• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.489-500
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• 2014

This paper presents a simple modified unipolar carrier-based pulsewidth modulation (CB-PWM) strategy for the three-level neutral-point-clamped (NPC) voltage source inverter (VSI). Analytical expressions for the relationship between modulation reference signals and output voltages are derived. The proposed modulation technique for the three-level NPC VSI includes the maximum and minimum of the three-phase sinusoidal reference voltages with zero-sequence voltage injection concept. The proposed modified CB-PWM strategy incorporates a novel method that requires only of one triangular carrier wave for generate the gating pulses in three-level NPC VSI. It has the advantages of being simplifying the algorithm with no need of complex two/multi-carrier pulsewidth modulation or space vector modulation (SVM) and it's also simple to implement. The possibility of the proposed CB-PWM technique has been verified though computer simulation and experimental results.

• ETRI Journal
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• v.6 no.4
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• pp.21-30
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• 1984

A new control strategy for a PWM inverter with instantaneous feedback is suggested, theoretically analyzed and verified through simulations. This control gives excellent results under various load conditions.

• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.280-286
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• 1998

In this paper, space voltage vector pulsewidth modulation for 2-phase inverter is proposed. When this method is appled to 2-phase induction motor, the phase difference of voltage between phase A and B is fixed at $90^{\circ}$and amplitude of voltage of phase Ais same with that of phase B. This method have advantages over low-power servo system because this is simple method comparing to 3-phase space vector method which requires d-q transform.

• 전기의세계
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• v.23 no.4
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• pp.32-35
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• 1974

Thyristor inverter의 유형은 Switching기능에 따라 분류하고 있는데, 크게 나누어 Bridge형 converter와 Cycloconverter로 나누는데, 여기서는 이중 3상 Bridge형 Thyristor Inverter에 대한 전력변환과정을 Vector해석법에 의하여 그 개요를 설명하고, 여기에 현재 가장 효율적 switching방식이라 보고 있는 펼스폭변조환류게이트방식(Pulsewidth modulation commutation gating system)을 적용하였을 때의 효과를 첨가 설명코자 한다.

• Korean Journal of Optics and Photonics
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• v.11 no.5
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• pp.353-359
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• 2000

A harmonically mode-locked fiber ring laser cavlty was theoretically analyzed. The measured charactenstlcs of a 10 GHz erbium-doped fiber ring laser were used as a basis of the theoretical analysis. From the nonlinear Schroedinger equation of an actively mode-locked erblUm-doped fiber laser. the effects of the components inside the laser cavity have been analyzed includmg nonlinear effects from group-velocity dispersion (GVD) and self-phase modulation (SPM). Usmg the analysls. we have designed a laser cavity with minimum pulsewidth and chirp by changing the intracavity optical intensity and the bandwidth of the filter. In the new design, the chirp i, reduced by 2 times and the pulsewidth by 2A times. compared to the laser used in the experiment. iment.

• Korean Journal of Optics and Photonics
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• v.10 no.2
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• pp.146-151
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• 1999

We demonstrated a harmonic mode locking scheme that used regeneratie phase modulation to get a high and stable repetition rate in a figure-of-eight fiber soliton laser. From the detected beat spectra of the laser output, a sinusoidal clock freguency tone of 400 MHz, the 96th harmonics of the fundamental mode locking frequency, was extracted with a high Q filter and was used to drive the phase modulator, resulting in stable output of soliton pulse train synchronized with the modulation signal. Generated soliton pulses had FWHM pulsewidth of 930 fs and 3.1 nm linewidth, yielding pulsewidth-bandwidth product of 0.359 that was close to the transform limit. As the modulation frequency always followed the beat frequency of laser modes, stable harmonic mode locking was achieved without the adjustment of the cavity length, which has been commonly required in actively mode-locked lasers.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.605-610
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• 1991

In inverter system for driving induction motor, the output harmonics are hamrful in induction motor drive because it leads to ripple torque and induction interference. For electrical drives using PWM(Pulsewidth Modulation) inverters and ac motors, the methods for efficiency optimal control have been developed. In this paper, two different PWM methods for inverter and voltage control technique are described. In order to reduce or minimize losses, various forms of PWM strategy such as, PM (Positive Modulation) and NM (Negative Modulation) are discussed. The results show the feasibility of obtaining practically sinusoidal output waveforms which are highly desirable in most inverter application.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.3
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• pp.65-70
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• 2008

Capacitive position sensing with modulation technique is widely used in electrostatic actuator applications. To maximize the electrostatic force and the position-sensing gain, capacitors for driving and capacitors for sensing are shared, i.e, after applying the driving voltage with high-frequency modulating signals using op amps, the position is demodulated from the modulated signal. In high-voltage applications, however, low bandwidth of a high-voltage op amp hinders adding the high-frequency modulating signal to the driving voltage. In this paper, new and very simple driving and sensing method is proposed, in which the pulse-width modulated driving voltage eliminates the need of the high-frequency modulating signal for position sensing. This new algorithm is proved by the simulation results using Matlab/SIMULINK.

• Korean Journal of Optics and Photonics
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• v.10 no.5
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• pp.430-438
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• 1999

We have utilized soft-aperturing by gain media to develop a high-power tunable Ti:Sapphire laser with sub-40-fs and broad tuning range. The tunable spectral range was only limited by the bandwidth of mirrors. We made use of knife-edge slits near an intra-cavity prism controlled by micro-stepping-motors to tune the center wavelength continuously. The tunability of the center wavelength was ranged from 770 nm to 870 nm, and the measured pulsewidth was sub-40 fs throughout the above spectral range. The shortest pulsewidth was about 17 fs at the center wavelength of 820 nm and the spectral bandwidth was 72 nm. At 5 W pumping power of the Ar-ion laser we obtained average output power of 440 mW~580 mW. For the cw and Kerr-lens mode-lodking conditions, we have evaluated the value of an amplitude modulation to be ${\gamma}=2.5{\times}10^{-8}/W$ from the calculated waists of a Gaussian beam on the Ti:sapphire crystal surface. Using this result we demonstrate that the generation of sub-40-fs Kerr-lens mode-locked pulse can be described by the Ginzberg-Landau model which is a weak pulse shaping model.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10b
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• pp.218-223
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• 1993

In this paper, we present a full digital control scheme which controls currents and speed of the permanent magnet AC servo motor with large range of bandwidth and high performance. The current equations of the permanent magnet AC servo motor are linearized by feedback linearization technique. Both acceleration feedforward terms and IP controllers, whose gains are functions of motor speed, are used in order to control motor currents. In addition the phase delays in current control loops are compensated by placing phase lead-lag compensators after current commands, which make it possible to avoid high gains in the current controllers. Unity power factor can be achieved by the proposed current controller. Pulsewidth modulation is performed by way of the well-known comparison with a triangular carrier signals. The velocity controller is designed on the basis of the linearized model of the permanent magnet AC servo motor by the proposed current controller. The performance of the entire control system is analyzed in the presence of uncertainty in the motor parameters. The proposed control scheme is implemented using the digital signal processor-based controller composed of an Analog Device ADSP 2111 and a NEC78310. The pulsewidth modulation (PWM) signals are generated through a custom IC, SAMSUNG-PWM1, which has the outputs of current controllers as input. The experimental results show that the permanent magnet AC servo motor can be always driven with high dynamic performance by the proposed full digital control scheme of motor speed and motor current.