• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 하계학술대회 논문집
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• pp.346-350
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• 1990

This paper proposes a novel current control strategy for current regulated VSI-PWM transistor inverter. The conventional hysteresis control method has good dynamic responses. But the switching frequencies are high because it does not optimize switching patterns. Proposed current control strategy can optimize switching patterns. As regulator, three level comparators are used. The outputs of the comparators select appropriate inverter output voltage vectors via switching table stored in EPROM. The simulation and exparimental results in comparison to contentional hysteresis strategy are presented and discussed.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권8호
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• pp.390-396
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• 2002

This paper Presents to choose number of RGB LED through optical special quality analysis of RGB LED samples and to produce ratio of RGB LED for a stable color variation and white light. Also, it is to design of a simple switching circuit using some resistances and switching transistors that is able to operate each 16 RGB LED stably, and switching control circuit base on a microcontroller that would be suitable for colors variation patterns control more than about 64 patterns and colors variation more than about 100,000 colors using ON/OFF and Duty control.

• Journal of Power Electronics
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• 제16권2호
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• pp.542-552
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• 2016

Central 60° synchronous modulation is an easy pulse-width modulation (PWM) method to implement for the traction inverters of urban rail trains at a very low switching frequency. Unfortunately, its switching patterns are determined by a Fourier analysis of assumed steady-state voltages. As a result, its transient responses are not very good with over-currents and high instantaneous torque pulses. In the proposed solution, the switching patterns of the conventional central 60° modulation are modified according to the dynamic error between the target and actual stator flux. Then, the specific trajectory of the stator flux and current vector can be guaranteed, which leads to better system transients. In addition, stator flux control is introduced to get smooth mode switching between the central 60° modulation and the other PWMs in this paper. A detailed flow chart of the control signal transmission is given. The target flux is obtained by an integral of the target voltage. The actual PMSM flux is estimated by a minimum order flux state observer based on the extended flux model. Based on a two-level inverter model, improved rules in the α-β stationary coordinate system and equations of the switching patterns amendment are proposed. The proposed method is verified by simulation and experimental results.

• Journal of Power Electronics
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• 제13권2호
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• pp.232-242
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• 2013

To obtain phase currents information in AC drives, shunt sensing technology is known to show great performance in cost-effectiveness and therefore it is widely used in low cost applications. However, shunt sensing methods are unable to acquire phase currents in certain operation conditions. This paper deals with the derivation of the boundary conditions for phase current reconstruction in three-shunt sensing inverters and proposes a voltage injection method to expand the measurable areas. As the boundary conditions are deeply dependent on the switching patterns, they are typically analyzed on the voltage vector plane for space vector pulse width modulation (SVPWM) and discontinuous pulse width modulation (DPWM). In the proposed method, the voltage injection and its compensation are conducted within one sampling period. This guarantees fast current reconstruction and the injected voltage is decided so as to minimize the current ripple. In addition to the voltage injection method, a sampling point shifting method is also introduced to improve the boundary conditions. Simulation and experimental results are presented to verify the boundary condition derivation and the effectiveness of the proposed voltage injection method.

• 전력전자학회논문지
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• 제17권4호
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• pp.291-297
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• 2012

Recently, Switching devices become cheaper, depending on the multi-level inverters are considered as the power-conversion systems for high-power and power-quality demanding applications. The multi-level inverters can reduce the THD(Total Harmonic Distortion) as the output which is similar sinusoidal waveform by synthesizing several capacitor DC voltages. However it has some disadvantages such as increased number of components, complex PWM control method. Therefore, this paper is proposed the new multi-level inverter topology using an new H-bridge output stage with a bidirectional auxiliary switch. The proposed topology is the 4-level 3-phase PWM inverter with less switching part than conventional multi-level inverters and reactive power control possible. In order to understand the new multi-level inverter, topology analysis and switching patterns and modes according to the current loop are described in this paper. The proposed multi-level inverter topology is validated through PSIM simulation and the experimental results are provided from a prototype.

• 전력전자학회논문지
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• 제23권3호
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• pp.190-198
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• 2018

This paper proposes a nonisolated, bidirectional, soft-switching DC - DC converter with PWM plus phase shift (PPS) control. The proposed converter has an input-parallel/output-series configuration and can achieve the interleaving effect and high voltage gains, resulting in decreased voltage ratings in all related devices. The proposed converter can operate under zero-voltage switching (ZVS) conditions for all switches in continuous conduction mode. The power flow of the proposed converter can be controlled by changing the phase shift angle, and the duty is controlled to balance the voltage of four high voltage side capacitors. The PPS control device of the proposed converter is simple in structure and presents symmetrical switching patterns under a bidirectional power flow. The PPS control also ensures ZVS during charging and discharging at all loads and equalizes the voltage ratings of the output capacitors and switches. To verify the validity of the proposed converter, an experimental investigation of a 2 kW prototype is performed in both charging and discharging modes under different load conditions and a bidirectional power flow.

• 한국조명전기설비학회지:조명전기설비
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• 제2권2호
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• pp.64-70
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• 1988

교류 전동기의 가변속 구동에 있어서, 가변전압, 가변주파수 방식의 PWN 인버터가 널리 사용되고 있다. 본 연구에서는 3상 PWN 인버터의 출력 파형에 있어서 특정고조파제거를 위한 방법이 소개되며 그 타당성을 입증하기 위해 실험결과는 시뮬레이션 결과와 비교·검토된다. 제안된 PWN 방식은 유도 전동기뿐만 아니라 전압 조정기, UPS 등에도 사용 가능하다.

• Toxicological Research
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• 제11권1호
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• pp.9-14
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• 1995

The immune system is partially under the control of the sympathetic and parasymphathetic nervous systems through the regulatory feedback loop. Methamphetamine (MA) is a neurotoxic chemical which affects the neurotransmitter system. The objective of this study was to investigate the immunotoxic effect of MA on the major immune target organ and lymphocyte proliferation to the various mitogens. Female Balb/C mice, 15 to 20 g, were injected subcutaneously with 0, 0.5, or 5 mg MA/kg for 14 consecutive days. In MA treated mice, the body weight gain and relative spleen and thymus weight were decreased in doserelated manner. Histopathologically, there was a paucity of lymphold follicles and germinal centers in the spleen, and thymic cortical atrophy with lymphophagocytosis was prominent. Apoptosis also occurred in germinal centers of spleen and thymic cortex. The threshold and peak of lymphocyte proliferation at various concentration of mitogens showed similar patterns. However, the response to lipopolysaccaride (LPS) and pokeweed mitogen (PWM) in the 5 mg MA/kg treated group showed threshold and peak proliferation at high concentration of mitogens (25${\mu}g$ LPS/ml for MA vs 15${\mu}g$ LPS/ml for control; 60${\mu}g$ PWM/ml for MA vs 45${\mu}g$ PWM/ml for control), which suggest that MA impairs T cell dependent-B cell function. This preliminary study indicated that MA affected the lymphold organs and immune function.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1997년도 전력전자학술대회 논문집
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• pp.352-356
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• 1997

This paper present the design of a novel neural-network (NN) based pulse-width modulation (PWM) techniques for a three-level power converter of electric trains along with nonlinear mapping of essential switching patterns and fault tolerance, which are inherent characteristics of NNs. Considering the importance of safety, power factor and harmonics of electric train power converters, two-level type and three-level type of power converters using NNs are precisely investigated and compared in computer simulation. A computer simulation shows that a new current control scheme provides an improved performance over a fixed-band hysteresis current control in many aspects.

• Journal of the korean society of oceanography
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• 제35권3호
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• pp.153-157
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• 2000

Four different FITC-conjugated lectins were used to visually evaluate lectin binding activity by optical staining quality using confocal laser scanning microscopy (CLSM) of Cochzodinium polykrikoides in nature (wild type) and culture (cultured type). Cells from the field and cultures treated with ConA fluoresced only at the outer cell wall, and the abundance and distribution of the fluorescent signal were similar. Treatment with PWM and HPA did not elicit fluorescence at the cell surface, but the wild type exposed to HPA showed greater binding than did the cultured cells, possibly due to greater concentrations of glucosamine. The wild type cells treated with LBL lectin showed a strong green fluorescence on the cell surface, whereas cultured cells did not. Signal intensity and abundance were greater than for any other lectins tested in this study. These results suggest that wild type and cultured type are significantly different based on surface sugar production. In particular, the wild type cells apear richer in galactosamine-like moieties. Neither glucose nor mannose-like moieties were present in either wild types or cultured cells.