• JSTS:Journal of Semiconductor Technology and Science
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• 제16권1호
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• pp.58-69
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• 2016

This paper describes the design and implementation of a new diode clamped multilevel inverter for variable frequency drive. The diode clamp multilevel inverter has been widely used for low power, high voltage applications due to its superior performance. However, it has some limitations such as increased number of switching devices and complex PWM control. In this paper, a new topology is proposed. New topology requires only (N-1) switching devices and (N-3) clamping diodes compared to existing topology. A modified APO-PWM control method is used to generate gate pulses for inverter. The proposed inverter topology is coupled with single phase induction motor and its performance is tested by MATLAB simulation. Finally, a prototype model has built and its performance is tested with single phase variable frequency drive.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제37회 추계학술대회논문집
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• pp.942-948
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• 2011

고체추진기관은 구조가 비교적 간단하고 장기적 저장성이 우수한 반면에 일반적으로 추력의 조절등에 한계성을 가지고 있다. 본 논문에서는 구현의 용이함과 에너지 효율성이 좋은 on-off 제어기법을 이용한 가변추력 고체추진 기관의 압력 제어를 위한 제어기를 소개한다. 연소기 내 압력제어를위해 질량보존만을 고려한 추진기관의 연소기 내 압력변화 모델에 대하여 고전적인 비례-적분 제어기와 같은 연속적 제어 기법과 PWM, PWPFM과 같은 on-off 제어기를 설계하고 시뮬레이션을 통해 결과를 비교한다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(2)
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• pp.519-523
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• 2004

In this paper, a simple power control scheme of Class-D inverter, which is varied duty cycle of fixed frequency to desired output power. It is more suitable and acceptable for high-frequency induction heating (IH) jar applications. The proposed control scheme has the advantages of not only wide power regulation range but also ease to control output power. Also it can achieve the stable and efficient Zero-Voltage-Switching (ZVS) in whole load range. The control principles of proposed method are described in detail and its validity is verified trough simulations results on 38.5kHz IGBT for induction heating rated on 1.6kW with constant frequency variable power.

• Journal of Power Electronics
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• 제14권3호
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• pp.580-591
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• 2014

This paper concerns a three-phase self-excited induction generator used for autonomous power generation. It presents a robust control strategy which makes it possible to maintain the frequency quasi constant during the voltage regulation without any control loop on this variable. This strategy, which also prevents the machine disengagement, uses as power converter a simple dimmer. The obtained theoretical and/or numerical results are validated on a laboratory test bench that allows the analysis of this control law effectiveness.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 정기총회 및 창립40주년기념 학술대회 학회본부
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• pp.552-554
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• 1987

A design principles of discontinuous control are studied and then are applied to position control of D. C. sevo drive fed by a four-quadrant chopper. Variable structure control with sliding mode gives fast dynamic response with no overshoot. And the resulting system bas good robust properties independent of the wide variations of electrical, mechanical parameters and external disturbances without any system identification. But the high frequency chatter component of control input in the sliding mode is undesirarable. A continuous control law that is a approximation to discontinuous control law is used for design.

• Journal of Electrical Engineering and Technology
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• 제12권6호
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• pp.2268-2277
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• 2017

As constantly increasing wind power penetrates power grid, wind power plants (WPPs) are exerting a direct influence on the traditional power system. Most of WPPs are using variable speed constant frequency (VSCF) wind turbines equipped with doubly fed induction generators (DFIGs) due to their high efficiency over other wind turbine generators (WTGs). Therefore, the analysis of DFIG has attracted considerable attention. Precisely measuring optimum reference speed is basis of utilized maximum wind power in electric power generation. If the measurement of wind speed can be easily taken, the reference of rotation speed can be easily calculated by known system's parameters. However, considering the varying wind speed at different locations of blade, the turbulence and tower shadow also increase the difficulty of its measurement. The aim of this study is to design fuzzy controllers to replace the wind speedometer to track the optimum generator speed based on the errors of generator output power and rotation speed in varying wind speed. Besides, this paper proposes the fuzzy adaptive PID control to replace traditional PID control under rated wind speed in variable-pitch wind turbine, which can detect and analyze important aspects, such as unforeseeable conditions, parameters delay and interference in the control process, and conducts online optimal adjustment of PID parameters to fulfill the requirement of variable pitch control system.

• 유공압시스템학회논문집
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• 제7권3호
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• pp.20-27
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• 2010

A vehicle suspension system performs two functions, the ride quality and the stability, which conflict with each other. An active suspension system has an external energy source, from which energy is always supplied to the system for continuous control of vehicle motion. Therefore, an active suspension system can have even more improved performance. Some control laws have been proposed for active suspension system, but in this paper, an optimal variable structure control(VSC) is proposed. The VSC method is well suited for a class of nonlinear system and can address the robustness issues to constant modelling errors and disturbances. This paper develops an optimal VSC controller and compares its performance to those of a passive suspension system and an active suspension system with an optimal controller. The transient and frequency responses are analyzed respectively.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 정기총회 및 창립40주년기념 학술대회 학회본부
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• pp.362-366
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• 1987

The amount of inflowing Air into the boiler has controlled by manipulating the opening of valve, damper and vane, as fan operated by induction motor operats at constant speed, but these control methods are not efficient. Thus VVVf(Variable Voltage Variable Frequency) control of fan has selected to improve efficiency and to acquire power savings. Control system of Air Flow is affected by nonlinearity caused by load variation, vane opening, etc. The analysis of control parameter causing nonlinearity is needed to acquire optimal control and excellent transient response. This paper provides modeling of boiler with various load conditions and vane opening, and analysis of this system.

• Journal of Power Electronics
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• 제5권4호
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• pp.282-288
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• 2005

In this paper, a new speed sensorless induction motor scheme which can estimate rotor speed and rotor resistance simultaneously is presented. The rotor flux with a low frequency sinusoidal waveform is used to conduct on-line simultaneous estimation of the rotor speed and rotor resistance. Hence the proposed sensorless control method is robust to rotor resistance variations. Also, the control scheme has no current minor loop to determine voltage references. It contributes to good control performance at low speeds. Some simulation results supported by experiments are given to show the effectiveness of this method.

• International Journal of Fluid Machinery and Systems
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• 제2권4호
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• pp.334-345
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• 2009

Pumped storage power plants are playing a significant role in the contribution to the stabilization of an electrical grid, above all by stable operation and fast reaction to sudden load respectively frequency changes. Optimized efficiency and smooth running characteristics both in pump and turbine operation, improved stability for synchronization in turbine mode, load control in pump mode operation and also short reaction times may be achieved using adjustable speed power units. Such variable speed power plants are applicable for high variations of head (e.g. important for low head pump-turbine projects). Due to the rapid development of power semiconductors and frequency converter technology, feasible solutions can be provided even for large hydro power units. Suitable control strategies as well as clear design criteria contribute significantly to the optimal usage of the pump turbine and motor-generators. The SIMSEN tool for dynamic simulations has been used for comparative investigations of different configurations regarding the power converter topology, types of semiconductors and types of motor-generators including the coupling to the hydraulic system. A brief overview of the advantages & disadvantages of the different solutions can also be found in this paper. Using this approach, a customized solution minimizing cost and exploiting the maximum usage of the pump-turbine unit can be developed in the planning stage of new and modernization pump storage projects.