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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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The Transactions of the Korean Institute of Power Electronics
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The Korean Institute of Power Electronics
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Volume & Issues
Volume 21, Issue 4 - Aug 2016
Volume 21, Issue 3 - Jun 2016
Volume 21, Issue 2 - Apr 2016
Volume 21, Issue 1 - Feb 2016
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Characteristics Analysis of Segmental Rotor Type 3-Phase SRMs
Xu, Zhenyao ; Lee, Dong-Hee ; Ahn, Jin-Woo ;
The Transactions of the Korean Institute of Power Electronics, volume 21, issue 1, 2016, Pages 1~9
DOI : 10.6113/TKPE.2016.21.1.1
In this study, two types of switched reluctance motors (SRMs) with segmental rotors are presented in detail. The first is a 6/5 segmental rotor type, whereas the second is a 12/8 segmental rotor type. Both motor types have the same stator, rotor, and winding configurations. The stator is constructed with special stator poles, namely, exclusively designed exciting and auxiliary poles. The rotor is constructed from a series of discrete segments, each of which is embedded into the nonmagnetic isolator. The windings are only wound on the exciting poles, and no winding is wound on the auxiliary poles. Given these configurations, short flux paths and high flux-linkage utilization rate are achieved in the proposed motors, which may reduce the magnetomotive force requirement and increase the electrical utilization of a machine. To verify the effectiveness of the proposed motors, their characteristics, such as magnetic flux distribution, flux-linkage, torque, radial force, and efficiency, are analyzed and compared with those of a conventional 12/8 SRM. Meanwhile, two prototypes, one for each proposed segmental rotor type, are also designed and manufactured. Finally, the validity of the proposed motors is further verified by test results.
An Efficient Clamp to Reduce Switch Voltage Stress of Forward Converter
Kim, Marn-Go ;
The Transactions of the Korean Institute of Power Electronics, volume 21, issue 1, 2016, Pages 10~18
DOI : 10.6113/TKPE.2016.21.1.10
In this study, an efficient clamp is proposed to reduce the switch voltage stress of a forward converter. The proposed clamp consists of a conventional LC snubber, a tertiary winding, and a diode. When the switch is turned OFF, the magnetizing inductor energy of the transformer is recovered directly into the flyback output, which is the tertiary winding and diode network, instead of circulating in the LC snubber. Therefore, switch voltage stress and circulating current caused by the magnetizing inductor energy are reduced. This condition improves the efficiency of the forward converter with limited switch voltage stress. A theoretical analysis and the design guidelines of the proposed converter are provided. Experimental results are also reported.
Design and Control Strategy for Autonomous and Seamless Mode Transition of High Efficiency Bidirectional DC-DC Converter for ISG Systems
Park, Jun-Sung ; Kwon, Min-Ho ; Choi, Se-Wan ;
The Transactions of the Korean Institute of Power Electronics, volume 21, issue 1, 2016, Pages 19~26
DOI : 10.6113/TKPE.2016.21.1.19
In this study, a bidirectional DC-DC converter for idle stop and go (ISG) is developed to reduce fuel consumption. A three-phase non-isolated half-bridge converter is selected through a design method by considering efficiency and volume. According to the state of charge of the batteries at both the low-voltage and high-voltage sides, buck mode, which charges a low-voltage battery from the generated motor energy, and boost mode, which provides power to the motor from the low- and high-voltage battery sides, are required in the ISG system. Hence, an autonomous and seamless bidirectional control method using a variable current limiter is proposed for mode change. A 1.8 kW engineering sample of the proposed converter has been built and tested to verify the validity of the proposed concept. The maximum efficiencies, including gate driver and control circuit losses, are 96.4% in charging mode and 96.1% in discharging mode.
A Switching Method of Single Phase Grid Connected Inverter for Common Mode Noise Reduction
Lee, Seung-Ju ; Hong, Chang-Pyo ; Kim, Hag-Wone ; Cho, Kwan-Yuhl ;
The Transactions of the Korean Institute of Power Electronics, volume 21, issue 1, 2016, Pages 27~33
DOI : 10.6113/TKPE.2016.21.1.27
A pulse-width modulation (PWM) method for common mode noise reduction in a PWM inverter connected to a single-phase grid is proposed in this study. The extensively used conventional switching method may experience common mode voltage problems, which generate current leakage and electromagnetic induction problems. In the proposed switching method, the neutral point of the output voltage is always fixed at both ends of the input voltage to reduce common mode noise. The validity of the proposed method is proven through simulation and experimental results.
Power Loss Analysis of Transformer Caused By Current Harmonics
Jang, Seungyong ; Han, Sanghoon ; Choi, Jaeho ;
The Transactions of the Korean Institute of Power Electronics, volume 21, issue 1, 2016, Pages 34~41
DOI : 10.6113/TKPE.2016.21.1.34
This study investigates transformer losses caused by current harmonics. Electrical transformers are designed to work under sinusoidal voltage and current waves at a rated frequency. Recently, various nonlinear loads, such as power electronic converters, are connected to a power system; these converters generate current harmonics. Current harmonics increase power loss in transformers, which results in several problems, including temperature increase of the transformer and insulation damage. These problems will eventually shorten the operational life of the transformer. In this study, different types of losses caused by current harmonics in three-phase transformers are studied under linear and nonlinear load conditions. Linear loads are simulated and experimented on using pure resistance load, whereas nonlinear loads are simulated and experimented on using a three-phase twelve-pulse thyristor full-bridge rectifier. The different types of losses in three-phase transformers are evaluated analytically through the experimental result and simulation in PSiM.
LED Driver Compatible with Both Electronic and Magnetic Ballasts
Gu, Hyun-Su ; Choi, Yoon ; Kang, Jeong-Il ; Han, Sang-Kyoo ;
The Transactions of the Korean Institute of Power Electronics, volume 21, issue 1, 2016, Pages 42~48
DOI : 10.6113/TKPE.2016.21.1.42
Light-emitting diode (LED) drivers are recently replacing fluorescent lamps; these drivers can operate adaptively with various ballasts without modifying and removing such ballasts. To satisfy these trends, a LED driver that is compatible with both electronic and magnetic ballasts is proposed in this study. Unlike conventional LED drivers, the proposed driver has a ballast recognition circuit and a mode selection circuit to operate ballasts at optimal conditions. Therefore, it features low voltage stress, high efficiency, and good compatibility with both electronic and magnetic ballasts. Moreover, it can be compatible with a wide selection of ballasts from various manufacturers. To confirm the validity of the proposed LED driver, results of the theoretical analysis and experimental verification performed on a 15 W-rated prototype are presented.
A Design Methodology of Digital Controller Considering Time Delay Effect for a Modular Multilevel Converter VSC HVDC System
Song, Ji-Wan ; Ku, Nam-Joon ; Kim, Rae-Young ;
The Transactions of the Korean Institute of Power Electronics, volume 21, issue 1, 2016, Pages 49~57
DOI : 10.6113/TKPE.2016.21.1.49
A modular multilevel converter is widely adapted for a high-voltage direct current power transmission system. This study proposes a design methodology for a novel digital control that mitigates the negative effects caused by time delay, including communication transport delay for a modular multilevel converter. The modeling and negative effect of time delay are analyzed theoretically in a frequency domain, and its compensation methodology based on an inverse model is described fully with practical considerations. The proposed methodology is verified through several simulation results using a modular 21-level converter system.
Design of the Single-loop Voltage Controller for Arbitrary Waveform Generator
Kim, Hyeon-Sik ; Chee, Seung-Jun ; Sul, Seung-Ki ;
The Transactions of the Korean Institute of Power Electronics, volume 21, issue 1, 2016, Pages 58~64
DOI : 10.6113/TKPE.2016.21.1.58
This study presents a design method for a single-loop voltage controller that is suitable for an arbitrary waveform generator (AWG). The voltage control algorithm of AWG should ensure high dynamic performance and should attain sufficient robustness to disturbances such as inverter nonlinearity, sensor noise, and load current. By analyzing the power circuit of AWG, control limitation and control target are presented to improve the dynamic performance of AWG. The proposed voltage control algorithm is composed of a single-loop output voltage control, an inverter current feedback term to improve transient response, and a load current feedforward term to prevent voltage distortion. The guideline for setting control gain is presented based on output filter parameters and digital time delay. The performance of the proposed algorithm is proven by experimental results through comparison with the conventional algorithm.
Study on Predicting Induction Motor Characteristics of Alternate QD Model Under Light Loads by Comparing Performance of MTPA Control
Kwon, Chun-Ki ; Kim, Dong-Sik ;
The Transactions of the Korean Institute of Power Electronics, volume 21, issue 1, 2016, Pages 65~71
DOI : 10.6113/TKPE.2016.21.1.65
This study investigates a high-accuracy alternate QD model to estimate the characteristics of induction motor under light loads. To demonstrate the usefulness of the alternate QD model, a maximum torque per amp (MTPA) control based on the alternate model is shown to outperform MTPA control based on the standard QD model. The experimental study conducted in this work exhibits that the MTPA control based on the alternate QD model tracks torque commands between 20 Nm and 30 Nm with 5% error, whereas the MTPA control based on the standard QD model generates torques lower by over 23% compared with the aforementioned torque commands. This result indicates that the alternate QD model is a highly accurate model for induction motors under light loads.
Development of the Real-Time Remote Battery Inspection System
Lee, Jong-Hak ; Kim, Hyung-Won ; Choi, Woojin ;
The Transactions of the Korean Institute of Power Electronics, volume 21, issue 1, 2016, Pages 72~79
DOI : 10.6113/TKPE.2016.21.1.72
Uninterruptible power supplies are extensively used as backup power in various applications such as telecommunication systems, Internet data centers, hospitals, and military technologies. Some of these applications require a considerable number of batteries, and the maintenance of such batteries is critical for the reliability of a system. However, batteries are chemical energy storage devices that deteriorate over time and frequently inspecting their performance and suitability is difficult. A real-time remote battery inspection system that applies electrochemical impedance spectroscopy is proposed and implemented in this study. The proposed system consists of a small inspection circuit and software for control. The former is developed to monitor the impedance variation of the battery and to diagnose its state. The validity and feasibility of the proposed system is proven by experimental results.
Analysis of Output Voltage Variation of a Voltage Disturbance Generator according to the Load Power Factor in Voltage Sag and Swell Mode
Han, Heung-Soo ; Jeong, Hye-Soo ; Jung, Jae-Hun ; Nho, Eui-Cheol ; Kim, Heung-Geun ; Chun, Tae-Won ;
The Transactions of the Korean Institute of Power Electronics, volume 21, issue 1, 2016, Pages 80~87
DOI : 10.6113/TKPE.2016.21.1.80
This study investigates output voltage variation of a voltage disturbance generator in case of sag and swell modes. The generator uses series transformers and silicon-controlled rectifier thyristors to provide voltage disturbance; consequently, voltage drop at the output terminal is inevitable. On the basis of the analysis, voltage drop increases as the power factor decreases in lagging. Voltage drop is 3.7 [%] at a power factor (lagging) of 0.8. Simulation and experimental results show the validity of the analysis.
Active Damping Characteristics on Virtual Series Resistances of LCL Filter for Three-phase Grid-connected Inverter
Kim, Yong-Jung ; Kim, Hyosung ;
The Transactions of the Korean Institute of Power Electronics, volume 21, issue 1, 2016, Pages 88~93
DOI : 10.6113/TKPE.2016.21.1.88
LCL filters are widely used in high-order harmonics attenuation of output currents in grid-connected inverters. However, output currents of grid-connected inverters with LCL filters can become unstable because of the resonance of the filters. Given that the characteristics of output currents in inverters mostly depend on filter performance, the exact analysis of filters by considering parasitic components is necessary for both harmonics attenuation and current control. LCL filters have three or four parasitic components: the series and/or parallel resistance of the filter capacitor and the series resistance of the two filter inductors. Most studies on LCL filters have focused on the parasitic components of the filter capacitor. Although several studies have addressed the parasitic components of the filter inductor at the inverter side, no study has yet investigated the concurrent effects of series resistance in both filter inductors in detail. This paper analyzes LCL filters by considering series resistance in both filter inductors; it proposes an active damping method based on the virtual series resistance of LCL filters. The performance of the proposed active damping is then verified through both simulation and experiment using Hardware-in-the-Loop Simulator(HILS).