Yasunori Mitani

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.

Analysis of Kita-Hon HVDC Link for Load Frequency Control of Eastern Japan 50-Hz Power System Based on Application of The CampusWAMS

The CampusWAMS (campus wide area measurement system) based on phasor measurement units (PMU), which covers ten electric power companies of Japan, has been developed for several years. Based only on practical phasor measurements from the CampusWAMS, the paper presents the analysis of KitaHon HVDC Link for load frequency control of Eastern Japan 50Hz power system. Kita-Hon HVDC Link is practically equipped with automatic frequency control function and serves as only interconnection between Hokkaido side and Honshu side of Eastern Japan 50-Hz system. Therefore, it must have certain effects on the load frequency control of both sides. The analysis is carried out using phasor measurements under normal operating condition as well as during the period of a system disturbance. Particularly, the correlation between the frequency deviations of both sides is investigated when Kita-Hon HVDC Link is in operation and out of service, respectively. The effect and its characteristics of Kita-Hon HVDC Link on load frequency control of Eastern Japan 50-Hz power system is observed and concluded based on the analysis results. Keywords-load frequency control; HVDC; synchronized phasor measurements; CampusWAMS; coefficient of determination

A practical approach to tuning of SMES controller based on synchronized phasor measurements for interconnected power system with wind farms

The high penetration of hardly predictable wind power with abrupt changes adversely affects many aspects of power system operations and control, in particular power system stability. To achieve the controller design in practice, this paper presents an approach to tuning of SMES controller based on synchronized phasor measurements for interconnected power system with wind farms. The designed controller is aimed at improving the system damping performance, meanwhile enhancing the stability of a power system. With PMUs, the most recent data of power system can be obtained for controller design. The extended simplified oscillation model is determined for detection and assessment of an approximated inter-area oscillation mode including SMES controller effects. The parameters of SMES controller are systematically tuned with less effort by tabu search towards the design specification. Finally, some simulation studies are carried out to demonstrate and confirm the applicability and effectiveness of the presented approach.

A practical design of fuzzy SMES controller based on synchronized phasor measurement for interconnected power system

Recently, fuzzy logic control has widely received attention in various power system applications, despite difficulties of obtaining its control rules and membership functions. Nowadays, power systems consist of multiple areas where load variations with abrupt changes always exist, and proper control rules and membership functions could hardly be achieved. This paper proposes a practical design of fuzzy logic controllers for superconducting magnetic energy storage (SMES) based on a wide area synchronized phasor measurement for enhancing the stability of an interconnected power system. Moreover, a heuristic method is applied for determining control rules and membership functions. The estimated model is determined via a simplified oscillation model for detection and assessment of an approximated inter-area oscillation mode. Finally, some simulation studies based on a two-area four-machine power system are carried out to examine the performance and effectiveness of the designed fuzzy SMES controller.

Power system stability assessment based on synchronized phasor measurements

An approach to design power system steady state estimation and transient stability assessment using a multi-machine area network based on multiple synchronized phasors measurements is presented. The oscillations were analyzed from measured synchronized phasors in a multi-machine two area network. The fast Fourier transform (FFT) filter was used to extract the desired frequency from the angular frequency estimated by measured synchronized phasors. The dynamic characteristics of the system were linearly approximated with a set of differential equations from which the appropriate eigenvalues were identified for the dominant mode. In transient stability analysis, direct methods were used to derive the rotor angles from generator parameters; phasor voltages and currents. The least square method was used to estimate the power-delta curve from the calculated variables based on the time domain. A disturbance scenario was analyzed and the critical stability region of the power system determined with the equal area criterion. The algorithms developed were tested on a four-machine two area system by simulation of disturbance scenario on the network.

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.

Stability analysis based on synchronized phasor measurements

A method to analyze stability on a multi-machine power system was developed. For steady state estimation the phasor voltages and angles were used to calculate the frequency deviations. The calculated frequency deviations were then filtered by an FFT filter to extract the power oscillations. By linearly approximating a set of differential equations, the eigenvalues for the system were identified from the dominant mode. To do transient stability analysis, rotor angles were calculated from generator parameters; phasor voltages and currents by using direct methods. The equal area criterion was used to analyze disturbance scenario and determine the critical stability region of the power system. The algorithms developed were tested on a four-machine two area system by simulation of disturbance scenario in the network.

Design of SMES Controller for Improving Stabilization of Interconnected Power System based on Synchronized Phasor Measurement

This paper presents the design of superconducting magnetic energy storage (SMES) controller for improving stabilization of interconnected power system based on synchronized phasor measurement. Load variations with abrupt changes occurring in a power system cause fluctuations of tie-line power flow and significantly disturb the effective use of transmission lines. As one of promising energy storage devices, SMES is applied for power system stabilization. SMES controller is designed based on the wide area synchronized phasor measurement. The estimated model is determined as a coupled vibration model for detection and assessment of an approximated inter-area oscillation mode. Finally, some simulation studies are carried out to demonstrate the applicability and effectiveness of the design method.

A practical controller design of distributed energy resources for stabilization of interconnected power system based on synchronized phasor measurements

With todays advanced technologies, various types of distributed energy resources (DERs) with relatively fast controllability option have been brought into practical applications. This paper presents a metaheuristic-based controller design of controllable DER for stability enhancement based on synchronized phasor measurements. With the most recent data, a simplified oscillation model (SOM) is evaluated and referred to as an estimated power system model for detection and assessment of an estimated inter-area oscillation mode. Subsequently, an extended SOM is formulated by including dynamic effects of DER control system. The designed controller can be achieved via a metaheuristic method with less effort towards the design specification. Moreover, performance of the designed controller can be evaluated during design to avoid its adverse effects. Some simulation results demonstrate and confirm the applicability and effectiveness of the proposed controller design method.