Katsuhiko Uemura

Modal Analysis for Power System Dynamic Stability

This paper deals with a numerical method to find the significant eigenvalues (damping factors and natural frequencies) and eigenvectors (oscillation mode shapes) in the dynamic stability range of a power system.

State Estimation of Large Scale Electric Power Systems by Decomposition Methods

Abstract This paper deals with the computational methods for the state estimation problem of a large-Scale electric Power system. This state estimation problem can be defined as the power flow problem which has overdetermined boundary conditions, and non-linear function minimization techniques can be used to solve the problem. The mathematical foundation of proposed methods is based upon the perturbed Newton method which includes as special cases standerd function minimization techniques such as Newton-Gauss method, Fretcher-Powel1 method and steerest descent method. The proposed methods in this paper are considered as decomposition methods for the reason that the coefficient matrices of iteration schemes are decomposed into block diagonal forms from the view joints of a power system configuration or a sersitivity between variab1es. These methods are suitable for the state-estimation problem which has many state variables for the simplicity of the coefficient moatrix in non-linear function minimization techniques.

Knowledge-Based Operation Guidance Method for Voltage and Reactive Power Control in Power Systems

Abstract This paper presents a new method for operation guidance of the voltage and Veactive power control in electric power systems. This control idea makes use of knowledge about the system state, control devices, operating rules, operator s experience and other requirements for an actual system operation. With this guidance method, the operator can easily obtain a desirable operating procedure which otherwise he would find after many trial-and-errors. As this method is based on a knowledge engineering technique, a suitable operating guidance tool for each utility can be easily built by rewriting the knowledge base.

A NEW EFFICIENT METHOD FOR INTEGRATED CONTROL OF VOLTAGE AND REACTIVE POWER IN POWER SYSTEMS

This paper presents an efficient method for the integrated control of voltage and reactive power in power systems. This method is able to maintain the bus voltages in their permissible limits while simultaneously realizing well-balanced operation of VAR sources and a reduction in active transmission losses. The proposed method has the following features compared with the conventional methods. (1) Voltage and reactive power control is divided into two parts: control of the switchable VAR sources and control of the load tap-changing transformers. This decomposition technique can realize well-balanced operation of VAR sources.

Operational Transfer Matrix Based Analysis of Power System Dynamic Stability

Abstract Eigenvalue method based on state space matrix and other conventional methods used for dynamic stability analysis are not suited for a multi-machine system consisting of hundreds of machines with automatic voltage regulators and speed governors. This paper shows that the frequency response method is very useful for such a large scale system. The stabillity analysis is based on operational transfer matrix from internal angles to input mechanical torques. The critical stability condition obtained by the proposed method is compared with that obtained from field tests and it is shown that the proposed method is sufficiently accurate and efficient. Eigenvalues and mode shapes of the power system are also calculated by using the operational transfer matrix. Two algorithms are presented; topological method and iteration method. The analysis methods are used for planning, design and operation of power systems.