• Journal of Electrical Engineering and Technology
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• 제12권1호
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• pp.486-493
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• 2017

Refineries and chemical plants with isolated power systems that have a limited power supply are more susceptible to voltage changes from disturbances compared to power systems connected with a power company. Furthermore, most loads in such cases are induction motor loads, and therefore, transient voltage characteristics when starting a high-capacity motor must be examined. In general, high-capacity motors are customized appropriately to the load performance curve by the manufacturer during the construction of an industrial plant. Subsequently, when complying with the voltage drop permitted by international standards during the design process, power supply equipment such as transformers and generators is overdesigned. Therefore, a novel analysis is necessary on standards for startup and constraint voltage drops, as well as on identifying the voltage drop limitations for starting high-capacity motors in refineries and chemical plants with isolated power systems. In this study, field tests on an industrial plant were conducted, and simulations modeled under conditions identical to those of the field test system were performed using the general-purpose program ETAP in order to compare the results.

• 조명전기설비학회논문지
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• 제24권10호
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• pp.143-148
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• 2010

Recently, the KEPCO is constructing the PQMS(Power Quality Monitoring System) each of the distribution line and will establish the voltage sag standard based on the long time measurement data of PQMS. The voltage sag prospect is difficult for the power system manager, however, the voltage sag forecasted is very important because the damage effect of the voltage sag is very broad. This paper describes the prospect formula of the voltage sag magnitude in the PCC(Point Common Coupling) by the starting current when the high capacity equipment is connected with the distribution line. To achieve this, this paper has proposed the sag prospect formula revision of KEPCO for the reliability improvement and the proposed formula has been applied the voltage sag real case to inspect the calculation procedure and reliability.

• 한국초전도ㆍ저온공학회논문지
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• 제4권1호
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• pp.61-65
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• 2002

It becomes difficult and high in cost to construct new ducts and/or tunnels for power cables in metropolitan areas. This paper presents possible applications of an HTS superconducting power cables for transmitting electric power in metropolitan areas. Reflected were its important distinction such as compactness for installation in underground ducts and considerably high efficiency compared with present underground cables. In this paper, system modeling, transmission capacity and voltage class of compact HTS cables which should be applied to existing ducts were reviewed. Based on this, the following items on urban transmission system are examined. (1) A method of constructing a model system to introduce high temperature superconducting cables to metropolitan areas is presented. (2)The maximum outer diameter of HTS cables to be accommodated in exiting ducts is calculated based on the design standards for current cable ducts. (3)The voltage level that can be accommodated by existing ducts is examined.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 A
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• pp.79-81
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• 1993

We have proposed a new technology compensating reactance component of line and load. Because capacity of SC is static, it is not appropriate to varing reactance and causes SSR problems. TCSC is introduced for the flecxible control of reactance of SC. If SC voltage is varied when the capacitor current is constant, it can be considered that capacity of SC was varied. SO capacity of SC can be controlled by controlling the voltage of SC. Control reference voltage of SC can be obtained from the condition that sum of reactive powers in all parts is zero.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.64-68
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• 1991

This paper presents development of the submersible pump-motor with a high voltage and large capacity. Today many manufacturers are fabricated submersible pump-motor in this country. But only there are small or midium capacity pump-motor of low voltage. Also the condition of large flow rated it will not be caplable of carrying out the task of which various for reason geographically and seasonably. In order to be equal to the task it will be increase its capacity. Recently we were development that the large capacity with high voltage submersible pump-motor.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권8호
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• pp.509-513
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• 2000

This paper deals with the parallel operation of space vector PWM for large capacity inverter system. To enlarge the capacity of inverter system and to reduce the current ripples on inverter output side, two or more inverters are operated in parallel. In this paper, a new parallel operation strategy which minimizes the harmonic distortion of the output stage is described. The proposed method is developed on the basis of the space-vector PWM in order to increase the linearly controllable voltage range. With the help of the proposed voltage synthesis method, the total harmonic distortion of the output stage can be greatly reduced in compared with that of conventional method with sinusoidal PWM or that of the single inverter operation case. The experimental results with reduced scale test show the feasibility of the proposed voltage synthesis method.

• 전력전자학회논문지
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• 제18권3호
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• pp.270-278
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• 2013

This paper proposes a control method for high voltage direct current(HVDC) with modular multilevel converter (MMC) under unbalanced voltage conditions considering the submodule(SM)'s current capacity and circulating current. It is aimed to propose a control method in which the current peak value does not exceed the maximum value of HVDC-MMC by considering the current capacity of the SM under unbalance voltage conditions. And it analyzes the effect of the unbalanced voltage on circulating currents in MMC and then proposes a control method considering each component of circulating currents under unbalanced voltages. The effectiveness of the proposed controlling method is verified through simulation results using PSCAD/EMTDC.

• 전기학회논문지
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• 제67권7호
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• pp.809-815
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• 2018

Distributed generations (DGs) using renewable energy resources in power systems have been widely integrated, and many of these DGs have intermittency. DGs can significantly affect the overall voltage profile of the system through the reactive power control for a voltage support. Therefore, in the planning stage of the optimal operation and dispatch of voltage regulation devices, DGs' hosting capacity with the reactive power control scheme should be considered. In this paper, we model the IEEE 34-bus test feeder, including all essential equipment. An optimization method is utilized to determine the optimal siting and operation of the voltage regulation devices in the presence of DGs with reactive power control scheme. Finally, we compare the optimal results of the each case to analyze the relationship among the hosting capacity of the DGs and voltage regulation devices operation.

• Journal of Power Electronics
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• 제7권1호
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• pp.72-80
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• 2007

Voltage sags are one of the most frequently occurring power quality problems challenging power systems today. The Unified Power Quality Conditioner (UPQC) is one of the major custom power solutions that are capable of mitigating the effect of supply voltage sags at the load or Point of Common Coupling (PCC). A UPQC-Q employs a control method in which the series compensator injects a voltage that leads the supply current by $90^{\circ}C$ so that the series compensator at steady state consumes no active power. However, the UPQC-Q has the disadvantage that its series compensator needs to be overrated. Thus it cannot offer effective compensation. This paper proposes a new control scheme for the UPQC-Q that offers minimum power injection. The proposed minimum power injection method takes into consideration the limits on the rated voltage capacity of the series compensator and its control scheme. The validity of the proposed control scheme is investigated through simulation and experimental results.

• 조명전기설비학회논문지
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• 제28권11호
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• pp.9-16
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• 2014

The electronic ballast for HID lamps needs high ignition voltage which is consisted of high voltage pulse ignitor. However, In the case of street lamp it is far from a lamp to a ballast, the conventional pulsed high voltage ignitor can not turn on the HID lamps because of reduction of ignition voltage. Therefore, it needs to do the research on a resonant ignition to turn on the HID lamps. However, the resonant circuit which is consisted of LC occurs over current, so the capacity of the ignitor increases. The capacity of the ignitor can be reduced by using the transformer. In this case, the capacitor for resonance is installed to the secondary of the transformer, and the capacitor needs high withstanding voltage. Therefore, it needs to do the research on a resonant ignition to reduce the voltage over the resonant capacitor by dividing the secondary of the transformer.