• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전력기술부문
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• pp.214-216
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• 2005

This paper introduces a compression technique for power quality disturbance signal via MRA. The proposed approach is based on a energy at each resolution level. The compression effect can be achieved by thresholding the energies.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 A
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• pp.363-365
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• 2002

The characteristic responds of load respect to various disturbances which can usually be occurred on actual power system is very important to analyze performance and to improve load with high-technology. The disturbance power supply is designed to provide wide range of power to testing load. This device uses PLC technology to dynamic characteristic experiment and CVVF to change frequency. Also this instrument includes data acquisition system to obtain reliable data from experiment.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 제14회 신호처리 합동 학술대회 논문집
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• pp.619-622
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• 2001

In this paper, an efficient approach to classification of transient and harmonic disturbances in power systems is proposed. First, the Stop-and-Go CA CFAR Detector is utilized to detect a disturbance from the power signals which are mixed with other disturbances and noise. Then, (i) Wigner Distribution, SVD(Singular Value Decomposition) and Fisher´s Criterion (ii) DWT and Fisher´s Criterion, are applied to extract an efficient feature vector. For the classification procedure, a combined neural network classifier is proposed to classify each corresponding disturbance class. Finally, the 10 class data simulated by Matlab power system blockset are used to demonstrate the performance of the proposed classification system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
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• pp.671-674
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• 1997

The objective of this paper is to present a new feature-vector extraction method for the automatic detection and classification of power quality(PQ) disturbances, where FIT, DWT(Discrete Wavelet Transform), and Fisher's criterion are utilized to extract an appropriate feature vector. In particular, the proposed classifier consists of three parts: i.e., (i) automatic detection of PQ disturbances, where the wavelet transform and signal power estimation method are utilized to detect each disturbance, (ii) feature vector extraction from the detected disturbance, and (iii) automatic classification, where Multi-Layer Perceptron(MLP) is used to classify each disturbance from the corresponding extracted feature vector. To demonstrate the performance and applicability of the proposed classification algorithm, some test results obtained by analyzing 10-class power quality disturbances are also provided.

• Journal of Power Electronics
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• 제17권5호
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• pp.1211-1222
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• 2017

In order to decrease the parameter sensitivity of deadbeat direct torque control (DB-DTC), an improved deadbeat direct torque control method for surface mounted permanent-magnet synchronous motor (SPMSM) drives is proposed. First, the track errors of the stator flux and torque that are caused by model parameter mismatch are analyzed. Then a sliding mode observer is designed, which is able to predict the d-q axis currents of the next control period for one-step delay compensation, and to simultaneously estimate the model parameter disturbance. The estimated disturbance of this observer is used to estimate the stator resistance offline. Then the estimated resistance is required to update the designed sliding-mode observer, which can be used to estimate the inductance and permanent-magnetic flux linkage online. In addition, the flux and torque estimation of the next control period, which is unaffected by the model parameter disturbance, is achieved by using predictive d-q axis currents and estimated parameters. Hence, a low parameter sensitivity DB-DTC method is developed. Simulation and experimental results show the validity of the proposed direct control method.

• 전력전자학회논문지
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• 제27권5호
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• pp.367-375
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• 2022

Generally, a proportional-resonant controller is used to eliminate steady-state errors during the voltage-current control of a double-conversion uninterruptible power supply (UPS) in a stationary reference frame. Additionally, the feed-forward control compensating for the load current, which can be considered a disturbance of the voltage controller, can be used to improve the disturbance rejection performance. However, during the parallel operation of UPSs, circulating current can occur between UPS modules when performing both feed-forward control and droop control because feed-forward control reduces the circulating current impedance. This study proposes a feed-forward compensation technique that considers the impedance of circulating current. An additional feed-forward compensation technique is developed to enhance the disturbance rejection performance. The validity of the proposed feed-forward compensation technique is verified by the experiment results of the parallel operation of a 500 W double-conversion UPS module.

• 보험의학회지
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• 제2권1호
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• pp.122-127
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• 1985

The basis for determining hearing disturbance adopted by the Life Insurance Industry is the loss of hearing power above 80 db on either or both sides, in accordance with the divide sixth method of audiometric test. Different types of small-to-medium-sized enterprises were chosen for the study of the extent of loss and the power of hearing. The following are the findings: 1. The disturbance percentage found among the types of occupation and different levels of age was found to be higher as the subject's ages increased. 2. The heavier the workload and the noisier the environment, the higher the percentage of disturbance. The average percentage of the subjects turned out to be 24.35%. Those engaged in sawing and wood-work showed 49%. Those engaged in machinery and equipment for transportation accounted for 42.6%. Those engaged in the metal products occupied 39.6%. The disturbance percentage among those engaged in such noisy works as press, pipe and sawing showed 32.52%. 28.46% of those workers with three to four years employment turned out to be disturbed in hearing. Of these, a high percentage of 43.9% showed disturbance in conversation or talk. 3. No hearing loss due to occupation beyond the Life Insurance standard of 80 db was found; therefore, the present status poses no problem. Constant attention, however, is needed.

• 전력전자학회논문지
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• 제26권2호
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• pp.127-134
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• 2021

This study presents an overhang-type rail traction system using dual brushless AC (BLAC) motors with hall sensors. For an accurate position and moving length control of the designed rail traction system, instantaneous position controller using speed reference model and modified disturbance observer for BLAC motor with hall sensor are proposed. The presented speed reference model is designed to satisfy the required performance of 200 mm/s with proper acceleration and deceleration slopes to reduce mechanical vibration. Through the instantaneous speed reference model, instantaneous position and speed errors can be compensated together. Furthermore, the modified disturbance observer for BLAC motors with low-resolution hall sensors can improve the torque and speed control performance. The proposed disturbance observer is based on an actual motor speed. However, the feedback speed information of the hall sensor is not enough for use in the low-speed region. The practical adopted disturbance observer uses an activation speed band to the actual torque controller of the designed rail traction system. The proposed position control scheme is verified by the MATLAB-Simulink model and a practical manufactured traction system. In the computer simulation and experiments, the proposed position control scheme shows advanced control performance.

• 전력전자학회논문지
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• 제15권5호
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• pp.411-416
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• 2010

본 논문에서는 변압기 기반 전압변동 발생기의 직렬변압기에 의한 전압강하 특성을 분석하였다. 전압변동 발생기의 회로구성 방식에는 여러 가지가 있으나 본 논문에서는 비교적 비용이 저렴하고 신뢰도가 높은 직렬변압기를 사용한 방식에 대해 다루고자 한다. 직렬변압기에 의한 전압강하는 변압기의 %Z와 부하용량 및 부하역률에 의해 결정된다. 직렬변압기의 설계가 잘못되면 전압강하가 심각하게 발생하여 제대로 된 성능을 확보할 수 없다. 본 논문에서는 10kVA급 전압변동 발생기에 대해 %Z가 4%인 직렬변압기를 사용한 경우 부하역률에 따른 전압강하를 분석하였으며 지상 부하일수록 전압강하가 증가하고 역률이 0.85 지상인 경우 전압강하가 4% 발생함을 시뮬레이션 및 실험을 통하여 확인하였다.

• 제어로봇시스템학회논문지
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• 제21권7호
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• pp.615-620
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• 2015

DOB (Disturbance Observer) is an useful control method for estimating the disturbance applied to dynamic systems. Disturbance observer can be used to implement a robust control system to generate a control input for rejecting the disturbance, and it can be also used to estimate the disturbance to obtain information. The system that uses disturbance estimation is investigated for high performance control such as automatic door systems, walking robot and electric power steering system in vehicles. In this paper, a novel disturbance observer which is called disturbance and current observer for estimating load torque in the motor system is proposed. The difference between the DOB for disturbance rejection and DCOB is mathematically verified. Current and angular velocity are required for estimating the load torque of the motor in DOB. However, the DCOB can estimate load torque and current without current sensor. DCOB is designed based on modeling of the motor system. Appropriate Q-filter is selected and the applicability of DCOB is verified by simulation. The estimated disturbance and current of the electric motor can be verified without current sensor, as experiments of the actual motor system.