Chul-Won Park

A Comparative Study on Frequency Estimation Methods

In this paper, a comparative study on the frequency estimation methods using IRDWT(Improved Recursive Discrete Wavelet Transform), FRDWT(Fast Recursive Discrete Wavelet Transform), and GCDFT(Gain Compensator Discrete Fourier Transform) is presented. The 345[kV]power system modeling data of the Republic of Korea by EMTP-RV is used to evaluate the performance of the proposed two kinds of RDWT(IRDWT and FRDWT) and GCDFT. The simulation results show that the frequency estimation technique based on FRDWT could be the optimal frequency measurement method, and thus can be applied to FDR(Fault Disturbance Recorder) for wide-area blackout protection or frequency measurement apparatus.

Algorithm for Fault Detection and Classification Using Wavelet Singular Value Decomposition for Wide-Area Protection

An algorithm for fault detection and classification method for wide-area protection in Korean transmission systems is proposed. The modeling of 345-kV and 765-kV Korean power system transmission networks using the Electro Magnetic Transient Program - Restructured Version (EMTP- RV) is presented and the algorithm for fault detection and classification in transmission lines is developed. The proposed algorithm uses the Wavelet Transform (WT) and Singular Value Decomposition (SVD). The Singular value of Approximation coefficient (SA) and part Sum of Detail coefficient (SD) are introduced. The characteristics of the SA and SD at the fault conditions are analyzed and used in the algorithm for fault detection and classification. The validation of the proposed algorithm is verified by various simulation results.

Study on Advanced Frequency Estimation Technique using Gain Compensation

Frequency is an important operating parameter for the protection, control, and stability of a power system. Thus, it must be maintained very close to its nominal frequency. Due to the sudden change in generation and loads or faults in a power system, however, frequency deviates from its nominal value. An accurate monitoring of the power frequency is essential for optimum operation and prevention of wide area blackout. Most conventional frequency estimation schemes are based on the DFT filter. In these schemes, the gain error could cause defects when the frequency deviates from the nominal value. We present an advanced frequency estimation technique using gain compensation to enhance the DFT filter-based technique. The proposed technique can reduce the gain error caused when the frequency deviates from the nominal value. Simulation studies are performed using both the data from EMTP-RV software and the user-defined arbitrary signals to demonstrate the effectiveness of the proposed algorithm. Results show that the proposed algorithm achieves good performance under both steady state tests and dynamic conditions.

Dynamic Characteristic Analysis of Water-Turbine Generator Control System of Sihwa Tidal Power Plant

Abstract - Tidal power is one of new and renewable energy sources. The seawater is stored inside a tidal embankment built at the mouth of a river or bay, where tides ebb and flow. The water turbine-generators produce power by exploiting the gap in the water level between the water outside and inside the embankment. Tidal power plant is a large plant that is installed on the sea. And then, the facilitys operations and a separate control system for monitoring and maintenance is required. However, this plant predictive control of building systems and technologies have been avoided the transfer of technology from advanced global companies. Accordingly, the control system for core technology development and localization is urgently needed. This paper presents modeling and simulation using by PSS/E about generator, governor, exciter, and power system stabilizer for control system in Sihwa tidal power plant to improve the efficiency and develope of core technology. And the dynamic characteristics of governor and exciter were analyzed.Key Words : Control system, Dynamic characteristics, Exciter, Governor, New and renewable energy, Sihwa tidal power plant, Power system stabilizer, PSS/E, Water-turbine generator †교신저자, 종신회원 : 강릉원주대학교 전기공학과 교수․공박E-mail : cwpark1@gwnu.ac.kr*정 회 원 : 강릉원주대학교 전기공학과 석사과정**정 회 원 : 강릉원주대학교 전기공학과 석사과정 접수일자 : 2012년 10월 5일최종완료 : 2012년 11월 12일

Fault Simulation and Analysis of Generator

Large generator of power plant is very important. In order to protect large generator from faults, digital protective relay or IED is required. However, all protective relays for generators of the domestic power plant are operated by foreign products. And now, for technological independence from foreign and improvement of import substitution effect, IEDs using domestic technology are being developed. To evaluate performance of developing next-generation power devices, the study of the dynamic characteristics of the power plant, generator system modeling, fault simulation and analysis, should be considered. Specially, To obtain IEEE Standards COMTRADE format for relay operation test, generator system modeling and fault simulation using PSCAD/EMTDC tools must be preceded. Until now, a complete modeling of generator internal windings and fault simulation techniques dose not exist. In this paper, for evaluation performance of relay elements of developing IED, the generator system modeling and various faults simulation using PSCAD/EMTDC tools were performed. And then, the various transient phenomena through obtained relaying signal of developed modeling were analyzed.

A review of network technologies in power monitoring systems in Korea

With recent introduction of IT in power systems, a number of studies are being conducted regarding the implementation of monitoring systems that utilize various technologies for monitoring transmission facilities. A power monitoring system monitors power system status based on realtime data acquired by various sensor elements installed on power transmission lines and facilities. A power monitoring system consists of multiple sensors on wired and wireless networks. This paper reviews various wired and wireless communication technologies used in sensor networks deployed in power monitoring systems in Korea.

A comparative study of frequency estimation techniques

This paper describes a comparative study of frequency estimation techniques using the angle between two phasors, high speed FIR filtering, and positive sequence component. The three frequency estimation techniques to be discussed are the DFT filtering based algorithm using phasor angle between two phasors, the high speed FIR filtering based algorithm, and positive sequence component based algorithm using the half angle between two successive positions of phasor. In this paper, these frequency estimation techniques have been formulated through numerical manipulation of a discrete system. For ATP simulation data, the performance of these three frequency estimation techniques are also compared.

Advanced Distance Relaying of on a Double Circuit Transmission Line

This paper proposes an advanced distance relaying based on the DC offset removal filter to minimize the effects of DC offset on a double circuit transmission line. The proposed DC offset removal filter uses only one cycle of data for phasor extraction computation, which does not need to preset the time constant of the DC offset component. This proposed distance relaying uses not only the residual current of the faulted circuit but also mutual current of the healthy adjacent circuit. A series of off-line test results using ATP simulation data show the effectiveness of the an advanced distance relaying.

Distributed Sensor Network-Based Virtual FDR System

We propose an application for power facility monitoring using distributed sensor networks. The proposed application is a virtual frequency disturbance recorder (FDR) system that estimates the frequency of a power grid using the data from a modeled grid and sends the information to the server for monitoring via wireless communication. To verify the validity of the proposed application, we conducted experiments using actual system data. The functionality of the proposed system was also verified by establishing a ZigBee-based wireless network for power monitoring and diagnosis of disturbances.

Generator fault detection technique using detailed coefficients ratio by daubechies wavelet transform

An AC (alternating current) generator is one of the important components in producing a electric power and so it requires highly reliable protection relays to minimize the possiblity of demage occurring under fault conditions. Conventionally, a RDR (ratio differential relaying) based on DFT (discrete Fourier transform) has been used for protecting the stator winding of a generator. However, when DFTs based on Fourier analysis are used, it has been pointed out that defects can occur during the process of transforming a time domain signal into a frequency domain one which can lead to loss of time domain information. This paper proposes the adoption of a protection algorithm for the stator by applying a WT (wavelet transform) to overcome the defects in the DFT process. Moreover, a new ratio equation is proposed for easy utilization of the detailed coefficients by DWT (Daubechies wavelet transform) through the course of MLD (multi-level decomposition) using MATLAB. For the case studies reported in the paper, a model system was established for the simulations utilizing the ATP (alternative transient program), and this verified the effectiveness of the proposed technique through various off-line tests carried out on the collected data. The propose method is shown to be able to rapidly identify internal faults and did not operate a miss-operation for all the external faults tested.