The herringbone water-sediment separation structure(HWSSS) was developed to prevent debris flows. This paper mainly focuses on evaluating the sediment separation efficiency of HWSSS in debris flow prevention and deter...The herringbone water-sediment separation structure(HWSSS) was developed to prevent debris flows. This paper mainly focuses on evaluating the sediment separation efficiency of HWSSS in debris flow prevention and determining the grid opening width D, a crucial structure parameter for HWSSS design. Theoretical analysis on the total sediment separation rate Pt reveals that the efficiency of sediment separation is much related with sediment grain size distribution(GSD) and grid opening width. The lower limit of Pt is deduced from the perspective of safety consideration by transforming debris flow into sediment-laden flow. Hydraulic model tests were carried out. Based on the regression analysis of the experimental data, the quantitative relationships between Pt and D and GSD characteristic values were finally established. A procedure for determining optimal grid opening width is proposed based on these analyses. These results are of significance in evaluating sediment separation effect by HWSSS in debris flow prevention and contribute to a more explicit methodology for design of HWSSS.展开更多
In wind power generation system the grid-connected inverter is an important section for energy conversion and transmission, of which the performance has a direct influence on the entire wind power generation system. T...In wind power generation system the grid-connected inverter is an important section for energy conversion and transmission, of which the performance has a direct influence on the entire wind power generation system. The mathematical model of the grid-connected inverter is deduced firstly. Then, the space vector pulse width modulation （SVPWM） is analyzed. The power factor can be controlled close to unity, leading or lagging, which is realized based on H-type current controller and grid voltage vector-oriented control. The control strategy is verified by the simulation and experimental results with a good sinusoidal current, a small harmonic component and a fast dynamic response.展开更多
Necessity of electricity access in remote area is the main reason for expanding decentralized energy system such as stand-alone power systems. The best electrical power supply must provide a constant magnitude and fre...Necessity of electricity access in remote area is the main reason for expanding decentralized energy system such as stand-alone power systems. The best electrical power supply must provide a constant magnitude and frequency voltage. Therefore, good power quality is an important factor for the reliable operation of electrical loads in a power system. However, the current drawn by most of electronic devices and non-linear loads are non-sinusoidal, which can result in a poor power quality, especially in off-grid power systems. Poor power quality is characterized by electrical disturbances such as transients, sags, swells, harmonics and even interruptions in the power supply. Off-grid power systems worldwide often struggle with system failures and equipment damage due to poor power quality. In this paper, MAT- LAB/Simulink is used to model and analyses power quality in an off-grid renewable energy system. The results show high voltage transient when the inductive loads were switched OFF. The voltage and current harmonics are also determined and compared for various types of loads.展开更多
基金supported by the National Science and Technology Support Program (2011BAK12B00)
文摘The herringbone water-sediment separation structure(HWSSS) was developed to prevent debris flows. This paper mainly focuses on evaluating the sediment separation efficiency of HWSSS in debris flow prevention and determining the grid opening width D, a crucial structure parameter for HWSSS design. Theoretical analysis on the total sediment separation rate Pt reveals that the efficiency of sediment separation is much related with sediment grain size distribution(GSD) and grid opening width. The lower limit of Pt is deduced from the perspective of safety consideration by transforming debris flow into sediment-laden flow. Hydraulic model tests were carried out. Based on the regression analysis of the experimental data, the quantitative relationships between Pt and D and GSD characteristic values were finally established. A procedure for determining optimal grid opening width is proposed based on these analyses. These results are of significance in evaluating sediment separation effect by HWSSS in debris flow prevention and contribute to a more explicit methodology for design of HWSSS.
基金supported by Delta Power Electronic Science and Education Development in 2007 (Grant No.DRES2007002)
文摘In wind power generation system the grid-connected inverter is an important section for energy conversion and transmission, of which the performance has a direct influence on the entire wind power generation system. The mathematical model of the grid-connected inverter is deduced firstly. Then, the space vector pulse width modulation （SVPWM） is analyzed. The power factor can be controlled close to unity, leading or lagging, which is realized based on H-type current controller and grid voltage vector-oriented control. The control strategy is verified by the simulation and experimental results with a good sinusoidal current, a small harmonic component and a fast dynamic response.
文摘Necessity of electricity access in remote area is the main reason for expanding decentralized energy system such as stand-alone power systems. The best electrical power supply must provide a constant magnitude and frequency voltage. Therefore, good power quality is an important factor for the reliable operation of electrical loads in a power system. However, the current drawn by most of electronic devices and non-linear loads are non-sinusoidal, which can result in a poor power quality, especially in off-grid power systems. Poor power quality is characterized by electrical disturbances such as transients, sags, swells, harmonics and even interruptions in the power supply. Off-grid power systems worldwide often struggle with system failures and equipment damage due to poor power quality. In this paper, MAT- LAB/Simulink is used to model and analyses power quality in an off-grid renewable energy system. The results show high voltage transient when the inductive loads were switched OFF. The voltage and current harmonics are also determined and compared for various types of loads.
