• Proceedings of the KIEE Conference
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• summer
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• pp.1154-1157
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• 2004

This paper presents design of a class D Amplifier using multi-level switching and Zero-Voltage-Switching(ZVS) technique. The amplifier circuit features zero voltage switching at all switches of the circuit and multi-level switching operation so that the higher efficiency and lower THD could be achieved. A 50-W prototype D class amplifier built and tested it. As a result, the maximum efficiency of $96\%$ and the THD of under $60\%$ were obtained.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.500-504
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• 1997

Current source inverter drives of auto sequentially commutated type are very popular in high power applications, because of simple power circuit configuration with four quadrant operation. But the six-step current output create harmonic problems and the input power factor of such a drive is not always good. In this respect pulse width modulated drives using gate turn off thyristors ( GTO ) are finding application, especially in traction drives. However the switching and snubber loses of a GTO do not permit the inverter switching frequency go beyond a few hundred hertz.This will again introduce low frequency harmonic problems. Multi level inverters of the 3-level and 5-level can be considered as an alternative to overcome the low switching frequency harmonic problem of the 2-level GTO inverters. But with multi level inverters the complexity of the power circuit increases. In this paper a combination of multi level ( 2-level and 3-level ) inverters and multi phase induction motor ( 3-phase and 6-phase) configurations are presented for high power VSI drives for traction applications with reduced inverter switching frequency requirements coupled with reduced voltage rating for the power switch.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.3
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• pp.366-371
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• 2012

In this paper, we propose an electric circuit using one common-arm of H-Bridge inverters to reduce the number of switching components in the multi-level inverter combined with H-Bridge inverters and transformers. And furthermore, we suggested a new multi-level PWM inverter using PWM level to reduce THD (Total Harmonic Distortion). We use a phase-shift switching method that has the same rate of usage at each transformer. Also, we test the proposed prototype 9-level inverter to clarify the proposed electric circuit and reasonableness of the control signal for the proposed multi-level PWM inverter.

• Journal of Electrical Engineering and information Science
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• v.1 no.2
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• pp.109-118
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• 1996

This paper deals with a new multi-level high voltage source inverter with GTO Thyristors. Recently, a multi-level approach seems to be the best suited for implementing high voltage conversion systems because it leads to harmonic reduction and deals with safe high power conversion systems independent of the dynamic switching characteristics of each power semiconductor device. A conventional multi-level inverter has some problems; voltage unbalance between DC-link capacitors and larger blocking voltage across the inner switching devices. To solve these problems, the novel multi-level inverter structure is proposed.

• Journal of Electrical Engineering and Technology
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• v.2 no.3
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• pp.373-378
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• 2007

Soft switching was applied to the multi-level inverter to enhance the performance of the high-intensity discharge (HID) ballast used in vehicle headlights. The electrical properties were investigated and the available modeling of ballast in steady state was calculated using mathematical methods. The result was used in analyzing the power characteristics. The modeling was confirmed by the experiment.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.4
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• pp.337-343
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• 2015

The multi-level inverters are highly efficient for high-power and medium-voltage AC driving applications, such as high-speed railway systems and renewable energy resources, because such inverters generate lower total harmonic distortion (THD) and electromagnetic interface (EMI). Lower switching stress occurs on switching devices compared with conventional two-level inverters. Depending on the multi-level inverter topology, the required components and number of switching devices are different, influencing the overall efficiency. Comparative studies of multi-level inverters based on loss analysis and output characteristic are necessary to apply multi-level inverters in high-power AC conversion systems. This paper proposes a theoretical loss analysis method based on piecewise linearization of characteristic curves of power semiconductor devices as well as loss analysis and output performance comparison of five-level neutral-point clamped, flying capacitor inverters, and high-level cascaded H-bridge multi-level inverters.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.4
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• pp.291-297
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• 2012

Recently, Switching devices become cheaper, depending on the multi-level inverters are considered as the power-conversion systems for high-power and power-quality demanding applications. The multi-level inverters can reduce the THD(Total Harmonic Distortion) as the output which is similar sinusoidal waveform by synthesizing several capacitor DC voltages. However it has some disadvantages such as increased number of components, complex PWM control method. Therefore, this paper is proposed the new multi-level inverter topology using an new H-bridge output stage with a bidirectional auxiliary switch. The proposed topology is the 4-level 3-phase PWM inverter with less switching part than conventional multi-level inverters and reactive power control possible. In order to understand the new multi-level inverter, topology analysis and switching patterns and modes according to the current loop are described in this paper. The proposed multi-level inverter topology is validated through PSIM simulation and the experimental results are provided from a prototype.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.673-676
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• 2005

In this paper, we proposed the electric circuit using one common arm of H-Bridge Inverters to reduce the number of switching component in multi-level inverter combined with H-Bridge Inverters and Transformers. and furthermore we suggested the new multi-level PWM inverter using PWM level to reduce THD(Total Harmonic Distortion). and we used the switching method that can be same rate of usage at each transformer. Also, we tested the proposed prototype 9-level inverter to clarify the proposed electric circuit and reasonableness of control signal for the proposed multi-level PWM inverter.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1477-1479
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• 2005

In this paper, we proposed the electric circuit using one common arm of H-Bridge inverters to reduce the number of switching component in multi-level inverter combined with H-Bridge Inverters and Transformers. and furthermore we suggested the new multi-level PWM inverter using PWM level to reduce THD(Total Harmonic Distortion) and we used the switching method that can be same rate of usage at each transformer. Also, we tested the proposed prototype 15-level inverter to clarify the proposed electric circuit and reasonableness of control signal for the proposed multi-level PWM inverter.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.6
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• pp.628-634
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• 2004

The soft switching is applied to the multi-level inverter to enhance the characteristics of HID(High Intensity Discharge) Ballast in headlight of vehicle. The electrical properties are investigated. The available modeling of the ballast in steady-state is calculated using mathematical method and the result is used in analyzing the power characteristics and design of the system. Finally the designed system md modeling is confirmed by the experiment.