Murat Dilek - Academia.edu (original) (raw)

Papers by Murat Dilek

2019 IEEE Power & Energy Society General Meeting (PESGM)

A new approach to system computations, Graph Trace Analysis (GTA), is applied to the power flow p... more A new approach to system computations, Graph Trace Analysis (GTA), is applied to the power flow problem. A matrix free GTA power flow algorithm that solves unbalanced, three-phase transmission, substations, and multi-phase distribution, all in the same model, is presented. GTA traces are used to combine both Gauss-Seidel (GS) and continuation methods into a GTA algorithm. Testing circuits are used to demonstrate the capability of the new GTA power flow, and solutions are compared and/or verified against Newton-Raphson and forward/backward sweep based power flow algorithms. The comparisons include convergence characteristics for steady-state voltage stability analysis. It is shown that the computational complexity of GS-GTA grows linearly with the size of the model.

2017 North American Power Symposium (NAPS)

2020 IEEE Power & Energy Society General Meeting (PESGM)

This paper furthers the concept of static stability limit breakdown margin for circuit elements a... more This paper furthers the concept of static stability limit breakdown margin for circuit elements and steady state voltage stability of unbalanced, multiphase integrated Transmission and Distribution (T&D) systems. For large multiphase system with multiple voltage levels, identification of weak links in the system and their reinforcement is demonstrated. As proposed previously, the reinforcement may come in the form of impedance modification, line addition or reactive compensation. Here, utilizing the impedance changing capability of distributed series reactors (DSRs), a control scheme is proposed for dynamic manipulation of voltage stability limits of system buses. This manipulation of stability margin enables flexible operation of the system, where the voltage stability limits of system buses can be changed to increase the net load capability of the buses in events of system contingencies and/or load/generation fluctuations. The proposed concepts are implemented using a robust power flow based on Graph Trace Analysis (GTA). Case studies demonstrate the effectiveness of the methods using an integrated T&D model formed from IEEE standard transmission and distribution models.

2015 IEEE IAS Joint Industrial and Commercial Power Systems / Petroleum and Chemical Industry Conference (ICPSPCIC), 2015

In this paper a new approach for studying slow transients, such as electromechanical transients, ... more In this paper a new approach for studying slow transients, such as electromechanical transients, using three phase models of power systems is presented. Typically programs used for studying slow transients assume a positive sequence network model, limiting their application to the study of balanced power systems. While electromagnetic simulation software can be used for studying slow transients in unbalanced networks, their application to large systems can be resource and time intensive. The approach presented here overcomes the aforementioned limitations of existing software and provides a means for studying slow transients using complete three phase models of the electric network. Of the many potential applications of the approach presented, evaluating the impact of Distributed Generation (DG), such as rooftop solar photovoltaic (PV) based DG, on the stability of the electric grid is important particularly for utilities with high penetration of DG.

2001 IEEE/PES Transmission and Distribution Conference and Exposition. Developing New Perspectives (Cat. No.01CH37294)

Interdependencies among software components for distribution network reconfiguration, reliability... more Interdependencies among software components for distribution network reconfiguration, reliability and protection system analysis are considered. Software interface specifications are presented. Required functionalities of reconfiguration for restoration are detailed. Two algorithms for reconfiguration for restoration are reviewed and compared. Use of outage analysis data to locate circuit sections in need of reliability improvements and to track predicted improvements in reliability is

2003 IEEE PES Transmission and Distribution Conference and Exposition (IEEE Cat. No.03CH37495)

Distribution system circuit topologies, conuections, and equipment pose interesting challenges to... more Distribution system circuit topologies, conuections, and equipment pose interesting challenges to system analysts. An approach based upon fundamental cireuit analysis principles to calculating fault currents of various types is presented. The basic approach consists of obtaining the pre-fault phase voltages and a phase Thevenin matrix at the fault location, and using the phase Thevenin matrix to solve the equations imposed by the boundary conditions of a given fault. The approach requests semces from a multi-phase power flow software component and a circuit model software component. The approach works for both radial aid looped distribution systems. The analysis can evaluate fault currents at a node regardless of whether it is three-phase or nonthree-phase and gmunded or ungrounded. Experience obtained from solving circuits with more than 5000 nodes will be renewed.

2017 North American Power Symposium (NAPS), 2017

Due to the insignificant share of inverter-based Renewable Energy Resources (RER) as well as the ... more Due to the insignificant share of inverter-based Renewable Energy Resources (RER) as well as the uncertainty concerning their integration impacts, the capability of RERs to regulate voltage or frequency has not been widely used. However, inverter-based voltage/frequency regulation is of interest due to the fast growth of distributed RERs, especially solar Photovoltaic (PV) resources. The IEEE 1547a standard relaxed some of the restrictions on utilization of Distributed Energy Resources (DER) in voltage/frequency regulation. Smart inverters may employ different control strategies, such as Fixed Power Factor, Volt-VAR, Volt-Watt, and Frequency-Watt. In this study, a comparison between fixed power factor and Volt-VAR control strategies is performed in terms of voltage regulation capability. One hour of quasi-steady-state simulation with one-second time steps is performed, where fast and frequent irradiance variations are occurring. Parametric studies involving controller settings are used to compare voltage regulation performance. The IEEE 13-bus test feeder, modified by adding two PV generators, is used as the case study. Simulation results show that the Volt-VAR control out performs the fixed power factor control when it comes to voltage regulation.

2020 IEEE/PES Transmission and Distribution Conference and Exposition (T&D), 2020

This paper introduces the concept of static stability limit breakdown margin for circuit elements... more This paper introduces the concept of static stability limit breakdown margin for circuit elements and demonstrates that it is linked with steady state voltage stability of unbalanced, multiphase T&D systems. It is shown that the proposed index can be effectively utilized to recognize and reinforce the system elements that limit the voltage stability. The reinforcement may come in the form of adding a new line, impedance modification or reactive compensation. Thus by changing stability margin, the voltage stability limits of system buses can be manipulated to increase the net load capability of the buses in events of system contingencies and/or load/generation fluctuations. The proposed concepts are implemented using Graph Trace Analysis (GTA), and demonstrated using standard IEEE Transmission, Distribution, and Integrated Transmission and Distribution models built from standard IEEE models.

IEEE PES Power Systems Conference and Exposition, 2004.

Abstract-- Distribution system circuit topologies, connections, and equipment pose interesting ch... more Abstract-- Distribution system circuit topologies, connections, and equipment pose interesting challenges to system analysts. An approach based upon fundamental circuit analysis principles to calculating fault currents of various types is presented. The basic approach consists of ...

International Journal of Renewable Energy Research, 2020

Efforts are exerted worldwide to increase the deployment of renewables specifically solar photovo... more Efforts are exerted worldwide to increase the deployment of renewables specifically solar photovoltaic (PV) systems. One main challenge to face is the perturbation due to the fluctuating nature of the solar energy. The intermittency of the irradiance received by the solar PV systems is mainly caused by the cloud covering the PV system. In this paper a statistical analysis of the received irradiance by a real PV plant as well as the meteorological conditions/parameters surrounding the PV arrays is performed. The meteorological data analyzed include the speed of the cloud, gust, number of clouds passing, width of the clouds, and the time interval between consecutive clouds. One objective of this study is to indicate and adjust the parameters that are to be fed to a Cloud Motion Simulator (CMS); which is a software that simulates the repeated passage of clouds over an electric power system model which includes interconnected PV.

2017 IEEE Power and Energy Conference at Illinois (PECI), 2017

Renewable Energy Resources (RER), especially wind and solar energy resources, have been growing s... more Renewable Energy Resources (RER), especially wind and solar energy resources, have been growing steadily, and supplying all electric power needs from renewable resources appears more achievable than ever. Solar energy has had the greatest growth rate among renewable energy resources in recent years. The main challenge of employing Photovoltaic (PV) systems is the intermittent nature of solar energy. The irradiance variations are mainly caused by cloud movements and the associated shadows moving over solar arrays. Thus, when considering high PV penetration, simulation of cloud shadow movement and its effect on the power system is of interest. In this work a Cloud Motion Simulator (CMS) that incorporates Quasi-Steady-State (QSS) power flow analysis is introduced. Moreover, short-term flicker severity based on the IEEE 1453–2015 standard is computed by the CMS, and the use of this standard is discussed. The effect of CMS parameters — cloud speed, number of clouds, width of clouds, and time interval between clouds — on short-term flicker is also investigated.

Energies, 2020

The use of a Graph Trace Analysis (GTA)-based power flow for analyzing the voltage stability of i... more The use of a Graph Trace Analysis (GTA)-based power flow for analyzing the voltage stability of integrated Transmission and Distribution (T&D) networks is discussed in the context of distributed Photovoltaic (PV) generation. The voltage stability of lines and the load carrying capability of buses is analyzed at various PV penetration levels. It is shown that as the PV generation levels increase, an increase in the steady state voltage stability of the system is observed. Moreover, within certain regions of stability margin changes, changes in voltage stability margins of transmission lines are shown to be linearly related to changes in the loading of the lines. Two case studies are presented, where one case study involves a model with eight voltage levels and 784,000 nodes. In one case study, a voltage-stability heat map is used to demonstrate the identification of weak lines and buses.

Journal of Energy Engineering, 2018

AbstractIntegrated transmission and distribution (T&D) analysis is a new research area in pow... more AbstractIntegrated transmission and distribution (T&D) analysis is a new research area in power systems that has gained traction in recent years to study the impacts of rapidly growing penetration ...

IEEE Transactions on Industry Applications, 2018

Photovoltaic (PV) resources have introduced themselves as a main player in impacting different as... more Photovoltaic (PV) resources have introduced themselves as a main player in impacting different aspects of the power system, from system planning to voltage stability. The main challenge of employing PV systems is the intermittent nature of solar energy. The irradiance variations are mainly caused by cloud motion and the associated shadows moving over solar arrays. Thus, when dealing with high PV penetration levels, simulation of cloud shadow motion and its effect on the power system is of interest. In this work, a Cloud Motion Simulator (CMS) that incorporates Quasi Steady State (QSS) power-flow analysis is introduced. Moreover, how the CMS parameters can be estimated from field data is discussed. Cloud motion and the consequent voltage fluctuations can cause voltage flicker issues. A new and practical method for calculating short-term flicker severity based on the IEEE 1453-2015 standard is introduced and discussed. Effects of cloud speed, number of clouds, width of clouds, and time interval between clouds on short-term flicker are investigated. In addition, the effect of using distributed models for larger PV systems on flicker severity is investigated.

Electric Power Systems Research, 2017

An important issue in today's power system is the need to analyze and determine the adequacy of t... more An important issue in today's power system is the need to analyze and determine the adequacy of transmission capacity. There is a need for approaches to increase transmission system capacity without construction of new transmission facilities, all while assuring secure operation of the grid. Distributed Series Reactors (DSRs) are a new smart grid technology that can be applied to control flows in transmission or distribution systems. DSRs can be used to balance phase flows in a single line as well as to control the distribution of flow in a meshed system. This paper investigates DSRs to control power flow to alleviate overloads due to increased power transfer. The IEEE 39 bus standard model is modified to a 3-phase unbalanced transmission model with 345 kV lines that accounts for tower geometry. Using the symmetrical components transformation, a balanced, 3-phase model is then derived from the unbalanced, 3-phase model. DSR designs based on the unbalanced, 3-phase model and the balanced, 3-phase model are compared and used to demonstrate the effectiveness of DSR control in handling load growth. Only unbalanced impedances are addressed i.e., non-transposed lines, but the effects of impedance unbalance are shown to be significant on the resulting DSR design.

2016 IEEE Rural Electric Power Conference (REPC), 2016

The number of grid-connected rooftop solar photovoltaic (PV) systems is expected to increase sign... more The number of grid-connected rooftop solar photovoltaic (PV) systems is expected to increase significantly in the next few years. Many studies have been conducted on analyzing transmission level voltage stability with high PV penetration, and recent efforts have also analyzed voltage stability at the medium- and low-voltage distribution levels. However, those studies have not considered detailed distribution secondary modeling extending from the primary feeder to the service transformer and all the way through the distribution secondary connections and service drops. This study investigates how variable rooftop solar PV generation impacts voltages at customers sharing a service transformer. Several different types of secondary system topologies are taken into account. A set of rules is presented that can be used to ascertain the level of voltage volatility expected as the solar PV generation varies.

Electric Power Systems Research, 2017

Abstract This paper presents an alternative approach to power system computations, Graph Trace An... more Abstract This paper presents an alternative approach to power system computations, Graph Trace Analysis (GTA), and applies this approach to solving the power flow problem. GTA is derived from the Generic Programming Paradigm of computer science, and uses topology iterators to move through components in a model and perform calculations. The implementation of KVL and KCL in GTA is described. The GTA based power flow algorithm is shown to solve IEEE standard transmission models, IEEE standard distribution models, and integrated transmission and distribution models (hybrid models) constructed from modifying IEEE standard models. Comparisons with widely used, primarily matrix based, power flow algorithms are provided. Two advantages that GTA brings are the separation of system equations from component equations and the ability to distribute calculations across processors.

2016 IEEE Power and Energy Society General Meeting (PESGM), 2016

The primary objective of this paper is to highlight the need for and benefits of studying the ste... more The primary objective of this paper is to highlight the need for and benefits of studying the steady state and dynamic response of power systems using three phase integrated transmission and distribution (T&D) system models (hereafter referred to as hybrid models). Modeling and simulation requirements for building and analyzing hybrid models are also discussed. Finally, results from steady state and dynamic simulations of a large hybrid model are presented to demonstrate insights that can be obtained from hybrid models which cannot be obtained from the study of transmission and distribution systems separately.

Electric Power Systems Research, 2016

The need for modern electricity infrastructures and more capable grid components brings attention... more The need for modern electricity infrastructures and more capable grid components brings attention to Distributed Series Reactor (DSR) technology because of its control capabilities. DSRs are a new smart grid technology that can be applied to control flows in transmission or distribution systems. Design of DSRs to control power flow over transmission lines to alleviate overloads due to load growth under single line contingencies is investigated in this paper. N-1 contingency analysis is performed to assure secure operation of the grid while controlling the active power flow. The IEEE 39 bus standard model is modified to a 3-phase, unbalanced transmission model with 345 kV lines that accounts for tower geometry. The design of DSRs to control power flow under N-1 line contingency is performed using this modified 3-phase, unbalanced model. DSR design to control the power flow of a real power system over tie lines connecting different power pool areas and to control the power flow over transmission lines within the area itself is investigated. The economics of DSRs are then evaluated by comparing the DSR design with a design that uses new line construction.

Electric Power Components and Systems, 2016

A series of analyses along with field validations that evaluate efficiency, reliability, and capa... more A series of analyses along with field validations that evaluate efficiency, reliability, and capacity improvements of modelcentric distribution automation are presented. With model-centric distribution automation, the same model is used from design to real-time control calculations. A 14-feeder system with 7 substations is considered. The analyses involve hourly time-varying loads and annual load growth factors. Phase balancing and capacitor redesign modifications are used to better prepare the system for distribution automation, where the designs are performed considering time-varying loads. Coordinated control of load tap changing transformers, line regulators, and switched capacitor banks is considered. In evaluating distribution automation versus traditional system design and operation, quasi-steady-state power flow analysis is used. In evaluating distribution automation performance for substation transformer failures, reconfiguration for restoration analysis is performed. In evaluating distribution automation for storm conditions, Monte Carlo simulations coupled with reconfiguration for restoration calculations are used. The evaluations demonstrate that model-centric distribution automation has positive effects on system efficiency, capacity, and reliability.

2019 IEEE Power & Energy Society General Meeting (PESGM)

A new approach to system computations, Graph Trace Analysis (GTA), is applied to the power flow p... more A new approach to system computations, Graph Trace Analysis (GTA), is applied to the power flow problem. A matrix free GTA power flow algorithm that solves unbalanced, three-phase transmission, substations, and multi-phase distribution, all in the same model, is presented. GTA traces are used to combine both Gauss-Seidel (GS) and continuation methods into a GTA algorithm. Testing circuits are used to demonstrate the capability of the new GTA power flow, and solutions are compared and/or verified against Newton-Raphson and forward/backward sweep based power flow algorithms. The comparisons include convergence characteristics for steady-state voltage stability analysis. It is shown that the computational complexity of GS-GTA grows linearly with the size of the model.

2017 North American Power Symposium (NAPS)

2020 IEEE Power & Energy Society General Meeting (PESGM)

This paper furthers the concept of static stability limit breakdown margin for circuit elements a... more This paper furthers the concept of static stability limit breakdown margin for circuit elements and steady state voltage stability of unbalanced, multiphase integrated Transmission and Distribution (T&D) systems. For large multiphase system with multiple voltage levels, identification of weak links in the system and their reinforcement is demonstrated. As proposed previously, the reinforcement may come in the form of impedance modification, line addition or reactive compensation. Here, utilizing the impedance changing capability of distributed series reactors (DSRs), a control scheme is proposed for dynamic manipulation of voltage stability limits of system buses. This manipulation of stability margin enables flexible operation of the system, where the voltage stability limits of system buses can be changed to increase the net load capability of the buses in events of system contingencies and/or load/generation fluctuations. The proposed concepts are implemented using a robust power flow based on Graph Trace Analysis (GTA). Case studies demonstrate the effectiveness of the methods using an integrated T&D model formed from IEEE standard transmission and distribution models.

2015 IEEE IAS Joint Industrial and Commercial Power Systems / Petroleum and Chemical Industry Conference (ICPSPCIC), 2015

In this paper a new approach for studying slow transients, such as electromechanical transients, ... more In this paper a new approach for studying slow transients, such as electromechanical transients, using three phase models of power systems is presented. Typically programs used for studying slow transients assume a positive sequence network model, limiting their application to the study of balanced power systems. While electromagnetic simulation software can be used for studying slow transients in unbalanced networks, their application to large systems can be resource and time intensive. The approach presented here overcomes the aforementioned limitations of existing software and provides a means for studying slow transients using complete three phase models of the electric network. Of the many potential applications of the approach presented, evaluating the impact of Distributed Generation (DG), such as rooftop solar photovoltaic (PV) based DG, on the stability of the electric grid is important particularly for utilities with high penetration of DG.

2001 IEEE/PES Transmission and Distribution Conference and Exposition. Developing New Perspectives (Cat. No.01CH37294)

Interdependencies among software components for distribution network reconfiguration, reliability... more Interdependencies among software components for distribution network reconfiguration, reliability and protection system analysis are considered. Software interface specifications are presented. Required functionalities of reconfiguration for restoration are detailed. Two algorithms for reconfiguration for restoration are reviewed and compared. Use of outage analysis data to locate circuit sections in need of reliability improvements and to track predicted improvements in reliability is

2003 IEEE PES Transmission and Distribution Conference and Exposition (IEEE Cat. No.03CH37495)

Distribution system circuit topologies, conuections, and equipment pose interesting challenges to... more Distribution system circuit topologies, conuections, and equipment pose interesting challenges to system analysts. An approach based upon fundamental cireuit analysis principles to calculating fault currents of various types is presented. The basic approach consists of obtaining the pre-fault phase voltages and a phase Thevenin matrix at the fault location, and using the phase Thevenin matrix to solve the equations imposed by the boundary conditions of a given fault. The approach requests semces from a multi-phase power flow software component and a circuit model software component. The approach works for both radial aid looped distribution systems. The analysis can evaluate fault currents at a node regardless of whether it is three-phase or nonthree-phase and gmunded or ungrounded. Experience obtained from solving circuits with more than 5000 nodes will be renewed.

2017 North American Power Symposium (NAPS), 2017

Due to the insignificant share of inverter-based Renewable Energy Resources (RER) as well as the ... more Due to the insignificant share of inverter-based Renewable Energy Resources (RER) as well as the uncertainty concerning their integration impacts, the capability of RERs to regulate voltage or frequency has not been widely used. However, inverter-based voltage/frequency regulation is of interest due to the fast growth of distributed RERs, especially solar Photovoltaic (PV) resources. The IEEE 1547a standard relaxed some of the restrictions on utilization of Distributed Energy Resources (DER) in voltage/frequency regulation. Smart inverters may employ different control strategies, such as Fixed Power Factor, Volt-VAR, Volt-Watt, and Frequency-Watt. In this study, a comparison between fixed power factor and Volt-VAR control strategies is performed in terms of voltage regulation capability. One hour of quasi-steady-state simulation with one-second time steps is performed, where fast and frequent irradiance variations are occurring. Parametric studies involving controller settings are used to compare voltage regulation performance. The IEEE 13-bus test feeder, modified by adding two PV generators, is used as the case study. Simulation results show that the Volt-VAR control out performs the fixed power factor control when it comes to voltage regulation.

2020 IEEE/PES Transmission and Distribution Conference and Exposition (T&D), 2020

This paper introduces the concept of static stability limit breakdown margin for circuit elements... more This paper introduces the concept of static stability limit breakdown margin for circuit elements and demonstrates that it is linked with steady state voltage stability of unbalanced, multiphase T&D systems. It is shown that the proposed index can be effectively utilized to recognize and reinforce the system elements that limit the voltage stability. The reinforcement may come in the form of adding a new line, impedance modification or reactive compensation. Thus by changing stability margin, the voltage stability limits of system buses can be manipulated to increase the net load capability of the buses in events of system contingencies and/or load/generation fluctuations. The proposed concepts are implemented using Graph Trace Analysis (GTA), and demonstrated using standard IEEE Transmission, Distribution, and Integrated Transmission and Distribution models built from standard IEEE models.

IEEE PES Power Systems Conference and Exposition, 2004.

Abstract-- Distribution system circuit topologies, connections, and equipment pose interesting ch... more Abstract-- Distribution system circuit topologies, connections, and equipment pose interesting challenges to system analysts. An approach based upon fundamental circuit analysis principles to calculating fault currents of various types is presented. The basic approach consists of ...

International Journal of Renewable Energy Research, 2020

Efforts are exerted worldwide to increase the deployment of renewables specifically solar photovo... more Efforts are exerted worldwide to increase the deployment of renewables specifically solar photovoltaic (PV) systems. One main challenge to face is the perturbation due to the fluctuating nature of the solar energy. The intermittency of the irradiance received by the solar PV systems is mainly caused by the cloud covering the PV system. In this paper a statistical analysis of the received irradiance by a real PV plant as well as the meteorological conditions/parameters surrounding the PV arrays is performed. The meteorological data analyzed include the speed of the cloud, gust, number of clouds passing, width of the clouds, and the time interval between consecutive clouds. One objective of this study is to indicate and adjust the parameters that are to be fed to a Cloud Motion Simulator (CMS); which is a software that simulates the repeated passage of clouds over an electric power system model which includes interconnected PV.

2017 IEEE Power and Energy Conference at Illinois (PECI), 2017

Renewable Energy Resources (RER), especially wind and solar energy resources, have been growing s... more Renewable Energy Resources (RER), especially wind and solar energy resources, have been growing steadily, and supplying all electric power needs from renewable resources appears more achievable than ever. Solar energy has had the greatest growth rate among renewable energy resources in recent years. The main challenge of employing Photovoltaic (PV) systems is the intermittent nature of solar energy. The irradiance variations are mainly caused by cloud movements and the associated shadows moving over solar arrays. Thus, when considering high PV penetration, simulation of cloud shadow movement and its effect on the power system is of interest. In this work a Cloud Motion Simulator (CMS) that incorporates Quasi-Steady-State (QSS) power flow analysis is introduced. Moreover, short-term flicker severity based on the IEEE 1453–2015 standard is computed by the CMS, and the use of this standard is discussed. The effect of CMS parameters — cloud speed, number of clouds, width of clouds, and time interval between clouds — on short-term flicker is also investigated.

Energies, 2020

The use of a Graph Trace Analysis (GTA)-based power flow for analyzing the voltage stability of i... more The use of a Graph Trace Analysis (GTA)-based power flow for analyzing the voltage stability of integrated Transmission and Distribution (T&D) networks is discussed in the context of distributed Photovoltaic (PV) generation. The voltage stability of lines and the load carrying capability of buses is analyzed at various PV penetration levels. It is shown that as the PV generation levels increase, an increase in the steady state voltage stability of the system is observed. Moreover, within certain regions of stability margin changes, changes in voltage stability margins of transmission lines are shown to be linearly related to changes in the loading of the lines. Two case studies are presented, where one case study involves a model with eight voltage levels and 784,000 nodes. In one case study, a voltage-stability heat map is used to demonstrate the identification of weak lines and buses.

Journal of Energy Engineering, 2018

AbstractIntegrated transmission and distribution (T&D) analysis is a new research area in pow... more AbstractIntegrated transmission and distribution (T&D) analysis is a new research area in power systems that has gained traction in recent years to study the impacts of rapidly growing penetration ...

IEEE Transactions on Industry Applications, 2018

Photovoltaic (PV) resources have introduced themselves as a main player in impacting different as... more Photovoltaic (PV) resources have introduced themselves as a main player in impacting different aspects of the power system, from system planning to voltage stability. The main challenge of employing PV systems is the intermittent nature of solar energy. The irradiance variations are mainly caused by cloud motion and the associated shadows moving over solar arrays. Thus, when dealing with high PV penetration levels, simulation of cloud shadow motion and its effect on the power system is of interest. In this work, a Cloud Motion Simulator (CMS) that incorporates Quasi Steady State (QSS) power-flow analysis is introduced. Moreover, how the CMS parameters can be estimated from field data is discussed. Cloud motion and the consequent voltage fluctuations can cause voltage flicker issues. A new and practical method for calculating short-term flicker severity based on the IEEE 1453-2015 standard is introduced and discussed. Effects of cloud speed, number of clouds, width of clouds, and time interval between clouds on short-term flicker are investigated. In addition, the effect of using distributed models for larger PV systems on flicker severity is investigated.

Electric Power Systems Research, 2017

An important issue in today's power system is the need to analyze and determine the adequacy of t... more An important issue in today's power system is the need to analyze and determine the adequacy of transmission capacity. There is a need for approaches to increase transmission system capacity without construction of new transmission facilities, all while assuring secure operation of the grid. Distributed Series Reactors (DSRs) are a new smart grid technology that can be applied to control flows in transmission or distribution systems. DSRs can be used to balance phase flows in a single line as well as to control the distribution of flow in a meshed system. This paper investigates DSRs to control power flow to alleviate overloads due to increased power transfer. The IEEE 39 bus standard model is modified to a 3-phase unbalanced transmission model with 345 kV lines that accounts for tower geometry. Using the symmetrical components transformation, a balanced, 3-phase model is then derived from the unbalanced, 3-phase model. DSR designs based on the unbalanced, 3-phase model and the balanced, 3-phase model are compared and used to demonstrate the effectiveness of DSR control in handling load growth. Only unbalanced impedances are addressed i.e., non-transposed lines, but the effects of impedance unbalance are shown to be significant on the resulting DSR design.

2016 IEEE Rural Electric Power Conference (REPC), 2016

The number of grid-connected rooftop solar photovoltaic (PV) systems is expected to increase sign... more The number of grid-connected rooftop solar photovoltaic (PV) systems is expected to increase significantly in the next few years. Many studies have been conducted on analyzing transmission level voltage stability with high PV penetration, and recent efforts have also analyzed voltage stability at the medium- and low-voltage distribution levels. However, those studies have not considered detailed distribution secondary modeling extending from the primary feeder to the service transformer and all the way through the distribution secondary connections and service drops. This study investigates how variable rooftop solar PV generation impacts voltages at customers sharing a service transformer. Several different types of secondary system topologies are taken into account. A set of rules is presented that can be used to ascertain the level of voltage volatility expected as the solar PV generation varies.

Electric Power Systems Research, 2017

Abstract This paper presents an alternative approach to power system computations, Graph Trace An... more Abstract This paper presents an alternative approach to power system computations, Graph Trace Analysis (GTA), and applies this approach to solving the power flow problem. GTA is derived from the Generic Programming Paradigm of computer science, and uses topology iterators to move through components in a model and perform calculations. The implementation of KVL and KCL in GTA is described. The GTA based power flow algorithm is shown to solve IEEE standard transmission models, IEEE standard distribution models, and integrated transmission and distribution models (hybrid models) constructed from modifying IEEE standard models. Comparisons with widely used, primarily matrix based, power flow algorithms are provided. Two advantages that GTA brings are the separation of system equations from component equations and the ability to distribute calculations across processors.

2016 IEEE Power and Energy Society General Meeting (PESGM), 2016

The primary objective of this paper is to highlight the need for and benefits of studying the ste... more The primary objective of this paper is to highlight the need for and benefits of studying the steady state and dynamic response of power systems using three phase integrated transmission and distribution (T&D) system models (hereafter referred to as hybrid models). Modeling and simulation requirements for building and analyzing hybrid models are also discussed. Finally, results from steady state and dynamic simulations of a large hybrid model are presented to demonstrate insights that can be obtained from hybrid models which cannot be obtained from the study of transmission and distribution systems separately.

Electric Power Systems Research, 2016

The need for modern electricity infrastructures and more capable grid components brings attention... more The need for modern electricity infrastructures and more capable grid components brings attention to Distributed Series Reactor (DSR) technology because of its control capabilities. DSRs are a new smart grid technology that can be applied to control flows in transmission or distribution systems. Design of DSRs to control power flow over transmission lines to alleviate overloads due to load growth under single line contingencies is investigated in this paper. N-1 contingency analysis is performed to assure secure operation of the grid while controlling the active power flow. The IEEE 39 bus standard model is modified to a 3-phase, unbalanced transmission model with 345 kV lines that accounts for tower geometry. The design of DSRs to control power flow under N-1 line contingency is performed using this modified 3-phase, unbalanced model. DSR design to control the power flow of a real power system over tie lines connecting different power pool areas and to control the power flow over transmission lines within the area itself is investigated. The economics of DSRs are then evaluated by comparing the DSR design with a design that uses new line construction.

Electric Power Components and Systems, 2016

A series of analyses along with field validations that evaluate efficiency, reliability, and capa... more A series of analyses along with field validations that evaluate efficiency, reliability, and capacity improvements of modelcentric distribution automation are presented. With model-centric distribution automation, the same model is used from design to real-time control calculations. A 14-feeder system with 7 substations is considered. The analyses involve hourly time-varying loads and annual load growth factors. Phase balancing and capacitor redesign modifications are used to better prepare the system for distribution automation, where the designs are performed considering time-varying loads. Coordinated control of load tap changing transformers, line regulators, and switched capacitor banks is considered. In evaluating distribution automation versus traditional system design and operation, quasi-steady-state power flow analysis is used. In evaluating distribution automation performance for substation transformer failures, reconfiguration for restoration analysis is performed. In evaluating distribution automation for storm conditions, Monte Carlo simulations coupled with reconfiguration for restoration calculations are used. The evaluations demonstrate that model-centric distribution automation has positive effects on system efficiency, capacity, and reliability.