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AbstractThe spread of wind power generation has progressed hugely in recent years from the viewpoint of environmental problems including global warming. Though wind power is considered as a very prospective energy source, wind power fluctuation due to the random fluctuation of wind speed has still created some problems. Therefore, research has been performed on how to smooth the wind power fluctuation. This paper proposes Energy Capacitor System (ECS) for the smoothing of wind power which consists of Electric Double‐Layer Capacitor (EDLC) and power electronics devices and works as an electric power storage system. Moreover, hydrogen has received much attention in recent years from the viewpoint of the problem of exhaustion of fossil fuel. Therefore, it is also proposed that a hydrogen generator be installed at the wind farm to generate hydrogen. In this paper, the effectiveness of the proposed system is verified by simulation analyses using PSCAD/EMTDC. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 168(3): 10–18, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20864

AbstractOn‐line monitoring of voltage‐stability conditions is a new requirement for the energy management systems of the electric power industry. Preferred by the utility engineers and dispatchers is an index which represents explicitly the margins to a voltage‐stability limit (collapse point) expressed in a physical unit ordinarily used. For example, such indices are the system load and voltage‐voltage‐stability‐margins (SVVSM) between the present operating point and a voltage collapse point. However, long computer time is required to calculate accurately the voltage collapse point by the conventional method because many multiple load‐flow solutions are required.This paper presents a new algorithm to calculate directly, exactly, and rapidly the voltage‐stability limit. The algorithm uses the load‐flow equations and the explicit expressions of the voltage collapse root conditions are expressed as dR/dV = 0, where R is active or reactive power node injection, and modifying the conventional N‐R load‐flow program, and is not affected numerically by singular Jacobians. The proposed algorithm is verified through calculating the voltage stability limit of a 176‐node power system.

Reliability of the information transmission system and the information processing system has a great effect on the reliability of the centralized supervisory control system in power systems. The reliability of the centralized supervisory control system in terms of the expected information loss and the mean time between system failures (MTSF) has been discussed previously. Here a reliability design method of the centralized supervisory control system using these two reliability indices is proposed considering the following two problems: assigning redundancy so as to minimize the expected information loss subject to cost constraints; and assigning redundancy so as to minimize the cost subject to MTSF constraints. The two problems are formulated to a 0 to 1 type integer linear program. Numerical examples are given. It is shown that the number of constraints and the number of variables can be reduced greatly by limiting the extent of redundancy to duplication. The results obtained by the two algorithms coincide with each other.

AbstractResults of numerical study on performance of closed loop in the CCMHD single power generation system are presented. The small closed loop with thermal input of 2.3 MW was designed. The fluid‐dynamical and thermal performance of the closed loop was calculated for the first time by one‐dimensional numerical simulation. The result indicates that pressure loss and heat loss are large in the designed small closed loop. The large pressure loss was due to the wall friction or the pebble bed and it occurred at the supersonic nozzle, the MHD channel, and the regenerative heat exchanger used for argon cooling. The enthalpy extraction remained low (= 17.6%) owing to the large pressure loss and as a result, the thermal efficiency of the closed loop remained only 21.6%. The enthalpy extraction and the thermal efficiency became maximal at the optimal inlet total pressure of 0.60 MPa. At inlet total pressure lower than the optimal one, the electric conductivity, the flow velocity, and the electric efficiency became higher. However, the total pressure ratio (= exit/inlet) in the MHD channel became larger particularly at low inlet total pressure because of the increase in the pressure loss due to pebble bed and wall friction. These led to the existence of the optimal inlet total pressure. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 143(1): 27–38, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10118