The paper deals with the current state and future prospect of applications of elliptic function to the electric power and energy field. In particular, practical use of conformal mapping technology by elliptic function are introduced for electric power cables.
Returning to Riemann's basic principle “thinking instead of calculation”, against the main current of numerical calculation, we have a new understanding of elliptic function analysis for the usefulness and the beautiful with simplicity and elegance.

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Since land of Japan is narrow, it is advantageous to enlarge the transmission capacity per one route in terms of environmental aspect and cost performance. Therefore, technological development, such as multiple transmission line, large size conductor, multiple conductors, high strength insulator and so on, has been promoted. Especially, the adoption of 1000kV transmission line is the final configuration of high voltage system, and it is the dream for overhead transmission line engineer. So, we intervened the engineer who engaged in the conceptual design of 1000kV transmission line in initial stage on the development situation at that time. It is considered that the method of solving the problems is useful for present engineer.

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This paper presents a case-based reasoning (CBR) technique, a novel approach for voltage security assessment and optimal load shedding in real-time environment. The CBR extracts the information of voltage security from large sets of possible operating conditions of the power system, which are screened off-line by randomly varying the real and reactive loads at PQ buses. The severity of contingency is then assessed by the number of insecure operating states, which are predicted by the CBR system under that contingency. Security classes are defined by threshold value of maximum loadability margins (MLM), calculated using continuation power flow (CPF) method. For insecure states, the presented technique also gives optimal load shedding plan to bring the system from insecure to secure region. Decision trees (DT) are used for case indexing to reduce the search time to obtain the set of relevant cases, which are in thousands of numbers. In addition, decision trees also provide the information about those case features, which mostly influence the severity of a given contingency of the power system. Unlike other non-deterministic approaches, the proposed method is easy to understand for operators, easy to modify under the change of topology of the power system and has continuous learning capability. The effectiveness of the proposed approach is tested on IEEE test systems. The proposed CBR approach provides a fast and accurate voltage security assessment for unknown load patterns and a load shedding plan for insecure cases to mitigate the voltage collapse. Hence it found to be suitable for on-line applications of energy management systems.

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In recent years, distributed generation is emerging as a new alternative for power generation at a smaller but distributed scale. The output of distributed generators (DGs) mainly depends on weather condition. On the other hand, the electric utility industry worldwide has been facing pressure to be deregulated. The power flow in the electric power market will uncertainly vary with several power transactions. Therefore, complex power flow by DGs or transactions will cause the voltage deviation.
In this paper, to avoid these undesirable phenomena we propose a new multi-agent method for cooperative voltage control. The simulation results show that the proposed multi-agent method performs better than a conventional control method.

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In power systems the proper voltage ranges are predetermined in the individual voltage classes. In order to maintain the proper voltage ranges, we propose the voltage stability index VMPI (Voltage Margin Proximity Index) in this paper which defines voltage stability from the point of view of voltage magnitude limits. Many conventional papers dealing with voltage stability preventive control use control devices which take continuous values e.g. static var compensators, whereas actual power systems mainly utilize voltage control devices which take discrete values.
Hence, in this paper, we propose a voltage stability preventive control using VMPI sensitivities in order to control devices which take discrete values. We generally require speed for preventive controls in order to use it on-line, however VMPI takes time due to running optimal power flow calculations. Consequently, we propose a practical voltage stability preventive control using the calculation with initial estimates of control devices and estimation of VMPI sensitivities, which require less calculation time. Simulations are run using the IEEJ west 30 machine 115 bus system to verify the effectiveness of the proposed method.

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This paper presents a new method of unbalanced load flow calculation to improve complexity by the method of advanced symmetrical coordinates. Usually, the electric power system has been calculated only by positive phase sequence component on the assumption that three phase transmission lines and loads are balanced. However, many ultra high voltage transmission lines are not transposed, therefore mutual inductances cause negative sequence current in trunk transmission system. Negative sequence current causes the heating of the generators and transformers. Therefore, the three phase sequence component should be calculated accurately.
We examined fast computation and good convergence performance of unbalanced load flow calculation by the models of three phase transmission lines, transformers and loads. The proposed method is not the phase coordinate system but the method of symmetrical coordinates. This technique decreases numerical complexity by the use of simplified jacobian matrix. The convergence performance of this method is inferior to usual Newton-Raphson method. In consequence, the problem of poor convergence performance is improved by the technique for newly developed deceleration Newton method.

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In this paper, a new method of estimating critical generation margin (CGM) in power systems is proposed from the viewpoint of transient stability diagnostic. The proposed method has the capability to directly compute the stability limit output for a given contingency based on transient energy function method (TEF). Since CGM can be directly obtained by the limit output using estimated P-θ curves and is easy to understand, it is more useful rather than conventional critical clearing time (CCT) of energy function method. The proposed method can also estimate CGM as its negative value that means unstable in present load profile, then negative CGM can be directly utilized as generator output restriction.
The proposed method is verified its accuracy and fast solution ability by applying to simple 3-machine model and IEEJ EAST10-machine standard model. Furthermore the useful application to severity ranking of transient stability for a lot of contingency cases is discussed by using CGM.

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This paper presents a new adaptive evolutionary algorithm (AEA) by integrating genetic algorithm (GA) and evolution strategy (ES) to solve the economic dispatch with piecewise quadratic cost functions and prohibited operating zones. AEA consists of GA for a global search capability and ES for a local search in an adaptive manner when the present generation evolves into the next generation. AEA is algorithm that ratio of population of GA and ES is adaptively modified in reproduction according to the fitness. Numerical results show that the proposed method is more effective than other previously developed methods and it can be applied successfully in problems with nonconvex functions.

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In the current wind turbine generation system, there are substantial problems such as the maximum power of the wind turbine cannot be obtained under the fluctuating wind speed, high in cost and low in annual net electricity production (due to mismatch between a generator and a wind turbine). A new wind turbine generator optimized for the wind turbine output is presented in order to solve such problems. This wind turbine generator consists of a permanent magnet generator, a reactor and a rectifier, and uses neither a control circuit which requires standby electricity nor a PWM converter having a switching element. By selecting most appropriate combination of the permanent magnet generator having multiple windings and the reactor connected in series with each winding, the maximum output of the wind turbine can be obtained without using a control circuit. The new wind turbine generator was directly coupled with the straight wing non-articulated vertical axis wind turbine (SW-VAWT), and matching of the generator with the wind turbine was examined through field tests. From the test result and review, it has been confirmed that the new wind turbine generator is highly matched with the wind turbine under the fluctuating wind speed.

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In this paper Eigenvalue estimation method for small signal stability analysis of the electric power systems is proposed. The developed method is named Mode Coupling Method which is the method for estimating the non-linear change of the eigenvalue for the change of parameter, efficiently. The eigenvalue sensitivity analysis method, which has been used to estimate the change of the eigenvalue, is a linear estimation of the change of the eigenvalue. However, the eigenvalue shows a strong nonlinear change frequently. Therefore, the calculating efficiency and the calculating speed were insufficient by the conventional method. In the Mode Coupling Method, at first, it selects the important and most related modes with the major mode for that we pay attention. Next, these two or more selected modes are coupled and a new eigenvalues of the coupled matrix are calculated, those are good estimation of new eigenvalues. The size of the coupled matrix is very small. We can consider mutual interaction between important modes. As a result, it is a powerful method in which nonlinear estimation of the eigenvalue is possible. When QR method is used, the calculation time which is required for eigenvalue analysis, is proportional to the third power of the size of the matrix. The size of the matrix which is used for Mode Coupling Method, is approximately 1/6 of the origin. Therefore, the computing time for eigenvalues estimation becomes less than 1% of computing time of the origin. Concerning the computing accuracy of the proposed method, verification was done with IEEJ standard power system model EAST30.

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Proton exchange membrane fuel cell (PEMFC) can hardly react a hundred percent of fuel, because a cell potential becomes zero if all of the fuel is consumed at PEMFC. Therefore a small amount of fuel is always released from PEMFC. The exhausted H₂ should be treated for safety. i_ave-V_cel characteristics were measured changing hydrogen concentration from 99.99% to 1%. Moreover, V_cell of the constant voltage control was selected from the measured V_cell-i_ave characteristics, the low concentration hydrogen could be treated under V_cell =0.15 - 0.3V by hydrogen pump and V_cell =0.4 - 0.6V by PEMFC. The exhaust hydrogen was reduced to the hydrogen concentration of several tens of ppm.

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A study was conducted to establish a method for measuring the position and amount of leak current increase during operation of the cell. This measurement method was applied to the load fluctuation test under low humidification and leak current increase was observed on the down stream of the cell. Tested cell was disassembled and cross sections were observed under SEM. SEM images revealed the formation of the Pt band near the cathode catalyst of the down stream of the cell. This may be the cause of the degradation of the membrane at the downstream.

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Using a high temperature superconductor, we constructed and tested a model Superconducting Fault Current Limiter (SFCL). SFCL we proposed has a vacuum interrupter with electromagnetic repulsion mechanism. We set out to construct high voltage class SFCL. We produced the electromagnetic repulsion switch equipped with a 24kV vacuum interrupter (VI). There are problems that opening speed becomes late, because the larger vacuum interrupter needs the heavier weight of its contact. For this reason, the current which flows in a superconductor may be unable to be interrupted within a half cycles of current. In order to solve this problem, it is necessary to change the design of the coil connected in parallel and to strengthen the electromagnetic repulsion force at the time of opening the vacuum interrupter. Then, the design of the coil was changed, and in order to examine whether the problem is solvable, the current limiting test was conduced. We carried out a current limiting test using second generation (2G) HTS wire. The element which is used in this experiment has stainless steel stabilizer both side of the wire. As a result, we succeed in interrupting the current of a superconductor within a half cycle.

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This paper presents a new nonintrusive appliance load monitoring technique based on the integer programming. Nonintrusive appliance load monitoring is a problem to identify the operating conditions of the electric appliances in a house only by observing the overall load current and voltage. Since the overall load current is expressed as a superposition of each current of the operating appliance, the monitoring problem can be formulated as an integer quadratic programming problem by expressing the operating conditions as integer variables. This problem is solvable with sufficiently small computational burden thanks to the recent development of the commercial software. The proposed method does not require the relearning even when a new appliance is installed in the house. Furthermore, the proposed formulation is applicable to cases that some appliance has multiple modes, and cases that some same-type appliances operate simultaneously. Usefulness of the proposed technique is verified through some experimental results.

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Transient current distribution within the grounding system for a wind-turbine-generation tower of height 61m struck by lightning has been calculated using the finite-difference time-domain (FDTD) method. The grounding grid for the lightning-struck tower considered in this paper is connected electrically via an insulated wire to one neighboring-tower grounding grid located 50m away from it. High-frequency components of a lightning current tend to flow in ground through the grounding grid of the lightning-struck tower, and they become larger with increasing the ground conductivity. Relatively-lower-frequency components of the lightning current flow in ground through each of the two grounding grids roughly in inverse proportion to the grounding resistance of each grid. For example, when two identical grounding grids for the lightning-struck tower and the neighboring tower are buried in the same ground, about 50% of the lightning current flows in the grounding grid for the neighboring tower via the insulated wire connecting these two grounding grids. When the grounding resistance of the neighboring tower is about 1/4 of that for the lightning-struck tower, about 4/5 of the lightning current flows in the neighboring-tower grounding grid. This agrees well with the trend shown by Nagaoka et al. from their measurement in the grounding system for an actual wind-turbine-generation tower struck by natural lightning.

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Time dependent r-z two-dimensional numerical simulations with LES technique have been carried out in order to clarify the plasma fluid behavior and power generation characteristics of the disk MHD generator under the rated operation conditions demonstrated in the closed loop experimental facility at Tokyo Tech. The generator currently installed could suffer from the non-uniform and low electrical conductivity, and the boundary layer separation even under the rated operation conditions. The large amount of generated electric power is consumed in the boundary layer separation region, which reduces a net output power. Reducing the back pressure and improving the inlet plasma conditions surely provide the higher generator performance. The influence of 90 degree bend downstream duct on the generator performance is found to be not marked.

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Global warming caused by CO₂ etc. is a field where the concern is very high. Especially, automobile emissions are problem for it. Therefore, the hybrid car is widely development and used recently. Hybrid car used electric power and gasoline. So, the car reduces CO₂. Hybrid car has engine and motor. To rotate the motor, hybrid car has battery. This battery is large capacity. Therefore, the relay should interrupt high DC current for the switch of the motor and the engine. So, hybrid car used hydrogen gas filling relay We studied interruption test for the research of a basic characteristic of hydrogen gas. DC current has not current zero point. So, it is necessary to make the current zero by high arc voltage and forcible current zero point. The loss coefficient and arc voltage of hydrogen is high. Therefore, we studied interruption test for used high arc voltage. We studied interruption test and dielectric breakdown test of air, pure Hydrogen, and Hydrogen- nitrogen mixture gas. As a result, we realized H₂-N₂(80%-20%) is the best gas.

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