Young-Min Seo’s research while affiliated with Dankook University and other places

A diagnostic fluoroscopy X-ray system uses a 32kW or greater X-ray generator for obtaining real-time moving images and high-resolution images. Fluoroscopy X-ray systems have to use a high-capacity AC power source to perform long-time low-power fluoroscopy and short-time high-power spot exposure. In this paper, we propose a hybrid type X-ray generator for fluoroscopy X-ray system which can perform fluoroscopy and spot exposure with a low-capacity AC power source and an energy storage device. The characteristics of energy storage devices are compared and each energy storage device is modelled to equivalent circuit. And the characteristics of available energy are analyzed as a function of output voltage and power. A 32kW class hybrid X-ray generator with EDLC as an energy storage device for fluoroscopy X-ray system was constructed, and its validity was verified by means of simulations and experiments.

UPS is largely divided into passive-standby, line-interactive, and double-conversion types. In general, a double-conversion type is used at a site requiring a high reliability. The main function of the double-conversion UPS is providing the constant voltage, constant frequency, regardless of the linear or non-linear load and variation of the load. In this paper, the robust controller of the single phase double-conversion UPS is designed and its performance is verified by both simulations and experimentation.

High voltage power is needed by diverse application fields such as high precision medical equipment, and development of an X-ray generator equipped with large capacity power is accordingly required. Commercial AC power based X-ray generator has a disadvantage of having limitation in the location and of being sensitive to the power characteristics, the necessity for an independent power type X-ray generator is increasing recently. For this reason, development of an energy storage device based stand-alone type X-ray generator is required. This paper compared characteristics of energy storage devices, and composed equivalent models of each energy storage devices, and analyzed characteristics of available energy as a function of output voltage and power. An energy storage device based 32 [kW] class X-ray generator was constructed, and the output characteristics of diagnostic X-ray generators with each energy storage devices were compared through simulations and experiments.

This paper proposes a boost type single-phase inverter system to compensate the voltage sag appeared on source side. The proposed system is composed of a boost converter, a PWM inverter, and a bypass diode. If the voltage sag has appeared in input voltage, the boost converter would be operated to compensate it in the proposed system. The boost converter would not be operated when the magnitude of input voltage is more than 0.9 pu. The output voltage is kept constant by a direct-quadrature frame controller in the inverter. A 300 W class boost type inverter system was simulated, and the validity of the proposed system was verified by carrying out experiments.

This paper proposes a boost type inverter system to compensate the voltage sag has appeared in voltage sources. If the voltage sag has appeared in input voltage, a boost converter would be operated to compensate it in the boost type inverter system. The boost converter would not be operated when the magnitude of input voltage is more than 90 %, and the output voltage is kept constant by a direct-quadrature frame controller in the single-phase PWM inverter. A 300 W class boost type inverter system was simulated, and the validity of the proposed system was verified by carrying out experiments.

The formation process is presently used in the manufacture of secondary batteries such as a lithium battery. Therefore, charging and discharging processes for lithium battery are essential for the formation process. In case that the nominal capacity is 2,600 mAh and lithium battery is charged/discharged at 0.5 C, the lithium battery charge/discharge system takes very long time over two hours for charging and discharging processes, respectively. Also, to simulate such a system in a conventional way takes very long time and huge files are produced. Eventually, the simulation would be unable with general PC class. In this paper, the lithium battery charge/discharge system is analyzed by using state space averaging method and its validity is verified by both simulations and experiments. As a result, the simulation time is dramatically reduced and the charge/discharge characteristics of the lithium battery can be observed.