• Title/Summary/Keyword: electrical frequency

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The Comparative Effect of Time-Frequency Distribution Function in a Time-Frequency Domain Reflectometry System (시간-주파수 영역 반사파 계측 시스템에서 다양한 시간-주파수 분포 함수의 영향 연구)

  • Kwak, Ki-Seok;Tok, Son-Choe;Tae, Sung-Yoon;Jin, Bae-Park;Jae, Won-Kho
    • Proceedings of the KIEE Conference
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    • 2004.07d
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    • pp.2149-2151
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    • 2004
  • The time-frequency domain reflectometry(TFDR) is well known to detect and locate a fault in a coaxial cable[3]. Traditional reflectometry methods have been achieved in either the time domain or frequency domain only. However, the time-frequency domain reflectometry utilizes time and frequency information of a reflected signal passed through a cable to detect and locate the fault. The purpose of this paper is to find appropriate time-frequency distribution function suitable for a TFDR system. Choosing the appropriate time-frequency distribution function implies one can detect the fault and estimate the location accurately. We consider and compare adequate time-frequency distribution function on the basis of experimental results.

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Virtual Inertial Control of a Wind Power Plant using the Maximum Rate of Change of Frequency (주파수의 최대 변화율을 이용한 풍력단지 가상관성제어)

  • Kim, Dooyeon;Kim, Jinho;Lee, Jinshik;Kim, Yeon-Hee;Chun, Yeong-Han;Kang, Yong Cheol
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.62 no.7
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    • pp.918-924
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    • 2013
  • In a conventional power system, the frequency is recovered to the nominal value by the inertial, primary, and secondary responses of the synchronous generators (SGs) after a large disturbance such as a generator tripping. For a power system with high wind penetration, the system inertia is significantly reduced due to the maximum power point tracking control based operation of the variable speed wind generators (WGs). This paper proposes a virtual inertial control for a wind power plant (WPP) based on the maximum rate of change of frequency to release more kinetic energy stored in the WGs. The performance of the proposed algorithm is investigated in a model system, which consists of a doubly fed induction generator-based WPP and SGs using an EMTP-RV simulator. The results indicate that the proposed algorithm can improve the frequency nadir after a generator tripping. In addition, the algorithm can lead the instant of a frequency rebound and help frequency recovery after the frequency rebound.

A Study on an Evaluation Modeling of Power System Performance for Frequency Regulation ESS Based on the PSCAD/EMTDC (PSCAD/EMTDC를 이용한 주파수조정용 ESS의 계통영향성 평가 모델링에 관한 연구)

  • Choi, Sung-Sik;Kang, Min-Kwan;Lee, Hu-Dong;Nam, Yang-Hyun;Park, Ji-Hyun;Rho, Dae-Seok
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.67 no.8
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    • pp.1024-1030
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    • 2018
  • Recently, the large scaled energy storage system(ESS) which has various functions such as peak saving, demand management, output stabilization of renewable energy and frequency regulation(FR) is being energetically installed and operated. Especially, as the use case of frequency regulation ESS, the KEPCO has demonstrated the total of 376[MW] ESS since 2014. However, there are no operational experiences and international technical standards on frequency regulation application in ESS. Therefore, this paper propose the evaluation algorithm for power system performance of ESS by considering the frequency characteristics between governor of existing generator and frequency regulation ESS, in order to verify the power system performance of ESS. And also, this paper propose an evaluation modeling for small scaled power system including the existing generator, frequency control ESS and customer loads based on the PSCAD/EMTDC S/W. From the simulation results in 360[MW] model power system, it is confirmed that frequency regulation ESS has better performances than conventional generators.

A Study on Slip Frequency Control And Frequency Compensation in CSIM (전류형 인버터로 구동되는 유도 전동기의 슬립 주파수 제어와 주파수 보상에 관한 연구)

  • Jeon, Hi-Jong;Kim, Chun-Soo;Lee, Myong-Woo;Jeong, Won-Seok;An, Jae-Woo
    • Proceedings of the KIEE Conference
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    • 1988.11a
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    • pp.306-309
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    • 1988
  • For the purpose of fast response and simplifing system angle control strategy is selected. And the analysis and dynamic performance of a slip frequency controlled current source inverter fed induction motor drive with stator frequency compensation (indirect torque angle control) is investigated. The current control loop including motor is modeled and speed control loop including the frequency compensation is analysed. And transfer function of overal system is simplified. Experimental results are given in support of the analytical procedure.

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Study on Hybrid PWM Method under Low Switching Frequency

  • Kekang, Wei;Zheng, Trillion Q.;Wang, Ran;Wang, Chenchen
    • Journal of international Conference on Electrical Machines and Systems
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    • v.1 no.2
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    • pp.64-69
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    • 2012
  • This paper presents a hybrid pulse width modulation (PWM) method under low switching frequency conditions based on space vector PWM (SVPWM) and selective harmonic eliminated PWM (SHEPWM), which use asynchronous carrier modulation SVPWM at low frequency, and SHEPWM at high frequency, a square wave after rated conditions. A transitive strategy is proposed to realize a smooth transition of individual modes including SVPWM, SHEPWM and square waves. Experimental results confirm this hybrid modulation method and their transition are reasonable and proper.

Design of Coordinated Frequency Control Strategy applied to EDLC and BESSs for Microgrid in the Islanded Mode (독립운전 모드의 마이크로그리드에서 EDLC와 BESS의 주파수 협조제어전략 설계)

  • Yoo, Hyeong-Jun;Kim, Hak-Man
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.63 no.6
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    • pp.820-827
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    • 2014
  • Since a microgrid has renewable energy sources, imbalance between power supply and power demand occurs in the islanded mode. In order to solve the imbalance, several energy storage systems (ESSs) such as bettary energy storage system (BESS), EDLC (electric double layer capacitor), flywheel, and SMES (superconducting magnetic energy storage) are generally used. Especially, their electrical characteristics are different. For efficient use of them, a coordinated control scheme is required. In this paper, a coordinated control scheme for using a Lead-acid BESS, a Lithium BESS, and a EDLC is designed to efficient frequency control for a microgrid in the islanded mode. The coordinated frequency control strategy is designed based on their electrical characteristics. The feasibility of the proposed coordinated frequency control strategy is verified through the simulation.

Design of Battery System for Smoothing Wind Power Variations in Power System based on Frequency Response Analysis

  • Nakajima, Kyouhei;Umemura, Atsushi;Takahashi, Rion;Tamura, Junji
    • Journal of international Conference on Electrical Machines and Systems
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    • v.2 no.3
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    • pp.342-348
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    • 2013
  • As a number of wind power generation systems have been installed in power systems in the world, frequency fluctuations due to output power variations from wind farms have become a serious problem. Battery systems have been studied for smoothing the output variations and decreasing the resulting frequency fluctuations. Among these studies, efficient design of battery systems is one of the most important subjects from a point of view of cost. This paper presents a comparative analysis of the smoothing effect between the conventional moving average method and a new method based on frequency response analysis.

On-line Faults Signature Monitoring Tool for Induction Motor Diagnosis

  • Medoued, Ammar;Lebaroud, Abdesselem;Boukadoum, Ahcene;Clerc, Guy
    • Journal of Electrical Engineering and Technology
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    • v.5 no.1
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    • pp.140-145
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    • 2010
  • The monitoring and the diagnosis of the faults in induction motors starting from the stator current are very interesting, since it is an accessible and measurable quantity. The spectral analysis of the stator current makes it possible to highlight the characteristic frequencies of the faults but in a wide frequency range depending on half the sampling frequency, making it very difficult to monitor on-line the faults. In order to facilitate the use of the relevant frequencies of machine faults we proposed the extraction of the frequency components using two methods, namely, the amplitude and the instantaneous frequency. The theoretical bases of these methods were presented and the results were validated on a test bench with an induction motor of 5.5 kw.

A Novel Switched Capacitor Lossless Inductors Quasi-Resonant Snubber Assisted ZCS PWM High Frequency Series Load Resonant Inverter

  • Fathy, Khairy;Kang, Tae-Kyung;Kwon, Soon-Kurl;Suh, Ki-Young;Lee, Hyun-Woo;Nakaoka, Mutsuo
    • Proceedings of the KIEE Conference
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    • 2005.10c
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    • pp.169-171
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    • 2005
  • In this paper, a novel type of auxiliary switched capacitor assisted edge resonant soft switching PWM series load resonant high frequency inverter with two auxiliary edge resonant lossless inductor snubbers is proposed for small consumer induction heating appliances. The operation principle of this high frequency inverter is described using the switching mode equivalent circuits. The practical effectiveness of the newly proposed soft switching inverter are discussed as compared with the conventional soft switching high frequency inverters based on simulation and experimental results from an application point of view.

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Study on Advanced Frequency Estimation Technique using Gain Compensation

  • Park, Chul-Won;Shin, Dong-Kwang;Kim, Chul-Hwan;Kim, Hak-Man;Kim, Yoon-Sang
    • Journal of Electrical Engineering and Technology
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    • v.6 no.4
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    • pp.439-446
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    • 2011
  • 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.