• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.5
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• pp.231-237
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• 2005

Many conventional multi-level inverters have detected switching faults by using the over voltage and current. However, fault detection of the switching elements is very difficult because the voltage and current due to each switching fault decrease more than the normal operation. Moreover, the dc-link unbalancing voltage causes a serious problem in the safety and reliability of system when the 3-level inverter faults occur Therefore, this paper proposes the simple fault diagnose method and the neutral-point-voltage control method that can protect the 3-level inverter system from the unbalancing voltage of the do-link capacitors when the faults of switching elements occur in the 3-level inverter that is very efficient in ac motor drives of the high voltage and high power applications. Through experiment results, the validity of the proposed method is demonstrated.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.512-514
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• 2007

The number of transformers and the size of transformers in inverter using 3-phase transformer could be reduced compare with a multi-level inverter using single phase transformer. but still the 3-phase transformer inverter needs many switches. In this study, we proposed the isolated multi-level inverter using 3-phase transformers and common arm. Also, the equal-area method is used to calculate conduction angle with switching frequency equal to output fundamental frequency and it can reduce harmonics component of output voltage and switching loss. Finally, We tested multi-level inverter to clarify electric circuit and reasonableness through Matlab simulation and experiment by using prototype inverter.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.12
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• pp.2359-2369
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• 2009

The study on the multi-level inverter has been increasingly progressing to reduce the switching loss and improve the THD of output current in photovoltaic inverter. Recently, the main topics of multi-level inverter are to reduce the number of devices maintaining the power quality. Therefore, the novel topology was proposed for these problem which is composed of the isolated H-bridge multi-level inverter using the three phase low frequency transformer. The proposed multi-level inverter may not be need for a independent DC power, diode and capacitor. Specially, It has a advantage in generating high voltage source. The proposed approach is verified through simulation and experiment.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1995.10a
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• pp.80-84
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• 1995

ABSTRACT - This paper presents a software based 3 phase 5 level pulse-width modulation(PWM) inverter to reduce total harmonic distortion. The proposed modulation technique can reduce total harmonic distortion and significantly improve the performance of the inverter. In the modulation mode where the frequency ratio is 36 and modulation index is 1.2∼2.0, harmonic components have been mostly eliminated and the magnitude of fundamental component have been maximized by the 3 phase 5 level PWM inverter.

• Journal of Power Electronics
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• v.3 no.2
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• pp.90-98
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• 2003

This paper presents a performance analysis in steady-state of a novel type Auxiliary Resonant Commutation Snubber-linked 3-level 3-phase voltage source soft switching inverter suitable and acceptable for high-power applications in comparison with other three types of 3-level 3-phase voltage source soft switching inverters. This soft switching inverter operation which can operate under a condition of Zero Voltage Switching (ZVS). The practical steady -state performances of this inverter are illustrated and evaluated on the basis of the experimental results.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.4
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• pp.746-755
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• 2001

This paper proposes a snubber circuit for flying capacitor 3-level inverter and converter. The proposed snubber circuit makes use of Undeland snubber as basic snubber unit. It has such an advantage of Undeland snubber used in the two-level inverter. Compared with conventional RLD/RCD snubber for 3-level inverter and converter, the proposed snubber keeps such good features as fewer number of components, reduction of voltage stress of main switching devices due to low overvoltage, and improved efficiency of system due to low snubber loss. In this paper, the proposed snubber is applied to multilevel flying capacitor inverter and its feature is demonstrated by computer simulation and experimental result.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.3
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• pp.341-351
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• 1996

The values for the average and rms currents in a three-level PWM inverter are required in order to select the various components such as power semiconductor devices, capacitors and reactors of inverter circuit. And those are very useful for the designing of the heat sink. In this paper, therefore, the simple current equations are proposed for a three-level PWM inverter. Analysis of inverter current waveforms indicate that the average and rms inverter currents are dependent on the load power factor and PWM modulation index (Ma). Error analysis and experiment results verify the effectiveness of the proposed current equations. (author). refs., figs., tabs.

• Journal of the Semiconductor & Display Technology
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• v.14 no.4
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• pp.72-77
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• 2015

Three-level diode clamped multilevel inverter, generally known as neutral point clamped (NPC) inverter, has an inherent problem causing neutral point (NP) potential variation. Until now, the NP potential problem of variation has been investigated and lots of solutions have also been proposed. This paper presents a neutral point voltage control technology using the anti-windup PI controller and offset technology of PWM (Pulse Width Modulation) to control the variation of NPC 3-phase three-level inverter neutral point voltage. And the proposed algorithm is tested and verified using a PLL (Phase Locked Loop) in order to synchronize the phase voltage from the line voltage of grid. It significantly improves the voltage balancing under a solar fluctuation conditions of the inverter. Experimental results show the good performance and effectiveness of the proposed method.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.4
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• pp.535-542
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• 1996

A zero voltage switching (ZVS) three level auxiliary resonant commutated pole inverter (ARCPI) is presented for high power GTO inverters. The concept of ARCP for two level inverter is extended to the three inverter. The proposed auxiliary commutation circuit consists of one resonant inductor and two bi-directional switches, which provides ZVS condition to the main devices without increasing device voltage or current stresses. The auxiliary device operates with zero current switching (ZCS) which enables use of the low cost thyristors. The proposed ARCPI can handle higher voltage and higher power (1-10MVA) comparing to the two level one. Operation and analysis of the ARCPI are illustrated and the features are compared o those of the snubber circuit incorporated three level inverter. Experimental results with 10kW, 4kHz prototype are presented to verify the principle of operation. (author). refs., figs., tab.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.1963-1965
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• 1998

In this paper, a new simplified configuration for a multi-level PWM inverter is proposed. The proposed inverter consists of an auxiliary circuit with one switching device, and 3 phase full-bridge inverter. The proposed inverter, in spite of reduction of the switching devices, offers characteristics similar to the NPC(Neutral - point - clamped)- PWM inverter. Also, since the reduction of the switching devices, the control strategy is simplified. And switching loss is reduced. In addition to, it is possible that reliable DC level voltage than former multi-level inverter. And load power application is same to conventional NPC-PWM inverter. The performance of the system is verified by simulation. In this paper, show the simulation result of the single phase full bridge inverter application.