• Journal of Power Electronics
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• v.1 no.1
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• pp.26-35
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• 2001

In most inverter/converter applications SVPWM method is a preferred approach since it shows good characteristics in linear modulation range and waveform quality. In this paper, we propose a new carrier based SVPWM method for multi-level system, First, we survey the conventional carrier based SVPWM method, and investigate the problem of the conventional one for the multi-level system with the focus on the switching frequency harmonic flux trajectories. Finally, we propose a new carrier based SVPWM method that can reduce harmonic distortion. Simulation and experimental results are given for verification of the proposed SVPWM method.

• The Transactions of the Korean Institute of Power Electronics
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• v.2 no.3
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• pp.1-10
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• 1997

3-레벨 ZVS PWM DC/DC 컨버터는 풀브리지 ZVS PWM DC/DC 컨버터와 같은 동작 특성을 가지면서 입력전압의 반을 스위칭 소자의 차단전압으로 갖기 때문에 높은 입력을 갖는 DC-DC 변환시스템에 적합한 구조라 할 것이다. 그러나 부유 인덕턴스의 영향으로 인한 내외측 소자간의 차단전압 불균형의 문제와 경부하에서 영전압 스위칭 동작을 하지 못하므로 부하범위가 작다는 문제점을 가지고 있다. 이와 같은 문제점들은 시스템의 신뢰도를 낮추며, 경부하로 갈수록 효율을 떨어뜨리게 된다. 철도 차량과 같은 고압, 대용량의 시스템에서 이러한 문제들은 더욱 두드러 진다. 본 논문에서는 내외측 소자간의 차단전압 불균형의 문제를 없애며, 무부하에서 전부하까지 모든 부하 영역에서 영전압 스위칭 동작을 할 수 있는 새로운 3-레벨 ZVS PWM DC/DC 컨버터를 제시한다. 제안한 회로의 동작 특성과 타당성을 시뮬레이션 및 실험 결과를 통하여 입증한다.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.26-29
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• 2000

The conventional types of X-ray generators were bulky in physical size and heavy in weight and the control accuracies of the output voltages were not always satisfacotry. The high frequency switching inverter and converter technology on power conversion and control systems have been greatly closed up introducing power semiconducot devices. To decreasing the volume and the weight of high voltage transformer and to stabilize ripple. In this paper the newly developed x-ray generator in a low cost using duty modulation PWM inverter. This system verify improved performance by stabilize ripple of X-ray tube voltage and compared the reproducibility linearity and dose in single phase three phase and PSU.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.309-312
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• 2000

Single-phase multi-level AC-DC converter is proposed that is composed of diode bridge and switch. The number of the supply current level is depending on the individual current level of the converter. A converter circuit the number of the level is equal to $\textrm{2}^{M+1}$-1 The proposed circuit has converter with 31 current levels. When the number of current level is increased smoother sinusoidal waveform can be obtained directly and it is possible to control the supply current almost continuously from zero to maximum without step changes of generating high voltage as pulse width modulation switching loss is decreased it has an advantage in large capacity. it is illustrated technique are confirmed the validity and effectiveness through the simulation & experiments

• The Journal of Korean Institute of Communications and Information Sciences
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• v.9 no.3
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• pp.120-126
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• 1984

In this paper, there is presented the novel encoder circuit design method in the realization of exponential adaption process on the delta modulation coding of speech signals. The digital implementation has been adapted for the illustration of above, especially using a rate multiplier end a double integration circuit. The use of a double integration of the local decoder included in the ADM encoder in prove the undesirable characteristics which the low switching speed of the ratemultiplier couses the SQNR to decreuse, and the SQNR of the decoding signal by above realization is relatively uniformed in wide range of signal levels. The validity of the above design is verified by laboratory experiments.

• Journal of Power Electronics
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• v.9 no.5
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• pp.726-735
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• 2009

This paper presents a Bidirectional High-Frequency Link (BHFL) inverter that utilizes the Deadbeat controller. The main features of this topology are the reduced size of the inverter and fewer power switches. On the secondary side of the transformer, the active rectifier employs only two power switches, thus reducing switching losses. Using this configuration, the inverter is capable of carrying a bidirectional power flow. The inverter is controlled by a Deadbeat controller, which consists of the inner current loop, outer voltage loop and a feedforward controller. Additional disturbance decoupling networks are employed to improve the system's robustness towards load variations. A 1-kVA prototype inverter has been constructed and the Deadbeat control algorithm is experimentally verified. The experimental results show that the inverter has high efficiency (91%) with low steady state output voltage total harmonics distortion (1.5%).

• Journal of Power Electronics
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• v.16 no.4
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• pp.1316-1323
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• 2016

Multilevel inverters (MLIs) have been preferred over conventional two-level inverters due to their inherent properties such as reduced harmonic distortion, lower electromagnetic interference, minimal common mode voltage, ability to synthesize medium/high voltage from low voltage sources, etc. On the other hand, they suffer from an increased number of switching devices, complex gate pulse generation, etc. This paper develops an ingenious symmetrical MLI topology, which consumes lesser component count. The proposed level dependent sources concoction multilevel inverter (LDSCMLI) is basically a multilevel dc link MLI (MLDCMLI), which first synthesizes a stepped dc link voltage using a sources concoction module and then realizes the ac waveform through a conventional H-bridge. Seven level and eleven level versions of the proposed topology are simulated in MATLAB r2010b and prototypes are constructed to validate the performance. The proposed topology requires lesser components compared to recent component reduced MLI topologies and the classical topologies. In addition, it requires fewer carrier signals and gate driver circuits.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.5
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• pp.415-421
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• 2014

This study proposes a model-based predictive control for interleaved multi-phase DC/DC converters. The power values necessary to adjust the output voltage in the succeeding are predicted using a converter model. The output power is controlled by selecting the optimal duty cycle. The proposed method does not require controller loops and modulators for converter switching. This method can control the converter by calculating the optimal duty cycle, which minimizes the error between the reference and actual output voltage. The effectiveness of the proposed method is verified through simulations and experiments.

• Proceedings of the KIPE Conference
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• 2017.11a
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• pp.95-96
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• 2017

A three-level inverter is widely used thanks to its excellent performances, but the voltage may fluctuate at the neutral point of the split DC-Link. Neutral point voltage fluctuations cause inverter performance degradation and switching element damage, so the neutral point voltage control is essential. However, the neutral point control can be also limited by modulation index and power factor. This paper analyzes the limitation of the neutral point voltage control due to the limitation of zero-sequence voltage, and suggests a method to determine the region where the PWM has to be changed for a better neutral point control.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.2 no.2
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• pp.11-18
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• 2001

The design method of high potential generator of diagnostic X-ray apparatus by using inverter is presented. For the high potential generator, a line filter, a rectifier, a Pulse width modulation control, bridge drive, a high potential transformer and a high potential rectifier circuit were adopted. The high potential generator with switching frequency to be 40 KHz is fabricated by using design method presented in this method. The experimental results are as followings; variable volts of 0∼620 V and variable currents 50∼500 mA.