• ETRI Journal
• /
• v.19 no.2
• /
• pp.35-47
• /
• 1997

A power amplifier operating at 3.3 V has been developed for CDMA/AMPS dual-mode cellular phones. It consists of linear GaAs power MESFET's, a new gate bias control circuit, and an output matching circuit which prevents the drain terminal of the second MESF from generating the harmonics. The relationship between the intermodulation distortion and the spectral regrowth of the power amplifier has been investigated with gate bias by using the two-tone test method and the adjacent channel leakage power ratio (ACPR) method of CDMA signals. The dissipation power of the power amplifier with a gate bias control circuit is minimized to below 1000 mW in the range of the low power levels while satisfying the ACPR of less than -26 dBc for CDMA mode. The ACPR of the power amplifier is measured to be -33 dBc at a high output power of 26 dBm.

• 제어로봇시스템학회:학술대회논문집
• /
• 2004.08a
• /
• pp.1147-1152
• /
• 2004

Switched Reluctance Motors have an inexpensive, intrinsic simplicity and low cost that makes them well suited to home appliance and office applications. However the motor suffering with necessity of shaft position sensor, lead to non-linearity of operations. Further, the involvement of static converters deteriorates the operational power factor. Implementation of a sensorless algorithm, can remove the need of position sensors. Also, the drive includes a compact power factor control in the input stage by implementing Zero Current Switching Quasi-Resonant Boost Technology. This paper presented, aims at optimized low line current distortion, high power factor, low cost and a shaft position sensorless Switched Reluctance Motor drive.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.65 no.11
• /
• pp.1800-1805
• /
• 2016

The micro-grid designed as bipolar ${\pm}750V$ low-voltage DC power distribution system demonstrated by KEPRI, demands interconnection of a number of small decentralized power source including variable renewable generator. Therefore, variable researches for the influence of interconnection with the bipolar typed DC grid and these variable power sources are required for superior quality of power distribution. Renewable power generation simulators for the bipolar ${\pm}750V$ low-voltage DC power distribution system are necessary for such researches. In this paper, we carry out a research on the photovoltaic simulator that be actually able to interconnect with a bipolar ${\pm}750V$ low-voltage micro-grid. Simulator for this research is not only able to simulate photovoltaic generation according to weather informations and PV modules characteristics, but also contribute to stabilization of bipolar ${\pm}750V$ low-voltage of the system. Therefore, the simulator was designed to develop a system that can situationally respond to variable control algorithms such as the MPPT control, droop control, EMS power control, etc.

• The Journal of the Korea Contents Association
• /
• v.8 no.11
• /
• pp.251-262
• /
• 2008

In this study we investigated the effects of physical therapeutic intervention through electromyography, ultrasonographic imaging and changes of the IL-$1{\beta}$, IGF-1 and IGF-2 in skeletal muscle of rats injured experimentally. The twenty Sprague-Dawley male rats were randomly divided into the 4 groups: a normal, a control, a low power laser and a neuromuscular electrical stimulation group. Abnormal spontaneous activities had not been shown, both in normal and skeletal muscle injured rats. The maximum diameter of the calf muscle was significantly increased in the low power laser and neuromuscular electrical stimulation groups compared with control group. The level of the serum IL-$1{\beta}$ was more decreased in the low power laser and neuromuscular electrical stimulation groups than that of control group. The activation level of the IGF-1 and the IGF-2 were significantly higher in the control, low power laser and neuromuscular electrical stimulation groups than that of normal group. However, there was no statistically significant difference among the control, low power laser and neuromuscular electrical stimulation groups.

• Proceedings of the KIEE Conference
• /
• 2005.10b
• /
• pp.113-115
• /
• 2005

To explore the seafloor, an observation instrument should be laid there for a long time and it should be again withdrawn. This system must be designed low power consumption model because it operates for a long period, but because power control don't execute or simply control algorithm executes, power efficiency is low. Hereupon, a power control algorithm for retrieval system using the ultrasonic communication that was improved its controllability and movability was presented in this paper. Likewise, the logicality of control algorithm and remote control system were ascertained by experiments.

• Journal of Power Electronics
• /
• v.10 no.4
• /
• pp.405-411
• /
• 2010

This paper proposes a novel tracking algorithm considering radiation to improve the power of a photovoltaic (PV) tracking system. The sensor method used in a conventional PV plant is unable to track the sun's exact position when the intensity of solar radiation is low. It also has the problem of malfunctions in the tracking system due to rapid changes in the climate. The program method generates power loss due to unnecessary operation of the tracking system because it is not adapted to various weather conditions. This tracking system does not increase the power above that of a power of tracking system fixed at a specific position due to these problems. To reduce the power loss, this paper proposes a novel control algorithm for a tracking system and proves the validity of the proposed control algorithm through a comparison with the conventional PV tracking method.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.25 no.6
• /
• pp.490-495
• /
• 2020

The power loss of large-capacity systems using single-phase inverters has attracted considerable attention. In this study, optimal switching sequence model prediction control at a low switching frequency is proposed to reduce the power loss in a high-power inverter system, and a compensation method that can be utilized for model prediction control is developed to reduce errors in accordance with sampling values. When a three-level, single-phase inverter using a switching frequency of 600 Hz and a sampling frequency of 12 kHz is adopted, the power factor is improved from 0.95 to 0.99 through 3 kW active power control. The performance of the controller is also verified.

• International Journal of Automotive Technology
• /
• v.8 no.5
• /
• pp.651-658
• /
• 2007

This paper presents a new type of fuzzy logic-based power control strategy for fuel cell hybrid electric vehicles designed to improve their fuel economy while maintaining the battery's state of charge. Since fuel cell systems have inherent limitations, such as a slow response time and low fuel efficiency, especially in the low power region, a battery system is typically used to assist them. To maximize the advantages of this hybrid type of configuration, a power distribution control strategy is required for the two power sources: the fuel cell system and the battery system. The required fuel cell power is procured using fuzzy rules based on the vehicle driving status and the battery status. In order to show the validity and effectiveness of the proposed power control strategy, simulations are performed using a mid-size vehicle for three types of standard drive cycle. First, the fuzzy logic-based power control strategy is shown to improves the fuel economy compared with the static power control strategy. Second, the robustness of the proposed power control strategy is verified against several variations in system parameters.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2009.10a
• /
• pp.539-540
• /
• 2009

• The Transactions of the Korean Institute of Power Electronics
• /
• v.22 no.1
• /
• pp.75-81
• /
• 2017

This paper presents a design and parallel control strategy of 1.8 kW low-voltage DC-DC converter (LDC) for mild hybrid electric vehicles to improve their power density, system efficiency, and operation stability. Topology and control scheme are important on the LDC for mild hybrid electric vehicles to achieve high system efficiency and power density because of their very low voltage and large current in input and output terminals. Therefore, the optimal topological structure and control algorithm are examined, and a detailed design methodology for the power and control stages is presented. A working sample of 1.8 kW LDC is designed and implemented by applying the adopted topology and control strategy. Experimental results indicate 92.45% of the maximum efficiency and 560 W/l of power density.