• 제목/요약/키워드: Unbalanced load current

검색결과 113건 처리시간 0.024초

초전도 전력케이블의 전류 불평형에 관한 연구 (A Study on the Unbalanced Current Distribution of HTS Power Cable)

  • 김재호;박충화
    • 한국안전학회지
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    • 제27권6호
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    • pp.43-47
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    • 2012
  • The unbalance currents flow the High Temperature Superconducting (HTS) power cable caused by asymmetrical fault, harmonic distortion and unbalanced load. That problem causes additional loss and leakage field in the HTS power cable, and deteriorates the electric power quality and stability. In addition, large amounts of unbalanced current can cause negative sequence and ground relays to operate. This paper presents an analysis unbalanced three-phase current distribution in HTS power cable caused by unbalanced load condition and grounding methods using PSCAD/EMTDC. The results obtained through the analysis would provide important data for the design of HTS power cables and valid information for their installation in power system.

전류 고조파와 불평형 전원 전압을 보상하는 직렬형 능동전력 필터와 병렬형 수동전력필터 병용시스템의 새로운 제어법 (A Novel Control Method of Combined System consists of Series Active Power Filter and Parallel Passive Power Filter to Compensate Current Harmonics and Unbalanced Source Voltages)

  • 오재훈;한윤석;김영석;원충연;최세완
    • 대한전기학회논문지:전기기기및에너지변환시스템부문B
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    • 제50권12호
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    • pp.615-623
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    • 2001
  • In this paper, we study a series active power filter to compensate current harmonics and unbalanced source voltages. Conventional control methods for compensating unbalanced source voltages use source voltages to calculate compensation voltages, and in addition use load voltages to regulate load voltages. But the proposed control method uses load voltage to compensate unbalanced source voltages and regulate load voltages. And we propose a control method to reduce current harmonics which can calculate compensation voltages directly from source currents and load voltages. By well-matched operation of two control methods, the series active power filter can compensate current harmonics, unbalanced source voltages, and regulate load voltages. We compose a combined system of the series active power filter and parallel passive filters to confirm a validity of proposed control methods. The results from experiments are presented to demonstrate effectiveness of the proposed method.

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부하 변동에 의한 전압불평형율의 특성 해석 (Analysis on the Characteristics of Voltage Unbalance Factor by Load Variations)

  • 김종겸;박영진;이은웅
    • 전기학회논문지P
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    • 제54권1호
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    • pp.47-53
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    • 2005
  • Most of the loads in industrial power distribution systems are balanced and connected to three power systems. However, in the user power distribution systems, most of the loads are single & three phase and unbalanced, generating voltage unbalance. Voltage unbalance factor is mainly affected by load system rather than stable power system. Unbalanced voltage will draw a highly unbalanced current. As a result, the three-phase currents may differ considerably, thus resulting in an increased temperature rise in the machine. This paper presents a scheme on the characteristics of voltage and current unbalance factor under the load variation at the three phase 4-wire system. Load unbalance factor is measured by the power quality measurement apparatus and compared by the current unbalance factor. Two methods are indicated similar results. The voltage unbalance factor of the three-phase 4-wire system is approved by the field measurement. Each phase has an impedance each other by the unbalanced operation pattern and give rise to voltage unbalance.

VAR 시스템에 의한 3 상 불평형 부하의 무효전력 보상에 관한 연구 (A STUDY ON THE REACTIVE POWER COMPENSATION OF THREE PHASE UNBALANCED LOAD FOR VAR SYSTEM)

  • 정연택;서영수;김영봉;김한수;이봉주
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1989년도 하계종합학술대회 논문집
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    • pp.531-534
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    • 1989
  • In this paper, the way that input voltage and input line current as a control variable is provided as one unit is projected. Till no, have denied with three phase balanced load. But, in that case, total power factor compensation is difficult, for to control each phase at unbalanced load. Therefor, in this paper suggest of the scheme that three phase unbalanced load is controlled by each phase and input total power factor is compensated unit input factor. therefore, in this paper suggest that three phase unbalanced load is controlled and the method in compensation of unit input factor to be attended by unbalanced load. Besides, the object of control is calculating quantity for input voltage and input line current for the point at issuse make to improve of control method at unbalanced load. As a result, control system of each phase could maintain as a unit input total power factor has been state diviation error of 2% with unbalanced load.

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부하 불평형율에 대한 새로운 해석 (A New Analysis for Load Unbalance Factor)

  • 김종겸
    • 전기학회논문지P
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    • 제55권2호
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    • pp.67-72
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    • 2006
  • Most of the load distributions in low voltage power feeder distribution systems are designed with approximately balanced and connected at the three phase four wire systems. However, in the user power distribution systems, most of the loads are single & three phase and unbalanced, generating load unbalance. Load unbalance factor is mainly affected by the impedance of load system. Unbalanced current will draw a highly unbalanced voltage. This paper presents a new calculation method for unbalance factor under the load variation at the three phase four wire system. Load unbalance factor is measured by the power quality measurement apparatus and compared with the current unbalance factor. Two methods are indicated similar results.

The Harmonic Current Mitigation of DFIG under Unbalanced Grid Voltage and Non-linear Load Conditions

  • Thinh, Quach Ngoc;Kim, Eel-Hwan
    • 전력전자학회:학술대회논문집
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    • 전력전자학회 2011년도 전력전자학술대회
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    • pp.83-84
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    • 2011
  • This paper presents an analysis and a novel strategy for a doubly fed induction generator (DFIG) based wind energy conversion system under unbalanced grid voltage and non-linear load conditions. A proportional-resonant (PR) current controller is applied in both grid side converter (GSC) and rotor side converter (RSC). The RSC is controlled to mitigate the stator active power and the rotor current oscillations at double supply frequency under unbalanced grid voltage while the GSC is controlled to mitigate ripples in the dc-link voltage and compensate harmonic components of the network current. Simulation results using Psim simulation program are presented for a 2 MW DFIG to confirm the effectiveness of the proposed control strategy.

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불평형부하를 가지는 다단 H-bridge STATCOM에서 상간 직류전압 불평형의 제어 (Control of DC-side Voltage Unbalance among Phases in Multi-level H-Bridge STATCOM with Unbalanced Load)

  • 권병기;정승기;김태형
    • 전력전자학회논문지
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    • 제19권4호
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    • pp.332-341
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    • 2014
  • A cascaded H-bridge multi-level STATCOM(STATic synchronous COMpensator), which is composed of many cell inverters with independent dc-sources, generates inevitably dc-side voltage unbalance among phases when it compensates unbalanced load. It comes from the difference of flowing active power in each phase when this compensator makes negative-sequence current to eliminate the unbalance of source-side current. However, this unbalance can be controlled by injecting zero-sequence current which is decoupled with grid currents, so the compensator can work well during this balancing process. Both a feedback control algorithm, which produces zero-sequence current proportional to dc-side voltage unbalance within each phase, and a feedforward control algorithm, which makes zero-sequence current directly from the compensator's negative-sequence current, were proposed. The dc-side voltage of each phase can be controlled stably by these proposed algorithms in both steady-state and transient, so the compensator can have fast response to satisfy control performance under rapid changing load. These balancing controllers were implemented and verified via simulation and experiment.

계통연계 인버터의 주요 부하 불평형 시 상전류 제어를 통한 부하 상전압 평형 제어 (An Output Voltage Balance Control of Grid Connected Inverter by Phase Current Control at Critical Load Unbalanced Condition)

  • 박태현;김학원;조관열;민준기;최원일
    • 전력전자학회논문지
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    • 제28권1호
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    • pp.22-29
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    • 2023
  • A grid-connected inverter can be used in grid-connected or stand-alone modes. Generally, a grid-connected inverter operates in a grid-connected mode, but the inverter operates in stand-alone mode if grid faults occur. In the stand-alone mode, the grid-connected inverter must supply electric power to a critical load that needs to receive stable power even though grid faults occur. Generally, three-phase loads are used as critical loads, but a single phase is configured in some cases. In these conditions, the critical load is required to unbalance the load power consumption, which makes the three-phase load voltage unbalancd. This unbalanced voltage problem can cause fatal problems to the three-phase critical loads, and thus must be addressed. Hence, this paper proposes an algorithm to solve this unbalanced voltage problem by the individual phase current control. The proposed method is verified using Psim simulation and experiments.

PSCAD/EMTDC를 이용한 불평형 부하에서의 초전도 케이블의 운전특성 해석 (A Operated Characteristic Analysis of HTS Cable in Unbalanced Load Using PSCAD/EMTDC)

  • 이현철;황시돌;이근준
    • 전기학회논문지
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    • 제57권10호
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    • pp.1713-1719
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    • 2008
  • A high temperature superconducting power cable (HTS power cable) was applied large current capacity by no resistance in normal state. Fault state was risen out of over-current but, it was limited to resistance. This study was modeling equivalence, and unbalanced state analyzed operating characteristic of HTS power cable. The equivalence model was composed superconductor, shield, and former part. This model simulation was appeared conductor and shield current in normal state, but unbalanced state was appeared former current as rise current by resistance. So it need to sufficiently influenced the quench characteristic when the former design.

불평형보상용 STATCOM의 역상분 전류 검출을 위한 디지털 버터워쓰 필터 (The Digital Butterworth Filter of STATCOM for detecting negative sequence components of Unbalanced Load currents)

  • 임수생;이은웅;손홍관;김석곤;김준호
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2000년도 추계학술대회 논문집 학회본부 B
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    • pp.333-335
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    • 2000
  • STATCOM(static synchronous compensator : one of the custom power equipment) can be used for balancing unbalanced loads. Compensation current references are given by the analysis of the unbalanced 3-phase currents. And for detecting negative-sequence components, a digital Butterworth Filter is designed. Finally a negative sequence component of an unbalanced load current is acquired using the digital Butterworth Filter.

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