• Journal of Power Electronics
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• v.15 no.5
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• pp.1207-1216
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• 2015

In order to suppress the low frequency oscillation of the neutral-point voltage for three-level inverters, this paper proposes a new discontinuous pulse width modulation (DPWM) control method. The conventional sinusoidal pulse width modulation (SPWM) control has no effect on balancing the neutral-point voltage. Based on the basic control principle of DPWM, the relationship between the reference space voltage vector and the neutral-point current is analyzed. The proposed method suppresses the low frequency oscillation of the neutral-point voltage by keeping the switches of a certain phase no switching in one carrier cycle. So the operating time of the positive and negative small vectors is equal. Comparing with the conventional SPWM control method, the proposed DPWM control method suppresses the low frequency oscillation of the neutral-point voltage, decreases the output waveform harmonics, and increases both the output waveform quality and the system efficiency. An experiment has been realized by a neutral-point clamped (NPC) three-level inverter prototype based on STM32F407-CPLD. The experimental results verify the correctness of the theoretical analysis and the effectiveness of the proposed DPWM method.

• Korean Journal of Computational Design and Engineering
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• v.13 no.4
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• pp.243-254
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• 2008

As modular production becoming increasingly widespread in globalized manufacturing industries, sub modules or parts of the final product are being provided by many suppliers. Some part suppliers design their own products for themselves. In some cases, part suppliers provide the same type of product to multiple OEM companies. Because all part suppliers and OEM companies typically cannot use the same CAD system, engineering change in the CAD model of one company cannot be directly propagated to related CAD models of other companies. Even if two companies use the same CAD system, it may be difficult to share their CAD model owing to corporate security policy. In this paper, a neutral reference model that consists of a neutral skeleton model and an external reference data model is proposed as a new medium for the sharing and propagation of engineering change information among collaborating companies.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.918-923
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• 2011

On AC railway systems, the neutral sections are installed in front of substations and sectioning posts in order to avoid crash between power that have differing phases. In case railway vehicles pass through these neutral sections, it is necessary for them to switch to coasting driving by notch-off. This may reduce speed of the vehicles, resulting lowered train operation efficiency. The usage of automatic power switching systems makes it possible to pass neutral sections at notch-on, enhancing operation efficiency so that it is appropriate for high-speed railway applications. This paper introduces a simulator that assesses efficiency of automatic power switching systems in neutral sections. The is composed of a power supply system, electric railway vehicles, thyristor switches, and traction motors.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.477-477
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• 2012

The effects of argon neutral beam (NB) energy on the amorphous carbon (a-C) films were investigated, while the a-C films were deposited by neutral particle beam assisted sputtering (NBAS) system. The deposition characteristics of these films were studied as a function of NB energy (or reflector bias voltage). The film structures were investigated by Raman spectroscopy. The hardness was measured by nano-indentation tests and the optical band gap was measured by UV-visible spectroscopy.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.11
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• pp.2236-2241
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• 2009

In this study, the electron behavior was investigated numerically in order to obtain guidelines for design and operation of a new plasma source by a magnetic neutral loop discharge (NLD). The optimum plasma production was investigated by using a 3-dimensional simulation model which enables the electron behavior calculation from source region to downstream region. The results showed that the high-density plasma produced around the magnetic neutral loop (NL) is transferred from the NL region to the downstream region along magnetic force lines. Also the avaraged electron energy is increased with the normalized RF electric field (F), which can be used to characterize the plasma production efficiency of NLD system. Considering the relation between F and plasma production, in-depth plasma control can be achieved at a given specific process condition.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.9
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• pp.59-70
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• 2020

Three-dimensional (3D) design data is used for various purposes throughout the life cycle of a plant construction project. Plant 3D CAD systems support 3D modeling based on specs-catalogs, which contain data that are used for different purposes such as design, procurement, production, and handover. Therefore, it is important to share the spec-catalog data in the 3D design model with other application systems. Sharing this data thus requires a system that extracts spec-catalog data from plant 3D CAD systems and converts them into neutral model data. In this paper, we analyze equipment spec-catalog data of plant 3D CAD systems and, based on these analyses, define the data structure for neutral spec-catalog data. We subsequently propose a procedure that translates native spec-catalog data to neutral model data and develop a prototype system that performs this operation. The proposed method is then experimentally validated for the test spec-catalog data.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.4
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• pp.181-187
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• 2004

With the proliferation of nonlinear loads, high neutral harmonic currents in three-phase four-wire distribution system have been observed. It has been known that the ground impedance has an effect on the neutral currents of a system which operates with harmonics present. On-site measurements of harmonic currents and voltages according to the fall-of-potential method under case study system were made and the ground impedance modeling using the pattern search method for the harmonic analysis was developed The ground impedance model obtained by the proposed method was compared with the frequency characteristics by field tests and has shown appropriate results, and would be applicable to evaluate the harmonic and transient response characteristics of the ground system.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.535-536
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• 2011

This paper studies the validity about a joint operation of neutral wire and overhead grounding wire in combined distribution systems. The overhead grounding wire and neutral wire are currently installed separately and grounded by common. However there is no any ineffectiveness or electrical problem in case of the proposed system, such system can be operated at real distribution system. Therefore this paper describes the suitability of a joint operation through lightning surge analysis on combined distribution systems and analyzes the optimal position of lightning arrester on joint operation of neutral wire and overhead grounding wire. Lightning surge analysis is carried out by EMTP/ATPDraw to obtain the overvoltage of overhead line and underground cable in various conditions such as location and current types of lightning stroke. Over voltage gained by the analysis show that the insulation strength of the joint operation case is not stable compare with the current operation case.

• Proceedings of the KIEE Conference
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• summer
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• pp.369-371
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• 2004

With the proliferation of nonlinear loads, high neutral harmonic currents in three-phase four-wire distribution system have been observed. It has been. known that the ground impedance has an effect on the neutral currents of a system which operates with harmonics present. On-site measurements of harmonic currents and voltages according to the fell-of-potential method under case study system were made and the ground impedance modeling using the pattern search method for the harmonic analysis was developed. The ground impedance model obtained by the proposed method was compared with the frequency characteristics by field tests and has shown appropriate results, and would be applicable to evaluate the harmonic and transient response characteristics of the ground system.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.3
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• pp.120-127
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• 2004

With the proliferation of nonlinear loads such as switching mode power supplies, high neurtral harmonic currents in three-phase four-wire distribution system have been observed. It has been known that the grounded impedance has an effect on the neutral current of a system which operates with harmonics present since the neutral conductor is grounded. On-site measurements of harmonic currents and voltages were made and the corresponding equivalent circuit was developed. The circuit model under study was simulated numerically and graphically through the use of the software MATLAB. Simulation results verifying the relationship between the neutral harmonic current and ground impedance are presented.