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Hiroshi Sasaki
2001 Volume 121 Issue 2 Pages
159
Published: February 01, 2001
Released on J-STAGE: December 19, 2008
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Masakazu Kato
2001 Volume 121 Issue 2 Pages
160-163
Published: February 01, 2001
Released on J-STAGE: December 19, 2008
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Keiichiro Yasuda, Mitsuaki Tsunematsu, Takao Watanabe
2001 Volume 121 Issue 2 Pages
164-171
Published: February 01, 2001
Released on J-STAGE: December 19, 2008
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In recent years, the trend has been toward factors (demand for load, energy cost, etc.) becoming more and more uncertain in power system expansion planning. So it has become necessary to take this uncertainty into account in determining generation plans. In this paper, a robust generation plan is defined explicitly as a plan that assures fixed performance (economy) despite deviations in these factors. In addition, a new formulation of the robust generation mix problem, whose purpose is to determine the most robust combination of plants in a target year, is proposed. It is generally difficult to solve the formulated problem with parameters. However, by analyzing a proposed formulation from the viewpoint of optimization, we show that the proposed formulation is transformed into the conventional optimization problem without parameters. The simulation results on a typical model show that the generation mix produced by the proposed formulation is more robust than that produced by the conventional formulation.
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Yasuhiro Hayashi, Junya Matsuki, Koichi Nara
2001 Volume 121 Issue 2 Pages
172-178
Published: February 01, 2001
Released on J-STAGE: December 19, 2008
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Secondary power systems (66kV) with radial system structures are served from the 275kV or 154kV substations. For enhancement of power supply reliability, the transmission line is connected to another substation. However, when the radial power system has a number of connected feeders, the combinatorial number of possible system structures by switching CBs becomes very large. In this paper, a new solution method to determine the optimal secondary power system configuration is proposed. In the proposed method, the determination problem of the optimal system structure is treated as a minimum spanning tree problem with constraints, and then it is solved by using reduced ordered binary decision diagram (ROBDD). Since the proposed method is based on Boolean function, the optimality of obtained solution is guaranteed. In order to check the validity of the proposed method, numerical simulations are carried out for system models, and the results obtained by branch and bound method are compared with these of proposed method.
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Takeshi Nagata, Hideki Watanabe, Masumi Ohno, Nobuhiko Iba
2001 Volume 121 Issue 2 Pages
179-185
Published: February 01, 2001
Released on J-STAGE: December 19, 2008
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This paper proposes a multi-agent system to power system restoration problems. Multi-agent is a new paradigm for developing software applications. Coordinating the behavior of autonomous agents is a key issue in agent oriented programming techniques today. Recently, agents are being used in a increasingly wide variety of applications, ranging from comparatively small systems such as E-mail filters to large, open, complex systems such as air traffic control. Though some agent frameworks have been proposed in the power system field, the number of studies is limited.
In this paper, we developed a power system restoration application by multi-agent architecture. Our multi-agent system has the following characteristics: (1) The system consists of a single facilitator agent, and one or more bus-agents which are elements of power system network. (2) The facilitator agent is developed to act as a manager for the process by using the singleton design pattern. The bus-agents have simple negotiation strategies. (3) Message object is developed to communicate between the agents using KQML-like object. The proposed approach is applied to a simple network, and the results show that the multi-agent system is an efficient and robust approach for solving power system restoration problems.
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Akinori Miyata
2001 Volume 121 Issue 2 Pages
186-193
Published: February 01, 2001
Released on J-STAGE: December 19, 2008
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This paper presents the outline of an optimization program of renewal plans for aged thermal power stations. The program includes technological development of new facilities represented by diminishing construction cost and increasing thermal efficiency as linear functions. It also can include large concentrated repair work maintenance expenditures as well as linear function type ones. It evaluatesthe economic and electro-technical differences of acquiring new sites remote from demand centers against utilizing existing sites with valuable infrastructures.
Examples of application for aged 175, 350, 600MW plants are shown. The study results show that smaller size existing units which can be replaced with advanced combined cycle units with comparatively large output can produce favorable results for promotion of renewal when the ratio of the output after and before renewal is about twice or more.
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Hideyasu Hokazono, Michio Suwa, Shinichi Iwamoto, Eiji Hashimoto
2001 Volume 121 Issue 2 Pages
194-200
Published: February 01, 2001
Released on J-STAGE: December 19, 2008
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Semiconductor application equipment has been widely used by rapid advance of thepower electronics technology, and the voltage distortions in power systems have increased and, therefore, the harmonics have become problems recently. As for the equipment that has semiconductor applications, it is possible that the use would be increased in the future, and the harmonics troubles would be increased correspondingly. In order to solve the problems, this paper proposes an optimal filter allocation method using a nonlinear programming technique. Simulations results are given for 6 and 20 bus systems to illustrate and verify the proposed method.
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Kenji Yoshimura, Naoyuki Uchida, Toshiyuki Okada
2001 Volume 121 Issue 2 Pages
201-209
Published: February 01, 2001
Released on J-STAGE: December 19, 2008
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We have developed new design methods for generator's excitation controller. The methods can improve damping and synchronizing torque to rise power transfer capability. The power transfer capability is evaluated in a one-machine connected infinite bus system and a multi-machine power system model.
(1) Development of a new optimization method for parameters of AVR and PSS: The method can improve both of damping power and synchronizing power based on eigenvalue sensitivity technique. Applying this method to 18-generator system model, the power transfer capability increases by 7% larger than a conventional method.
(2) Development of a new excitation system with a remote bus voltage as AVR input signal: Increasing of stabilized generator capacity, the power transfer capability expands much higher however its effect is saturated due to bus voltage instability. Introducing a remote signal of the bus voltage into the generator's exciter in addition to a conventional terminal voltage, the power transfer capability grows up to 63%.
(3) Comprehensive controller design scheme for practical use is proposed to enhance both of steady state stability and transient stability.
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Hajime Nishi
2001 Volume 121 Issue 2 Pages
210-216
Published: February 01, 2001
Released on J-STAGE: December 19, 2008
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This paper proposes a method to calculate the steady state stability limit in the two synchronus machines connected to an infinite bus system from only two power equations; namely, the simultaneous power equa-tions show critical points of a potential function in the two variables. Considering that the two equations represent a vector field, one differential equation is derived as a solution when a functional relation between the two transformed variables is assumed. This differential equation is an infinite series of the one variable. If the theory of catastrophy is applied to the function which is obtained by integrating the differential equa-tion, a bifurcation set can be obtained.
Elmination of the fixed points from the obtained equation and the simultaneous equations to calculate the fixed points leads to the expression for the steady state stability limit curve (represented by P
1, P
2).
This curve is considerably swayed by the change of the nominal induced voltage, but if the quadrature-axis fluxes φ
q1 and φ
q2 are used, a new curve can be freed from the effect of the nominal induced voltage.
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Masaru IGUCHI, Koichi NAKAMURA, Susumu YAMASHIRO
2001 Volume 121 Issue 2 Pages
217-223
Published: February 01, 2001
Released on J-STAGE: December 19, 2008
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In recent year, under the deregulation of power industry, the independent power producers (IPP) have been entering into the power generation sector and the number of IPP will increase more and more in the future. In this circumstance, we must consider the issue of how to estimate and to secure the reliability of a power system under uncertainty. Therefore, the unit commitment schedule with an appropriate spinning reserve taking into account uncertainties will be a key subject in the economic estimation of power system operation.
In this paper, we report a solution technique with a new objective function for the unit commitment problem considering a power interruption cost which is expected to be able to evaluate the reliability in term of economy. In the proposed algorithm, the decision space is separated into two phases, a virtual scenario part in which the generator outage and the demand forecasting error are included, and an actual unit commitment part. An optimization algorithm of a stochastic approach using this decision space is developed and numerical results indicate that the value of the objective function can be reduced significantly compared with the deterministic model.
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Junyong Wu, Akihiko Yokoyama, Qiang Lu, Masuo Goto, Hiroo Konishi
2001 Volume 121 Issue 2 Pages
224-233
Published: February 01, 2001
Released on J-STAGE: December 19, 2008
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In this paper, deoentralized feedback linearizing excitation and governor control, a kind of decentralized nonlinear control, in multi-machine power system is proposed to improve transient stability, and a local observation algorithm of the postfault equilibrium is also explored. Simulation results show that, it can improve the transient stability of the multi-machine power system to a great extent and enlarge the stable operating region even comparing to the decentralized feedback linearizing excitation control, and its adaptive ability to the changing postfault operating conditions is also verifiod.
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Hiroyuki Mori, Noriyuki Kosemura
2001 Volume 121 Issue 2 Pages
234-241
Published: February 01, 2001
Released on J-STAGE: December 19, 2008
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This paper proposes a method for daily maximum load forecasting in power systems. It is based on the integration of the regression tree and the artificial neural network. In this paper, the regression tree is used to extract knowledge or rules as a data-mining method. That is useful for the information processing of the complicated data. As a result, the proposed method has an advantage to clarify the cause and effect of dynamic load behavior in load forecasting. However, the regression tree does not necessarily give good prediction results in spite of good classification. Therefore, this paper proposes a method for combining the classification results of the regression tree with the multi-layer perceptron of a universal nonlinear approximator. The effectiveness of the proposed method is demonstrated in real data.
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Yasuji Hongo, Koji Michishita, Masaru Ishii
2001 Volume 121 Issue 2 Pages
242-249
Published: February 01, 2001
Released on J-STAGE: December 19, 2008
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Induction by a vertical lightning channel on an overhead wire over lossy ground is calculated in accordance with Agrawal's model, and the effect of pole-type distribution transformers on the induced voltage waveform is studied.
A transformer decreases the induced voltage and at the same time it increases the rise time of the voltage waveform. As far as the induced voltage waveforms on a medium voltage line are concerned, a transformer can be represented by its capacitive component only in most of the cases. Resonance of a transformer, usually its frequencies being higher than 1MHz, influences the induced voltage waveforms in cases that transformers or surge arresters are connected with an interval of less than 100m and that the rise time of a return stroke current waveform is much shorter than 1μs.
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Hironari Taniguchi, Kenji Otani, Kosuke Kurokawa
2001 Volume 121 Issue 2 Pages
250-255
Published: February 01, 2001
Released on J-STAGE: December 19, 2008
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The knowledge of the available solar irradiation at the earth's surface is essential for any type of solar power systems in terms of their design, site selection, and performance analysis. However, the irradiation observer networks at ground level are not enough to obtain the reliable information of the solar energy distribution in the world. On the other hands, Geostationary Meteorological Satellites (GMS) provides the images of cloud fields over the whole surface of the Earth. An irregular change in the irradiation at the ground level caused mainly by the effect of the clouds. Therefore, the methods of estimating the solar irradiation by using the GMS images become very useful. This paper describes the methods for forecasting solar irradiance by using GMS images. As the first attempt, the authors forecasted the cloud albedo by a basic study of irradiance estimating driving drift vector of clouds using GMS images. A new procedure is also proposed to remove the effect of ground albedo, which disturbs the cloud movement analysis. Annual forecast probability was estimated as 66. 8% for one hour ahead, 58.5% for two hours ahead and 52.7% for three hours ahead at 20 sites.
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Naoki Itamoto, Takeo Wakai, Tsutomu Sakai, Masaru Ishii
2001 Volume 121 Issue 2 Pages
256-261
Published: February 01, 2001
Released on J-STAGE: December 19, 2008
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The authors have tested 154kV-class transmission line arresters by installing them on an instrumented tower of a double circuit test transmission line during winter seasons since 1993. The tower is struck by natural and artificially-triggered lightning several times during each winter season. First, the authors verified the conventional transmission line arrester designed against summer lightning was effective against winter lightning. Next, the authors investigated its applicability against winter lightning based on EMTP analysis taking account of observed lightning current waveforms in winter, and developed a new transmission line arrester of reduced rating. The new arrester of reduced rating was tested on the test line and showed no damages in appearance and in characteristics by the inspection after field test. The new arrester for 154kV line will perform well against winter lightning when the tower footing resistance is 30Ω or less.
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Minwon Park, Kenji Matsuura, Masakazu Michihira
2001 Volume 121 Issue 2 Pages
262-263
Published: February 01, 2001
Released on J-STAGE: December 19, 2008
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In PV power generation system there need huge system apparatuses in order to verify the effect of system efficiency and stability considering the size of solar panel, the sort of converter type, and the load condition. And also, under the same weather and load condition it is almost impossible to compare with a certain MPPT control scheme and others. In this paper, in order to bring the mentioned above to a settlement, first of all, a solar cell is simulated with VI characteristics equation of solar cell, and the real field data of weather condition is interfaced to EMTDC program using Fortran program interface method. As results, comparing with the real data of PV panel and the simulated data, we obtained hopeful answers and made the simulation of PV power generation system much closer to reality possible.
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Junji Tamura, Toshiyuki Nagano, Masahiro Ueno
2001 Volume 121 Issue 2 Pages
264-265
Published: February 01, 2001
Released on J-STAGE: December 19, 2008
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This paper presents a new method to express the slack-bus in the unbalanced power flow calculation based on the phase coordinate method. Although the slack-bus is expressed, in general, as a three phase symmetrical voltage source in unbalanced power flow calculations, this expression results an incorrect solution when a generator with finite rating is connected to the slack-bus. This paper proposes a new method in which the slack-bus is expressed as a quasi P-V specified node.
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