• Title/Summary/Keyword: Low voltage Operation

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Analysis on the Operation Characteristics of Induction Motor Operated by Unbalanced Voltage with Harmonics Components (고조파 성분이 포함된 전압 불평형 운전시 유도전동기의 동작 특성 해석)

  • Kim, Jong-Gyeum;Park, Young-Jeen;Lee, Eun-Woong
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.54 no.3
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    • pp.134-140
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    • 2005
  • Most of the loads in industrial power distribution systems are usually balanced and connected to three power systems. However, in the user power distribution systems, partial loads are single & three phase and unbalanced, generating voltage unbalance by the impedance mismatching. Voltage unbalance has detrimental effects on three-phase induction motors, including over heating, line-current unbalance, derating, torque pulsation, low efficiency, etc. This paper presents a scheme on operation states of a three-phase induction motor under the unbalanced voltages with harmonics components. Three-phase voltages applied to the stator winding of the studied induction motor are controlled by respectively adjusting not only fundamental but also harmonics components. Harmonic components at the voltage unbalanced factor(VUF) of the three-phase source voltages can then be examined the different values of VUF on machine's operation characteristics.

A Study on Permissible Operation Limit of Distributed Generation System in Distribution System (배전계통에서 분산전원 운전가능 범위에 대한 연구)

  • Jung, Won-Jae;Kim, Tae-Eung;Kim, Jae-Eon
    • Proceedings of the KIEE Conference
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    • 2001.07a
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    • pp.19-21
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    • 2001
  • Nowadays, small scale DGS(Distributed Generation System), as a wind power generation or photovoltaic generation, becomes to be introduced into the power distribution system. But in that case it is difficult to properly maintain the terminal voltage of low voltage customers by using only LDC(Line Drop Compensator). So, it is necessary to determine the permissible operation limit of the introduced DGS for proper voltage in distribution system. In this paper clarifies the relationship between LDC voltage regulation principle and real, reactive power of DGS, and examines the permissible operation limit of the introduced DGS in distribution system which the voltage is controlled by LDC.

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A Study on the Efficiency Improvement of Induction Motor with AC Voltage Controller (교류 전압 제어기에 의한 유도전동기의 효율 개선에 관한 연구)

  • Lee, Seung-Chul;Jeong, Seung-Gi
    • Proceedings of the KIEE Conference
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    • 1991.11a
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    • pp.137-139
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    • 1991
  • This paper proposes a minimum power factor control for maximum efficiency operation of an induction motor, under low load condition. Minimum input or maximum efficiency operation is achived by properly adjusting the amplitude of the stator voltage, with the three phase AC voltage controller. Through the simulation, the relationships between the delay angle and input power under various load conditions are examined. Experimental results are also given, which show good coincidence with the simulation results.

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AN OBSERVER-BASED DTC OF INDUCTION MOTORS DRIVEN BY 3-LEVEL INVERTER FOR IMPROVING LOW SPEED OPERATION (3 레벨 인버터로 구동되는 유도전동기 직접 토크제어의 저속운전 성능 개선)

  • Yun, J.H.;Choi, S.K.;Lee, S.H.;Lee, K.B.;Yoo, J.Y.;Song, J.H.;Choi, I.
    • Proceedings of the KIEE Conference
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    • 2000.07b
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    • pp.1030-1032
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    • 2000
  • Direct torque control algorithm for 3-level inverter-fed induction motors is proposed. Conventional selection method of the stator voltage vector shows problems of stator flux drooping phenomenon and undesirable torque control appeared especially at the low, speed operation. To overcome these problems, a proposed method uses intermediate voltage vectors, which are inherently generated in 3-level inverters. An adaptive observer is also employed to estimate some state-variables and motor parameters, which takes a deep effect on the performance of the low speed operation. Simulation and experiment results verify effectiveness of the proposed algorithm.

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Electric Safety Protection Device of High Speed for Incapable Operation of ELB and MCCB Using the Low Voltage Distribution Line (저압 배전선로의 누전 및 배선용 차단기의 오동작 방지를 위한 고속형 전기안전 보호장치)

  • Kwak, Dong-Kurl;Jung, Do-Young
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.56 no.11
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    • pp.1925-1929
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    • 2007
  • This paper is studied on a novel Electric Safety Protection Device (ESPD) of high speed for incapable operation of Earth Leakage Circuit Breaker (ELB) and Molded_case Circuit Breaker (MCCB) using the low voltage distribution line. The major causes of electrical fire are classified to short circuit fault, overload fault, electric leakage and electric contact failure. The occurrence factor of the fire is electric arc or spark accompanied with electrical faults. Residual Current Protective Device (RCD), that is ELB and MCCB, of high sensitivity type used at low voltage wiring cuts off earth leakage and overload, but the RCD can't cut off electric arc or spark to be a major factor of electrical fire. As the RCDs which are applied low voltage distribution panel are prescribed to rated breaking time about 30[ms] (KS C 4613), the RCDs can't perceive to the periodic electric arc or spark of more short wavelength level. To be improved on such problem, this research development is proposed to a novel ESPD of high speed to trip of distribution line on electric arc or spark due to electrical fire. Some experimental results of the proposed ESPD are confirmed to the validity of the analytical results.

A Study on the Design of the Voltage Down Converter for Low Power, High Speed DRAM (DRAM의 저전력, 고속화에 따른 VDC 설계에 관한 연구)

  • 주종두;곽승욱
    • Proceedings of the IEEK Conference
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    • 1998.10a
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    • pp.707-710
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    • 1998
  • This paper presents a new voltage down converter(VDC) for low power, high speed DRAM. This VDC Consists of RVG(Reference Voltage Generator) and Driver Circuit. And it is independent of temperature variation, and Supply Voltage. Using weak inversion region, this RVG dissipates low power. Internal Voltage Source of this VDC is stable in spite of high speed operation of memory array. This circuit is designed with a $0.65\mu\textrm{m}$ nwell CMOS technology. In HSPICE simulation results, Temperature dependency of this RVG is $20\muV/^{\circ}C,$ supply voltage dependency is $\pm0.17%,$ $VCC=3.3V\pm0.3V,$ and current dissipation is $5.22\muA.$ Internal voltage source bouncing of this VDC is smaller than conventional VDC.

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Improved Flux and Torque Estimators of a Direct Torque Controlled Interior PM Machine with Compensations for Dead-time Effects and Forward Voltage Drops

  • Sayeef, Saad;Rahman, M.F.
    • Journal of Power Electronics
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    • v.9 no.3
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    • pp.438-446
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    • 2009
  • The performance of direct torque controlled (DTC) interior permanent magnet (IPM) machines is poor at low speeds due to a few reasons, namely limited accuracy of stator voltage acquisition and the presence of offset and drift components in the acquired signals. Due to factors such as forward voltage drop across switching devices in the three phase inverter and dead-time of the devices, the voltage across the machine terminals differ from the reference voltage vector used to estimate stator flux and electromagnetic torque. This can lead to instability of the IPM drive during low speed operation. Compensation schemes for forward voltage drops and dead-time are proposed and implemented in real-time control, resulting in improved performance of the space vector modulated DTC IPM drive, especially at low speeds. No additional hardware is required for these compensators.

Implementation of Dual Current Controller and Realtime Power Limiting Algorithm in Grid-connected Inverter during Unbalanced Voltage Conditions (전원 전압 불평형시 계통연계형 인버터의 유효전력 리플 억제를 위한 듀얼 전류제어기 구현과 출력 전력의 실시간 제한 알고리즘)

  • Song Seung-Ho;Kim Jeong-Jae
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.55 no.1
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    • pp.54-60
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    • 2006
  • A power limiting algorithm is proposed for stable operation of grid-connected inverter in case of grid voltage unbalance considering the operation limit of inverter. During the voltage unbalance the control performance of Inverter. is degraded and the output power contains 120Hz ripple due to the negative sequence of voltage. In this paper, conventional dual sequence current controller is implemented to solve these problems using separated control of positive and negative sequence. Especially the maximum power limit which guarantees the maximum rated current of the inverter is automatically calculated as the instant grid voltage changes. As soon as the voltage recovers the proposed algorithm can return to the normal power control mode accomplishing low voltage ride through. Proposed algorithm is verifed using PSCAD/EMTDC simulations and tested experimentally at 4.4kW wind turbine simulator set-up.

A Detection Method of Grid Voltage for Grid Support Operation of an Inverter-based Renewable Energy Generation System (인버터 기반 신재생 에너지 발전 시스템의 계통 지원 운전을 위한 계통 전압 검출 방법)

  • Ahn, Hyun-Chul;Song, Seung-Ho
    • New & Renewable Energy
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    • v.9 no.2
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    • pp.51-57
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    • 2013
  • The Grid code is being strengthen as increase of renewable energy ratio. Especially, the grid connection regulations are continuously being updated for stable operation of power grids. Static grid support and Dynamic grid support must make an accurate measure at Grid connected point because they needs control algorithm individually. It has to exactly measure voltage including switching ripple at the output of the inverter generating system. In addition, it is necessary to have an accurate voltage measurement when the situation rapidly changing the grid impedance is caused by the input of serial impedance of transformer and line impedance as well as Grid Fault Device. In this paper, We propose a new detection method of grid voltage to calculate accurately the r.m.s voltage of the grid connection point along the standard required by the low voltage regulation. We verified performance through simulation grid fault device.

Design and Development of a High-Voltage Transformer-less Power Supply for Ozone Generators Based on a Voltage-fed Full Bridge Resonant Inverter

  • Amjad, Muhammad;Salam, Zainal;Facta, Mochammad;Ishaque, Kashif
    • Journal of Power Electronics
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    • v.12 no.3
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    • pp.387-398
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    • 2012
  • It is known that transformer based power supplies for ozone generators have low efficiency, high cost and exhibits a limited frequency range of operation. To overcome these disadvantages, this paper proposes a high frequency ozone generator with the absence of a transformer. The voltage step-up is achieved only by utilizing the resonant tank. This is made possible by a novel combination of ozone chamber materials that allow ozone to be generated at only 1.5 - 3.5 $kV_{p-p}$. The input to the resonant tank is driven by a PWM full bridge resonant inverter. Furthermore, zero-current zero-voltage switching (ZCZVS) operation is achieved by employing a duty factor of 25% between the switches of the full bridge. The advantages of the proposed system include high efficiency, low cost and the ability to control ozone production by varying the input voltage to the inverter. The prototype is verified by both simulation and experimental results.