• 전기학회논문지
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• 제65권8호
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• pp.1334-1339
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• 2016

In a power grid that has a high wind power penetration, the fast voltage support of a wind power plant (WPP) during the grid fault is required to stabilize the grid voltage. This paper proposes a voltage control scheme of a doubly-fed induction generator (DFIG)-based WPP that can promptly support the voltage of the point of common coupling (PCC) of a WPP during the grid fault. In the proposed scheme, the WPP and DFIG controllers operate in a voltage control mode. The DFIG controller employs two control loops: a maximum voltage dip-dependent reactive current injection loop and a reactive power to voltage loop. The former injects the reactive power in proportion to the maximum voltage dip; the latter injects the reactive power in proportion to the available reactive power capability of a DFIG. The former improves the performance of the conventional voltage control scheme, which uses the latter only, by increasing the reactive power as a function of the maximum voltage dip. The performance of the proposed scheme was investigated for a 100-MW WPP consisting of 20 units of a 5-MW DFIG under various grid fault scenarios using an EMTP-RV simulator. The simulation results indicate that the proposed scheme promptly supports the PCC voltage during the fault under various fault conditions by increasing the reactive current with the maximum voltage dip.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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• pp.869-871
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• 2005

As deregulated electricity markets are being implemented in different countries, the remuneration of reactive power which contribute to ancillary services is one of the key issues, so it is necessary to evaluate the generator's reactive. In this paper, we focus on the evaluation of reactive power which contributes to reactive power balance. The idea is that the main usages of the reactive power of generator can be divided into two components. First one is physically required amounts for transmitting the real power and the second one is the amounts contributed to support the system, that is, to maintain the voltage profiles. In this paper, the second component is used to evaluate the effective amounts of the reactive power contributed to ancillary service.

• Journal of Power Electronics
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• 제16권4호
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• pp.1494-1503
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• 2016

Power quality promotion has received increasing attention because of the wide use of semiconductor devices in recent decades. Reactive power regulation is crucial to ensuring the stable operation of power systems. In this study, a continuous reactive power controller, which is referred to as a parallel-connected magnetic energy recovery switch (MERS), is developed to regulate voltage or power factor in power grids. First, the operating principle is introduced, and a mathematical model is built. Second, a new control method for restraining current harmonics and the peak voltages of capacitors is presented. Using the proposed method, the MERS shows a wide range in terms of reactive power compensation. Finally, the performance of the proposed controller is demonstrated through computer simulations and experiments. Unlike STATCOMs, the proposed controller entails low losses, adopts a small dc capacitor, and offers ease of use.

• 전력전자학회논문지
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• 제5권4호
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• pp.377-385
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• 2000

본 논문에서는 국내 최초로 설치된 Custom Power기기인 배전용 STATCOM(STATic COMpensator)의 기기 신뢰성 확보를 위힌 기가 테스트 및 설계통 운전 분석결과를 보이고 있다. Custom Power는 유연송전시스템(FACTS : Flexible AC Transmission System)과 같이 교류전력계통을 제어함으로써 효율적이고 유연한 전력계통의 운용과 구성을 목적으로 한다. STATCOM은 Custom Power기기의 한 형태로 무효전력 보상, 전압조정, 그리고 전압 퓰리커 억제 등의 기능을 가진다. 본 논문에서는 STATCOM 시운전 결과 무효전력과 역률 보상에서 우수한 성능을 보임을 확인할 수 있다.

• 전기학회논문지
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• 제61권12호
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• pp.1782-1790
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• 2012

In this paper, a methodology to use load duration curve and the reactive power factor sensitivity of generation cost is proposed for analyzing the effects of load power factor effectively. A great deal of cases of power systems are classified into several patterns according to the characteristics using load duration curve, and the overall effects of load power factor are assessed by integrating the analysis results of load power factor in all the patterns. The reactive power sensitivity of generation cost and the integrated costs such as generation cost, investment cost, voltage variation penalty cost and CO2 emission cost are used for determining an appropriate load power factor. A systematic procedure for effective analysis of load power factor is presented. It is shown through the application to the practical power system of KEPCO(Korea Electric Power Corporation)that the effects of load power factor can be analyzed effectively using load duration curve and reactive power factor sensitivity.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.115-116
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• 2008

This paper discusses local reactive power control method of substation which has FACTS controller(STATCOM) and other reactive power controllers. Not only The relation between entral control and local control method was discussed, but also local STATCOM control methd was done. With this results, revised coordinative control method which can implement system voltage sensitivity characteristics of each control devices. Also, this method can give proper solution for system status which requires momentary reactive reserve. This method is expected to be applied to control multiple substation reactive power devices which is combined with SCADA system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.455-456
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• 2007

Maintaining the voltages is important in the power systems and the voltage is closely associated with the reactive powers. Therefore, the voltages are maintained by controlling the reactive powers. However actually it is impossible to control reactive power for maintaining all bus voltages. Thus, Secondary Voltage Regulation was designed. It divides power systems into some control areas and controls pilot node with the included generators. The reactive powers of generators can control pilot bus voltage continuously and fast. Therefore we need to divide areas and select control generators for SVR with Electrical distance. Then estimation of the reactive power reserves of geneators is needed in voltage control areas to control voltages of the pilot nodes.

• 전기의세계
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• 제15권3호
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• pp.1-7
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• 1966

The past several years have strongly anticipated the advent of a more integrated system control combining active power and voltage-reactive power controls. This paper presents a new approach to the intergrated system control with primary emphasis on the development of a new control method which combines the conventional economical load dispatching(ELD) and voltage-reactive power controls. The control method, in its fundamental principle, first determines the optimal active power allocation in accordance with the conventional ELD controller. By a proper manipulation of the remaining reactive power sources in the system, the control method then reduces the transmission losses of the system by the adjustment of system voltage distribution and also by the proper allotment of reactive power flows.

• 전기학회논문지
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• 제65권1호
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• pp.23-30
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• 2016

Wake effects cause wind turbine generators (WTGs) within a wind power plant (WPP) to produce different levels of active power and subsequent reactive power capabilities. Further, the impedance between a WTG and the point of interconnection (POI)-which depends on the distance between them-impacts the WPP's reactive power injection capability at the POI. This paper proposes a voltage control scheme for a WPP based on the available reactive current of the doubly-fed induction generators (DFIGs) and its impacts on the POI to improve the reactive power injection capability of the WPP. In this paper, a design strategy for modifying the gain of DFIG controller is suggested and the comprehensive properties of these control gains are investigated. In the proposed scheme, the WPP controller, which operates in a voltage control mode, sends the command signal to the DFIGs based on the voltage difference at the POI. The DFIG controllers, which operate in a voltage control mode, employ a proportional controller with a limiter. The gain of the proportional controller is adjusted depending on the available reactive current of the DFIG and the series impedance between the DFIG and the POI. The performance of the proposed scheme is validated for various disturbances such as a reactive load connection and grid fault using an EMTP-RV simulator. Simulation results demonstrate that the proposed scheme promptly recovers the POI voltage by injecting more reactive power after a disturbance than the conventional scheme.

• 전기학회논문지
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• 제65권7호
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• pp.1311-1315
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• 2016

Induction motor requires a rotating magnetic field for rotation. Current required to generate the rotating magnetic field is immediately magnetizing current. This magnetizing current is associated with the reactive power. Induction motor is always required reactive power. If reactive power is supplied only to the power supply side, the power factor is low. Therefore, it is to compensate the power factor by connecting capacitors in parallel to the motor terminal. If the capacitor current is greater than the magnetizing current of the motor, there is a possibility that the self-excitation occurs. High voltage generated by the self-excitation leads to insulation failure on the motor. So it is necessary to calculate the power factor correction capacitor capacity the most suitable to the extent that the magnetizing current does not exceed the capacitor current. In this study, we first computed the magnetization current and the reactive power of the induction motor and then calculates a limit of the maximum power factor by comparing the magnetizing current and the capacitor current installed in order to achieve the target power factor.