• Journal of Power Electronics
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• 제14권2호
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• pp.392-401
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• 2014

A fast-transient repetitive control strategy for a three-phase shunt active power filter is presented in this study to improve dynamic performance without sacrificing steady-state accuracy. The proposed approach requires one-sixth of the fundamental period required by conventional repetitive control methods as the repetitive control time delay in the synchronous reference frames. Therefore, the proposed method allows the system to achieve a fast dynamic response, and the program occupies minimal storage space. A proportional-integral regulator is also added to the current control loop to eliminate arbitrary-order harmonics and ensure system stability under severe harmonic distortion conditions. The design process of the corrector in the fast-transient repetitive controller is also presented in detail. The LCL filter resonance problem is avoided by the appropriately designed corrector, which increases the margin of system stability and maintains the original compensation current tracking accuracy. Finally, experimental results are presented to verify the feasibility of the proposed strategy.

• 대한전자공학회논문지SD
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• 제45권5호
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• pp.65-70
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• 2008

본 논문에서는 루프 대역폭을 조절하여 빠른 위상 고정 시간을 갖는 새로운 구조의 이중 루프 위상고정루프를 제안하였다. 위상고정루프가 out-lock 상태일 때는 채널 간격의 1/10보다 더 큰 대역폭을 갖도록 하였으며, in-lock 부근에서는 채널 간격의 1/10 보다 더 작은 좁은 대역폭을 갖도록 하였다. 제안된 위상고정루프는 표준 CMOS $0.35{\mu}m$ 공정으로 HSPICE를 이용하여 설계 하였다. 시뮬레이션 결과 PLL의 대역폭을 200KHz 채널 간격 보다 14배 크게 하여 80MHz의 주파수를 변화시키는데 $50{\mu}s$의 빠른 위상고정 시간을 갖는 것으로 나타났다.

• Journal of electromagnetic engineering and science
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• 제1권1호
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• pp.18-23
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• 2001

A fast-sweep broadband FM reflectometer system has been successfully developed and operacted at the DIII-D tokamak, producing reliable density Profiles with excellent spatial (1 $\leq$ cm) and temporal resolution (~100 $\mu$ s). The system uses a solid-state microwave oscillator and an active quadrupler, covering full Q-band frequencies (33~50 GHz) and providing relatively high output power (20~60 mW). The system hardware allows fu11band frequency sweep in 10 $\mu$ s, but due to digitization rate limit on DIII-D, sweep time was limited to 75~100 $\mu$ s. Fast frequency sweep has helped to reduce density fluctuation effects on the reflectometer phase measurements, thus improving reliability for individual sweeps. The fast-sweep system with high spatial and temporal resolution has allowed to measure fast-changing edge density profiles during plasma ELMS and L-H transitions, thus enabling fast-time sca1e physics studies.

• 전기학회논문지
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• 제60권7호
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• pp.1331-1338
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• 2011

This paper proposes a method for frequency control of islanded microgrid with battery energy storage system. For frequency control of islanded microgrid, battery energy storage system uses a phase locked loop algorithm with positive sequence components for a fast frequency estimation. Microgrid is a power system with small inertia because it has small capacity generators and inverter systems for renewable energy. So, Islanded microgrid's frequency varies fast and large as small generation and load changes. To reduce frequency variation of islanded microgrid, it needs a device with fast frequency response. For fast frequency response, a fast frequency tracking is important. To show the validation of proposed fast frequency tracking algorithm, battery energy storage system with proposed algorithm is tested in microgrid pilot plant.

• 한국인터넷방송통신학회논문지
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• 제18권1호
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• pp.97-103
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• 2018

위성 변조 비콘 신호는 위성에서 생성한 TOD (Time of Day) 데이터를 gold sequence를 이용하여 확산 시킨 후 linear phase modulation을 통해 전송된다. 변조 비콘 신호를 수신 시 위성과 지상 수신기 간 특성 차이 때문에 주파수 오프셋(FO)이 발생한다. 기존 위성 변조 비콘 수신기는 변조 비콘 신호를 FFT(Fast Fourier Transform)를 이용하여 주파수를 동기화시키는 방법이며, 이는 시스템 구현 관점에서 딜레이 및 복잡도를 증가 시킬 뿐만 아니라 points 간 생기는 FO과 phase offset에 의한 위상차를 보정하는 별도의 회로가 필요하다. 본 논문에서는 이를 극복하기 위해 변조 비콘 신호의 2위상 성형된 특성을 이용하여 coarse FO와 phase offset을 한 번에 보정 및 복조하기 위한 방안과 그에 따른 하드웨어 구성도를 제안 및 분석하였다. 또한, 시뮬레이션을 통해 본 논문에서 제안하는 방식에 적합한 변조 지수(modulation index)를 분석하였으며 그에 따른 적정 누적 개수 또한 분석하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2011년도 전력전자학술대회
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• pp.442-443
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• 2011

In this paper, a voltage control method based on DQ transformation and Space Vector Pulse Width Modulation (SVPWM) for a single phase three-level converter is proposed. This control method is designed to use DC values instead of using instantaneous values of current which are usually used in single-phase application, so that it results in a fast and robust voltage control response. Simulation results demonstrate the validity of the control strategies.

• ETRI Journal
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• 제28권4호
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• pp.435-443
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• 2006

This paper presents an efficient carrier recovery algorithm combined with a turbo-coding technique in a mobile communication system. By using a block turbo code made up of independently decodable block codes, we can efficiently recover the fast time-varying carrier phase as well as correct channel errors. Our simulation results reveal that the proposed scheme can accommodate mobiles with high speed, and at the same time can reduce the number of iterations to lock the phase.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(2)
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• pp.281-284
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• 2001

This paper describes an analog multi-phase delay-locked loop (DLL) to solve the harmonic lock problem using current-starved inverter and shunt-capacitor delay cell. The DLL can be used not only as an internal clock buffer of microprocessors and memory It's but also as a multi-phase clock generator for gigabit serial interfaces. The proposed circuit was simulated in a 0.25${\mu}{\textrm}{m}$ CMOS technology to solve harmonic lock problem and to realize fast lock-on time and low-jitter we verified time interval less than 40 ps as the simulation results.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 추계종합학술대회 논문집
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• pp.275-278
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• 1999

In this paper, Dual PFD(Phase Frequency Detector) with improved phase locking time is proposed. The proposed PFD consists of positive and negative edge triggered D flip-flop. In order to confirm the characteristics of proposed PFD, HSPICE simulations are performed using a 0.25${\mu}{\textrm}{m}$ CMOS process. As a result of simulations, the proposed PFD has a characteristic of fast phase locking time with dead zone free.

• 동의생리병리학회지
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• 제19권3호
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• pp.760-764
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• 2005

This research was performed to investigate protective effect of Sophora Subprostrata fractions against focal ischemic brain damage after middle cerebral artery(MCA) occlusion. Rats were divided into six groups: MCA-occluded group(Control); each administered groups with Sophora Subprostrata total phase(Total), Sophora Subprostrata Aqueous phase (Aqueous), Sophora Subprostrata BuOH phase(BuOH), and Sophora Subprostrata Alkaloid phase(Alkaloid) after MCA-occlusion; sham-operated group(Sham). The right MCA was occluded by A poly-L-lysine coated 4-0 nylon suture thread through the internal carotid artery permanently. Sophora Subprostrata and fractions were administered orally(5mg/ml) for 7 days after MCA-occlusion. The behavior of ischemic rats were examined at 24 hours, 3, 5 and 7 days after MCA-occlusion from the views of 4 different aspects: posture & balance tests(4 subtests), reflex tests(6 subtests), muscle-tone tests(3 subtests), and foot-fault test. The results showed that 1) in muscle tone test, Sophora Subprostrata total phase only increased reduced muscle tone function from 3 to 7 days, 2) in reflex test, Sophora Subprostrata total and Aqueous phase increased fast recovery from 24 hours and 3 days, 3) in posture & balance test, Sophora Subprostrata total and Aqueous phase increased fast recovery from 24 hours, and Sophora Subprostrata BuOH and Alkaloid phase increased posture & balance function from 3 days, but 4) in motor function test, Sophora Subprostrata did not show effective recovery compared with control group. In conclusion, Sophora Subprostrata has protective effects against brain damage at the early stage of focal cerebral ischemia. Sophora Subprostrata total and Aqueous phase produced more pronounced protective effect against focal ischemic brain damage.