• 전기학회논문지
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• 제57권1호
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• pp.58-64
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• 2008

In this paper, we present an active anti-islanding method with a load monitoring system using reactive power control. The proposed method, which is based on reactive power control, has fewer harmonics components than those in conventional methods, and it can minimize the reactive power component of the grid because it compensates the reactive power component with the load monitoring. The proposed quick islanding detection method was confirmed from the experimental results with an inverter for a 3kW photovoltaic system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전력기술부문
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• pp.158-161
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• 2004

This paper presents practical applications of reactive power and voltage planning to obtain voltage stability and operational voltage level for 2005 year summer peak Korea power system. It also describes the new electric facilities, operation criteria, voltage levels, MVAr flows, reactive power reserves in each control area. And reactive compensation devices are installed to maintain established voltage levels and stability margins. This simulation results show the improvement of voltage levels and the increase of reactive margins & interface flow margins. Finally, the paper reports the necessity of dynamic reactive reserves. It can be applied to analysis reactive compensation requirements and P-V & V-Q curves by PSS/E & VSAT.

• Journal of Power Electronics
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• 제15권5호
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• pp.1348-1357
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• 2015

Under traditional unified power quality conditioner (UPQC) control, a UPQC series converter (SC) is mainly used to handle grid-side power quality problems while its parallel converter (PC) is mainly used to handle load-side power quality problems. The SC and PC are relatively independent. The SC is usually in standby mode and it only runs when the grid voltage abruptly changes. In this paper, novel UPQC coordinated control strategies are proposed which use the SC to share the reactive power compensation function of the PC especially without grid-side power quality problems. However, in some cases, there will be a circulating current between the SC and the PC, which will probably influence the compensation fashion, the compensation capacity, or the normal work of the UPQC. Through an active power circulation analysis, strategies with and without a circulating current are presented which fuses the reactive power allocation strategy of the SC and the PC, the composite control strategy of the SC and the compensation strategy of the DC storage unit. Both of the strategies effectively solve the SC long term idle problem, limit the influence of the circulating current, optimize all of the UPQC units and reduce the production cost. An analysis, along with simulation andexperimental results, is presented to verify the feasibility and effectiveness of the proposed control strategies.

• Journal of Electrical Engineering and Technology
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• 제7권5호
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• pp.689-697
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• 2012

This paper proposes a new coordinated voltage control scheme between STATCOM (Static Synchronous Compensator) and reactive power compensation devices, such as shunt elements(shunt capacitor and shunt reactor) and ULTC(Under-Load Tap Changer) transformer in a local substation. If STATCOM and reactive power compensators are cooperatively used with well designed control algorithm, the target of the voltage control can be achieved in a suddenly changed power system. Also, keeping reactive power reserve in a STATCOM during steady-state operation is always needed to provide reactive power requirements during emergencies. This paper describes the coordinative voltage control method to keep or control the voltage of power system in an allowable range of steady-state and securing method of momentary reactive power reserve using PSS/E with Python. In the proposed method of this paper, the voltage reference of STATCOM is adjusted to keep the voltage of the most sensitive bus to the change of loads and other reactive power compensators also are settled to supply the reactive power shortage in out range of STATCOM to cope with the change of loads. As the result of simulation, it is possible to keep the load bus voltage in limited range and secure the momentary reactive power reserve in spite of broad load range condition.

• 조명전기설비학회논문지
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• 제27권9호
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• pp.100-107
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• 2013

Since the West Sea experiences a big difference in tides, the output power of the small marine hydroelectric power plant varies with the tide. When an induction generator is used here for small hydroelectric power, the reactive power capacitor should be installed at the generator main bus to compensate for the changes in power. As such, the sizing method for the power compensation of the induction generator is reviewed and an optimal method for compensation is suggested. The self-excitation minimum capacitor capacity method, which prevents high voltages, and the power factor automatic control method, which retains a power factor of greater than 90% are reviewed. The compensation effect of reactive power is confirmed through a case study.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 A
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• pp.168-170
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• 2001

This paper presents the strategy of reactive power compensation which directly improves voltage stability. Voltage stability index that serves as an indirect assessment of voltage stability margin is derived from M.G.C.F. (Modified Generalized Curve Fit) algorithm incorporating load model. Weak buses are ranked by this stability index, and amounts of reactive power compensation are determined by function of reactive power and stability index. Using the proposed strategy, all load buses can be prevented from voltage collapse gradually. A simple illustrative example is given as well as simulation results obtained on 5 bus test system and 19 bus real power system.

• 한국인터넷방송통신학회논문지
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• 제14권6호
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• pp.119-123
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• 2014

본 연구에서는 익일부하예측 기능을 갖는 빌딩에너지관리시스템을 제시한다. 기존의 빌딩에너지 관리시스템은 빌딩내의 다양한 인프라를 이용하여 에너지를 감시 한다 그러나 이러한 시스템을 구현하기 위해서는 많은 인프라 구축비용이 소요 되어, 에너지 절감을 위한 인프라 구축비용과 실제 절감된 전기 요금을 비교 할 경우, 에너지 절감을 위해 투자한 비용을 전기 요금 절약으로 회수하는데 수년이 걸리고, 또한 인프라 설비 유지 보수를 고려할 경우, 결과적으로 에너지 절약 효과가 미비하다. 따라서 본 연구에서는 보다 저렴하고 합리적인 방법으로 빌딩의 에너지 소비를 억제할 수 있도록, 기상청데이터와 한전의 ISmart 데이터를 기반으로 데이터마이닝기법을 이용하여 빌딩의 익일 부하 사용량을 예측하고 이를 기반으로 빌딩 부하의 On/Off를 수행하도록 빌딩에너지관리시스템을 구현함으로써 상대적으로 저렴한 비용으로 빌딩에너지 사용의 합리화를 이루도록 하였다.

• Journal of Power Electronics
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• 제17권2호
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• pp.522-532
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• 2017

This paper presents a novel integrated structure for a cascaded distribution static compensator (D-STATCOM) and distribution transformer for medium-voltage reactive power compensation. The cascaded multilevel converter is connected to a system via a group of special designed taps on the primary windings of the Dyn11 connection distribution transformer. The three-phase winding taps are symmetrically arranged and the connection point voltage can be decreased to half of the line-to-line voltage at most. Thus, the voltage stress for the D-STATCOM is reduced and a compromise between the voltage rating and the current rating can be achieved. The spare capacity of the distribution transformer can also be fully used. The working mechanism is explained in detail and a modified control strategy is proposed for reactive power compensation. Finally, both simulation and scaled-down prototype experimental results are provided to verify the feasibility and effectiveness of the proposed connection structure and control strategy.

• Journal of Electrical Engineering and Technology
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• 제6권2호
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• pp.147-153
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• 2011

This paper proposes a methodology using a tool based on the branch-parameter continuation power flow (BCPF) in order to restore the power flow solvability in unsolvable contingencies. A specified contingency from a set of transmission line contingencies is modeled, considering the transient analysis and practice in the Korean power system. This tool traces a solution path that satisfies the power flow equations with respect to the variation of the branch parameter. At a critical point, in which the branch parameter can move on to a maximum value, a sensitivity analysis with a normal vector is performed to identify the most effective compensation. With the sensitivity information, the location of the reactive power compensation is determined and the effectiveness of the sensitivity information is verified to restore the solvability. In the simulation, the proposed framework is then applied to the Korean power system.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제48권12호
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• pp.715-726
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• 1999

This paper estimates the capacity of shunt type active power filters(APF) for harmonic/reactive power compensation with a thyristor converter load. The base capacity requirement of APF is defined for idealized converter load current waveform and the effect of commutation overlap on the APF capacity is examined. The APF capacity required for reactive power compensation in addition to the harmonic elimination is estimated to give maximum achievable power factor for various operating condition of the partially-loaded thyristor converter. The method of current limit of APF is introduced, and it is shown that the APF capacity can be considerably reduced by deliberately limiting the peak current while maintaining the filtering performance to meet the level std 519 regulation.