• Title/Summary/Keyword: Reactive Power Variation

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Gird-interactive Current Controlled Voltage Source Inverter System with UPS (UPS를 고려한 계통연계 전류제어형 전압원 인버터)

  • Ko, Sung-Hun;Lim, Sung-Hun;Lee, Su-Won;Lee, Seong-Ryong
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.56 no.6
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    • pp.1064-1070
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    • 2007
  • This paper presents a grid-interactive current controlled voltage source inverter (CCVSI) with uniterruptible power supply (UPS), which uses an inner current control loop (polarized ramp time (PRT)) and outer feedback control loops to improve grid power quality and UPS. To reduce the complexity, cost and number of power conversions, which results in higher efficiency, a single stage CCVSI is used. The operation of this system could be divided into the power quality control (PQC) state mode and the UPS state mode. In PQC mode, the system operated to compensate the reactive power demand by nonlinear load or variation in load. In UPS mode. the system is controlled to provide a sinusoidal voltage at the rated value for the load when the gird fail. To verify the proposed system, a comprehensive evaluation with theoretical analysis, simulation and experimental results for 1KVA load capacity is presented.

Electric Energy Saving System for Lighting with Power Conditioning (전력품질개선 기능을 갖는 조명 에너지 절약 시스템)

  • Kwon, H.D.;Park, C.S.;Jo, S.P.;Ko, S.H.;Lee, S.W.;Lee, S.R.
    • Proceedings of the KIPE Conference
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    • 2008.06a
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    • pp.151-153
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    • 2008
  • This paper deals with the electric energy saving system for lighting with power conditioning, which aims at the integration of power quality improvement and energy saving. The system consists of a CCVSI(Current-Controlled Voltage Source Inverter) and VCVSI(Voltage-Controlled Voltage Source Inverter). The CCVSI is connected in parallel to a grid, which can be operated to compensate the reactive power demanded by nonlinear and variation loads. The VCVSI is connected to the CCVSI through the DC capacitor (DC side) and in series on the AC side(lighting load), which can perform the energy saving. The operation of the proposed system is confirmed through the simulation and its usefulness is discussed.

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SSSC model for Power Flow Study using IPLAN (IPLAN을 이용한 SSSC 조류계산 모델)

  • Kook, Kyung-Soo;Kim, Hak-Man;Lee, Young-Woon;Oh, Tae-Kyoo;Jang, Byung-Hoon;Chu, Jin-Bu
    • Proceedings of the KIEE Conference
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    • 1999.07c
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    • pp.1164-1166
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    • 1999
  • This paper presents Static Synchronous Series Compensator(SSSC) model for power flow study using IPLAN. In the proposed model, SSSC is represented by the equivalent load variation. The equivalent load consists of active power load specified by user and reactive power load which is founded for considering characteristic of SSSC. And this is implemented by IPLAN which is a macro-external program for PSS/E. Using this model, SSSC can be solved in load-flow by just calling the model in PSS/E. The proposed model was applied to a realistic power system for validity test.

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Reactive Power Variation Method for Anti-islanding Using Digital Phase-Locked-Loop (DPLL을 이용한 능동적 단독운전방지를 위한 무효전력변동법)

  • Lee, Ki-Ok;Yu, Byung-Gu;Yu, Gwon-Jong;Choi, Ju-Yeop;Choy, Ick
    • Journal of the Korean Solar Energy Society
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    • v.28 no.2
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    • pp.64-69
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    • 2008
  • As the grid-connected photovoltaic power conditioning systems (PVPCS) are installed in many residential areas, these have raised potential problems of network protection on electrical power system. One of the numerous problems is an Islanding phenomenon. There has been an argument that it may be a non-issue in practice because the probability of islanding is extremely low. However, there are three counter-arguments: First, the low probability of islanding is based on the assumption of 100% power matching between the PVPCS and the islanded local loads. In fact, an islanding can be easily formed even without 100% power matching (the power mismatch could be up to 30% if only traditional protections are used, e.g. under/over voltage/frequency). The 30% power-mismatch condition will drastically increase the islanding probability. Second, even with a larger power mismatch, the time for voltage or frequency to deviate sufficiently to cause a trip, plus the time required to execute a trip (particularly if conventional switchgear is required to operate), can easily be greater than the typical re-close time on the distribution circuit. Third, the low-probability argument is based on the study of PVPCS. Especially, if the output power of PVPCS equals to power consumption of local loads, it is very difficult for the PVPCS to sustain the voltage and frequency in an islanding. Unintentional islanding of PVPCS may result in power-quality issues, interference to grid-protection devices, equipment damage, and even personnel safety hazards. Therefore the verification of anti-islanding performance is strongly needed. In this paper, improved RPV method is proposed through considering power quality and anti-islanding capacity of grid-connected single-phase PVPCS in IEEE Std 1547 ("Standard for Interconnecting Distributed Resources to Electric Power Systems"). And the simulation results are verified.

Load Characteristic Identification and Transient Stability Analysis Using Neural Network (신경회로망에 의한 부하식별과 과도안정도 해석)

  • Lee, Jong-Pil;Kim, Tae-Eung;Ji, Pyeong-Shik;Nam, Sang-Cheon;Lim, Jae-Yoon;Kim, Jung-Hoon
    • Proceedings of the KIEE Conference
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    • 1997.07c
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    • pp.1127-1129
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    • 1997
  • In this paper, we developed to artificial neural network for load characteristic identification of power system. We can acquire active power and reactive power of individual load depending on the variation of voltage and frequency from the experimentation of a dynamic characteristic of load. The data of the experimental results were be used in learning of ANN. A proposed ANN model is applied to analyze the transient stability. To demonstrate the propriety of the power system transient stability with load model using ANN, the simulation of the two-machine five-bus system is carried out.

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Simulation Study on Capturing Maximum Wind Power Control Method of DFIG based on PSCAD/EMTDC (PSCAD를 이용한 DFIG풍력발전 최대출력 풍력발전 제어방법에 관한 연구)

  • Sun, Qitao;Choi, Joon-Ho;Park, Sung-Jun;Nam, Soon-Ryul
    • Proceedings of the KIEE Conference
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    • 2009.07a
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    • pp.1122_1123
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    • 2009
  • Doubly Fed Induction Generator (DFIG) used in variable speed constant frequency wind energy generation system can capture wind energy with the highest efficiency by using the stator flux oriented vector control method. This paper sets up a DFIG modeling of wind generation system in PSCAD/EMTDC to simulate the operational performance with wind speed variation. In order to achieve the characteristics of the maximum utilization of wind power, this paper uses the vector control technology to track largest wind power and the independent control of generator active and reactive power.

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Simulink-based Modelling and Simulation for a Single-phase UPFC (Simulink를 이용한 단상 UPFC 모델링 및 시뮬레이션)

  • Kang, Moon-Ho
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.3
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    • pp.523-530
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    • 2009
  • This paper presents a study on a small scale single-phase UPFC preliminary researches on power quality compensating schemes of electrical railway. As the UPFC is very complicated power-electronic system consisting of grid-connected transformers, four single phase inverters interconnected with dc-link capacitors and various electrical apparatuses, multiple controllers and control algorithms are needed, and entire UPFC has been modelled in the form of block diagrams and simulated by using Simulink. The main purpose of the compensating system is to manage reactive and active powers with the four single phase inverters, so, the control effort has been focused on the power flow control and has been realized through the hysteresis current control of the single phase inverters. And transport-delayed PLL with additional delay-time compensating term has been used to synchronize a grid voltage and the simulation results have shown that the compensating term could improve PLL performance under some frequency variation of the voltage.

A study on the DC Capacitor Voltage control of 5 Level Inverter for Static Var Compensator (자려식 SVC용 5레벨 인버터의 직류측 콘덴서 전압제어에 관한 연구)

  • Kim, Jong-Yun;Harada, Hedehoro;Lyu, Sung-Kak;Oh, Jin-Suck;Kim, Yoon-Sik;Noh, Chang-Joo
    • Proceedings of the KIEE Conference
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    • 1998.07f
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    • pp.1899-1901
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    • 1998
  • A five-level VSI(Voltage Source Inverter) is introduced as a SVC(Static Var Compensator) like a large scale power source. The problems in using SVC are that the power device can easily be destroyed by voltage unbalance and accurate reactive power control is difficult because of voltage variation. A asymmetrical PAM(Pulse Amplitude Modulation) switching pattern is proposed to solve this problem and analyze both fundamental component and harmonic current in the system. Through experimental results of 3.5 kVA experimental test system. It is confirmed that DC capacitor voltage can be controlled by asymmetrical PAM switching pattern control.

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Parallel Operation Control Technique of On-line UPS System (온라인 무정전전원장치의 병렬운전 제어기술)

  • Cho J.S.;Kang B.H.;Gho J.S.;Choe G.H.;Kim J.H.;Chung S.E.
    • Proceedings of the KIPE Conference
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    • 2001.07a
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    • pp.501-505
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    • 2001
  • The parallel operation system of UPS is used to increase reliability of power source at critical load. But parallel UPS system has a few defects, impedance is different from each other and circulating current occurs between UPSs, due to line impedance and parameter variation, though controlled by the same synchronization signal. According to such characteristic of parallel UPS, balanced load-sharing control is the most important technique in parallel UPS operation. In this paper, a novel power deviation compensation algorithm is proposed. it is composed of voltage controller to compensate power deviation that be calculated by using active and reactive current deviation between inverters on synchronous d-q reference frame.

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Fabrication and Characteristics of InP-Waveguide (InP 광도파로의 식각 특성)

  • 박순룡;김진우;오범환;우덕하;김선호
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2000.07a
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    • pp.824-827
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    • 2000
  • Fabrication of InP-based photonic devices by dry etch Process is important for clear formation of waveguide mesa structure. We have developed more efficient etch process of the inductively coupled plasma (ICP) with low damages and less polymeric deposits for the InP-based photonic devices than the reactive ion etching (RIE) technique. We report the tendency of etch rate variation by the process parameters of the RF power, pressure, gas flow rate, and the gas mixing ratio. The surface roughness of InP-based waveguide structure was more improved by the light wet etching in the mixed solution of H$_2$SO$_4$:H$_2$O (1:1)

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