• Journal of Power Electronics
• /
• 제14권6호
• /
• pp.1303-1313
• /
• 2014

Dynamic behavior of the harmonic detection part of an active power filter (APF) has an essential role in filter compensation performances during transient conditions. Instantaneous power (p-q) theory is extensively used to design harmonic detectors for active filters. Large overshoot of p-q theory method deteriorates filter response at a large and rapid load change. In this study the harmonic estimation of an APF during transient conditions for balanced three-phase nonlinear loads is conducted. A novel fuzzy instantaneous power (FIP) theory is proposed to improve conventional p-q theory dynamic performances during transient conditions to adapt automatically to any random and rapid nonlinear load change. Adding fuzzy rules in p-q theory improves the decomposition of the alternating current components of active and reactive power signals and develops correct reference during rapid and random current variation. Modifying p-q theory internal high-pass filter performance using fuzzy rules without any drawback is a prospect. In the simulated system using MATLAB/SIMULINK, the shunt active filter is connected to a rapidly time-varying nonlinear load. The harmonic detection parts of the shunt active filter are developed for FIP theory-based and p-q theory-based algorithms. The harmonic detector hardware is also developed using the TMS320F28335 digital signal processor and connected to a laboratory nonlinear load. The software is developed for FIP theory-based and p-q theory-based algorithms. The simulation and experimental tests results verify the ability of the new technique in harmonic detection of rapid changing nonlinear loads.

• 천문학논총
• /
• 제8권1호
• /
• pp.179-183
• /
• 1993

We analyze the evolution of active galactic nuclei for the decreasing accretion rate case. Our analysis is based on the unified theory of active galactic nuclei which entirely depends on the accretion rates of the central supermassive black holes. Our discussion leads us to conclude that active galactic nuclei may evolve from QSOs into the nuclei of Seyfert or radio galaxies.

• 전력전자학회논문지
• /
• 제4권1호
• /
• pp.50-56
• /
• 1999

본 연구에서는 시간영역에서 전력이 해석되어지므로 이해하기 쉽고, 비교적 계측하기 용이한 상관함수에 의한 순시전력이론에 대해서 고찰하였다. 상관함수에 의한 순시전력이론은 시간영역에서 전압과 전류의 자기상관함수와 상호상관함수에 의해서 전력과의 전압과 상관성에 따라 상관전력과 비상관 전력으로 분해된다. 분해된 두 가지 전력성분으로부터 비선형 부항의 특성에 따라 전력과 전류를 유효성분, 기본파 무효성분 그리고 고조파성분 등 3성분으로 분해한다. 능동전력필터는 그 보상특성상 전력과 전류의 3성분만을 다루며, 실시간 제어를 위해 그외의 여러 복잡한 그리고 구현의 어려움이 있는 전력모델은 경제적이지 못하다. 상관함수적인 순시전력이론에 의해 분석된 전력성분들의 타당성을 입증하기 위해서 전압형 DSP능동전력필터를 제작하였다. 싸이리스터 제어 유도전동기 구동시스템의 전력을 제안된 순시전력이론에 의해 3성분으로 분해한 후, 이들 성분중에서 보상기준전류로 고조파성분과 기본파 무효성분을 각각 제어하여 그 보상결과로부터 타당성을 입증하였다.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 1999년도 전력전자학술대회 논문집
• /
• pp.667-670
• /
• 1999

An active power filter is used to eliminate harmonic currents. This paper applied the extension pq theory to harmonic currents compensation. An active power filter based on extension pq theory is more effective than pq theory in 3-phase unsymmetrical voltage system. When extension pq theory is used, the result of simulation present source current is not distorted. Pulse-width modulation method is CRPWM(Current-Regulated PWM).

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2000년도 전력전자학술대회 논문집
• /
• pp.111-114
• /
• 2000

Harmonics and fundamental reactive power of nonlinear loads in serious unbalanced power condition are compensated by current synchronous detection(CSD) theory which is also acceptable for single phase power system, but the CSD theory is not suitable any more in case of controlled independently harmonics and reactive component. Therefore a new algorithm the extended current synchronous detection (ECSD)theory for a three phase active power filter based on decomposition of fundamental reactive distorted components is proposed in this paper. The proposed ECSD theory is simulated and tested comparison with a few power theories under asymmtrical condition in power system.

• Steel and Composite Structures
• /
• 제32권6호
• /
• pp.753-767
• /
• 2019

Vibration control in mechanical equipments is an important problem where unwanted vibrations are vanish or at least diminished. In this paper, free vibration active control of the porous sandwich piezoelectric polymeric nanocomposite microbeam with microsensor and microactuater layers are investigated. The aim of this research is to reduce amplitude of vibration in micro beam based on linear quadratic regulator (LQR). Modified couple stress theory (MCST) according to sinusoidal shear deformation theory is presented. The porous sandwich microbeam is rested on elastic foundation. The core and face sheet are made of porous and three-phase carbon nanotubes/resin/fiber nanocomposite materials. The equations of motion are extracted by Hamilton's principle and then Navier's type solution are employed for solving them. The governing equations of motion are written in space state form and linear quadratic regulator (LQR) is used for active control approach. The various parameters are conducted to investigate on the frequency response function (FRF) of the sandwich microbeam for vibration active control. The results indicate that the higher length scale to the thickness, the face sheet thickness to total thickness and the considering microsensor and microactutor significantly affect LQR and uncontrolled FRF. Also, the porosity coefficient increasing, Skempton coefficient and Winkler spring constant shift the frequency response to higher frequencies. The obtained results can be useful for micro-electro-mechanical (MEMS) and nano-electro-mechanical (NEMS) systems.

• Smart Structures and Systems
• /
• 제19권4호
• /
• pp.351-360
• /
• 2017

Protection of structures against natural hazards such as earthquakes has always been a major concern. Semi-active control combines the reliability of passive control and versatility and adaptability of active control. So it has recently become a preferred control method. This paper proposes an algorithm based on Uniform Deformation Theory to mitigate vulnerable buildings using magneto-rheological (MR) damper. Due to the successful performance of fuzzy logic in control of systems and its simplicity and intrinsically robustness, it is used here to regulate MR dampers. The particle swarm optimization (PSO) algorithm is also used as an adaptive method to develop a fuzzy control algorithm that is able to create uniform inter-story drifts. Results show that the proposed algorithm exhibited a desirable performance in reducing both linear and nonlinear seismic responses of structures. Performance of the presented method is indicated in compare with passive-on and passive-off control algorithms.

• 한국콘텐츠학회:학술대회논문집
• /
• 한국콘텐츠학회 2008년도 춘계 종합학술대회 논문집
• /
• pp.800-804
• /
• 2008

본 연구는 능동적 수용자로서 프로슈머가 미디어를 접할 때, 무조건적으로 수용하는 것이 아니라 능동적인 개인으로서의 수용자라는 문제 인식에서 출발하였다. 다양한 소수의견이 교환되고 문화의 저변이 확대 양산되는 등 사회 전반의 다양성을 증대시키고 기업 환경까지 빠르게 변화시키고 있는 UCC의 논의에 있어 프로슈머의 능동적 역할을 위한 전략적 제언을 하고자 한다. 그럼으로써 UCC 이용에 있어 능동적인 수용자의 모습을 확인하고 그 의미를 찾기 위한 연구라 하겠다.

• 한국지반공학회지:지반
• /
• 제12권6호
• /
• pp.101-114
• /
• 1996

Coulomb토압이론은 실무에서 주로 사용되고 있음에도 불구하고 점성토로 뒤채움된 옹벽에 대한 일반적인 조건에 적용할 수 있는 토압이론식이 존재하지 않는다. 여기서는 점성토로 뒤채움한 중력식 옹벽에 대해서 배수 및 비배수 해석으로 인장균열이 부시된 경우와 고려된 경우에 각각 토압이론식을 유도하였다. 그리고 상기의 조건들에 대해서 전주동토압과 인장균열 깊이를 구하여 설계도표를 작성하였다.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
• /
• pp.571-575
• /
• 2001

A protection scheme for hybrid active power filters, which is combined shunt passive filter and small rated series active filter, is presented and analyzed in this paper. The proposed series active power filter operated as a high impedance 'k($\Omega$)' to the fundamental component when over current occurs in the power distribution system, and three control strategies are proposed in this paper. The first is the method by detecting the fundamental source current through the p-q theory, the second is the method by detecting the fundamental component of load current in Synchronous Reference Frame (SRF) and the third is the method by detecting the input voltage. When the over current occurs in the power distribution system, the proposed scheme protects the series active power filter without additional protection circuits. The validity of proposed protection scheme is investigated through experimental result for the prototype hybrid active power filter system.