• International Journal of Air-Conditioning and Refrigeration
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• 제15권2호
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• pp.61-69
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• 2007

This paper deals with fuzzy control with a feedforward compensator to progress both energy saving and coefficient of performance (COP) in a variable speed refrigeration system. Both the capacity and superheat are controlled simultaneously and independently in the system. By adopting the fuzzy theory, the controller design for the capacity and superheat is possible without depending on a dynamic model of the system. Moreover, the feedforward compensator of the superheat can reduce influence of the interfering loop between the capacity and superheat. Some experiments are conducted to design appropriate fuzzy controller by an iteration manner. The results show that the proposed fuzzy controller with the compensator can establish good control performances for the complicated refrigeration system in spite of its inherent strong non-linearity. Also, the fuzzy control performances were investigated by comparing to the model based PI control experimental results to evaluate transient behavior under the control.

• 한국ITS학회 논문지
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• 제16권2호
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• pp.116-127
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• 2017

도로 상의 안개는 교통류에 영향을 미치는 요인으로 알려져 있다. 이를 해소하기 위한 방안으로 최근 실시간 도로 및 기상조건에 따라 적절한 제한속도를 제공하는 가변제한속도시스템 VSL(Variable Speed Limit)을 도입하여 운영하고 있다. 하지만, VSL은 운전자가 제한속도를 준수하지 않을 경우 차량 간 속도 편차가 증가하여 오히려 교통사고의 위험도를 가중시킬 수 있다. 따라서, 본 연구는 기상조건별 VSL 유 무에 따른 운전자의 가변속도제한의 순응 경향 및 교통특성 분석을 목적으로 한다. 차량 시뮬레이터를 이용한 주행 환경을 구현하여 실험을 수행하였으며 기상조건은 크게 맑음, 안개로 나누었다. 분석 결과, 피험자의 평균 속도는 대부분 제한속도를 순응하였지만 전체적으로 속도 편차는 가변제한속도를 적용할 경우에 감소하는 것으로 분석되었고 특히, 안개가 발생할 경우 더욱 뚜렷하게 감소하는 것으로 나타났다. 기상조건이 운전자의 전방 시거에 영향을 미치면 VSL에 대한 운전자의 순응도는 높아지고, 속도 편차가 감소하여 교통안전성 향상에 도움을 주는 것으로 나타났다. 이는 향후 가변속도제한 운영속도를 산정하는데 기초자료로 사용할 수 있을 것으로 기대된다.

• 전기학회논문지
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• 제65권4호
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• pp.533-538
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• 2016

In a power grid that has a high penetration of wind power, the highly-fluctuating output power of wind turbine generators (WTGs) adversely impacts the power quality in terms of the system frequency. This paper proposes a power smoothing scheme of a variable-speed WTG that can smooth its fluctuating output power caused by varying wind speeds, thereby improving system frequency regulation. To achieve this, an additional loop relying on the frequency deviation that operates in association with the maximum power point tracking control loop, is proposed; its control gain is modified with the rotor speed. For a low rotor speed, to ensure the stable operation of a WTG, the gain is set to be proportional to the square of the rotor speed. For a high rotor speed, to improve the power smoothing capability, the control gain is set to be proportional to the cube of the rotor speed. The performance of the proposed scheme is investigated under varying wind speeds for the IEEE 14-bus system using an EMTP-RV simulator. The simulation results indicate that the proposed scheme can mitigate the output power fluctuation of WTGs caused by varying wind speeds by adjusting the control gain depending on the rotor speed, thereby supporting system frequency regulation.

• 열병합발전
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• 통권74호
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• pp.12-17
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• 2010

• 전기학회논문지P
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• 제55권3호
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• pp.117-122
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• 2006

The paper is proposed artificial neural network(ANN) sensorless control of induction motor drive with fuzzy learning control-fuzzy neural network(FLC-FNN) controller. The hybrid combination of neural network and fuzzy control will produce a powerful representation flexibility and numerical processing capability. Also this paper is proposed. speed control of induction motor using FLC-FNN and estimation of speed using ANN controller. The back Propagation neural network technique is used to provide a real time adaptive estimation of the motor speed. The error between the desired state variable and the actual one is back-propagated to adjust the rotor speed so that the actual state variable will coincide with the desired one. The proposed control algorithm is applied to induction motor drive system controlled FLC-FNN and ANN controller, Also, this paper is proposed the analysis results to verify the effectiveness of the FLC-FNN and ANN controller.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1997년도 전력전자학술대회 논문집
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• pp.357-363
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• 1997

The windup phenomenon appears and results in the performance degradation when the PI controller output is saturated. A new anti-windup PI controller is proposed to improve the control performance of the variable-speed motor drives and it is experimentally applied to the speed control of a vector-controlled induction motor driven by a pulse width modulated(PWM) voltage source inverter (VSI). The integral state is separately controlled corresponding to whether the PI controller output is saturated or not. The experimental results show that the speed response has the much improved performances such as small overshoot and fast settling time over the conventional anti-windup technique. Although the operating speed command is changed, the similar control performance can be obtained by using the PI gains selected in the linear region.

• 전기학회논문지
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• 제58권7호
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• pp.1313-1320
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• 2009

This paper analyzes the steady-state operating characteristics of doubly-fed induction generator(DFIG) and fixed-speed induction generator(FSIG) in wind turbine system. It also presents a modeling and simulation of a grid-connected wind turbine generation system for dynamics analysis on MATLAB/Simulink, and compares the responses between DFIG and FSIG wind turbine systems with respect to wind speed variation, 3-phase fault and 1-phase ground fault of the network. Simulation results show the variations of generator's active/reactive output, rotor speed, terminal voltage, fault current, etc. Case studies demonstrate that DFIG illustrates better performance compared to FSIG.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 심포지엄 논문집 정보 및 제어부문
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• pp.216-218
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• 2006

The paper is proposed high performance control of induction motor drive with adaptive fuzzy logic controller(AFLC). Also, this paper is proposed speed control of induction motor using AFLC and estimation of speed using artificial neural network(ANN) controller. The back propagation neural network technique is used to provide a real time adaptive estimation of the motor speed. The error between the desired state variable and the actual one is back-propagated to adjust the rotor speed, so that the actual state variable will coincide with the desired one. The proposed control algorithm is applied to induction motor drive system controlled AFLC and ANN controller. And this paper is proposed the results to verify the effectiveness of the AFLC and ANN controller.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.736-741
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• 1998

It is well known that an encoder or a resolver is necessary to obtain the position data for speed or position control Generally utilized speed sensors are mal-affected by the EMI, dusty, and high temperature surroundings. Therefore, the speed and position sensorless controls using observers have been studied widely. In this paper, the binary observer which is composed of two feedback regulation loops to control the speed of SRM(Switched Reluctance Motor) is applied. One loop compensates the control input directly like the sliding mode control, and the other one compensates the system parameters indirectly. This observer is constructed on the foundation of variable structure control on the foundation of variable structure control theory and has the inertial term for the varying parameter. The validities of this proposed method is proved by experiments.

• Journal of Biosystems Engineering
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• 제16권3호
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• pp.239-247
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• 1991

This study was conducted to investigate the feasbility of continuously variable V-belt transmission(CVVT) as automatic power transmission system of combine harvesters. An experimental set-up for testing the performance of CVVT and the automatic transmission system was designed and used to analyze the power transmission characteristics of CVVT. The transmission efficiency of CVVT was increased logarithmically with increase of the load of driven shaft, but was not affected by the speed ratios of transmission. More than 80% of transmission efficiency was obtained in the 25N-m load and more of driven-shaft, and the maximum efficiency was 88~91%. When rapid speed change of the CVVT was attempted, the speed of driven shaft was stabilized within about 0.4 seconds after shift operation in both cases of increasing and decreasing of the speed.