• Journal of Electrical Engineering and Technology
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• v.10 no.2
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• pp.574-585
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• 2015

This paper aims to improve the performance of conventional direct torque control (DTC) drives proposed by Takahashi by extending the idea for 5-level inverter. Hybrid cascaded H-bridge topology is used to achieve inverter voltage vector composed of 5-level of voltage. Although DTC is very popular for its simplicity but it suffers from some disadvantages like- high torque ripple and uncontrollable switching frequency. To compensate these shortcomings conventional DTC strategy is modified for five levels voltage source inverter (VSI). Multilevel hysteresis controller for both flux and torque is used. Optimal voltage vector selection from precise lookup table utilizing 12 sector, 9 torque level and 4 flux level is proposed to improve DTC performance. These voltage references are produced utilizing a hybrid cascaded H-bridge multilevel inverter, where inverter each phase can be realized using multiple dc source. Fuel cells, car batteries or ultra-capacitor are normally the choice of required dc source. Simulation results shows that the DTC drive performance is considerably improved in terms of lower torque and flux ripple and less THD. These have been experimentally evaluated and compared with the basic DTC developed by Takahashi.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1589-1596
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• 2015

A novel control method of a three-phase PWM inverter with LC filter is proposed. The transfer function of LC filter is the same as that of 2nd order low pass filter(2nd LPF) which has a zero damping ratio. A simple method of implementing 2nd LPF with damping ratio is to add resistor to inductor or capacitor of LC filter. In an industrial application, it is not practical to adopt damping resistor because it results in losses being proportional to square of current flowing through resistor. Instead of using damping resistors, the proposed active damping control(ADC) utilizes all pass filter(APF) and considers inherent processing delay of digital controller. The overall transfer function of the proposed method is the same as a 2nd LPF and its damping ratio is also controllable via control variables. Detailed design and implementation of controller is also presented. Experiments are conducted with a 7.5kVA induction motor drive system controlled by PWM converter and inverter. Test waveforms are also presented to verify the proposed LC filter control algorithm.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.5
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• pp.501-507
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• 2005

This paper proposes a Hybrid Random PWM(HRPWM) technique using a LF2407 DSP board in order to spread the power spectra of an induction motor. The proposed method is composed to the PRBS (Pseudo-Random Binary Sequence) with the Lead-Lag random bit and the random triangular carrier for the logical comparison. Also, a DSP generates the random number, the PRBS and the three-phase reference signal, a MAX038 chip operating as frequency modulator generates the random triangular carrier. For verification of the proposed method, the experiments were conducted with a three-phase adjustable speed a.c drives, and the results of simulations and experiments are presented.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.559-561
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• 2008

본 논문에서는 실용적이며 신뢰성 있는 고전압 대용량 유도전동기 구동용 H-브릿지 멀티레벨 인버터를 개발하여 산업 현장에 적용한 내용을 소개하였다. 실용적인 PWM (Pulse Width Modulation)과 PEBB (Power Electronics Building Blocks)에 기초한 신뢰성 있는 분산 제어를 적용하였으며, H-브릿지 멀티레벨 인버터를 이용한 유도 전동기 벡터 제어시의 위상지연을 보상하여 제어 성능을 향상시켰다. 또한, Power Cell 고장 발생시 시스템을 정지하지 않으면서 효율적 운전을 가능하게 하는 3상 불평형 제어를 이용하여 잉여성을 확보하였다. 다양한 전압과 용량의 H-브릿지 멀티레벨 인버터를 설계 및 제작하여 각종 부하 실험, 산업 현장 적용을 통해 적용된 방법의 타당성과 실용성을 입증하였다. 또한 실제 제품 설계, 생산, 판매, 유지 보수 과정을 통해 설계의 유연성, 생산의 효율성, 유지 보수의 편리함, 그리고 사용자 요구에 대한 대응성이 우수함을 확인하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.11
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• pp.886-897
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• 1990

This paper is proposed new optimal PWM scheme is based on a defined linear relationship between the successive pulsewidths of the PWM pattern. The calculation of the pulsewidths in the new PWM scheme is caried out without referring to the equations of CW and MW. With this scheme the PWM pattern for microprocessor controlled inverters can be composed easily by obtaining the optimal increment in sucessive pulsiwidths of the pattern. Furthmore, the harmonic level at the output of PWM inverter are always very low because this PWM pattern is selected on the basis of minimum THD. Theis scheme is applied to 1(Hp), three phase induction motor, and compared with conventional regular PWM scheme. The results of calculations and experiments show that new optimal PWM scheme could provide an effective generalized approach for minimization of harmonics in the VSI-PWM inverter.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.238-240
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• 2005

This paper presents harmonic evaluation of an IAT(Intra Airport Transit) system in Incheon International Airport. It will be used electric vehicles with 80 kW per car that are produced Mitsubishi Heavy Industries Ltd, and one car is constructed with SIV(Static Inverter), VVVF controller and two induction motor. The operated vehicles in the IAT system are rapidly changing DC load and at a feeding substation, 3-phase electric power is transferred to DC 750 V by rectifier. Since, vehicles are also changing continuously, the voltages for the load fluctuate in the IAT system, and moreover, the fluctuating voltages generate high-order har -monies. This means that there is the difficulty in maintaining power quality in KEPCO systems' side. Therefore, the power quality of the IAT system in Incheon International Airport is evaluated using PSCAD/EMTDC simulator in the paper The THD(Total Harmonic Distortion) of voltages and TDD(Total Demand Distortion) of currents, indices are calculated for the IAT system using the results of PSCAD/EMTDC dynamic simulation.

• Proceedings of the KIEE Conference
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• 2006.07d
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• pp.1868-1870
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• 2006

Neural network is used in many fields of control systems, but input-output patterns of a control system are not easy to be obtained and by using as single feedback neural network controller. And also it is difficult to get a satisfied performance when the changes of rapid load and disturbance are applied. To resolve those problems, this paper proposes a new algorithm which is the neural network controller. The new algorithm uses the neural network instead of activation function to control object at the output node. Therefore, control object is composed of neural network controller unifying activation function, and it supplies the error back propagation path to calculate the error at the output node. As a result, the input-output pattern problem of the controller which is resigned by the simple structure of neural network is solved, and real-time learning can be possible in general back propagation algorithm. Application of the new algorithm of neural network controller gives excellent performance for initial and tracking response and it shows the robust performance for rapid load change and disturbance. The proposed control algorithm is implemented on a high speed DSP, TMS320C32, for the speed of 3-phase induction motor. Enhanced performance is shown in the test of the speed control.

• The Journal of Korean Institute for Practical Engineering Education
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• v.3 no.1
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• pp.15-24
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• 2011

Modeling and simulation for Green Energy depends largely on the type of system under investigation. The topics are very wide ranging from semiconductor physics (solar), electrical motor/generator (wind turbines), power electronics (grid connections) to typical control strategies. To correctly model these technologies requires a broad set of models and various simulation techniques. To further refine or detail the simulation the modeling has to be performed on a specific level, being system, circuit or component level. Combinations of several levels allows gradually improving the validity of the overall model against available parameters and model equations.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.3
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• pp.239-246
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• 2015

A novel control method of a three-phase PWM inverter with LC filter is proposed. The transfer function of LC filter is the same as that of second-order low pass filter(LPF), which has a zero damping ratio. A simple method of implementing second-order LPF with damping ratio is to add a resistor in an LC circuit. However, in a real power system, adopting damping resistors is impractical because it results in losses proportional to the square of the current flowing through the resistors. Instead of inserting resistors, the proposed control strategy utilizes the measured capacitor voltages to control the oscillation of LC circuit. The overall transfer function of the proposed method is the same as a second-order LPF, and its damping ratio is controllable via control variables. The current controller can have overshoots caused by LC filter. Improved current controller is implemented by an equivalent second-order of LC filter. A 7.5 kVA PWM converter and a PWM inverter with a 5.5 kW induction motor are set up to verify the proposed control algorithm. Test waveforms are also presented to verify the proposed LC filter control algorithm.

• Proceedings of the KIEE Conference
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• 1999.07b
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• pp.794-796
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• 1999

본 논문에서는 3상 유도전동기의 속도를 제어하는데 기존 제어기의 문제점을 해결하고 최적화하기 위해서 유전자 알고리즘을 이용한 하이브리드 퍼지 -PID(HFPID) 제어기를 고안하고, 이에 대한 파라미터 설정 방법을 제안한다. 유도전동기의 제어는 지연시간이 길고, 비선형성이 강하며, 부하변동이 잦은 프로세스이기 때문에, 기존의 제어방식으로는 만족할만한 결과를 얻을 수 없다. 제안한 하이브리드 퍼지-PID 제어기는 PID 제어기의 장점인 과도기의 우수성과 퍼지 제어기의 장점인 정상기의 우수성을 퍼지 변수로 결합시켜 설계한다. 이 제어기에 유전자 알고리즘을 적용하여 최적의 퍼지 및 PID 파라미터를 설정하다. 그리고 이 제어기를 3상 유도전동기의 속도 제어에 응용한다. 또한 속도오차에 대한 룩업 표를 만들어 온라인 실시간 제어를 가능하게 한다. 이상의 과정을 3상 유도전동기에서 컴퓨터 시뮬레이션 하였다. 시뮬레이션 결과를 비교해 볼 때, 하이브리드 퍼지-PID 제어기는 기존의 제어기 보다 전동기의 속도 및 토크성분 전류 둥의 특성에서 우수한 성능을 보였다.