• 한국음향학회지
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• 제17권8호
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• pp.103-109
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• 1998

디지털신호의 변조에는 기본적으로 진폭 편이 변조(ASK: Amplitude-Shift Keying), 주파수 편이 변조(FSK: Frequency-Shift Keying), 위상 편이 변조(PSK: Phase-Shift Keying) 등의 세 가지 방법이 있다. 본 논문에서는 표본클록 합성계수 방식에 관한 이론을 고찰하고, 클록초기치 누적방식의 DDFS를 이용하여 위에서 언급한 변조방법을 실현할 수 있는 주파수 도약 대역 확산 통신에 적합한 변조기를 구현하였다. 또한, 합성된 출력주파수 의 정현파형에 대한 스펙트럼 분석과 PN(Pseudo Noise) 부호를 사용한 순시적인 주파수 도 약 상태, 위상제어의 가능성 등을 확인한 결과 실험으로부터 다음과 같은 결과를 얻었다. 첫 째, 합성된 출력주파수는 주파수 Index에 따라 기준주파수에 정확히 정수배가 되며, 둘째, 합성된 정현파형의 스펙트럼으로 기본파와 여러 고조파의 크기를 비교하여 본 결과 50[dB] 이상의 차이가 남으로서 고조파 성분들이 상당히 감소되었음을 확인하였고, 셋째, PN 코드 를 사용하여 순시적인 주파수 도약 상태를 확인하여 본 결과 스위칭 시간이 빠르기 때문에 주파수 도약 특성이 뛰어남을 알 수 있었으며 또한, 누산기의 set/reset 상태를 변화시킴에 따라 위상이 제어됨을 입증하였다.

• 조명전기설비학회논문지
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• 제12권1호
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• pp.69-77
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• 1998

무정전전원장치는 중요설비에 안정된 전원을 공급하는 기기로서 컴퓨터, 통신시스템 등에 필수적인 장치가 되었으며 최근에는 고주파스위칭 기술의 발전으로 여러 가지 제어방식이 제안되고 있다. 본 논문은 3상 무정전전원장치의 PWM 인버터를 DSP로 제어하고 PI제어기의 피드 포워드항을 부하전류 예측기법에서 예측된 부하전류의 함수로 둠으로써 비선형부하에 대해서도 출력전압의 왜형률을 저감시킬 수 있는 방법을 제시한다. 시뮬레이션과 실험을 통하여 제안된 제어방법의 타당성을 입증하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집
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• pp.65-68
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• 2001

In the vector control methods of induction motor, the stator current is divided into the flux and torque component current. By controlling these components respectively, the methods control independently flux and torque as in the DC motor and improve the control effects. To apply the vector control methods, the position of the rotor current is identified. The indirect vector control use the parameters of the machine to identify the position of rotor flux. But due to the temperature rise during machine operation, the variation of rotor resistance degrades the vector control. To solve the problem, the q-axis is aligned to reference frame without phase difference by comparing the real flux component with the reference flux component. Then to compensate the slip, PI controller is used. The proposed method keeps a constant slip by compensating the gain of direct slip frequency when the rotor resistance of induction motor varies. To prove the validations of the proposed algorithm in the paper, computer simulations is executed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 학술대회 논문집 전문대학교육위원
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• pp.98-101
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• 2002

The switching-mode power converter has been widely used because of its features of high efficiency and small weight and size. These features are brought by the ON-OFF operation of semiconductor switching devices. However, this switching operation causes the surge and EMI(Electromagnetic Interference) which deteriorate the reliability of the converter themselves and entire electronic systems. This problem on the surge and noise is one of the most serious difficulties in AC-to-DC converter. In the case of carrier frequency selection, output-voltage of steady state and transient state is fully regulated. A RPWM control method was proposed in order to smooth the switching noise spectrum and reduce it's level. Experimental results are verified by converter operating at 300V/1kW with 5%${\sim}$30% white noise input. Spectrum analysis is performed on the Phase current and the CM noise voltage. The former is measured with Current Probe and the latter is achieved with USN. which are connected to the spectrum analyzer respectively.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.1151-1153
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• 2003

In this paper, switching surge voltage distribution in stator windings of induction motor driven by IGBT PWM inverter is studied. To analyze the irregular voltage of stator winding, equivalent circuit model of inverter-cable-motor was proposed and high frequency parameter is computed by using finite element method (FEM). Electromagnetic transient program (EMTP) analysis of the whole system for induction motor and PWM inverter is proposed. In order to experiment, an induction motor, 380 [V], 50 [HP], with taps from one phase and a switching surge generator was built to consider the voltage distribution.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 추계학술대회 논문집 학회본부
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• pp.373-377
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• 1996

Recently, active power factor control for AC/DC converter has been required to replace for a conventional diode rectifier. A voltage type AC/DC converter is widely used to obtain higher regulated DC voltage than input voltage with a unity power factor and a sinusoidal line current. This paper describes several active power factor control method for AC/DC converter. The analysis of several active power factor control is given. The simulations for hysteresis control, peak current control. constant frequency control and average current mode control are represented and compared.

• Journal of Power Electronics
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• 제10권6호
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• pp.724-732
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• 2010

This paper presents an effective rotor current controller for variable-speed stand-alone doubly fed induction generator (DFIG) systems feeding an unbalanced three-phase load. The proposed current controller is developed based on proportional plus two resonant regulators, which are tuned at the positive and negative slip frequencies and implemented in the rotor reference frame without decomposing the positive and negative sequence components of the measured rotor current. In addition, the behavior of the proposed controller is examined in terms of control performance and stability with respect to rotor speed variations, i.e., slip frequency variations. Simulations and experimental results are shown to validate the robustness and effectiveness of the proposed control method.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2015년도 전력전자학술대회 논문집
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• pp.377-378
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• 2015

본 논문에서는 유기랭킨 사이클(organic rankine cycle: ORC) 발전 시스템에서 터빈과 발전기의 속도를 추정하는 방법을 제안한다. 다이오드 정류기에 의해 왜곡된 발전기 3상 단자 전압은 PLL 기법을 이용한 속도추정의 성능을 저하시키므로, 정상분 추출과 맥동성분 제거를 위한 상태관측기와 주파수 가변형 PR 제어기를 동기좌표계 PLL 기법에 적용하여 발전기의 속도를 추정한다. 제안하는 터빈과 발전기의 속도추정 방법은 실험 결과를 통해 그 성능을 검증한다.

• 전기학회논문지P
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• 제57권4호
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• pp.383-387
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• 2008

This paper analyzes the operation characteristics of a self excited induction generator with Steinmetz connection. For this analysis, the symmetrical components analysis is used to obtain the related expressions and the excitation capacitance and the magnetizing reactance are determined in turn by the condition of self excitation which includes the input impedance of the generator as viewed across load terminals. Two simultaneous equations of the condition of self excitation itself are solved by using the real and imaginary function in an application software. This method is applied to simulate the operation characteristics when the generator is driven at rated speed and the specified excitation capacitor is connected across the lagging phase. The results show that better operation characteristics except generated frequency are obtained by using relatively large excitation capacitance and resistive load.

• 한국정밀공학회지
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• 제17권1호
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• pp.171-178
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• 2000

In this study, an indirect method to estimate the setup runout of a ball-end mill from cutting force signal is proposed. This runout makes cutting forces of each tooth of the milling cutter unequal. By transforming the cutting force model from time domain to frequency domain through time-convolution theorem, the magnitude and phase angle of runout can be explicitly expressed with material constants, cutting conditions, and force signal. The static setup runout can be obtained by extrapolating estimated effective runout, which is independent of feedrate but decreases linearly with increase in axial depth of cut. The setup runout estimated by slot cutting experiments, shows good agreement with the measured one.