Osamu Saeki

Economic and Efficient Voltage Management Using Customer-Owned Energy Storage Systems in a Distribution Network With High Penetration of Photovoltaic Systems

The widespread installation of distributed generation systems is crucial for making optimal use of renewable energy. However, local distribution networks face voltage fluctuation problems if numerous photovoltaic (PV) systems are connected. Recently, energy storage systems that can be installed at commercial customers have been developed. This paper proposes a concept that solves the voltage fluctuation problem in distribution networks with high penetration of PV systems by using customer-side energy storage systems. The distribution network operator (DNO) is allowed to control the output of the energy storage systems of customers during a specific time period in exchange for a subsidy covering a portion of the initial cost of the storage system. The cost effectiveness of the cooperative operation for both customer and DNO is discussed by numerical simulations based on minute-by-minute solar irradiation data. Our results have clarified the possibilities of making voltage management more economical in distribution networks.

Oscillation mode analysis in power systems based on data acquired by distributed phasor measurement units

In the Japan western 60 Hz System, it is generally known that the longitudinal structure produces various system oscillations, such as long term oscillation, local generator oscillation and oscillation caused by frequency control among systems. However, little is known about the wide-area phenomena in the system. The purpose of this study is to establish an analysis method using actual measurements, and to clarify the oscillations in the power systems. The authors placed a PMU (Phasor Measurement Unit) connected to 100 V outlets in some Universities in the 60 Hz power system. The PMU is synchronized based on the Global Positioning System (GPS) and measured data are transmitted via the Internet. At present, a technique for clarifying the oscillations in the power system is being investigated. This paper describes signal processing of measurement data acquired by PMU for the analysis of power system oscillations.

Observation of frequency oscillation in western Japan 60 Hz power system based on multiple synchronized phasor measurements

Western Japan 60 Hz power system is a longitudinal power system which consists of interconnected six major electric power companies. Though the power system has some interesting oscillation characteristics, there were few researches based on observation as a whole system. Authors have constructed an online global monitoring system of the power system dynamics, which is based on multiple synchronized phasor measurement technique using time stamp of the Global Positioning System (GPS) and Internet. This paper presents some results of observing system frequency oscillation and discussed the difference among the measured point. System dynamics due to the load frequency control (LFC) can be extracted from observed frequency oscillations by time-frequency analysis based on the Wavelet transform. Because variations of phase difference between the interconnected two areas are closely related with tie line power flow variations, relations between the frequency oscillations and the LFC are also investigated.

Analysis of power system dynamics based on multiple synchronized phasor measurements

In Japan western 60 Hz System, it is generally known that its longitudinal structure produces various system oscillations, such as long term oscillation, local generator oscillation and oscillation caused by frequency control among systems. However, little is known about the wide-area phenomenon in systems. The purpose of this study is to establish the analysis method used actual measurements and to clarify the oscillations in the power systems. Authors placed PMU (phasor measurement unit) connected to 100 V outlets in some universities in the 60 Hz power system. PMU is synchronized based on the global positioning system (GPS) and measured data are transmitted via Internet. In present, the technique for clarifying the oscillation in the power systems is being investigated. This paper describes some results to evaluate the power system oscillation characteristics.

Power System Dynamic Performance Measured by Phasor Measurement Unit

In recent years, there has been an increasing interest in monitoring and analyzing dynamic performances of power systems, such as observation of power system oscillations and evaluation of machine parameters. However, in Japan, there was little observation as a whole power system. In this paper the authors present a global monitoring system of power system dynamics by using the synchronized phasor measurement of demand side. Authors have placed phasor measurement units (PMU) connected to 100 V outlets in some universities in Japan and been researching into oscillation characteristics in power systems. Phasor measurements are synchronized based on the global positioning system (GPS) and measurement data are transmitted via Internet. Some oscillative features and variation of phasor in a day, a week or a year are analyzed using the acquired data. The purpose of this paper is to show a power system dynamic performance by the use of measurement data at an unexpected disturbance and monitors a global and a local oscillation mode.

Monitoring power system dynamics based on phasor measurements from demand side outlets developed in Japan Western 60 Hz System

Japan Western 60 Hz System consists of six major electric power companies. Due to its longitudinal structure there are some significant oscillation modes represented by long term oscillation among whole system. So far, some oscillative characteristics have been measured in own area or in the interconnected tie lines. However, there was little observation as a whole power system. In this paper the authors present a global monitoring system of power system dynamics by using the synchronized phasor measurement of demand side outlets, which are located in some universities in the 60 Hz power system. Phasor measurements are synchronized based on the global positioning system (GPS) and measured data are transmitted via Internet. Some oscillative features and variation of phasor in a day, a week or a year are analyzed using the acquired data.

Observation of power system oscillation characteristics by using measurement data obtained from demand side outlets

In Japan western 60 Hz system, it is generally known that its longitudinal structure produces various system oscillations, such as long term oscillation, local generator oscillation and oscillation caused by frequency control among systems. However, little is known about the wide-area phenomenon in systems. The purpose of this study is to establish the analysis method used actual measurements and to clarify the oscillations in the power systems. Authors placed PMLJ (Phaser Measurement Unit) connected to 100 V outlets in some Universities in the 60 Hz power system. PMU is synchronized based on the global positioning system (GPS) and measured data are transmitted via Internet. In present, the technique for clarifying the oscillation in the power systems is being investigated. This paper describes some results to evaluate the power system oscillation characteristics by PMU.

Real-time power system monitoring at demand sides by Campus Wide Area Measurement System

Modern electric power transmission and distribution systems form a huge and complicated system. Fortunately, Phasor Measurement Units (PMUs) have been developed, which can correct voltage phasors as sequential data with precise time synchronization based on time stamps by the Global Positioning System (GPS). The PMU has great possibilities for wide area measurement or protection in the power system. Recently, advanced information technologies make it available that any users, not only power system operators, perform the wide area measurement by the PMU. Authors and co-researchers have developed global monitoring systems of Japanese and Southeast Asian power systems by the PMUs, which are named as Campus Wide Area Measurement Systems (Campus WAMSs). This paper investigates the possibility of the Campus WAMS as a simple online monitoring system of power system dynamics. The monitoring system only plots the corrected data on a plane of frequency deviation versus phase difference, and evaluates an expanse of an aggregate of the data. Therefore, the monitoring system can be run even at the customer-side and reduce data processing and influences by loss of data or time synchronization. The availability of the monitoring system is confirmed by examples of the actual data.

An Application of Dual Affine Scaling Method to MARKAL Type Energy Models

Abstract Linear Programming (LP) has been used in many applications for power systems and energy systems, including MARKAL models. In 1984, Karmarkar proposed a new interior point method which is a polynomial time algorithm, to solve LP problems. Since then, many variants of interior point methods have been studied and reported and the dual affine scaling method is one of them. In this paper, we report the results of applying a variant of dual affine scaling method to MARKAL-type energy models in which optimal solutions tend to be degenerate. The results confirmed the computational advantage of the dual affine scaling method over the simplex method.

An Application of Interior Point Method to 0-1 Mixed Integer Programing Problems

Abstract In many fields, 0-1 mixed integer programming (MIP) problems are prevailingly used. These problems are often solved by the branch and bound method. However, it requires much calculation time. Some of the 0-1 MIP problems have multiple optimal solutions on the first relaxed linear programming problems. In this paper, a method which is an application of the interior point method is proposed to solve these problems. It will be shown that the proposed method is more effective than the conventional method and by the numerical experiments it will be shown that the proposed method reduces the number of created subproblems and the calculation time on the various size problems.