• Journal of Power Electronics
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• v.16 no.6
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• pp.2076-2084
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• 2016

In this paper, a novel scheme to eliminate common-mode voltage (CMV) is proposed for three-level neutral-point clamped (NPC) inverters. In the proposed scheme, a low-power full-bridge converter is utilized to produce compensatory voltage for CMV, which is injected into an NPC inverter through a single-phase four-winding transformer. With the proposed circuit, the power range for applications is not limited, and the maximum modulation index of the inverter is not reduced. These features are suitable for high-power medium-voltage machine drives. The effectiveness of the proposed method is verified by simulation and experimental results.

• Journal of Power Electronics
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• v.11 no.1
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• pp.21-27
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• 2011

In this paper, an approach to reduce common-mode voltage (CMV) at the output of multilevel inverters using a phase opposition disposed (POD) sinusoidal pulse width modulation (SPWM) technique is proposed. The SPWM technique does not require computations therefore, this technique is easy to implement on-line in digital controllers. A good tradeoff between the quality of the output voltage and the magnitude of the CMV is achieved in this paper. This paper realizes the implementation of a POD-SPWM technique to reduce CMV using a five-level diode clamped inverter for a three phase induction motor. Experimental and simulation results demonstrate the feasibility of the proposed technique.

• Journal of Power Electronics
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• v.19 no.3
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• pp.714-726
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• 2019

This paper proposes a hybrid-boost Modular Multilevel Converter (MMC) for the Medium-Voltage (MV) Variable Speed Drives (VSDs) employed in subsea applications, such as oil and gas recovery. In the presented architecture, a hybrid-boost MMC with a reduced number of semiconductor devices driving a multiphase Induction Machine (IM) is investigated. The stepped output voltage generated by the MMC reduces or eliminates the filtering requirements. Moreover, the boosting capability of the proposed architecture eliminates the need for bulky low-frequency transformers at the converter output terminals. A detailed illustration of the hybrid-boost MMC operation, the expected limitations/constraints, and the voltage balancing technique are presented. A simulation model of the proposed MV hybrid-boost MMC-based five-phase IM drive has been built to investigate the system performance. Finally, a downscaled prototype has been constructed for experimental verification.

• Journal of Power Electronics
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• v.11 no.4
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• pp.512-519
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• 2011

This paper gives a detailed analysis of the direct torque control (DTC) strategy in a five-level drive and proposes a 24-sector switching table. The known problems in low-voltage drives such as bearings currents and an overvoltage phenomenon which leads to premature failure are reviewed and the occurrence of these problems in medium voltage drives has been investigated. Then a solutions to these problems is presented and the switching table to deal with these problems is modified. Simulation and experimental results on a 3kVA prototype confirm the proposed solution. In implementing the above strategy a TMS320F2812 is used.

• Journal of Power Electronics
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• v.16 no.5
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• pp.1725-1734
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• 2016

This paper presents a novel seven-level (7L) voltage source converter for high-power medium-voltage applications. The proposed topology is an H-bridge connection of two nested neutral-point clamped (NNPC) converters and is referred to as an HNNPC converter. This converter exhibits advantageous features, such as operating over a wide range of output voltages, particularly for 10-15 kV applications, without the need to connect power semiconductors in series; high-quality output voltage; and fewer components relative to other classic seven-level topologies. A novel sinusoidal pulse width modulation technique is also developed for the proposed 7L-HNNPC converter to control flying capacitor voltages. One of the main features of the control strategy is the independent application of control to each arm of the converter to significantly reduce the complexity of the controller. The performance of the proposed converter is studied under different operating conditions via MATLAB/Simulink simulation, and its feasibility is evaluated experimentally on a scaled-down prototype converter.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.31-35
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• 2001

IGCTs have established themselves as the power semiconductor of choice at medium voltage levels within the last few years because of their low conduction and switching losses. The trade-off between these losses can be adjusted by various lifetime control techniques and the growing demand for these devices is driving the need for standard types to cover such applications as Static Circuit Breakers (low on-state) and Medium Voltage Drives (low switching losses). The additional demands of Traction (low operating temperatures) and Current Source Inverters (symmetric blocking) would normally result in conflicting demands on the semiconductor. This paper will outline how a range of power devices can meet these needs with a limited number of wafers and gate units. Some of the key differences between IGCTs and IGBTs will be explained and the outlook for device improvements will be discussed.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.288-289
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• 2018

In this paper, the coupled inductor scheme instead of noncoupled inductors is suggested to reduce the dimension, weight and cost of the magnetic core. The simulation results have verified the effectiveness of the flying-capacitor MMC with coupled inductors and its control method for medium-voltage induction motor drives at low-speed operation.

• Journal of Power Electronics
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• v.17 no.4
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• pp.923-932
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• 2017

This paper proposes a novel scheme which can compensate the common-mode voltage (CMV) for five-level active neutralpoint clamped (5L-ANPC) inverters, which is based on modifying the space vector pulse width modulation (SVPWM) and adding an auxiliary leg to the inverter. For the modified SVPWM, only the 55 voltage vectors producing low CMV values among the 125 possible voltage vectors are utilized, which varies over the three voltage levels of $-V_{dc}/12$, 0 V, and $V_{dc}/12$. In addition, the compensating voltage, which is injected into the 5L-ANPC inverter system to cancel the remaining CVM through a common-mode transformer (CMT) is generated by the additional NPC leg. By the proposed method, the CMV of the inverter is fully eliminated, while the utilization of the DC-link voltage is not decreased at all. Furthermore, all of the DC-link and flying capacitor voltages of the inverter are well controlled. Simulation and experimental results have verified the validity of the proposed scheme.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.2
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• pp.99-105
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• 2014

This paper proposes the reliability improvement of H-Bridge Multi-level (HBM) inverter. This reliability can be implemented through modularization of power circuit, distribution of controller, duplication of controller and communication, and continuous operation method in case of power cell failure for driving medium-voltage & high-power induction motor. It is shown that the modularization and expansion characteristics of the HBM inverter are improved since the individual inverter modules operate more independently when using the proposed concept. Also the fault tolerance is increased by using power cell bypass. The proposed design and control methods are described in detail and the validity of the proposed system is verified experimentally in various industrial fields.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.398-399
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• 2019

본 논문은 LS산전 고압인버터의 국내외 현장 전용화 사례에 대해 기술한다. 고압인버터는 대용량 고전압 전동기를 구비한 중요부하에 주로 적용되며 단독운전보다는 다수의 고압인버터가 연동 운전하는 현장에 설치되는 경우가 많다. 이러한 현장에는 표준제품이 아닌 전용화 기능을 포함한 제품이 출하가 된다. 자사 LS MVD는 각종 산업설비와 국책연구기관의 시험설비 그리고 발전소 수처리 시설 등 국가기간시설에 많이 적용이 되며 매년 70여대 이상의 MVD가 국내외 전동기 부하에 신규로 설치되어 운용되고 있다. 본 논문에서는 주목할만한 현장의 전용화 사례에 대해 설명하여 향후 고압인버터를 적용하고자 하는 고객이나 고압인버터에 관심이 있는 엔지니어에게 고압인버터에 대한 이해도를 높이고자 한다.