• 전력전자학회:학술대회논문집
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• 전력전자학회 2019년도 추계학술대회
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• pp.200-201
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• 2019

Due to uncontrollability and non-repeatability of natural irradiation and temperature, the solar array simulator (SAS) is required to conduct the MPPT power processing experiments precisely. However, the nonlinearity of PV curve characteristic is a crucial task for the control of SAS. In the literature, this issue is addressed by many authors and various methods are proposed. However, stability analysis of SAS is not enough to evaluate the control performance. In this paper, the limitations of conventional SAS are studied according to the small signal model. By using the proposed approach, the performance of two different control method for SAS system are analyzed and compared.

• Transactions on Control, Automation and Systems Engineering
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• 제4권1호
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• pp.38-42
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• 2002

Conditions are discussed for operating a dissymmetric human master-small (or micro) slave system in best (large position gain-small velocity gain) conditions allowing higher operator dexterity when real effects (joint compliance, link flexion delay and transmission distortion) are taken into account. It is shown that position PD feedback law advantage for ideal case no longer holds, and that more complicated feedback law depending on real effects has to be implemented with adapted transmission line. Drawback is slowdown of master slave interaction, suggesting to use more advanced predictive methods for the master and more intelligent control law for the slave.

• 제어로봇시스템학회논문지
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• 제22권7호
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• pp.513-518
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• 2016

The piezoelectric actuating device is known for its large power density and simple structure. It can generate a larger force than a conventional actuator and has also wide bandwidth with fast response in a compact size. To control the piezoelectric actuator, we need an analog signal conditioning circuit as well as digital microcontrollers. Conventional microcontrollers are not equipped with an analog part and need digital-to-analog converters, which makes the system bulky compared with the small size of piezoelectric devices. To overcome these weaknesses, we are developing a single-chip controller that can handle analog and digital signals simultaneously using mixed-signal FPGA technology. This gives more flexibility than traditional fixed-function microcontrollers, and the control speed can be increased greatly due to the parallel processing characteristics of the FPGA. In this paper, we developed a floating-point multiplier, PWM generator, 80-kHz power control loop, and 1-kHz position feedback control loop using a single mixed-signal FPGA. It takes only 50 ns for single floating-point multiplication. The PWM generator gives two outputs to control the charging and discharging of the high-voltage output capacitor. Through experimentation and simulation, it is demonstrated that the designed control loops work properly in a real environment.

• Journal of Biosystems Engineering
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• 제25권5호
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• pp.351-358
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• 2000

This study was conducted to develop a speed control system of a DC motor which drove a barley seeder mounted on a combine harvester. Barley seeder mounted on a combine has been known to reduce labor and cost of barley cultivation. However, development of the seeder has been unsuccessful because the combine, a dedicated rice and barley harvester has not enough space and proper power take-off for barley seeder. To develop a barley seeder, small powered motor speed controller was required. A proximity sensor for detecting working speed of the combine and a programmable one board microprocessor was used to develope a control system. Motor parameters and motor constant, relationship between seeding rate, motor speed, groove volumes of a tested roller, torque were measured. The proximity sensor sent a frequency signal to the microprocessor. In laboratory experiments, the excitation voltage of the motor was shown not to be proportional to the size of pulse width (duty ratio). A table transforming frequency signal, that represented for working speed to proper pulse width was developed from seeding rate experiments. However, seeding rate at low frequency signal was not proportional to the working speed. Seeding rate control proportional to the frequency signal was achieved by shifting of the frequency signal.

• 전력전자학회논문지
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• 제3권3호
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• pp.231-239
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• 1998

본 논문에서는 대용량에 적합한 영전압 스위칭 전브리지 PWM 직류/직류 변한기의 동특성 해석과 제어 루프의 설계에 대해 논하였다. 전압을 제어하기 위한 위상전이제어의 효과와 영전압 스위칭을 위한 변압기의 누설인덕턴스, FET의 적합 커패시턴스의 이용효과를 고려한 소신호 모델을 유도하였다. 이 소신호 모델은 PWM 벅 변환기의 등가모델에 시비율 변조에 대한 두 개의 종속 전원을 추가함으로써 모델링할 수 있다. 소신호 해석 결과를 근거로 하여 2-극점, 1-영점 보상회로를 사용한 전압제어기를 설계하였다. 설계된 제어기의 타당성을 검증하기 위해서 개루프 시스템과 폐루프 시스템의 소신호 해석결과를 비교하였으며, 2kW급 부하실험으로 설계한 전압제어기의 동특성이 우수함을 실험적으로 입증하였다.

• 융합신호처리학회논문지
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• 제12권3호
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• pp.222-227
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• 2011

2층 트레킹 방식을 적용한 PV 태양광 발전 유닛은 고정형에 비해 동일 면적의 패널로 140% 이상의 발전 출력을 얻을 수 있다는 것이 밝혀져 있다. 그러나 이 방식은 고정형 또는 1축 제어방식에 비해 트레킹 기구가 복잡하고 제어전력이 커서 소 출력 PV 유닛에 있어서는 상대적으로 불리하다. 본 논문에서는 소형 PV 발전유닛의 경제성을 개선하는 방법으로 복수개의 소 출력 PV 유닛을 묶어서 1개소의 중앙제어장치에서 간헐식으로 원격제어 함으로써 각 유닛의 트레킹 관련 기구를 간소화 시키는 동시에 제어전력을 경감 시킬 수 있음을 소개한다. 또한 대규모의 PV 발전 플랜트를 건설하기 어려운 환경에서 적합한 방식으로 활용할 수 있음을 소개한다.

• 한국통신학회논문지
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• 제18권10호
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• pp.1413-1421
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• 1993

제어대상에 제한된 제어 입력 신호에 대하여 좋지 않은 효과를 줄일 수 있고, 이것은 제어 입력 신호의 억제 되어진 부분을 보상하는 보상 루프를 구성함으로서 실행된다. 보상 루프의 보상기 설계와 안정도 조사는 Kalman-Szego-보조정리를 이용하고 그 결과로서 작은 오차신호에 대해서도 제어대상에 대한 제어 입력 신호의 많은 범위를 활용하는 것이 가능하다.

• Journal of the Korean Data and Information Science Society
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• 제28권2호
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• pp.451-459
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• 2017

There are many researches showing that when a process change has occurred, variable sampling intervals (VSI) control chart is better than the fixed sampling interval (FSI) control chart in terms of reducing the required time to signal. When the process engineers use VSI control procedure, frequent switching between different sampling intervals can be a complicating factor. However, average number of samples to signal (ANSS), which is the amount of required samples to signal, and average time to signal (ATS) do not provide any control statistics about switching performances of VSI charts. In this study, we evaluate numerical switching performances of multivariate VSI EWMA chart including average number of switches to signal (ANSW) and average switching rate (ASWR). In addition, numerical study has been carried out to examine how to improve the performance of considered chart with accumulate-combine approach under several different smoothing constant and sample size. In conclusion, process engineers, who want to manage the correlation coefficients of related quality variables, are recommended to make sample size as large and smoothing constant as small as possible under permission of process conditions.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제5B권1호
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• pp.78-83
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• 2005

Currently in Japan, the use of the small wind turbine is an upward trend. There are already many well established small wind turbine generators in use and their various failures have been reported. The most commonly sighted failure is blade damage. Thus the research purpose was set to develop a simple failure diagnostic system, where an Acoustic Emission (AE) signal was produced from the failure part of a blade which was measured by AE sensor. The failure diagnostic technique was thoroughly examined. Concurrently, the damage part of the blade was imitated, the AE signal was measured, and a FFT(Fast Fourier Transform) analysis was carried out, and was compared with the output characteristic. When one sheet of a blade was damaged 40mm or more, the level was computed at which failure could be diagnosed.

• Journal of Electrical Engineering and Technology
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• 제11권4호
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• pp.801-809
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• 2016

The electrically excited synchronous generator (EESG) is applied in wind turbine systems recently. In an EESG control system, electrical torque is affected by stator flux and rotor current. So the control system is more complicated than that of the permanent-magnet synchronous generator (PMSG). Thus, the higher demanding of the control system is required especially in case of wind turbine mechanical resonance. In this paper, the mechanism of rotor speed resonant phenomenon is introduced from the viewpoint of mechanics firstly, and the characteristics of an effective damping torque are illustrated through system eigenvalues analysis. Considering the variables are tightly coupled, the four-order small signal equation for torque is derived considering stator and rotor control systems with regulators, and the bode plot of the closed loop transfer function is analyzed. According to the four-order mathematical equation, the stator flux, stator current, and electrical torque responses are derived by torque reference step and ramp in MATLAB from a pure mathematical deduction, which is identical with the responses in PSCAD/EMTDC simulation results. At last, the simulation studies are carried out in PSCAD software package to verify the resonant damping control strategy used in the EESG wind turbine system.