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Avoiding sustained oscillations in power systems with tap changing transformers
06 Electrical power supply and utilization (scientific, technical) quad-flatpack programmable MCM (1.42 x 1.42 x 0.16 in). The charging and discharging characteristics of this battery are presented and discussed in terms of its intended application.
99/99291 A nonlinear controller desian for SVC to imorove power system voltage stability ” Wang, Y. et al. Elec. Power and Energy Sysr., 2000, 22, (7). 463-470. This-paper discusses a non-linear controller design for. static var comoensator (SVC) to imorove Dower svstem voltage stabilitv. A thirdorder non-linear ‘dynamical description for thi SVC ‘system is developed. Direct feedback linearization (DFL) technique is employed to design a non-linear controller. The effectiveness of the controller on voltage stability enhancement is studied on a three-bus power system through time simulation and bifurcation analysis. The results show that the collapse time is put off and the subcritical Hopf bifurcation is greatly affected by the controller. The performance of the controller is further compared with that of the conventional capacitor switching. It is found that in some cases the conventional control scheme cannot prevent voltage collapse while the non-linear SVC control can stabilize the system. The results show that the proposed controller is effective in voltage stability enhancement. 99100292 An efficient approach for voltage security analysis and enhancement Bijwe, P. R. t-f al. Elec. Power and Energy Syst., 2000, 22, (7), 483486. This paper presents an efficient one step look-ahead approach for postcontingency loadability limit analysis and its enhancement in critical cases. This is achieved by using steady state analysis tool judiciously within its limitations. The proposed approach does not require any computation of post-contingency distance or margin to the loadability limit for screening non-critical contingencies. In the new approach, the possibility of occurrence of critical loading earlier than the predicted load at next step corresponding to monitoring and control rescheduling stage is examined after each contingency at base case. Only a load flow convergence check is required for this purpose. In critical cases where loadability limit is insufficient, strategies for post-contingency rescheduline of controls at base-case loadine are devised such that the deviazon from the base-case control sihedule is minimum and the loadability limit is pushed beyond the next predicted load step. Results for a sample test system have been obtained to demonstrate the suitability of the proposed algorithm.
An electrochemical investigation of mechanical alloying of MgNi-based hydrogen storage alloys
99100293
Jiang, J-J. and Gasik, M. J. Power Sources, 2000, 89, (l), 117-124. The electrochemical properties of amorphous MgNi-based hydrogen storage alloys synthesized by mechanical alloying (MA) were evaluated. The results show that these amorphous MgsaNiSc alloys exhibit a higher discharge capacity and relatively good rate capacity at a suitable grinding time while their cycle life is very poor. In order to improve the cycle life, the surface of the amorphous Mgr&Iiss alloy was coated with Ti, Al and Zr in Spex 8000 mill/mixer and the coating effects were further investigated. Based on experimental results, two kinds of MgNibased amorphous alloys are designed by substituting part of Mg in MgNi-based alloys by suitable elements. These alloys are then composed of four components. Thus, the cycle life of electrodes consisting of these quaternary amorphous alloys is greatly improved.
An investigation of the Lil+6Mn2_804 cathode material for rechargeable lithium ion batteries Part I: comoosition and structure analvses .~-~ W/99294
He, L. Sol. Energy Mat. & Sol. Cells: 2000, 62, (l-2), 117-123. The Hunter’s chemical delithiating process has been applied for the first time to produce Li+-extracted-materials from 6 spine1 lithium manganese oxides. The composition and structure of these Li+extracted materials have been analysed by X-ray diffraction (XRD), infra-red spectroscopy (IR) and atomic absorption spectroscopy techniques. The results show that these Li+-extracted materials keep cubic symmetry structure and the host framework Mnz-604 of the starting material, Lii+6Mnz_a04 (6 = 0.044). However, contraction of the framework occurs during the delithiating process and thus the lattice parameter, a, changes regionally with the lithium content in Li+-extracted materials. Furthermore, the present work demonstrates that the amount of lithium ions in octahedral sites remain intact.
An investigation of the Lir+aMn2_80., cathode material for rechargeable lithium ion batteries Part II: characterization and delithiating mechanism
00100295
He, L. er al. Sol. Energy Mat. & Sol. Cells, 2000, 62, (l-2), 125-132. The Hunter’s chemical delithiating process has been applied for the first time to produce Li+-extracted materials from &spine1 lithium manganese oxides. The characterization of the obtained materials has been investigated by the laser diffraction (LD) technique and the Brunauer-Emmett-Teller (BET) method, Jager-Vetter titration, as well as the scanning electron microscope technique (SEM). The 30
Fuel and Energy Abstracts
January 2991
charge/discharge curves of the starting material Lii+6Mnz-a04, 6 = 0.044 and its Li+-extracted materials Li. + sMnz_a04 are also tested. Upon the above testing results and analyses, the present work firstly proposes the mechanism of the chemical delithiating process for the stoichiometric spine1 compounds Li1+,Mnz_604 (0 5 6 5 0.33).
Application of the CaMnOrbased high electronic conductivitv ceramic to cathode active material in alkaline battery _ 00100296
Esaka, T. ef al. Adv. Sci. Technol. (Faenra, Italy), 1999, 24, 157-164. In order to check the application of high conductivity oxide ceramics to cathode active materials in batteries, the cathodic behaviours were investigated as to the several types of substituted oxide ceramics based on CaMnOs-6 in alkaline solutions. As a result, it was discovered that some oxides, the Ca-sites of which were substituted by a rare earth element, show high electronic conductivity of more than 10’ S cm-t at room temperature even in the sintered porous state and the ceramics work as the cathode active materials without any conductive additives. The kind of rare earth element, the way of the substitution and the alkaline solution are the factors that determine the discharge performance. The highest discharge capacity is 225 mAh g-’ (810 C gg’) for the x = 0.1 sample of Cai.,Laws Mn0s.6 in 5% LiOH solution. A discussion is also included on the cathodic property in relation with the lithium battery that contains a non-aqueous solution. 00100297 Application of wavelet transform in travelling wave protection Liang, J. et al. Elec. Power and Energy Syst., 2000, 22, (8), 537-542. In this paper, the correlation function-based travelling wave protection algorithm is analysed from the viewpoint of wavelet transform (WT) and a wavelet correlation function (WCF) algorithm is proposed to reolace it. In the new aleorithm. the multi-scale saline WT is used to detect the edges of the yravelling wave signal, anh the WCF is then employed to fulfil the correlation operation in the WT domain instead of ihe time domain. This enhances the peak intensity and the noise rejection ability of the algorithm. The performance of this algorithm is illustrated by simulation results.
Avoiding sustained oscillations in power systems with tap changing transformers 00100296
Wu, Q. et al. Elec. Power and Energy Sysf., 2000, 22, (8), 597-605. The problem of avoiding sustained oscillations in power systems with dynamic loads and tap changing transformers is analysed. Deadband size adjustment is used to eliminate limit cycles which originate from tap-load interactions. The analysis demonstrates the role of load dynamics in providing a deadband setting which guarantees the absence of sustained oscillatory behavior.
Characterisation of mesocarb.on microbeads (cBK~B) as acbve electrode material in hthium and sodium 00100299
Alchntara, R. et al. Carbon, 2000, 38, (7), 1031-1041. Mesocarbon microbeads (MCMB) derived from petroleum residues and heat treated under. different experimental conditions were characterised by X-ray and electron diffraction, proton magnetic resonance (PMRl. Fourier transform infrared soectroscoov , 1 _J, (FTIR) \ I and electron paramagnetic resonance (EPR). The presence of two different forms of hydrogen is retained after heating to 750°C under vacuum. Graphitizationto 3000°C leads to graphite ribbon-like particles surrounding microbeads of a few microns in size. The crystalline graphite, monodomains are with a small band gap or are semimetallic as observed by EPR. Heat treatment even at 3000°C does not eliminate completely the localized paramagnetic defects in the microbeads. These properties condition the aptitude of these materials toward their use in lithium and sodium electrochemical cells. The samples prepared at 750°C have a reversible intercalation behaviour, while samples prepared at 3000°C evidence solvent decomposition resulting in a non-reversible extended discharge plateau when using sodium perchlorate electrolyte dissolved in pure propylene carbonate (PC). ,I
Characterization of a diffusion barrier layer for molybdenum electrodes
00/00300
Buell, D. A. et al. Surf. Modif. Technol. XII, Proc. Int. ConI., 12th. 1998, 85-90. Edited by Sudarshan T.S., Khor K.A., Jeandin M. Molybdenum is used as an electrode in glass melting furnaces for electric resistance heating. A diffusion barrier coating layer is being designed and developed to enhance the high-temperature oxidation resistance of molybdenum. Based on an extensive review of the possible coating systems and earlier investigations, it has been noted that MoSiz with 1.96 mol% Sic is an ideal material for the diffusion barrier. Reactive sputtering of this target in a nitrogen atom produced a quaternary Mo-Si-C-N layer. This layer has been characterized for its structure and chemistry by a combination of techniques such as X-ray diffraction, scanning electron microscopy, differential thermal analysis,
99/99291 A nonlinear controller desian for SVC to imorove power system voltage stability ” Wang, Y. et al. Elec. Power and Energy Sysr., 2000, 22, (7). 463-470. This-paper discusses a non-linear controller design for. static var comoensator (SVC) to imorove Dower svstem voltage stabilitv. A thirdorder non-linear ‘dynamical description for thi SVC ‘system is developed. Direct feedback linearization (DFL) technique is employed to design a non-linear controller. The effectiveness of the controller on voltage stability enhancement is studied on a three-bus power system through time simulation and bifurcation analysis. The results show that the collapse time is put off and the subcritical Hopf bifurcation is greatly affected by the controller. The performance of the controller is further compared with that of the conventional capacitor switching. It is found that in some cases the conventional control scheme cannot prevent voltage collapse while the non-linear SVC control can stabilize the system. The results show that the proposed controller is effective in voltage stability enhancement. 99100292 An efficient approach for voltage security analysis and enhancement Bijwe, P. R. t-f al. Elec. Power and Energy Syst., 2000, 22, (7), 483486. This paper presents an efficient one step look-ahead approach for postcontingency loadability limit analysis and its enhancement in critical cases. This is achieved by using steady state analysis tool judiciously within its limitations. The proposed approach does not require any computation of post-contingency distance or margin to the loadability limit for screening non-critical contingencies. In the new approach, the possibility of occurrence of critical loading earlier than the predicted load at next step corresponding to monitoring and control rescheduling stage is examined after each contingency at base case. Only a load flow convergence check is required for this purpose. In critical cases where loadability limit is insufficient, strategies for post-contingency rescheduline of controls at base-case loadine are devised such that the deviazon from the base-case control sihedule is minimum and the loadability limit is pushed beyond the next predicted load step. Results for a sample test system have been obtained to demonstrate the suitability of the proposed algorithm.
An electrochemical investigation of mechanical alloying of MgNi-based hydrogen storage alloys
99100293
Jiang, J-J. and Gasik, M. J. Power Sources, 2000, 89, (l), 117-124. The electrochemical properties of amorphous MgNi-based hydrogen storage alloys synthesized by mechanical alloying (MA) were evaluated. The results show that these amorphous MgsaNiSc alloys exhibit a higher discharge capacity and relatively good rate capacity at a suitable grinding time while their cycle life is very poor. In order to improve the cycle life, the surface of the amorphous Mgr&Iiss alloy was coated with Ti, Al and Zr in Spex 8000 mill/mixer and the coating effects were further investigated. Based on experimental results, two kinds of MgNibased amorphous alloys are designed by substituting part of Mg in MgNi-based alloys by suitable elements. These alloys are then composed of four components. Thus, the cycle life of electrodes consisting of these quaternary amorphous alloys is greatly improved.
An investigation of the Lil+6Mn2_804 cathode material for rechargeable lithium ion batteries Part I: comoosition and structure analvses .~-~ W/99294
He, L. Sol. Energy Mat. & Sol. Cells: 2000, 62, (l-2), 117-123. The Hunter’s chemical delithiating process has been applied for the first time to produce Li+-extracted-materials from 6 spine1 lithium manganese oxides. The composition and structure of these Li+extracted materials have been analysed by X-ray diffraction (XRD), infra-red spectroscopy (IR) and atomic absorption spectroscopy techniques. The results show that these Li+-extracted materials keep cubic symmetry structure and the host framework Mnz-604 of the starting material, Lii+6Mnz_a04 (6 = 0.044). However, contraction of the framework occurs during the delithiating process and thus the lattice parameter, a, changes regionally with the lithium content in Li+-extracted materials. Furthermore, the present work demonstrates that the amount of lithium ions in octahedral sites remain intact.
An investigation of the Lir+aMn2_80., cathode material for rechargeable lithium ion batteries Part II: characterization and delithiating mechanism
00100295
He, L. er al. Sol. Energy Mat. & Sol. Cells, 2000, 62, (l-2), 125-132. The Hunter’s chemical delithiating process has been applied for the first time to produce Li+-extracted materials from &spine1 lithium manganese oxides. The characterization of the obtained materials has been investigated by the laser diffraction (LD) technique and the Brunauer-Emmett-Teller (BET) method, Jager-Vetter titration, as well as the scanning electron microscope technique (SEM). The 30
Fuel and Energy Abstracts
January 2991
charge/discharge curves of the starting material Lii+6Mnz-a04, 6 = 0.044 and its Li+-extracted materials Li. + sMnz_a04 are also tested. Upon the above testing results and analyses, the present work firstly proposes the mechanism of the chemical delithiating process for the stoichiometric spine1 compounds Li1+,Mnz_604 (0 5 6 5 0.33).
Application of the CaMnOrbased high electronic conductivitv ceramic to cathode active material in alkaline battery _ 00100296
Esaka, T. ef al. Adv. Sci. Technol. (Faenra, Italy), 1999, 24, 157-164. In order to check the application of high conductivity oxide ceramics to cathode active materials in batteries, the cathodic behaviours were investigated as to the several types of substituted oxide ceramics based on CaMnOs-6 in alkaline solutions. As a result, it was discovered that some oxides, the Ca-sites of which were substituted by a rare earth element, show high electronic conductivity of more than 10’ S cm-t at room temperature even in the sintered porous state and the ceramics work as the cathode active materials without any conductive additives. The kind of rare earth element, the way of the substitution and the alkaline solution are the factors that determine the discharge performance. The highest discharge capacity is 225 mAh g-’ (810 C gg’) for the x = 0.1 sample of Cai.,Laws Mn0s.6 in 5% LiOH solution. A discussion is also included on the cathodic property in relation with the lithium battery that contains a non-aqueous solution. 00100297 Application of wavelet transform in travelling wave protection Liang, J. et al. Elec. Power and Energy Syst., 2000, 22, (8), 537-542. In this paper, the correlation function-based travelling wave protection algorithm is analysed from the viewpoint of wavelet transform (WT) and a wavelet correlation function (WCF) algorithm is proposed to reolace it. In the new aleorithm. the multi-scale saline WT is used to detect the edges of the yravelling wave signal, anh the WCF is then employed to fulfil the correlation operation in the WT domain instead of ihe time domain. This enhances the peak intensity and the noise rejection ability of the algorithm. The performance of this algorithm is illustrated by simulation results.
Avoiding sustained oscillations in power systems with tap changing transformers 00100296
Wu, Q. et al. Elec. Power and Energy Sysf., 2000, 22, (8), 597-605. The problem of avoiding sustained oscillations in power systems with dynamic loads and tap changing transformers is analysed. Deadband size adjustment is used to eliminate limit cycles which originate from tap-load interactions. The analysis demonstrates the role of load dynamics in providing a deadband setting which guarantees the absence of sustained oscillatory behavior.
Characterisation of mesocarb.on microbeads (cBK~B) as acbve electrode material in hthium and sodium 00100299
Alchntara, R. et al. Carbon, 2000, 38, (7), 1031-1041. Mesocarbon microbeads (MCMB) derived from petroleum residues and heat treated under. different experimental conditions were characterised by X-ray and electron diffraction, proton magnetic resonance (PMRl. Fourier transform infrared soectroscoov , 1 _J, (FTIR) \ I and electron paramagnetic resonance (EPR). The presence of two different forms of hydrogen is retained after heating to 750°C under vacuum. Graphitizationto 3000°C leads to graphite ribbon-like particles surrounding microbeads of a few microns in size. The crystalline graphite, monodomains are with a small band gap or are semimetallic as observed by EPR. Heat treatment even at 3000°C does not eliminate completely the localized paramagnetic defects in the microbeads. These properties condition the aptitude of these materials toward their use in lithium and sodium electrochemical cells. The samples prepared at 750°C have a reversible intercalation behaviour, while samples prepared at 3000°C evidence solvent decomposition resulting in a non-reversible extended discharge plateau when using sodium perchlorate electrolyte dissolved in pure propylene carbonate (PC). ,I
Characterization of a diffusion barrier layer for molybdenum electrodes
00/00300
Buell, D. A. et al. Surf. Modif. Technol. XII, Proc. Int. ConI., 12th. 1998, 85-90. Edited by Sudarshan T.S., Khor K.A., Jeandin M. Molybdenum is used as an electrode in glass melting furnaces for electric resistance heating. A diffusion barrier coating layer is being designed and developed to enhance the high-temperature oxidation resistance of molybdenum. Based on an extensive review of the possible coating systems and earlier investigations, it has been noted that MoSiz with 1.96 mol% Sic is an ideal material for the diffusion barrier. Reactive sputtering of this target in a nitrogen atom produced a quaternary Mo-Si-C-N layer. This layer has been characterized for its structure and chemistry by a combination of techniques such as X-ray diffraction, scanning electron microscopy, differential thermal analysis,