• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.810-812
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• 2003

The dynamic characteristics of a three phase induction motor which is applied by various unbalanced voltages are simulated and analyzed in this paper. The voltage equations and torque equation in the dq stationary reference frame for the three phase star connected induction motor are used in this analysis. MATLAB and SIMULINK are employed as a simulation tool. The dynamic characteristics of speed and torque are simulated for various unbalanced voltages, that is, (1) cases with the same unbalance voltage factor but different unbalanced voltages, (2) cases with only one unbalanced voltages but different degree of unbalance, and (3) cases with the same positive sequence voltage but different negative sequence voltages. The simulated results are compared and analyzed with each other, and also with the results of balanced voltage.

• 조명전기설비학회논문지
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• 제13권1호
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• pp.86-93
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• 1999

대규모 배전계통 설비의 합리적인 운용과 안전성을 제고하기 위해서는 시스템의 불평형 상태를 정확하게 파악하는 것이 필수적이다. 본 논문에서는 전송선로와 부하의 불평을 고려한 3상 조류계산에 의하여 시스템의 불평형상태를 평가하였다. 이를 위하여, 먼저 전송선로에서는 선로정수에 상호결합과 상배치 및 연가의 영향을 고려하여 모델링하였고, 변압기는 1, 2차의 결선방식에 대하여 상호결합관계를 고려하였고 변압기 철손도 전압의 함수로 표현하여 계산하였다. 발전기모델에서는 돌극효과를 고려할 수 있도록 하였으며, 전력조류계산 알고리즘에서는 전력방정식을 상전압으로 표현하여 뉴톤-랩슨법으로 프로그램화 하였다.

• Journal of Power Electronics
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• 제18권4호
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• pp.1245-1254
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• 2018

The stability of a grid-connected system (GCS) has become a critical issue with the increasing utilization of renewable energy sources. Under grid faults, however, a grid-connected inverter cannot work efficiently by using only the traditional droop control. In addition, the unbalance factor of voltage/current at the common coupling point (PCC) may increase significantly. To ensure the stable operation of a GCS under grid faults, the capability to compensate for grid imbalance should be integrated. To solve the aforementioned problem, an improved voltage-type grid-connected control strategy is proposed in this study. A negative sequence conductance compensation loop based on a positive sequence power droop control is added to maintain PCC voltage balance and reduce grid current imbalance, thereby meeting PCC power quality requirements. Moreover, a stable analysis is presented based on the small signal model. Simulation and experimental results verify the aforementioned expectations, and consequently, the effectiveness of the proposed control scheme.

• 조명전기설비학회논문지
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• 제21권6호
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• pp.102-108
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• 2007

원유가의 급등과 더불어 에너지자원에 대한 관심이 크게 증가 되었는데, 다양한 에너지관련 분야 중에서 먼저 선행되어야 하는 것은 기존의 설비에서 사용하고 있는 에너지가 효과적으로 사용되고 있는가를 판단하는 것이며, 이를 에너지 효율의 산정이라고 한다. 따라서 본 논문에서는 에너지의 주요 수요처중 하나인 제지 생산 플랜트의 한 공정에서 전력에너지와 열에너지에 대한 에너지효율을 계산하였다. 이때 전력에너지는 운전 중인 전동기의 부하에 따른 효율을 중심으로, 열에너지는 공정에서 입출력되는 열량을 중심으로 계산하였다. 즉 운전 중인 생산설비의 한 공정의 전력과 열에너지에 대해 각각 에너지효율을 산정하였으며 일부 에너지절감에 대한 방안도 제시하였다.

• 전기학회논문지P
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• 제57권2호
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• pp.121-126
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• 2008

This paper analyzes the losses of a Steinmetz connection three-phase induction motor which is supplied by a single-phase source. The T-type equivalent circuit which is taken no-load losses into account is used to determine phase converter capacitive reactances at starting and rated speed by using the condition of the minimum voltage unbalance. The starting and the operating capacitor are replaced at the slip of the same voltage unbalance factor points which are depicted using two capacitive reactances. The operation characteristics are investigated by comparing with those of three-phase balanced operation to find the feasibility of single-phase operation. To analyze the losses of this motor, the output power decrease factor(OPDF), the loss ratio(LR), the no load loss ratio(NLLR), the copper loss ratio(CLR), the stator copper loss ratio(SCLR), and the rotor copper loss ratio(RCLR) are defined and simulated in the whole slip range. The simulated results show that OPDF is maintained almost uniformly, LR is low at low speed and high at high speed, CLR is higher !ban NLLR, but CLR varies concavely and NLLR varies convexly at high speed, SCLR is low at low speed and high at high speed, but SCLR varies convexly at high speed, and RCLR is nearly opposite to SCLR.

• 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.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 학술대회 논문집 전문대학교육위원
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• pp.106-108
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• 2005

3상 4선식 배전방식은 우리나라 저압 수용가에 널리 채용되고 있다. 단상과 3상을 혼합하여 사용하는 경우가 많아 전압불평형에 의한 여러 가지 문제를 발생하고 있다. 3상 4선식 배전시스템에서 3상 동력용으로 단독사용일 경우에는 별로 문제가 되지 않지만, 단상부하와 3상 부하를 혼용사용할 경우에는 부하의 불평형에 의한 어떤 문제를 발생하는지에 대해 저항성 및 유도성 부하를 대상으로 전압불평형율을 측정하고 분석하였다.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2005년도 춘계학술대회논문집
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• pp.106-110
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• 2005

In this paper, LED traffic signal lamp's operating circuit using Flyback converter and PFC IC has been presented. Most power conversion circuits use PFC IC for Power Factor Correction. The design parameter's value of Flyback converter has been proposed and the error amplifier which regulates the output voltage has been designed Besides, the under voltage protection circuit and the over voltage protection circuit for protecting the operating circuit kin unbalance of common electric power source and the temperature compensation circuit for fixed optical output power have been proposed.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 춘계학술대회 논문집
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• pp.852-857
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• 2007

For electric traction using a large power converter, harmonic problem in the p-ower quality and regenerating energy in side of efficiency are important. Recently, by advance in power electronics technology, some countries are considering regenerative inverter from the points of view. when the electric tractions are stopped or driven through the falling slope way, it is very useful to supply surplus energy to the power source by regenerating system in the efficient side of energy and it is very economical. these regenerating energy are supported electrical equipment through DC line. In this research, the purposes are suppressing extra DC-line voltage and saving energy generated while electric traction is been driving on the falling slope way or reducing speed for railway using a 1500V DC-voltage. Besides, the accompanied defects of current distortion, low power factor and the voltage unbalance will be solved by developing the algorism of inverter having ability to compensate current harmonic.

• 전기학회논문지P
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• 제53권3호
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• pp.110-115
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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. This paper presents a scheme on operation 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.