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03720 Frequency dependent network equivalents for electromagnetic transient studies
06
Electrical power supply and utilization (scientific, technical)
electric field at the ground level. The charge simulation method (CSM), with complex charges and complex boundary conditions, is used to model the above mentioned systems with a great accuracy.
Electrochemical characteristics of the interface between the metal hydride electrode and electrolyte for an advanced nickel/metal hydride battery
99103716
Han, .I. et al. .I. Power Sources, 1999, 80, (l/2), 39-4.5. In a nickel/metal hydride (MH) battery, the characteristics of the negative electrode are related to the charge transfer and mass transfer processes at the interface between the MH electrode and the electrolyte. With increasing number of charge/discharge cycles, the MH alloy powders micro-crack into particles that are several microns in diameter and this then influences the exchange current density. A polarization experiment was used to analyse the charge transfer and mass transfer processes. The exchange current densities of uncoated and palladium-coated Mm09sTiaOs. NiJ.ssCoo.4sMno.3SAl~~,~s alloy electrodes increase with increasing number of charge/discharge cycles before reaching a constant value after 20-30 cycles.
99193717
An environmental aircraft battery (EAB)
Erbacher, J. K. J. Power Sources, 1999, 80, (l/2), 26.5-271. The Battery Branch of the US Air Force Research Laboratory began the development of an environmental aircraft battery (EAB) to replace existing nickel/cadmium (Ni-Cd) and sealed lead/acid (SLA) batteries to minimize or eliminate use of environmentally hazardous battery materials by the USAF. A three-phase development contract was awarded in 1996 to replace the cadmium in nickel-cadmium batteries with a metal hydride (MH) anode. Designs, materials, space battery technology, and results on commercial and government battery programmes were evaluated in the Phase I, Feasibility Analysis. Bipolar and prismatic designs were selected for Phase II development. Materials and cell test data are presented.
99163716 Environmental assessment of vanadium redox and lead-acid batteries for stationary energy storage Rydh, C. J. J. Power Sources, 1999, 80, (l/2), 21-29. Using a life cycle assessment approach, the environmental impact of both the vanadium redox battery (vanadium battery) and the lead-acid battery for use in stationary applications has been evaluated. In this study, the calculated environmental impact was lower for the vanadium battery than for the lead-acid one. The net energy storage efficiency of the vanadium battery was greater due to lower primary energy needs during the life cycle. Favourable characteristics such as long cycle-life, good availability of resources and recycling ability justify the development and commercialization of the vanadium battery.
Fast nodal assessment of static voltage stability 99103719 including contingency analysis Prada,
R. B. and dos Santos,
J. 0. R.
Electric
Power Systems Research,
1999, 51, (l), 55-59.
A nodal static voltage stability evaluation analytical tool for electric power systems is presented. The method is based on a straightforward physical characterization of the voltage stability phenomena. Emphasis is given to numerical calculation aspects leading to computational efficiency, necessary when leading with real life networks and contingency analysis. The method was able to detect real voltage stability problems in the Brazilian system, which substantiates its applicability and adequacy.
Frequency dependent network equivalents for 99103720 electromagnetic transient studies Ibrahima,
A. I. and Salama, M. M. A.
Electrical Power and Energy Systems,
1999, 21, (6), 395-404.
In electromagnetic transient studies, only a small part of an ac power system can be modelled in detail. The remaining parts of the system should be reduced to an equivalent model. Different methods were developed to generate frequency dependent network equivalents. This paper presents a novel approach for obtaining network equivalents for ac power systems using the QZ algorithm. The proposed method obtains accurate resonant frequencies directly from the system equations to be used in finding the network equivalent parameters. Also, the proposed method is a good tool to predict the system response. The use of the QZ algorithm in the creation of the network equivalent model gives the following advantages: 1. Improved accuracy: as compared to the direct frequency response method. 2. Less complexity: because it obtains the minima and maxima frequencies directly from the system equations. 3. Reliable prediction: it gives the complete information about the behaviour of the test system and its peaks and troughs before calculating its frequency response. 4. Good evaluation of network’s resistance: the proposed method determines the resistors of the network equivalent model as the real part of the impedance function magnitude at the minima frequency points. In this article, a general algorithm is developed to determine the frequency dependent network equivalent model parameters for any given system. Finally a four-bus test system is introduced to show the accuracy and the validation of the proposed method. For simplicity and convenience a comparison between the direct frequency response method and the proposed method, a two-bus system, is also studied in this work. Good results were obtained for network equivalent models for both the frequency and time domains.
392
Fuel and Energy Abstrscts
November 1999
99103721
Future cathode materials for lithium rechargeable
batteries Ritchie, A. G. et al. 1. Power Sources, 1999, 80, (l/2), 98-102. Lithium rechargeable batteries are now well established as power sources for portable equipment, such as portable telephones or computers. Future applications include electric vehicles. However, before they can be used for this, or other price-sensitive applications, new cathode materials of much lower cost are needed. Possible cathode materials are reviewed.
An investigation of the significance of singular value decomposition in power system dynamics
99103722
Hamdan, A. M. A. Electrical Power and Enew Systems, 1999,21, (6). 417424. A theoretical explanation of the basics of singular value decomposition (SVD) is given to justify their use in applications in power system dynamics and control. The minimum singular value of a matrix not only specifies the rank of the matrix, it also gives a measure of distance of the matrix from the set of matrices having a rank less than its rank. This distance is used as a measure to compare the ability of inputs to control a mode. It is also used to compare the observability of a mode in a signal and to synthesize the optimum signal to maximize the minimum singular value of the observability matrix. The ideas are applied to a single-machine infinite busbar system with a static var controller (SVC). The system has two inputs and the SVD is used to compare the effectiveness of the outputs in controlling a mode. It is also used to determine the best output (signal) to have maximum observability of a mode in it.
Load frequency control: a generalized neural network approach
99103723
Chaturvedia,
D. K. et al.
Electrical
Power and Energy
Systems,
1999, 21,
(6), 405-415.
Variation in load frequency is an index for normal operation of power systems. When load perturbation takes place anywhere in any area of the system, it will affect the frequency at other areas also. To control load frequency of power systems various controllers are used in different areas, but due to non-linearities in the system components and alternators, these controllers cannot control the frequency quickly and efficiently. Simple neural networks, which are in common use at present, have various drawbacks like large training time, requirement of large number of neurons, etc. The present work deals with the development of a non-linear neural network controller using a generalized neural network. The drawbacks of existing neural networks have been overcome in the generalized neuron structure, which has been developed to control the deviations in load frequency of a power system.
Manufacture of graphite material for high-capacity secondary nonaqueous-electrolyte battery anode
99103724
Tamaki, T. and Nakajima, H. Jpn. Kokai Tokkyo Koho JP 11 97,019 [99 97,019] (Cl. HOlM4/58), 9 Apr 1999, Appl. 97/268,240, 16 Sep 1997, 10 pp. (In Japanese) The following steps comprise the manufacturing process: (1) forming milled carbon fibres having average particle size 8-50 pm by carbonizing mesophase pitch fibres at 400-1500°C in an inert gas atmosphere and milling, (2) forming a pitch-boron compound mixed-carbide having average particle size 8-50/Lm by melting petroleum pitch or coal tar pitch with a boron compound and then pulverizing, (3) mixing the milled carbon fibres with the mixed carbide and (4) graphitizing the mixture at 12200°C in an inert gas atmosphere. The battery using the obtained graphite material has high charge/discharge capacity and energy density and shows good cycling performance.
99103725 Minimization of series reactive power loss for the voltage instability problems Hamzaoglu, F. and Makram, E. B. Elec. Power Syst. Res., 1999, 50, (3) 175-181. A method to find the location of series capacitors to minimize the total series reactive power loss (SRPL) of a power system is introduced. Since the increase in reactive power loss has been used as an indicator for the voltage instability, a newly developed indicator dQi”s,i_j/dK, is introduced to calculate the decrease in SRPL as a result of series compensation. The proposed method is simulated on one- and two-area systems and the results are discussed and found to be consistent. The divergence of the power flow solution is taken to check the increase in load margin, when the resulting lines are compensated. 99103726
Modelllng and simulation of lead-acid battery
charging Catherino, H. A. et al. J. Power Sources, 1999, 80, (l/2), 17-20. The US Army has shown a renewed interest in lead-acid SLI battery charging, spurred on by the recent shift to Army-wide use of ‘maintenance free’ batteries. Although the use of calcium-grid construction reduces the need for periodic water additions, using battery maintainers for extended float charging may cause an even greater problem. By charging at constant voltage, the batteries can slowly lose water if the charging is performed in the absence of suitable temperature compensation. This uncontrolled water loss is of particular significance in those batteries that do not permit access to the electrolyte. In this study, charging curves measured at constant current were obtained over a range of temperatures. The curves were modelled analytically by combining the individual effects of battery
Electrical power supply and utilization (scientific, technical)
electric field at the ground level. The charge simulation method (CSM), with complex charges and complex boundary conditions, is used to model the above mentioned systems with a great accuracy.
Electrochemical characteristics of the interface between the metal hydride electrode and electrolyte for an advanced nickel/metal hydride battery
99103716
Han, .I. et al. .I. Power Sources, 1999, 80, (l/2), 39-4.5. In a nickel/metal hydride (MH) battery, the characteristics of the negative electrode are related to the charge transfer and mass transfer processes at the interface between the MH electrode and the electrolyte. With increasing number of charge/discharge cycles, the MH alloy powders micro-crack into particles that are several microns in diameter and this then influences the exchange current density. A polarization experiment was used to analyse the charge transfer and mass transfer processes. The exchange current densities of uncoated and palladium-coated Mm09sTiaOs. NiJ.ssCoo.4sMno.3SAl~~,~s alloy electrodes increase with increasing number of charge/discharge cycles before reaching a constant value after 20-30 cycles.
99193717
An environmental aircraft battery (EAB)
Erbacher, J. K. J. Power Sources, 1999, 80, (l/2), 26.5-271. The Battery Branch of the US Air Force Research Laboratory began the development of an environmental aircraft battery (EAB) to replace existing nickel/cadmium (Ni-Cd) and sealed lead/acid (SLA) batteries to minimize or eliminate use of environmentally hazardous battery materials by the USAF. A three-phase development contract was awarded in 1996 to replace the cadmium in nickel-cadmium batteries with a metal hydride (MH) anode. Designs, materials, space battery technology, and results on commercial and government battery programmes were evaluated in the Phase I, Feasibility Analysis. Bipolar and prismatic designs were selected for Phase II development. Materials and cell test data are presented.
99163716 Environmental assessment of vanadium redox and lead-acid batteries for stationary energy storage Rydh, C. J. J. Power Sources, 1999, 80, (l/2), 21-29. Using a life cycle assessment approach, the environmental impact of both the vanadium redox battery (vanadium battery) and the lead-acid battery for use in stationary applications has been evaluated. In this study, the calculated environmental impact was lower for the vanadium battery than for the lead-acid one. The net energy storage efficiency of the vanadium battery was greater due to lower primary energy needs during the life cycle. Favourable characteristics such as long cycle-life, good availability of resources and recycling ability justify the development and commercialization of the vanadium battery.
Fast nodal assessment of static voltage stability 99103719 including contingency analysis Prada,
R. B. and dos Santos,
J. 0. R.
Electric
Power Systems Research,
1999, 51, (l), 55-59.
A nodal static voltage stability evaluation analytical tool for electric power systems is presented. The method is based on a straightforward physical characterization of the voltage stability phenomena. Emphasis is given to numerical calculation aspects leading to computational efficiency, necessary when leading with real life networks and contingency analysis. The method was able to detect real voltage stability problems in the Brazilian system, which substantiates its applicability and adequacy.
Frequency dependent network equivalents for 99103720 electromagnetic transient studies Ibrahima,
A. I. and Salama, M. M. A.
Electrical Power and Energy Systems,
1999, 21, (6), 395-404.
In electromagnetic transient studies, only a small part of an ac power system can be modelled in detail. The remaining parts of the system should be reduced to an equivalent model. Different methods were developed to generate frequency dependent network equivalents. This paper presents a novel approach for obtaining network equivalents for ac power systems using the QZ algorithm. The proposed method obtains accurate resonant frequencies directly from the system equations to be used in finding the network equivalent parameters. Also, the proposed method is a good tool to predict the system response. The use of the QZ algorithm in the creation of the network equivalent model gives the following advantages: 1. Improved accuracy: as compared to the direct frequency response method. 2. Less complexity: because it obtains the minima and maxima frequencies directly from the system equations. 3. Reliable prediction: it gives the complete information about the behaviour of the test system and its peaks and troughs before calculating its frequency response. 4. Good evaluation of network’s resistance: the proposed method determines the resistors of the network equivalent model as the real part of the impedance function magnitude at the minima frequency points. In this article, a general algorithm is developed to determine the frequency dependent network equivalent model parameters for any given system. Finally a four-bus test system is introduced to show the accuracy and the validation of the proposed method. For simplicity and convenience a comparison between the direct frequency response method and the proposed method, a two-bus system, is also studied in this work. Good results were obtained for network equivalent models for both the frequency and time domains.
392
Fuel and Energy Abstrscts
November 1999
99103721
Future cathode materials for lithium rechargeable
batteries Ritchie, A. G. et al. 1. Power Sources, 1999, 80, (l/2), 98-102. Lithium rechargeable batteries are now well established as power sources for portable equipment, such as portable telephones or computers. Future applications include electric vehicles. However, before they can be used for this, or other price-sensitive applications, new cathode materials of much lower cost are needed. Possible cathode materials are reviewed.
An investigation of the significance of singular value decomposition in power system dynamics
99103722
Hamdan, A. M. A. Electrical Power and Enew Systems, 1999,21, (6). 417424. A theoretical explanation of the basics of singular value decomposition (SVD) is given to justify their use in applications in power system dynamics and control. The minimum singular value of a matrix not only specifies the rank of the matrix, it also gives a measure of distance of the matrix from the set of matrices having a rank less than its rank. This distance is used as a measure to compare the ability of inputs to control a mode. It is also used to compare the observability of a mode in a signal and to synthesize the optimum signal to maximize the minimum singular value of the observability matrix. The ideas are applied to a single-machine infinite busbar system with a static var controller (SVC). The system has two inputs and the SVD is used to compare the effectiveness of the outputs in controlling a mode. It is also used to determine the best output (signal) to have maximum observability of a mode in it.
Load frequency control: a generalized neural network approach
99103723
Chaturvedia,
D. K. et al.
Electrical
Power and Energy
Systems,
1999, 21,
(6), 405-415.
Variation in load frequency is an index for normal operation of power systems. When load perturbation takes place anywhere in any area of the system, it will affect the frequency at other areas also. To control load frequency of power systems various controllers are used in different areas, but due to non-linearities in the system components and alternators, these controllers cannot control the frequency quickly and efficiently. Simple neural networks, which are in common use at present, have various drawbacks like large training time, requirement of large number of neurons, etc. The present work deals with the development of a non-linear neural network controller using a generalized neural network. The drawbacks of existing neural networks have been overcome in the generalized neuron structure, which has been developed to control the deviations in load frequency of a power system.
Manufacture of graphite material for high-capacity secondary nonaqueous-electrolyte battery anode
99103724
Tamaki, T. and Nakajima, H. Jpn. Kokai Tokkyo Koho JP 11 97,019 [99 97,019] (Cl. HOlM4/58), 9 Apr 1999, Appl. 97/268,240, 16 Sep 1997, 10 pp. (In Japanese) The following steps comprise the manufacturing process: (1) forming milled carbon fibres having average particle size 8-50 pm by carbonizing mesophase pitch fibres at 400-1500°C in an inert gas atmosphere and milling, (2) forming a pitch-boron compound mixed-carbide having average particle size 8-50/Lm by melting petroleum pitch or coal tar pitch with a boron compound and then pulverizing, (3) mixing the milled carbon fibres with the mixed carbide and (4) graphitizing the mixture at 12200°C in an inert gas atmosphere. The battery using the obtained graphite material has high charge/discharge capacity and energy density and shows good cycling performance.
99103725 Minimization of series reactive power loss for the voltage instability problems Hamzaoglu, F. and Makram, E. B. Elec. Power Syst. Res., 1999, 50, (3) 175-181. A method to find the location of series capacitors to minimize the total series reactive power loss (SRPL) of a power system is introduced. Since the increase in reactive power loss has been used as an indicator for the voltage instability, a newly developed indicator dQi”s,i_j/dK, is introduced to calculate the decrease in SRPL as a result of series compensation. The proposed method is simulated on one- and two-area systems and the results are discussed and found to be consistent. The divergence of the power flow solution is taken to check the increase in load margin, when the resulting lines are compensated. 99103726
Modelllng and simulation of lead-acid battery
charging Catherino, H. A. et al. J. Power Sources, 1999, 80, (l/2), 17-20. The US Army has shown a renewed interest in lead-acid SLI battery charging, spurred on by the recent shift to Army-wide use of ‘maintenance free’ batteries. Although the use of calcium-grid construction reduces the need for periodic water additions, using battery maintainers for extended float charging may cause an even greater problem. By charging at constant voltage, the batteries can slowly lose water if the charging is performed in the absence of suitable temperature compensation. This uncontrolled water loss is of particular significance in those batteries that do not permit access to the electrolyte. In this study, charging curves measured at constant current were obtained over a range of temperatures. The curves were modelled analytically by combining the individual effects of battery