• 한국태양에너지학회 논문집
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• 제27권2호
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• pp.37-44
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• 2007

As photovoltaic(PV) power generation system becomes more common, it will be necessary to investigate islanding detection method for PV systems. Islanding of PV systems can cause a variety of problems and must be prevented. However, if the real and reactive power of the load and PV system are closely matched, islanding detection by Passive methods becomes difficult. Also, most active methods lose effectiveness when there are several PV systems feeding the same island. The active frequency drift positive feedback method(AFDPF) enables islanding detection by forcing the frequency of the voltage in the island to drift up or down. In this paper the research for the minimum value of chopping fraction gain applied digital phase-locked-loop (DPLL) to AFDPF considering output power quality and islanding prevention performance are performed by simulation and experiment according to IEEE Std 929-2000 islanding test.

• 한국소음진동공학회논문집
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• 제18권12호
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• pp.1293-1300
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• 2008

This paper presents an active vibration control of cantilever beams under disturbances by a primary force. A direct velocity feedback control using a pair of PZT actuator and a velocity sensor is considered. Variation of the stability and performance with the locations of the sensor/actuator pair is investigated. It is found that the maximum gain varies with the locations of the sensor/actuator pair significantly. The maximum gain shows a symmetric distribution along the beam length with respect to the center point, although the boundary condition of the beam is unsymmetric. The control performance is affected by the location of the primary force as well as the location of the sensor/actuator pair. The active control system can more effectively reduce the vibration when the primary force is located close to the fixed boundary.

• Journal of Power Electronics
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• 제17권4호
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• pp.1058-1070
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• 2017

This paper proposes a novel active damping scheme to suppress LCL-filter resonance with only grid-current feedback control in grid-connected voltage-source converters. The idea comes from the concept of the model reference adaptive control (MRAC). A detailed theoretical derivation is given, and the effectiveness of this method is explained based on its physical nature. According to the control structure of this method, the active damping compensator, which is essentially a second order resonant integrator (SORI) filter, provides an effective solution to damp LCL resonance and to eliminate the need for additional sensors. Compared with extra feedback methods, the cost and complexity are reduced. A straightforward tuning procedure for the active damping method has been presented. A stability analysis is illustrated in the discrete domain while considering a one-step delay. Finally, experimental results are presented to validate the analysis and to demonstrate the good performance of the proposed method.

• 한국전자파학회논문지
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• 제11권3호
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• pp.445-453
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• 2000

본 논문에서는 MMlC 설계에서 필요한 능동 인덕터의 설계 방법을 제시하였다. 제안된 가변 능동 인덕터는 궤환 커패시터와 궤환 저항을 가진 종속접속된 2개의 FET로 구성을 하였다. 제안된 가변 능동 인덕터는 낮은 직렬 저항을 가져서 상대적으로 높은 Q 값을 얻을 수 있고 높은 주파수대에서 사용이 가능한 우수한 동작 특성 을 가진다. 인덕턴스 값은 궤환 커패시터와 궤환 저항 및 바이어스 전압에 의하여 변화되어지며 궤환 저항과 회 로내 병렬 저항을 가변하였을 때 1 GHz에서 15 GHz까지 범위에서 인덕턴스 값이 0.2nH에서 L7nH까지 변화하 였다. 또한 제안된 능동 인덕터를 사용하여 대역통과 필터를 설계하였을 때 삽입손실은 약 0.4 dB이고 반사 손실은 20dB 이상의 우수한 결과를 얻을 수 있었다

• Smart Structures and Systems
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• 제19권5호
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• pp.487-497
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• 2017

Semi-active devices use the building's own motion to produce resistive forces and are thus strictly dissipative and require little power. Devices that independently control the binary open/closed valve state can enable novel device hysteresis loops that were not previously possible. However, some device hysteresis loops cannot be obtained without active analog valve control allowing slower, controlled release of stored energy, and is presents an ongoing limitation in obtaining the full range of possibilities offered by these devices. This in silico study develops a proportional-derivative feedback control law using a validated nonlinear device model to track an ideal diamond-shaped force-displacement response profile using active analog valve control. It is validated by comparison to the ideal shape for both sinusoidal and random seismic input motions. Structural application specific spectral analysis compares the performance for the non-linear, actively controlled case to those obtained with an ideal, linear model to validate that the potential performance will be retained when considering realistic nonlinear behaviour and the designed valve control approach. Results show tracking of the device force-displacement loop to within 3-5% of the desired ideal curve. Valve delay, rather than control law design, is the primary limiting factor, and analysis indicates a ratio of valve delay to structural period must be 1/10 or smaller to ensure adequate tracking, relating valve performance to structural period and overall device performance under control. Overall, the results show that active analog feedback control of energy release in these devices can significantly increase the range of resetable, valve-controlled semi-active device performance and hysteresis loops, in turn increasing their performance envelop and application space.

• 한국자동차공학회논문집
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• 제22권1호
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• pp.20-28
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• 2014

This paper presents static output feedback LQ and $H_{\infty}$ controllers for rollover prevention. Linear quadratic static output feedback controllers have been proposed for rollover prevention in such a way to minimize the lateral acceleration and the roll angle. Rollover prevention capability can be enhanced if $H_{\infty}$ controller is designed. To avoid full-state measurement for feedback requirement or sensitiveness of an observer to nonlinear model error, static output feedback is adopted. To design static output feedback controllers, Kosut's method is adopted because it is simple to calculate. Differential braking and active anti-roll bar are adopted as actuators that generate yaw and roll moments, respectively. The proposed method is shown to be effective in preventing rollover through the simulations on nonlinear multi-body dynamic simulation software, CarSim.

• Smart Structures and Systems
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• 제6권8호
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• pp.921-938
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• 2010

Most of studies on control of beams containing piezoelectric sensors and actuators have been based on linear quadratic regulator (LQR) with state feedback or output feedback law. The aim of this study is to develop velocity-acceleration feedback law in the optimal control of smart piezoelectric beams. A new controller which is an optimal control system with velocity-acceleration feedback is presented. In finite element modeling of the beam, the variation of mechanical displacement through the thickness is modeled by a sinus model that ensures inter-laminar continuity of shear stress at the layer interfaces as well as the boundary conditions on the upper and lower surfaces of the beam. In addition to mechanical degrees of freedom, one electric potential degree of freedom is considered for each piezoelectric element layer. The efficiency of this control strategy is evaluated by applying to an aluminum cantilever beam under different loading conditions. Numerical simulations show that this new control scheme is almost as efficient as an optimal control system with state feedback. However, inclusion of the acceleration in the control algorithm increases practical value of a system due to easier and more accurate measurement of accelerations.

• 한국콘텐츠학회논문지
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• 제21권12호
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• pp.896-905
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• 2021

인공지능 기반 보안관제 시스템은 운영환경에서 발생할 수 있는 학습 데이터 오류, 신규 공격 이벤트 발생으로 인한 오탐 증가 등 문제를 해결하기 위해 피드백 기능이 연구되고 있다. 그러나 한정된 관제 인력의 피드백 수행 방식은 모델 개선에 오랜 시간이 걸리고 숙련되지 않은 관제 인력의 피드백은 오히려 모델 성능 저하의 원인이 될 수 있다. 본 논문에서는 관제 인력 한계 극복, 신규 오탐 개선, 빠른 모델 성능 향상을 위한 능동형 보안관제 모델 개선 프로세스를 제안하였다. 운영 중 예측된 유사 이벤트를 군집화 하고, 피드백이 우선적으로 필요한 군집을 계산하여 운영자에게 대표 이벤트 설명이 가능한 인공지능(eXplainable AI) 기반 시각화도 함께 제시하였다. 수신된 대표 피드백은 동일 군집과 다른 데이터를 계산하여 제외하고 피드백 전파 학습 데이터를 생성한다. 준비된 학습 데이터는 초기 모델과 함께 점진적 학습을 통해 모델을 생성함으로써 성능을 향상시키는 프로세스이다. 제안 프로세스의 실효성 검증을 위해 웹 어플리케이션 방화벽 데이터셋 PKDD2007과 CSIC2012를 선택하여 3개의 시나리오를 통해 실험을 진행하였다. 실험 결과 제안된 프로세스는 피드백을 주지 않았거나 소수 운영자 피드백을 적용한 모델 성능에 비해 모든 지표에서 약 30% 이상의 성능 향상을 확인하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.513-517
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• 1995

In this paper, a relation of matrix Q in cost function to distances between the closed-loop and open-loop poles of a multi input controllable systems is studied. Futhmore, the state feedback gain with exact desired eigenvalues in the LQR is computed. The proposed scheme is applied to designing automotive active suspension control system for a half-car model and its performance is compared with the existing LQR control system design methodology.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2000년도 종합학술발표회 논문집 Vol.10 No.1
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• pp.229-232
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• 2000

In this study, An active band grass filter for 2.14GHz have been designed with MMIC using negative resistance circuit. The negative resistance element was realized with a common-drain FET with series inductive feedback. The designed active filter showed an insertion loss of 0dB at 2.14GHz and a 3-dB bandwidth of 125MHz.