• Journal of Power Electronics
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• 제18권5호
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• pp.1325-1335
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• 2018

This paper presents a discontinuous pulse width modulation (DPWM) method to reduce switching losses in an indirect matrix converter (IMC) drive. The IMC has a number of power semiconductor switches. In other words, it consists of a rectifier stage and an inverter stage for AC/AC power conversion, which are composed of 12 and 6 switching devices, respectively. Therefore, the switching devices of the IMC suffer from high switching losses in the IMC drives. Various topologies to reduce switching losses have been studied by eliminating a number of switches from the rectifier stage. In this study, in contrast to prior research, a DPWM method is presented to reduce the switching losses of the inverter stage. The effectiveness of the proposed method to reduce switching losses in IMC drives is verified by simulations and experimental results.

• Journal of Power Electronics
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• 제17권6호
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• pp.1490-1499
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• 2017

The modular multilevel converter (MMC) is generally considered to be a promising topology for medium-voltage and high-voltage applications. However, in order to apply it to high-power applications, a huge number of switching devices is essential. The numerous switching devices lead to considerable switching losses, high cost and a larger heat sink for each of the switching device. In order to reduce the switching losses of a MMC, this paper analyzes the performance of the conventional discontinuous pulse-width modulation (DPWM) method and its efficiency. In addition, it proposes a modified novel DPWM method for advanced switching losses reduction. The novel DPWM scheme includes an additional rotation method for voltage-balancing and power distribution among sub modules (SMs). Simulation and experimental results verify the effectiveness and performance of the proposed modulation method in terms of its switching losses reduction capability.

• 전력전자학회논문지
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• 제21권6호
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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.

• 조명전기설비학회논문지
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• 제24권5호
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• pp.29-36
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• 2010

본 논문에서는 새로운 변조방식을 사용한 단상 인버터 시스템을 제안한다. 제안한 시스템은 buck-boost 변환기와 인버터로 구성되며 새로운 변조방식인 PWAM(Pulse Width/Amplitude Modulation)방식을 사용하여 제어한다. PWAM방식은 PWM(Pulse Width Modulation)방식과 PAM(Pulse Amplitude Modulation) 방식이 혼합된 새로운 변조방식이며 인버터의 입력단에 위치한 buck-boost 변환기는 일정한 직류전압을 입력으로 받아 가변 직류전압으로 변환한다. 인버터는 buck-boost 변환기에서 출력된 가변 직류전압을 입력으로 하며, PWM 구간에서는 PWM 스위칭을 하고 PAM 구간에서는 인버터가 스위칭을 하지 않음으로써 정현 교류전압으로 변환한다. 제안한 PWAM방식을 사용한 단상 인버터 시스템은 PAM 구간에서 스위칭 동작을 하지 않으므로 기존의 방식에 비해 스위칭 횟수가 감소하여 스위칭 손실을 줄일 수 있다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제15권4호
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• pp.493-500
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• 2015

A flyback converter operates with either pulse width modulation (PWM) or pulse frequency modulation (PFM) control scheme depending on the load current. At light load condition, PFM control is employed to reduce the switching frequency and thereby minimize the switching power loss. For heavier load, PWM control is used to regulate the output voltage of the flyback converter. The flyback controller has been implemented in a $0.35{\mu}m$ BCDMOS process and applied to a 40-W flyback converter. The light-load power efficiency of the flyback converter is improved up to 5.7-% comparing with the one operating with a fixed switching frequency.

• Journal of Power Electronics
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• 제18권6호
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• pp.1729-1750
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• 2018

Voltage source inverters (VSIs) are widely used to drive induction motors in industry applications. The quality of output waveforms depends on the switching sequences used in pulse width modulation (PWM). In this work, all existing optimal space vector pulse width modulation (SVPWM) switching strategies are studied. The performance of existing SVPWM switching strategies is optimized to realize a tradeoff between quality of output waveforms and switching losses. This study generalizes the existing optimal switching sequences for total harmonic distortions (THDs) and switching losses for different modulation indexes and reference angles with a parameter called quality factor. This factor provides a common platform in which the THDs and switching losses of different SVPWM techniques can be compared. The optimal spatial distribution of each sequence is derived on the basis of the quality factor to minimize harmonic current distortions and switching losses in a sector; the result is the minimum ripple loss SVPWM (MRSLPWM). By employing the sequences from optimized switching maps, the proposed method can simultaneously reduce THDs and switching losses. Two hybrid SVPWM techniques are proposed to reduce line current distortions and switching losses in motor drives. The proposed hybrid SVPWM strategies are MRSLPWM 30 and MRSLPWM 90. With a low-cost PIC microcontroller (PIC18F452), the proposed hybrid SVPWM techniques and the quality of output waveforms are experimentally validated on a 2 kVA VSI based on a three-phase two-level insulated gate bipolar transistor.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.986-989
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• 2004

The concept and results of a simple constant switching frequency delta modulation scheme suitable for DC-AC power conversion in uninterruptable power supply (UPS) applications are presented. Unlike the traditional delta modulation scheme, the scheme has a well defined harmonic spectrum, resulting in a simple filter design and reduced radio interference.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(5)
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• pp.17-20
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• 2000

Usually, in many applications, high frequency resonant inverters are used, and the PAM(Pulse Amplitude Modulation), PFM(Pulse Frequency Modulation) or PWM(Pulse Width Modulation) techniques are used to control the output power of resonant inverters. In this paper, a new switching scheme is proposed as a PWM control method. With the proposed method, it can be obtained that unity output displacement factor under the variable resonant frequency. The detail algorithm of the proposed PWM switching scheme and its charicteristics are discussed. And the validity of the proposed method is confirmed with the experimental results.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 전력전자학술대회 논문집
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• pp.287-290
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• 1998

This paper presents PWM method which modulates two third period only during one cycle of power converter. This method is compared with the conventionl sinusoidal modulation method applying to the power converter with large capacity necessitating low switching frequency. The presented modulation method enables to reduce power semiconductor rating, minimize switching loss, and improve the current wave form.

• Journal of Power Electronics
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• 제17권4호
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• pp.933-941
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• 2017

In this paper an improved low frequency selective harmonic elimination-PWM (SHE-PWM) technique for Cascaded H-bridge (CHB) converters is proposed. The proposed method is able to eliminate low order harmonics from the output voltage of the converter for a wide range of modulation indices. To solve SHE-PWM equations, especially for low modulation indices, a modified method is used which employs either the positive or negative voltage polarities of H-bridge cells to increase the freedom degrees of each cell. Freedom degrees of the switching angles are also used to increase the range of available solutions for non-linear SHE equations. The proposed SHE methods can successfully eliminate up to $25^{th}$ harmonic from a 7-level output voltage by using just nine switching transitions or a 150 Hz switching frequency. To confirm the validity of the proposed method, simulation and experimental results have been presented.