• Proceedings of the KIEE Conference
• /
• 2000.07a
• /
• pp.400-402
• /
• 2000

This paper presents a game theoretic approach for power transactions analysis in a competitive market. The considered competitive power market is regarded as PooICo model, and the participating players are restricted by only two generating entities for simplicity in this paper. The analysis is performed on the basis of marginal cost based relations of bidding price and bidding generations. That is, we assume that the bidding price of each player is determined by the marginal cost when the bidding generation is pre-determined. This paper models the power transaction as a two player game and analyzes by applying the Nash eauilibrium idea. The generalized game model for power transactions covering constant-sum(especially zero-sum), and nonconstant-sum game is developed in this paper. Also, the analysis for each game model are performed in the case studies. Here, we have defined the payoff of each player as the weighted sum of both player's profits.

• Proceedings of the KIEE Conference
• /
• 2006.07a
• /
• pp.218-219
• /
• 2006

This paper is about modeling on 1500V DC electric railroad system. Electric railroad systems have peculiar characteristics against other electric system. The characteristics arc that the railroad systems have electric vehicle loads which are power-varying and location-varying with time. Because of this load characteristic, the electric railroad system modeling which reflects its own characteristics on EMTDC simulation could not be achieved. However, to reflect load characteristic on EMTDC, this paper suggests electric railroad system modeling by using TPS (Train Performance Simulator) that was developed in Korea Railroad Research Institute. A TPS program has various kinds of input data, such as operation condition, vehicle condition, and power system condition. By these data, TPS calculates mechanical power consumption and location, especially it decide electric power consumption on the basis of the fact that consumed electric and mechanical power are equal. Moreover, on this paper, movement of vehicle is reflected on EMTDC simulation as variation of feeder impedance. Also, an electric vehicle load is modeled as time-varying constant power load model.

• IEIE Transactions on Smart Processing and Computing
• /
• v.3 no.4
• /
• pp.221-225
• /
• 2014

Low power RF devices, such as RFID and Zigbee, are important for ubiquitous sensing. These devices, however, are powered by portable energy sources, such as batteries, which limits their use. To mitigate this problem, this study developed RF energy harvesting with W-CDMA for a low power RF device. Diodes are required with a low turn on voltage because the diode threshold is larger than the received peak voltage of the rectifying antenna (rectenna). Therefore, a Schottky diode HSMS-286 was used. A prototype of RF energy harvesting device showed the maximum gain of 5.8dBi for the W-CDMA signal. The 16 patch antennas were manufactured with a 10 dielectric constant PTFT board. In low power RF devices, the transmitter requires a step-up voltage of 2.5~5V with up to 35 mA. To meet this requirement, the Texas Instruments TPS61220 was used as a low input voltage step-up converter. From the evaluated result, the achievable incident power of the rectenna at 926mV to operate Zigbee can be obtained within a distance of 12m.

• Proceedings of the KIEE Conference
• /
• 1999.07c
• /
• pp.1344-1346
• /
• 1999

This paper presents a game theoretic approach for power transactions analysis in a competitive market. The considered competitive power market is regarded as PoolCO model, and the participating players are restricted by only two generating entities for simplicity in this paper. The analysis is performed on the basis of marginal cost based relations of bidding price and bidding generations. That is, we assume that the bidding price of each player is determined by the marginal cost when the bidding generation is pre-determined. This paper models the power transaction as a two player game and analyzes by applying the Nash eauilibrium idea. The generalized game model for power transactions covering constant-sum(especially zero-sum), and nonconstant-sum game is developed in this paper. Also, the analysis for each game model are Performed in the case studies. Here, we have defined the payoff of each player as the weighted sum of both player's profits.

• Proceedings of the KIEE Conference
• /
• 1999.07f
• /
• pp.2578-2580
• /
• 1999

In this paper, an embedded micro processor based resistance spot welding controller is introduced which has been recently developed by Hyosung Co. Ltd. The performance of rapid and constant high current control is tested experimentally. This paper shows configurations of measuring system for high current and realtime RMS conversion techniques of sampled discrete data. A digital proportional control is adopted for this system and the result shows that this new product is working well at wide range of welding current and the performance is improved compared with some other commercially available controllers that are widely used in our industries. User friendly MMI system and a computer network system to monitor each welding processes are also presented.

• Journal of Hydrogen and New Energy
• /
• v.28 no.6
• /
• pp.721-728
• /
• 2017

In this work, an one-dimensional analysis on spontaneous combustion in a coal stockpile was conducted using a commercial software $gPROMS^{(R)}$ based on assumption suggested by Arioy and Akgun. According to them, it is assumed that there is temperature difference between the surface of coal particle and the gas surrounded around the particle, and it is also assumed that the velocity of the gas is constant and thus oxygen is fed to the stockpile with same velocity. The higher temperature zone is formed to the surface of the coal stockpile at the initial phase and it became deepen as time is taken. Finally it was found that the temperature difference between coal particle and the gas was calculated as $57^{\circ}C$ and spontaneous combustion have not been occurred during 6 months since coal was piled in the stock.

• Proceedings of the KIEE Conference
• /
• 2015.07a
• /
• pp.1056-1057
• /
• 2015

A common DC bus is a useful connection for several DC output sources such as photovoltaic (PV), fuel cells, and batteries. Operation of the common DC power system with more than two DC output sources, especially in a stand-alone mode, requires a control scheme for the stable operation of the system. In this paper, a control scheme has been developed for applying DC power sources to the distribution system. The purpose of the control scheme is to make the best use of the DC power sources. The DC power system consists of PV, two energy storage systems and a DC-AC inverter with the control scheme. A distribution system was modeled in PSCAD/EMTDC. As the results, the control scheme is applied to the DC-AC inverter and the DC-DC converter for transfer operations between the grid-connected and the stand-alone mode to keep the DC bus and the AC voltage constant. The results from the simulation demonstrate the stable operation of a grid connected DC power system.

• Progress in Superconductivity and Cryogenics
• /
• v.14 no.3
• /
• pp.43-47
• /
• 2012

A linear compressor generates pulsating pressure and oscillating flow in a cryocooler such as Stirling cryocooler and pulse tube refrigerator. It is driven by AC power source and designed to operate at resonance of piston motion. The driving voltage level is determined by electric parameters of resistance, inductance and thrust constant of linear motor. From voltage equation on linear motor, the power factor of driving power is inherently less than 1. The phase difference between voltage and current of supplied power can be zero using capacitor and this can minimize a supply voltage level. Especially, the linear compressor of kW class requires high voltage and thus can cause a difficulty in selecting power supply unit due to limitation of voltage level. The capacitor in driving electric circuit is useful to settle this problem. In this study, the electric circuit of linear compressor is analytically investigated with assumption of mechanical resonance. The electric parameters of commercial linear motor are used in the analysis. The effects of capacitor on driving voltage level and power factor are investigated. From analytic results, it is shown that the voltage level can be mimized with using capacitor in driving electric circuit.

• Journal of Power Electronics
• /
• v.16 no.6
• /
• pp.2359-2367
• /
• 2016

Inductive power transfer (IPT) systems have become increasingly popular in recharging electric vehicle (EV) batteries. This paper presents an investigation of a series parallel/series (SP/S) resonant compensation network based IPT system for EVs with further optimized circular pads (CPs). After the further optimization, the magnetic coupling coefficient and power transfer capacity of the CPs are significantly improved. In this system, based on a series compensation network on the secondary side, the constant output voltage, utilizing a simple yet effective control method (fixed-frequency control), is realized for the receiving terminal at a settled relative position under different load conditions. In addition, with a SP compensation network on the primary side, zero voltage switching (ZVS) of the inverter is universally achieved. Simulations and experiments have been implemented to validate the favorable applicability of the modified optimization of CPs and the proposed SP/S IPT system.

• Journal of Power Electronics
• /
• v.1 no.2
• /
• pp.78-87
• /
• 2001

A new high-power step-up based on the two-module parallel-input (PISO) modular dual inductor-fed push-pull converter is proposed. The proposed converter is operated at a constant duty cycle and employs and auxiliary circuit to control the output voltage with a phase-shift between two modules. It shows a high efficiency due to the greatly reduced switch turn-off stress. It also shows a high and linear voltage conversion ratio, low current stress in the output capacitor, and fast control-to-output dynamics. The operation principles and the mathematical models of the proposed converter are presented. Features of the proposed converter are discussed in comparison with the two-module PISO modular dual inductor-fed push-pull converter. Also, experimental results from a 50kHz, 800W, 350 Vdc prototype with an input voltage range of 20-32 Vdc are provided to confirm the validity of the proposed converter. The new converter compares favorably with the conventional counterpart, and is considered well siuted to high-power step-up applications.