333 results
Search Results
2. Kappa Number Prediction of Pulp Digester Using LSTM Neural Network
- Author
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Diew Koolpiruck and Arinchai Phatwong
- Subjects
Artificial neural network ,business.industry ,Deep learning ,Pulp (paper) ,Feed forward ,System identification ,engineering.material ,Kappa number ,Kraft process ,engineering ,Artificial intelligence ,business ,Biological system ,Kappa ,Mathematics - Abstract
A digester, one of the major units of Kraft process, has a function for conversion of wood into wood pulp. It is controlled by monitoring Kappa number with nonlinear reaction and has a long resident time. This paper aims to present the prediction of kappa number in pulp digester in advance for 1-3 hours by using Long Short-Term Memory (LSTM) neural network. The structures of LSTM inputs consists of effective alkali, temperature, and outlet lignin content. The prediction has been developed with nonlinear simulations of digester reactions. The results reveal that a kappa prediction can be predicted in advance for 1, 2 and 3 hours with percentages of error 1.1, 1.9 and 2.9 respectively. It could be beneficial for an operator to decide on feedforward compensation before it is out of control.
- Published
- 2019
3. Statistical Analysis of Agarwood Oil Compounds based on GC-MS Data
- Author
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Saiful Nizam Tajuddin, Nurlaila Ismail, Mohd Nasir Taib, Nor Azah Mohd Ali, and Mohamad Hushnie Haron
- Subjects
040101 forestry ,biology ,0211 other engineering and technologies ,04 agricultural and veterinary sciences ,02 engineering and technology ,Agarwood ,engineering.material ,Pulp and paper industry ,biology.organism_classification ,Odor ,engineering ,Aquilaria ,0401 agriculture, forestry, and fisheries ,Statistical analysis ,Gas chromatography–mass spectrometry ,021101 geological & geomatics engineering ,Mathematics - Abstract
Agarwood is a resinous heartwood and Aquilaria is one of many species that grows a lot in Asia. Traditionally, the quality of agarwood oil is based on color, odor, high fixative properties and consumer perception. This quality grading is performed by trained human graders using sensory panels. Human sensory panels has limitation such as fatigue. Therefore, this study focuses on chemical compounds of Agarwood oil. Using this compounds together with artificial intelligence technique, a new grading system will be proposed. This paper discusses only on the statistical analysis of the chemical compounds. 106 compounds were acquired using GC-MS analysis. To remove insignificant compounds, missing values ratio was computed and out of 109 only 19 compounds remained. These compounds were transformed using natural logarithm to improves the distribution of data.
- Published
- 2018
4. Design and Construction of oil palm fronds (OPF) Compost Mixer Machine Type Rotary Double Helix Drum
- Author
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Mustaqimah, Rahmah Rahmah, Agustami Sitorus, T Dewi Sartika, Andi Rinaldi Hasan, and Ramayanty Bulan
- Subjects
0106 biological sciences ,Frond ,biology ,Compost ,020209 energy ,Mixing (process engineering) ,Rotational speed ,02 engineering and technology ,Drum ,engineering.material ,Elaeis guineensis ,biology.organism_classification ,Pulp and paper industry ,01 natural sciences ,010601 ecology ,0202 electrical engineering, electronic engineering, information engineering ,Palm oil ,engineering ,Process time ,Mathematics - Abstract
Palm oil (Elaeis guineensis Jacq) is a plant that provides many benefits. However, oil palm plantations contribute a lot of waste, especially oil palm fronds (OPF). But OPF can be processed into compost. The compost processing made from palm fronds requires mixing to make the material evenly distributed. This process requires machines and equipment called mixer machine. Therefore, the purpose of this study was to design and construct a rotary double machine helix drum type. Machine testing was carried out at three mixer rotation speed levels (100 rpm, 300 rpm, and 500 rpm), two levels of mixing process time (10 minutes and 15 minutes) and two compost method (natural and bokashi). The parameters observed were the productive capacity of the machine, the percentage of compost material left on the machine and the percentage of compost material that was unmixing. In the natural composting method, it is obtained that with the increase of the mixer rotational speed, the engine capacity will also increase at all processing times. However, it is different from the percentage of compost material left on the machine and the percentage of compost material that clot when mixer decreases with increasing mixing speed of the mixer at all processing times. In the method of composting, it was found that with the increase of the mixing machine’s rotational speed to 500 rpm it would increase machine capacity at each process time of 10 minutes and 15 minutes to 63.94 kg/hr and 42.69 kg/hr. However, for the percentage of compost left on the machine and the percentage of compost material that unmixing when mixer will decrease to 11.2% (10 minutes processing time), 11.1% (15 minutes processing time), 20.83% (10 minutes process time), 19.94% (15 minute processing time) with increasing mixing machine speed to 500 rpm.
- Published
- 2019
5. The grading of agarwood oil quality using k-Nearest Neighbor (k-NN)
- Author
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Mohd Hezri Fazalul Rahiman, Nurlaila Ismail, Saiful Nizam Tajuddin, Nor Azah Mohd Ali, Mohd Nasir Taib, and Mailina Jamil
- Subjects
engineering ,Oil quality ,Data mining ,Agarwood ,engineering.material ,Pulp and paper industry ,computer.software_genre ,Grading (education) ,computer ,Mathematics ,k-nearest neighbors algorithm - Abstract
This paper presents the application of k-Nearest Neighbor (k-NN) in grading the quality agarwood oil. Six agarwood oil samples obtained at Forest Research Institute Malaysia (FRIM) were extracted and their chemical compounds were examined by GC-MS. The work is followed by the grading system using the proposed k-NN. The study shows that there are 10 significant chemical compounds of agarwood oils. They are β-agarofuran, α-agarofuran, 10-epi-□-eudesmol, □-eudesmol, longifolol, oxo-agarospirol, hexadecanol and eudesmol. These compounds are used as inputs to the k-NN algorithm for grading them. The performance of the k-NN is measured and the highest accuracy obtained by k-NN which is above 83.3% shows that k-NN is a reliable classifier in grading the agarwood oil quality.
- Published
- 2013
6. Classification of the quality of agarwood oils from Malaysia using Z-score technique
- Author
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Mohd Hezri Fazalul Rahiman, Mailina Jamil, Nurlaila Ismail, Nor Azah Mohd Ali, Saiful Nizam Tajuddin, and Mohd Nasir Taib
- Subjects
Chemical technology ,media_common.quotation_subject ,engineering ,Statistical analysis ,Quality (business) ,Agarwood ,engineering.material ,Standard score ,Pulp and paper industry ,media_common ,Mathematics - Abstract
This paper presents classification of the quality of agarwood oils from Malaysia using Z-score technique. Six agarwood oil samples named as MU, MUS, MN, MNS, R5 and HD are analyzed by GC-MS to examine their chemical profiles. The extraction showed that at least forty three volatile compounds are found. The Z-score technique is proposed to identify the significant chemical compounds of the agarwood oils. It is found that six chemical compounds are recognized. They are β-agarofuran, α-agarofuran, 10-epi-□-eudesmol, α-eudesmol, dihydrocollumellarin and □-eudesmol. These volatile compounds have different abundances pattern responsible to the different qualities of agarwood oil such as high and low. The Z-score applied in this study give a promising result in discriminating agarwood oil to high and low quality. It is important and useful in solving the grading agarwood oil system which is currently done manually.
- Published
- 2013
7. Fuzzy modelling of pulp density in a mineral grinding plant
- Author
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M. Guarini, A. Guesalaga, M. Ramos, C. Munoz, and Aldo Cipriano
- Subjects
Mathematics::General Mathematics ,business.industry ,Estimation theory ,Pulp (paper) ,Fuzzy model ,Fuzzy set ,Linear model ,engineering.material ,Fuzzy logic ,Grinding ,Fuzzy modelling ,ComputingMethodologies_PATTERNRECOGNITION ,engineering ,ComputingMethodologies_GENERAL ,Process engineering ,business ,Mathematics - Abstract
This paper describes an identification algorithm of fuzzy models and its application to the modeling of the pulp density in a mineral grinding plant. The parameters of the fuzzy model are estimated using information obtained from a process simulator. The performance of the fuzzy model is only slightly superior to that of a conventional linear model. >
- Published
- 2002
8. Motor load and freeness control of CMP pulp refining
- Author
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S. Bussiere, P. Tessier, Gordon Broderick, and C. Desrochers
- Subjects
Engineering drawing ,Pulp (paper) ,PID controller ,Energy consumption ,Motor load ,engineering.material ,Pulp and paper industry ,visual_art ,Newsprint ,engineering ,Mass flow rate ,visual_art.visual_art_medium ,Specific energy ,Process control ,Mathematics - Abstract
A simple refiner control strategy aimed at minimizing variations in freeness of a Ultra High Yield Sulphite (UHYS) pulp has been implemented in a newsprint mill. The feeder screw speed is being manipulated to compensate for variations in the bulk density of the chip feed and to maintain a constant motor load at the primary refiners. This ensures a more constant mass flow rate through the primary refiners which translates into a more constant primary specific energy. This has resulted in a reduction in motor load fluctuations of about 60% and a reduction in freeness variations of 40%. The final pulp freeness is regulated by manipulating the plate gap of the secondary refiners using on-line freeness measurements made at the outlet of the latency chest. Control of the secondary plate gap has led to an additional 35% reduction of the variation in freeness. This two-stage refining control strategy has reduced the 2-sigma confidence interval for variation in pulp freeness from 48ml to less than 14ml, a reduction of more than 70%. The complete strategy has reduced the refiner energy consumption by 5% and has had a beneficial impact on production. In addition, the strategy has compensated for changes in cooking conditions and their effect on the refining properties of the chips.
- Published
- 1997
9. Unit Commitment With Probabilistic Spinning Reserve and Interruptible Load Considerations.
- Author
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Aminifar, Farrokh, Fotuhi-Firuzabad, Mahmud, and Shahidehpour, Mohammad
- Subjects
PROBABILITY theory ,MATHEMATICS ,ELECTRIC power systems ,ELECTRICITY ,POWER resources ,ENERGY industries ,INTEGER programming ,MATHEMATICAL programming ,ENGINEERING - Abstract
This paper demonstrates how a probabilistic criterion could be explicitly integrated in the unit commitment (UC) formulation. Both spinning reserve and interruptible load are taken into account as the operating reserve facilities. Incorporating the interruption notice time of interruptible load involves some complexities in the evaluation procedure and problem formulation which is considered in this paper. The expected energy not supplied (EENS) is considered as a probabilistic criterion and a new method is proposed to calculate this index in the presence of interruptible load. The reliability-constrained unit commitment (RCUC) problem is formulated based on the mixed-integer programming (MIP) method that can be solved using large-scale commercial solvers. The effectiveness of the proposed formulation is examined using the IEEE-RTS. Numerical results are presented and the implementation issues are discussed. A number of analyses are examined to evaluate the impact of some important factors on the problem solution. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
10. Continuous Newton's Method for Power Flow Analysis.
- Author
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Milano, Federico
- Subjects
ENGINEERING ,ELECTRIC power ,DIFFERENTIAL equations ,BESSEL functions ,NEWTON-Raphson method ,ITERATIVE methods (Mathematics) ,MATHEMATICS ,ALGORITHMS ,RUNGE-Kutta formulas - Abstract
This paper describes the application of the continuous Newton's method to the power flow problem. This method basically consists in formulating the power flow problem as a set of autonomous ordinary differential equations. Based on this formal analogy, we propose an entire family of numerically efficient algorithms for solving ill-conditioned or badly-initialized power flow cases. The paper also shows that the classical Newton-Raphson's method and most robust power flow techniques proposed in the literature are particular cases of the proposed formulation. An example based on a 1254-bus model of the UCTE system is presented and discussed. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
11. Optimal Capacitor Allocation in a Distribution System Considering Operation Costs.
- Author
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Park, Jong-Young, Jin-Man Sohn, and Park, Jong-Keun
- Subjects
CAPACITORS ,DIELECTRIC devices ,ELECTRIC capacity ,ELECTRIC power ,POWER resources ,ELECTRICITY ,GENETIC algorithms ,COMBINATORIAL optimization ,ENGINEERING ,MATHEMATICS - Abstract
This paper proposes the planning method for capacitor installation in a distribution system to reduce the installation costs and minimize the loss of electrical energy. The expected life-time of devices with moving parts depends on the total number of operations, which affects the replacement period and replacement decisions for aging equipment under a limited budget. In this paper, the expected device lifetimes are included in the formulation, and the optimal operation status of the devices is determined using a genetic algorithm. The optimal numbers and locations for capacitor installation are determined based on the optimal operation status. Simulation results in a 69-bus distribution system show that the proposed technique performs better than conventional methods. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
12. Multiobjective Optimization for DG Planning With Load Models.
- Author
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Singh, Deependra, Singh, Devender, and Verma, K. S.
- Subjects
ELECTRICAL load ,ELECTRICITY ,ELECTRIC power ,GENETIC algorithms ,COMBINATORIAL optimization ,DISTRIBUTION (Probability theory) ,POWER resources ,MATHEMATICS ,ENGINEERING - Abstract
This paper presents a multiobjective performance index-based size and location determination of distributed generation in distribution systems with different load models. Normally, a constant power (real and reactive) load model is assumed in most of the studies made in the literature. It is shown that load models can significantly affect the optimal location and sizing of distributed generation (DG) resources in distribution systems. The simulation technique based on genetic algorithms is studied. The studies have been carried out on 16-bus and 37-bus distribution systems. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
13. Scheduling of Head-Sensitive Cascaded Hydro Systems: A Nonlinear Approach.
- Author
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Catalão, J. P. S., Mariano, S. J. P. S., Mendes, V. M. F., and Ferreira, L. A. F. M.
- Subjects
WATER power ,NATURAL resources ,RENEWABLE energy sources ,POWER resources ,ELECTRIC power production ,ELECTRICITY ,ENGINEERING ,MATHEMATICS - Abstract
In this paper, we propose a novel nonlinear approach to solve the short-term hydro scheduling problem under deregulation, considering head-dependency. The actual size of hydro systems, the continuous reservoir dynamics and constraints, the hydraulic coupling of cascaded hydro systems, and the complexity associated with head-sensitive hydroelectric power generation still pose a real challenge to the modelers. These concerns are all accounted for in our approach. Results from a case study based on one of the main Portuguese cascaded hydro systems are presented, showing that the proposed nonlinear approach is proficient. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
14. The Spanish AGC System: Description and Analysis.
- Author
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Egido, Ignacio, Fernández-Bernal, Fidel, and Rouco, Luis
- Subjects
SIMULATION methods & models ,CONFIGURATIONS (Geometry) ,WAVE functions ,ELECTRICITY ,ENGINEERING ,MATHEMATICS - Abstract
This paper describes and analyzes the Spanish AGC system. The differences with respect to a standard hierarchical structure are explained. A simple model useful for simulation is proposed. Using this model, the performance of the system and the influence of several parameters in system response is evaluated. The paper also suggests some changes in the configuration and parameter settings of the system to improve its performance. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
15. A Wide-Band Multi-Port System Equivalent for Real-Time Digital Power System Simulators.
- Author
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Xi Lin, Gole, A. M., and Ming Yu
- Subjects
ELECTRICITY ,ELECTRIC power ,ELECTROMAGNETIC devices ,ELECTRIC transients ,ELECTRIC currents ,ALGORITHMS ,DIGITAL computer simulation ,ENGINEERING ,MATHEMATICS - Abstract
This paper describes a method of developing wide-band multi-port system equivalents for use with real-time digital power system simulators. The proposed equivalent combines a frequency dependent network equivalent (FDNE) for the high frequency electromagnetic transients and a transient stability analysis (TSA) type simulation block for the electromechanical transients. The frequency dependent characteristic for FDNE is obtained by curve-fitting frequency domain admittance characteristics using the vector fitting method. The paper also introduces an approach for approximating the frequency dependent characteristic of large power networks from readily available typical power-flow data. The paper shows how the TSA algorithm can be adapted to a real-time platform. The validity of this method is confirmed with examples, including the study of a multi infeed HVDC system based network. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
16. Robust .Design of a TCSC Oscillation Damping Controller in a Weak 500-kV Interconnection Considering Multiple Power Flow Scenarios and External Disturbances.
- Author
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Simões, Alberto Mota, Savelli, Diego Chaves, Pellanda, Paulo César, Martins, Nelson, and Apkarian, Pierre
- Subjects
OSCILLATIONS ,ELECTRICITY ,ELECTRIC power ,THYRISTORS ,ELECTRIC switchgear ,ENGINEERING ,MATHEMATICS ,ALGORITHMS ,NONSMOOTH optimization - Abstract
The power oscillation damping (POD) controllers implemented in the two thyristor controlled series compensators of the Brazilian North-South (NS) interconnection, in the year 1999, were solely intended to damp the low-frequency NS oscillation mode. These controllers are still under operation and are derived from the modulus of the active power flow in the NS line that is phase-lagged at the frequency of the NS mode and may experience relatively large excursions generated by exogenous disturbances. This paper utilizes the same 1999 data to compare the performance of a proposed robust POD controller design with those of two conventional designs. A recent robust control synthesis algorithm used in this work is based on a nonsmooth optimization technique and has the capability to handle various controller structures, including reduced-order, and to deal with time-domain constraints on both controlled and measured outputs. Moreover, the nonsmooth design technique encompasses multiple operating conditions subject to various test signals, hence building a truly time-domain multi-scenarios approach. According to the results discussed hereafter, this is a key advantage in the industrial context of increasing demand for performance and robustness. The described results relate to a large-scale system model used in the feasibility studies for that interconnection. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
17. Power System Risk Assessment and Control in a Multiobjective Framework.
- Author
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Fei Xiao and McCalley, James D.
- Subjects
RISK assessment ,ELECTRIC power ,ENGINEERING ,MATHEMATICS ,ELECTRICITY ,PROBABILITY theory ,COST ,ELECTRIC potential ,DECISION making ,ALGORITHMS - Abstract
Traditional online security assessment determines whether the system is secure or not, but how secure or insecure is not explicitly indicated. This paper develops probabilistic indices, risk, to assess real-time power system security level. Risk captures not only event likelihood, but also consequence. System security level associated with low voltage and overload can be optimally controlled, using the NSGA multiobjective optimization method. A security diagram is used to visualize operating conditions in a way that enables both risk-based and traditional deterministic views. An index for cascading overloads is used to evaluate the Pareto optimal solutions. This paper shows that the multiobjective approach results in less risky and less costly operating conditions, and it provides a practical algorithm for implementation. The IEEE 24-bus RTS-1996 system is analyzed to show that risk-based system security control results in lower risk, lower cost, and less exposure to cascading outages. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
18. Using State Diagrams for Modeling Maintenance of Deteriorating Systems.
- Author
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Welte, Thomas M.
- Subjects
ENGINEERING ,MATHEMATICS ,MARKOV processes ,STOCHASTIC processes ,PROBABILITY theory ,MONTE Carlo method ,NUMERICAL analysis ,MATHEMATICAL models ,MAINTENANCE - Abstract
This paper discusses the use of state diagrams in maintenance modeling. These diagrams frequently illustrate deterioration, inspections and maintenance. Mathematically, the state diagram can be represented by a Markov process. The paper discusses the properties of such a Markov process. They are compared with the maintenance situation in the real world. It is shown that some properties make the model inconsistent with reality especially in cases where a maintenance policy with non-periodic inspections is modeled. A numerical example is provided that shows that these model properties result in modeling errors. The presented results make it clear that the common practice of using Markov processes based on state diagrams must be judged critically when they are used for modeling certain maintenance strategies. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
19. Historical corner: To C?ligny, in the footprints of Vilfredo Pareto's ?optimum?
- Author
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Pelosi, Giuseppe and Selleri, Stefano
- Subjects
FOOTPRINTS ,SOCIOLOGISTS ,ENGINEERING ,ENGINEERS - Abstract
This short contribution is dedicated to the Italian Vilfredo Pareto [Paris, France, July 15, 1848 ? Celigny, Switzerland, August 19, 1923]. He was an engineer, an econo mist, and a sociologist. Among his many contributions, he stated the Pareto principle (also known as the 80/20 rule), he def ned the Pareto distribution, and the Pareto optimum [1]. Pareto ideas have had a very important impact on engineering, as the queries on IEEE Xplore presented later on in this work will show. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
20. Adaptive Hybrid Genetic Algorithm for Technical Loss Reduction in Distribution Networks Under Variable Demands.
- Author
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Queiroz, Leonardo M. O. and Lyra, Christiano
- Subjects
ALGORITHMS ,MATHEMATICS ,ENGINEERING ,ELECTRIC power distribution ,POWER transmission ,POWER resources ,ELECTRICITY ,ELECTRIC transients ,MATHEMATICAL optimization - Abstract
In power distribution networks the load varies within any given time frame. It may, therefore, seem that a good approach to reduce losses would be the solving of a network reconfiguration problem to suit each of the significant load variations. However, frequent changes in configuration can trigger outages or cause transient problems; they are best avoided. A recent formulation of this problem explicitly considers load variations and proposes to restrain frequent reconfigurations by assuming that network topologies will remain unchanged for a given planning period. This formulation leads to a much larger optimization problem than that traditionally used for network reconfiguration; moreover, it requires a new approach to optimization which is capable of dealing with energy flows instead of only instantaneous power flows. Such an approach is proposed in this paper, which discusses the design of an adaptive hybrid genetic algorithm that fulfills these new requirements. Key concepts in evolutionary computation and analysis of distribution systems are explored to develop this new algorithm. Application to real case studies certifies its benefits. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
21. Flexible Transmission Expansion Planning With Uncertainties in an Electricity Market.
- Author
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Jun Hua Zhao, Zhao Yang Dong, Lindsay, Peter, and Kit Po Wong
- Subjects
DEREGULATION ,ENERGY industries ,ELECTRIC power ,POWER resources ,ELECTRICITY ,NONLINEAR programming ,MATHEMATICAL programming ,MATHEMATICS ,ENGINEERING - Abstract
Deregulation of the electric power industry has introduced new uncertainties for market participants and made planning of transmission expansion more difficult. More flexible transmission expansion plans are needed, to cope with the increased risks. In this paper, a novel planning approach is proposed to meet the above challenge. In our approach, the planning process is modeled as a mixed integer nonlinear programming (MINLP) problem, so that conflicting objectives can be optimized simultaneously. To minimize planning risks, our method identifies several scenarios based on statistics and expert knowledge; the most flexible expansion plan is selected as the plan that has least adaptation cost. The proposed method is tested with the IEEE 14-bus system. Promising results are obtained to demonstrate the effectiveness of our method. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
22. An Annual Midterm Energy Forecasting Model Using Fuzzy Logic.
- Author
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Elias, Charalambos N. and Hatziargyriou, Nikos D.
- Subjects
FUZZY logic ,MATHEMATICAL logic ,FUZZY systems ,MATHEMATICS ,ENGINEERING ,ELECTRIC power ,POWER resources ,ELECTRICITY ,BIOLOGICAL neural networks ,ARTIFICIAL intelligence - Abstract
The objective of this paper is to present a new fuzzy logic method for midterm energy forecasting. The proposed method properly transforms the input variables to differences or relative differences, in order to predict energy values not included in the training set and to use a minimal number of patterns. The input variables, the number of the triangular membership functions and their base widths are simultaneously selected by an optimization process. The standard deviation is calculated analytically by mathematical expressions based on the membership functions. Results from an extensive application of the method to the Greek power system and for different categories of customers are compared to those obtained from the application of standard regression methods and artificial neural networks (ANN). [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
23. Application of NSGA-II Algorithm to Generation Expansion Planning.
- Author
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Kannan, S., Baskar, S., McCalley, James D., and Murugan, P.
- Subjects
GENETIC algorithms ,COMBINATORIAL optimization ,MATHEMATICS ,ENGINEERING ,DECISION making ,INVESTMENTS ,COST ,POWER resources ,ELECTRICITY - Abstract
This paper describes use of a multiobjective optimization method, elitist nondominated sorting genetic algorithm version II (NSGA-II), to the generation expansion planning (GEP) problem. The proposed model provides for decision maker choice from among the different trade-off solutions. Two different problem formulations are considered. In one formulation, the first objective is to minimize cost; the second objective is to minimize sum of normalized constraint violations. In the other formulation, the first objective is to minimize investment cost; the second objective is to minimize outage cost (or maximize reliability). Virtual mapping procedure is introduced to improve the performance of NSGA-II. The GEP problem considered is a test system for a six-year planning horizon having five types of candidate units. The results are compared and validated. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
24. A Stochastic Optimization Approach to Rating of Energy Storage Systems in Wind-Diesel Isolated Grids.
- Author
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Abbey, Chad and Joós, Géza
- Subjects
ENERGY storage ,ELECTRIC power supplies to apparatus ,FORCE & energy ,WIND power ,DIESEL fuels ,CONSUMPTION (Economics) ,OPERATING costs ,MATHEMATICS ,ENGINEERING - Abstract
Wind-diesel systems represent a proactive step towards sustainable remote communities. However, for high ratios of wind energy, the necessity of a dump load and the diesel operating constraints need to be considered. Energy storage systems offer a means of optimizing energy use and further reducing consumption of diesel fuel. This paper proposes a methodology for storage sizing based on stochastic optimization. The problem is formulated and solved using representative data. The dependence of storage sizing and the cost of delivered energy on wind penetration levels, storage efficiency, and diesel operating strategies are considered. Results demonstrate that for high wind penetration, the availability of storage, together with an appropriate diesel operating approach, can result in significant cost savings in terms of fuel and operating costs. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
25. Fuzzy Logic Supervisor-Based Primary Frequency Control Experiments of a Variable-Speed Wind Generator.
- Author
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El Mokadem, Mostafa, Courtecuisse, Vincent, Saudemont, Christophe, Robyns, Benoit, and Deuse, Jacques
- Subjects
FUZZY logic ,MATHEMATICAL logic ,FUZZY systems ,VARIABLE speed generators ,ELECTRIC generators ,ELECTRICITY ,POWER resources ,MATHEMATICS ,ENGINEERING - Abstract
In this paper, a primary frequency control strategy based on fuzzy logic, designed for variable-speed wind generators, is proposed and tested on a 2.2-kW test bench. The fuzzy logic supervisor ensures a regular primary reserve for a large range of wind speeds without any wind speed measurement. This supervisor controls simultaneously the generator torque and the pitch angle to keep the primary reserve; it determines in real time the generator power reference value. The fuzzy logic supervisor is compared to a simpler strategy, based only on the control of the generator torque. This classical strategy ensures a regular power reserve only when the wind generator operates at full load, and the generator power reference needs to be determined previously or by the network manager. A procedure for implementing a fuzzy logic supervisor in real time is proposed. The experiments indicate the regularity of the power reserve and the ability to contribute to frequency control. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
26. Identification of Catastrophic Failures in Power System Using Pattern Recognition and Fuzzy Estimation.
- Author
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Hazra, Jagabondhu and Sinha, Avinash K.
- Subjects
ELECTRIC power systems ,ELECTRICITY ,POWER resources ,PROBABILITY theory ,DATABASES ,MATHEMATICAL decoupling ,MATHEMATICAL inequalities ,ENGINEERING ,MATHEMATICS - Abstract
This paper presents a new approach for finding the sequence of events that may lead to catastrophic failure in a power system. The probable sequences (of events) leading to catastrophic failures are identified using risk indices which incorporate the severity as well as the probability of the contingencies. Probable collapse sequences are identified offline for different possible loading conditions using a modified fast decoupled load flow method which considers the voltage and frequency dependence of loads and generator regulation characteristics and stored in a knowledge base. Pattern recognition method and fuzzy estimation are used for online identification of collapse sequences for any operating condition from the stored database (knowledge base). [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
27. The Dead Band Control of LTC Transformer at Distribution Substation.
- Author
-
Joon-Ho Choi and Seung-Il Moon
- Subjects
ALGORITHMS ,ELECTRIC potential ,POWER resources ,ELECTRICITY ,ELECTRIC power ,ELECTRIC transformers ,CONSUMERS ,ENGINEERING ,MATHEMATICS - Abstract
In this paper, dead band control algorithms using a performance index of the load tap changing (LTC) tap position are proposed to reduce the tap changing operation times. The performance index is defined as the customer voltage quality with the tap position of LTC transformer. In addition, dead band control algorithms using the load diversity values of the feeders are proposed. The mathematical formulations of the proposed dead band control algorithms are introduced. A sample case study is shown to verify the effectiveness of the proposed dead band control algorithms. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
28. Distributed Transient Stability Simulation of Power Systems Based on a Jacobian-Free Newton-GMRES Method.
- Author
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Ying Chen, Chen Shen, and Jian Wang
- Subjects
JACOBIAN matrices ,FUNCTIONS of several complex variables ,ELECTRIC power ,ELECTRICITY ,ALGORITHMS ,ENGINEERING ,MATHEMATICS ,STOCHASTIC convergence ,MATHEMATICAL functions - Abstract
As power systems becoming more closely interconnected and are being deregulated in energy markets, distributed simulations among different dispatch centers are highly required for online full system analysis and control applications. In this paper a new algorithm for distributed transient stability simulation of interconnected power systems is presented. Based on a Jacobian-free Newton-GMRES(m) method, this algorithm requires only exchanges of states of boundary buses among different regions. Therefore, it has strong scalability in distributed computing environments built on heterogeneous computing resources. Moreover, several accelerating methods are developed to enhance its efficiency, including continuous preconditioning with adaptive preconditioners, predicting boundary conditions and multistep coordination. The standard IEEE 39-bus system and a real power system with 1165 buses were used as test systems. The test results show that these accelerating methods greatly enhance the convergence rate of the proposed algorithm and reduce communication costs remarkably, which proves the novel algorithm is feasible and can be adopted in wide area networks with high-latency. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
29. Development of Rule-Based Classifiers for Rapid Stability Assessment of Wide-Area Post-Disturbance Records.
- Author
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Kamwa, I., Samantaray, S. R., and Joos, Geza
- Subjects
DECISION trees ,TREE graphs ,CHARTS, diagrams, etc. ,DECISION making ,DATABASES ,SPECTRAL energy distribution ,SPECTRUM analysis ,ENGINEERING ,MATHEMATICS - Abstract
The paper proposes a systematic scheme for building compact and transparent fuzzy rule-based classifiers for rapid stability assessment; the classifiers are initialized by large accurate decision trees (DTs). The approach starts by selecting strategic monitoring buses where phasor measurement units (PMUs) are placed to capture wide-area response signals in real-time operation. These measurements are processed in the time and frequency domains for extracting selected decision features such as the peak spectral density of the angle, frequency and their dot product evaluated over the grid areas. These so-called wide-area severity indices (WASI) are reliable time-varying stability indicators that form the basis of an effective classification system. Large-size DTs are used to generate initial accurate classification boundaries for decision making as early as 1 s or 2 s after fault clearing. From the DT classification boundaries, fuzzy membership functions (MFs) are developed and the corresponding fuzzy rule base is formulated parsimoniously by eliminating redundant MFs and rules using a similarity measure. The resulting fuzzy-rule classifiers are successfully tested for systemwise and area-wise contingencies based on a large database of detailed simulations of the Hydro-Quebec grid and are further confirmed on actual measurements recorded with existing wide-area measurements (WAMS). [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
30. Induction Machine Modeling Based on Shifted Frequency Analysis.
- Author
-
Peng Zhang, Martí, José R., and Dommel, Hermann W.
- Subjects
ELECTROMAGNETISM ,ELECTROMAGNETIC induction ,ELECTRIC power ,ELECTRICITY ,EQUATIONS ,TRANSIENTS (Dynamics) ,MACHINERY ,ENGINEERING ,MATHEMATICS - Abstract
Electromagnetic transient program (EMTP) simulators are being widely used in power system dynamics studies. However, their capability in real-time simulation of power systems is compromised due to the small time step used and relatively slow simulation speed. The shifted frequency analysis (SFA) is then proposed to accelerate the EMTP simulations for power system dynamics. The objective of this paper is to extend the SFA method [7] to model the induction machines in EMTP. By analyzing the relationship between rotor and stator physical variables, a phase-coordinate model with lower number of equations is first derived. Based on this, an SFA model is proposed as a general purpose model capable of simulating both fast transients and slow dynamics. Case study results have confirmed the SFA induction machine model is a valuable component for real-time EMTP simulations. It is observed that the SFA model is in excess of 70 times faster than the standard EMTP model when simulating dynamics with frequency spectra close to the fundamental power frequency. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
31. Identifying Power Flow Control Infeasibilities in Large-Scale Power System Models.
- Author
-
Filho, João A. Passos, Martins, Nelson, and Falcão, Djalma M.
- Subjects
ELECTRIC power ,ELECTRICITY ,ENGINEERING ,MATHEMATICS ,STOCHASTIC convergence ,MATHEMATICAL functions ,EIGENVALUES ,MATRICES (Mathematics) ,JACOBIAN matrices - Abstract
This paper describes a methodology to identify potential conflicts among power flow control devices that may slow down or impair convergence. The proposed methodology is based on the eigenvalue analysis of the sparse Jacobian matrix associated with the Newton power flow with controls. Practically identical results are obtained from a smaller control sensitivity matrix. The implementation in a power flow program has been tested using both small- and large-scale systems. The results presented validate and clearly indicate the effectiveness of the proposed technique. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
32. Radial Power Flow Tolerance Analysis by Interval Constraint Propagation.
- Author
-
Vaccaro, Alfredo and Villacci, Domenico
- Subjects
ENGINEERING ,ALGORITHMS ,INTERVAL analysis ,NUMERICAL analysis ,ELECTRIC power distribution ,METHODOLOGY ,NONLINEAR systems ,SYSTEMS theory ,MATHEMATICS - Abstract
Many applications in modern distribution management systems (DMS) need the support of robust and reliable radial power flow analysis. In this connection, although radial power flow solution algorithms are widely proposed in the literature, their application is often complicated by the presence of uncertainties affecting the distribution network operation. The effect of these uncertainties could affect the power flow solution to a considerable extent. A comprehensive tolerance analysis is therefore required in order to incorporate the effect of data uncertainties into power flow analysis. To address this problem, in this paper the employment of interval constraint propagation (ICP) is proposed. ICP is an effective technique for refining enclosures to solutions of nonlinear systems of equations by merging interval mathematic and constraint propagation techniques. Several numerical results are presented and discussed in order to assess the effectiveness of the proposed methodology as an alternative to sampling-based technique, in radial power flow analysis. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
33. Implementing Spiking Neural Networks for Real-Time Signal-Processing and Control Applications: A Model-Validated FPGA Approach.
- Author
-
Pearson, Martin J., Pipe, A. G., Mitchinson, B., Gurney, K., Meihuish, C., Gilhespy, I., and Nibouche, M.
- Subjects
ARTIFICIAL neural networks ,ARTIFICIAL intelligence ,EVOLUTIONARY computation ,SELF-organizing maps ,COMPUTER arithmetic ,FLOATING-point arithmetic ,MATHEMATICS ,ROBOTICS ,ENGINEERING - Abstract
In this paper, we present two versions of a hardware processing architecture for modeling large networks of leaky-integrate-and-fire (LIF) neurons; the second version provides performance enhancing features relative to the first. Both versions of the architecture use fixed-point arithmetic and have been implemented using a single field-programmable gate array (FPGA). They have successfully simulated networks of over 1000 neurons configured using biologically plausible models of mammalian neural systems. The neuroprocessor has been designed to be employed primarily for use on mobile robotic vehicles, allowing bio-inspired neural processing models to be integrated directly into real-world control environments. When a neuroprocessor has been designed to act as part of the closed-loop system of a feedback controller, it is imperative to maintain strict real-time performance at all times, in order to maintain integrity of the control system. This resulted in the reevaluation of some of the architectural features of existing hardware for biologically plausible neural networks (NNs). In addition, we describe a development system for rapidly porting an underlying model (based on floating-point arithmetic) to the fixed-point representation of the FPGA-based neuroprocessor, thereby allowing validation of the hardware architecture. The developmental system environment facilitates the cooperation of computational neuroscientists and engineers working on embodied (robotic) systems with neural controllers, as demonstrated by our own experience on the Whiskerbot project, in which we developed models of the rodent whisker sensory system. [ABSTRACT FROM AUTHOR]
- Published
- 2007
- Full Text
- View/download PDF
34. Reliability Modeling of Multi-State Degraded Systems With Multi-Competing Failures and Random Shocks.
- Author
-
Li, Wenjian and Pham, Hoang
- Subjects
RELIABILITY in engineering ,PROBABILITY theory ,METHODOLOGY ,MATHEMATICS ,ENGINEERING ,MAINTAINABILITY (Engineering) - Abstract
In this paper, we develop a generalized multi-state degraded system reliability model subject to multiple competing failure processes, including two degradation processes, and random shocks. The operating condition of the multi-state systems is characterized by a finite number of states. We also present a methodology to generate the system states when there are multi- failure processes. The model can be used not only to determine the reliability of the degraded systems In the context of multi-state functions, but also to obtain the states of the systems by calculating the system state probabilities. Several numerical examples are given to Illustrate the concepts. [ABSTRACT FROM AUTHOR]
- Published
- 2005
- Full Text
- View/download PDF
35. A Reliability-Centered Asset Maintenance Method for Assessing the Impact of Maintenance in Power Distribution Systems.
- Author
-
Bertling, Lina, Allan, Ron, and Eriksson, Roland
- Subjects
STATISTICS ,MAINTENANCE ,FAILURE time data analysis ,COST ,ENGINEERING ,MATHEMATICS - Abstract
This paper proposes a method for comparing the effect of different maintenance strategies on system reliability and cost. This method relates reliability theory with the experience gained from statistics and practical knowledge of component failures and maintenance measures. The approach has been applied to rural and urban distribution systems. In particular, a functional relationship between failure rate and maintenance measures has been developed for a cable component. The results show the value of using a systematic quantitative approach for investigating the effect of different maintenance strategies. [ABSTRACT FROM AUTHOR]
- Published
- 2005
- Full Text
- View/download PDF
36. New Challenges in Power System Restoration With Large Scale of Dispersed Generation Insertion.
- Author
-
Thi Thu Ha Pham, Bésanger, Yvon, and Hadjsaid, Nouredine
- Subjects
ELECTRIC power systems ,ELECTRICITY ,POWER resources ,ALGORITHMS ,DISTRIBUTION (Probability theory) ,MATHEMATICS ,ENGINEERING - Abstract
The ability of using dispersed generation (DG) in the distribution system restoration service in the context of smart networks is presented in this paper. The objectives are to reduce the consequences due to a major blackout in terms of the out-of-service load volume, and the duration of restoration process. Based on knapsack problem formulation and network represented graph modeling, a new restoration procedure for distribution network is proposed. An adapted branch-and-bound algorithm is then used to solve the problem. It maximizes the restored loads in distribution by using the DG availability. Simulation results on a study case will be shown to illustrate the proposed procedure and quantify the benefit of using DG in critical situations. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
37. Prediction of Power System Security Levels.
- Author
-
Halilčević, Suad S., Gubina, Ferdinand, and Gubina, Andrej F.
- Subjects
MARKOV processes ,STOCHASTIC processes ,MONTE Carlo method ,NUMERICAL analysis ,ELECTRIC power systems ,ELECTRICITY ,POWER resources ,ENGINEERING ,MATHEMATICS - Abstract
In the paper, Markov chains in conjunction with Monte Carlo simulation are used to predict the power system security level. The new approach uses a Markov chain for each identified security range to track the development of security level through time. Based on the forecasted and recorded data, the proposed procedure offers a useful tool to the system operator to predict a future power system security level. The method has been tested on the Bosnian power system using the recorded data on security levels during a one-year period. The forecasted results show a striking coincidence with the real security levels. By means of a simple and computationally fast method, the system operator can estimate the probability of a power system blackout. The presented method could be incorporated in the wide-area monitoring system in control centers. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
38. A Study on the Effect of Generation Shedding to Total Transfer Capability by Means of Transient Stability Constrained Optimal Power Flow.
- Author
-
Hakim, Lukmanul, Kubokawa, Junji, Yue Yuan, Mitani, Tomohisa, Zoka, Yoshifumi, Yorino, Naoto, Niwa, Yoshihito, Shimomura, Kimihiko, and Takeuchi, Akira
- Subjects
ELECTRIC transients ,ELECTRIC appliance protection ,POWER resources ,ELECTRICITY ,ELECTRIC power systems ,LAGRANGE equations ,DIFFERENTIAL equations ,ENGINEERING ,MATHEMATICS - Abstract
In nowadays deregulated market, total transfer capability (TTC) calculation, which is the basis for evaluating available transfer capability (ATC), has been becoming more significant. During the last decade, transient stability constraints have been included in the optimal power flow approach to maximize TTC. However, no previous work on investigating the effect of generation shedding action to TTC has been reported. Therefore, in this paper, we propose a TTC maximization by means of transient stability constrained optimal power flow considering the generation shedding action. Proper selection of the generator to shed is based on its Lagrange multiplier value of transient stability constraint. Our simulation results show how TTC can be increased to anticipate possible generation shedding. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
39. A Generic Operations Framework for Discos in Retail Electricity Markets.
- Author
-
Algarni, Ayed A. S. and Bhattacharya, Kankar
- Subjects
ELECTRICITY ,POWER resources ,ELECTRIC power ,ECONOMIC competition ,ELECTRIC industries ,DECISION making ,COST ,ENGINEERING ,MATHEMATICS - Abstract
A generic operations framework for a distribution company (disco) operating in a competitive electricity market environment is presented in this paper. The operations framework is a two-stage hierarchical model in which the first deals with disco's activities in the day-ahead stage, the Day Ahead Operations Model (DAOM). The second deals with disco's activities in real-time and is termed Real-Time Operations Model (RTOM). The DAOM determines the disco's operational decisions on grid purchase, scheduling of distributed generation (DG) units owned by it, and contracting for interruptible load. These decisions are imposed as boundary constraints in the RTOM and the disco seeks to minimize its short-term costs keeping in mind its day-ahead decisions. A case-study is presented considering the well-known 33-bus distribution system and three different scenarios are constructed to analyze the disco's actions and decision-making in this context. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
40. Decentralized Optimal Power Flow Control for Overlapping Areas in Power Systems.
- Author
-
Hug-Glanzmann, Gabriela and Andersson, Göran
- Subjects
POWER resources ,ELECTRICITY ,ELECTRIC power ,ELECTROMECHANICAL devices ,MATHEMATICAL physics ,ENGINEERING ,MATHEMATICS - Abstract
The task of controlling a power system is generally accomplished by several entities, each responsible for a distinct part of the system. For the enhancement of the system security, controllable devices such as FACTS devices are installed and operated by these entities. But in order to avoid conflicting behavior coordination is needed, leading to the concept of multiarea control. In this paper, it is assumed that the areas are determined independently from each other according to the influence of the control devices. As a consequence, overlapping areas may result necessitating an extension of the applied multiarea control method based on approximate Newton directions. In addition, it is taken into account that part of the grid might not be included in any of the areas. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
41. Assessment and Enhancement of Small Signal Stability Considering Uncertainties.
- Author
-
Rueda, José L., Colomé, Delia G., and Erlich, Istvan
- Subjects
PROBABILITY theory ,MONTE Carlo method ,STOCHASTIC processes ,NUMERICAL analysis ,ELECTRIC power ,ELECTRICITY ,OSCILLATIONS ,ENGINEERING ,MATHEMATICS - Abstract
This paper proposes a probabilistic small signal stability assessment (PSSSA) methodology based on the application of Monte Carlo approach for iterative evaluation, via modal analysis of small signal stability (SSS). Operation states represented by random values of generation and demand are analyzed. A probabilistic instability risk index based on cumulative probability distribution function of damping ratios of oscillatory modes is calculated, as well as a power system stabilizer (PSS) devices location index based on eigenvectors and participation factors, which are considered random variables. Moreover, the impact of long-distance power flows on oscillatory modes (OM) and how the damping of OM depends on the orientation and magnitude of power flows is investigated. Further, an additional index concerns qualitatively the determination of transfer capability as affected by small signal stability. PSSSA is tested on a reduced order model of New England-New York's interconnected system considering uncertainties around three different system conditions separately: highly loaded, fairly loaded, and lowly loaded. The results highlight the main advantages of PSSSA over deterministic SSS studies such as instability risk assessment, small signal stability enhancement through adequate PSS location, and the proposal of possible restrictions for transfer capability in order to avoid poorly damped oscillations in the face of the diversity in power system operation. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
42. Optimization Study on Voltage Level and Transmission Capacity.
- Author
-
Zhang Jinhua
- Subjects
ELECTRIC potential ,WATER power ,RENEWABLE energy sources ,POWER resources ,ELECTRIC power ,ENGINEERING ,MATHEMATICS - Abstract
Jinsha River has very abundant hydro power reservation, ranking first in all the hydro power bases of China. To deliver the 38-GW hydro power from Jinsha power stations by HVDC transmission lines to load centers 1000-2000 km away, it is necessary to determine the right voltage level and the capacity of each bipole. This paper proposes three preliminary power delivery scheme and presents an optimization method for transmission capacity, dc voltage and conductor size. Based on a comprehensive comparison of cost-effectiveness, technical feasibility and network security and stability, it was recommended that the 3 bipolar ±800-kV ultra HVDC (UHVDC) links with rated capacity of 6.4 GW for each link be adopted as transmission scheme of Phase I Hydro Power station on Jinsha River. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
43. Investigation of StatComs With Capacitive Energy Storage for Reduction of Voltage Phase Jumps in Weak Networks.
- Author
-
Hailian Xie, Ängquist, Lennart, and Nee, Hans-Peter
- Subjects
ENERGY storage ,ELECTRIC power supplies to apparatus ,POWER (Mechanics) ,FORCE & energy ,ELECTRIC potential ,FLUCTUATIONS (Physics) ,ELECTRICITY ,ENGINEERING ,MATHEMATICS - Abstract
The voltage at the point of common coupling (PCC) in a weak network is very sensitive to load changes. A sudden change in active load will cause both a phase jump and a magnitude fluctuation in the bus voltage (voltage at the PCC), whereas reactive load changes mainly affect the voltage magnitude. With the addition of energy storage to a static synchronous compensator (StatCom), it is possible to compensate for the active power change as well as providing reactive power support. In this paper effective active power compensation schemes are proposed. Simulation and experimental results verify the compensation schemes by showing that a StatCom with energy storage can significantly reduce phase jumps and magnitude deviations of the bus voltage under load disturbances. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
44. Wide-Area Measurements-Based Two-Level Control Design Considering Signal Transmission Delay.
- Author
-
Dotta, Daniel, e Silva, Aguinaldo S., and Decker, Ildemar C.
- Subjects
ELECTRIC power ,ELECTRICITY ,TIME delay systems ,STOCHASTIC convergence ,COMMUNICATION ,MATRICES (Mathematics) ,ENGINEERING ,MATHEMATICS - Abstract
In this paper the design of power system stabilizers for small-signal stability using phasor measurements is considered. An approach based on optimal control with structural constraints is proposed to design a two-level control structure. Time delays are included in the design. The method is combined with order reduction to ensure faster convergence of the design algorithm and to facilitate the choice of the weighting matrices for damping inter-area modes. The control scheme is discussed and modal analysis and time-domain simulations of two Brazilian equivalent systems are performed to assess the control performance. The robustness to loss of communication links, topological changes, and variations of time delay is evaluated. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
45. Frequency Regulation Contribution Through Variable-Speed Wind Energy Conversion Systems.
- Author
-
Mauricio, Juan Manuel, Marano, Alejandro, Gómez-Expósito, Antonio, and Ramos, José Luis Martínez
- Subjects
WIND energy conversion systems ,WIND power ,VARIABLE speed generators ,ELECTRIC generators ,ELECTRIC power production ,POWER resources ,ELECTRICITY ,ENGINEERING ,MATHEMATICS - Abstract
This paper presents a new method to enhance the participation of variable-speed wind energy conversion systems (WECS) in existing frequency regulation mechanisms. The proposed approach, based on a modified inertial control scheme, takes advantage of the fast response capability associated with electronically-controlled WECS, allowing the kinetic energy stored by rotational masses to be partly and transiently released in order to provide earlier frequency support. An additional improvement is achieved by communicating the WECS response to conventional generators so that these can eventually take care of the full load imbalance. Several simulations using a two-area test system are performed to demonstrate the benefits of the proposed scheme. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
46. Admissible Locational Marginal Prices via Laplacian Structure in Network Constraints.
- Author
-
Chéverez-González, Daniel and DeMarco, Christopher L.
- Subjects
PRICES ,LAPLACIAN operator ,PARTIAL differential equations ,LAGRANGE equations ,JACOBIAN matrices ,ELECTRIC power ,ELECTRICITY ,ENGINEERING ,MATHEMATICS - Abstract
Standard computations reveal that locational marginal prices (LMPs), being Lagrange multipliers in an optimization problem, must lie in the null space of a Jacobian matrix evaluated at the optimal power flow solution, augmented by columns associated with active line flow limits. The impact of network power flow and active line limit constraints is to confine the LMPs in a subspace that satisfies necessary conditions for optimality. Optimal market clearing can then proceed as a minimization over offer curves confined to admissible LMPs in this subspace. When no line limits are active and losses neglected (e.g., in a dc power flow representation), the matrix in question has a generalized Laplacian structure, and admits only a vector of all equal elements in its null space (verifying the well-known equal incremental cost condition). As line flow limits become active, the null space grows in dimension. Among the phenomena of interest as the dimension of admissible LMPs grows is that of "load pockets"; that is, admissible LMP vectors that can show patterns in which buses partition into zones of approximately equal LMPs, with significant differences between zones. This paper explores an approach to admissible LMP calculation that isolates the topological role of active line flow constraints, independent of offer curve prices. Identification of this admissible subspace can then greatly facilitate computations such as clustering to identify potential zones of differentiated LMPs. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
47. Response of Fixed Speed Wind Turbines to System Frequency Disturbances.
- Author
-
Sumper, Andreas, Gomis-Bellmunt, Oriol, Sudria-Andreu, Antoni, Villafafila-Robles, Roberto, and Rull-Duran, Joan
- Subjects
WIND turbines ,WINDMILLS ,ELECTRIC power ,POWER resources ,ELECTRICITY ,INDUCTION machinery ,FREQUENCY response ,ENGINEERING ,MATHEMATICS - Abstract
This paper analyzes the impact of system frequency variations on the steady-state operation point of fixed speed induction generators used in wind turbine generation systems (WTGS). An analytic method to predict the values of angular speed, torque and current during and after a frequency disturbance is presented. The proposed method as well permits to establish the operation limits in order to keep the WTGS connected during frequency variations and therefore to adjust protection relay settings. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
48. Overload Alleviation With Preventive-Corrective Static Security Using Fuzzy Logic.
- Author
-
Lenoir, Laurent, Kamwa, Innocent, and Dessaint, Louis-A.
- Subjects
FUZZY logic ,MATHEMATICAL logic ,ELECTRIC power production ,ELECTRICITY ,ELECTRICAL engineering ,DATA transmission systems ,ENGINEERING ,MATHEMATICS - Abstract
This paper presents a concept overview of an automatic operator of electrical networks (AOEN) for real-time alleviation of component overloads and increase of system static load-ability, based on state-estimator data only. The control used for this purpose is real-power generation rescheduling, although any other control input could fit the new framework. The key performance metrics are the vulnerability index of a generation unit (VIGS) and its sensitivity (SVIGS), accurately computed using a realistic ac power flow incorporating the AGC model (AGC-PF). Transmission overloads, vulnerability indices and their sensitivities with respect to generation control are translated into fuzzy-set notations to formulate, transparently, the relationships between incremental line flows and the active power output of each controllable generator. A fuzzy-rule-based system is formed to select the best controllers, their movement and step-size, so as to minimize the overall vulnerability of the generating system while eliminating overflows. The controller performance is illustrated on the IEEE 39-bus (New England) network and the three-area IEEE-RTS96 network subjected to severe line outage contingencies. A key result is that min- imizing the proposed vulnerability metric in real-time results in increased substantial loadability (prevention) in addition to overload elimination (correction). [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
49. Worst-Case Interdiction Analysis of Large-Scale Electric Power Grids.
- Author
-
Salmeron, Javier, Wood, Kevin, and Baldick, Ross
- Subjects
ELECTRIC power ,POWER resources ,ENGINEERING ,MATHEMATICS ,FAILURE analysis ,CONSUMERS ,PERSONAL computers ,LOAD flow analysis (Electric power systems) - Abstract
This paper generalizes Benders decomposition to maximize a nonconcave objective function and uses that decomposition to solve an "electric power grid interdiction problem." Under one empirically verified assumption, the solution to this bilevel optimization problem identifies a set of components, limited by cardinality or "interdiction resource," whose destruction maximizes economic losses to customers (and can thereby guide defensive measures). The decomposition subproblem typically incorporates a set of dc optimal power-flow models that cover various states of repair after an attack, along with a load-duration curve. Test problems describe a regional power grid in the United States with approximately 5000 buses, 6000 lines, and 500 generators. Solution time on a 2-GHz personal computer is approximately one hour. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
50. Estimating the Spinning Reserve Requirements in Systems With Significant Wind Power Generation Penetration.
- Author
-
Ortega-Vazquez, Miguel A. and Kirschen, Daniel S.
- Subjects
WIND power ,RENEWABLE energy sources ,WIND power plants ,ELECTRIC power ,POWER resources ,ENGINEERING ,MATHEMATICS ,MONTE Carlo method ,NUMERICAL analysis - Abstract
Spinning reserve (SR) allows system operators to compensate for unpredictable imbalances between load and generation caused by sudden outages of generating units, errors in load forecasting or unexpected deviations by generating units from their production schedules. As the proportion of power produced by wind farms increases, it becomes more difficult to predict accurately the total amount of power injected by all generators into the power system. This added uncertainty must be taken into account when setting the requirement for SR. This paper proposes a technique to calculate the optimal amount of SR that the system operator should provide to be able to respond not only to generation outages but also to errors in the forecasts for load and wind power production. Using a Monte Carlo simulation, the proposed technique for setting the SR requirements is then compared with the traditional deterministic criterion (i.e., the capacity of the largest online infeed), an approach to cope with wind imbalances and an approach that combines the traditional criterion with the approach to cope with wind imbalances. The results show that, contrary to what is commonly believed, an increased wind power penetration does not necessarily require larger amounts of SR. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
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