• Title/Summary/Keyword: Flux method

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An Improved Model Predictive Direct Torque Control for Induction Machine Drives

  • Song, Wenxiang;Le, Shengkang;Wu, Xiaoxin;Ruan, Yi
    • Journal of Power Electronics
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    • v.17 no.3
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    • pp.674-685
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    • 2017
  • The conventional model predictive direct torque control (MPDTC) method uses all of the voltage vectors available from a two level voltage source inverter for the prediction of the stator flux and stator current, which leads to a heavy computational burden. This paper proposes an improved model predictive direct torque control method. The stator flux predictive controller is obtained from an analysis of the relationship between the stator flux and the torque, which can be used to calculate the desired voltage vector based on the stator flux and torque reference. Then this method only needs to evaluate three voltage vectors in the sector of the desired voltage vector. As a result, the computational burden of the conventional MPDTC is effectively reduced. The time delay introduced by the computational time causes the stator current to oscillate around its reference. It also increases the current and torque ripples. To address this problem, a delay compensation method is adopted in this paper. Furthermore, the switching frequency of the inverter is significantly reduced by introducing the constraint of the power semiconductor switching number to the cost function of the MPDTC. Both simulation and experimental results are presented to verify the validity and feasibility of the proposed method.

Quantitative Study of CO2 based on Satellite Image for Carbon Budget on Flux Tower Watersheds (플럭스 타워 설치 유역을 대상으로 탄소수지 분석을 위한 위성영상자료기반의 CO2 정량화 연구)

  • Jung, Chung Gil;Lee, Yong Gwan;Kim, Seong Joon;Jang, Cheol Hee
    • Journal of The Korean Society of Agricultural Engineers
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    • v.57 no.3
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    • pp.109-120
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    • 2015
  • Spatial heterogeneous characteristics of solar radiation energy from Climate Change gives rise to energy imbalance in the general ecological system including water resources. This study is to estimate the $CO_2$ flux of South Korea using Terra MODIS image and to assess the reliability of MODIS data from the ground measured $CO_2$ flux by eddy covariance flux tower data at 3 locations (two at mixed forest area and one at rice paddy area). The MODIS Gross Primary Productivity (GPP) product (MOD17A2), 8-day composite at 1-km spatial resolution was adopted for the spatial $CO_2$ flux generation. The MOD17A2 data by noise like cloud and snow in a day were tried to fill by Inverse Distance Weighted (IDW) method from valid pixels and the damping effect of MOD17A2 data were corrected by Quality Control (QC) flag. The MODIS $CO_2$ flux was estimated as the sum of GPP and Re (ecosystem respiration) by Lloyd and Taylor method (1994). The determination coefficient ($R^2$) between MODIS $CO_2$ and flux tower $CO_2$ for 3 years (2011~2013) showed 0.55 and 0.60 in 2 mixed forests and 0.56 in rice paddy respectively. The $CO_2$ flux generally fluctuated showing minus values during summer rainy season (from July to August) and maintaining plus values for other periods. The MODIS $CO_2$ flux can be a useful information for extensive area, for example, as a reliable indicator on ecological circulation system.

A Study of Rotor Fault Detection for the Induction Motor Using Axial Leakage Magnetic Flux (축방향 누설자속 측정에 의한 유도전동기의 회전자 결함검출에 관한 연구)

  • Shin, Dae-Cheul;Kim, Young-Hwan
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.20 no.1
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    • pp.132-137
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    • 2006
  • The second part of paper related rotor failure is to evaluate that the axial magnetic flux measurement could be used as a tool of the condition monitoring system for the induction motor and to develope the diagnostic algorithm for the various fault in the electric motors. The magnetic leakage flux signal is captured by the flux coil located at the end of motor without the disturbance of the operation. And the signal is analyzed both time and frequency domain to detect the failure of the motor. Specific signature can be described in tin and frequency domain for each fault of the motor. The experimental test found that the rotor failures - broken rotor bar, broken end ing and rotor eccentricity, could be detected from the spectrum with high resolution. The method of detecting the rotor fault was found by analysing the specific frequency and the sideband of the rotor bar pass frequency from axial leakage flux spectrum. In addition the optimal flux coil and measuring equipment for the axial leakage flux measurement was verified and the diagnostic method for the detection of the rotor related failure was developed.

Evaluation of MODIS Gross Primary Production (GPP) by Comparing with GPP from CO2 Flux Data Measured in a Mixed Forest Area (설마천 유역 CO2 Flux 실측 자료에 의한 총일차생산성 (GPP)과 MODIS GPP간의 비교 평가)

  • Jung, Chung-Gill;Shin, Hyung-Jin;Park, Min-Ji;Joh, Hyung-Kyung;Kim, Seong-Joon
    • Journal of The Korean Society of Agricultural Engineers
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    • v.53 no.2
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    • pp.1-8
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    • 2011
  • In this study, In order to evaluate reliable of MODIS GPP, the MODIS GPP and Flux tower measured GPP were compared to evaluate the use of method on 8 days composite MODIS GPP. The 2008 Flux data ($CO_2$ Flux and air temperature) measured in Seolmacheon watershed ($8.48\;km^2$) were used. The Flux tower GPP was estimated as the sum of $CO_2$ Flux and $R_{ec}$ (ecosystem respiration) by Lloyd and Taylor method (1994). The summer Monsoon period from June to August mostly contributed the underestimation of MODIS GPP by cloud contamination on MODIS pixels. The 2008 MODIS GPP and Flux tower GPP of the watershed were $1133.2\;g/m^2/year$ and $1464.3\;g/m^2/year$ respectively and the determination coefficient ($R^2$) after correction of cloud-originated errors was 0.74 (0.63 before correction). Even though effect of Cloud-Originated Errors was eliminated, Solar radiation and Temperature are affected at GPP. Measurement of correct GPP is difficult. But, If errors of MODIS GPP analyze on Cloud Moonsoon Climate in korea and eliminated effect of Cloud-Originated Errors, MODIS GPP will be considered GPP increasing of 9 %. There, Our results indicate that MODIS GPP show reliable and useful data except for summer period in Moonsoon Climate.

Variations of Turbulent Fluxes in the Atmospheric Surface Layer According to the Presence of Cloud (구름 유무에 따른 대기표층 난류속의 변화)

  • de Oliveira Junior, Jose Francisco;Kwon, Byung-Hyuk
    • Journal of the Korean earth science society
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    • v.25 no.2
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    • pp.87-93
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    • 2004
  • To study the effect of cloud on the variabilities of turbulent fluxes over the flat terrain, we used the gradient method to analyze the dynamic and thermodynamic data from the meteorological 9-m mast (0.75, 3 and 9 m) in Villafria airport in Spain. The decrease of the surface wind speed is governed by cooling at the surface following the evening transition. The sensible heat flux and the momentum flux are increased with the dynamic factor rather than the thermodynamic factor, and the sensible heat flux was not affected by the thermal condition. The global radiation did not play an important role in the variation of the sensible heat flux in the cloudy day, but the atmospheric surface layer was characterized rather by the wind intensity.

Finite Element Analysis of the Neutron Transport Equation in Spherical Geometry (구형에서 중성자 수송방정식의 유한요소법에 의한 해석)

  • Kim, Yong-Ill;Kim, Jong-Kyung;Suk, Soo-Dong
    • Nuclear Engineering and Technology
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    • v.24 no.3
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    • pp.319-328
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    • 1992
  • The Galerkin formulation of the finite element method is applied to the integral law of the first-order form of the one-group neutron transport equation in one-dimensional spherical geometry. Piecewise linear or quadratic Lagrange polynomials are utilized in the integral law for the angular flux to establish a set of linear algebraic equations. Numerical analyses are performed for the scalar flux distribution in a heterogeneous sphere as well as for the criticality problem in a uniform sphere. For the criticality problems in the uniform sphere, the results of the finite element method, with the use of continuous finite elements in space and angle, are compared with the exact solutions. In the heterogeneous problem, the scalar flux distribution obtained by using discontinuous angular and spatical finite elements is in good agreement with that from the ANISN code calculation.

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Study on the magnetic flux distribution of transformer by the use of finite element method (유한요소법에 의한 변압기의 자속분포 해석에 관한 연구)

  • 임달호;현동석;이철직
    • 전기의세계
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    • v.29 no.4
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    • pp.247-255
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    • 1980
  • In this study, an application of Finite Element Method which, in principle, based on variational calculus has been presented for the two-dimensional analysis of magnetic flux distribution in the shell type core of single phase transformer. The necessary stationarity condition of energy functional and boundary conditions were determined under the assumptions that the electromagnetic field considered is stationary and that the effect of eddy current is negligible. In the process of application the domain of magnetic field was divided into triangle subsectional elements and then the matrix equations were constructed for the respective triangular element and for those of all after the manipulation of minimization process to the vector potential of magnetic field at the each vertex of the element. Furthermore the numerical computation for the equations was guided by the Gaussian Elimination Methods. As the results obtained, it is found that the aspect of magnetic flux distribution inside the core as well as the leakage flux profile at the vicinity of the inner leg of the core is not much different from the well-known distribution profile of magnetic flux, however, the procedure shows to possess the merit of the uniquely deterministic nature for the flux distribution at the desired points.

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Comparison of daily solar flare peak flux forecast models based on regressive and neural network methods

  • Shin, Seulki;Lee, Jin-Yi;Moon, Yong-Jae
    • The Bulletin of The Korean Astronomical Society
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    • v.39 no.1
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    • pp.75.2-75.2
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    • 2014
  • We have developed a set of daily solar flare peak flux forecast models using the multiple linear regression (MLR), the auto regression (AR), and artificial neural network (ANN) methods. We consider input parameters as solar activity data from January 1996 to December 2013 such as sunspot area, X-ray flare peak flux, weighted total flux $T_F=1{\times}F_C+10{\times}F_M+100{\times}F_X$ of previous day, mean flare rates of a given McIntosh sunspot group (Zpc), and a Mount Wilson magnetic classification. We compute the hitting rate that is defined as the fraction of the events whose absolute differences between the observed and predicted flare fluxes in a logarithm scale are ${\leq}$ 0.5. The best three parameters related to the observed flare peak flux are as follows: weighted total flare flux of previous day (r=0.5), Mount Wilson magnetic classification (r=0.33), and McIntosh sunspot group (r=0.3). The hitting rates of flares stronger than the M5 class, which is regarded to be significant for space weather forecast, are as follows: 30% for the auto regression method and 69% for the neural network method.

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Preparation of high-performance nanofiltration membrane with antioxidant properties

  • Yu, Feiyue;Zhang, Qinglei;Pei, Zhiqiang;Li, Xi;Yang, Xuexuan;Lu, Yanbin
    • Membrane and Water Treatment
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    • v.13 no.4
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    • pp.191-199
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    • 2022
  • In industrial production, the development of traditional polyamide nanofiltration (NF) membrane was limited due to its poor oxidation resistance, complex preparation process and high cost. In this study, a composite NF membrane with high flux, high separation performance, high oxidation resistance and simple process preparation was prepared by the method of dilute solution dip coating. And the sulfonated polysulfone was used for dip coating. The results indicated that the concentration of glycerin, the pore size of the based membrane, the composition of the coating solution, and the post-treatment process had important effects on the structure and performance of the composite NF membrane. The composite NF membrane prepared without glycerol protecting based membrane had a low flux, when the concentration of glycerin increased from 5% to 15%, the pure water flux of the composite NF membrane increased from 46.4 LMH to 108.2 LMH, and the salt rejection rate did not change much. By optimizing the coating system, the rejection rate of Na2SO4 and PEG1000 was higher than 90%, the pure water flux was higher than 40 LMH (60psi), and it can withstand 20,000 ppm.h NaClO solution cleaning. When the post treatment processes was adjusted, the salt rejection rate of NaCl solution (250 ppm) reached 45.5%, and the flux reached 62.2 LMH.

Heat-Flux Analysis of Solar Furnace Using the Monte Carlo Ray-Tracing Method (몬테카를로 광선추적법을 이용한 태양로의 열유속 해석)

  • Lee, Hyun-Jin;Kim, Jong-Kyu;Lee, Sang-Nam;Kang, Yong-Heack
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.35 no.10
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    • pp.989-996
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    • 2011
  • An understanding of the concentrated solar flux is critical for the analysis and design of solar-energy-utilization systems. The current work focuses on the development of an algorithm that uses the Monte Carlo ray-tracing method with excellent flexibility and expandability; this method considers both solar limb darkening and the surface slope error of reflectors, thereby analyzing the solar flux. A comparison of the modeling results with measurements at the solar furnace in Korea Institute of Energy Research (KIER) show good agreement within a measurement uncertainty of 10%. The model evaluates the concentration performance of the KIER solar furnace with a tracking accuracy of 2 mrad and a maximum attainable concentration ratio of 4400 sun. Flux variations according to measurement position and flux distributions depending on acceptance angles provide detailed information for the design of chemical reactors or secondary concentrators.