• Journal of Power Electronics
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• 제11권2호
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• pp.120-131
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• 2011

This paper proposes two control strategies for the bidirectional Z-source inverters (BZSI) supplied by batteries for electric vehicle applications. The first control strategy utilizes the indirect field-oriented control (IFOC) method to control the induction motor speed. The proposed speed control strategy is able to control the motor speed from zero to the rated speed with the rated load torque in both motoring and regenerative braking modes. The IFOC is based on PWM voltage modulation with voltage decoupling compensation to insert the shoot-through state into the switching signals using the simple boost shoot-through control method. The parameters of the four PI controllers in the IFOC technique are designed based on the required dynamic specifications. The second control strategy uses a proportional plus resonance (PR) controller in the synchronous reference frame to control the AC current for connecting the BZSI to the grid during the battery charging/discharging mode. In both control strategies, a dual loop controller is proposed to control the capacitor voltage of the BZSI. This controller is designed based on a small signal model of the BZSI using a bode diagram. MATLAB simulations and experimental results verify the validity of the proposed control strategies during motoring, regenerative braking and grid connection operations.

• 한국산학기술학회논문지
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• 제8권2호
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• pp.219-225
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• 2007

AC/DC 컨버터, UPS 등의 적용 분야에서 사용하는 계통 전압의 주파수와 위상 정보는 매우 중요하다. 3상의 경우에는 계통 전압 벡터를 사용하여 계통 전압의 위상 및 주파수 정보를 쉽게 얻을 수 있으나, 단상의 경우에는 계통 전압의 위상 및 주파수 검출이 어렵다. 본 논문에서는 가상 2상 방식을 사용하여 계통 전압의 주파수와 위상을 검출하는 단상 PLL 방법들의 동작을 컴퓨터 시뮬레이션 및 실험을 통하여 살펴보고 각 방법들의 제어 성능을 비교 검토하여 본다.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제1권1호
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• pp.56-61
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• 2001

Activated sludge processes are broadly used in the biological wastewater treatment processes. The activated sludge processes are complex systems because of the many factors such as the variation of influent flowrate and ingredients, the complexity of biological reactions, and the various operation conditions. The main motivation o this research is to develop an intelligent control strategy for activated sludge process (ASP). ASP is a complex and nonlinear dynamic system owing to the characteristic of wastewater, the change in influent flowrate, weather conditions, and so on. The mathematical model of ASP also includes the uncertainty which is a ignored or unconsidered factor from process designers. The ASP model based on Matlabⓡ/Simulinkⓡ is developed in this paper. And the model performance is examined by IWA (International Water Association) and COST (European Cooperation in the filed of Scientific and Technical Research) data. The model tests derive steady-state results of 14 days. In this paper, fuzzy logic control approach is applied to handle DO concentrations. The fuzzy logic controller includes two inputs and one output to adjust air flowrate. The objective function for the optimization, in the implemented evolutionary strategy, is formed with focusing on improving the effluent quality and reducing the operating cost.

• 농촌지도와개발
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• 제27권2호
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• pp.65-74
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• 2020

The study aims to identify the factors affecting business performance of rural tourism operators. For this study, 1,004 questionnaires were collected by field survey of rural tourism operators. The linear multiple regression analysis were used to identify factors affecting performance of rural tourism business. The result indicate that the factors influencing the sales of rural tourism business were in order of owning sales facilities, perception of multi-functional value of agriculture and rural, group promotion, number of rooms, and gender. In the case of gender, it was found that females had a high probability of positively affecting sales. The factors influencing the satisfaction of the rural tourism business were in the order of management strategy, number of days of operation, perception of multi-functional value of agriculture and rural, and business career. In the case of management strategy, it was found that the differentiation strategy have a positively affecting the satisfaction of the rural tourism business. As for the business career, the shorter the career, the higher the probability of positively affecting the satisfaction of the rural tourism business. The results of this study would be useful for establishing strategies to improve the management performance of the rural tourism business.

• 한국경영과학회지
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• 제27권1호
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• pp.95-106
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• 2002

The tilde use of Information Technology (IT), especially the rapid diffusion of the internet, brings us a new paradigm, called "Electronic Commerce," or "Digital Economy." The paradigm is regarded as a business strategy essential to organizations′competitive advantages. Because few studies have been shown in the area of e-strategies, especially in the combined strategies of clicks and mortars, a study of this area is required. The main questions of this study are empirically to validate the usefulness and applicability of a decision roadmap and to analyze the situation of Korean firms in the view of the decision roadmap. Major results of this study are as follows : First, there is an evidence that the roadmap can be applied to Korean firms regardless of their industry and size. Second, the usefulness of the roadmap is proved because companies following the directions of the roadmap show high degree of satisfaction with online sales. Third, Korean companies in general do not achieve an Ideal Integration (or separation), especially In terms of management and operation. In conclusion, this study provides an e-business strategy Planner some guidelines about how to achieve right mix of on-line and off-line business.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제4권6호
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• pp.1169-1193
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• 2010

In this paper, we present and compare two different multiple camera collaboration strategies to reduce false association in finding the correspondence of objects. Collaboration matrices are defined with the required minimum separation for an effective collaboration because homographic lines for objects association are ineffective with the insufficient separation. The first strategy uses the collaboration matrices to select the best pair out of many cameras having the maximum separation to efficiently collaborate on the object association. The association information in selected cameras is propagated to unselected cameras by the global information constructed from the associated targets. While the first strategy requires the long operation time to achieve the high association rate due to the limited view by the best pair, it reduces the computational cost using homographic lines. The second strategy initiates the collaboration process of objects association for all the pairing cases of cameras regardless of the separation. In each collaboration process, only crossed targets by a transformed homographic line from the other collaborating camera generate homographic lines. While the repetitive association processes improve the association performance, the transformation processes of homographic lines increase exponentially. The proposed methods are evaluated with real video sequences and compared in terms of the computational cost and the association performance. The simulation results demonstrate that the proposed methods effectively reduce the false association rate as compared with basic pair-wise collaboration.

• Journal of Power Electronics
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• 제16권6호
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• pp.2099-2108
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• 2016

The cascaded multilevel converter is widely adopted to medium/high voltage and high power electronic applications due to the small harmonic components of the output voltage and the facilitation of modularity. In this paper, the operation principle of a T-type H-bridge topology is investigated in detail, and a carrier phase shifted pulse width modulation (CPS-PWM) based control method is proposed for this topology. Taking a virtual five-level waveform achieved by a unipolar double frequency CPS-PWM as the output object, PWM signals of the T-type H-bridge can be obtained by reverse derivation according to its switching modes. In addition, a control method for the T-type H-bridge based cascaded multilevel converter is introduced. Then a single-phase T-type H-bridge cascaded multilevel static var generator (SVG) prototype is built, and a repetitive controller based compound current control strategy is designed with the DC-link voltage balancing control scheme analyzed. Finally, simulation and experimental results validate the correctness and feasibility of the proposed modulation method and control strategy for T-type H-bridge based cascaded multilevel converters.

• 대한전자공학회논문지TC
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• 제44권7호통권361호
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• pp.112-121
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• 2007

본 논문에서는 중복 구조 시스템을 이용하여 각 프로세서에서의 출력을 비교하여 효율적으로 고장을 탐지하고, 체크포인팅 기법을 적용하여 과도 고장뿐 아니라 영구적 고장을 극복하기 위한 방법을 제안한다. 매 체크포인터에서는 각 프로세서로부터의 출력과 과거 체크포인터에 저장된 데이터를 불러와 서로 비교한 후 과거 체크포인터로 회귀할지 태스크의 수행을 계속 수행할지 결정한다. 과도 고장과 영구 고장이 발생할 수 있는 상황에서 제안된 체크포인팅 기법을 탑재한 중복 구조 시스템을 마코프 모델을 이용하여 모델링한다. 마코프 모델로부터 실시간 태스크가 데드라인 이내에서 성공적으로 수행을 끝낼 확률을 계산하고, 이 확률식을 이용하여 중복구조 시스템에 탑재할 체크포인터 구간을 최적화한다. 최적화된 체크포인터 구간은 태스크의 성공적 수행 확율을 최대화 하도록 선정하였다.

• Journal of Electrical Engineering and Technology
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• 제13권3호
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• pp.1079-1088
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• 2018

A line overload emergency control strategy based on the source-load synergy coefficient is proposed in this paper. First, the definition of the source-load synergy coefficient is introduced. When line overload is detected, the source-load branch synergy coefficient and source-load distribution synergy coefficient are calculated according to the real-time operation mode of the system. Second, the generator tripping and load shedding control node set is determined according to the source-load branch synergy coefficient. And then, according to the line overload condition, the control quantity of each control node is determined using the Double Fitness Particle Swarm Optimization (DFPSO), with minimum system economic loss as the objective function. Thus load shedding for the overloaded line could be realized. On this basis, in order to guarantee continuous and reliable power supply, on the condition that no new line overload is caused, some of the untripped generators are selected according to the source-load distribution synergy coefficient to increase power output. Thus power supply could be restored to some of the shedded loads, and the economic loss caused by emergency control could be minimized. Simulation tests on the IEEE 10-machine 39-bus system verify the effectiveness and feasibility of the proposed strategy.

• Journal of Power Electronics
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• 제15권4호
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• pp.1026-1034
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• 2015

In this paper, a unified control strategy using the current space vector modulation (CSVM) technique is proposed and applied to a bidirectional three-phase DC/AC converter. The operation of the converter changes with the direction of the power flow. In the charging mode, it works as a buck type rectifier; and during the discharging mode, it operates as a boost type inverter, which makes it suitable as an interface between high voltage AC grids and low voltage energy storage devices. This topology has the following advantages: high conversion efficiency, high power factor at the grid side, tight control of the charging current and fast transition between the charging and discharging modes. The operating principle of the mode analysis, the gate signal generation, the general control strategy and the transition from a constant current (CC) to a constant voltage (CV) in the charging mode are discussed. The proposed control strategy has been validated by simulations and experimental results obtained with a 1kW laboratory prototype using supercapacitors as an energy storage device.