• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.253-254
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• 2006

this paper suggest a new space vector PWM modulation method with short processing time which does not need idenfication of nearest three vectors(NTV) and duty calculation for each vector. The suggested PWM method makes mean value of phase voltage to be same as reference during every modulation period by use of a triangle in small hexagon on multi-level vector space. This paper described the suggested modulation method can be successfully applied to the space vector modulation use of multi-level inverter by computer simulations and experiments.

• Journal of Power Electronics
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• v.19 no.6
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• pp.1515-1526
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• 2019

Ear-piercing high-frequency noise from electromagnetic vibrations in motors has become unacceptable in sensitive environments, due to the application of pulse width modulation (PWM) and in consideration of switching losses. This paper proposed a synchronous periodic frequency modulation (SPFM) method based on the interleaving technique for paralleled three-phase voltage source inverters (VSIs) to eliminate PWM vibration noise. The proposed SPFM technique is able to effectively remove unpleasant high-frequency vibration noise as well as acoustic noise more effectively than the conventional periodic carrier frequency modulation (PCFM) and interleaving technique. It completely eliminates the vibration noise near odd-order carrier frequencies and reduces the PWM vibration noise near even-order carrier frequencies depending on the switching frequency variation range. Furthermore, the SPFM method is simple to implement and does not employ additional circuits in the drive system. Finally, the effectiveness of the proposed method has been confirmed by detailed experimental results.

• Current Optics and Photonics
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• v.6 no.1
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• pp.39-43
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• 2022

Underwater optical wireless communication (UOWC) is a good candidate for high-speed underwater wireless communication. In this work, we compare the performance of several modulation techniques for a UOWC system consisting of a light-emitting diode (LED) with an operating wavelength of 405 nm and a Si avalanche photodiode (APD). In this work, we consider six modulation schemes: 4-quadrature amplitude modulation (QAM), 8-QAM, quadrature phase shift keying (QPSK), binary phase shift keying (BPSK), on-off keying (OOK), and 4-pulse amplitude modulation (PAM). We also consider the cases of pure water and seawater for the working conditions. Our results show that 4-QAM and 8-QAM perform the best, in terms of communication distance and transmission power efficiency, for all water types considered.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.6
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• pp.530-537
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• 2016

This work deals with a switching method for minimizing overcurrent in a three-phase interleaved bidirectional DC-DC converter with frequency modulation. Generally, a three-phase interleaved DC-DC converter is used to reduce a current ripple component. The combined operation of three-phase and two-phase converters can significantly reduce the ripple component. However, the conventional PWM method cannot solve severe overcurrent during phase transfer or frequency variation for power control. To overcome this problem, this work proposes a new PWM switching method. A 3 kW DC-DC power converter is designed and implemented, and the converter is operated in discontinuous current mode with varying switching frequencies for power control. Simulation and experimental results show the validity of the proposed switching method. The proposed switching method can be widely used in the field of current ripple reduction for three-phase interleaved bidirectional DC-DC converters.

• Korean Journal of Optics and Photonics
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• v.3 no.3
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• pp.143-147
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• 1992

1)iscussed in this paper are the effects of phase modulation on the line spread functions (LSF) and MTFs of ;I binocular objective system. The binocular objective lens is made in Korea. It has rotationally symmetric aberrations. The LSFs and MTFs are measured experimentally. The phase modulation is carried out by applying phase retardation $\pi$ on the aperture. The area where the phase is not retarded presents a double annular type. The OTF curves of phase modulated aperture are compared with that of unmodulated aperture. The comparison shows that there is the aberration compensation effect in aberration loaded system. Therefore the performance of many optical system can be improved without any loss of light energy by properly modulating the phase on the aperture.

• Journal of Power Electronics
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• v.16 no.2
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• pp.480-489
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• 2016

A novel hybrid carrier-based pulse width modulation (CBPWM) scheme that combines unipolar and dipolar modulations is proposed for single-phase three-level rectifiers, which are widely applied in railway traction drive systems. The proposed CBPWM method can satisfy the volt-second balancing principle in the complete modulation index region through overmodulation compensation. The modulation scheme features two modulation modes: unipolar and dipolar. The operation range limits of these modulation modes can be modified by changing the separation coefficient. In comparison with the traditional unipolar CBPWM, the proposed hybrid CBPWM scheme can provide advantageous features, such as lower high-order harmonic distortion of the line current and better utilization of switching frequency. The separation coefficient value is optimized to achieve the maximum utilization of these advantages. The experimental results verify the feasibility and effectiveness of the proposed hybrid CBPWM scheme.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2129-2138
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• 2016

The full-bridge inverter, widely used for single-phase photovoltaic grid-connected applications, presents a leakage current issue. Therefore, an AC bypass branch is introduced to overcome this challenge. Nevertheless, existing modulation strategies entail drawbacks that should be addressed. One is the zero-crossing distortion (ZCD) of the AC current caused by neglecting the AC filter inductor voltage. Another is that the system cannot deliver reactive power because the AC bypass branch switches at the power frequency. To address these problems, this work proposes an optimized hybrid modulation strategy. To reduce ZCD, the phase angle of the inverter output voltage reference is shifted, thereby compensating for the neglected leading angle. To generate the reactive power, the interval of the negative power output is calculated using the power factor. In addition, the freewheeling switch is kept on when power is flowing into the grid and commutates at a high frequency when power is fed back to the DC side. In this manner, the dead-time insertion in the high-frequency switching area is minimized. Finally, the performances of the proposed modulation strategy and traditional strategies are compared on a universal prototype inverter. Experimental results validate the theoretical analysis.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.5
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• pp.29-36
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• 2010

In this paper, we propose a single-phase inverter system using new modulation method. The proposed system is composed of a buck-boost converter and an inverter and controlled by PWAM scheme. PWAM method is a new modulation method which is the incorporation of PWM(Pulse Width Modulation) and PAM(Pulse Amplitude Modulation) methods. The DC voltage which is the input voltage of buck-boost converter is converted into a variable DC voltage by buck-boost converter. Also, the variable DC voltage which is the output voltage of buck-boost converter is converted into a sinusoidal AC voltage by inverter. The input voltage of inverter is processed by PWM switching in PWM section and bypassed in PAM section. By using PWAM method, switching action is not existed in PAM section and thus the times of switching is reduced. As a result, the switching loss can be reduced.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.8
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• pp.1893-1898
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• 1998

We have redefined the $\alpha$ -parameter of the extended transmitters in the presence of self-phase modulation (SPM) induced chirp. The $\alpha$ -parameter is effectively lowered to about 1, when the SPM effect with the launching power of 12.5dBm (maximum launching power to avoid stimulated Brillouin scattering(SBS)) is included, compared to the $\alpha$ -parameter of the transmitter algone. The lowered $\alpha$ -parameter has improved the transmission performance significantly regardless the transmitter is operated with positive or negative chirp. The SPM-induced effective $\alpha$ -parameter can be used as a design parameter for the high speed (10 Gbps) transmission systems.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.37 no.1
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• pp.58-62
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• 2000

We Propose modulation scheme using I-Q modulation for transmitting different information simultaneously. For transmitting 1bit of each information, we apply QPSK scheme, for more bits, MAPSK. At the second modulation stage, We mix PN wavefoms with APSK waveforms for spreading bandwith. BER(Bit Error Rate) of each Information of the proposed scheme is analyzed on computer simulation. Finally we show power spectrum before and after spreading bandwidth.