• 전력전자학회논문지
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• 제15권1호
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• pp.60-68
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• 2010

최근 PCS(Power Conditioning System)는 고효율, 고 전력밀도 및 고 기능화를 통해 고집적화 추세에 있다. 이러한 요구를 만족시키기 위해 LLC 공진인버터와 LF 사이클로 컨버터로 구성된 회로를 제안했다. 동작분석 및 1kW 시제품을 제작하여 110Vac, 60Hz 전원계통연계실험 통해 적용 가능함을 보였으며 이에 대한 실험결과를 서술하였다.

• Journal of Electrical Engineering and Technology
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• 제9권2호
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• pp.721-725
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• 2014

In this paper, we propose a fast adaptive power allocation method for an orthogonal frequency division multiple access (OFDMA) system that employs an adaptive modulation and coding (AMC) scheme. The proposed scheme aims to reduce the calculation complexity of greedy adaptive power allocation (APA), which is known as the optimal algorithm for maximizing the utility argument of power. Unlike greedy APA, which starts power allocation from "0", the proposed algorithm initially allocates a certain level of power determined by the water-filling scheme. We theoretically demonstrate that the proposed algorithm has almost the same capability of maximizing the utility argument as the greedy APA while reducing the number of operations by 2M, where M is the number of AMC levels.

• Journal of Electrical Engineering and Technology
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• 제8권4호
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• pp.737-743
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• 2013

The small-scaled onsite generators such as photovoltaic power, wind power, biomass and fuel cell belong to decarbonization techniques. In general, these generators tend to be connected to utility systems, and they are called distributed generations (DGs) compared with conventional centralized power plants. However, DGs may impact on stabilization of utility systems, which gets utility into trouble. In order to reduce utility's burdens (e.g., investment for facilities reinforcement) and accelerate DG introduction, the advanced operation algorithms under the existing utility systems are urgently needed. This paper presents the advanced voltage regulation method in power systems since the sending voltage of voltage regulators has been played a decisive role restricting maximum installable DG capacity (MaxC_DG). For the proposed voltage regulation method, the difference from existing voltage regulation method is explained and the detailed concept is introduced in this paper. MaxC_DG estimation through case studies based on Korean model network verifies the superiority of the proposed method.

• 전력전자학회논문지
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• 제13권2호
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• pp.145-151
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• 2008

본 논문에서는 계통 전압이 불평형인 경우에 정확한 위상각을 검출할 수 있는 정상분 전압 관측기를 이용한 PLL(Phase Locked Loop) 방법을 제안한다. 제안된 PLL 방법은 기존의 전역 통과 필터(APF, All Pass Filter)를 이용하여 불평형 전원전압으로부터 정상분 전압을 구하는 것과는 달리 전차원 상태관측기를 사용함으로써 불평형사고 발생 시 추정위상각의 과도상태 응답특성을 개선하였다. 기존의 정상분 전압 추출 PLL 방법과 본 논문에서 제안된 PLL 방법의 성능을 비교하기 위해, 전원단 전압에 불평형 사고 발생시 위상각을 검출하는 실험을 하였고, 이를 통해 기존의 전역 통과 필터를 이용한 정상분 전압 추출 PLL 방법보다 제안된 전차원 상태관측기를 이용한 정상분 전압 추출 PLL 방법의 과도상태 응답특성이 개선됨을 입증하였다.

• Journal of Power Electronics
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• 제9권2호
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• pp.320-333
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• 2009

A Photovoltaic (PV) system's power output varies with the change of climate. Frequency deviations, tie line voltage swings are caused by the varying PV power when large PV power from several PV systems is fed in the utility. In this paper, to overcome these problems, a simple coordinated control method for smoothing the variations of combined PV power from multiple PV systems is proposed. Here, output power command is formed in two steps: central and local. Fuzzy control is used to produce the central smoothing output power command considering insolation, variance of insolation and absolute average of frequency deviation. In local step, a simple coordination is kept between the central power command and the local power commands by producing a common tuning factor. Power converters are used to achieve the same output power as local command power employing PI control law for each of the PV generation systems. The proposed method is compared with the method where conventional Maximum Power Point Tracking (MPPT) control is used for each of the PV systems. Simulation results show that the proposed method is effective for smoothing the output power variations and feasible to reduce the frequency deviations of the power utility.

• 전기학회논문지
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• 제59권9호
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• pp.1523-1529
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• 2010

This paper describes the distribution power system econimical PQMS(Power quality monitoring system) of Utility. Recently, the korea power quality standard has been established based on the IEC Std. By IEC Std., the power quality assessment point is measured in PCC(Point of common coupling). In this case, the utility has to construct PQM system in all customer PCC point and the PQ meter cost would be very high in order to acquire the suitable data. Also the distribution system would be encounter the communication overload problem due to the huge data. Accordingly the utilities could not apply to PQM system in the distribution power system by the cost and communication problem. In this paper, the proposed economical PQMS has the voltage and current signal reiteration function and FFT operation function is transferred the server. Also the voltage and current measurement channels are minimized by a classified substation construction.

• 한국경영과학회지
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• 제28권4호
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• pp.1-19
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• 2003

This paper studies power and rate control for data users on the forward link of CDMA system with two cells. The QoS for data users is specified by delay and error rate constraints as well as a family of utility functions representing system throughput and fairness among data users. Optimal power and rate allocation problem is mathematically formulated as a nonlinear programming problem, which is to maximize total utility under delay and error rate constraints, and optimal power and rate allocation scheme (OPRAS) is proposed to obtain a good solution in a fast time. Computational experiments show that the proposed scheme OPRAS works very well and increases total utility compared to the separate power and rate allocation scheme (SPARS) which considers each cell individually.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1999년도 전력전자학술대회 논문집
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• pp.431-434
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• 1999

This paper presents design of controllers for battery energy storage system. The proposed battery energy storage system can be controlled to operate in the power conditioning mode or the inverter mode. The operation of this mode further divided into three cases: (a) in the peak load period, the load power supplied from the utility is minimized as far as possible; (b) in the off-peak load period, the utility supplies power to the load and charges the battery bank with automatic charging control; (c) in the medium load period, to save battery energy the real power flow out of the battery energy storage system is minimized. Besides, in all cases, the proposed battery energy storage system also automatically compensates the harmonics, subharmonics and reactive power factor in the utility side are much improved. Simulation results are presented by the effectiveness of the proposed controllers for battery energy storge system.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2007년도 추계학술대회 논문집
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• pp.279-285
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• 2007

Since the residential load is an AC load and the output of solar cell is a DC power, the photovoltaic system needs the DC/AC converter to utilize solar cell. In case of driving to interact with utility line, in order to operate at unity power factor, converter must provide the sinusoidal wave current and voltage with same phase of utility line. Since output of solar cell is greatly fluctuated by insolation, it is necessary that the operation of solar cell output in the range of the vicinity of maximum power point. In this paper, DC/AC converter is three phase PWM converter with smoothing reactor. And then, feedforward control used to obtain a superior characteristic for current control and digital PLL circuit used to detect the phase of utility line.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.288-291
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• 2007

Since the residential load is an AC load and the output of solar cell is a DC power, the photovoltaic system needs the DC/AC converter to utilize solar cell. In case of driving to interact with utility line, in order to operate at unity power factor, converter must provide the sinusoidal wave current and voltage with same phase of utility line. Since output of solar cell is greatly fluctuated by insolation, it is necessary that the operation of solar cell output in the range of the vicinity of maximum power point. In this paper, DC/AC converter is three phase PWM converter with smoothing reactor. And then, feedforward control used to obtain a superior characteristic for current control and digital PLL circuit used to detect the phase of utility line.