• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 전력전자학술대회
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• pp.114-116
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• 2018

This paper presents a control strategy to achieve the balanced sinusoidal output currents, as well as sinusoidal input currents for the matrix converter (MC) under unbalanced input voltages. By regulating the modulation index of the converter according to the instantaneous input voltages, the output currents are kept balanced and sinusoidal. In order to obtain sinusoidal input currents, the input power factor angle should be dynamically calculated based on the positive and negative sequence components of the input voltages. This paper proposes a simple method to construct the expected input power factor angle without the complicated sequence component extraction of input voltages. Simulation results are given to validate the effectiveness of the proposed control strategy.

• 한국산학기술학회논문지
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• 제15권4호
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• pp.1992-1998
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• 2014

본 연구는 지난 십 여년간 우리 사회에서 중요한 주제로 대두되었던 지역균형발전과 관련하여 그 의미 및 필요성과 방법에 대하여 논의하였다. 이전의 연구와 달리 본 연구는 현재의 경제구조의 특징이 지역균형발전에 대하여 의미하는 바를 분석하였다. 최근의 경제구조는 과거의 산업사회와 달리 정보사회, 지식기반경제, 디지털 경제 등으로 정의되고 있으며, 지식 및 아이디어, 인적자본 등의 역할이 중요하다는 특징을 갖고 있다. 본 고는 그러한 새로운 경제구조에서 지역균형발전의 개념은 이전의 산업사회와 어떠한 차이가 있는지를 분석하였다. 분석결과, 지역균형발전 조건에 필요한 물적 자본의 효율적 배분을 유지하기 위해서는 동시에 지역별 인적자본의 효율적 배분이 필요함을 지적하였다. 또한 지역의 불균형 발전이 발생시키는 사회적 비용을 추정하기 위하여, 지역들이 균형적으로 발전하는 경우에 비하여 불균형적으로 발전하는 경우에 경제성장률이 감소하게 되는 점을 의태모형실험을 통하여 보였다.

• Journal of Power Electronics
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• 제19권1호
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• pp.99-107
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• 2019

This study proposes a new modulation strategy to deal with unbalanced output voltage that is based on three-level neutral-point-clamped cascaded rectifiers. The fundament idea is to reallocate the value of the voltage levels generated by each of the modules on the basis of space vector pulse width modulation. This proposed modulation strategy can reduce the switching frequency while maintaining the mutual-module voltage balance. First, an analysis of unbalanced output voltage is reflected. Then a new modulation strategy is introduced in detail. Internal module capacitor voltages are balanced by the selection of redundant vectors. Moreover, the voltage balance ability is calculated. Finally, the feasibility of this modulation strategy is verified through experimental results.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권6호
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• pp.372-379
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• 2004

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. Rotating machines operating on an 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 steady states of a three-phase induction motor under unbalanced voltages. The three-phase voltages applied to the stator winding of the studied induction motor are controlled by respectively adjusting the magnitude and phase angle of each phase. The voltage unbalanced factor(VUF) of the three-phase source voltages can then be varied to examine the different values of VUF on machine's operation characteristics.

• 한국항행학회논문지
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• 제12권5호
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• pp.464-469
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• 2008

Serial 통신에는 RS-232C 통신과 같은 Un-balanced 방식과 RS-485/422통신과 같은 Balanced 통신 방식이 있다. 이 가운데 RS-485 통신의 경우는 통신의 거리가 길고 Balanced 방식에 의한 전송방식이기 때문에 RS-232에 비하여 데이터의 신뢰성이 매우 우수하므로 산업현장에 많이 사용되고 있다. 통상적으로는 하나의 통신선 위에서는 하나의 프로토콜을 이용하여 통신을 구현하는 것이 일반적인 방법이다. 본 연구에서는 RS-485 serial 전송의 Physical layer 위에 여러 가지 종류의 장비나 기기를 동시 연결하여 사용할 수 있도록, 다수의 통신 Protocol을 구현하는 방법을 실현하여 보고 성능을 검증하여 보고자 한다.

• 한국농공학회지
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• 제17권4호
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• pp.3962-3969
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• 1975

1. When the frame of the experimental apparatus was directly fixed on the platform, result from the spectrum density analysis showed that the generated vibration frequecy of the system was nearly-same as the system's own characteristic vibration frequency, 80Hz, in the case of the forcing vibration frequency was 7.5 to 22.5Hz. The reduction ratio of acceleration by balanced type model compare to non-balanced type one was 26.66 percent. 2. When the frame of experimental apparatus was fixed on the platform with putting a shock absorbing rubber between the frame and the platform, the generated vibration frequency of the system was same as forcing vibration frequency. When either frequency or the amplitude of the forcing vibration was increased, the acceleration ratio was increased too. The average reduction ratio was resulted 44.77 per cent. It was concluded that this method of acceleration measurement(the method using a shock absorbing rubber) was a reaonable method, because actual machine will work under such condition. As the vibration frequency and aptitude were increased, the absolute magnitude of acceleration was increased. 3. unbalanced rotating parts, and unbalanced moment of inertia of links were supposed to be causing factors of residual vibration in spite of using the balanced type oscillating mole drainer. This fact suggested that the attachment of the counter weight on the rotating parts which satisfy the condition mw$.$rw=m0e, was necessary. And also, it was expected that the shock absorbing effect could be improved by putting the shock absorbing materials between the moving parts and their supports.

• 응용통계연구
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• 제28권3호
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• pp.495-509
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• 2015

일반적인 2집단 분류(2-class classification)의 경우, 두 집단의 비율이 크게 차이나지 않는 경우가 많다. 본 논문에서는 두 집단의 비율이 크게 차이나는 불균형 데이터(unbalanced data)의 분류 문제에 대해서 다루고자 한다. 불균형 데이터의 분류방법은 균형이 맞는 데이터(balanced data)의 경우보다 분류하기 어려운 경우가 많다. 이런 자료에서 보통의 분류모형을 적용하게 되면 많은 경우에 대부분의 관측치가 큰 집단으로 분류 되는 경우가 많은데 실질적인 어플리케이션에서는 이런 오분류가 손해가 더 큰 경우가 대부분이다. 우리는 sampling 기법을 이용하여 다양한 분류 방법론의 성능을 비교 분석 하였다. 또한 비대칭 손실(asymmetric loss)을 가정한 경우에 어떤 방법론이 가장 작은 loss를 생성하는 지를 비교하였다. 성능 비교를 위해서는 오분류율(misclassification rate), G-mean, ROC, 그리고 AUC(Area under the curve) 등을 이용하였다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제21권3호
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• pp.64-81
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• 2016

To analyze the influence of various groundwater flow rates (specific discharge) on BHE system with balanced and unbalanced energy loads under assuming same initial temperature (15℃) of ground and groundwater, numerical modeling using FEFLOW was used for this study. When groundwater flow is increased from 1 × 10⁻⁷ to 4 × 10⁻⁷m/s under balanced energy load, the performance of BHE system is improved about 26.7% in summer and 22.7% at winter time in a single BHE case as well as about 12.0~18.6% in summer and 7.6~8.7% in winter time depending on the number of boreholes in the grid, their array type, and bore hole separation in multiple BHE system case. In other words, the performance of BHE system is improved due to lower avT in summer and higher avT in winter time when groundwater flow becomes larger. On the contrary it is decreased owing to higher avT in summer and lower avT in winter time when the numbers of BHEs in an array are increased, Geothermal plume created at down-gradient area by groundwater flow is relatively small in balanced load condition while quite large in unbalanced load condition. Groundwater flow enhances in general the thermal efficiency by transferring heat away from the BHEs. Therefore it is highly required to obtain and to use adequate informations on hydrogeologic characterristics (K, S, hydraulic gradient, seasonal variation of groundwater temperature and water level) along with integrating groundwater flow and also hydrogeothermal properties (thermal conductivity, seasonal variation of ground temperatures etc.) of the relevant area for achieving the optimal design of BHE system.

• 조명전기설비학회논문지
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• 제24권12호
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• pp.71-77
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• 2010

A discontinuity of magnetic circuits according to the end effect is generated in PMLSM. And magnetic state of the 3 phase coils becomes unbalanced. Due to the unbalanced magnetic state, the unbalanced flux linkage, back electro-magnetic force and inductance of the 3 phase coils appear. In result, the circulating current is generated by unbalanced inductance even if the input voltages are in balanced state. Then the thrust and efficiency are decreased because of the circulating current. Therefore, in this paper, the unbalanced inductance and the thrust reduction according to discontinuity of magnetic circuits are analyzed by FEA(2D). To demonstrate the validity of the analysis results, the experiment results are compared with analysis results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.996-997
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• 2015

This paper proposes parameter design principle of the sub-module capacitance, Arm inductance and a control method to reduced the circulating currents in modular multilevel converter(MMC) under unbalanced voltage conditions. Under balanced voltage conditions, only negative-sequence circulating currents exist. Consequently, the conventional method has considered only negative-sequence circulating currents in MMC. However, under unbalanced voltage conditions, there are positive-sequence, zero-sequence and negative-sequence circulating currents in MMC. Thus, under unbalanced voltage conditions, a control method should consider these all components. This study proposes the control method to reduced the circulating currents under the unbalanced voltage.