Environment and Water Resource Management / 813: Modelling and Simulation / 814: Power and Energy Systems / 815: Health Informatics, 2014
The present Nigerian 330kV grid system is predominantly known to be unstable, fragile, and ill-co... more The present Nigerian 330kV grid system is predominantly known to be unstable, fragile, and ill-conditioned. This is due to rapid increase in the consumers demand for electricity and other technical factors. A network is said to be weak and ill-conditioned when it is deficit of reactive power, with low voltages below the nominal limit and has high R/X line ratios. To maintain a secure, efficient and economical operation of electrical power system and to meet the enormous demand by consumers, it becomes imperative to carry out real power flow control and its redirection. Presented in this paper is the application of phase shifting transformers to the Nigerian 330kV grid system for active power flow control. Newton Raphson Iterative algorithm was adopted for solving the power flow problems. Modified power flow algorithm was implemented by the application of phase shifter approach using Phase Shifting Transformers (PST). The phase shifting transformer was inserted one at a time on each of the four suitable transmission lines directly connected to the generator bus. These lines are between Benin to Osogbo (8-10), Alaoji to Onitsha (12-14), Benin to Onitsha (8-14), and Osogbo to Ikeja West (10-5). Results obtained show that, with the incorporation of PST, active power flow can be redirected between the two points in power system and hence, enhancing its operation in terms of efficiency and reduced system losses.
2010 International Conference on Advances in Energy Engineering, 2010
Large cascade blackouts are generally catastrophic both economically and socially, when they occu... more Large cascade blackouts are generally catastrophic both economically and socially, when they occur. In this work, a transmission constrained, 5-bus power grid was simulated using PowerWorld and the impact of lines outages on the violation of loading capacities of network links was studied. We use the Widest Path Algorithm(WPA) and Power Flow Redistribution Algorithm(PFRA) to redistribute power flow in the
Abstract This paper proposes a novel transmission line fault detection and classification scheme,... more Abstract This paper proposes a novel transmission line fault detection and classification scheme, based on a single-end measurements using time shift invariant property of a sinusoidal waveform. Various types of faults at different locations, fault resistance and fault ...
Abstract This paper presents a novel scheme for removing a decay-ing DC-offset from fault current... more Abstract This paper presents a novel scheme for removing a decay-ing DC-offset from fault current measurements in a faulted power transmission lines. The technique is based on Stationary Wavelet Transform (SWT). The performance of the scheme on two study cases ...
This paper presents a novel scheme for removing a decaying DC-offset from both current and voltag... more This paper presents a novel scheme for removing a decaying DC-offset from both current and voltage measurements irrespective of the time constant.The technique is based on stationary wavelet transform (SWT) cascaded with a differentiator. The performance of the scheme on two study cases is investigated; the statistical performance in relation to noise on a hypothetical signal, and a modeled segment of a utility network in South Africa. The proposed scheme is practically applied by testing it on a real life data obtained from Eskom's network. The result shows that the scheme is robust, and that it can remove any DC-offset. The output of the scheme can be used for fault detection, classification and location.
This paper proposes a novel transmission line fault location scheme, combining stationary wavelet... more This paper proposes a novel transmission line fault location scheme, combining stationary wavelet transform (SWT), determinant function feature (DFF), support vector machine (SVM) and support vector regression (SVR). Various types of faults at different locations, fault impedance and fault inception angles on a 400 kV, 361.297 km transmission line are investigated. The system only utilizes single-end measurements. DFF is used to extract distinctive fault features from 1/4 cycle of post fault signals after noise and the decaying DC offset have been eliminated by a filtering scheme based on SWT. A classifier (SVM) and regression (SVR) schemes are subsequently trained with features obtained from DFF. The scheme is then used in precise location of fault on the transmission line. The result shows that fault location on transmission lines can be determined rapidly and correctly irrespective of fault impedance.
... They have been shown to be an attractive and more systematic approach to learn linear or non-... more ... They have been shown to be an attractive and more systematic approach to learn linear or non-linear decision boundaries. SVR includes linear SVR and nonlinear SVR. In this paper, nonlinear SVR is used for estimating fault locations. ...
Environment and Water Resource Management / 813: Modelling and Simulation / 814: Power and Energy Systems / 815: Health Informatics, 2014
Many utilities suffer from High Technical and Non-Technical Energy Losses that, when combined, ca... more Many utilities suffer from High Technical and Non-Technical Energy Losses that, when combined, can exceed 30% of the total energy generated or imported. Studies have shown that the optimal total power losses in the distribution network (Primary and Secondary Distributions) range from between 6% and 12%. Sample studies of a number of utilities showed, however, that the secondary distribution network alone could have a loss that exceeds 12%. In this paper High Voltage Distribution System (HVDS) is proposed for analysis and implementation for Power Holding Company of Nigeria (PHCN) that is having relatively high technical loss problems in a section of the distribution network. The distribution of power at high voltage and supplying the customers directly through small size distribution transformers would be achieved. The load Flow equation for testing a practical situation is also presented.
The plan to integrate solar energy into the Nigerian grid is in conception and thirteen different... more The plan to integrate solar energy into the Nigerian grid is in conception and thirteen different locations within the country have been proposed for solar farm investment. In this paper, fourteen selected solar photovoltaic module types from different manufacturers were assessed to determine the optimum PV module for each of the locations. The optimum module was thereafter used to determine the technical feasibility and economic viability of the locations identified for solar investment in Nigeria. Technical assessments were performed using the reference yield, array yield, final system yield, performance ratio and capacity factor while the economic consideration was made using the levelized cost of energy and payback period. Sensitivity analyses were also carried out to identify the important relationships among the technical and economic parameters as they affect the proposed sites. Relevant findings reveal that final yield, performance ratio and capacity factor ranges between 4.0361 and 4.7972 kWh/kWp, 78.96-79.96% and 16.75-19.92%, respectively. It was also observed that the cost of energy and payback period are between 0.0524 and 0.0607 $/kWh and 10.18-10.42 years, respectively. The sensitivity analyses conducted across the selected sites demonstrate that levelized cost of electricity depends heavily on the electricity production in kWh/kWp. The result obtained also shows that increase in the installed capacity of the solar farm has no significant impact on its performance ratio and capacity factor of the farm. Out of fourteen solar modules that were used in the study, module index M 2 (Panasonic solar) provided the best result in terms of peak values of capacity factor and performance ratio at all the proposed sites.
The quasi-impedance source inverters/quasi-Z source inverters (Q-ZSIs) have shown improvement to ... more The quasi-impedance source inverters/quasi-Z source inverters (Q-ZSIs) have shown improvement to overwhelmed shortcomings of regular voltage-source inverters (VSIs) and current-source inverters (CSIs) in terms of efficiency and buck-boost type operations. The Q-ZSIs encapsulated several significant merits against conventional ZSIs, i.e., realized buck/boost, inversion and power conditioning in a single power stage with improved reliability. The conventional inverters have two major problems; voltage harmonics and boosting capability, which make it impossible to prefer for renewable generation and general-purpose applications such as drive acceleration. This work has proposed a Q-ZSI with five-level six switches coupled inverter. The proposed Q-ZSI has the merits of operation, reduced passive components, higher voltage boosting capability and high efficiency. The modified space vector pulse width modulation (PWM) developed to achieve the desired control on the impedance network and i...
Environment and Water Resource Management / 813: Modelling and Simulation / 814: Power and Energy Systems / 815: Health Informatics, 2014
This paper explores the use of reactive Power compensation to enhance voltage bus profiles for po... more This paper explores the use of reactive Power compensation to enhance voltage bus profiles for power system security in weak power system networks. Powerflow analysis is one of the tools used in this paper and it is modelled as a nonlinear problem which is solved using Newton-Raphson-based algorithm. Power-flow is performed in this paper to determine voltage magnitudes and angles at every bus, active and reactive powers, transmission losses for each of the branches in the network and total transmission losses of the network. Buses that have their voltage magnitude outside the prescribed acceptable limits (% 10  tolerance value) within the network are therefore identified. The magnitudes of the voltages at these buses are substantially improved when reactive power is injected. Total transmission loss on the line is also reduced to barest minimum after the compensation. MATLAB 2010a is used as a programming tool for this work. A weak meshed network of 28-bus system is used as a test system. The result of the simulation in this paper shows the effectiveness of reactive power compensation using a bank of capacitors in transmission power system networks.
Voltage stability assessment in power system has recently been a growing concern to power system ... more Voltage stability assessment in power system has recently been a growing concern to power system utilities due to blackout experienced in a couple of years in some developed and underdeveloped nations. This paper presents an alternative method which is based on the topology of the power network to identify weak load buses that are susceptible to voltage instability. The method makes use of the critical mode and the eigenvectors to determine the weak bus of the system. To determine the critical mode of the system, eigenvalue decomposition technique is used. Comparison analysis with the power flow based voltage collapse proximity index (VCPI) is performed to show the significance of the suggested approach. Results obtained show that voltage stability assessment in power system could as well be done using the structurally based approach as it saves time and reduces the computational burden compared with the traditional power flow based approach of VCPI.
Identification of weak buses in an electric power system is important for operational and plannin... more Identification of weak buses in an electric power system is important for operational and planning purposes. In this paper, a framework that uses the variance of the magnitude of voltage at load buses when reactive power of all loads are varied concurrently is used to identify a set of weak buses. In the framework, reactive power for all load buses are generated concurrently and independently based on the probability distribution function of load demands at each node. Three IEEE test systems are used to test the framework in Pypower in conjunction with Python programming language. The result shows that weak buses can be identified with the framework. It was observed that the first three set of most critical nodes in a network can be identified within a variation of 1% of reactive power at load nodes in case of ordinary power flow (pf), while the same set of nodes can be identified with at least 5% of variation of reactive power at nodes based on optimal power flow (opf). One area of...
In this paper a scheme for allocating active power loss in the context of smart grid to load node... more In this paper a scheme for allocating active power loss in the context of smart grid to load nodes is presented. A technique that is based on set theoretic principle is used to identify nodes that use certain segments of a network. Once the nodes are identified, active power losses are then allocated in line with active power demands. The scheme was tested on IEEE 39 bus test system in PYPOWER 5.12. In the results obtained, it is evident that the scheme can be used to allocate losses to load nodes in electric power system.
This paper presents a scheme for allocating loss in transmission network to load nodes. A techniq... more This paper presents a scheme for allocating loss in transmission network to load nodes. A technique that uses load-edge set and edge-load set is used to determine load nodes that are using specific segment of transmission network. Losses are subsequently allocated based on the proportion of active power demand at load nodes. A model of IEEE 9 bus test system in PYPOWER 5.12 was used to test the scheme. The result obtained shows that, the scheme can be used as an alternative means of allocating tranmission network losses to load nodes in electric power networks.
The occurrence of Voltage collapse has been considered a frequent phenomenon in the recent time a... more The occurrence of Voltage collapse has been considered a frequent phenomenon in the recent time and has been a growing concern to the power system utility. Thus, the importance of identifying nodes where reactive power compensator can be placed for voltage stability enhancement. This paper proposed a technique based on the network topological structure of the power system. The suggested technique is found by computing the critical mode and the associated eigenvectors of the system. The node, which has the highest contributions to the critical mode identified is computed and considered as the weakest node. Comparative analysis of the suggested approach with the power flow based technique of modal analysis is also done. The results obtained show that suitable node for the placement of reactive power compensators is better identified using the suggested approach as it saves time and does not depend on performing a time consuming power flow solution before the weakest node is identified.
Gridlad-D is an open source simulation software for modeling electric power distribution network.... more Gridlad-D is an open source simulation software for modeling electric power distribution network. The software has about 9 modules, 181 classess and more than 2402 properties. Although the software is versatile, however modeling of a network could be cumbersome when one is faced with definition of properties of network components. In this work a scheme for auto-completion and syntax highlight of keyword, variables and numerical values was developed for Gridlab-D in Emacs. The result shows that there is a substantial improvement in productivity when Gridlab-D is used with the proposed modeling enhancement scheme.
Environment and Water Resource Management / 813: Modelling and Simulation / 814: Power and Energy Systems / 815: Health Informatics, 2014
The present Nigerian 330kV grid system is predominantly known to be unstable, fragile, and ill-co... more The present Nigerian 330kV grid system is predominantly known to be unstable, fragile, and ill-conditioned. This is due to rapid increase in the consumers demand for electricity and other technical factors. A network is said to be weak and ill-conditioned when it is deficit of reactive power, with low voltages below the nominal limit and has high R/X line ratios. To maintain a secure, efficient and economical operation of electrical power system and to meet the enormous demand by consumers, it becomes imperative to carry out real power flow control and its redirection. Presented in this paper is the application of phase shifting transformers to the Nigerian 330kV grid system for active power flow control. Newton Raphson Iterative algorithm was adopted for solving the power flow problems. Modified power flow algorithm was implemented by the application of phase shifter approach using Phase Shifting Transformers (PST). The phase shifting transformer was inserted one at a time on each of the four suitable transmission lines directly connected to the generator bus. These lines are between Benin to Osogbo (8-10), Alaoji to Onitsha (12-14), Benin to Onitsha (8-14), and Osogbo to Ikeja West (10-5). Results obtained show that, with the incorporation of PST, active power flow can be redirected between the two points in power system and hence, enhancing its operation in terms of efficiency and reduced system losses.
2010 International Conference on Advances in Energy Engineering, 2010
Large cascade blackouts are generally catastrophic both economically and socially, when they occu... more Large cascade blackouts are generally catastrophic both economically and socially, when they occur. In this work, a transmission constrained, 5-bus power grid was simulated using PowerWorld and the impact of lines outages on the violation of loading capacities of network links was studied. We use the Widest Path Algorithm(WPA) and Power Flow Redistribution Algorithm(PFRA) to redistribute power flow in the
Abstract This paper proposes a novel transmission line fault detection and classification scheme,... more Abstract This paper proposes a novel transmission line fault detection and classification scheme, based on a single-end measurements using time shift invariant property of a sinusoidal waveform. Various types of faults at different locations, fault resistance and fault ...
Abstract This paper presents a novel scheme for removing a decay-ing DC-offset from fault current... more Abstract This paper presents a novel scheme for removing a decay-ing DC-offset from fault current measurements in a faulted power transmission lines. The technique is based on Stationary Wavelet Transform (SWT). The performance of the scheme on two study cases ...
This paper presents a novel scheme for removing a decaying DC-offset from both current and voltag... more This paper presents a novel scheme for removing a decaying DC-offset from both current and voltage measurements irrespective of the time constant.The technique is based on stationary wavelet transform (SWT) cascaded with a differentiator. The performance of the scheme on two study cases is investigated; the statistical performance in relation to noise on a hypothetical signal, and a modeled segment of a utility network in South Africa. The proposed scheme is practically applied by testing it on a real life data obtained from Eskom's network. The result shows that the scheme is robust, and that it can remove any DC-offset. The output of the scheme can be used for fault detection, classification and location.
This paper proposes a novel transmission line fault location scheme, combining stationary wavelet... more This paper proposes a novel transmission line fault location scheme, combining stationary wavelet transform (SWT), determinant function feature (DFF), support vector machine (SVM) and support vector regression (SVR). Various types of faults at different locations, fault impedance and fault inception angles on a 400 kV, 361.297 km transmission line are investigated. The system only utilizes single-end measurements. DFF is used to extract distinctive fault features from 1/4 cycle of post fault signals after noise and the decaying DC offset have been eliminated by a filtering scheme based on SWT. A classifier (SVM) and regression (SVR) schemes are subsequently trained with features obtained from DFF. The scheme is then used in precise location of fault on the transmission line. The result shows that fault location on transmission lines can be determined rapidly and correctly irrespective of fault impedance.
... They have been shown to be an attractive and more systematic approach to learn linear or non-... more ... They have been shown to be an attractive and more systematic approach to learn linear or non-linear decision boundaries. SVR includes linear SVR and nonlinear SVR. In this paper, nonlinear SVR is used for estimating fault locations. ...
Environment and Water Resource Management / 813: Modelling and Simulation / 814: Power and Energy Systems / 815: Health Informatics, 2014
Many utilities suffer from High Technical and Non-Technical Energy Losses that, when combined, ca... more Many utilities suffer from High Technical and Non-Technical Energy Losses that, when combined, can exceed 30% of the total energy generated or imported. Studies have shown that the optimal total power losses in the distribution network (Primary and Secondary Distributions) range from between 6% and 12%. Sample studies of a number of utilities showed, however, that the secondary distribution network alone could have a loss that exceeds 12%. In this paper High Voltage Distribution System (HVDS) is proposed for analysis and implementation for Power Holding Company of Nigeria (PHCN) that is having relatively high technical loss problems in a section of the distribution network. The distribution of power at high voltage and supplying the customers directly through small size distribution transformers would be achieved. The load Flow equation for testing a practical situation is also presented.
The plan to integrate solar energy into the Nigerian grid is in conception and thirteen different... more The plan to integrate solar energy into the Nigerian grid is in conception and thirteen different locations within the country have been proposed for solar farm investment. In this paper, fourteen selected solar photovoltaic module types from different manufacturers were assessed to determine the optimum PV module for each of the locations. The optimum module was thereafter used to determine the technical feasibility and economic viability of the locations identified for solar investment in Nigeria. Technical assessments were performed using the reference yield, array yield, final system yield, performance ratio and capacity factor while the economic consideration was made using the levelized cost of energy and payback period. Sensitivity analyses were also carried out to identify the important relationships among the technical and economic parameters as they affect the proposed sites. Relevant findings reveal that final yield, performance ratio and capacity factor ranges between 4.0361 and 4.7972 kWh/kWp, 78.96-79.96% and 16.75-19.92%, respectively. It was also observed that the cost of energy and payback period are between 0.0524 and 0.0607 $/kWh and 10.18-10.42 years, respectively. The sensitivity analyses conducted across the selected sites demonstrate that levelized cost of electricity depends heavily on the electricity production in kWh/kWp. The result obtained also shows that increase in the installed capacity of the solar farm has no significant impact on its performance ratio and capacity factor of the farm. Out of fourteen solar modules that were used in the study, module index M 2 (Panasonic solar) provided the best result in terms of peak values of capacity factor and performance ratio at all the proposed sites.
The quasi-impedance source inverters/quasi-Z source inverters (Q-ZSIs) have shown improvement to ... more The quasi-impedance source inverters/quasi-Z source inverters (Q-ZSIs) have shown improvement to overwhelmed shortcomings of regular voltage-source inverters (VSIs) and current-source inverters (CSIs) in terms of efficiency and buck-boost type operations. The Q-ZSIs encapsulated several significant merits against conventional ZSIs, i.e., realized buck/boost, inversion and power conditioning in a single power stage with improved reliability. The conventional inverters have two major problems; voltage harmonics and boosting capability, which make it impossible to prefer for renewable generation and general-purpose applications such as drive acceleration. This work has proposed a Q-ZSI with five-level six switches coupled inverter. The proposed Q-ZSI has the merits of operation, reduced passive components, higher voltage boosting capability and high efficiency. The modified space vector pulse width modulation (PWM) developed to achieve the desired control on the impedance network and i...
Environment and Water Resource Management / 813: Modelling and Simulation / 814: Power and Energy Systems / 815: Health Informatics, 2014
This paper explores the use of reactive Power compensation to enhance voltage bus profiles for po... more This paper explores the use of reactive Power compensation to enhance voltage bus profiles for power system security in weak power system networks. Powerflow analysis is one of the tools used in this paper and it is modelled as a nonlinear problem which is solved using Newton-Raphson-based algorithm. Power-flow is performed in this paper to determine voltage magnitudes and angles at every bus, active and reactive powers, transmission losses for each of the branches in the network and total transmission losses of the network. Buses that have their voltage magnitude outside the prescribed acceptable limits (% 10  tolerance value) within the network are therefore identified. The magnitudes of the voltages at these buses are substantially improved when reactive power is injected. Total transmission loss on the line is also reduced to barest minimum after the compensation. MATLAB 2010a is used as a programming tool for this work. A weak meshed network of 28-bus system is used as a test system. The result of the simulation in this paper shows the effectiveness of reactive power compensation using a bank of capacitors in transmission power system networks.
Voltage stability assessment in power system has recently been a growing concern to power system ... more Voltage stability assessment in power system has recently been a growing concern to power system utilities due to blackout experienced in a couple of years in some developed and underdeveloped nations. This paper presents an alternative method which is based on the topology of the power network to identify weak load buses that are susceptible to voltage instability. The method makes use of the critical mode and the eigenvectors to determine the weak bus of the system. To determine the critical mode of the system, eigenvalue decomposition technique is used. Comparison analysis with the power flow based voltage collapse proximity index (VCPI) is performed to show the significance of the suggested approach. Results obtained show that voltage stability assessment in power system could as well be done using the structurally based approach as it saves time and reduces the computational burden compared with the traditional power flow based approach of VCPI.
Identification of weak buses in an electric power system is important for operational and plannin... more Identification of weak buses in an electric power system is important for operational and planning purposes. In this paper, a framework that uses the variance of the magnitude of voltage at load buses when reactive power of all loads are varied concurrently is used to identify a set of weak buses. In the framework, reactive power for all load buses are generated concurrently and independently based on the probability distribution function of load demands at each node. Three IEEE test systems are used to test the framework in Pypower in conjunction with Python programming language. The result shows that weak buses can be identified with the framework. It was observed that the first three set of most critical nodes in a network can be identified within a variation of 1% of reactive power at load nodes in case of ordinary power flow (pf), while the same set of nodes can be identified with at least 5% of variation of reactive power at nodes based on optimal power flow (opf). One area of...
In this paper a scheme for allocating active power loss in the context of smart grid to load node... more In this paper a scheme for allocating active power loss in the context of smart grid to load nodes is presented. A technique that is based on set theoretic principle is used to identify nodes that use certain segments of a network. Once the nodes are identified, active power losses are then allocated in line with active power demands. The scheme was tested on IEEE 39 bus test system in PYPOWER 5.12. In the results obtained, it is evident that the scheme can be used to allocate losses to load nodes in electric power system.
This paper presents a scheme for allocating loss in transmission network to load nodes. A techniq... more This paper presents a scheme for allocating loss in transmission network to load nodes. A technique that uses load-edge set and edge-load set is used to determine load nodes that are using specific segment of transmission network. Losses are subsequently allocated based on the proportion of active power demand at load nodes. A model of IEEE 9 bus test system in PYPOWER 5.12 was used to test the scheme. The result obtained shows that, the scheme can be used as an alternative means of allocating tranmission network losses to load nodes in electric power networks.
The occurrence of Voltage collapse has been considered a frequent phenomenon in the recent time a... more The occurrence of Voltage collapse has been considered a frequent phenomenon in the recent time and has been a growing concern to the power system utility. Thus, the importance of identifying nodes where reactive power compensator can be placed for voltage stability enhancement. This paper proposed a technique based on the network topological structure of the power system. The suggested technique is found by computing the critical mode and the associated eigenvectors of the system. The node, which has the highest contributions to the critical mode identified is computed and considered as the weakest node. Comparative analysis of the suggested approach with the power flow based technique of modal analysis is also done. The results obtained show that suitable node for the placement of reactive power compensators is better identified using the suggested approach as it saves time and does not depend on performing a time consuming power flow solution before the weakest node is identified.
Gridlad-D is an open source simulation software for modeling electric power distribution network.... more Gridlad-D is an open source simulation software for modeling electric power distribution network. The software has about 9 modules, 181 classess and more than 2402 properties. Although the software is versatile, however modeling of a network could be cumbersome when one is faced with definition of properties of network components. In this work a scheme for auto-completion and syntax highlight of keyword, variables and numerical values was developed for Gridlab-D in Emacs. The result shows that there is a substantial improvement in productivity when Gridlab-D is used with the proposed modeling enhancement scheme.
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