• Journal of Power Electronics
• /
• 제10권2호
• /
• pp.203-209
• /
• 2010

This paper describes the development of a three-phase line-interactive DVR with a new sag detection algorithm. The developed detection algorithm has a hybrid structure composed of an instantaneous detector and RMS-variation detectors. The source voltage passes through the sliding-window DFT and RMS calculator, and the instantaneous sag detector. If an instantaneous sag is detected, the RMS variation detector-1 is selected to calculate the RMS variation. The RMS variation detector-2 is selected when the instantaneous sag occurs under the operation of the RMS variation detector-1. The feasibility of the proposed algorithm is verified through computer simulations and experimental work with a prototype of a line-interactive DVR with a 3kVA rating. The line-interactive DVR with the proposed algorithm can compensate for an input voltage sag or an interruption within a 2ms delay. The developed DVR can effectively compensate for a voltage sag or interruption in sensitive loads, such as computers, communications equipment, and automation equipment.

• Smart Structures and Systems
• /
• 제17권6호
• /
• pp.881-901
• /
• 2016

In this study, a method to compensate the effect of temperature variation on impedance responses which are used for prestress-loss monitoring in prestressed concrete (PSC) girders is presented. Firstly, an impedance-based technique using a mountable lead-zirconate-titanate (PZT) interface is presented for prestress-loss monitoring in the local tendon-anchorage member. Secondly, a cross-correlation-based algorithm to compensate the effect of temperature variation in the impedance signatures is outlined. Thirdly, lab-scale experiments are performed on a PSC girder instrumented with a mountable PZT interface at the tendon-anchorage. A series of temperature variation and prestress-loss events are simulated for the lab-scale PSC girder. Finally, the feasibility of the proposed method is experimentally verified for prestress-loss monitoring in the PSC girder under temperature-varying conditions and prestress-loss events.

• 소성∙가공
• /
• 제18권4호
• /
• pp.290-295
• /
• 2009

The roll gap set-up in the finishing mill is one of the most important technologies in the hot plate rolling process. As the target thickness can be obtained by the correct set-up of the roll gap, improving the roll gap set-up technology is very critical for plate thickness accuracy. The main cause of thickness variation in hot plate mills is the non-uniform temperature distribution along the length of the slab. The objective of this study is to adjust the roll gap set-up for the thickness accuracy of plate in hot rolling process considering top-end temperature drop. Therefore this study has concentrated on determining the correct amounts of thickness variation according to top-end temperature drop and roll gap to compensate thickness variation. The control method of roll gap set-up which can improve the thickness accuracy was proposed. The off-line simulation of compensated roll gap significantly decreases top-end thickness variation.

• 전력전자학회논문지
• /
• 제18권4호
• /
• pp.322-332
• /
• 2013

Conventional single-phase series quasi Z-source voltage compensator can not compensate for voltage sag less than 50% that frequently occurs in the industrial field. In this study, single-phase series quasi Z-source voltage sag-swell compensator which can compensate the voltage variation of entire range is proposed. The proposed system is composed of two quasi Z-source AC-AC converters connected in series with output terminal stage. Voltage sag less than 50% could be compensated by the intersection switching control of the upper converter duty ratio and of the upper converter duty ratio. Also the compensation voltage and its flowchart for each compensation mode are presented for entire sag-swell region. To confirm the validity of the proposed system, a DSP(DSP28335) controlled experimental system was manufactured. As a result, the proposed system could compensate for the voltage sag/swell of 20% and 60%. Finally, voltage compensation factor and THD(Total Harmonic Distortion) according to voltage variation and load change were measured, and voltage quality shows a good results.

• 자원ㆍ환경경제연구
• /
• 제23권2호
• /
• pp.281-304
• /
• 2014

친환경 자동차의 보급을 활성화시키기 위해서는 자동차 소비자들을 분석하는 것이 필수적이다. 본 연구는 자동차 소비자들의 특성과 친환경 자동차 선호의 관계를 성별 연령 연료비 중심으로 분석하였다. 설문조사를 이용한 컨조인트법을 이용하여 응답자를 성별 연령 연료비의 기준으로 구분하여 친환경 자동차의 속성이 효용에 미치는 영향을 분석한 결과, 응답자의 특성에 따라 자동차의 속성에 대한 한계효용에 유의한 차이가 있는 것을 발견할 수 있었다. 또한 자동차의 속성이 응답자의 효용수준에 미치는 영향이 같을 지라도 보상변이로 표출될 때는 다르게 나타날 수 있고, 반대로 효용수준에 미치는 영향이 다를지라도 보상변이는 같은 수준으로 나타날 수 있다는 것을 알 수 있었다. 한계효용은 주관적인 기준이기 때문에 응답자마다 다를 수 있는 반면, 보상변이는 상충관계를 이용한 객관적인 기준이 될 수 있기 때문에 응답자 특성에 따른 실질적인 선호의 차이를 나타낼 수 있다. 보상변이에 의하면 남성과 장년이 연비가 높은 차량을 더욱 선호하는 것으로 나타났다. 고유류비 소비자는 저유류비 소비자보다 주유시간에 더욱 민감하에 반응하고, 휘발유 차량은 청년층에서 더욱 선호된다.

• Journal of Power Electronics
• /
• 제13권5호
• /
• pp.854-860
• /
• 2013

The voltage variation problem at the point of common coupling (PCC) in a grid-connected wind turbine is investigated. The voltage variation problem is one of the most frequent power quality issues for the grid connection of large amounts of input power in a weak grid. Through the simplified modeling of the wind turbine and power network, the magnitude of PCC voltage variation is calculated by using the equivalent circuit parameters and output power of the wind turbine. The required amount of reactive power that can compensate the voltage variation is also presented analytically by using the vector diagram method. The proposed calculation and compensation method of the PCC voltage variation is verified by computer simulations and experiments.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
• /
• pp.249-252
• /
• 1996

The inverted pendulum system is mechanical system which can handle the modern control theory and practical applications. In theoretical field, it is used as the experimental device identifying the effects of control method and in applicative field. There are difficulties in designing or linearizing the practical controller because it is so sensitive to the parameter variation and has the highly non-linear characteristic. In this paper, we suggested the systems which compensate the non-linearity throughout the internal control method and designed controller which is robust to the parameter variation using sliding mode.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1993년도 하계학술대회 논문집 B
• /
• pp.686-688
• /
• 1993

This paper proposes a robust speed control algorithm of Induction Motor. The main idea of this paper is to compensate the torque component of motor current with load torque observer and feedforward control. The speed response of the conventional PI controller is affected by variation of system parameters. However the proposed system has robust characteristics against the variation of system parameters. The simulation results and experiment prove the validity of proposed algorithm.

• 한국기계가공학회지
• /
• 제14권3호
• /
• pp.57-64
• /
• 2015

In this paper, a model reference adaptive control (MRAC) scheme is applied for the precise and robust motion control of a pneumatic system with load variation. The reference model for MRAC is designed systematically using linear quadratic Gaussian control with loop transfer recovery (LQG/LTR). The sigmoid function of inverse velocity is used to compensate for the nonlinear friction force between the sliding parts. The experimental results show that MRAC effectively overcame the limit of the PID controller when there was unknown disturbance, including abrupt load variation and model uncertainty in the pneumatic control system.

• Journal of Power Electronics
• /
• 제17권2호
• /
• pp.464-475
• /
• 2017

This study examines a P+multi resonant-based voltage control for voltage harmonics compensation under the islanded mode of a microgrid. In islanded mode, the inverter is defined as a voltage source to supply the full local load demand without the connection to the grid. On the other hand, the output voltage waveform is distorted by the negative and zero sequence components and current harmonics due to the unbalanced and nonlinear loads. In this paper, the P+multi resonant controller is used to compensate for the voltage harmonics. The gain tuning method is assessed by the tendency analysis of the controller as the variation of gain. In addition, this study analyzes the slight voltage magnitude drop due to the practical form of the P+multi resonant and proposes a counter method to solve this problem by adding the PI-based voltage restoration method. The proposed P+multi resonant controller to compensate for the voltage harmonics is verified through the PSIM simulation and experimental results.