• Title, Summary, Keyword: Total Demand Distortion(TDD)

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Harmonics Assessment for an Electric Railroad Feeding System using Moments Matching Method (모멘트 정합 방법(Moment Matching Method)을 이용한 전기철도 급전시스템의 고조파 평가)

  • Lee, Jun-Kyong;Lee, Seung-Hyuk;Kim, Jin-O
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.56 no.1
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    • pp.1-7
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    • 2007
  • Generally, an electric railroad feeding system has many problems due to the different characteristics in contrast with a load of general three-phase AC electric power system. One of them is harmonics problem caused by the switching device existing in the feeding system, and moreover, the time-varying dynamic loads of rail way is inherently another cause to increase this harmonics problem. In Korea power systems, the electric railroad feeding system is directly supplied from the substation of KEPCO. Therefore, if voltages fluctuation or unbalanced voltages are created by the voltage and current distortion or voltage drop during operation, it affects directly the source of supply. The trainloads of electric railway system have non-periodic but iterative harmonic characteristics as operating condition, because the electric characteristic of the electric railroad feeding system is changed by physical conditions of the each trainload. According to the traditional study, the estimation of harmonics has been performed by deterministic way using the steady state data at the specific time. This method is easy to analyze harmonics, but it has limits in some cases which needs an assessment of dynamic load and reliability. Therefore, this paper proposes the probabilistic estimation method, moments matching method(MW) in order to overcome the drawback of deterministic method. In this paper, distributions for each harmonics are convolved to obtain the moments and cumulants of TDD(Total Demand Distortion), and this can be generalized for any number of trains. For the case study, the electric railway system of LAT(Intra Airport Transit) in Incheon International Airport is modeled using PSCAD/EMTDC dynamic simulator. The raw data of harmonics for the moments matching method is acquired from simulation of the LAT model.

Assessment on Power Quality of Grid-Connected PV System Based on Incremental Conductance MPPT Control (증분컨덕턴스 MPPT제어 기반 계통연계형 태양광발전시스템의 전력품질 평가)

  • Seol, Jae-Woong;Jang, Jae-Jung;Kim, Dong-Min;Lee, Seung-Hyuk;Kim, Jin-O
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.56 no.1
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    • pp.8-13
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    • 2007
  • During the last years, there has been an increased interest in the new energy such as photovoltaic(PV) system from the viewpoint of environmental pollution. In this regard, this paper estimates the power quality of grid-connected PV system. As the maximum power operating point(MPOP) of photovoltaic(PV) power systems alters with changing atmospheric conditions, the efficiency of maximum power point tracking(MPPT) is important in PV power systems. Moreover, grid-connected PV system occurs some problems such as voltage inequality and harmonics. Therefore, this paper presents the results of a grid-connected PV system modeling that contains incremental conductance MPPT controller by PSCAD/EMTDC simulator and investigates the influence that can occur in the grid-connected PV system from aspect of power quality, i.e. voltage drop, total harmonic distortion(TDD) and total demand distortion(TDD). For the case study, the measured data of the PV way in Cheongwadae, Seoul, Korea is used.

Probabilistic Method for The Harmonic Analysis of Railroad Feeding System (철도급전시스템의 고조파 평가를 위한 확률론적 방법)

  • Lee, Seung-Hyuk;Song, Hak-Seon;Lee, Jun-Kyong;Kim, Jin-O
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.55 no.9
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    • pp.384-391
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    • 2006
  • The harmonic currents generated along with the operating speed of electrical railroad traction are very difficult to analyze because of its nonlinear characteristics. This paper therefore presents probabilistic approach for the evaluation of harmonic currents about the operating speed of the arbitrary single traction. To use probabilistic method for railroad system, PDF(Probability Density Function) using measuring data based on the realistic h 따 monic currents per operating speed is calculated. Measuring data of harmonic current per operating speed is obtained using the result data of PSCAD/EMTDC dynamic simulation based on an IAT(Intra Airport Transit) in Incheon International Airport. The means(expected values) and variances of harmonic currents of single traction also are obtained by the PDF of the operating traction speed and harmonic currents. The uncertainty of harmonic currents can be calculated through the mean and variance of PDF. The probability of harmonic currents generated with the operating of arbitrary many tractions is calculated by the convolution of functions. The harmonics of different number of tractions are systematically investigated to assess the TDD(Total Demand Distortion) for the railroad system. The calculation of TDD was carried out using Monte-Carlo Simulations(MSCs) and the results of TDD evaluation of the power quality in the IAT power feeding system.

Source Model for Harmonic Interaction Analysis between Renewable Energy Generators and Power Distribution System (계통 고조파와 분산형 전원의 상호작용 평가를 위한 고조파 모델에 관한 연구)

  • Cho, Sung-Min;Shin, Hee-Sang;Moon, Won-Sik;Kim, Jae-Chul
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.60 no.4
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    • pp.733-738
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    • 2011
  • As increase of nonlinear loads and renewable energy generators (REGs) being connected to power distribution system via inverters, the concern on harmonic problems have increased. Recently, the harmonics evaluation method considering TDD (Total Demand Distortion) is used to analyze the effect of harmonics from inverters on power distribution quality. Harmonic current sources are typically used for simulation of nonlinear load. Most inverter type for REGs is voltage source inverter (VSI). So, harmonic voltage sources are more suitable to analyze impact of renewable energy generator on harmonics problem in power distribution system. In this paper, we presented the circuit model to analyze interaction between harmonics from nonlinear load and REGs. We verified that the harmonic analysis using the proposed circuit model is more appropriate than the harmonics evaluation method considering TDD through case study using PSCAD/EMTDC.

Harmonics Analysis of Railroad Systems using Markov Chain (Markov Chain을 이용한 철도계통의 고조파 분석)

  • Song, Hak-Seon;Lee, Seung-Hyuk;Kim, Jin-O;Kim, Hyung-Chul
    • Proceedings of the KIEE Conference
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    • pp.230-233
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    • 2005
  • This paper proposes power qualify assessment using Markov Chain applied to Ergodic theorem. The Ergodic theorem introduces the state of aperiodic, recurrent, and non-null. The proposed method using Markov Chain presents very well generated harmonic characteristics according to the traction's operation of electric railway system. In case of infinite iteration, the characteristic of Markov Chain that converges on limiting probability Is able to expected harmonic currents posterior transient state. TDD(Total Demand Distortion) is also analyzed in expected current of each harmonic. The TDD for power quality assesment is calculated using Markov Chain theory in the Inceon international airport IAT power system.

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A Study on the Harmonics of Distribution Power System Interconnected with Distributed Generation (분산전원의 배전계통 연계 시 발생하는 고조파에 관한 연구)

  • Park, Jae-Gyun;Kim, Jin-Sung;Oh, Yong-Taek
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.11 no.1
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    • pp.73-78
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    • 2010
  • In this paper, the analysis of the harmonics of distribution power system interconnected with DG(distributed generation) is simulated by using PSCAD/EMTDC and evaluated the harmonics. The modeling system for simulation is similar to the actual distribution system, and solar power system. The simulation analyses are performed at connection points for each sector. Harmonic standards of interconnection with DG (IEEE Std 1547 and IEEE Std 519) are applied to the evaluation algorithm, converted the simulated data through FFT method, evaluated by THD and TDD separately. The harmonic contents in the case of without DG and each sector with DG are evaluated and compared. The results of evaluation showed the effect that the harmonic contents are appropriated at all sector with DG (without DG) in the distribution power systems but the large induction motor(50KW) is increased the harmonic contents.

Power Quality Assessment and PSCAD/EMTDC Modeling of Grid-Connected PV System (계통연계형 태양광발전시스템의 PSCAD/EMTDC 모델링 및 전력품질 평가)

  • Seol, Jae-Woong;Jang, Jae-Jung;Kim, Jin-O
    • Proceedings of the KIEE Conference
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    • pp.2193-2194
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    • 2006
  • This paper presents the results of a grid-connected photovoltaic (PV) system modeling that contain incremental conductance MPPT(Maximum Power Point Tracking) controller by PSCAD/EMTDC simulator and investigates the influence that can occur in the grid-connected PV system from aspect of power quality, i.e. voltage drop, total harmonic distortion(THD) and total demand distortion(TDD). The measured data the PV array modeling of PSCAD/EMTDC in Cheongwadae, Seoul, Korea is used in the paper.

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Power Quality Assessment and PSCAD/EMTDC Modeling of Grid-Connected PV System (계통연계형 태양광발전시스템의 PSCAD/EMTDC 모델링 및 전력품질 평가)

  • Seol, Jae-Woong;Jang, Jae-Jung;Kim, Jin-O
    • Proceedings of the KIEE Conference
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    • pp.561-562
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    • 2006
  • This paper presents the results of a grid-connected photovoltaic(PV) system modeling that contain incremental conductance MPPT(Maximum Power Point Tracking) controller by PSCAD/EMTDC simulator and investigates the influence that can occur in the grid-connected PV system from aspect of power Quality, i.e. voltage drop, total harmonic distortion(THD) and total demand distortion(TDD) The measured data the PV array modeling of PSCAD/EMTDC in Cheongwadae, Seoul, Korea is used in the paper.

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Power Quality Assessment and PSCAD/EMTDC Modeling of Grid-Connected PV System (계통연계형 태양광발전시스템의 PSCAD/EMTDC 모델링 및 전력품질 평가)

  • Seol, Jae-Woong;Jang, Jae-Jung;Kim, Jin-O
    • Proceedings of the KIEE Conference
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    • pp.1687-1688
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    • 2006
  • This paper presents the results of a grid-connected photovoltaic (PV) system modeling that contain incremental conductance MPPT(Maximum Power Point Tracking) controller by PSCAD/EMTDC simulator and investigates the influence that tan occur in the grid-connected PV system from aspect of power quality, i.e. voltage drop, total harmonic distortion(THD) and total demand distortion(TDD). The measured data the PV array modeling of PSCAD/EMTDC in Cheongwadae, Seoul, Korea is used in the paper.

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Power Quality Assessment and PSCAD/EMTDC Modeling of Grid-Connected PV System (계통연계형 태양광발전시스템의 PSCAD/EMTDC 모델링 및 전력품질 평가)

  • Seol, Jae-Woong;Jang, Jae-Jung;Kim, Jin-O
    • Proceedings of the KIEE Conference
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    • pp.1227-1228
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    • 2006
  • This paper presents the results of a grid-connected photovoltaic(PV) system modeling that contain incremental conductance MPPT(Maximum Power Point Tracking) controller by PSCAD/EMTDC simulator and investigates the influence that can occur in the grid-connected PV system from aspect of power quality, i.e. voltage drop, total harmonic distortion(THD) and total demand distortion(TDD). The measured data the PV array modeling of PSCAD/EMTDC in Cheongwadae, Seoul, Korea is used in the paper.

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