loop for the energy storage in a leakage inductor for the duration of the power switching by the resonant capacitors paralleled with the primary windings of the transformer. Then the transformer leakage inductor is utilized to be resonant with the parallel capacitor, and the ZVS operation is achieved. This converter exhibits many advantages such as lower duty-cycle losses, limited peak voltage across the rectifier diodes and a higher efficiency. Furthermore, the operating principles and key problems of the converter design are analyzed in detail, and the ZVS conditions are derived. A 500W experimental converter prototype has been built to verify the effectiveness of the proposed converter, and its maximum efficiency reaches 94.8%.
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Chunwei Cai,Pufeng An,Yuxing Guo,Fangang Meng 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.5
A novel three-phase four-wire inverter topology is presented in this paper. This topology is equipped with a special capacitor balance grid without magnetic saturation. In response to unbalanced load and unequal split DC-link capacitors problems, a qusi-full-bridge DC/DC topology is applied in the balance grid. By using a high-frequency transformer, the energy transfer within the two split dc-link capacitors is realized. The novel topology makes the voltage across two split dc-link capacitors balanced so that the neutral point voltage ripple is inhibited. Under the condition of a stable neutral point voltage, the three-phase four-wire inverter can be equivalent to three independent single phase inverters. As a result, the three-phase inverter can produce symmetrical voltage waves with an unbalanced load. To avoid forward transformer magnetic saturation, the voltages of the primary and secondary windings are controlled to reverse once during each switching period. Furthermore, an improved mode chosen operating principle for this novel topology is designed and analyzed in detail. The simulated results verified the feasibility of this topology and an experimental inverter has been built to test the power quality produced by this topology. Finally, simulation results verify that the novel topology can effectively improve the inhibition of an inverter with a three-phase unbalanced load while decreasing the value of the split capacitor.
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Cai, Chunwei,An, Pufeng,Guo, Yuxing,Meng, Fangang The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.5
A novel three-phase four-wire inverter topology is presented in this paper. This topology is equipped with a special capacitor balance grid without magnetic saturation. In response to unbalanced load and unequal split DC-link capacitors problems, a qusi-full-bridge DC/DC topology is applied in the balance grid. By using a high-frequency transformer, the energy transfer within the two split dc-link capacitors is realized. The novel topology makes the voltage across two split dc-link capacitors balanced so that the neutral point voltage ripple is inhibited. Under the condition of a stable neutral point voltage, the three-phase four-wire inverter can be equivalent to three independent single phase inverters. As a result, the three-phase inverter can produce symmetrical voltage waves with an unbalanced load. To avoid forward transformer magnetic saturation, the voltages of the primary and secondary windings are controlled to reverse once during each switching period. Furthermore, an improved mode chosen operating principle for this novel topology is designed and analyzed in detail. The simulated results verified the feasibility of this topology and an experimental inverter has been built to test the power quality produced by this topology. Finally, simulation results verify that the novel topology can effectively improve the inhibition of an inverter with a three-phase unbalanced load while decreasing the value of the split capacitor.
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A Novel Zero-Voltage-Switching Push-Pull Forward Converter with a Parallel Resonant Network
Cai, Chunwei,Shi, Chunyu,Guo, Yuxing,Yang, Zi,Meng, Fangang The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.1
A novel zero-voltage-switching (ZVS) push-pull forward converter with a parallel resonant network is presented in this paper. The novel topology can provide a releasing loop for the energy storage in a leakage inductor for the duration of the power switching by the resonant capacitors paralleled with the primary windings of the transformer. Then the transformer leakage inductor is utilized to be resonant with the parallel capacitor, and the ZVS operation is achieved. This converter exhibits many advantages such as lower duty-cycle losses, limited peak voltage across the rectifier diodes and a higher efficiency. Furthermore, the operating principles and key problems of the converter design are analyzed in detail, and the ZVS conditions are derived. A 500W experimental converter prototype has been built to verify the effectiveness of the proposed converter, and its maximum efficiency reaches 94.8%.
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