Frequency is one of the most important measures of the status of a power system, especially for s... more Frequency is one of the most important measures of the status of a power system, especially for structurally weak and rapidly growing power systems. Thus, frequency monitoring is a desirable practice to ensure reliability and provide data for analysis. This paper reports the joint work between Rensselaer Polytechnic Institute (RPI) and Abubakar Tafawa Balewa University (ATBU) to study frequency dynamics of small power systems. We describe the Frequency Disturbance Recorder (FDR) implementation experience at ATBU, Bauchi, Nigeria, and present analysis on the digital recordings provided by the FDR installed at this location. A proposal for a universitybased frequency monitoring network for Nigeria's power system is also presented. Such monitoring system will allow further investigations on the Nigerian system and ultimately enhance the understanding of the dynamics and control of structurally weak and rapidly growing power systems found in some developing countries.
Cancer is a leading public health problem worldwide. In many developing countries, cancer tends t... more Cancer is a leading public health problem worldwide. In many developing countries, cancer tends to present in predominantly advanced stages, to a certain extent due to lack of comprehensive screening and poor access to efficient management. This study was carried out to describe the pattern of cancers managed in the Department of Radiotherapy and Oncology in Usmanu Danfodiyo University Teaching Hospital Sokoto, North-western Nigeria. This was a cross-sectional descriptive study involving patients with malignancies that attended the new Oncology Department of the Usman Danfodiyo University Teaching Hospital Sokoto, North-West Nigeria for the period of one year (June 2013 - May 2014). The data was analyzed using SPSS (versions 20). A total of 210 patients with complete records met the criteria for the study. Majority 162 (77.1%) were females with a mean age of 45.68±12.4 years. The male patients were 48 (22.9%) with mean age 46.27±16.5. The spectrum of malignant lesions observed were cancer of the cervix 77 (36.67%), breast cancer 74 (35.24%), nasopharyngeal cancer 20 (9.52%), cancer of the larynx 18 (8.57%) and rectal cancer 14 (6.67%). Late presentation was most common with 6 (3%), 101 (49.8%) and 58 (28.6%) patients presenting at stage I, III and IV, respectively. The study demonstrates that Cancer of the cervix is the leading malignancy in the study population.
2009 IEEE Power & Energy Society General Meeting, 2009
Frequency is one of the most important measures of the state of a power system, especially for st... more Frequency is one of the most important measures of the state of a power system, especially for structurally weak and rapidly growing power systems. Thus, frequency monitoring is a desirable practice to ensure reliability and provide data for analysis. This paper reports the joint work between Abubakar Tafawa Balewa University (ATBU) and Rensselaer Polytechnic Institute (RPI) to study frequency dynamics of a relative small power system. We describe the Frequency Disturbance Recorder (FDR) implementation experience at ATBU, Bauchi, Nigeria, and present analysis on the digital recordings obtained by the FDR. A proposal for a university-based frequency monitoring network for the Nigerian power system is also presented. Such monitoring system will allow further investigations on the Nigerian system and ultimately enhance the understanding of the dynamics and control of structurally weak and rapidly growing power systems found in many developing countries.
IEEE Power Engineering Society General Meeting, 2004., 2004
This paper presents a novel load frequency control design approach for a two-area power system th... more This paper presents a novel load frequency control design approach for a two-area power system that relies on unsupervised and supervised learning neural network structure. Central to this approach is the prediction of the load disturbance of each area at every minute interval that is uniquely assigned to a cluster via unsupervised learning process. The controller feedback gains corresponding to each cluster center are determined using modal control technique. Thereafter, supervised learning neural network (SLNN) is employed to learn the mapping between each cluster center and its feedback gains. A real time load disturbance in either or both areas activates the appropriate SLNN to generate the corresponding feedback gains. The effectiveness of the control framework is evaluated on the Nigerian hydrothermal system. Several far-reaching simulation results obtained from the test system are presented and discussed to highlight the advantages of the proposed approach.
2003 IEEE Power Engineering Society General Meeting (IEEE Cat. No.03CH37491), 2003
In this paper, the application of a novel and computationally enhances genetic algorithm (GA) for... more In this paper, the application of a novel and computationally enhances genetic algorithm (GA) for solving the reactive power dispatch problem is presented. In order to attain a significant reduction in the computational time of GA, a systematic procedure of reactive power control device pre-selection mechanism is herein proposed to choose a-priori subsets of the available control devices, which maximally
2007 International Conference on Intelligent Systems Applications to Power Systems, 2007
This paper presents the comparative application of two metaheuristic approaches: Differential Evo... more This paper presents the comparative application of two metaheuristic approaches: Differential Evolution (DE) and Particle Swarm Optimization (PSO) to the solution of the reactive power and voltage control problem. Efficient distribution of reactive power in an electric network leads to minimization of the system losses and improvement of the system voltage profile. It can be achieved by varying the excitation of generators or the on-load tap changer positions of transformers as well as by switching of discrete portions of inductors or capacitors etc. This constitutes a typical mixed integer non-linear optimization problem for the solution of which metaheuristic techniques have proven well suited in principle. The feasibility, effectiveness and generic nature of both DE and PSO approaches investigated are exemplarily demonstrated on the Nigerian grid system and the New England power system. Comparisons were made between the two approaches in terms of the solution quality and convergence characteristics. The simulation results revealed that both approaches were able to remove the voltage limit violations, but PSO procured in some instances slightly higher power loss reduction as compared with DE; on the other hand DE required a lower number of function evaluations as compared with PSO. Consideration of computational effort is relevant for potential real time on line application.
2007 IEEE Power Engineering Society General Meeting, 2007
The goal of reactive power dispatch is to minimize the system losses and improve the system volta... more The goal of reactive power dispatch is to minimize the system losses and improve the system voltage profiles at all times. This is achieved by adjusting various generating units' excitation systems continuously, discrete tap positions of on-load tap changers of transformers as well as switching of correct doses of inductors or capacitors. This is a mixed integer non-linear optimization problem. In this paper, the differential evolution (DE), a novel evolutionary computation technique which was originally designed for continuous problems is applied to solve this problem. DE appears to ally qualities of established computational intelligence (CI) techniques with a more striking computational performance, thus suggesting the possibility of having the potential for on line applications in the control center; comparison work with other techniques is presently conducted. The developed tool was demonstrated on the Nigerian power system grid for three case scenarios preset on the power world simulator which was linked with DE for power flow calculation (fitness check of solutions). The results achieved revealed that DE procured a significant reduction of real power losses while simultaneously keeping the voltage profiles within the acceptable limits.
IEEE Power Engineering Society General Meeting, 2005, 2005
The main focus of this paper is on the application of Genetic Algorithm (GA) to search for an opt... more The main focus of this paper is on the application of Genetic Algorithm (GA) to search for an optimal solution to a realistically formulated economic dispatch (ED) problem. GA is a global search technique based on principles inspired from the genetic and evolution mechanism observed in natural biological systems. A major drawback of the conventional GA (CGA) approach is that it can be time consuming. The micro-GA (µGA) approach has been proposed as a better time efficient alternative for some engineering problems. The effectiveness of CGA and µGA to solving ED problem is initially verified on an IEEE 3generating unit, 6-bus test system. Simulation results obtained on this network using CGA and µGA validate their effectiveness when compared with the published results obtained via the classical and the Hopfield neural network approaches. Finally, both GA approaches have been successfully applied to the coordination of the Nigerian 31-bus system fed by four thermal and three hydro generating units. Herein, use has been made of the loss formula developed for the Nigerian system from several power flow studies. For the Nigerian case study, the µGA is shown to exhibit superior performance than the CGA from both optimal generation allocations and computational time viewpoints.
IEEE Power Engineering Society General Meeting, 2005, 2005
In this paper, a micro-genetic based approach to the optimization of reactive power and voltage p... more In this paper, a micro-genetic based approach to the optimization of reactive power and voltage profiles improvement and real power loss minimization is presented. The reactive power control devices such as generators, tap positions of on-load tap changer of transformers, shunt reactors are used to correct voltage limits violations while simultaneously reducing the system real power losses. Genetic Algorithms (GAs) are well-known global search techniques anchored on the mechanisms of natural selection and genetics. Because of the time intensive nature of the conventional GA, the micro-GA is proposed as a more time efficient alternative. The feasibility and effectiveness of the developed algorithm is tested and verified on the Nigerian grid power system for three case studies scenarios preset in the power world simulator. The far-reaching simulation results that validate the effectiveness of the developed tool are presented and discussed in depth.
2011 5th International Power Engineering and Optimization Conference, 2011
... Grid System Considering Voltage and Line Flow Constraints Rasa> Soreme&... more ... Grid System Considering Voltage and Line Flow Constraints Rasa> Soreme>un, Abdullah Asuhaimi Mohd Zin, Abdullahi Amoo, Ganiyu Ba>are, Usman Aliyu ... 5 References [1] Sambo, AS 2008: Matching Electricity Supply with Demand in Nigeria, a 4th Quarter Journal of ECN. ...
2012 IEEE International Power Engineering and Optimization Conference, 2012
ABSTRACT A lot of things determine the life expectancy of a transformer such as overheating due t... more ABSTRACT A lot of things determine the life expectancy of a transformer such as overheating due to triplen harmonics, unbalanced loading, vibro-acoustic noise and so on. For this reason, this paper presents the investigation carried out on the magnetostrictive sound of Bauchi, 30/40 MVA, 132/33 KV substation transformer. Readings were taken using standard audio recording instrument for various loading and voltage conditions in the mornings, afternoons and nights for six days and the offline assessment was carried out using digital spectrum analyzer. However, no access could be gained to the variation of certain important parameters, like changing of core dimensions, loosing or tightening of core and so on, for the substation transformer in-situ in the substation hence separate laboratory test transformers were used in the assessment of the effect of core damping pressure, construction looseness and transformer saturation on the vibro-acoustic noise. Conclusively, increasing the operation voltage of transformer tends to produce more magnetostriction effect while loosening core lamination increases the energy losses.
2009 15th International Conference on Intelligent System Applications to Power Systems, 2009
An optimal transient controller for a synchronous generator in a multi-machine power system is de... more An optimal transient controller for a synchronous generator in a multi-machine power system is designed using the concept of flatness-based feedback linearization in this paper. The computation of the flat output and corresponding controller for reduced order model of the synchronous generator is presented. The required feedback gains used to close the linearization loop is optimized using particle swarm optimization for maximum damping. Typical results obtained for transient disturbances on a two-area, four-generator power system equipped with the proposed controller on one generator and conventional power system stabilizers on the remaining generators are presented. The effectiveness of the flatness-based controller for multi-machine power systems is discussed.
2007 IEEE Power Engineering Society General Meeting, 2007
This paper focuses attention on the concept of flatness-based feedback linearization and its prac... more This paper focuses attention on the concept of flatness-based feedback linearization and its practical application to the design of an optimal transient controller for a synchronous machine. The feedback linearization scheme of interest requires the generation of a flat output from which the feedback control law can easily be designed. Thus the computation of the flat output for reduced order model of the synchronous machine with simplified turbine dynamics is hereby presented. The corresponding linearized compensator is derived as well as the nonlinear controller for transient stabilization of a synchronous machine subjected to large disturbances. The transient behavior of a single machine equipped with the so designed nonlinear controllers feeding an infinite bus is illustrated via simulation in Matlab environment. The results obtained for transient disturbances on the single machine infinite bus system (SMIBS) are presented and compared with other control algorithms to demonstrate the effectiveness of the proposed scheme.
Proceedings of International Conference on Control Applications, 1995
Effects of unwanted distortions on power system network voltage and current phasor quantities dur... more Effects of unwanted distortions on power system network voltage and current phasor quantities during faults could adversely affect the reliability and discrimination of protective relays. This paper is principally concerned with the digital relaying concept based on multi-state Kalman filtering approach to minimise such problems. It seeks to characterise the effects of noise, harmonics and DC offset distortions on Kalman
A modified discrete particle swarm optimisation (MDPSO) algorithm to generate optimal preventive ... more A modified discrete particle swarm optimisation (MDPSO) algorithm to generate optimal preventive maintenance schedule of generating units for economical and reliable operation of a power system, while satisfying system load demand and crew constraints, is presented. Discrete particle swarm optimisation (DPSO) is known to effectively solve large-scale multi-objective optimisation problems and has been widely applied in power system. The MDPSO proposed for the generator maintenance scheduling optimisation problem generates optimal and feasible solutions and overcomes the limitations of the conventional methods, such as extensive computational effort, which increases exponentially as the size of the problem increases. The efficacy of the proposed algorithm is illustrated and compared with the genetic algorithm (GA) and DPSO in two case studies -a 21-unit test system and a 49-unit system feeding the Nigerian national grid. The MDPSO algorithm is found to generate schedules with comparatively higher system reliability indices than those obtained with GA and DPSO.
... This process, in turn, favors the propagation of genes of those animals that have been succes... more ... This process, in turn, favors the propagation of genes of those animals that have been successful in their for-aging strategies. ... Page 5. DAS et al.: BIO-INSPIRED ALGORITHMS FOR THE DESIGN OF POWER SYSTEM STABILIZERS: SPPSO AND BFA 1449 ...
Power Engineering Society, IEEE General Meeting, 2006
In determining the correct operation of relays of a protection scheme, proper representation of i... more In determining the correct operation of relays of a protection scheme, proper representation of instrument transformers and their behavior in conditions where there can be transient is very critical. This paper presents a simulation model for assessing the transient performance of capacitive voltage transformers (CVTs). In order to test the validity of the developed model, four CVT operational conditions are
The application of advanced signal processing techniques to power system measurement data for the... more The application of advanced signal processing techniques to power system measurement data for the estimation of dynamic properties has been a research subject for over two decades. Several techniques have been applied to transient (or ringdown) data, ambient data, and to probing data. Some of these methodologies have been included in off-line analysis software, and are now being incorporated into software tools used in control rooms for monitoring the near real-time behavior of power system dynamics. In this paper we illustrate the practical application of some ambient analysis methods for electromechanical mode estimation in different power systems. We apply these techniques to phasor measurement unit (PMU) data from stored archives of several hours originating from the US Eastern Interconnection, the Western Electricity Coordinating Council, the Nordic Power System, and time-synchronized Frequency Disturbance Recorder (FDR) data from Nigeria. It is shown that available signal processing tools are readily applicable for analysis of different power systems, regardless of their specific dynamic characteristics. The discussions and results in this paper are of value to power system operators and planners as they provide information of the applicability of these techniques via readily available signal processing tools, and in addition, it is shown how to critically analyze the results obtained with these methods. Index Terms Power system oscillations, power system identification, power system parameter estimation, power system monitoring, application of signal processing techniques, synchronized phasor measurements, power system measurements, small-signal stability.
This paper reports on an ongoing research effort between researchers in North America and Africa ... more This paper reports on an ongoing research effort between researchers in North America and Africa on the study of the dynamics of loosely regulated and rapidly growing power systems, with focus on the Nigerian power network. A description of the implementation of Virginia Tech's FDR (Frequency Disturbance Recorder) at Bauchi, Nigeria is provided. We discuss the nature of the frequency dynamics observed throughout multiple hours of a day in Nigeria and other power systems. To cater to the loosely regulated nature of the system frequency in Nigeria, we propose an appropriate method for signal conditioning which prepares the data for ambient analysis. Parametric and nonparametric block processing techniques are applied to prolonged frequency recordings ranging from 8 to 19 hours, and estimates of modal frequencies and damping are obtained by computing power spectrum densities and applying a mode meter algorithm to the ambient data. The estimated modes from ambient analysis are in agreement with other studies based on power system models.
This paper reports and assesses a semester-long activity-based approach to learning social resear... more This paper reports and assesses a semester-long activity-based approach to learning social research methods. Unlike more typical research methods classes which depend on lectures, readings, and tests, this class used a series of projects that moved students out of the classroom into a progressive series of research activities using Istanbul itself as the primary locale for learning. From the first session of the semester, two related research questions, "What makes a successful street beggar?" and "How do people in Istanbul interact with street beggars," guided a collaborative research project involving more than forty students and their instructor. Students used observation, role-taking, interview construction and gathering interviews, survey construction and administration, and data analysis as research tactics to address the research questions. Students report that they learned more through these activities than through usual classroom learning and they endorsed the approach for their other classes. Suggestions for adapting this approach for other classes are listed.
Frequency is one of the most important measures of the status of a power system, especially for s... more Frequency is one of the most important measures of the status of a power system, especially for structurally weak and rapidly growing power systems. Thus, frequency monitoring is a desirable practice to ensure reliability and provide data for analysis. This paper reports the joint work between Rensselaer Polytechnic Institute (RPI) and Abubakar Tafawa Balewa University (ATBU) to study frequency dynamics of small power systems. We describe the Frequency Disturbance Recorder (FDR) implementation experience at ATBU, Bauchi, Nigeria, and present analysis on the digital recordings provided by the FDR installed at this location. A proposal for a universitybased frequency monitoring network for Nigeria's power system is also presented. Such monitoring system will allow further investigations on the Nigerian system and ultimately enhance the understanding of the dynamics and control of structurally weak and rapidly growing power systems found in some developing countries.
Cancer is a leading public health problem worldwide. In many developing countries, cancer tends t... more Cancer is a leading public health problem worldwide. In many developing countries, cancer tends to present in predominantly advanced stages, to a certain extent due to lack of comprehensive screening and poor access to efficient management. This study was carried out to describe the pattern of cancers managed in the Department of Radiotherapy and Oncology in Usmanu Danfodiyo University Teaching Hospital Sokoto, North-western Nigeria. This was a cross-sectional descriptive study involving patients with malignancies that attended the new Oncology Department of the Usman Danfodiyo University Teaching Hospital Sokoto, North-West Nigeria for the period of one year (June 2013 - May 2014). The data was analyzed using SPSS (versions 20). A total of 210 patients with complete records met the criteria for the study. Majority 162 (77.1%) were females with a mean age of 45.68±12.4 years. The male patients were 48 (22.9%) with mean age 46.27±16.5. The spectrum of malignant lesions observed were cancer of the cervix 77 (36.67%), breast cancer 74 (35.24%), nasopharyngeal cancer 20 (9.52%), cancer of the larynx 18 (8.57%) and rectal cancer 14 (6.67%). Late presentation was most common with 6 (3%), 101 (49.8%) and 58 (28.6%) patients presenting at stage I, III and IV, respectively. The study demonstrates that Cancer of the cervix is the leading malignancy in the study population.
2009 IEEE Power & Energy Society General Meeting, 2009
Frequency is one of the most important measures of the state of a power system, especially for st... more Frequency is one of the most important measures of the state of a power system, especially for structurally weak and rapidly growing power systems. Thus, frequency monitoring is a desirable practice to ensure reliability and provide data for analysis. This paper reports the joint work between Abubakar Tafawa Balewa University (ATBU) and Rensselaer Polytechnic Institute (RPI) to study frequency dynamics of a relative small power system. We describe the Frequency Disturbance Recorder (FDR) implementation experience at ATBU, Bauchi, Nigeria, and present analysis on the digital recordings obtained by the FDR. A proposal for a university-based frequency monitoring network for the Nigerian power system is also presented. Such monitoring system will allow further investigations on the Nigerian system and ultimately enhance the understanding of the dynamics and control of structurally weak and rapidly growing power systems found in many developing countries.
IEEE Power Engineering Society General Meeting, 2004., 2004
This paper presents a novel load frequency control design approach for a two-area power system th... more This paper presents a novel load frequency control design approach for a two-area power system that relies on unsupervised and supervised learning neural network structure. Central to this approach is the prediction of the load disturbance of each area at every minute interval that is uniquely assigned to a cluster via unsupervised learning process. The controller feedback gains corresponding to each cluster center are determined using modal control technique. Thereafter, supervised learning neural network (SLNN) is employed to learn the mapping between each cluster center and its feedback gains. A real time load disturbance in either or both areas activates the appropriate SLNN to generate the corresponding feedback gains. The effectiveness of the control framework is evaluated on the Nigerian hydrothermal system. Several far-reaching simulation results obtained from the test system are presented and discussed to highlight the advantages of the proposed approach.
2003 IEEE Power Engineering Society General Meeting (IEEE Cat. No.03CH37491), 2003
In this paper, the application of a novel and computationally enhances genetic algorithm (GA) for... more In this paper, the application of a novel and computationally enhances genetic algorithm (GA) for solving the reactive power dispatch problem is presented. In order to attain a significant reduction in the computational time of GA, a systematic procedure of reactive power control device pre-selection mechanism is herein proposed to choose a-priori subsets of the available control devices, which maximally
2007 International Conference on Intelligent Systems Applications to Power Systems, 2007
This paper presents the comparative application of two metaheuristic approaches: Differential Evo... more This paper presents the comparative application of two metaheuristic approaches: Differential Evolution (DE) and Particle Swarm Optimization (PSO) to the solution of the reactive power and voltage control problem. Efficient distribution of reactive power in an electric network leads to minimization of the system losses and improvement of the system voltage profile. It can be achieved by varying the excitation of generators or the on-load tap changer positions of transformers as well as by switching of discrete portions of inductors or capacitors etc. This constitutes a typical mixed integer non-linear optimization problem for the solution of which metaheuristic techniques have proven well suited in principle. The feasibility, effectiveness and generic nature of both DE and PSO approaches investigated are exemplarily demonstrated on the Nigerian grid system and the New England power system. Comparisons were made between the two approaches in terms of the solution quality and convergence characteristics. The simulation results revealed that both approaches were able to remove the voltage limit violations, but PSO procured in some instances slightly higher power loss reduction as compared with DE; on the other hand DE required a lower number of function evaluations as compared with PSO. Consideration of computational effort is relevant for potential real time on line application.
2007 IEEE Power Engineering Society General Meeting, 2007
The goal of reactive power dispatch is to minimize the system losses and improve the system volta... more The goal of reactive power dispatch is to minimize the system losses and improve the system voltage profiles at all times. This is achieved by adjusting various generating units' excitation systems continuously, discrete tap positions of on-load tap changers of transformers as well as switching of correct doses of inductors or capacitors. This is a mixed integer non-linear optimization problem. In this paper, the differential evolution (DE), a novel evolutionary computation technique which was originally designed for continuous problems is applied to solve this problem. DE appears to ally qualities of established computational intelligence (CI) techniques with a more striking computational performance, thus suggesting the possibility of having the potential for on line applications in the control center; comparison work with other techniques is presently conducted. The developed tool was demonstrated on the Nigerian power system grid for three case scenarios preset on the power world simulator which was linked with DE for power flow calculation (fitness check of solutions). The results achieved revealed that DE procured a significant reduction of real power losses while simultaneously keeping the voltage profiles within the acceptable limits.
IEEE Power Engineering Society General Meeting, 2005, 2005
The main focus of this paper is on the application of Genetic Algorithm (GA) to search for an opt... more The main focus of this paper is on the application of Genetic Algorithm (GA) to search for an optimal solution to a realistically formulated economic dispatch (ED) problem. GA is a global search technique based on principles inspired from the genetic and evolution mechanism observed in natural biological systems. A major drawback of the conventional GA (CGA) approach is that it can be time consuming. The micro-GA (µGA) approach has been proposed as a better time efficient alternative for some engineering problems. The effectiveness of CGA and µGA to solving ED problem is initially verified on an IEEE 3generating unit, 6-bus test system. Simulation results obtained on this network using CGA and µGA validate their effectiveness when compared with the published results obtained via the classical and the Hopfield neural network approaches. Finally, both GA approaches have been successfully applied to the coordination of the Nigerian 31-bus system fed by four thermal and three hydro generating units. Herein, use has been made of the loss formula developed for the Nigerian system from several power flow studies. For the Nigerian case study, the µGA is shown to exhibit superior performance than the CGA from both optimal generation allocations and computational time viewpoints.
IEEE Power Engineering Society General Meeting, 2005, 2005
In this paper, a micro-genetic based approach to the optimization of reactive power and voltage p... more In this paper, a micro-genetic based approach to the optimization of reactive power and voltage profiles improvement and real power loss minimization is presented. The reactive power control devices such as generators, tap positions of on-load tap changer of transformers, shunt reactors are used to correct voltage limits violations while simultaneously reducing the system real power losses. Genetic Algorithms (GAs) are well-known global search techniques anchored on the mechanisms of natural selection and genetics. Because of the time intensive nature of the conventional GA, the micro-GA is proposed as a more time efficient alternative. The feasibility and effectiveness of the developed algorithm is tested and verified on the Nigerian grid power system for three case studies scenarios preset in the power world simulator. The far-reaching simulation results that validate the effectiveness of the developed tool are presented and discussed in depth.
2011 5th International Power Engineering and Optimization Conference, 2011
... Grid System Considering Voltage and Line Flow Constraints Rasa> Soreme&... more ... Grid System Considering Voltage and Line Flow Constraints Rasa> Soreme>un, Abdullah Asuhaimi Mohd Zin, Abdullahi Amoo, Ganiyu Ba>are, Usman Aliyu ... 5 References [1] Sambo, AS 2008: Matching Electricity Supply with Demand in Nigeria, a 4th Quarter Journal of ECN. ...
2012 IEEE International Power Engineering and Optimization Conference, 2012
ABSTRACT A lot of things determine the life expectancy of a transformer such as overheating due t... more ABSTRACT A lot of things determine the life expectancy of a transformer such as overheating due to triplen harmonics, unbalanced loading, vibro-acoustic noise and so on. For this reason, this paper presents the investigation carried out on the magnetostrictive sound of Bauchi, 30/40 MVA, 132/33 KV substation transformer. Readings were taken using standard audio recording instrument for various loading and voltage conditions in the mornings, afternoons and nights for six days and the offline assessment was carried out using digital spectrum analyzer. However, no access could be gained to the variation of certain important parameters, like changing of core dimensions, loosing or tightening of core and so on, for the substation transformer in-situ in the substation hence separate laboratory test transformers were used in the assessment of the effect of core damping pressure, construction looseness and transformer saturation on the vibro-acoustic noise. Conclusively, increasing the operation voltage of transformer tends to produce more magnetostriction effect while loosening core lamination increases the energy losses.
2009 15th International Conference on Intelligent System Applications to Power Systems, 2009
An optimal transient controller for a synchronous generator in a multi-machine power system is de... more An optimal transient controller for a synchronous generator in a multi-machine power system is designed using the concept of flatness-based feedback linearization in this paper. The computation of the flat output and corresponding controller for reduced order model of the synchronous generator is presented. The required feedback gains used to close the linearization loop is optimized using particle swarm optimization for maximum damping. Typical results obtained for transient disturbances on a two-area, four-generator power system equipped with the proposed controller on one generator and conventional power system stabilizers on the remaining generators are presented. The effectiveness of the flatness-based controller for multi-machine power systems is discussed.
2007 IEEE Power Engineering Society General Meeting, 2007
This paper focuses attention on the concept of flatness-based feedback linearization and its prac... more This paper focuses attention on the concept of flatness-based feedback linearization and its practical application to the design of an optimal transient controller for a synchronous machine. The feedback linearization scheme of interest requires the generation of a flat output from which the feedback control law can easily be designed. Thus the computation of the flat output for reduced order model of the synchronous machine with simplified turbine dynamics is hereby presented. The corresponding linearized compensator is derived as well as the nonlinear controller for transient stabilization of a synchronous machine subjected to large disturbances. The transient behavior of a single machine equipped with the so designed nonlinear controllers feeding an infinite bus is illustrated via simulation in Matlab environment. The results obtained for transient disturbances on the single machine infinite bus system (SMIBS) are presented and compared with other control algorithms to demonstrate the effectiveness of the proposed scheme.
Proceedings of International Conference on Control Applications, 1995
Effects of unwanted distortions on power system network voltage and current phasor quantities dur... more Effects of unwanted distortions on power system network voltage and current phasor quantities during faults could adversely affect the reliability and discrimination of protective relays. This paper is principally concerned with the digital relaying concept based on multi-state Kalman filtering approach to minimise such problems. It seeks to characterise the effects of noise, harmonics and DC offset distortions on Kalman
A modified discrete particle swarm optimisation (MDPSO) algorithm to generate optimal preventive ... more A modified discrete particle swarm optimisation (MDPSO) algorithm to generate optimal preventive maintenance schedule of generating units for economical and reliable operation of a power system, while satisfying system load demand and crew constraints, is presented. Discrete particle swarm optimisation (DPSO) is known to effectively solve large-scale multi-objective optimisation problems and has been widely applied in power system. The MDPSO proposed for the generator maintenance scheduling optimisation problem generates optimal and feasible solutions and overcomes the limitations of the conventional methods, such as extensive computational effort, which increases exponentially as the size of the problem increases. The efficacy of the proposed algorithm is illustrated and compared with the genetic algorithm (GA) and DPSO in two case studies -a 21-unit test system and a 49-unit system feeding the Nigerian national grid. The MDPSO algorithm is found to generate schedules with comparatively higher system reliability indices than those obtained with GA and DPSO.
... This process, in turn, favors the propagation of genes of those animals that have been succes... more ... This process, in turn, favors the propagation of genes of those animals that have been successful in their for-aging strategies. ... Page 5. DAS et al.: BIO-INSPIRED ALGORITHMS FOR THE DESIGN OF POWER SYSTEM STABILIZERS: SPPSO AND BFA 1449 ...
Power Engineering Society, IEEE General Meeting, 2006
In determining the correct operation of relays of a protection scheme, proper representation of i... more In determining the correct operation of relays of a protection scheme, proper representation of instrument transformers and their behavior in conditions where there can be transient is very critical. This paper presents a simulation model for assessing the transient performance of capacitive voltage transformers (CVTs). In order to test the validity of the developed model, four CVT operational conditions are
The application of advanced signal processing techniques to power system measurement data for the... more The application of advanced signal processing techniques to power system measurement data for the estimation of dynamic properties has been a research subject for over two decades. Several techniques have been applied to transient (or ringdown) data, ambient data, and to probing data. Some of these methodologies have been included in off-line analysis software, and are now being incorporated into software tools used in control rooms for monitoring the near real-time behavior of power system dynamics. In this paper we illustrate the practical application of some ambient analysis methods for electromechanical mode estimation in different power systems. We apply these techniques to phasor measurement unit (PMU) data from stored archives of several hours originating from the US Eastern Interconnection, the Western Electricity Coordinating Council, the Nordic Power System, and time-synchronized Frequency Disturbance Recorder (FDR) data from Nigeria. It is shown that available signal processing tools are readily applicable for analysis of different power systems, regardless of their specific dynamic characteristics. The discussions and results in this paper are of value to power system operators and planners as they provide information of the applicability of these techniques via readily available signal processing tools, and in addition, it is shown how to critically analyze the results obtained with these methods. Index Terms Power system oscillations, power system identification, power system parameter estimation, power system monitoring, application of signal processing techniques, synchronized phasor measurements, power system measurements, small-signal stability.
This paper reports on an ongoing research effort between researchers in North America and Africa ... more This paper reports on an ongoing research effort between researchers in North America and Africa on the study of the dynamics of loosely regulated and rapidly growing power systems, with focus on the Nigerian power network. A description of the implementation of Virginia Tech's FDR (Frequency Disturbance Recorder) at Bauchi, Nigeria is provided. We discuss the nature of the frequency dynamics observed throughout multiple hours of a day in Nigeria and other power systems. To cater to the loosely regulated nature of the system frequency in Nigeria, we propose an appropriate method for signal conditioning which prepares the data for ambient analysis. Parametric and nonparametric block processing techniques are applied to prolonged frequency recordings ranging from 8 to 19 hours, and estimates of modal frequencies and damping are obtained by computing power spectrum densities and applying a mode meter algorithm to the ambient data. The estimated modes from ambient analysis are in agreement with other studies based on power system models.
This paper reports and assesses a semester-long activity-based approach to learning social resear... more This paper reports and assesses a semester-long activity-based approach to learning social research methods. Unlike more typical research methods classes which depend on lectures, readings, and tests, this class used a series of projects that moved students out of the classroom into a progressive series of research activities using Istanbul itself as the primary locale for learning. From the first session of the semester, two related research questions, "What makes a successful street beggar?" and "How do people in Istanbul interact with street beggars," guided a collaborative research project involving more than forty students and their instructor. Students used observation, role-taking, interview construction and gathering interviews, survey construction and administration, and data analysis as research tactics to address the research questions. Students report that they learned more through these activities than through usual classroom learning and they endorsed the approach for their other classes. Suggestions for adapting this approach for other classes are listed.
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