• 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.

• 한국통신학회논문지
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• 제35권12C호
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• pp.1029-1034
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• 2010

QPSK 디지털 수신기는 전송 경로 또는 송수신기 간의 클럭 차이에 의해 발생하는 위상 편차를 보정하기 위해 위상 복원 방안이 필요하다. 널리 사용되고 있는 디지털 Costas 위상 복원 루프는 입력신호의 주파수/위상 복원 성능이 입력 신호의 전력에 따라 달라지므로 별도의 자동 이득조정 (AGC) 루프가 필요하고, 이는 하드웨어 구현시 시스템의 복잡도와 사용 자원을 증가시킨다. 본 논문에서는 입력 전력에 관계없이 일정한 위상 보정 기능을 수행할 수 있으며 타이밍 복원을 위한 AGC를 동시에 제공할 수 있는 위상 보정 및 진폭 보상 방안을 제안하였다. 제안된 방안은 CORDIC 알고리즘을 사용하여 입력 신호의 위상 및 진폭 정보를 분리하여 각각 처리하며 시스템의 복장도 및 사용 자원을 대폭 절감할 수 있으며, C++ 및 Model Sim을 사용한 모의실험을 통해 본 논문에서 제안한 위상 복원 루프의 동작을 검증하였다.

• 한국정밀공학회지
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• 제34권4호
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• pp.265-272
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• 2017

Velocity ripple in manufacturing processes reduces productivity and limits the precision of the product. In practice, the frequency and phase of velocity ripples always change minutely, which makes it impossible to compensate for the ripple by simply inserting an opposite feed-forward signal in the system. In this study, an active-phase compensation algorithm was developed to enable the velocity-ripple controller to track the phase change of the ripples in real time. The proposed controller can compensate for the velocity ripple whatever its cause, including disturbance by the torque ripple. The algorithm consists of three functional modules: the velocity-ripple extractor, the synchronized integrator, and the phase shifter. Experimental results showed that the proposed controller clearly reduces velocity ripples with phase variation.

• 산업기술연구
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• 제11권
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• pp.65-72
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• 1991

In this paper, a control algorithm is discussed when the quadruped walking robot walks over the unknown soft ground. Firstly, it estimated the relationship between the foot force and the ground sinkage at the leg-placing phase. Secondly, the generated soil property is applied to the leg-supporting phase. If the attitude angle is changed by incorrect ground sinkage compensation, the control algorithm adjusts the attitude angle using simplified orientation orientation matrix.

• 전력전자학회논문지
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• 제18권2호
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• pp.161-168
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• 2013

This paper presents an algorithm of a compensation of the grid current distortion caused by the grid voltage unbalance and distortion in 3-phase bi-directional DC to AC inverter. Usually 3-phase grid system has unbalance and distortion because of connecting 1-phase and non-linear load with 3-phase load using same input node. Controlling 3-phase inverter by general method under the unbalanced and distorted grid voltage, the grid current has distortion. This distortion of the grid current cause the grid voltage distortion again. So, it need to control the grid current balanced and non-distorted, even the grid voltage gets unbalanced and distorted. There are some complex method to compensate the gird current distortion. it suggest simple method to solve the problem. Simulation and experiment is used to validate the proposed algorithm.

• 한국인터넷방송통신학회논문지
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• 제12권2호
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• pp.153-158
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• 2012

본 논문에서는 통신 채널에서 발생되는 찌그러짐과 잡음의 영향을 최소화하기 위하여 사용되는 적응 등화 알고리즘인 CMA 와 MMA 의 성능을 비교하였다. 다른 방식에비해 비교적 간단한 연산으로 고속 등화가 가능한 알고리즘인 CMA (Constant Modulus Algorithm)와 이의 오차 함수를 변형한 MMA (Multi-Modulus Algorithm)의 성능을 분석하여 점대점 또는 점대다점의 디지털 전송에서 적용 가능성을 확인하였다. CMA 알고리즘은 수신 신호의 진폭만을 보상하며 위상은 보상하지 못하므로 별도의 PLL을 사용하여야 하지만, MMA 알고리즘은 진폭과 위상을 동시에 보상할 수 있음을 컴퓨터 시뮬레이션을 통하여 확인하였으며 이의 성능 비교를 위해서 적응 등화기에 필수적인 수렴 특성과 잔류 isi양을 사용하였고, 그 결과 수렴 특성에서는 MMA 방식이, 진폭 보상을 나타내는 잔류 isi 양에서는 CMA 방식이 우월함을 알 수 있었다.

• 전기학회논문지P
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• 제58권4호
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• pp.391-396
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• 2009

In this paper, a control algorithm for DC-Link voltage unbalancing compensation of a four-switch inverter for a three-phase BLDC motor drive is proposed. Compared with a conventional six-switch inverter, the split source of the four-switch inverter can be obtained by splitting DC-link capacitor into two capacitors to drive the three phase BLDC motor. The voltages across each of two capacitors are not always equal in steady state because of the unbalance in the impedance of the DC-link capacitors $C_1$ and $C_2$ or the variable current flowed into the capacitor's neutral point in motor control. Despite the unbalance, if the BLDC motor may be run for a long time the voltage across one of the capacitors is more increased. So the unbalance in the capacitors voltages will be accelerated. As a result, The current ripple and torque ripple is increased due to the fluctuation of input current which flows into 3-phase BLDC motor. According to that, the vibration of motor will be increased and the whole system will be instable. This paper presents a control algorithm for DC-Link voltage unbalancing compensation. The sampling from the voltages across each of two capacitors is used to perform the voltage control of DC-Link by using the feedforward controller.

• Journal of Power Electronics
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• 제16권1호
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• pp.18-26
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• 2016

This paper proposes a compensation algorithm for reducing a specific ripple component on synchronous reference frame phase locked loop (SRF-PLL) in grid-tied single-phase inverters. In general, SRF-PLL, which is based on all-pass filter to generate virtual voltage, is widely used to estimate the grid phase angle in a single-phase system. In reality, the estimated grid phase angle might be distorted because the phase difference between actual and virtual voltages is not 90 degrees. That is, the phase error is caused by the difference between cut-off frequency of all-pass filter and grid frequency under grid frequency variation. Therefore, the effects on phase angle and output current attributed to the phase error are mathematically analyzed in this paper. In addition, the proportional resonant (PR) controller is adapted to reduce the effects of phase error. The validity of the proposed algorithm is verified through several simulations and experiments.

• Journal of Electrical Engineering and Technology
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• 제12권2호
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• pp.533-540
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• 2017

Distance relay identifies the type and location of fault by measuring the transmission line impedance. However any other factors that cause miss calculating the measured impedance, makes the relay detect the fault in incorrect location or do not detect the fault at all. One of the important factors which directly changes the measured impedance by the relay is series capacitive compensation (SCC). Another factor that changes the calculated impedance by distance relay is fault resistance. This paper provides a method based on the combination of distance and differential protection. At first, faulty transmission line is detected according to the current data of buses. After that the fault location is calculated using the proposed algorithm on the transmission line. This algorithm is based on active power calculation of the buses. Fault resistance is calculated from the active powers and its effect will be deducted from calculated impedance by the algorithm. This method measures the voltage across SCC by phasor measurement units (PMUs) and transmits them to the relay location via communication channels. The transmitted signals are utilized to modify the voltage signal which is measured by the relay. Different operating modes of SCC and as well as different faults such as phase-to-phase and phase-to-ground faults are examined by simulations.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권11호
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• pp.563-571
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• 2003

In this paper, the control algorithm and control method for a combined system of shunt passive filter and series active filter in 3-phase 4-wire system are discussed. Moreover, the three-phase four-wire system is widely employed in distributing electric energy to several office building and manufacturing plants. In such systems, the third harmonic and its 3th harmonics are termed as triple and zero sequence components that do not cancel each other in the system neutral. Consequently, the triple harmonics add together creating a primary source of excessive neutral current. Regarding this concern, this paper presents a new control algorithm for a series hybrid active system, whereas the control approach it adopts may directly influence its compensation characteristics. Hence, the advantage of this control algorithm is direct extraction of compensation voltage reference and the required rating of the series active filter is much smaller than that of a conventional shunt active filter. Some experiments were executed and experimental results from a prototype active power filter confirm the suitability of the proposed approach.