• IEMEK Journal of Embedded Systems and Applications
• /
• 제7권6호
• /
• pp.291-300
• /
• 2012

This paper deals with the design and implementation of wireless sensor network protocol for smart power outlet system capable of fire detection, power monitoring, standby power cutoff, and home automation. The proposed protocol integrates both the CSMA and the TDMA protocols for low power consumption and good scalability. A prototype smart power outlet system employing the proposed protocol and a simple home automation network including the power outlet system have been implemented for evaluating the feasibility of the proposed protocol The result shows that the proposed protocol allows the power outlet system to be scalable with high power efficiency.

• Proceedings of the Korean Geotechical Society Conference
• /
• 한국지반공학회 2006년도 추계 학술발표회
• /
• pp.169-178
• /
• 2006

The pumped-storage power system is the one of the hydroelectric power systems, generating electricity with hydraulic head difference. In this system, the electricity is produced during the hours of peak demand by using water that has been pumped into an upper reservoir from a lower reservoir during the hours of low demand. Generally, the system consists of an under-ground power house and tunnels such as the headrace, pressure, and tailrace tunnels. The Chungsong pumped-storage power station is the sixth one In the pumped-storage power station in Korea. Both the regional self-government and the population of chungsong -Goon had made a great effort to draw this power station construction into this area. The proposed Chungsong pumped-power station construction project was accepted by the central government as a part of the national electricity plan for the first time in Korea.

• Proceedings of the KIEE Conference
• /
• 대한전기학회 1998년도 하계학술대회 논문집 E
• /
• pp.1626-1628
• /
• 1998

In reccent years the large capacity underground power transmission systems have been required gradually with the increasing demand of electric power, the increasing electric power system and the environmental limitations of an overhead transmission line in the city. But it is difficult to get the space for the underground power transmission lines because of complicated distributions of underground public facilities. But as the superconducting power cables have the large power transmission capacity, the high power transmission density, and low loss characteristics in comparison with a conventional cable, the necessity for their development are increasing. In this paper, the results of the conceptual design of HTS power cable is described.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• 제4B권3호
• /
• pp.108-113
• /
• 2004

This paper presents methods to improve performance of the power supply system in a NASA deep space explorer. In the Stirling engine driven reciprocating Brushless DC (BLDC) generator, the accurate position information of the prime mover is important to diagnose the performance of the engine and prevent distortion of the output power. Since sensors to detect the position are fragile and unreliable, and conventional sensorless techniques have drawbacks in the low speed region, a novel sensorless position detection technique for the prime mover has been proposed and verified. Another major issue of the generator for the spacecraft is power density maximization. The mass of the power system is important to the mass of the satellite. Therefore, the components of the spacecraft should be lightweight. Conventional rectification methods cannot achieve the maximum power possible due to non-optimal current waveforms. The optimal current waveform for maximizing power density and minimizing machine size and weight in a nonsinusoidal power supply system has been derived, incorporated in a control system, and verified by simulation work.

• Journal of Power Electronics
• /
• 제7권2호
• /
• pp.174-180
• /
• 2007

In this paper, a simple control method for two-stage utility grid-connected photovoltaic power conditioning systems (PCS) is proposed. This approach enables maximum power point (MPP) tracking control with post-stage inverter current information instead of calculating solar array power, which significantly simplifies the controller and the sensor. Furthermore, there is no feedback loop in the pre-stage converter to control the solar array voltage or current because the MPP tracker drives the converter switch duty cycle. This simple PCS control strategy can reduce the cost and size, and can be utilized with a low cost digital processor. For verification of the proposed control strategy, a 2.5kW two-stage photovoltaic grid-connected PCS hardware which consists of a boost converter cascaded with a single-phase inverter was built and tested.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• 제24권9호
• /
• pp.1241-1244
• /
• 2020

In this paper, we consider a downlink non-orthogonal multiple access system with a base station and N mobile stations, where we assume that instantaneous channel state information (CSI) is available at the base station. A power allocation scheme is proposed to achieve perfect fairness, which means equal data rates for all mobile stations. However, the power allocation scheme using full CSI requires high complexity. Hence, a simple power allocation scheme with low complexity is proposed by using high signal-to-noise power ratio (SNR) approximation. The simple power allocation scheme can achieve perfect fairness only for high SNR. However, it needs only the best CSI and the simple procedure to obtain power allocation coefficients. From simulation results, we show that the simple power allocation scheme provides remarkable fairness performance at high SNR.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• 제8권6호
• /
• pp.131-140
• /
• 2009

A key challenge for Wireless Body Area Network (WBAN) is to maximize the network lifetime with power-efficient and flexible duty cycling techniques on energy-constraint sensor nodes. In this paper, we propose a novel power-efficient MAC protocol for WBAN that accommodates normal, emergency, and on-demand traffic in a reliable manner. This protocol supports two wakeup mechanisms, a traffic-based wakeup mechanism, which accommodates normal traffic by exploiting the node's traffic patterns, and a wakeup radio mechanism, which accommodates emergency and on-demand traffic by using a wakeup radio. It can be seen that the proposed protocol not only improves the lifetime of WBAN but also provides a reliable method to handle sporadic events. Simulation results show that the proposed protocol outperforms WiseMAC in terms of low-power consumption and delay.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• 제17권2호
• /
• pp.1-6
• /
• 2017

Due to the recent advances in IoT technologies, reducing power consumption in battery-based IoT devices becomes an important issue. An IoT device is a kind of real-time systems, and processor voltage scaling is known to be effective in reducing power consumption. However, recent research has shown that power consumption in memory increases dramatically in such systems. This paper aims at combining processor voltage scaling and low-power NVRAM technologies to reduce power consumption further. Our main idea is that if a task is schedulable in a lower voltage mode of a processor, we can expect that the task will still be schedulable even on slow NVRAM memory. We incorporate the NVRAM memory allocation problem into processor voltage scaling, and evaluate the effectiveness of the combined approach.

• Journal of Power Electronics
• /
• 제13권2호
• /
• pp.322-328
• /
• 2013

This paper presents a modified Current Source Parallel Resonant Push-pull Inverter (CSPRPI) for single phase induction heating applications. One of the most important problems associated with current source parallel resonant inverters is achieving ZVS in transient intervals. This paper shows that a CSPRPI with the integral cycle control method has dynamic ZVS. According to this method, it is the Phase Locked Loop (PLL) circuit that tracks the switching frequency. The advantages of this technique are a higher efficiency, a smaller package size and a low EMI in comparison with similar topologies. Additionally, the proposed modification results in a low THD of the ac-line current. It has been measured as less than %2. To show the validity of the proposed method, a laboratory prototype is implemented with an operating frequency of 80 kHz and an output power of 400 W. The experimental results confirm the validity of the proposed single phase induction heating system.

• Journal of the Institute of Electronics and Information Engineers
• /
• 제50권1호
• /
• pp.97-101
• /
• 2013

There is a growing need for optical communication systems that convert large volumes of data to optical signals and that accommodate and transmit the signals across long distances. Digital optical communication consists of a master unit (MU) and a slave unit (SU). The MU transmits data to SU using digital optical signals. However, digital optical units that are commercially available or are under development transmit data using two's complement representation. At low input levels, a large number of SSOs (simultaneous switching outputs) are required because of the high rate of bit switching in two's complement, which thereby increases the power noise. This problem reduces the overall system capability because a DSP (digital signal processor) chip (FPGA, CPLD, etc.) cannot be used efficiently and power noise increases. This paper proposes a change from two's complement to a more efficient method that produces less SSO noise and can be applied to existing digital optical units.