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Altagamoa Al Khames, Main centre of town, end of 90th Street
New Cairo
Egypt
Faculty of Engineering & Technology

Walid Atef Hafez Elmetwally Omran

Basic information

Name : Walid Atef Hafez Elmetwally Omran
Title: Associate Professor
Personal Info: Walid Atef Omran Date of Birth: 12/06/1974

Education

Certificate Major University Year
PhD Electrical & Computer Engineering University of Waterloo- Faculty Of Engineering 2010
Masters Department of Electrical Engineering Faculty of Engineering - Ain Shams University 2005
Bachelor Department of Electrical Engineering Faculty of Engineering - Ain Shams University 1998

Researches /Publications

A probabilistic multi-objective approach for FACTS devices allocation with different levels of wind penetration under uncertainties and load correlation - 01/0

Walid Atef Hafez Elmetwally Omran

M. EL-Azab, S. F. Mekhamer

01/08/2020

This study presents a probabilistic multi-objective optimization approach to obtain the optimal locations and sizes of static var compensator (SVC) and thyristor-controlled series capacitor (TCSC) in a power transmission network with large level of wind generation. In this study, the uncertainties of the wind power generation and correlated load demand are considered. The uncertainties are modeled in this work using the points estimation method (PEM). The optimization problem is solved using the Multi-objective particle swarm optimization (MOPSO) algorithm to find the best position and rating of the flexible AC transmission system (FACTS) devices. The objective of the problem is to maximize the system loadability while minimizing the power losses and FACTS devices installation cost. Additionally, a technique based on fuzzy decision-making approach is employed to extract one of the Pareto optimal solutions as the best compromise one. The proposed approach is applied on the modified IEEE 30-bus system. The numerical results evince the effectiveness of the proposed approach and shows the economic benefits that can be achieved when considering the FACTS controller.

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Wind Power Ramps Analysis for High Shares of Variable Renewable Generation in Power Systems - 01/0

Walid Atef Hafez Elmetwally Omran

Mohammed Saber, Abdel Moteleb, M Said, M Saber Eltohamy, S Fouad Mekhemar

01/06/2020

The increased penetrations from variable renewable generation (VRG), such as solar and wind, into power systems, growing the flexibility requirements for managing the uncertainty and variability of output power. These flexibility requirements can be achieved by many flexibility options. However, quantifying the flexibility available and required in a power system is a complicated problem. The paper reviews different flexibility metrics that measure the flexibility available from each conventional generator and that measure the flexibility available and needed by a power system at either planning and operational stages. Due to the dynamics of power systems, no flexibility metric has been taken as a standard. Accordingly, for high variable renewable generation shares, it is necessary to have a deeper understanding of power ramping scale as well as times when collective ramp events are most likely to occur. The paper introduces a method for power ramping analysis that will be demonstrated by analysing the output power of aggregated Belgian wind farms. In addition, the ramp characteristic indicators have been proposed for comparing the ramping behaviour of VRG in different years or between different countries.

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Optimal Battery Sizing in Wind System Using Firefly and Harmony Search Techniques - 01/1

Walid Atef Hafez Elmetwally Omran

Ibrahim M Ibrahim, SF Mekhamer

01/12/2019

This paper investigates the use of the battery storage to solve the power fluctuations problem of a grid connected wind energy system. The main objective of the study is to obtain the optimal size of the battery which reduces the wind power fluctuations to be within acceptable limits and maximizes the profit gained from selling the energy to the grid. The formulated optimization problem is solved using two optimization techniques; the Firefly Algorithm and the Harmony Search Algorithm which have not been used in the previous studies related to the wind power fluctuations problem presented in this paper. The problem codes are implemented using MATLAB program.

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Analyzing Wind Power Ramps for High Penetration of Variable Renewable Generation - 01/1

Walid Atef Hafez Elmetwally Omran

M Saber Eltohamy, M Said Abdel Moteleb, S Fouad Mekhemer

01/12/2019

One of the greatest issues connected with incorporating high penetration levels of variable renewable generation into the power system is the capability to handle the unlimited ramps in the renewable power production. It is essential for power system operators to have statistical information on the power ramping features of renewables generation. This information can be utilized in power system operations to mitigate ramping events for the sake of power system flexibility, reliability and economic considerations. Grid operators had successfully balanced the variability of collective power output at low penetration of variable renewable generation, but as the installations of renewable energy continue to grow, the ability to manage these fluctuations has become a difficult task. At high renewable penetration, more power ramps with short durations occurred as the number of ramping events increased with increasing penetration level [1]. In this paper the output power of wind generation will be analyzed to get information about the wind power ramping behavior by analyzing the historical data of power-time curve in two directions, vertical and horizontal. While the forecast of wind power has been improved, the forecast errors are still relatively high. As a result, with the increase in the participation rate of variable generation, these errors will significantly affect the balance of generating capacity and consumption. Consequently, from the perspective of grid operators, it will be necessary to gain a deeper understanding of the aggregate ramping scale and the periods that collective ramp events are most likely to occur. The analyzing method will be demonstrated by analyzing the output power of aggregated Belgium's wind farms, 3.16 GW, in the year of 2018.

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Overview of Power System Flexibility Options with Increasing Variable Renewable Generations - 01/1

Walid Atef Hafez Elmetwally Omran

aber Eltohamy, M Said Abdel Moteleb

01/11/2019

Many energy systems around the world tend to generate electricity from renewable energy sources as an alternative to the use of high-carbon fossil fuels. Increasing the rate of inclusion of renewable power plants in power systems at the expense of conventional power plants will result in new challenges in dealing with the unexpected generation capacity of these plants. This research discusses the various flexibility options for power systems in dealing with this variable and uncertain generating capacity at different time intervals to achieve the desired balance between generating capacity and load needs.

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Technical Investigation for Power System Flexibility - 01/1

Walid Atef Hafez Elmetwally Omran

M Saber Eltohamy, M Said Abdel Moteleb, S Fouad Mekhemer

01/11/2019

Power systems face growing flexibility requirements for managing the increased penetrations from variable renewable generation (VRG) like solar and wind power generation. In general, instant balance of temporal inequalities between supply and demand can be reached by many flexibility options. However, an accurate quantification of the flexibility needed and available in a power system is a complex task. Accordingly, this paper introduces a review of various power system flexibility metrics that used to quantify the flexibility. The use of these metrics varied, some of which were used to measure the flexibility available from each conventional generator and others were used to measure the flexibility available and needed by the power system at both the planning and operational stages, but up till now there is no flexibility metric that can be taken as a standard.

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Hybrid mean variance mapping optimization for dynamic economic dispatch with valve point effects - 01/0

Walid Atef Hafez Elmetwally Omran

Noha Shouman, YG Hegazy, Gerhard Krost

01/05/2018

This paper proposes hybrid variant mean variance mapping optimization technique (MVMO-SH) for solving dynamic economic load dispatch problem (DED) in power systems. MVMO-SH has less number of control parameters to be tuned which makes it easier to solve non-convex problems. The effectiveness of the proposed technique has been verified on four different case studies to solve the DED problem of thermal power units for a cycle of 24 hours. The constraints taken into account are transmission losses, generation limits, ramp rate limits, valve- point loading and spinning reserve constraints. The results obtained by MVMO-SH algorithm have been compared with those of previously published algorithms in terms of solution quality and robustness.

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A Decentralized Technique for Autonomous Service Restoration in Active Radial Distribution Networks - 01/0

Walid Atef Hafez Elmetwally Omran

Ahmed Abel Hafez, Yasser G. Hegazy

01/05/2018

This paper proposes a fully decentralized multi-agent system (MAS) based technique for service restoration of radial distribution networks. The technique utilizes expert system rules and considers the customers' priority and the presence of distributed generators (DGs). It also considers the operational constraints in both healthy and restored sections of the feeder. The technique relies on one type of agents only, hence, simplifying its implementation. Moreover, it allows for assigning a back-up decision making agent to improve the reliability of the restoration process. The effectiveness of the technique is validated through several case studies simulated on an 11 kV distribution feeder. The agents are implemented in Java Agent Developing Framework (JADE) environment for communications and decisions making. Power flow calculations are performed in MATLAB environment to validate the correctness of the agents' decisions.

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Optimal Battery Sizing in Wind System Using Firefly and Harmony Search Techniques - 01/1

Walid Atef Hafez Elmetwally Omran

Ibrahim M. Ibrahim

01/12/2017

This paper investigates the use of the battery storage to solve the power fluctuations problem of a grid connected wind energy system. The main objective of the study is to obtain the optimal size of the battery which reduces the wind power fluctuations to be within acceptable limits and maximizes the profit gained from selling the energy to the grid. The formulated optimization problem is solved using two optimization techniques; the Firefly Algorithm and the Harmony Search Algorithm which have not been used in the previous studies related to the wind power fluctuations problem presented in this paper. The problem codes are implemented using MATLAB program.

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Optimal Reconfiguration and DG Allocation in Active Distribution Networks Using a Probabilistic Approach - 01/0

Walid Atef Hafez Elmetwally Omran

Mina G. Naguib

01/09/2017

This paper proposes a method for the reduction of annual energy loss in distribution networks using simultaneous reconfiguration and allocation of Distributed Generators (DGs). The method considers the DGs intermittency throughout the studied period by using a probabilistic model for renewable based DGs. Hence, the model is used in solving a discrete nonlinear optimization problem to find the optimal sizes and locations of DGs and the optimal configuration of the network. The problem is solved using the discrete Firefly optimization technique and is tested on the IEEE 33-bus system. The test cases are used to investigate the effectiveness of simultaneous reconfiguration and DG allocation as compared to reconfiguration alone, DG allocation alone, and DG allocation after reconfiguration. In addition, the test cases investigate the best scenario for simultaneous reconfiguration and DG allocation based on the season.

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Mean Variance Mapping Optimization for Solving the Economic Load Dispatch Problem - 01/0

Walid Atef Hafez Elmetwally Omran

Noha Shouman ; Y. G. Hegazy ; Gerhard Krost

01/06/2017

The mean variance mapping optimization technique (MVMO) is employed in this paper to solve the economic dispatch problem (ED) in power systems. The effectiveness of the proposed technique has been verified on three different case studies to solve the ED problem of thermal power units taking into account the transmission losses and other constraints which include generation limits, ramp rate limits, prohibited operating zones and valve-point loading. The obtained results have demonstrated that MVMO is a promising approach for solving the optimization problems in practical power systems. Moreover, the number of control parameters in MVMO to be tuned is less than that in most of other metaheuristic technique which makes it simpler for solving non-convex optimization problems. Solution quality, convergence speed and robustness of MVMO technique has been compared with those of formerly proposed techniques.

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Power management strategy to enhance the operation of active distribution networks - 01/0

Walid Atef Hafez Elmetwally Omran

Ahmed A. Raouf Mohamed ; Rania El-Sharkawy

01/04/2017

This paper focuses on the power management of renewable energy based distributed generators (RDGs) installed in medium voltage distribution networks (DNs). The goal of the study is to propose a strategy that improves the operation of the distribution network by utilizing the available resources efficiently. This is achieved by continuously managing the output power from the RDGs to meet the required demand. To achieve this task, the proposed strategy is divided into two stages; short-term planning stage and distribution network operation stage. In the short term planning stage, optimal power flow (OPF) is used to determine the output of the RDGs using forecasted data. The aim of the OPF is to minimize the power loss of the distribution network. The second stage aims to manage the actual output power of the RDGs using a multi-agent system (MAS). This stage is responsible for controlling any power imbalance that occurs between the generation and demand in each zone until the OPF is executed in the next time step. The OPF is performed using Particle Swarm Optimization (PSO) implemented in MATLAB, while the MAS is implemented in the JADE environment.

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A probabilistic approach for the optimal placement of PMUs with limited number of channels - 01/1

Walid Atef Hafez Elmetwally Omran

Ahmed Hamdy Ghazy Ibrahim

01/12/2016

This paper presents a two-stage method for the placement of Phasor Measurement Units (PMUs) to achieve a fully observable power system while considering the PMUs channel limitation. The first stage uses the Binary Integer Linear Programming (BILP) to find the initial optimum locations of PMUs which ensure full system observability under normal conditions. The second stage uses state enumeration based on probabilistic failure of different components to ensure full system observability under single and double outages. The proposed method is validated using the IEEE 14-Bus system, IEEE 30-Bus system and IEEE 57-Bus system. The simulation results show that the method is efficient in providing detailed information about the observability of the power system under different operating conditions.

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Power Management in Islanded Microgrids Using Multi-Agent Systems - 01/1

Walid Atef Hafez Elmetwally Omran

Ahmed M. Abdulmohsen ; Metwally A. El-Sharkawy

01/10/2016

This paper presents a power management strategy for islanded microgrids. The proposed strategy utilizes the MultiAgent System (MAS) to perform the required tasks. The strategy is divided into two stages. The first stage is an operational planning stage which aims to optimize the operation of the microgrid in the islanded mode. This is achieved by performing Optimal Power Flow (OPF) periodically in the grid connected mode using a central agent. Once the islanded mode is detected, the results of the OPF are used to balance the operation of the microgrid. Several distributed agents along with the central agent aim to further fine tune the set points obtained from the OPF based on the actual operating conditions of the microgrid. To demonstrate the effectiveness of the proposed strategy, four scenarios are simulated and presented.

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“A Decentralized Coordination Strategy for Voltage Regulation of Active Distribution Networks - 01/1

Walid Atef Hafez Elmetwally Omran

Mohamed M. Ibrahim

01/10/2016

This paper presents a fully decentralized coordination strategy based on Multi-Agent System (MAS) for voltage regulation in active distribution networks (ADNs). The strategy is based on coordinating the operation of Distributed Generators (DGs) and On-Load Tap Changer (OLTC) to maintain the bus voltages within acceptable limits. The strategy attempts to maximize the use of the renewable based DGs while minimizing the operation of the OLTC. Several case studies are presented to show the effectiveness and robustness of the proposed strategy.

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A Decentralized Technique for Autonomous Service Restoration in Active Radial Distribution Networks - 01/0

Walid Atef Hafez Elmetwally Omran

Ahmed Abel Hafez, Yasser G Higazi

01/08/2016

This paper proposes a fully decentralized multi-agent system (MAS) based technique for service restoration of radial distribution networks. The technique utilizes expert system rules and considers the customers' priority and the presence of distributed generators (DGs). It also considers the operational constraints in both healthy and restored sections of the feeder. The technique relies on one type of agents only, hence, simplifying its implementation. Moreover, it allows for assigning a back-up decision making agent to improve the reliability of the restoration process. The effectiveness of the technique is validated through several case studies simulated on an 11 kV distribution feeder. The agents are implemented in Java Agent Developing Framework (JADE) environment for communications and decisions making. Power flow calculations are performed in MATLAB environment to validate the correctness of the agents' decisions.

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Sizing and control of large PV system inverters connected to MV grid - 01/0

Walid Atef Hafez Elmetwally Omran

Hassan H. Eldeeb and, Mostafa I. Marei

01/04/2016

New energy polices and the reduction in the prices of photovoltaic (PV) panels, storage batteries and power electronics inverters resulted in a dramatic increase in the penetration level of PV systems connected to the medium voltage (MV) network. Consequently, utility sets a restriction over the injected power fluctuations as well as the requirements from PV system to support static and dynamic stability of the grid. The German grid code for connecting generation units to MV network is one of the stringent grid codes regards the stability requirements. Those requirements are required to be fulfilled under techno-economical attentive considerations to maximize the profit of PV system owner. This paper introduces an optimal sizing for battery and its corresponding inverter to satisfy the grid requirements and to maximize the profit. The optimization is done using GAMS software. The system is implemented using a real time simulator PSCAD/EMTDC to study the dynamics of control loops under steady state and transient conditions. Moreover, the German grid-code is utilized for controlling the reactive power injected from system inverters to support the voltage stability. The simulation results reveal accurate, fast and improved dynamic response of the proposed system Index Terms-PV, power fluctuations, optimal sizing, reactive power management, voltage stability, coordinated control.

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Voltage Stability Investigation of the Egyptian Grid with High Penetration Level of Wind Energy During Steady State and Transien - 01/0

Walid Atef Hafez Elmetwally Omran

Hamdy S. K. El-Goharey; Adel T. M. Taha; Salwa M. El-Samanoudy

01/04/2016

The large penetration level of wind farms might have deleterious effects on the voltage stability of the electric network. This is because wind farms absorb reactive power from the transmission network and an observable drop in bus voltages occur. To mitigate this effect, system must be studied under steady-state and transient conditions. The main objective of this study is to analyze the voltage stability of the Egyptian Electrical Network with large scale wind power under normal condition, under single contingency (N-1) and under transient condition. The single contingency is defined as the loss of any transmission line, transformer, or generator. In addition, the paper determines the size of reactive power compensation devices (capacitors or STATCOM) that should be installed at weak buses to prevent the voltage collapse during normal and transient states.

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Power System Observability of Phasor Measurement Units: A Binary Integer Programming Approach - 01/1

Walid Atef Hafez Elmetwally Omran

Ahmed Hamdy Ghazy Ibrahim

01/11/2015

In this paper, the allocation problem of Phasor measurement units (PMU) is solved using a binary integer programming (BIP) method. The proposed approach aims to minimize the total number of PMUs that can achieve full system observability. Defining N as the number of system buses, the full system observability is ensured both in normal operating conditions and in case of N-1 contingencies such as the outage of a PMU or a transmission line. Moreover, the approach is utilized to allocate the PMUs in case of limited number of PMU channels. The problem formulation considers the Zero Injection Buses (ZIBs) and uses a set of rules that can improve the redundancy of the PMUs by choosing better locations without increasing their number. The proposed approach is applied to the IEEE standard systems 14, 30 and 57 test systems. The simulations results are compared with other approaches used in the literature to validate the effective performance of the proposed approach.

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Reliability Assessment of Grid Connected Photovoltaic Generation Systems - 01/1

Walid Atef Hafez Elmetwally Omran

Ahmed M. Mustafa, Yasser G. Hegazy

01/11/2015

This paper investigates the reliability of different topologies of grid connected photovoltaic (PV) systems. The topologies considered in this study are centralized topology, string topology and multi-string topology. The reliability of each topology is evaluated by using suitable reliability indices that are based on calculating the probability of different operating states. These states are evaluated using the state enumeration method which is based on computing the failure rate of each component while considering the different environmental conditions. Simulations are performed in MATLAB environment on a 58.3 KW photovoltaic system to compare between the reliability of the three topologies.

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Enhancing the Power System Observability with the Aid of Phasor Measurement Units - 01/0

Walid Atef Hafez Elmetwally Omran

Ahmed Hamdy Ghazy Ibrahim

01/09/2015

This paper presents an approach for optimally allocating the Phasor Measurement Units (PMUs) in a power system. The proposed approach is based on Binary Integer Programming (BIP) to minimize the total number of PMUs that can achieve full system observability. The full system observability is ensured both in normal operating conditions and in case ofN-1 contingencies such as the outage of a PMU or a transmission line. Moreover, the approach is utilized to allocate the PMUs in case of limited number of PMU channels. The problem formulation considers the Zero Injection Buses (ZIBs) and uses a set of rules that can improve the redundancy of the PMUs by choosing better locations without increasing their number. The proposed approach is applied on the IEEE standard systems 14, 30 and 57 test systems. The simulations results are compared with other approaches used in the literature to validate the performance of the proposed approach.

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Multi-Agent Based Control Scheme for Electrical Distribution System Restoration - 01/0

Walid Atef Hafez Elmetwally Omran

Abdel Hafez and, Yasser G. Hegazy

01/09/2015

Continuity of the electric supply is considered one of the main power quality indices, and thus, it is essential to perform fast and efficient restoration of electricity following outages. However, this might not be always an easy task, especially in large distribution networks. In this paper, an efficient multi-agent based control scheme is introduced to restore the maximum possible out of service loads without violating any of the technical constraints of the electric network. The proposed scheme utilizes a number of agents distributed along the feeder to gather the necessary information and communicate it to the decision making agent at the faulted feeder head. The decision making agent first attempts to restore all the out of service loads through group restoration. However, if this is not possible due to violating any of the technical constrains, then the agent attempts to restore as much loads as possible through a zone restoration process. To validate the effectiveness of the proposed control scheme, two case studies are presented to show the group and zone restorations. The distribution system is simulated in the MATLAB environment to perform the required power flow calculations and provide the necessary information to the agents. On the other hand, the agents are implemented in JADE environment where the communication and decision making process occurs.

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Investigation of methods for reduction of power fluctuations generated from large grid-connected photovoltaic systems - 01/1

Walid Atef Hafez Elmetwally Omran

M Kazerani, MMA Salama

01/12/2010

Photovoltaic (PV) systems are presently allowed to inject into the grid all the power they can generate. However, in the near future, utilities are expected to impose additional regulations and restrictions on the power being injected by large centralized PV systems because of their possible adverse impacts. One of the main issues associated with large PV systems is the fluctuation of their output power. These fluctuations can negatively impact the performance of the electric networks to which these systems are connected, especially if the penetration levels of these systems are high. Moreover, the fluctuations in the power of PV systems make it difficult to predict their output, and thus, to consider them when scheduling the generating units in the network. The main objective of this paper is to investigate some methods that can be used to reduce the fluctuations in the power generated from a large customer-owned PV system, in the order of megawatts. This paper focuses on three methods: 1) the use of battery storage systems; 2) the use of dump loads; and 3) curtailment of the generated power by operating the power-conditioning unit of the PV system below the maximum power point. The emphasis in the analysis presented in this paper is on investigating the impacts of implementing these methods on the economical benefits that the PV system owner gains. To estimate the maximum revenues gained by the system owner, an linear programming optimization problem is formulated and solved. Moreover, the effect of varying different parameters of the problem is investigated through sensitivity analysis.

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A clustering-based method for quantifying the effects of large on-grid PV systems - 01/0

Walid Atef Hafez Elmetwally Omran

Mehrdad Kazerani, Magdy MA Salama

01/08/2010

Analyzing the impacts of large on-grid photovoltaic (PV) systems on the performance of the electric network is an essential task prior to the installation of these systems. To quantify these impacts, a method based on chronological simulations can be used. The main advantage of this method is its ability to provide information about the impacts of the fluctuation of the power generated from the PV systems. However, this method requires performing extensive analysis and simulations, making it impractical for utility studies, especially if long historical data with subhourly time resolution is used. In this paper, a new method that utilizes the data efficiently while preserving the temporal information of the generated PV power is proposed. The method takes advantage of the clustering techniques to group together segments of the output PV power having similar features. Hence, a representative segment for each group can be chosen and used in the analysis and simulations. This representative segment can provide information about the expected performance of other segments of the group. The validity and usefulness of the proposed method are demonstrated by identifying the suitable size and site of a large PV system.

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Identification and measurement of harmonic pollution for radial and nonradial systems - 01/0

Walid Atef Hafez Elmetwally Omran

Hamdy SK El-Goharey, Mehrdad Kazerani, MMA Salama

01/06/2009

Harmonic pollution is considered to be one of the major power-quality problems in electric power systems. Correct identification of the dominant source of harmonic pollution is an essential step towards solving this problem. The total harmonic power (THP) method is one of the methods proposed in the literature for this purpose. However, the method is still debatable as its complete success has been questioned by some researchers. This paper tries to answer some concerns regarding the success of the THP method in radial systems by using several comprehensive case studies. Then, a modification to the method is proposed to generalize its application to nonradial systems. Moreover, to increase the reliability and applicability of the method, a new time-domain algorithm is proposed for measuring the harmonic, subharmonic and interharmonic powers for single-phase and three-phase four-wire systems.

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