• 한국통신학회논문지
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• 제25권9B호
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• pp.1635-1640
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• 2000

본 논문에서는 기본파를 억제시키고 2차 고조파가 주 발진신호로 동작되는 18GHz 대역의 push-push 발진기를 semi-MMIC 형태로 설계 및 제작하였다. 마이크로스트립 선로를 포함하는 passive component는 semi-insulating GaAs 기판위에 MMIC 공정을 이용하여 구현하고, Chip 형태의 P-HEMT, 저항, 캐패시터를 Au wire-bonding에의해 연결하였으며, via-hole 대신 접지면을 회로 주변에 구성하여, back-side와 wire-bonding하였다. 실험 결과 -10.5 dBm의 출력 전력 특성을 얻었으며, 기본 주파수 억압은 -17.3 dBc/Hz의 특성을 보였다. 위상 잡음은 100kHz offset에서 -97.7 dBc/Hz를 얻었다.

• 전력전자학회논문지
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• 제4권5호
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• pp.462-473
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• 1999

디지털 제어 방식으로 구동되는 모든 교류 전동기 벡터제어시스템의 근간을 이루는 전류 측정에 관한 문제를 다룬다. 일반적인 펄스폭 변조 방식 교류 전동기 구동 시스템에서 전동기 전류에 포함된 인버터 스위칭 노이즈를 없애기 위하여 저역 통과 필터를 사용하는데 이러한 필터는 필연적으로 측정된 신호의 시간 지연을 유발하게 된다. 따라서 샘플링한 전류값에는 기본파 성분 뿐만아니라 고조파 리플 성분이 포함된다. 본 논문에서는 3상 대칭 펄스폭 변조시 기준 전압 벡터의 위치에 다른 전류 샘플링 오차를 해석적으로 구하고 이러한 샘플링 오차를 최소화하기 위한 기법을 제안한다. 제안된 지연 보상 샘플링 기법을 사용하면 정상 상태 전류 측정 오차를 최소화할 수 있고 보다 정확한 토오크 제어가 가능하게 됨을 시뮬레이션과 실험을 통해 보였다.

• 한국자동차공학회논문집
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• 제22권6호
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• pp.23-30
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• 2014

This paper proposes a dead time compensation method for an AC motor drive using phase current polarity information which is detected based on a digital programmable low-pass filter (PLPF). The polarity detection using the PLPF is an alternative solution of a conventional method which uses a general low-pass filter (LPF) and hysteresis bands in order to avoid jittering due to noises. The PLPF not only adjusts its cutoff frequency according to the synchronous frequency of AC motors but also eliminates a gain attenuation and phase delay which are main problems of the general LPF. Through the PLPF, a fundamental component signal without gain and phase distortions is extracted from the measured raw current signal with noise. By use of the fundamental component, the polarity of current is effectively detected by reducing the hysteresis band. Finally, the proposed method compensates the dead time effects by adding or subtracting average voltage value to voltage references of the controller according to the detected current polarity information. The proposed compensation method is experimentally verified by compared with the conventional method.

• Structural Engineering and Mechanics
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• 제72권5호
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• pp.541-555
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• 2019

Wind induced dynamic responses on hyperbolic cooling tower (HCT) shells are complicated functions of structure and wind properties, such as the fundamental frequency f_min, damping ratio ζ, wind velocity V, correlationship in meridian direction and so on, but comprehensions on the sensitivities of the dynamic responses to these four factors are still limited and disagree from each other. Following the dynamic calculation in time domain, features of dynamic effects were elaborated, focusing on the background and resonant components σ_B and σ_R, and their contributions to the total rms value σ_T. The σ_R is always less than σ_B when only the maximum σ_T along latitude is concerned and the contribution of σ_R to σ_T varies with responses and locations, but the σ_R couldn't be neglected for structural design. Then, parameters of the above four factors were artificially adjusted respectively and their influences on the gust responses were illustrated. The relationships of σ_R and the former three factors were expressed by fitted equations which shows certain differences from the existing equations. Moreover, a new strategy for wind tunnel tests aiming at surface pressures and the following dynamic calculations, which demands less experiment equipment, was proposed according to the influence from meridian correlationship.

• 전기학회논문지
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• 제67권11호
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• pp.1447-1454
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• 2018

In this paper, the design of robust DSC-PLL(Delayed Signal Cancellation Phase Locked Loop) is proposed for coping with frequency variation. This method shows significant performance for detection of fundamental positive sequence component voltage when the grid voltage is polluted by grid unbalance and frequency variation. The feedback frequency estimation of DSC-PLL is tracking the drift in the phase by unbalance and frequency variation. The robust DSC PLL is to present the analysis on method and performance under frequency variations. These compensation algorithms can correct for discrepancies of changing the frequency within maximum 193[ms] and improve traditional DSC-PLL. Linear interpolation method is adopted to reduce the discretized errors in the digital implementation of the PLL. For verification of robust characteristic, PLL methods are implemented on FPGA with a discrete fixed point based. The proposed method is validated by both Matlab/Simulink and experimental results based on FPGA(XC7Z030).

• 전력전자학회:학술대회논문집
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• 전력전자학회 2005년도 전력전자학술대회 논문집
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• pp.27-29
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• 2005

This paper studies particularly applicable method for sensorless Permanent Magnet Brushless DC(PMBLDC) Motor drive system. The waveform of the motor internal voltages (or back emf) contains a fundamental and higher order frequency harmonics. Therefore the third harmonics. component is extracted from the stator phase voltage. The resulting third harmonic signal keeps a constant phase relationship with the rotor flux for any motor speed and load condition. In addition, a simple starting method and a speed estimation approach are also proposed.

• 한국전자파학회논문지
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• 제17권8호
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• pp.725-731
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• 2006

Feedforward와 defected ground structure(DGS)를 이용한 새로운 주파수 체배기를 제안하였다. 제한된 주파수 체배기는 feedforward 구조에 의해 기본 주파수$(f_0)$가 제거되고, 아령 또는 나선형 모양의 DGS 구조에 의해 2차, 3차 또는 4차의 원하지 않는 고조파 성분들을 제거할 수 있었다. 결국 feedforward와 DGS 구조에 의해서 체배하고자 하는 성분을 제외한 나머지 고조파들이 제거되었다. 기본 주파수를 1 GHz로 하여 주파수 체배기를 설계하고, 측정하였다. 입력 전력을 0dBm으로 하였을 때 2체배기, 3체배기와 4체배기의 출력 전력은 각각 -2.59 dBm, -5.36 dBm과 -4.57 dBm이었다.

• 전력전자학회논문지
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• 제18권3호
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• pp.225-231
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• 2013

This paper presents an improved signal processing technique in the square-wave-type voltage injection method for IPMSM sensorless drives. Since the sensorless method based on the square-wave voltage injection does not use low-pass filters to get an error signal for estimating rotor position and allows the frequency of the injected voltage signal to be high, the sensorless drive system may achieve an enhanced control bandwidth and reduced acoustic noise. However, this sensorless method still requires low-pass and band-pass filters to extract the fundamental component current and the injected frequency component current from the motor current, respectively. In this paper, these filters are replaced by simple arithmetic operations so that the time delay for estimating the rotor position can be effectively reduced to only one current sampling. Hence, the proposed technique can simplify its whole signal process for the IPMSM sensorless control using the square-wave-type voltage injection. The proposed technique is verified by the experiment on the 800W IPMSM drive system.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 I
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• pp.498-498
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• 2001

Seismic qualification of the Main Control Boards for nuclear power plants has been performed with the guideline of AS ME Section III. US NRC Reg. Guide and IEEE 344 code. The analysis model of the Main Control Boards is consist of beam. shell and mass element by using the finite element method. and, at the same time. the excitation forces and other operating loads for each model are encompassed with respect to different loading conditions. As the fundamental frequencies of the structure are found to be less than 33Hz. which is the upper frequency limit of the seismic load, the response spectrum analysis using ANSYS is performed in order to combine the modal stresses within the frequency limit. In order to confirm the structural and functional integrity of the major components, modal analysis theory is adopted to derive the required response spectrum at the component locations. As all the combined stresses obtained from the above procedures are less than allowable stresses and no mechanical or electrical failures are found from the seismic testing, it concludes the Main Control Boards is dynamically qualified for seismic conditions. Although the authors had confirmed the structural and functional integrity of both Main Control Boards and all the component, in this paper only the seismic analysis of the Main Control Board is introduced.

• Journal of Power Electronics
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• 제17권6호
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• pp.1500-1511
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• 2017

The purpose of this paper is to study a high-performance control scheme for neutral-point-clamping three-level (NPC-3L) inverter fed dual three-phase permanent magnet synchronous motor (PMSM) drives by considering some asymmetric factors such as the non-identical parameters in phase windings. To implement this, the system model is analyzed for dual three-phase PMSM drives with asymmetric factors based on the vector space decomposition (VSD) principle. Based on the equivalent circuits, PI controllers with feedforward compensation are used in the d-q subspace for regulating torque, where the cut-off frequency of the PI controllers are set at the twice the fundamental frequency for compensating both the additional DC component and the second order component caused by asymmetry. Meanwhile, proportional resonant (PR) controllers are proposed in the x-y subspace for suppressing the possible unbalanced currents in the phase windings. A dual three-phase space vector modulation (DT-SVM) is designed for the drive, and the balancing factor is designed based on the numerical fitting surface for balancing the DC link capacitor voltages. Experimental results are given to demonstrate the validity of the theoretical analysis and the proposed control scheme.