• 한국항행학회논문지
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• 제7권2호
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• pp.128-134
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• 2003

광섬유의 색 분산과 자기 위상 변조 외에 상호 위상 변조 효과에 의해 왜곡된 WDM 채널 신호가 MSSI(Mid-Span Spectral Inversion) 기법을 통해 전송 거리에 따라 보상되는 정도를 다양한 광섬유 분산 계수를 고려하여 분석해 보았다. 본 연구에서 고려된 시스템은 전체 전송로의 중간에 비선형 매질로 HNL-DSF (Highly nonlinear dispersion shifted fiber)를 갖는 광 위상 공액기를 두고, 광 위상 공액기를 중심으로 첫 번째 전송 구간에서의 평균 강도와 두 번째 전송 구간에서의 평균 강도를 같게 하는 PAIA (Path Averaged Intensity Approximation) 방식의 MSSI 기법을 채택한 $3{\times}40$ Gbps 강도 변조 직접 검파 방식의 WDM 시스템이다. XPM에 의한 왜곡의 보상 측면에서 광섬유의 분산 계수가 비교적 큰 WDM 시스템일수록 MSSI 기법이 더욱 효과적으로 적용되어 전송 거리를 신장시킬 수 있는 것을 확인할 수 있었다. 또한 색 분산, SPM 외에 XPM의 영향을 받아 왜곡된 채널 신호는 MSSI 기법을 통해 광섬유의 분산 계수가 큰 시스템에서 더욱 안정되게 보상된다는 것을 알 수 있었다.

• Journal of Power Electronics
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• 제9권5호
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• pp.718-725
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• 2009

To get instantaneous reference data in a single power system with vector space phasors, the instantaneous load current is adopted as a phase and another new signal, which is delayed through filtering by the phase-delay property of a low-pass filter, is used as the secondary phase. Because the two-phases have a different phase, the instantaneous value of the harmonic current can be obtained without a time-delay in calculation. The reference voltage is created by multiplying the coefficient k by the compensation current using the rotating reference frame synchronized with the source-frequency. To verify the validity of the proposed control method, experiments are carried out on a prototype of the single-phase hybrid active power filter system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.149-151
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• 2005

This paper deals with the novel control algorithm of single-phase hybrid active power filter for the compensation of harmonic current components in nonlinear R-L load with passive active power filters. To construct two-axes coordinate, an imaginary second phase was made by giving time delay to line current. In this proposed method, the new signal, which was the delayed through the filtering by the phase-delay property of low-pass filter, is used as the secondary phase. Because two phases have different phase, instantaneous calculation of harmonic current is possible. In this paper, a reference voltage is created by multiplying gain of filter by compensation current using the rotating reference frames that synchronizes with source-frequency, not applying to instantaneous reactive power theory which has been used with the existing fixed reference frames. This paper shows the experimental results, which provide a high accuracy and extremely fast response of single-phase hybrid active Bower filter under the operation with the proposed control method.

• Current Optics and Photonics
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• 제8권1호
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• pp.56-64
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• 2024

In response to the current situation where general methods cannot effectively compensate for the phase delay of ordinary optical mixers, a multi-layer spatial beam-splitting optical mixer is designed using total reflection triangular prisms and polarization beam splittings. The phase delay is generated by the wave plate, and the mixer can use the existing parallel plates in the structure to individually compensate for the phase of the four output beams. A mixer model is established based on the structure, and the influence of the position and orientation of the optical components on the phase delay is analyzed. The feasibility of the phase compensation method is simulated and analyzed. The results show that the mixer can effectively compensate for the four outputs of the optical mixer over a wide range. The mixer has a compact structure, good performance, and significant advantages in phase error control, production, and tuning, making it suitable for free-space coherent optical communication systems.

• Journal of Power Electronics
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• 제8권3호
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• pp.259-267
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• 2008

Power quality improvement in a three-phase four-wire system is achieved using a new topology of DSTATCOM (distribution static compensator) consisting of a star/delta transformer with a tertiary winding and a three-leg VSC (voltage source converter). This new topology of DSTATCOM is proposed for power factor correction or voltage regulation along with harmonic elimination, load balancing and neutral current compensation. A tertiary winding is introduced in each phase for a delta connected secondary in addition to the star-star windings and this delta connected winding is responsible for neutral current compensation. The dynamic performance of the proposed DSTATCOM system is demonstrated using MATLAB with its Simulink and Power System Blockset (PSB) toolboxes under varying loads. The capacitor supported DC bus of the DSTATCOM is regulated to the reference voltage under varying loads.

• Journal of information and communication convergence engineering
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• 제6권3호
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• pp.353-357
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• 2008

One objective in developing the next generation of wireless communication systems is to increase data rates and reliability. A promising way to achieve this is to combine multiple-input and multiple-output signal processing with a space-time coding scheme, which offers higher coding and diversity gains and improves the spectrum efficiency and reliability of a wireless communication system. It is noted, however, that time delay differences and phase differences among different channels increase symbol interference and degrade system performance. In this letter, we investigate phase differences and their effects on multiple-input and multiple-output systems, and propose a compensation algorithm for the Rayleigh fading model to minimize their effects.

• 한국통신학회논문지
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• 제21권8호
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• pp.2055-2062
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• 1996

This paper presents a method of compensating for the gain and phase imbalance of quadrature modulator and demodulator. The gain and phase imbalance are compensated using the received power after the compensation pattern was transmitted at tranceiver. The proposed method is less vulnerable to changes in the transmission channel than the conventional method because compensation is made possible within the tranceiver system, and even the change in phase mblance in accordance with frequency can be compensated utilizing the adaptive algorithm. According to numerical results, a normalized eye opening and a bit error rate are improved by 1.8dB and 3.8dB, respectively.

• 전력전자학회논문지
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• 제18권1호
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• pp.110-116
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• 2013

This paper proposes a current ripple reduction method to improve the control performance of B4 type inverter that is studied for cost-effective drive systems. B4 inverters employ only four switches and they have a center-tapped connection between the split dc-link capacitors and one phase of a three-phase motor or load. In the B4 topology, unbalanced three-phase voltages will be generated due to the dc-link voltage ripple. To solve this problem, this paper presents a voltage distortion compensation method that adjusts the voltage reference with the consideration of dc-link voltage ripple. The validity of the proposed method is verified by simulation and excremental results with an induction machine.

• 한국정밀공학회지
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• 제31권8호
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• pp.705-713
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• 2014

In this paper, we propose a novel velocity ripple controller using phase compensation feedforward control. Velocity ripples result in many kinds of performance degradations in manufacturing machines, especially such as ultra-precision roll lathes. The generation of velocity ripple in constant velocity control comes from various causes, such as electrical torque ripples, mechanical worn out, inconsistent mass center, etc. Conventional researches about ripple is mainly for reducing torque ripple in actuator level, which is only one of reasons for velocity ripples, so in this study, we focus on eliminating velocity ripples in upper level controller using phase compensation feedforward controller. The proposed algorithm is composed of several modules, such as ripple extractor, phase adjuster and phase follower etc. The suggested algorithm can be easily extended, and it shows a superior performance in the experiments of ultra-precision roll lathes.

• Journal of Electrical Engineering and Technology
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• 제10권1호
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• pp.30-40
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• 2015

For a shunt power quality controller (SPQC) the DC side voltage value which is closely related to the compensation performance is a significant parameter. Buy so far, very little discussion has been conducted on this in a quantitative manner by previous publications. In this paper, a method to design the DC side voltage of SPQC is presented according to the compensation performance in the single-phase system and the three-phase system respectively. First, for the reactive current and the harmonic current compensation, a required minimal value of the DC side voltage with a zero total harmonic distortion (THD) of the source current and a unit power factor is obtained for a typical load, through the equivalent circuit analysis and the Fourier Transform analytical expressions. Second, when the DC side voltage of SPQC is lower than the above-obtained minimal value, the quantitative relationship between the DC side voltage and the THD after compensation is also elaborated using the curve diagram. Hardware experimental results verify the design method.