• Journal of the Semiconductor & Display Technology
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• v.17 no.3
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• pp.90-94
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• 2018

In this paper, we applied a three-level T-type inverter with the one more voltage level than two-level inverter. However, the three-level T-type inverter has a systematic problem with voltage unbalances. So neutral point control is essential. Therefore, the voltage unbalance problem of the three - phase inverter was confirmed to be controlled within 5V using the neutral point control algorithm in charge and discharge mode. In addition, total harmonic distortion was reduced in three phases (u phase, v phase, w phase) when neutral point control was performed in charging mode and also in three phases (u phase, v phase, w phase) in discharge mode. In this paper suggests a neutral point control algorithm to solve the voltage unbalance of a three-level T-type inverter, and shows the improvement of the performance of the proposed algorithm through experiment.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.326-332
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• 2018

In this paper, the design process and the control method of the power conversion system (PCS) that consists of a bidirectional DC-DC converter and a 3-level T-type inverter for an energy storage system is presented. Especially the design method of the output LCL filter for a 3-lvel T-type inverter without complex mathematical process are proposed. The validity of the control method and design process in this paper are verified through simulation and experimental analysis.

• Journal of the Semiconductor & Display Technology
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• v.13 no.4
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• pp.43-48
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• 2014

Two-level inverter has some disadvantages like high harmonics contained in the output current, efficiency limit and stress to switching device as IGBT and FET. Many researches have reported multi-level inverter to complement two-level inverter of problems. In this paper, we suggest MPPT algorithm of multi-string three-level solar inverter that considered nowadays. We added midpoint controller in order to implement the MPPT algorithm because the three-level inverter has to need midpoint controller and procured the stability of direct current link. We verify the superiority of multi-string T-Type inverter and the algorithm we suggested with solar irradiance variation experiment and MPPT efficiency measurement. The MPPT efficiency was confirmed with a high efficiency more than 99.97%.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.2
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• pp.311-318
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• 2016

This paper is a study on the neutral point voltage balancing of the three-phase 3-level T-type inverter using the predictive control techniques. Recently, multi-level inverter has been attracting attention as the advantages such as efficiency improving and harmonic reduction. Especially, the T-type inverter topology is advantageous in low DC-link voltage. However, in case of the prediction control, it takes a lot of time, because there exist 27 voltage vectors and it has to be calculated according to the respective voltage vectors. Therefore, in this paper, we propose a method to implement predictive control techniques while reducing the operation time. In order to reduce the operation time, the predictive control is implemented by using the minimum voltage vector except for the unnecessary voltage vector. The result of the implemented predictive control is added to the SPWM by using the offset voltage. It was verified through simulation and experimental results.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.263-269
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• 2018

In this study, a selective inverter operation between a 2-level voltage source converter (VSC) and a 3-level T-type VSC (3LT VSC) is proposed to improve the efficiency of a 3LT VSC. The 3LT VSC topology, except for its neutral-point switches, has similar operations as that of the 2-level VSC. If an operation mode is changed according to efficiency, the efficiency can be improved because efficiencies of each methods are depending on current and MI (Modulation Index). The proposed method calculates the power losses of the two topologies and operates as the having lower losses. To calculate the losses, the switching and conduction losses based on the operation mode of each topology were analyzed. The controller determined the operation mode of the 2- or 3-level VSC based on the power loss calculated during every cycle. The validity of the proposed control scheme was investigated through simulation and experiments. The waveform and average efficiency of each method were compared.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.2
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• pp.173-183
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• 2014

In this paper, an analysis of power losses for the three-level T-type and neutral-point clamped (NPC) PWM inverters is presented, in which the conduction and switching losses of semiconductor devices of the inverters are taken into account. In the inverter operation, the conduction loss depends on the modulation index (MI) and power factor (PF), whereas the switching loss depends on the switching frequency. Power losses for the T-type and NPC inverters are analyzed and calculated at the different operating points of MI, PF and the switching frequency, in which the four different models of semiconductor devices are adopted. In the case of lower MI, the NPC-type is more efficient than the T-type, and vice versa. The validity of the power loss analysis has been verified by the simulation results.

• Journal of Power Electronics
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• v.19 no.3
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• pp.702-713
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• 2019

Multilevel Inverters (MLIs) are widely used in medium voltage applications due to their various advantages. In addition, there are numerous types of MLIs for such applications. However, the diode-less 3-level (3L) T-type Neutral Point Clamped (NPC) MLI is the most advantageous due to its low conduction losses and high potential efficiency. The power circuit of a 3L T-type NPC is derived by the conventional two level inverter by a slight modification. In order to explore the MLI performance for various Pulse Width Modulation (PWM) schemes, this paper examines the operation of a 3L (five level line to line) T-type NPC MLI for various types of Multi-Carriers Pulse Width Modulation (MCPWM) schemes. These PWM schemes are compared in terms of their voltage profile, total harmonic distortion (THD) and conduction losses. In addition, a 3L T-type NPC MLI is also compared with the conventional NPC in terms of number of switches, clamping diodes, main diodes and capacitors. Moreover, the capacitor-balancing problem is also investigated using the Neutral Point Fluctuation (NPF) method with all of the MCPWM schemes. A 1kW 3L T-type NPC MLI is simulated in MATLAB/Simulink and implemented experimentally and its performance is tested with a 1HP induction motor. The results indicate that the 3L T-type NPC MLI has better performance than conventional NPC MLIs.

• Proceedings of the KIPE Conference
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• 2014.11a
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• pp.143-144
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• 2014

본 논문에서는 NPC(Neutral Point Clamped) 및 T-type IGBT 모듈을 이용하여 3상 3-레벨 인버터를 구성하고, 인버터에서 발생되어지는 도통손실과 스위칭 손실을 PSIM의 Thermal Module을 사용하여 확인한다. 또한 토폴로지 상의 차이에 의해 발생되어지는 스위치 손실을 비교 하며, 시뮬레이션에 적용한 파라미터 값들을 수식에 직접 적용하여 손실에 영향을 미치는 파라미터를 확인하고, 각 파라미터의 값의 변화가 주어진 조건에서 전체 손실에 미치는 영향을 확인한다.

• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.421-422
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• 2013

본 논문에서는 3-레벨의 NPC(Neutral Point Clamped) VSC와 T-type VSC를 시뮬레이션용 열 모델링 기법을 이용하여 스위칭과 도통 손실을 비교 분석하였다. 두 가지 토폴로지의 인버터동작과 회생동작에서의 주파수에 따른 효율을 시뮬레이션을 통하여 고찰 하였다.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.296-297
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• 2018

본 논문은 3상 T-type 3-레벨 인버터의 모델예측제어에 관한 연구이다. 모델예측제어는 시스템의 모델링을 통한 최적의 성능을 제공하는 제어기법으로 PI 제어보다 빠른 동특성을 갖지만, 정확한 파라미터 값이 요구된다. 본 논문에서는 시스템 파라미터 오차가 3상 T-type 3-레벨 인버터의 예측제어에서 어떤 영향을 주는지 알아보고 출력 파형을 분석한다.