The voltage uprating of existing overhead lines is an interesting solution for increasing the transmission of electricity, especially in areas where it is difficult to build new lines. If a line is uprated with minor ...The voltage uprating of existing overhead lines is an interesting solution for increasing the transmission of electricity, especially in areas where it is difficult to build new lines. If a line is uprated with minor changes of its design and without improvement of the grounding electrodes of towers, its lightning performance remains unchanged. The consequence is that the uprated line will have a lightning flashover rate very high compared to an overhead line of same nominal voltage but of standard design. One attractive solution to solve this problem is to use line arresters. The goal of this paper is to study the use of line arresters to achieve a satisfactory lightning performance of an overhead line uprated from 225 kV to 400 kV without major design modifications. In order to compare different strategies of line arrester installation the flashover rate is calculated based on a software able to launch automatically EMTP-RV. The software named LIPS has been developed under the cover of a partnership between Hydro-Quebec, RTE and EDF.展开更多
As an emerging research field,inductively coupled wireless power transfer(ICWPT) technology has attracted wide spread attention recently.In this paper,the maximum power transfer performances of four basic topologies l...As an emerging research field,inductively coupled wireless power transfer(ICWPT) technology has attracted wide spread attention recently.In this paper,the maximum power transfer performances of four basic topologies labeled as SS,SP,PS and PP are investigated.By modeling the equivalent circuits of these topologies in high frequency(HF),the primary resonance compensation capacitances for maximum power transfer capability are deduced.It is found that these capacitances fluctuate with load resistance change,which is disadvantageous to SP,PS and PP topologies and an obstacle to their practical applications as well.To solve this problem,a phase controlled inductor circuit is proposed.By adjusting the triggering angle,the real-time dynamic tuning control can be achieved to guarantee maximum power transfer.Finally,simulations and experiments show that the proposed method is of great effectiveness and reliability to solve the issue of resonance compensation capacitance fluctuation with load change and to guarantee the flexible applications of all topologies.展开更多
Sodium ions(Na+) and ether electrolyte coinserted graphite possesses a considerable volume expansion effect. However, the mechanism fails to clearly explain its stability. In response to this deficiency, the co-insert...Sodium ions(Na+) and ether electrolyte coinserted graphite possesses a considerable volume expansion effect. However, the mechanism fails to clearly explain its stability. In response to this deficiency, the co-inserted reaction is proposed, which is affected by the Lorentz force of the applied electric field under the high-current condition. The Na^(+) ions are separated out, while the ethylene glycol dimethyl ether molecules remain between the graphite layers. This insight provides a reasonable explanation for the extraordinary stability of this material. In situ X-ray diffraction and density functional theory calculations confirm the separation and release of Na+. On the basis of this result, unmodified commercial graphite was stably cycled 6400 times at a current density of up to 10 A g^(-1), and the capacity retention rate was as high as 97.2%. The full battery assembled in the laboratory has a maximum output power of 14,846 W kg^(-1)and an output energy density of 103 W h kg^(-1)(relative to the weight of anodic and cathodic active materials). The new mechanism provides innovative ideas for the design of large-scale energy storage devices.展开更多
A cymbal transducer is made up of a piezoceramic disk sandwiched between two dome-shaped metal endcaps.High circumferential stresses caused by flexural motion of the metal endcaps can induce the loss of mechanical inp...A cymbal transducer is made up of a piezoceramic disk sandwiched between two dome-shaped metal endcaps.High circumferential stresses caused by flexural motion of the metal endcaps can induce the loss of mechanical input energy.Finite element analysis shows that the radial slots fabricated in metal endcaps can release the circumferential stresses,and reduce the loss of mechanical input energy that could be converted into electrical energy.In this letter,the performance of a slotted-cymbal transducer in energy harvesting was tested.The results show that the output voltage and power of the cymbal are improved.A maximum output power of around 16 mW could be harvested from a cymbal with 18 cone radial slots across a 500 kΩ resistive load,which is approximately 0.6 times more than that of the original cymbal transducer.展开更多
文摘The voltage uprating of existing overhead lines is an interesting solution for increasing the transmission of electricity, especially in areas where it is difficult to build new lines. If a line is uprated with minor changes of its design and without improvement of the grounding electrodes of towers, its lightning performance remains unchanged. The consequence is that the uprated line will have a lightning flashover rate very high compared to an overhead line of same nominal voltage but of standard design. One attractive solution to solve this problem is to use line arresters. The goal of this paper is to study the use of line arresters to achieve a satisfactory lightning performance of an overhead line uprated from 225 kV to 400 kV without major design modifications. In order to compare different strategies of line arrester installation the flashover rate is calculated based on a software able to launch automatically EMTP-RV. The software named LIPS has been developed under the cover of a partnership between Hydro-Quebec, RTE and EDF.
基金supported by the National High-Tech Research & Development Program of China ("863" Program) (Grant No. 2012AA050210)the National Natural Science Foundation of China (Grant No. 51177011)+1 种基金the Research Innovation Program for College Graduates of Jiangsu Province (Grant No. CXZZ11_0150)Scholarship Award for Excellent Doctoral Student granted by Ministry of Education of China
文摘As an emerging research field,inductively coupled wireless power transfer(ICWPT) technology has attracted wide spread attention recently.In this paper,the maximum power transfer performances of four basic topologies labeled as SS,SP,PS and PP are investigated.By modeling the equivalent circuits of these topologies in high frequency(HF),the primary resonance compensation capacitances for maximum power transfer capability are deduced.It is found that these capacitances fluctuate with load resistance change,which is disadvantageous to SP,PS and PP topologies and an obstacle to their practical applications as well.To solve this problem,a phase controlled inductor circuit is proposed.By adjusting the triggering angle,the real-time dynamic tuning control can be achieved to guarantee maximum power transfer.Finally,simulations and experiments show that the proposed method is of great effectiveness and reliability to solve the issue of resonance compensation capacitance fluctuation with load change and to guarantee the flexible applications of all topologies.
基金supported by the National Natural Science Foundation of China (21978088, 91534202 and 51673063)sponsored by the Program of Shanghai Academic/Technology Research Leader (20XD1433600)+4 种基金the Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutes of High Learningthe Basic Research Program of Shanghai (17JC1402300)the Social Development Program of Shanghai (17DZ1200900)the Shanghai City Board of education research and innovation projectthe Fundamental Research Funds for the Central Universities (222201718002)。
文摘Sodium ions(Na+) and ether electrolyte coinserted graphite possesses a considerable volume expansion effect. However, the mechanism fails to clearly explain its stability. In response to this deficiency, the co-inserted reaction is proposed, which is affected by the Lorentz force of the applied electric field under the high-current condition. The Na^(+) ions are separated out, while the ethylene glycol dimethyl ether molecules remain between the graphite layers. This insight provides a reasonable explanation for the extraordinary stability of this material. In situ X-ray diffraction and density functional theory calculations confirm the separation and release of Na+. On the basis of this result, unmodified commercial graphite was stably cycled 6400 times at a current density of up to 10 A g^(-1), and the capacity retention rate was as high as 97.2%. The full battery assembled in the laboratory has a maximum output power of 14,846 W kg^(-1)and an output energy density of 103 W h kg^(-1)(relative to the weight of anodic and cathodic active materials). The new mechanism provides innovative ideas for the design of large-scale energy storage devices.
基金supported by the National Natural Science Foundation of China (No.50875057)the Natural Scientific Research Innovation Foundation in Harbin Institute of Technology,China (No.HIT.NSRIF.2008.50)
文摘A cymbal transducer is made up of a piezoceramic disk sandwiched between two dome-shaped metal endcaps.High circumferential stresses caused by flexural motion of the metal endcaps can induce the loss of mechanical input energy.Finite element analysis shows that the radial slots fabricated in metal endcaps can release the circumferential stresses,and reduce the loss of mechanical input energy that could be converted into electrical energy.In this letter,the performance of a slotted-cymbal transducer in energy harvesting was tested.The results show that the output voltage and power of the cymbal are improved.A maximum output power of around 16 mW could be harvested from a cymbal with 18 cone radial slots across a 500 kΩ resistive load,which is approximately 0.6 times more than that of the original cymbal transducer.
