• 조명전기설비학회논문지
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• 제12권4호
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• pp.81-89
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• 1998

본 논문에서는 유도전동기의 가변속 구동시 제어성능이 우수한 직접빽터 제어시스템에 관하여 연구하였다. 벡터제어시 펼요한 전동기의 자속정보는 궤환제어의 장점이 있는 자속연산형을 사용하여 구하였으며, 이때의 모델은 회전자 회로의 전류모델 방식을 이용하였다. 또한 회전자 좌표계에서의 자속관측기를 구성하여 고정 자 좌표계 사용시 나타날 수 있는 d-q축 간섭현상 및 이산화의 오차를 경감시켰다. 디지털 시율레이션올 통하여 원활한 제어특성이 나타남을 입증하였으며 고성능 DSP소자 및 고속 IGBT를 채용한 인버터 드라이브 시스템을 구현하여 그 특성을 확인하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.598-601
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• 2003

Most of all, DTC drive is very simple in its implementation because it needs only two hysteresis comparator and switching vector table for both flux and torque control. The switching strategy of a conventional direct torque control scheme which is based on hysteresis comparator results in a variable switching frequency which depends on the speed, flux, stator voltage and the hysteresis of the comparator. The amplitude of hysteresis band greatly influences on the drive performance such as flux and torque ripple and inverter switching frequency. In this paper the influence of the amplitudes of flux and torque hysteresis bands and sampling time of control program on the torque and flux ripples are investigated. Simulation results confirm the superiority of the DTC under the proposed method over the conventional DTC.

• 전력전자학회논문지
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• 제26권4호
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• pp.256-262
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• 2021

Six-phase motors can be used in industrial applications, such as an electric vehicle, due to their high reliability and low current magnitude per phase. An asymmetrical PMSM with two sets of three-phase windings is a commonly used structure for six-phase motors, with each winding set demonstrating a phase difference of 30°. Although the asymmetrical PMSM presents low torque ripples, its dynamic torque response deteriorates due to coupled components in the two three-phase windings. The decoupled VSD control is applied to eliminate the coupling effect. Load ratio control of two inverters for the six-phase PMSM is proposed in this study. DQ currents are controlled on the basis of two synchronous reference frames, and the six-phase drive system can be changed to a three-phase drive system when one inverter presents fault conditions. The operation and effectiveness of the proposed algorithm is verified through simulation and experiments. The six-phase drive system is transferred to a three-phase drive system by changing the current reference of the second DQ reference frame. Moreover, control of both torque and speed exhibits satisfactory performance before and after the mode change.

• Journal of Biosystems Engineering
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• 제25권3호
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• pp.213-220
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• 2000

Grafting of fruit-bearing vegetables has been widely used to increase the resistance to soil-borne diseases, to increase the tolerance to low temperature or to soil salinity, to increase the plant vigor, and to extend the duration of economic harvest time. After grafting, it is important to control the environment around grafted seedlings for the robust joining of a scion and rootstock. Usually the shading materials and plastic films are used to keep the high relative humidity and low light intensity in greenhouse or tunnel. It is quite difficult to optimally control the environment for healing and acclimation of grafted seedlings under natural light. So the farmers or growers rely on their experience for the production of grafted seedling with high quality. If artificial light is used as a lighting source for graft-taking of grafted seedlings, the light intensity and photoperiod can be easily controlled. The purpose of this study was to develop a prototype system for the graft-taking enhancement of grafted seedlings using artificial lighting and to investigate the effect of air current speed on the distribution of air temperature and relative humidity in a graft-taking enhancement system. A prototype graft-taking system was consisted by polyurethane panels, air-conditioning unit, system controller and lighting unit. Three band fluorescent lamps (FL20SEX-D/18, Kumho Electric, Inc.) were used as a lighting source. Anemometer (Climomaster 6521, KANOMAX), T-type thermocouples and humidity sensors (CHS-UPS, TDK) were used to measure the air current speed, air temperature and relative humidity in a graft-taking system. In this system, air flow acted as a driving force for the diffusion of heat and water vapor. Air current speed, air temperature and relative humidity controlled by a programmable logic controller (UP750, Yokogawa Electric Co) and an inverter (MOSCON-G3, SAMSUNG) had an even distribution. Distribution of air temperature and relative humidity in a graft-taking enhancement system was fairly affected by air current speed. Air current speed higher than 0.1m/s was required to obtain the even distribution of environmental factors in this system. At low air current speed of 0.1m/s, the evapotranspiration rate of grafted seedlings would be suppressed and thus graft-taking would be enhanced. This system could be used to investigate the effects of air temperature, relative humidity, air current speed and light intensity on the evaportranspiration rate of grafted seedlings.

• 한국전산유체공학회지
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• 제19권3호
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• pp.24-28
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• 2014

With ever rising concerns about saving of fossil fuel resource, there have been an increasing demand for use of energy more efficiently. The electric motor driven inverters can be a great help to improve energy efficiency. They are also used to control the motor speed to the actual need. Therefore the use of them can lead to reduce energy consumption. In particular, the medium voltage(MV) drive systems used for pumps, fans, steel rolling mills and tractions have widespread applications in the industry. They cover power ratings from 0.4MW to 40MW at the MV level of 2.3kV to 13.8kV. The majority of the installed MV drive systems however, are in the 1MW to 4MW range with voltage rating from 3.3kV to 6.6kV. But they are required to reduce size and weight like other power electronic equipments. In this paper, we studied on the 3.3kV(105A) compact rack type inverter system for improving the cooling efficiency. At first, we confirmed the tendency of temperature with computational simulation using ANSYS ICEPAK and actual experimental tests. And then we researched thermal performance improvement designs in order to reduce temperature of the transformer for the safe operation. It can reduce temperature of transformer that using pipe type flow guide in the system. As a result, we found out more efficient solution by thermal-fluid analysis.

• Journal of Advanced Marine Engineering and Technology
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• 제35권2호
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• pp.238-243
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• 2011

인버터형 가변속 압축기를 사용한 냉각기를 최적으로 제어하기 위한 선행 연구이며, 외기온도를 변화 시켰을 경우 압축기의 회전수 변화와 전자팽창밸브의 개도 변화가 전체 시스템에 미치는 영향에 대해 실험적으로 규명하였다. 외기온도 $35^{\circ}C$와 외기온도 $30^{\circ}C$의 30Hz에서는 제어 시 피해야할 영역으로 판단됨을 확인할 수 있었으며, 압축기 회전수 제어로 인한 용량 제어범위는 외기온도 $35^{\circ}C$에서의 약 43~100%, 외기온도 $25^{\circ}C$에서는 46~100%, 외기온도 $10^{\circ}C$에서는 48~100%로 외기온도가 낮아질수록 용량제어범위는 작아짐을 알 수 있었다.

• 한국산학기술학회논문지
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• 제21권11호
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• pp.861-869
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• 2020

대용량 유도전동기용 인버터 개발을 위한 부하 장치는 고가의 제작 비용 및 제작에 많은 시간이 필요하므로 유도전동기 및 부하 장치를 대체할 수 있는 시뮬레이터 개발에 대한 필요가 증대되고 있다. 기존의 대용량 3상 유도전동기의 인버터용 부하 시뮬레이터는 리액터와 3상 PWM 정류기를 사용하여 시험용 인버터의 전류를 제어함으로써 단지 인버터의 부하로만 작용할 뿐 유도전동기의 특성을 모사하기 어렵다. 본 논문에서는 LCL 필터와 3상 PWM 정류기를 이용하여 3상 유도전동기의 모델과 부하 특성을 모사할 수 있는 실시간 시뮬레이터를 제안한다. PWM 인버터에 흐르는 전류는 3상 유도전동기의 고정자 전류를 모사하며 LCL 필터의 인덕터에 흐르는 전류와 커패시터 전압에 의해 제어된다. LCL 필터의 커패시터 전압은 3상 유도전동기의 회전자 자속에 의해 고정자 권선에 유기되는 유도기전력을 모사하며 인덕터 전류와 PWM 정류기에 의해 제어된다. 3상 유도전동기의 회전자 전류, 고정자 및 회전자 자속, 전동기 토크, 슬립 주파수 및 회전자 속도는 인버터에 흐르는 전류와 유도전동기의 상수로부터 유도된다. MATLAB/Simulink 시뮬레이션을 통하여 제안된 3상 유도전동기용 실시간 시뮬레이터의 전기적, 기계적 모델 특성 및 벡터제어 동작을 검증하였다.

• 대한전기학회논문지
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• 제36권12호
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• pp.874-887
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• 1987

The efficiency of a synchronous motor can be substantially improved by controlling armature voltage, field excitation, and load angle on optimum values which yield minimum input power at any specified torque and speed. This improvement is particularly noticeable in the case of light loads. In addition, the control of armature input voltage improves the power factor at which the motor operates. Employed in the analysis is a new equivalent circuit model of the motor which incorporates the frequency dependent nature of the motor parameters and the effects of iron loss. The stability of synchronous motor operation is studied by applying the Nyquist stability criterion to the linearized equations which describe the behavior of the motor as the motor loads perturb about a steady-state operating point. This investigation reveals that, in some cases, the stable region of the motor is delineated from the results of a computer simulation. With a view to reducing harmonic loss and improving torque pulsation from harmonic components, a very poweful pulse amplitude modulation (PAM) method using an 16-bit microcomputer has been developed. This method has the advantages of simplicity of control algorithms and requires small memory space for storing thyristor trigger angles for a three-phase PAM inverter. The method can be used for smooth control of both modulation depth and frequency over a wide range.

• Journal of Power Electronics
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• 제17권1호
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• pp.172-180
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• 2017

The repetitive control (RC) strategy is widely used in AC power systems because of its high performance in tracking period signal and suppressing steady-state error. However, the dynamic response of RC is determined by the fundamental period delay $T_0$ existing in the internal model. In the current study, a ($nk{\pm}i$)-order harmonic RC structure is proposed to improve dynamic performance. The proposed structure has less data memory and can improve the tracking speed by n/2 times. $T_0$ proves the effectiveness of the ($nk{\pm}i$)-order RC strategy. The simulation and experiments of ($6k{\pm}1$)-order and ($4k{\pm}1$)-order RC strategy used in the voltage source inverter is conducted in this study to control the harmonic current source, which shows the validity and advantages of the proposed structure.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(2)
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• pp.812-815
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• 2003

Most of all, DTC drive is very simple in its implementation because it needs only two hysteresis comparator and switching vector table for both flux and torque control. The switching strategy of a conventional direct torque control scheme which is based on hysteresis comparator results in a variable switching frequency which depends on the speed, flux, stator voltage and the hysteresis of the comparator. The amplitude of hysteresis band greatly influences on the drive performance such as flux and torque ripple and inverter switching frequency. In this paper the influence of the amplitudes of flux and torque hysteresis bands and sampling time of control program on the torque and flux ripples are investigated. Simulation results confirm the superiority of the DTC under the proposed method over the conventional DTC.