• 드라이브 ㆍ 컨트롤
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• 제15권1호
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• pp.16-27
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• 2018

Hydraulic torque load simulator is essential to test and qualify the performance of various angle control systems. Typically a flapper-type second stage servovalve is applied to the load simulator, but here the direct drive servovalve, which is a kind of one-stage valve and affected by the large flow force, is applied. Since the torque load is applied not to the stationary shaft but to the rotating shaft of the angle control system, the controlled torque of load simulator is not accurate due to the rotating speed of the angle control system. A feedforward compensator is designed and applied to minimize the disturbance-like effect. A mathematical model is derived and linearized to analyze the stability, accuracy and responsiveness of the torque load simulator. The parameter effects of a controller, servovalve, hydraulic motor, rotating spring shaft are analyzed and summarized. The goodness of the linear analysis is verified by the digital computer simulations using both the linear and nonlinear mathematical models.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(2)
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• pp.663-666
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• 2003

This paper presents a speed controller method based on the disturbance torque observer of high performance brushless DC (BLDC) motor drives. In case of the speed control of robot arms and tracking applications with lower stiffness, we cannot design the speed controller gain to be very large from tile viewpoint of the system stability. Thus, the feedforward compensator using disturbance torque observer was proposed. This method can improve the speed characteristic without increasing the speed controller gain. The enhanced speed control performance can be achieved and the speed response against the disturbance torque can be Improved for high-performance BLDC motor drive systems in which the bandwidth of tile speed controller cannot be made large enough. Consequently, speed control for high-performance BLDC motor drives become improved. The simulation results for BLDC motor drive systems confirm the validity of the proposed method.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 전력전자학술대회
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• pp.144-146
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• 2018

In order to meet the harmonics standards such as IEEE 519 and P1547 the output quality of a grid connected inverter should satisfy a certain level of Total Harmonic Distortion (THD) value. However, the output quality of an inverter gets degraded due to the grid voltage harmonics, the dead time effects and the nonlinearity of the switches, which all contributes to a higher THD value of the output. In order to meet the required THD value for the inverter output under the distorted grid condition the use of harmonic controller is essential. In this paper a novel feedforward harmonic compensation method is proposed in order to effectively eliminate the low order harmonics in the inverter current to the grid. In the proposed method, unlike the conventional harmonic control methods, the hamonic components are directly compensated by the feedforward terms generated by the PR controller with the grid current in the stationary frame. The proposed method is simple in implementation but powerful in eliminating the harmonics from the output. The effectiveness of proposed method is verified through the PSIM simulation and the experiments with a 5kW single phase grid connected inverter.

• 대한전자공학회논문지TC
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• 제38권1호
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• pp.20-26
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• 2001

고출력 증폭기의 선형화 방법 중 Predistorter 방식은 크기가 작고, 전력 효율이 좋아 고출력 증폭기 선형화에 많이 이용된다. 본 논문에서는 새로운 측정 방법을 이용하여 고출력 증폭기에서 발생하는 혼변조 신호와 Predistorter의 혼변조 신호가 결합하는 경우에 Predistorter의 혼변조 신호의 세기와 위상 변화에 따른 고출력 증폭기에서의 혼변조 신호 감쇠량을 실험적 방법을 통해 추정하였다. 결과적으로 동일한 혼변조 신호, 결합 조건(세기와 위상)의 Predistorter의 선형화 방법은 서로 다른 경로의 신호 결함을 하는 Feedforward 선형화 방법보다 5dB 정도의 혼변조 신호 감쇠량이 낮음을 확인하였다.

• 반도체디스플레이기술학회지
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• 제23권1호
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• pp.1-6
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• 2024

Recently, artificial neural networks have been playing a crucial role and advancing across various fields. Artificial neural networks are typically categorized into feedforward neural networks and recurrent neural networks. However, feedforward neural networks are primarily used for processing static spatial patterns such as image recognition and object detection. They are not suitable for handling temporal signals. Recurrent neural networks, on the other hand, face the challenges of complex training procedures and requiring significant computational power. In this paper, we propose memristors suitable for an advanced form of recurrent neural networks called reservoir computing systems, utilizing a mask processor. Using the characteristic equations of Ti/TiOx/TaOy/Pt, Pt/TiOx/Pt, and Ag/ZnO-NW/Pt memristors, we generated current-voltage curves to verify their memristive behavior through the confirmation of hysteresis. Subsequently, we trained and inferred reservoir computing systems using these memristors with the NIST TI-46 database. Among these systems, the accuracy of the reservoir computing system based on Ti/TiOx/TaOy/Pt memristors reached 99%, confirming the Ti/TiOx/TaOy/Pt memristor structure's suitability for inferring speech recognition tasks.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2007년도 추계학술대회 논문집
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• pp.279-285
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• 2007

Since the residential load is an AC load and the output of solar cell is a DC power, the photovoltaic system needs the DC/AC converter to utilize solar cell. In case of driving to interact with utility line, in order to operate at unity power factor, converter must provide the sinusoidal wave current and voltage with same phase of utility line. Since output of solar cell is greatly fluctuated by insolation, it is necessary that the operation of solar cell output in the range of the vicinity of maximum power point. In this paper, DC/AC converter is three phase PWM converter with smoothing reactor. And then, feedforward control used to obtain a superior characteristic for current control and digital PLL circuit used to detect the phase of utility line.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.420-425
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• 1996

In this paper a robust speed controller for an induction motor is proposed. The speed controller consists or a fuzzy sliding adaptive controller(FSAC) and a sliding mode torque observer(SMTO). FSAC removes the problem or oscillations caused by discontinuous inputs of the sliding mode controller. The controller also provides robust characteristics against parameter and sampling time variations. Although, however, the performance of FSAC is better than PI controller and fuzzy controller in robustness, it generates the problem of slow response time. To alleviate this problem, a compensator, which performs feedforward control using torque signals produced by SMTO, is added. The simulation and hardware implementation results show that the proposed system is robust to the load disturbance, parameter variations, and measurement noises.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.830-835
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• 1998

This paper describes a new digital control method of 3-phase PWM inverter with LC filter for uninterruptible power supply(UPS). The overall control system is based on the dead beat control, which has the minor loop of current control within the voltage control major loop. In this paper, the full-order disturbance observer is proposed to compensate the disturbances generated due to a sudden change of load currents. The proposed disturbance observer is composed of dead beat observer which estimates state values within a finite time, and cancels the disturbances by adding feedforward compensation loop in the control system. In addition, on order to remove a defect of oscillation generated in output of conventional dead beat controller, a modified dead beat algorithm is proposed in this paper.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 추계학술대회 논문집
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• pp.36-40
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• 2003

On analyzing the power circuit of a DVR system, control limitations and control targets are presented for the voltage compensation in DVRs. The control delay in digital controllers increases the dimension of the system transfer function one degree higher which makes the control system more complicate and more unstable. Based on the power stage analysis, a novel controller for the compensation voltages in DVRs is proposed by a feedforward control scheme. Proposed controller works well with the time delay in the digital control system. This paper also proposes a guide line to design the control gain, appropriate output filter parameters and inverter switching frequency for DVRs in digital controllers. Proposed theory is verified by an experimental DVR system with a typical digital controller.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2014년도 전력전자학술대회 논문집
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• pp.253-254
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• 2014

본 논문에서는 무정전전원장치(UPS : Uninterruptible Power Supply 이하 UPS)에서 사용되는 단상인버터의 전압 제어기의 낮은 대역폭으로 인하여 발생될 수 있는 전압 위상 지연 문제를 해결한다. 제안하는 방법은 전압 명령에 대한 전향보상을 이용한 새로운 전압 제어기를 제안하고 이를 MATLAB Simulink를 사용한 시뮬레이션을 통하여 효과를 입증하였다.