Junichi Toyoda

Power arrival evaluation of bulk system including network constraints based on linear programming approach

Several useful support tools of power system scheduling and planning are provided. A fast method is proposed and used to evaluate the generating units and transmission capability of a power system and calculate the optimal reserve of each demand side, based on a two-step linear programming technique. A new support tool for power system planning is described by using the parametric linear programming. This support tool quickly gives an optimal reserve curve of the system and also provides some diagnosis information of the systems weak location for the expansion planning and maintenance scheduling of transmission lines or generating units. The outages of generators and transmission lines are considered, and a method of estimating the reliability (LOLP) of a multiarea power system by making use of linear programming is presented. Several examples are used to verify the proposed methodology and illustrate the application. The results show that the approaches are simple, fast, and efficient support tools for generation and transmission capability evaluation or for the contingency testing of a power system. >

An autonomous decentralized control mechanism for power flow in an open electric energy network

This paper discusses a power flow control mechanism for the “open electric energy network” (OEEN), which has been studied by the authors as a demand-side network suitable for a free market of electricity. The important concept of OEEN is that electric energy is treated like a packet of mail, with information about the sender (power producer) and the receiver (consumer). The control mechanism discussed in this paper is called the electric energy router and includes an energy storage device. The electric energy router controls the storage device in such a way that the “electricity packet” reaches a specified consumer from a specified power producer autonomously and in the distributed manner. This paper shows that optimal control theory can be applied to determine the control action of the electric energy router. The obtained optimal control action minimizes the difference between the load pattern of the consumer and the supply pattern of the router under the inequality constraints of energy storage capacity. A numerical example is given in order to check the validity of optimal control theory application. In order to manufacture a small-scale electric energy router for experiments, its basic structure and power control performance are studied through simulation studies.

Security Enhancement of Multiple Distributed Generation by the Harmonized Grouping

By social and technical reasons, the amount of the distribution generation will considerably increase in the future power supply system. For the secure supply and the safe operation of the distributed generation (DG) power, the harmonized grouping of DG plants and the careful interconnection of the DG micro grid to the existing power grid are required. This paper discusses the DG grouping in order to harmonize the investment of assets, the quality of power supply and the cooperation with the existing power grid. Model analysis shows there are several schemes of the DG plants and the storage device related to the combination of economical parameters. Recently, the demonstration research projects of DG grouping have been performed in Japan. Brief description of these projects is also included

Dominant mode filter for enhancing power system stability

Abstract This paper proposes a new type of filter, that is, a dominant mode filter (DMF) which uses the rotor speed fluctuations for dynamic security assessment and stability enhancement of power systems. The proposed filter can be used in detecting the degradation of damping power of the system and in improving the stabilizing ability of a control device such as PSS. The basic concept of the DMF design is based on the inherent characteristics of the power system network and the application of principal component analysis to a covariance matrix of the rotor speed fluctuations. The coefficients of the DMF are easily computed from the eigenvector of the covariance matrix. The weak damping modes which are useful for generating the control signals of the stabilizing devices, are satisfactorily estimated from the rotor speed fluctuations by means of the DMF. In the computing process of the DMF coefficients the ‘mode energy’ and ‘mode profile’ are also obtained from the eigenvalue and the eigenvector of the covariance matrix respectively. The mode energy is the strength of each mode contained in the fluctuations. The mode profile expresses the distribution of the mode oscillation with the rotor speed responses of all machines. Since, in the DMF design, the on-line fluctuation data are used, the weak damping modes, the mode energy and the mode profile can be estimated adaptively according to the system situation. In this paper, applications of the DMF are also discussed. One application is to use the mode energy as an on-line stability index. If the damping power of the system becomes weak, a system operator can detect signs of an unstable condition by observing the time variation of the mode energy. Another is a disturbance identifier to find the location and severity of a disturbance. This identifier utilizes the mode profile and mode energy. The third application of the DMF is to supply the slower mode component as a global control signal for HPSS (Hybrid PSS)11. The mode energy can be also utilized for adapting the parameters of the HPSS.

Dual-Time-Scale Simulation of Superconducting Magnetic Energy Storage for Enhancement of Electric Power System Stability

In this paper, a practical simulation method is developed for the aim to combine the ‘slow’ and ‘fast’ dynamic models of SMES in power systems on the basis of a dual-time-scale modeling. The parallel processing for the dual- time-scale simulation are realized by multi transputer networks. Proposed simulation technique is successfully applied to verify the experimental results obtained by a 1MJ-SMES test system which has been developed at Tohoku Electric Power Company in 1991.

Flexible Electric Power Distributor for Smart Use of Dispersed Generation Plants in Metropolitan Area

Abstract This paper proposes a flexible electric power distributor which is called “ Electric Energy Router “ for the adjustment of imbalance between supply and demand in a free market of electricity. The distributor is a main component of “ OEEN (Open Electric Energy Network) “ which has been studied by authors as the demand-side network suitable for the participation of various power producers in the market. In OEEN, electric energy is treated as a packet of electricity, and flows autonomously under the supervision of the distributor. OEEN and Electric Energy Router will settle the complicated problems of power flow control in the market.