• 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 Power Electronics
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• v.16 no.4
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• pp.1316-1323
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• 2016

Multilevel inverters (MLIs) have been preferred over conventional two-level inverters due to their inherent properties such as reduced harmonic distortion, lower electromagnetic interference, minimal common mode voltage, ability to synthesize medium/high voltage from low voltage sources, etc. On the other hand, they suffer from an increased number of switching devices, complex gate pulse generation, etc. This paper develops an ingenious symmetrical MLI topology, which consumes lesser component count. The proposed level dependent sources concoction multilevel inverter (LDSCMLI) is basically a multilevel dc link MLI (MLDCMLI), which first synthesizes a stepped dc link voltage using a sources concoction module and then realizes the ac waveform through a conventional H-bridge. Seven level and eleven level versions of the proposed topology are simulated in MATLAB r2010b and prototypes are constructed to validate the performance. The proposed topology requires lesser components compared to recent component reduced MLI topologies and the classical topologies. In addition, it requires fewer carrier signals and gate driver circuits.

• Journal of Electrical Engineering and Technology
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• v.8 no.5
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• pp.1122-1130
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• 2013

This paper proposes a new design for quick battery charger systems for electric vehicles that consists of a three-phase inverter and a full-bridge converter which use the phase-shift method. The 3-phase inverter controls the input and DC-link voltage by use of a current controller and a voltage controller. The full-bridge converter transfers the DC-link voltage to a fixed output voltage. Designs for the output-side converter and controller for improved performance are proposed in this paper. Design schemes for the filter and controller of an input-side inverter are also presented. Furthermore, the paper proposes a compensation method for the offset current that is caused by switch failure and circuit problems. Simulations and experiments have been performed on a 50kW-battery charger system that is suitable for vehicles. The presented results verify the validity of the proposed method and the superiority of the system over conventional methods.

• Proceedings of the KIEE Conference
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• 2003.07e
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• pp.166-170
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• 2003

This paper deals with the power loss analysis of voltage source type space voltage vector modulated soft switching inverter, and proposed the new voltage vector correction principle during one sampling period on realize high quality cutput voltage waveforms for two soft-swiching approches. The operating pinciple of a single active auxiliary resonant DC link snubber circuit is described. Moreover, the effectiveness of soft switching inverter operating under the corrected voltage pattern is proved on the basis of simulation and experimental results.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1995.10a
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• pp.101-104
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• 1995

The linear control of DC Link voltage in PWM inverter is very importent to estimate the goodness of PWM method. In motor control system, for the maximum torque on full region operating, the whole of DC Link voltage region must be used. 3 phase sinusoidal PWM inverter has a low efficienty at the using of output voltage. according to make better the efficiency, new improved PWM control method is proposed. The results of experimentation and simulation are included to verify the validity of this method.

• Journal of Power Electronics
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• v.6 no.1
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• pp.52-66
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• 2006

This paper proposes a wind energy conversion system connected to a grid using a self-excited induction generator (SEIG) based on the maximum power point tracking (MPPT) control scheme. The induction generator (IG) is controlled by the MPPT below the base speed and the maximum energy can be captured from the wind turbine. Therefore, the stator currents of the IG are optimally controlled using the indirect field orientation control (IFOC) according to the generator speed in order to maximize the generated power from the wind turbine. The SEIG feeds a (CRPWM) converter which regulates the DC-link voltage at a constant value where the speed of the IG is varied. Based on the IG d-q axes dynamic model in the synchronous reference frame at field orientation, high-performance synchronous current controllers with satisfactory performance are designed and analyzed. Utilizing these current controllers and IFOC, a fast dynamic response and low current harmonic distortion are attained. The regulated DC-link voltage feeds a grid connected CRPWM inverter. By using the virtual flux orientation control and the synchronous frame current regulators for the grid connected CRPWM inverter, a fast current response, low harmonic distortion and unity power factor are achieved. The complete system has been simulated with different wind velocities. The simulation results are presented to illustrate the effectiveness of the proposed MPPT control scheme for a wind energy system. In the simulation results, the d-q axes current controllers and DC-link voltage controller give prominent dynamic response in command tracking and load regulation characteristics.

• Proceedings of the KIPE Conference
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• 2013.11a
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• pp.109-110
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• 2013

3-level 인버터에서 DC_Link와 각 leg의 스위치 간 라인에 존재하는 Stray inductance로 인해 스위칭 시 Voltage spike가 발생하게 된다. 3-level 인버터는 고전압, 대전력에서 주로 사용되기 때문에 Voltage spike로 인해 전력반도체 스위치에 순간적으로 큰 전압이 인가되어 정격 이하의 운전에서도 스위치가 소손되어 전체 시스템의 고장을 초래할 수 있다. 이와 같은 사고를 방지하기 위해 본 논문에서는 DC_Link 커패시터를 분할로 구성하여 Stray inductance를 균일하게 하고 전반적으로 최소화 하였다. Stray inductance는 Double Pulse Test 시뮬레이션 및 실험으로 확인하였다.

• Proceedings of the KIPE Conference
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• 1997.07a
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• pp.14-20
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• 1997

Due to several advantages of Pulse Width Modulated(PWM) Converter, such as unity power factor with low-harmonics and energy regeneration, PWM converter has been widely used in industrial application. In every application of energy conversion equipment, the design and implementation must be carried out considering performance and cost. High quality with low cost is the best choice for energy conversion equipment. High dc link voltage can reduce inverter and motor side losses and system dimension compare to low dc link voltage. Analog controller can make PWM converter cheaper without considerable degradation of the performance than digital controller. This paper shows the simplified analog controller-for 600V dc link voltage using stationary reference frame control and the simulation results.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.1
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• pp.110-116
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• 2013

This paper proposes a current ripple reduction method to improve the control performance of B4 type inverter that is studied for cost-effective drive systems. B4 inverters employ only four switches and they have a center-tapped connection between the split dc-link capacitors and one phase of a three-phase motor or load. In the B4 topology, unbalanced three-phase voltages will be generated due to the dc-link voltage ripple. To solve this problem, this paper presents a voltage distortion compensation method that adjusts the voltage reference with the consideration of dc-link voltage ripple. The validity of the proposed method is verified by simulation and excremental results with an induction machine.

• Proceedings of the KIPE Conference
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• 2020.08a
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• pp.407-408
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• 2020

본 논문은 SiC-MOSFET 기반 전기차용 인버터의 DC-Link 캐패시터 전기용량을 선정하는 방법에 대해 연구하였다. 인버터 시스템에 주로 사용되는 DC-Link 캐패시터는 안정적인 전원 및 고주파 전류 공급 등의 중요한 역할을 한다. 그러나 인버터가 고용량일수록 캐패시터 사이즈가 커지고 무게가 늘어나는 문제가 발생한다. 따라서, 차세대 전력 반도체 소자로 각광 받는 SiC-MOSFET의 높은 동작 주파수의 특성을 활용하여 캐패시터 소형화를 실현시켰다. 또한, PSIM 시뮬레이션을 통해 제안하는 연구의 타당성을 검증하고 Si-IGBT 인버터와 비교하여 그 효과를 입증하였다.