• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 A
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• pp.109-111
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• 2001

Modern power grids are becoming more and more stressed with the load demands increasing continually. Therefore large stressed power systems exhibit complicated dynamic behavior when subjected to small disturbance. Especially, it is needed to analyze special conditions which make small signal stability structure varied according to operating conditions. This paper shows that the relation between small signal stability and operating conditions can be predicted well using node-focus point and 1:1 resonance point. Also, the weak point which limits operating range can be identified by the analysis of resonance condition. The proposed method is applied to test systems, and the results illustrate its capabilities.

• 전기학회논문지
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• 제65권4호
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• pp.593-600
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• 2016

The solar array regulator for low earth orbit satellites controls a operating point of solar array for suppling electric power to the battery and the other units. Because the control object is reversed, the new approach for large and small signal analysis is needed despite using buck-converter for power stage. In this paper, the steady state analysis of solar array regulator is performed in continuous conduction mode and discontinuous conduction mode, and the border condition for each mode is established. Also, the small signal model of solar array regulator is established in discontinuous conduction mode. Experiments are carried on in worst condition which the solar array regulator can face with discontinuous conduction mode. The results show that the solar array regulator is in stable.

• 대한전기학회논문지:전력기술부문A
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• 제52권9호
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• pp.487-492
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• 2003

This paper analyzes an eigenvalue distribution and enhancement of the small signal stabiligy when an Unified Power Flow Controller (UPFC) modeling is connected into the multi-machine power system. Recently a lot of attention has been paid to the subject of dynamic stability. It deals with analysis of eigenvalue sensitivities with respect to parameters of UPFC Controller and damping of interarea and local electromechanical oscillation modes using UPFC Controller. It provides an insight and understanding in the basic characteristics of damping effects of UPFC Controller and shows a very stable frequency response via UPFC in test model. The series branch of the UPFC is designed to damp the power oscillation during transients, while the shunt branch aims at maintaining the bus voltage and angle. Comprehensive time-domain simulation studies using PSS/E show that the proposed robost UPFC controller can enhance the small signal stability efficiently in spite of the variations of power system operating conditions.

• 한국화재소방학회논문지
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• 제27권1호
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• pp.14-19
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• 2013

본 논문은 소형 선박의 비상재난 발생 시 외부 VHF 장비와 연동하여 재난 상황을 자동으로 속보하는 기능을 수행하는 소형 선박용 재난자동속보장치에 대한 내용이다. 재난자동속보장치는 소형 선박의 재난 발생을 방지 또는 신속 대응하기 위한 시스템인 소형 선박재난분석시스템의 일부 장치에 해당하는 것으로서 선박재난분석시스템으로부터 재난 인지 신호와 GPS 위치 정보를 입력 받는다. 비상 상황 발생 시 위치 정보를 구조 요청의 음성 신호로 변환하여 외부 VHF 장비를 통해 송출한다. VHF 장비와 재난자동속보장치가 물에 잠기기 전까지 계속적인 음성 구조 신호를 송출할 수 있도록 한다. 본 연구를 통해 소형선박에 발생할 수 있는 갑작스런 재난상황의 대응과 인명손실을 예방할 수 있으리라 기대한다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.609-614
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• 1998

A new small signal modeling of an average current mode control is proposed. In order to analyze the characteristics of the control scheme, the discrete and continuous time small signal models are derived. The derivation are mainly come from the analysis of the sampling effect presented in the current control loop. By the mathematical interpretation of practical sampler representing the sampling effect of a current control loop, the small signal models of an average current mode control can be easily derived. The instability of the current control loop, which gives rise to the subharmonic oscillation, can be identified by the proposed models. To show the usefulness of the proposed models, the simulation and experiment are carried out. The results show that the predicted results by the proposed model are much better agreed with the measured ones than that of the conventional model, even though the high gain of the compensation network of a current control loop is employed.

• Journal of Power Electronics
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• 제12권3호
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• pp.399-409
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• 2012

In DC-DC Buck converters with average current mode control, the current loop compensator provides additional design freedom to enhance the converter current loop performance. On the other hand, the current loop circuit elements append substantial amount of complexity to not only the inner current loop but also the outer voltage loop, which makes it demanding to quantify circuit and operating parameter effects on the small-signal dynamics of such converters. Despite the difficulty, it is shown in this paper that parameter effects can be analyzed satisfactorily by using an existing small-signal model in conjunction with a newly proposed simplified alternative. As a result of the study, new insight into average current mode control is uncovered and discussed quantitatively. Measurable experimental results on a prototype averaged-current-mode-controlled Buck converter are provided to facilitate the analytical study with good correlation.

• Journal of Power Electronics
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• 제9권5호
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• pp.757-771
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• 2009

This paper proposes a systematic approach to the modeling of the small-signal characteristics of three-phase bridge boost rectifiers under non-sinusoidal conditions. The main obstacle to the conventional synchronous d-q frame modeling approach is that it is unable to identify a steady-state under non-sinusoidal conditions. However, for most applications under non-sinusoidal conditions, the current loops of boost rectifiers are designed to have a bandwidth that is much higher than typical harmonics frequencies in order to achieve good current control for these harmonic components. Therefore a quasi-static method is applied to the proposed modeling approach. The converter small-signal characteristics developed from conventional synchronous frame modeling under different operating points are investigated and a worst case point is then located for the current loop design. Both qualitative and quantitative analyses are presented. It is observed that operating points influence the converter low frequency characteristics but hardly affect the dominant poles. The relationship between power stage parameters, system poles and zeroes is also presented which offers good support for the system design. Both the simulation and experimental results verified the analysis and proposed modeling approach. Finally, the practical case of a parallel active power filter is studied to present the modeling approach and the resultant regulator design procedure. The system performance further verifies the whole analysis.

• 전력전자학회논문지
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• 제19권5호
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• pp.422-430
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• 2014

This study proposes a small-signal model and control design for a two-stage DC-DC-AC converter to investigate its dynamic characteristics in relation to battery energy storage system. When the circuit analysis of the two-stage DC-DC-AC converter is attempted simultaneously, the mathematical procedure of deriving the dynamic equation is complex and difficult. The main idea of modeling the two-stage DC-DC-AC converter states that this topology is separated into a bidirectional DC-DC converter and a single-phase inverter with an equivalent current source corresponding to that of the inverter or converter. The dynamic equations for the separated converter and inverter are then derived using the state-space averaging technique. The procedures of building the small-signal model of the two-stage DC-DC-AC converter are described in detail. Based on the derived small-signal model, the individual controllers are designed through a frequency-domain analysis. The simulation and experimental results verify the validity of the proposed modeling approach and controller design.

• 융합신호처리학회논문지
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• 제12권3호
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• pp.217-221
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• 2011

GaAs 나 InP 기반의 HEMT(High Electron Mobility Transistor)들은 우수한 마이크로파 및 밀리미터파 주파수 특성 및 이에 따른 우수한 저잡음 특성을 가지고 있다. GaAs 기반 MHEMT(Metamorphic HEMT)는 InP 기반의 HEMT에 비해 비용 측면에서 커다란 장점을 가지고 있다. 본 논문에서는 마이크로파 및 밀리미터파 응용 시스템에 필수적인 MHEMT의 RF 특성을 예측 평가하기 위하여 MHEMT의 RF 소신호 특성 회로를 시뮬레이션하고 분석하였다. 본 논문에서의 시뮬레이션을 통한 RF 소신호 주파수 분석은 MHEMT를 이용한 밀리미터파 응용 시스템 설계에 도움을 제공할 수 있을 것으로 기대된다.

• 전력전자학회논문지
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• 제20권2호
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• pp.167-174
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• 2015

This study describes how digital time delay deteriorates control performance in zero voltage switching (ZVS) phase-shifted full bridge (PSFB) converter. The small-signal model of the ZVS PSFB converter is derived from the buck-converter small-signal model. Digital time delay effects have been considered according to the digital sampling methods. The analysis verifies that digital time delays reduce the stability margin of the converter, and the double sampling technique exhibits better performance than the single sampling technique. Both simulation and experimental results based on 250 W ZVS PSFB confirm the validity of the analyses performed in the study.