Power System Operation Research Papers (original) (raw)

The increasing influence of wind power in the power system operation has caused the power system operators to include wind power plants in the control of the overall power system, both in steady-state and transient operation. Therefore, the grid connection requirements of the power system operators involve wind power systems. Low voltage ride-through requirement is probably the most demanding grid connection requirement to meet, at least from the point of view of the wind energy conversion system. In presence of grid voltage dips, the low voltage ride-through compliance produces a mismatch between the generated active power and the active power delivered to the grid. The management of this mismatch supposes a challenge for the wind energy conversion system. In this work, a control scheme for the back-to-back neutral-pointclamped converter is proposed. Under grid voltage dip, the controllers for generator-side and grid-side converters work concurrently to meet the low voltage ride-through requirement by storing the active power surplus in the inertia of the generator and keeping constant the dc-link voltage. Simulation results verify the proposed control scheme.

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- Power System, Energy Conversion, Wind Power, Wind energy conversion system

Abstract—The determination of additional operating reserves in power systems with high wind penetration is attracting a significant amount of attention and research. Wind integration analysis over the past several years has shown that the... more

- by Michael Milligan and +4
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- Wind Energy, Power System, Electric Power Systems, Wind Power

This paper presents a fast and efficient method which combines the Monte Carlo simulation (MCS) and the least squares support vector machine (LSSVM) classifier, for reliability evaluation of composite power system. LSSVM is used to accurately pre-classify the power system operating states as either success or failure states during the Monte Carlo sampling. These pre-classified failure states are then evaluated for adequacy analysis using DC power flow to calculate reliability indices. As a result, the computing time to perform power flow analysis of the system success states is eliminated. The proposed hybrid method is applied to the IEEE Reliability Test System (IEEE-RTS-79) and simulation results obtained using LSSVM with linear and nonlinear kernels are compared with that of nonsequential MCS. These promising results demonstrate the efficacy of the proposed MCS-LSSVM based hybrid method in terms of both classification accuracy and computational time in evaluating the composite power system reliability.

- by Dipti Srinivasan
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- Monte Carlo Simulation, Power System, Monte Carlo, Support Vector Machines

There are a multitude of studies completed and ongoing related to the cost of wind integration. However, the results are not easy to compare. An international forum for exchange of knowledge of power system impacts of wind power has been formed under the IEA Implementing Agreement on Wind Energy. IEA WIND R&D Task 25 on "Design and Operation of Power Systems with Large Amounts of Wind Power" produced a state-of-the-art report in October 2007, where the most relevant wind-power grid integration studies were analyzed, especially regarding methodologies and input data. This paper summarizes the results from 18 case studies, with discussion on differences in methodology as well as issues that have been identified to impact the cost of wind integration.

- by Hannele Holttinen and +2
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- Mechanical Engineering, Wind Energy, Power System, Wind Power

The paper critically analyzes the state of the art of the procedures to ensure the security of power system operation with respect to the introduction of Interruptible Loads. A short overview of the existing international approaches is presented. The potentiality of load curtailment as an ancillary service is underlined. The benefits for the power system in terms of increased exploitation of the network capability -with particular attention to the increase of Total Transfer Capacity (TTC) across network sectionsare emphasized. A new definition of security is discussed as a consequence of the use of Interruptible Loads not only into emergency conditions but also during normal and alert operation, in order to guarantee the N-1 criterion satisfaction. The consequences of the introduction of Interruptible Loads are detailed and some preliminary hints for the specific situations of the Italian Power System are presented. The results of a research activity on the possibility to use the load curtailment approach to increase the TTC in the Italy-Europe section are reported.

- by Marino Sforna
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- Power System, Power System Security, Power System Operation, Security Assessment

The use of distributed energy resources is increasingly being pursued as a supplement and an alternative to large conventional central power stations. The specification of a powerelectronic interface is subject to requirements related not only to the renewable energy source itself but also to its effects on the power-system operation, especially where the intermittent energy source constitutes a significant part of the total system capacity. In this paper, new trends in power electronics for the integration of wind and photovoltaic (PV) power generators are presented. A review of the appropriate storage-system technology used for the integration of intermittent renewable energy sources is also introduced. Discussions about common and future trends in renewable energy systems based on reliability and maturity of each technology are presented.

- by J. T. Bialasiewicz and +2
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- Engineering, Power Electronics, Renewable Energy, Power System
- by Max Anderson
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- Curriculum Design, Power System, Power System Operation, Network Topology

This paper has been prepared to provide a better understanding of the subject matter and to serve as a guide for those involved in engineering, maintenance, and operation of turbogenerators in a process plant. The paper covers all aspects of a turbogenerator and the system considerations that are required to achieve a reliable power system and minimize power outage during system disturbances. These include the following: 1) generator parameters; 2) excitation system; 3) neutral grounding; 4) protection; 5) synchronizing; 6) integration into the power system; 7) utility interface; and 8) islanding. Additional reference is provided for further investigation and clarification into the subject matter.

- by S. Khan
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- Engineering, Power System, Maintenance Engineering, Power System Operation

Three very different methods of accomplishing the same task-managing the operation of the transmission system in the deregulated power system operating environment-have been implemented as deregulated market structures have been created around the world. They are first, the optimal power flow (OPF) model found in various implementations in the United Kingdom, parts of the United States, and in Australia and New Zealand. Second, the point tariff, price area congestion control model used in the Nordpool market area in Norway and Sweden. Third, the U.S. transaction-based model. All are pragmatic solutions implemented in advance of complete theoretical understanding. Each has strengths and flaws, and there are some surprising inter-relationships. Each maintains power system security but differs in its impact on the economics of the energy market. No clearly superior method has so far emerged. In the future, methods of combining decentralized market solutions with operational use of optimal power flow may provide better solutions to existing and emerging problems.

- by Rajaram Prathiba
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- Biomedical Engineering, Congestion Control, Market Structure, United Kingdom

Ancillary Services are essential to the reliability and security of power system operation in any competitive electricity market environment. Procurement of ancillary services must take into account effective use of the capacity under emergency conditions, delivery time, transmission limitations, and local area requirements. Regional procurement of ancillary services is an approach that results in effective distribution of reserves and ensures continuous reliability in the event of a contingency occurring anywhere in the system. However, most ISOs procure and price ancillary services based on the least-cost service with little regard to zonal dispersion. In general, such an approach is not sufficient to ensure continuous reliability and security of the power system This paper presents a new methodology and numerical examples for procuring and pricing ancillary services on a regional basis, with an explicit representation of imports in a simultaneous energy/reserve market environment.

- by Ziad Alaywan
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- Power System, Power System Economics, Power System Operation, Optimal Power Flow

This paper provides comprehensive development procedures and final forms of mathematical models of unified power flow controller (UPFC) for steadystate, transient stability a$ eigenvalue studies. Based on the developed models, the impacts of control strategy, parameters and location of UPFC on power system operating conditions are discussed. The accuracy of the developed models is verified through comparing the study results with those obtained from detailed time-domain simulation using the Electromagnetic Transients Program (EMTP).

- by Ali Nabavi
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- Power System, Power System Operation, Eigenvalues, Steady state
- by R. Bessa
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- Economics, Power Systems, Environmental policy, Renewable Energy

The global electrical energy consumption is still rising and there is a steady demand to increase the power capacity. The production, distribution and the use of the energy should be as technological efficient as possible and incentives to save energy at the end-user should be set up. The deregulation of energy has lowered the investment in larger power plants, which

- by Florin Iov
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- Power Electronics, Renewable Energy, Wind Energy, Power System

Growing number of wind turbines is changing electricity generation profile all over the world. This brings challenges for power system operation, which was designed and developed around conventional power plants with directly coupled synchronous generators. In result, safety and stability of the electrical network with high wind energy penetration might be compromised. For this reason transmission system operators (TSO) impose more stringent connection requirements on the wind power plant (WPP) owners. On the other hand flexible AC transmission systems (FACTS) devices offer enhancement of grid stability and can facilitate grid code compliance for WPP.

- by P. Rodriguez
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- Wind Energy, Power Plant, Wind Power, Wind turbine

As wind power penetration level increases, power system operators are challenged by the penetration impacts to maintain reliability and stability of power system. Therefore, grid codes are being published and continuously updated by transmission system operators of the countries. In this paper, recent grid codes, which are prepared specially for the large wind power plants, are analyzed and compared. Also, harmonization of different grid codes in a common manner and future trends are assessed.

- by Mufit Altin
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- Wind Energy, Power System, Induction Generators, Wind Power

The use of distributed energy resources (DER) is increasingly being pursued as a supplement and an alternative to large conventional central power stations. The specification of a power electronics interface is subject to requirements related not only to the renewable energy source itself but also to its effects on power system operation, especially where the intermittent energy source constitutes a significant part of the total system capacity. In this paper, new trends in power electronics for the integration of wind and photovoltaic power generators are presented. A review of appropriate storage systems technology used for the integration of intermittent renewable energy sources is also introduced. Discussions about common and future trends in renewable energy systems based on reliability and maturity of each technology are presented.

- by Narciso Moreno
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- Engineering, Power Electronics, Renewable Energy, renewable Energy sources

The installation of small or medium sized dispersed storage and generation units operating in parallel with the utility supply presents several technical complications for the protection and control of the system. Amongst these is the need to protect the system from islanding caused by the loss of the utility grid supply and the possible subsequent out-of-synchronism reconnection of that supply. This paper examines the requirements of an islanding, or 'loss of grid', protection and outlines the principal methods used for this type of relaying. A new protection algorithm is introduced which is based on the rate of change of power as measured at the generator's terminals. The responses of the different measurands are examined for a selection of power system operating conditions to demonstrate the operation of this type of protection.

- by Miles Redfern and +1
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- Power System, Power Generation, Power Transmission, Power System Operation

Due to the increase of the distributed power generation in recent years, power system operators have updated their grid connection requirements, in order to include distributed power generation plants operation in the transient operation control of the overall electric power system. Among them, low voltage ride-through requirements demand wind power plant to remain connected to the network in presence of grid voltage dips, contributing to keep network voltage and frequency stable. Wind power technology points to increase voltage levels. Hence, multilevel converters are well suited for this application. The use of symmetrical components to control grid-connected voltage-source converters is simple and effective, but a sequence separation method is needed, which delivers inexact response during a lapse of time after a fault appearance or clearance. This inaccurate response can be a significant drawback. Predictive current control presents similar dynamic response and reference tracking than other well established control methods, but working at lower switching frequencies. In this work, predictive current control is applied to the grid-side NPC converter, in order to fulfil LVRT requirements. Then, a sequence separation method is not needed and inaccuracies after grid fault appearance and clearance are removed from the system performance. DC-link neutral point balance is also achieved by means of the predictive control algorithm, which considers the redundant switching states of the NPC. Simulation results confirm the validity of the proposed control approach.

- by Patricio Cortes
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- Engineering, Power Systems, Wind Energy, Wind Power

- by Jose Leon
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- Engineering, Power Electronics, Renewable Energy, Power System

This paper presents an optimal allocation method for flexible ac transmission system (FACTS) devices for market-based power systems considering congestion relief and voltage stability. The purpose of the FACTS devices installation is to provide benefit for all entities accomplished by both minimizing annual device investment cost and maximizing annual benefit defined as difference between expected security cost (ESC) with and without FACTS devices installation. Different from previous approaches, the proposed method accurately evaluates the annual cost and benefits obtainable by FACTS devices installation by formulating a large-scale optimization problem that contains power flow analyses for a large number of system states representing annual power system operations. In addition, dynamic state transitions caused by specified contingencies are also simulated in the optimization problem to evaluate the effect of FACTS control actions as well as the other coordinated controls. The expected cost consists of operating cost under normal and contingency states along with their related probabilities to occur. Maximizing social welfare is the objective for normal state while minimizing compensations for generations re-scheduling and load shedding as well as maximizing social welfare are the objectives in case of contingency. Although installation cost of FACTS devices is required, they are useful as cost free means, which can reduce effectively the annual costs for generations re-scheduling and load shedding.

The most important reference quantities for monitoring and controlling transient stability in real time are the rotor angle and speed of the synchronous generators. If these quantities can be estimated with sufficient accuracy, they can be used in global and local control methods. In the classic state estimation methods, such as the extended Kalman filter (EKF) technique, the linear approximations of the system at a given moment in time may introduce errors in the states. In order to overcome the drawbacks of the EKF, the authors of this paper have applied the unscented Kalman filter (UKF) to estimating and predicting the states of a synchronous machine, including rotor angle and rotor speed, using phasor measurement unit (PMU) quantities. The UKF algorithm propagates the pdf of a random variable in a simple and effective way and is accurate up to the second order in estimating the mean and covariance. The overall impression is that the performance of the UKF is better than the EKF in terms of robustness, speed of convergence, and also different levels of noise. Simulation results including saturation effects and grid faults show the accuracy and efficiency of the UKF method in state estimation of the system, especially at higher noise ratios.

- by Innocent Kamwa
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- Approximation Theory, Stability, State Estimation, Kalman Filter

In this paper, a novel adaptive strategy to obtain technically justified fault-ride-through requirements for wind turbines (WTs) is proposed. The main objective is to promote an effective integration of wind turbines into power systems with still low penetration levels of wind power based on technical and economical considerations. The level of requirement imposed by the strategy is increased stepwise over time, depending on system characteristics and on wind power penetration level. The idea behind is to introduce stringent requirements only when they are technically needed for a reliable and secure power system operation. Voltage stability support and fault-ride-through requirements are considered in the strategy. Simulations are based on the Chilean transmission network, a midsize isolated power system with still low penetration levels of wind power. Simulations include fixed speed induction generators and doubly fed induction generators. The effects on power system stability of the wind power injections, integrated into the network by adopting the adaptive strategy, are compared with the effects that have the same installed capacity of wind power but only considering WTs able to fulfill stringent requirements (fault-ride-through capability and support voltage stability). Based on simulations and international experience, technically justified requirements for the Chilean case are proposed. Index Terms-Fault-ride-through capability, grid code, transient stability, voltage stability support, wind power, wind turbine. I. INTRODUCTION T HROUGH the years, different grid code requirements for wind turbines (WTs) have been adopted around the world. The differences in the regulations depend on the local needs of the transmission network and the existing wind power penetration level [2]. In a first stage, characterized by low penetra

- by Luis Santiago Vargas
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- Power System, Wind Power, Wind turbine, Reactive Power

We give a comprehensive account of a complex systems ap- proach to large blackouts caused by cascading failure. In- stead of looking at the details of particular blackouts, we study the statistics, dynamics and risk of series of blackouts with approximate global models. North American blackout data suggests that the frequency of large blackouts is gov- erned by a power

- by David Newman and +1
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- Applied Mathematics, Power System, Risk Analysis, Chaos

The objective of the Economic Dispatch Problems (EDPs) of electric power generation is to schedule the committed generating units outputs so as to meet the required load demand at minimum operating cost while satisfying all units and system equality and inequality constraints. Recently, global optimization approaches inspired by swarm intelligence and evolutionary computation approaches have proven to be a potential alternative for the optimization of difficult EDPs. Particle swarm optimization (PSO) is a population-based stochastic algorithm driven by the simulation of a social psychological metaphor instead of the survival of the fittest individual. Inspired by the swarm intelligence and probabilities theories, this work presents the use of combining of PSO, Gaussian probability distribution functions and/or chaotic sequences. In this context, this paper proposes improved PSO approaches for solving EDPs that takes into account nonlinear generator features such as ramp-rate limits and prohibited operating zones in the power system operation. The PSO and its variants are validated for two test systems consisting of 15 and 20 thermal generation units. The proposed combined method outperforms other modern metaheuristic optimization techniques reported in the recent literature in solving for the two constrained EDPs case studies.

- by leandro coelho
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- Probability Theory, Swarm Intelligence, Power System, Particle Swarm Optimization

This paper addresses the problem of coordinating voltage control in a large-scale power system partitioned into control areas operated by independent utilities. Two types of coordination modes are considered to obtain settings for tap changers, generator voltages, and reactive power injections from compensation devices. First, it is supposed that a supervisor entity, with full knowledge and control of the system, makes decisions with respect to long-term settings of individual utilities. Second, the system is operated according to a decentralized coordination scheme that involves no information exchange between utilities. Those methods are compared with current practices on a 4141 bus system with 7 transmission system operators, where the generation dispatch and load demand models vary in discrete steps. Such a discretetime model is sufficient to model any event of relevance with respect to long-term system dynamics. Simulations show that centrally coordinated voltage control yields a significant improvement in terms of both operation costs and reserves for emergency control actions. This paper also emphasizes that, although it involves few changes with respect to current practices, the decentralized coordination scheme improves the operation of multi-utility power systems.

- by Damien Ernst
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- Power System, System Dynamics, Information Exchange, Reactive Power

Dissemination of small size dispersed microgeneration connected to Low Voltage (LV) distribution systems is expected to become an effective mean to face the con- tinuous demand growth in power needs. Under normal operation conditions, the LV distribution system is considered as interconnected with the upstream medium voltage network. However, if a severe disturbance occurs in the medium voltage side, a

- by F. Resende
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- Power System, Distributed System, Power System Operation, Control Strategy
- by Emanuele Ciapessoni and +1
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- Power System, Risk Management, High Voltage, Risk Analysis

A wind farm usually consists of a large number of wind turbine generators (WTGs) connected through an internal electrical network and operating simultaneously. In order to study the impact of a wind farm on the dynamics of the power system, a major issue is to develop adequate equivalent models that allow characterizing the dynamics of all individual WTGs. In this sense, with the advance of power electronics, direct-driven permanent magnet synchronous generators (PMSGs) have drawn increased interest to wind turbine manufacturers due to its advantages over other variable-speed WTGs. This paper presents a comprehensive dynamic equivalent model of a wind farm with direct-driven PMSG wind turbines and its control scheme. The proposed simplified modeling is developed using the state-space averaging technique and is implemented in the MATLAB/Simulink environment. The dynamic performance of the wind farm and its impact on the power system operation is fully evaluated using the phasor simulation method.

wind power in the long run, and our analysis shows that wind power forecasting can serve as an important tool to achieve this goal. a les (k) Generation, block l, thermal unit j, period k Production cost, thermal unit j, period k Start-up cost, thermal unit j, period k Curtailed wind generation, wind unit i, period k, scenario s Energy not served, period k, scenario s pt j () k Generation, thermal unit j, period k Maximum feasible generation, thermal unit j, period k Generation, wind unit i, period k, scenario s Reserve requirement (spinning), scenario s, period k Reserve curtailed, period k, scenario s v j (k) Binary on/off variable, thermal unit j, period k

- by Jean Sumaili
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- Economics, Renewable Energy, Wind Energy, Power System

- by ujjwal rox
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- Power System, Power System Operation, Eigenvalues, Steady state

With ongoing smart grid initiative, there is a considerable need for developing new algorithmic solutions and validating at laboratory level before they can be successfully applied in the power grid. This research work addresses the development of a real time test bed by integrating several hardware's including the Allen Bradley Programmable Logic Controllers (PLC), National Instruments PXI (NI-PXI) controller, Real Time Digital Simulator (RTDS), and Schweitzer Engineering Lab (SEL) devices. This work also integrates the OSIsoft PI Server system and the establishment of data channel over Ethernet/IP for communication and control. The developed test bed is evaluated by simulating a simple test case in RTDS and executing the control logic in PLC. The test bed provides a user friendly Human Machine Interface (HMI) for monitoring and control at different levels of the system along with capabilities for storing the power system data which includes Synchrophasor data for forensic analysis. This test bed will be essentially used for modeling and study of different power system operation control algorithms as well as to investigate cyber vulnerability and mitigation.

- by Anurag Srivastava
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- Power System, User interfaces, Cyber Security, Human Machine Interface

Forecasting of future electricity demand is very important for decision making in power system operation and planning. In recent years, due to privatization and deregulation of the power industry, accurate electricity forecasting has become an important research area for efficient electricity production. This paper presents a time series approach for mid-term load forecasting (MTLF) in order to predict the daily peak load for the next month. The proposed method employs a computational intelligence scheme based on the self-organizing map (SOM) and support vector machine (SVM). According to the similarity degree of the time series load data, SOM is used as a clustering tool to cluster the training data into two subsets, using the Kohonen rule. As a novel machine learning technique, the support vector regression (SVR) is used to fit the testing data based on the clustered subsets, for predicting the daily peak load. Our proposed SOM-SVR load forecasting model is evaluated in MATLAB on the electricity load dataset provided by the Eastern Slovakian Electricity Corporation, which was used in the 2001 European Network on Intelligent Technologies (EUNITE) load forecasting competition. Power load data obtained from (i) Tenaga Nasional Berhad (TNB) for peninsular Malaysia and (ii) PJM for the eastern interconnection grid of the United States of America is used to benchmark the performance of our proposed model. Experimental results obtained indicate that our proposed SOM-SVR technique gives significantly good prediction accuracy for MTLF compared to previously researched findings using the EUNITE, Malaysian and PJM electricity load datasets.

Abstract: The wide use of wind energy in Germany results in a lot of new power system operation problems corresponding especially to the stochastic character of the wind speed and to the not controllable production of energy. The... more

- by Kurt Rohrig
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- Wind Energy, Power System, Power Plant, Wind Power

A curriculum for electrical power engineering based on project based learning (PBL) methodology has been designed. Although the educational program is totally based on PBL, this curriculum is comprised of two types of study units. Some study units are based on a combination of lectures, tutorials and problem based learning techniques. Others are fully based on PBL. As an example of a fully PBL study unit, a course in power system analysis has been developed. For delivering the course in PBL, a power system laboratory has been established, which gives students access to professional software packages. Realworld industry-relevant projects are defined in the areas of power system operation and planning. These projects are used as stimuli for student learning. Portfolio assessment is used to assess students learning outcome. The first delivery of the course has been successful with positive feedback from students.

- by N Hosseinzadeh
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- Power Systems, Curriculum Design, Engineering Education, Power System

Notice of Violation of IEEE Publication Principles"A Dynamic Distributed Diagnosis Algorithm for an Arbitrary Network Topology with Unreliable Nodes and Links,"by Pabitra Mohan Khilar and Sudipta Mahapatra,in the Proceedings of the International Conference on Advanced Computing and Communications, 2007. ADCOM, Dec. 2007, pp. 125-130After careful and considered review of the content and authorship of this paper by a duly constituted expert committee, this paper has been found to be in violation of IEEE's Publication Principles.This paper contains significant portions of original text from the paper cited below. The original text was copied without attribution (including appropriate references to the original author(s) and/or paper title) and without permission.Due to the nature of this violation, reasonable effort should be made to remove all past references to this paper, and future references should be made to the following article:"A Distributed Network Connectivity Algorithm,"By E. Procopio Duarte Jr. and A.Weber,The Sixth International Symposium on Autonomous Decentralized Systems, 2003. ISADS 2003 April 2003, pp. 285-292This paper presents a distributed network diagnosis (DND) algorithm for an arbitrary network topology where every node needs to record the status of every other nodes and links assuming the nodes and links are subjected to crash and value faults in a dynamic fault environment (the node's or link's status may change during execution of algorithm). The algorithm operates correctly in each connected component if the network is partitioned due to a set of faulty links or faulty nodes. The worst-case bounds for diagnostic latency is at most O(td) rounds where t is the number of dissemination trees and d is the diameter of the network. The proposed approach uses non-broadcasting method of message dissemination that has similar diagnostic latency with flooding [4] and similar message co- mplexity with Chinese Agent [14] method of message dissemination respectively.

- by Sudipta Mahapatra
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- Information Technology, Wind Energy, Fuzzy Logic, Power System

This paper presents the basis for a new approach to solving the problem of inter-utility power transactions in deregulated electricity markets. The problem is formulated as an optimization approach with a nonlinear objective function and linear constraints. An example system is discussed, presenting the operation state for inter-utility transactions based on the equal-lambda criterion. The same example is presented for the proposed method and the results are discussed.

- by Roberto Ferrero
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- Power System, Electricity Market, Power System Operation, Economic Dispatch
- by Jose Cedeno
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- Power System, Power System Operation, Evolutionary Algorithm, Evolution Strategy

This paper presents a methodology for estimating the normalized transient stability margin by using the multilayered perceptron (MLP) neural network. The complex relationship between the input variables and output variables is established by using the neural networks. The nonlinear mapping relation between the normalized transient stability margin and the operating conditions of the power system is established by using the MLP neural network. To obtain the training set of the neural network the potential energy boundary surface (PEBS) method along with time domain simulation method is used. The proposed method is applied on IEEE 9 bus system and the results shows that the proposed method provides fast and accurate tool to assess online transient stability.

- by shishir ranjan
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- Engineering, Power System, Neural Networks, Neural Network
- by Ubiratan Holanda Bezerra Bezerra
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- Engineering, Optimal Control, Genetic Algorithms, Power System

The interconnection of wind sources characterized by a significant variability of generated power and the continuous growth of installed power in wind farms raises a number of specific problems both to the utilities and to the power system operator. One of these issues is to ensure the safe operation of the power system when the reduction of the wind generated power occurs. The compensation of not generated power by these wind sources has to be done by other sources that must ensure the necessary power reserve. The paper deals with the access of the wind farms to the Romanian transport system, both from the legislative (policies, regulations, certificates, and incentives) and from the power quality point of view. The flicker study becomes necessary as the wind power penetration level increases quickly.

- by Mariacristina Roscia
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- Power Quality, Power System, Wind Power, Legislation

Power" collects and shares information on wind power impacts on power systems, with analyses and guidelines on methodologies. There are dozens of studies made and ongoing related to wind integration, however, the results are not easy to compare. In the state-of-the-art report (October, 2007), and the final report of the 3 years period (July, 2009) the most relevant wind power grid integration studies have been analysed especially regarding methodologies and input data. Several issues that impact on the amount of wind power that can be integrated have been identified. Large balancing areas and aggregation benefits of large areas help in reducing the variability and forecast errors of wind power as well as help in pooling more cost effective balancing resources. System operation and functioning electricity markets at less than dayahead time scales help reduce forecast errors of wind power. Transmission is the key to aggregation benefits, electricity markets and larger balancing areas. Best practices in wind integration studies are described. There is also benefit when adding wind power to power systems: it reduces the total operating costs and emissions as wind replaces fossil fuels and this should be highlighted more in future studies.

- by Ana I Estanqueiro and +2
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- Mechanical Engineering, Wind Energy, Power System, Wind Power

- by stephy thiraviam
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- Engineering, Power Electronics, Renewable Energy, Power System

This article presents a survey of different possible technical solutions for the grid integration of wind farms. These solutions concern the main problems encountered today and, whenever possible, examples of actual implementation in wind farm projects are given. More specifically the following types of solutions are discussed: choice of an appropriate wind turbine generator technology; solutions based on co-ordinated wind farms and power system operation; reactive compensation and voltage control systems; fault ride-through systems; energy storage systems; current limitation devices; directional protections; etc. Copyright © 2005 John Wiley & Sons, Ltd.

- by pierre bousseau
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- Mechanical Engineering, Wind Energy, Power Quality, Wind

This paper presents the simultaneous tuning of power system stabilizers in a multi-machine power system. The problem of selecting the parameters of power system stabilizers in converted into an optimization problem that is solved by genetic algorithm using eigen value based objective function. The dynamic performance of the system has been investigated under small perturbation and large disturbance. The performance of genetic algorithm based PSS has been compared with the conventional power system stabilizer. The non-linear simulation results on 4 machine, 11 bus system verifies the effectiveness of the proposed genetic algorithm based power system stabilizers.

- by Mohammad Abido
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- Power Systems, Power System, Genetic Algorithm, Optimization Problem

This paper presents a frequency response analysis approach suitable for a power system control area in a wide range of operating conditions. The analytic approach uses the well-known system frequency response model for the turbine-governor and load units to obtain the mathematical representation of the basic concepts. Primary and supplementary frequency controls are properly considered and the effect of emergency control/protection schemes is included. Therefore, the proposed analysis/modeling approach could be gainfully used for the power system operation during the contingency and normal conditions. Time-domain nonlinear simulations with a power system example showed that the results agree with those predicted analytically.

- by Hassan Bevrani and +1
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- Power System, Electric Power Systems, Power System Operation, Power system control

During power system operations, the system operators are often struggling with identifying the dynamic operating security modes of the system in a fast, accurate and reliable manner. The system security constraints are in fact boundaries that surround all possible operating modes (scenarios) of the power system. In other words, these boundaries form the feasible operating domain -in the parameter space spanned by various operating variables -within which the system can safely be operated. For a given operating scenario, the associated security level is measured by the "distance" (for example, the Euclidean norm) of the operating point from the security region boundary. This paper reports on the results of a recently completed research and development paper, which included the development of innovative computerized schemes, which are capable of identifying dynamic operating security modes during the on-line operation of electric power systems. The methodology adopted in this paper includes the development of advanced, highly efficient computerized algorithms for fast identification of dynamic operating security modes of power systems. One of the salient outcomes of this paper is the development of a novel framework for identification and representation of operating security regions in power systems as well as evaluation of security levels associated with different operating scenarios. While the concepts and principles presented are general, the work of this paper is confined to the interpretation of the security boundary in terms of system stability criteria. Of course, the framework presented is applicable quite as well to other criteria that may be considered.

- by Essam Al-ammar and +1
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- Power System, Research and Development, Power System Operation, Electric Power System

Wind energy is the current "star" in the field of renewable energy for electrical production. Still, the power generated by wind turbines over time is characteristically uneven due to the unpredictable nature of their primary source of power. This only increases the problems inherent to the integration of a great number of wind turbines into power networks, making their contribution rather difficult to manage (regulating voltage and frequency, wind-farm operation, etc.) The integration of wind power in the power system is now an issue in order to optimize the utilization of the resource and in order to continue the high rate of installation of wind generating capacity, which is necessary in order to achieve the goals of sustainability and security of supply. This paper presents the main technical challenges that are associated with the integration of wind power into power systems. These challenges include effects of wind power on the power system, the power system operating cost, power quality and power imbalances (stability of grid). In addition, the paper presents the solutions will be offered to improve the management of wind power generation and increase its penetration in the overall electrical energy production.

- by Mazen Ghandour and +2
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- Renewable Energy, Wind Energy, Power Quality, Power System

- by Ignacio León
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- Power Electronics, Renewable Energy, renewable Energy sources, Power Generation