In Japan, local power systems (77kV) are served from the 275kV or 154kV substations. For enhancement of power supply reliability, the transmission lines are connected to several substations, and the operational configuration is radial. The local power system's configuration is determined by connecting and disconnecting transmission lines so as to keep the radial structure and satisfy the operational constraints. When a local power system has a number of transmission lines, many configuration candidates occurs. Recently, an IEEJ committee made a practical scale local system model (IEEJ Local System Model). Since IEEJ Local System Model has 76 transmission lines, the total number of configuration candidates is 2⁷⁶(=7.5×10²² approximately). In this paper, the authors try to strictly obtain the loss-minimum configuration under constraints such as substation capacity, line capacity and radial structure in IEEJ Local System Model. In order to obtain the optimal configuration, a new computation algorithm is proposed. In the proposed algorithm, the configuration determination problem is replaced as two combinatorial optimization problems based on the operational constraints (1)substation capacity, (2)line capacity and (3)radial structure). One combinatorial optimization problem (subprobleml) is to pick up all partial configurations satisfied with line capacity and radial structure constraints. The, other one (subproblem2) is to select the partial configurations so as to minimize total line loss under the substation capacity constraint. By using the enumeration method, subprobleml is solved. Subproblem2 is solved by using the reduced ordered binary decision diagram (ROBDD). Since the proposed method is based on enumeration and Boolean function, the optimality of obtained solution is guaranteed.

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In a transmission network open access environment, an efficient comprehensive generation scheduling taking into account the transmission network will be required. This paper proposes a practical hydro-thermal unit commitment scheduling considering the transmission network.
The proposed technique consists of a multi-stage screening algorithm for processing the operation constraints and a feasible solution is obtained using a heuristic multi-stage approach. At first stage, we decide an initial schedule by relaxing various operation constrains of the thermal units and reservoir storage constrains of hydro power stations. Second stage processes the thermal unit operation constrains of the spinning reserve and minimum up and down time taking into account the hydro system operation. At final stage, we screen the violation of reservoir storage of hydraulically coupled power stations. In each stage, calculation of transmission losses using an optimal DC power flow is carried out and it is expected to realize a more detailed and realistic schedule than the conventional one in which transmission losses are ignored. The application results for a 53 buses model power system including 12 thermal units and 24 hydro power stations of 7 rivers show the effectiveness of the proposed method.

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羽田空港は2010年の再拡張により交差する4本の滑走路を同時運用する方式となった．その際，空域のから「方面別滑走路」方式が採用され，また滑走路上においても離着陸が相互従属運用となった．これらのや特性は航空機遅延に対して大きな影響を与える．本研究では，これら羽田空港の滑走路運用特性に起因した航空機遅延に関して，方面別滑走路制約の有無による遅延量変化をシミュレーション分析し，さらに数理最適化手法を応用した離着陸便数配分手法による遅延軽減方策について検討を行った．その結果，方面別滑走路制約の解消および羽田空港の処理容量特性を踏まえた離着陸便数配分の最適化による遅延軽減効果を定量的に示した．

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It is unavoidable for electric power companies to inspect and to maintain electric power facilities. Each work is generally called as an outage work due to suspending power supply to the relevant electric power facility. The power companies are expected to operate a power system retaining high power supply reliability even during outage works. Therefore, they need to make an outage work plan carefully, considering a great number of power system conditions and restrictions. Several studies in this area have been so far carried out by research organizations including power manufacture. Most of them are dedicated to obtain a feasible plan without considering power supply reliabilities because it is virtually impossible to find out the best plan with high reliability out of enormous combinations of system configurations. In this paper, the authors regard the outage work scheduling as a combinatorial problem of system configurations. We provide a framework to solve the problem and some results by numerical simulations in order to confirm the effectiveness of our study.

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This paper describes the optimization of multiple power plant maintenance based on the quantitative risk evaluation. In the plant maintenance decision, an optimal maintenance strategy is decided so that the total maintenance cost and possible default cost through the lifetime of the plants are minimized. In this calculation, the maintenance strategy should satisfy the plant operation constraints such as acceptable maintenance budget and maximum probability of plant default in every year. This problem becomes a nonlinear optimization problem defined on a high dimensional space, to which metaheuristic search method can be applied effectively. In this paper, a memetic algorithm that combines Genetic algorithm and Nelder-Mead simplex method is proposed. Through the comparison with an ad hoc method that has been used conventionally, we show that the proposed metaheuristic algorithm has an effective solution power for real-world plant maintenance problems.

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In a distribution system, in order to enhance the reliability of power supply, the distribution feeder is divided into several sections by installing sectionalizing switches, and then each of sectionalized sections is connected to different feeder. For example, one feeder is divided into three sections by two sectionalizing switches, and then each of divided sections is connected to other feeder through sectionalizing switch. Since a distribution system with many feeders has many sectionalizing switches, the system configuration is determined by states (opened or closed) of sectionalizing switches. Usually, power utility tries to obtain distribution loss-minimum configuration among large numbers of configuration candidates. However, it is very difficult to determine the loss-minimum configuration that the mathematical optimality is guaranteed, because it is well known that determination of distribution system's configuration is to decide whether each sectionalizing switch is opened or closed by solving a combinatorial optimization problem.
In this paper, the authors propose a determination method of loss minimum configuration which the mathematical optimality is guaranteed for a three sectionalized and three connected distribution feeder network. A problem to determine the loss minimum configuration is formulated as a combinatorial optimization problems with four operational constraints ((1) feeder capacity, (2) voltage limit, (3) radial structure and (4) three sectionalization). In the proposed method, after picking up all partial configurations satisfied with radial structure constraint by using enumeration method, optimal combination of partial configurations is determined under the other operational constraints by using conventional optimization method. Numerical simulations are carried out for a distribution network model with 140 sectionalizing switches in order to examine the validity of the proposed algorithm in comparison with one of conventional meta-heuristics (Tabu search).

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Voltage reactive power control (VQC) on power systems becomes difficult when a load increases or decreases rapidly, especially in the morning and at noon. This is caused mainly by two problems. One is delayed operation and the other is noncooperative operation of facilities. To solve these problems, an advanced method for a centralized feed-forwarding control system and algorithms are pre-sented. They are based on two main steps, forecasting power system state for several minutes and dispatching reactive power sources optimally based on stepwise linear programming. The proposed method is evaluated and tested for data of a large scale power system. Results show that the proposed method keeps the voltage constraints well and reduces redundant operation of facilities.

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In the previously reported hydrothermal scheduling methods, emphasis is placed on the hydro scheduling and the thermal system is simply represented by a single equivalent unit which generates an economic schedule.
This paper presents a more detailed (thermal unit commitment involved) and efficient weekly power generation scheduling method of hydrothermal systems with pumped-storage plant. As the pumped-storage operation has a great influence on the unit commitment schedule, using power system's incremental fuel cost and unit's average fuel cost per kWh, firstly, the pumped-storage schedule is integrated into the thermal unit commitment schedule and then, optimal multireservoir hydro operation can be scheduled efficiently by the aggregation-decomposition method.
The effectiveness of the proposed method is ascertained through many simulations for a model system using a personal computer and due to its easiness of handling various constraints and an efficient calculation algorithm, it is considered to be a practical method for the large scale hydrothermal systems.

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This paper presents a novel method for optimal scheduling of hydraulically coupled power plants with operation constraints.
In a hydro thermal power system, the operation schedule of hydro plants becomes more important to reduce the fuel cost of thermal plants, as the ratio of the hydro plants becomes larger. But hydraulically coupled power plants have some specific constraints depending upon the operations of the upstream plants, which makes the optimization problem more complicated.
The proposed method is based on a decision process of an expert operation planner. First it calculates the most economical operation schedule without respect to the operation constraints of hydraulically coupled power plants. If this initial schedule violates the operation constraints of hydraulically coupled power plants, it is modified successively so as to dissolve each violation with most economical manner.
The method is heuristic, but it can be widely applied to general problems as specify the river systems characteristics.
Due to the above-mentioned method, the obtained schedule becomes easily acceptable because the intermediate schedules can be checked by the operation planners.

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This paper presents a method for obtaining preventive control strategies based on non-linear optimization for power systems which will incur voltage instability when load demand increases. The purpose of this algorithm is to determine an appropriate and effective control action taking into account the operating constraints, in order to widen the margin between the present operating point and a voltage collapse point, hence improving the system state. The method proposed here is based on a complex-valued load-flow technique using the Newton-Raphson method which has been already developed by the authors. Consequently, the preventive control algorithm also can evaluate the voltage instability for the case that the present operating point becomes closer to the critical point and system state becomes unfeasible at increased loading point. And in optimization, two-types of objective function are introduced so that voltage stabilization and dissolution of constraint violation can be attained simultaneously. In addition, this paper discusses the extension of the proposed preventive control to the successive control method which carries out the control action for avoiding voltage collapse while the load demand is increasing. Numerical examples for various model systems demonstrate the effectiveness of the proposed method.

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This paper presents an optimal weekly scheduling method for the complicated hydrothermal systems which involve not only hydraulically coupled multi-chain, multi-reservoir hydro systems, but also pumped-storage plants together with thermal units.
The basic approach of the proposed method adopts an iterative optimization algorithm of scheduling each operation of hydro, thermal and pumped-storage systems sequentially. An efficient aggregation-decomposition algorithm for the multi-reservoir hydro scheduling is developed. That is, to get an efficient scheduling method, hydroelectric plants along a river are aggregated into one equivalent hydro plant and then, this plant is decomposed again to each original plant through a matrix screening method so that constraints satisfied optimal solution is realized. Simulation results show that the proposed method has enough efficiency for practical use in terms of convergence characteristic and computing time.

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In the field of electrical power system, various approaches, such as utilization of renewable energy, loss reduction, and so on, have been taken to reduce CO₂ emission. So as to work toward this goal, the total number of distributed generators (DGs) using renewable energy connected into 6.6kV distribution system has been increasing rapidly. The DGs can reduce distribution loss by appropriate allocation. However, when a fault occurs such as distribution line fault and bank fault, DGs connecting outage sections are disconnected simultaneously. Since the simultaneous disconnection of DGs influences restoration configuration and normal configuration after the restoration, it is necessary to determine the system configuration in normal state considering simultaneous disconnection of DGs.
In this paper, the authors propose a computation method to determine the loss minimum configuration in normal state considering reconnection of DGs after simultaneous disconnection by fault occurrence. The feature of determined loss minimum configuration is satisfying with operational constraints even if all DGs are disconnected from the system. Numerical simulations are carried out for a real scale distribution system model with 252 sectionalizing switches (configuration candidates are 2²⁵²) and 120 DGs (total output is 38.46MW which is 23% of total load) in order to examine the validity of the proposed algorithm.

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Modern power system has become large and complex networks, which require more flexible system operation. Voltage and reactive power control (VQC) that transports more electric powers especially maintaining voltages within range of constraints is expected to become more important for a high-performance system operation. In this paper, we propose a new technique of VQC considering load change with a short-term load forecasting and an optimal control by a new Meta-heuristics technique with combination of Particle Swarm Optimization (PSO) and Tabu Search (TS).

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The economic load dispatching (ELD) among thermal units can be formulated as one of the constrained optimization problems in power system operation. Since an optimization is required under severe constraints, all constraints cannot be taken into account. Therefore, at present stage, an automation is performed considering several constraints and, for the time interval where some constraints are not satisfied, a manual operation is performed for ELD based on the empirical knowledge of operators.
This paper presents an application of artificial neural network to ELD. The method uses one of the probabilistic neuron model, called Gaussian Machine and several constraints are handled by heuristic methods. The method can solve a local minimum problem, initial condition problem of neurons, and parameter tuning problem.
In this paper, parallel processors are used for inplementation of the system. The processors are high performance microprocessors that support parallel processing through on-chip hardware. The number of processors is examined for detecting appropriate parallel computation

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In the field of electrical power system, various approaches, such as utilization of renewable energy, loss reduction, and so on, have been taken to reduce CO₂ emission. So as to work toward this goal, the total number of distributed generators (DGs) using renewable energy connected into 6.6kV distribution system has been increasing rapidly. However, when a fault occurs such as distribution line faults and bank faults, DGs connecting outage sections are disconnected simultaneously. Since the output of DGs influences feeder current and node voltage of distribution system, it is necessary to determine the optimal system configuration considering simultaneous disconnection and reconnection of DGs.
In this paper, the authors propose a computation method to determine the optimal restoration configuration considering many connections of DGs. The feature of determined restoration configurations is prevention of the violation of operational constraints by disconnection and reconnection of DGs. Numerical simulations are carried out for a real scale distribution system model with 4 distribution substations, 72 distribution feeders, 252 sectionalizing switches (configuration candidates are 2²⁵²) and 23.2MW DGs (which is 14% of total load) in order to examine the validity of the proposed algorithm.

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Ship's handling is difficult because the response of ship's maneuver is slow with the big inertia. First, this study identifies the ship's maneuverability, which is expressed as Auto-Regressive Moving Average (ARMA) model, by steering. Second, a time delay of the angular velocity is verified. Finally, this study design a ship's steering control system. The angular velocity is controlled by applying Generalized Minimum Variance Control (GMVC) of predictive control method. Especially, GMVC's control method is arranged by adding a operating limit for the ship's steering control.

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NHTSA-ODD分類に基づきJASPAR-ODDを定義した上で，ADSレベル3の分散開発で共有及び参照するための基本アーキテクチャを定義する．システムモデルはSysMLを用いてADS基本アーキテクチャを構築し，SOTIF範囲内外の危険シナリオを分析して未知の危険領域を最小化する安全要求を導出する．

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Recently, photovoltaic generation (PV) attracts great attentions as a countermeasure against the global warming and the depletion problem of fossil energy resources in the world. However, it is known that a PV output fluctuates due to the insolation variation. Unstable power from a PV power station may cause some negative impact to the power system. Therefore, to utilize a PV power station in substitution for an existing power supply, improvement in controllability and adjustability of generation output is very important factor. In this paper, a new method for scheduling and rescheduling the PV power station output based on the solar radiation forecast are proposed. The scheduling and rescheduling method using NAS battery and solar radiation forecast from the economic perspective are proposed and the validity of the proposed method is ascertained through case studies using the data measured in the Wakkanai PV power station.

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