• 전기학회논문지
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• 제62권5호
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• pp.626-631
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• 2013

Gas turbine systems are applied extensively in energy supplies to cover peak load requirements. The gas turboset must be accelerated by starting device up to 60%~80% of rated speed to ignite the gas turbine. Recently, the most favorable and economical starting device is the LCI(Load Commutated Inverter). The LCI runs up the gas turboset by feeding the generator as a synchronous motor. In this paper, we discuss in detail the driving principles and features of 183MW gas turbine system. During field application of LCI system, many tests have been conducted and the results were described in this paper. The test results will be considered as the important resources for development in future.

• 한국정보전자통신기술학회논문지
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• 제9권2호
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• pp.178-184
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• 2016

본 논문에서는 전력에너지를 사용하는 산업체의 전동기용량이 점차 증가하고 있다. 전동기는 기동시 기동전류로 전압강하가 발생한다. 이 기동전류가 전력계통에서 대형 전동기 기동 시 전압강하로 기동이 어려워 인접한 전력계통에 나쁜 영향을 미치게 된다. 또한 전동기는 부하의 크기에 따라 토크를 내는 것으로 토크의 크기에 따라 속도가 변하고 속도는 전동기 기동에 중요하다. 일반적으로 변압기나 비상발전기로부터 전동기까지의 거리가 짧으며 전동기용량이 작아 기동에 대한 어려움이 없으나 산업설비 등에 많이 이용되는 대용량 전동기의 기동특성에 대한 이론과 실제의 운전특성을 측정 분석하였다. 따라서 이번 연구는 전동기 기동 시 속도와 토크에 관계와 대용량 전동기 기동을 위한 분석과 전동기 기동 해석에 대해 연구하였다.

• 플랜트 저널
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• 제12권4호
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• pp.37-43
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• 2016

원자력발전소의 사고 대처 부하에 전력을 공급하는 전원계통은 다양한 조건에서도 일정 전압이 유지됨을 분석을 통하여 입증한다. 이를 위하여 발전소를 일정부하 운전 상태로 유지하고, 대용량 전동기(원자로냉각재펌프(RCP), 기기냉각수펌프(CCWP))를 각각 기동하여 기동 전 후 안전관련 모선의 전압을 측정하였다. 현장 시험으로 확보된 자료(예, 전압, 전류, 역율 등)는 기존 전력계통해석 모델의 운전 조건으로 재입력하고 재분석을 수행하였다. 이는, 기존 전력계통분석에 사용된 분석기법과 가정들을 실질적인 측정과 결과 분석으로 입증하는 과정이다. 결국, 두 경우의 전압 강하는 발전소 안전에 중요한 기기의 전압이 허용전압 이하로 저하되지 않음과 두 값의 비교 결과가 요구되는 제한치 이내임을 검증한다.

• 산업기술연구
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• 제19권
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• pp.217-226
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• 1999

A single phase to three phase power converter with cost effective and simple structure is proposed. The converter consists of rectifier and inverter. The rectifier is composed of a half wave rectifier, a dc link capacitor, and a current limiting inductor, and the inverter is of only two switches with PWM control. For negative sequence operation the inverter output voltage leads the line input by $60^{\circ}$, and for positive sequence operation the inverter output voltage leads by $60^{\circ}$. We can see that positive sequence operation shows higher output voltage, slight harmonic distortion(2%), and better performances such as high efficiency and high power factor. A mathematical model for system analysis is provided, and specifications for selection and control scheme both for start-up and for steady state are analyzed. comparison and operational limits of positive and negative sequence operation are performed, and simulations and experiments are executed to verify the proposed.

• International Journal of Computer Science & Network Security
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• 제22권4호
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• pp.1-12
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• 2022

In order to overcome the power fluctuation issues in photovoltaic (PV) smart grid-connected systems and the inverter nonlinearity model problem, an adaptive backstepping command-filter and a double second order generalized Integrators (DSOGI) controller are designed in order to tune the AC current and the DC-link voltage from the DC side. Firstly, we propose to present the filter mathematical model throughout the PV system, at that juncture the backstepping control law is applied in order to control it, Moreover the command filter is bounded to the controller aiming to exclude the backstepping controller differential increase. Additionally, The adaptive law uses Lyapunov stability criterion. Its task is to estimate the uncertain parameters in the smart grid-connected inverter. A DSOGI is added to stabilize the grid currents and eliminate undesirable harmonics meanwhile feeding maximum power generated from PV to the point of common coupling (PCC). Then, guaranteeing a dynamic effective response even under very unbalanced loads and/or intermittent climate changes. Finally, the simulation results will be established using MATLAB/SIMULINK proving that the presented approach can control surely the smart grid-connected system.

• 전력전자학회논문지
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• 제18권3호
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• pp.232-239
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• 2013

This paper proposes an improved stator flux estimator through ensuring conventional PLPF to act as a pure integrator for sensorless control of induction motors. Conventional PLPF uses the estimated synchronous speed as a cut-off frequency and has the gain and phase compensators. The gain and phase compensators are determined on the assumption that the estimated synchronous angular speed is coincident with the real speed. Therefore, if the synchronous angular speed is not same as the real speed, the gain and phase compensation will not be appropriate. To overcome the problem of conventional PLPF, this paper analyzes the relationship between the synchronous speed error and the phase lag error of the stator flux. Based on the analysis, this paper proposes the synchronous speed error compensation scheme. To achieve a start-up without speed sensor, the current model is used as the stator flux estimator at the standstill. When the motor starts up, the current model should be switched into the voltage model. So a stable transition between the voltage model and the current model is required. This paper proposes the simple transition method which determines the initial values of the voltage model and the current model at the transition moment. The validity of the proposed schemes is proved through the simulation results and the experimental results.

• Journal of Chest Surgery
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• 제28권6호
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• pp.542-548
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• 1995

The goal of this study is to develop an effective control system for cardiac output regulation based upon the preload and afterload conditions without any transducers and compliance chambers in the moving actuator type total artificial heart. Motor current waveforms during the actuator movement are used as an input to the automatic control algorithm. While the current waveform analysis is performed, the stroke length and velocity of the actuator are gradually increased up to the maximum pump output level. If the diastolic filling rate of either right or left pump begins to exceed the venous return, atrial collapse will occur. Since the diastolic suction acts as a load to the motor, this critical condition can be detected by analyzing the motor current waveforms. Every time this detection criterion is met, the control algorithm decreases the stroke velocity and length of the actuator step by step just below the critical detection level. Then, they start to increase. In this way the maximum pump output under given venous return can be achieved. Additionally the control algorithm provides some degree of afterload sensitivity. If the aortic pressure is detected to exceed 120 mmHg, the stroke length and velocity decrease in the same way as the response to the preload. Left-right pump output balance is maintained by proper adjustment of the asymmetry of the stroke angle. In the mock circulatory test, this control system worked well and there was a considerable range of stroke volume difference with adjustment of the asymmetry value. Two ovine experiments were performed. It was confirmed that the required cardiac output regulation according to the venous return could be achieved with adequate detection of diastolic function, at least in the in vivo short-term survival cases[2-3 days . We conclude that this control algorithm is a promising method to regulate cardiac output in the moving actuator type total artificial heart.