• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.1
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• pp.65-73
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• 2002

This paper proposes a new carrier-based PWM method to solve the most serious problem of flying capacitor multi-level inverter that is the unbalance of capacitor voltages. The voltage unbalance occurs due to the difference of each capacitor's charging and discharging time applied to Flying Capacitor Inverter. New solution controls the variation of capacitor voltages into the mean '0'during some period by means of new carriers using the leg voltage redundancy in the flying capacitor inverter. The solution can be easily expanded to the multi-level inverter. The leg voltage redundancy in the new method makes the switching loss of device equals to the conduction loss of device. This paper will examine the unbalance of capacitor voltage and the conventional theory of self-balance using Phase-shifted carrier. And then the new method that is suitable to the flying capacitor inverter will be explained.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.1334-1339
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• 2004

This paper proposes transformerless power conversion system consisting of a single-phase diode rectifier and a shunt hybrid filter for the electric-railway system. The hybrid filter consists of a single tuned LC filter per a phase and a low-rated NPC type multi-level inverter. Compared with conventional active filters. Transformers are not used. Also, LC filter works as not only a harmonic filter tuned at the 5th harmonic frequency but also a switching-ripple filter. The rating of the active filter can be decreased by using a NPC type multi-level inverter. The simulation results confirm the validity of the system.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.1427-1432
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• 2004

This paper proposes transformerless power conversion system consisting of a single-phase diode rectifier and a shunt hybrid filter for the electric-railway system. The hybrid filter consists of a single tuned LC filter per a phase and a low-rated NPC type multi-level inverter. Compared with conventional active filters. Transformers are not used. Also, LC filter works as not only a harmonic filter tuned at the 5th harmonic frequency but also a switching-ripple filter. The rating of the active filter can be decreased by using a NPC type multi-level inverter. The simulation results confirm the validity of the system

• 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.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.239-242
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• 2001

Energy recovery in the regenerative region is very important when SRM(Switched Reluctance Motor) is used in traction drive. This is because that to reduce energy toss during mechanical breaking and/or to have a high efficiency drive during breaking. To control excitation voltage in motor operation and regenerative voltage in the generator operation in the SRM, multi-level voltage control is effective. This paper proposes multi-level inverter which is useful for motoring and regenerative operation in SRM. The proposed method is verified by experiment.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.12
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• pp.624-631
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• 2003

This paper presents a simple carrier symmetric method for the voltage balance of flying capacitors in FCMLI(flying capacitor multi-level inverter). To achieve the voltage balance of flying capacitors, the utilization of each carrier must be balanced during a half-cycle of the switching period such as PSPWM(Phase-Shifted PWM). However, the CRPWM(Carrier Redistribution PWM) method causes the fluctuation of flying capacitor voltages because the balanced utilization of carriers is not achieved. Moreover, it does not consider that the load current change has an influence on flying capacitor voltages by assuming that the current flows into the load. To overcome the drawbacks of CRPWM, it is modified by the technique that carriers of each band are disposed symmetrically at every fundamental period. Firstly, the CRPWM method is reviewed and the theory on voltage balance of flying capacitors is analyzed. The proposed method is introduced and is verified through the experiment result.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.3
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• pp.296-301
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• 2005

This paper proposing the use of the Instantaneous reactive power method as a harmonic detection method for a single phase active filter system. This method is to detect harmonic components through d-q frame approach. The conventional use of d-q frame approach for a 3-phase system Is extended to the single phase system. The proposed system uses a multi-level inverter for harmonic compensation and the inverter is connected to the input side without using transformers. The proposed algorithm is verified by simulation and experiment.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.5
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• pp.101-109
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• 2009

In this paper, a new method, cascade 3 phase IHCML(Isolated H-bridge Cascade Multi-Level) inverter and a control method is proposed by using two 3-phase transformers that have respectively different transformation rates. Vector control technique in which the highest proximity vector has been used is also put into use. With this process, the switching frequency is almost identical with the output fundamental frequency, which makes less switching loss, and the switching frequency of the small volume of the H-bridge that is in charge of small power is highly controlled, which improves the quality of the output voltage.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.2
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• pp.179-183
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• 2013

This paper report on experimental results of 5-level inverter by DC divided link voltage. We have alreday reported that DC divided link valtage comes to be able to reduse harmonic of out line voltage. So we tested whether DC divided link voltage can reduce harmonics in experimental setup. This paper shows simulation results and experimental results. And we confirmed that DC divided link voltage can also apply in experimental setup.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.585-587
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• 1996

A simple regenerative snubber structure is proposed, which is applicable to multi-level inverter with series-connected GTOs for high power applications. The novel snubber structure can solve large energy loss problems and guarantee safe operation of power converter can be achieved. The proposed new snubber has the potential of high performance and high reliability and is particularly suitable to high power and multi-level application with series connected power devices. The snubber voltage and current waveforms are analized and shown the simulation and experimental results for a GTO 3-level inverter circuit with inductive load.