Recently, the stability of power systems becomes more firm involving the extension and complication of power systems, though an unstable behavior after a serious fault is expanding from a transient area to a dynamic area. Therefor we are aiming a development of stabilizing method for dynamic stability using only local information.
In this paper, firstly we proposes a new concept of real time modeling method using only local information after a fault. The control actions to stabilize the power systems are determined using a behavior prediction based on differential equations for this model. Secondly, behavior prediction will be done based on differential equations for above on-line model. And control actions of each generator are determined based on stability judgement results at each local site.
The case studies shows the validity of the proposed method.

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To study the efficient use of the housing and photovoltaic, we constructed housing which has adequate airtightness, adequate heat insulating efficiency, and concrete floors, multi-ple window glasses for seasonal weather changes and much more safety. We built a house where tow people can live(160m²) and which needs only 4.9 kW of energy. We did data analysis while they were actually living there.
As a result, we could create a comfortable environment to live, keeping the temperature in summer between 28.5 and 30°C and the humidity 50%(moisture removal) and the temperature in winter between 22 and 24°C and the humidity 50%(moisture addition). Because over drying of the air was restricted, dew condensation was prevented. 4240 kWh out of 2940kWh (70 %) became surplus electric power and the rest (30%) was consumed for a comfortable living environment. It proved that we could save 42% of electric power expenses compared with that of general hausing (4 person household, 160m2) and that we could reduce more than 60% thecooling and heating capacity.

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In Japan, electric power utilities purchase the electricity of independent power producers (IPPs) through competitive bidding, where the evaluation of IPP is based on the avoided costs of corresponding generators of utilities. In this evaluation, however, non-pricing factors such as power flow constraints in the electric power system cannot be considered.
In this paper, we propose a new approach to evaluate economical impacts of IPP, where the electricity of IPP is priced on the basis of total generating costs of the electric power utilities. Such a price to purchase the electricity of IPP is referred to as “breakeven cost”. The main results are summarized as follows:
1) breakeven cost depends upon not only the power flow constraints in the system, but also various factors of IPP such as generating pattern, location and capacity,
2) breakeven cost for the base-type IPP is higher than the avoided cost of corresponding utility generator, because IPP located on demand sides can reduce the transmission power loss in the electric power system,
3) breakeven cost, is affected by available capacity of utility generators. especially for the peak-type IPP generating during only peak demand periods.

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This paper proposes a novel PLL and a novel frequency detecting method suited for the abnormal voltage conditions due to faults in the power system. Conventional PLL and local frequency detecting method have operation missing and dynamic error under fault conditions. On the other hand, in the power system stabilization using power electronics equipment, clever detecting method for very small frequency difference is required at local point. But, some problems exist similarly to the above mentioned problems.
In this paper, from the point of view of positive sequence component governing the power system even under the fault conditions, the PLL and the frequency detecting method responding to the positive sequence component are proposed and discussed. And then, usefulness of this method is shown by simulating its operations including power system stabilization using voltage source type power converter.
As conclusion, we can see remarkable robustness of this method. And, dynamic error and twice frequency pulsation are remarkably reduced.
Therefore, this method is expected to be applicable to power system control.

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This paper presents a method to optimize power flows in a power system by controlling a set of variable reactance units to minimize the power transmission losses. The apparatus, which are capable of flexibly changing their impedance in series such as a thyristor controlled capacitor or a phase shifter, are attractive for power system utilities since they control power flows directly and rapidly as well as they improve power system dynamics. In this paper the capability of power flow control is applied to the optimal power flow control. A method to evaluate the power flow control ability of a variable reactance unit and a method to select a necessary set of variable reactance units are formulated. The object function is approximately represented only by a summation of products of a line resistance and a square of the line power flow, which makes possible to systematically calculate the locations and the necessary amounts of variable reactance units for a given set of generation and consumption in a power system.

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Today's bulk power systems require more sophisticated operation techniques because of including semiconducter equipment etc. Especially, wide and deep consideration have been paid to a short-term stability phenomenon in the recent years. And a computing program to analyze the causal relation and the cascading process of the phenomenon comes to one of the most essential analytical tools for the stable stability operation.
The purpose of this study is to establish a practical simulation program analyzing a short term behavior of stability. The program takes combined implicit and explicit integration on the basis Of time domain simulation, and have converter model and the control system model suited for Y method. Then, compared experiment result in simulator and verificated the propriety of analysis technique

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Releasing of polluted gases such as NOx and SOx from ships to the atmosphere has been concerned increasingly. To reduce the pollution of the marine environment, the application of photovoltaic energy to ships is highly regarded, since photovoltaic energy is an alternative clean energy source to fossil fuels.
In this paper, we propose a method of basic design of the electric power system with photovoltaic system for ships. The electric power generating system with photovoltaic generating system for a small ship is designed by the proposed method. We compare generating cost, the amount of fuel consumption and NOx and SOx emission of diesel generating system with those of photovoltaic/diesel hybrid generating system. In that case, the amount of fuel consumption, NOx and SOx emission are proved that be reduced significantly by installing of the photovoltaic system.

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This paper proposes a new algorithm to obtain an approximate optimal solution for the load balancing of large-scale radial distribution system. Since the problem is formulated as a combinatorial optimization problem because of the discreteness of load section connection, it is difficult to solve a large-scale combinatorial optimization problem accurately within the reasonable computational time. So for, in order to find an approximate optimal solution quickly, the authors have published a solution method based on the network flow incremental algorithm. Although the incremental algorithm can find the optimal solution to the problem, the result is not always radial (feasible). So as to overcome this deficiency, in this paper, the authors propose a new algorithm that can find the load balanced radial distribution feeder configuration. The proposed algorithm picks up load by a unit of a section load. Therefore, the problem is elementarily a combinatorial optimization problem. However, to avoid the permutation, the algorithm employs a heuristic algorithm based on the mathematical concept of the optimality of the incremental algorithm. In picking up section load, the algorithm can take into account not only the current load balance but also the expected load which feeders should pick up afterward. To realize this algorithm, a combination of labels is introduced to each node. Through numerical examples, the validity of the proposed method is examined.

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One of the most important questions on the wheeling of electricity is how to set its service rate. We had already reported the model of setting the wheeling rate on the basis of long-run marginal cost theory, which includes capacity expansion costs both in power generation and transmission lines. Rut the model was applied only in the case where one independent power producer (IPP) sells electric power to one specific customer, and the fair allocation of wheeling costs among multiple network users was not taken into consideration in the previous paper.
In this paper, we propose a new model for allocating the wheeling costs among multiple network users on the basis of cooperate game theory, and investigate the impartial allocation of wheeling costs by comparing the results with those derived on the basis of long-run marginal cost theory. We also calculate the allocation of wheeling costs in the case where the costs of transmission lines have scale-merit, and the case where expansion of transmission capacity is treated as a discrete variable.

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This paper describes a suggestion to a control system of network voltage and reactive power. The system gives the target quantity to each installed voltage and reactive power adjustment equipment on the distribution line from control center which connected with it by the communication line of distribution automation system. We will introduce that as a software of control center for realizing of this optimum condition, we developed the control method by Genetic Argorithm (GA) and Neural Network (NN). Concretely, we will describe the outline of processing software, detailed algorithm, and verification at the model system and so on.

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A new gas turbine power generation system has been proposed, in which the steam (H₂O) produced by utilizing waste heat from factories is used as the working fluid of gas turbine. A simulation model has been constructed to estimate power generation characteristics of the proposed system by adopting C++ language. It has been shown from simulation results that the proposed system has high exergetic efficiency, that is, the total exergetic efficiency is 46.3% and fuel-based one is 56.3% for a case where the steam with temperature of 27.5 °C produced from a garbage incineration plant is used. Sensitivity analysis has also been carried out when usable steam temperature and pressure is changed, together with the case when condenser outlet pressure is changed. Characteristics of a. dual fluid gas turbine cycle power generation system (DFGT) have also been estimated in this study. It has been shown that the proposed system has 16.9% higher exergetic efficiency and 41. 8% higher fuel-base exergetic efficiency compared with DFGT.

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For a predicting method of the fuel cell life which accompanies with continuous rated operation, start/stops and load changes, we propose the Integral Method. In this method, we seek for approximate formulas of voltage changing velocity to the generating time, and we can calculate voltage drop by integrate approximate formulas for operation patterns or operating temperature. This method allows us to separate the influences of the continuous rated operation, start/stop and load changes, so it comes to estimate cell life accurately.

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We measured an electric field in transformer oil / pressboard composite insulation system under dc voltage application using Kerr electro-optic measurement system. When a pressboard was inserted between two parallel-plane electrodes, the electric field between the pressboard and the cathode decreased monotonously with time. On the other hand, the electric field between the pressboard and the anode increased with time, reached a maximum value and then fell down. In this paper, we measured an electric field at different temperature of transformer oil and discussed the mechanism by charge accumulation model and potential distribution considering the difference in charge accumulation rate on the pressboard between positive and negative charges.

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Lightning surge characteristics of a power transmission line comprising of a tower, an earth wire and phase conductors are studied with the help of the Numerical Electromagnetic Code. They are little influenced by the type of lightning, upward or downward. The transfer impedances between the current injected into the tower and the voltages of crossarms are hardly affected by the presence of an earth wire. The coupling coefficient between an earth wire and a phase conductor is much lower than that in the steady state when it is evaluated at the moment of the peak of the insulator voltage. For the traveling wave analysis, a value of 20052 is suitable as the surge impedance of a typical double-circuit tower.

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In Japan, mean annual days of thunderstorm activity (T_d) is determined based on the observation of 10 years from 1954 to 1963, for each rectangular area of about 23 km×27km. The T_d may change depending on the longterm variation of climate. In addition, only one T_d for a 23km×27km area is not enough to express the locality of lightning activities.
On the other hand, based on the analysis of lightning current measurement on 15 transmission lines in Japan, the author found that the content (%) of large current lightnings (such as larger than 80KA) is very larger in heavy lightning districts than in mild lightning districts.
Taking the above phenomenon into account, and based on the statistical analysis of field investigation data, the author set up a new theory to estimate the lightning performance of transmission lines.

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Performance of a subsonic disk CCMHD generator at part-load operation is examined with time-dependent quasi-one-dimensional numerical simulations. The part-load operation is attempted by means of the control of the thermal input (mass flow rate) to the generator under the conditions of constant inlet stagnation temperature and stagnation pressure ratio. Under the operating conditions in the wide range from the nominal value to 25% of thermal input, the subsonic generator can be operated stably, keeping high enthalpy extraction ratio of 30% and isentropic efficiency of 75% given as the nominal values. The fully ionized plasma with the electron temperature of about 5000 K can be maintained regardless the variation of the thermal input.

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There is a few data of temperature characteristics of SF₆ gas tank type surge arresters. This paper describes the relation of solar radiation in summer, tank surface temperature and leakage current of SF₆ gas insulated type surge arresters for the 1, 000kV, 500kV power systems. The temperature of internal zinc oxide elements are evaluated as about 40°C.

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To measure the accurate distance between high voltage power transmission lines and trees and to fell nearby obstructing trees are important tasks of an electric power company. An on-board eye-safe laser radar system which can accurately measure distance between these two objects has been developed. An eye-safe wavelength of the laser operating at 1.572μm was used for the safety of the human cornea. The constructed system can be mounted on the helicopter for the general tour of the inspection as it is compact, light weight, and low average dissipation. The distance on the opposite side of the flight position can be measured at the same time. This system can be applied to all grade of transmission lines(500kV_??_66kV). The distance accuracy below ±93cm was obtained.

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