• Journal of Power Electronics
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• 제12권5호
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• pp.821-829
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• 2012

This research article presents a novel approach based on an instantaneous active and reactive power component (p-q) theory for generating reference currents for shunt active filter (SHAF). Three-phase reference current waveforms generated by proposed scheme are tracked by the three-phase voltage source converter in a hysteresis band control scheme. The performance of the SHAF using the p-q control strategy has been evaluated under various source conditions. The performance of the proposed control strategy has been evaluated in terms of harmonic mitigation and DC link voltage regulation. In order to maintain DC link voltage constant and to generate the compensating reference currents, we have developed Fuzzy logic controller with different (Trapezoidal, Triangular and Gaussian) fuzzy M.F.s. The proposed SHAF with different fuzzy M.F.s is able to eliminate the uncertainty in the system and SHAF gains outstanding compensation abilities. The detailed simulation results using MATLAB/SIMULINK software are presented to support the feasibility of proposed control strategy. To validate the proposed approach, the system is also implemented on a real time digital simulator and adequate results are reported for its verifications.

• 대한안전경영과학회지
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• 제8권6호
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• pp.109-118
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• 2006

This paper proposes service layout strategy considering service characteristics by the use of benchmarking production system such as layout by P-Q chart, improvement tool, automated system, Toyota production system and lean production system. This paper represents operation methodology of statistical process control using control chart for service performance outcomes.

• 전기학회논문지
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• 제66권2호
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• pp.292-299
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• 2017

In this paper, multiple ESS(Energy Storage System) control strategy for microgrids is presented. Installation of ESS becomes mandatory when microgrids are used to supply high quality power to the loads. The one of main functions of the ESS is to maintain power balance. However ESS has limitation of its capacity and instantaneous injecting power. Power allocation method based on SOC(State Of Charge) of each ESS is proposed. P-Q control is employed as the basic control strategy for the distributed ESSs. By using the proposed method, the coefficients in the conventional P-Q control method are modified. The ESSs with higher SOC inject more active power, while those with lower SOC inject less, leading to more balanced SOC levels among the ESSs. The proposed method is demonstrated by simulation using PSCAD/EMTDC.

• 전기학회논문지P
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• 제54권2호
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• pp.61-66
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• 2005

This paper presents an unified method which solves real and reactive power dispatch problems for the economic operation of power systems using evolutionary computation such as genetic algorithms(GA), evolutionary programming(EP), and evolution strategy(ES). Many conventional methods to this problem have been proposed in the past, but most of these approaches have the common defect of being caught to a local minimum solution. The proposed methods, applied to the IEEE 30-bus system, were run for 10 other exogenous parameters and composed of P-optimization module and Q-optimization module. Each simulation result, by which evolutionary computations are compared and analyzed, shows the possibility of applications of evolutionary computation to large scale power systems.

• Journal of Power Electronics
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• 제19권1호
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• pp.234-243
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• 2019

Studying the control strategy of a microgrid under the load unbalanced state helps to improve the stability of the system. The magnitude of the power fluctuation, which occurs between the power supply and the load, is generated in a microgrid under the load unbalanced state is called negative sequence reactive power $Q^-$. Traditional power distribution methods such as P-f, Q-E droop control can only distribute power with positive sequence current information. However, they have no effect on $Q^-$ with negative sequence current information. In this paper, a stationary-frame control method for power sharing and voltage unbalance compensation in islanded microgrids is proposed. This method is based on the proper output impedance control of distributed generation unit (DG unit) interface converters. The control system of a DG unit mainly consists of an active-power-frequency and reactive-power-voltage droop controller, an output impedance controller, and voltage and current controllers. The proposed method allows for the sharing of imbalance current among the DG unit and it can compensate voltage unbalance at the same time. The design approach of the control system is discussed in detail. Simulation and experimental results are presented. These results demonstrate that the proposed method is effective in the compensation of voltage unbalance and the power distribution.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(2)
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• pp.729-733
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• 2003

This paper proposed a novel current control strategy on active power filters using p-q-r instantaneous power theory which can compensate the line current harmonics and the neutral line current in unbalanced and/or distorted source conditions in three-phase four-wire systems. The proposed current control method is based on a sinusoidal PWM for fully-digital implementation which was compared with a hysteresis PWM. Simulation results showed good performance of the proposed current control strategy on shunt type APFs.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.1072-1074
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• 2003

In this paper, a new control strategy of a series active power filter using direct compensating voltage extraction method is proposed. This control algorithm compensates harmonics, reactive power and neutral line currents which are generated by balanced or unbalanced nonlinear loads. The advantage of this method is that the compensating voltage of the series active power filter can be extracted without phase transformation. Therefore, calculation time is shorten and the control method is simple compared with conventional method as the p-q theory In addition, this control strategy was applied for the series active power filter in 3-phase 4-wire system which is widely employed in distributing electric energy to several office building and manufacturing plants. Some results obtained from the experimental model using the proposed method are presented to demonstrate and confirm its validity.

• 현장농수산연구지
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• 제19권1호
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• pp.139-151
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• 2017

본 연구에서는 기능성 우유의 생산을 위해 높은 항산화 효과를 가지고 심혈관계 질환 환자에게 유익한 CoQ10을 홀스타인 젖소의 우유에 전이시키기 위해 CoQ10 생산성이 높은 R. sphaeroides가 반추위 내에서 생존하며 반추위 환경에 적응하여 CoQ10 생산의 가능성과 반추위 발효에 미치는 영향을 판단하였다. 반추위 환경과 가장 유사한 환경을 만들 수 있는 반추위연속배양장치(RSCC)를 이용하여 CoQ10 생산과 반추 발효를 분석하였다. 전체 15일의 배양기간에서 배양이 안정되는 12일 후부터 5% R. sphaeroides 처리한 군과 R. sphaeroides를 처리하지 않은 대조구로 나누어 실험을 진행한 결과, RSCC system시험에서는 NDF, ADF, pH, NH₃-N그리고 미생물 단백질 합성량은 대조구와 유사한 결과를 보였으나, R. sphaeroides가 성장함으로써 반추위에서 분해되지 않는 반추위 비분해성 단백질인 UDP가 대조구에 유의적으로 높게 나타났다. 특히, CoQ10은 대조구에서는 검출되지 않았으나, 처리구에서는 CoQ10 함량이 336.0 mg/l로 높게 나타났다. 이 연구를 통해서 R. sphaeroides는 반추위 내에서 항산화 물질인 CoQ10을 높은 농도로 생산할 수 있음을 확인하였다. 추후 젖소 착유 실험을 통한 CoQ10 우유 전이 실험을 진행하여 기능성 우유 생산을 위한 첨가제 개발에 활용할 예정이다.

• 한국산학기술학회논문지
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• 제17권10호
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• pp.46-53
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• 2016

본 연구는 Q방법론을 통하여 에이즈에 대한 인식을 분석하여, 향후 에이즈 예방캠페인 개발에 기초자료를 제공하는데 그 목적이 있다. 연구의 분석과정은 문헌자료 및 심층면담을 실시하여 Q모집단을 수집하였다. 2014년 10월 20일부터 27일까지 진술문으로 구성된 Q표본을 가지고, 이를 연구 대상자인 P표본이 자가 참조에 따라 분류하는 방식으로 진행되었다. 27개의 Q 표본을 선정하여 20명에게 분류토록 한 결과 모두 3개의 에이즈에 인식에 대한 유형이 도출되었다. 분석된 결과 총 3가지의 유형 즉 제1유형(N=9) : 부정형, 제2유형[(N=6) : 사회적 지지형, 제3유형(N=5) : 이기적 사고형으로 분류되었다. 부정형은 에이즈에 대하여 부정적 견해가 강했고, 사회적 지지형은 우호적 의견을 보였고, 이기적 사고형은 중립적 견해를 보였다. 그리고 각 유형의 특징과 함께 유형별 공통점과 차이점을 살펴보았다. 본 연구의 의미는 인간의 내면을 이해하는데 유용한 Q 방법론을 이용한 연구라는 점과 함께 에이즈 예방 및 관리정책의 효율적 전략을 제안한 점이라 하겠다.

• Journal of Power Electronics
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• 제18권6호
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• pp.1751-1759
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• 2018

This paper presents parallel-connected inverters to achieve accurate proportional power sharing. Due to line impedance mismatch, reactive power cannot be distributed proportionally when using the conventional $P-{\omega}$ and $\mathcal{Q}-E$ droop. In order to realize reactive proportional power sharing, the ratio of the droop coefficients should be inversely proportional to their power-sharing ratios. Meanwhile, the ratio of the line impedance should be inversely proportional to the desired power-sharing ratio, which is very difficult to be met in practice. In order to deal with this issue, a practical control strategy is presented. By measuring the PCC voltage and using the virtual impedance, the output impedance of individual inverters is reconstructed to counteract the line impedance effect. In order to guarantee system stability, a low pass filter is designed to suppress the bandwidth of the line compensation. Finally, the simulation and experimental results are given to verify the effectiveness of the proposed control strategy.