• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.36-41
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• 2003

This paper presents the results of power spectra using the fundamental and low frequency harmonic components of leakage current waveform to study aging on contaminated EPDM insulator(was serviced during 1997-2001, region Pohang, korea) under salt fog conditions. Experiments have been conducted in the chamber salt fog and at the 16KVrms. The salt contents adjusted as 0g,25g,50g and 75g per liter of deionized water. The onset of dry-band arcing on polymer insulators could be determined by signal processing the low frequency harmonics components. A correlation has been found between the fundamental and low harmonic components of power spectra on leakage current. Where aging could be associated with an increase in the level of both the fundamental and low frequency harmonics components of leakage current. Surface aging for contaminated EPDM insulators occurred when the fundamental component of leakage current was greater then some level On the other hand, when the polymer insulator approached failure, the fundamental component of leakage current reached relatively high values and low frequency harmonics components of the leakage current trended to decrease. The results suggest that both the fundamental and low frequency harmonics of leakage current can be used as a tool to determine both the beginning of aging and before flashover, end of life EPBM insulator in salt fog.

• Journal of Electrical Engineering and Technology
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• 제6권2호
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• pp.239-244
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• 2011

Industrial power distribution system includes many kinds of non-linear loads, which produce the harmonics during energy conversion transition. The single-tuned passive filter is widely used to absorb the harmonics and attenuate its undesirable effect in the distribution system. However, the passive filter might be severely stressed, and sometimes even damaged, due to the absorption of harmonics. There is voltage rise on the capacitor when the single-turned harmonic filter is applied. When the capacitor voltage rose above the allowable limit, the expected life of the capacitor will considerably deteriorate. On the other hand, the reactor can experience the spike voltage even if the voltage and current of the capacitor are within the allowable limit, and this accumulated voltage stress of the reactor causes its premature fault. In this paper, we analyzed and compared the harmonic voltage and current of the reactor and capacitor in a single-tuned harmonic filter through the EMTP software and verified them with the experimental results.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1999년도 춘계학술대회 논문집
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• pp.322-327
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• 1999

In most railway vehicle applications, a single phase AC/DC converter is used greatly and is essential equipment for Korea High Speed Train. A diode bridge rectifier and a phase-controlled thyristor bridge rectifier generate harmonics in power system. Nowadays, power factor and harmonics become major issue in electrical equipment for railway vehicle. Many researchers have been trying to improve the power factor and ac-side harmonics. Therefore the PWM converter is used to operate at unity Power factor and to reduce ac-side current harmonics. This paper describes the circuit for AC/DC PWM converter of Korea High Speed Train and proposes control algorithm to realize the sinusolidal input current waveform and the effective unity power factor. The validity of the proposed control method is verified through the experimental result.

• Journal of Power Electronics
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• 제16권3호
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• pp.960-969
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• 2016

High-power three-level voltage-source converters are widely utilized in high-performance AC drive systems. In several ultra-power instances, the harmonics on the grid side should be reduced through multiple rectifications. A combined harmonic elimination method that includes a dual primary-side series-connected winding transformer and selective harmonic elimination pulse-width modulation is proposed to eliminate low-order current harmonics on the primary and secondary sides of transformers. Through an analysis of the harmonic influence caused by dead time and DC magnetic bias, a synthetic compensation control strategy is presented to minimize the grid-side harmonics in the dual primary side series-connected winding transformer application. Both simulation and experimental results demonstrate that the proposed control strategy can significantly reduce the converter input current harmonics and eliminates the DC magnetic bias in the transformer.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 A
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• pp.267-269
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• 2004

Recently, due to increasing the application of power electronic equipment, harmonics generated from the non-liner load are fairy produced. Harmonics can cause a distribution problems such as the overheating of distribution transformer, the breakdown of device and communication interference. Interest about power quality decline of distribution system is very increased. In this paper, we are measured the harmonic voltage and current of distribution system to analyze harmonic characteristics, and it is analyzed Total Harmonic Distortion(HTD). Also, we are modeled distribution system using PSCAD/EMTDC. And it is analyzed harmonic voltage and current in steady-state. The study result have been indicated the utility about harmonics analysis and modeling for distribution system.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1998년도 추계학술대회 논문집
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• pp.219-225
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• 1998

A Diode bridge rectifier and a phase-controlled thyristor bridge rectifier generate harmonics in power system. Nowadays, power factor and harmonics are important performance in electrical equipment for railway vehicle. Many researchers have been trying to improve the power factor and ac-side harmonics. Therefore the PWM converter has been used to operate at unity power factor and to reduce ac-side current harmonics. This paper proposes the synchronization loop by vector product in single-phase PWM converter. The proposed control method can realize the sinusolidal input current waveform and the effective unity power factor. The validity of the proposed control method is verified through the experimental result.

• Journal of Power Electronics
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• 제16권5호
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• pp.1964-1980
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• 2016

This paper presents a new simplified harmonics extraction algorithm based on the synchronous reference frame (SRF) for an indirect current controlled (ICC) three-level neutral point diode clamped (NPC) inverter-based shunt active power filter (SAPF). The shunt APF is widely accepted as one of the most effective current harmonics mitigation tools due to its superior adaptability in dynamic state conditions. In its controller, the SRF algorithm which is derived based on the direct-quadrature (DQ) theory has played a significant role as a harmonics extraction algorithm due to its simple implementation features. However, it suffers from significant delays due to its dependency on a numerical filter and unnecessary computation workloads. Moreover, the algorithm is mostly implemented for the direct current controlled (DCC) based SAPF which operates based on a non-sinusoidal reference current. This degrades the mitigation performances since the DCC based operation does not possess exact information on the actual source current which suffers from switching ripples problems. Therefore, three major improvements are introduced which include the development of a mathematical based fundamental component identifier to replace the numerical filter, the removal of redundant features, and the generation of a sinusoidal reference current. The proposed algorithm is developed and evaluated in MATLAB / Simulink. A laboratory prototype utilizing a TMS320F28335 digital signal processor (DSP) is also implemented to validate effectiveness of the proposed algorithm. Both simulation and experimental results are presented. They show significant improvements in terms of total harmonic distortion (THD) and dynamic response when compared to a conventional SRF algorithm.

• 전기학회논문지
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• 제66권8호
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• pp.1291-1296
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• 2017

Single-phase and three-phase load can be used together in 3-phase 4-wire system. Single-phase and three-phase loads can be classified as linear loads without harmonics and nonlinear with harmonics. Single-phase linear loads are linear loads such as lamps and heat, and single-phase nonlinear loads are power converters such as rectifiers. It is recommended that the distribution of loads in the 3-phase, 4-wire distribution lines be evenly distributed within a certain range. However, harmonic currents generated in a nonlinear load flow on the neutral line and affect the phase current magnitude. The difference in the magnitude of the individual phase current due to the influence of the harmonic current present in the neutral line can produce a difference in current and load unbalance. In this study, current unbalance ratio and load unbalance ratio which can occur when a combination of linear and nonlinear loads are applied to 3-phase 4-wire distribution line are calculated.

• 조명전기설비학회논문지
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• 제19권1호
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• pp.155-161
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• 2005

사무용 빌딩의 비선형 전자부하에 기인한 전압 및 전류파형의 왜곡은 중성선의 과열, 변압기 손실, 누전차단기 오동작 등을 야기 시킨다. 본 논문에서는 사무용 빌딩에서의 전압 및 전류 고조파의 크기, 전압 및 전류 파고율(Crest Factor : CF), 전압 및 전류 불평형 등을 비교함으로써 파형왜곡 특성을 분석하였다. 분석 결과, 고조파에 의한 상 및 중성선에서의 심각한 파형 왜곡 문제와 삼상에서의 단상 부하의 부적절한 분배로 인한 전류 불평형이 심한 빌딩이 조사되었다. 본 연구 결과는 사무용 빌딩에서 합리적이고 경제적인 부하운용을 위해 사용될 수 있을 것이다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.111-114
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• 2000

Harmonics and fundamental reactive power of nonlinear loads in serious unbalanced power condition are compensated by current synchronous detection(CSD) theory which is also acceptable for single phase power system, but the CSD theory is not suitable any more in case of controlled independently harmonics and reactive component. Therefore a new algorithm the extended current synchronous detection (ECSD)theory for a three phase active power filter based on decomposition of fundamental reactive distorted components is proposed in this paper. The proposed ECSD theory is simulated and tested comparison with a few power theories under asymmtrical condition in power system.