Moon-Taek Cho

A Study on the Improved Stability of Inverter through History Management of Semiconductor Elements for Power Supply

This study suggested the methods to check a proper replacement time, etc. by managing operation data of IGBT used as switching element of inverter for improving the stability of inverter, which was checked through practical experiment. This study accumulated and recorded data such as operation time of IGBT and temperature of radiator for the use in setting, etc. of proper replacement time by checking the data through an indicator. Methods and systems suggested in this study will be also easily used in various sectors using other electric system and semiconductor switching elements for power.

A Study on Direct Vector Control System for Induction Motor Speed Control

In this thesis, in order to improve driving characteristics of vector control of an induction motor that is used in motors and elevators, a highly-precise method for flux observation has been exercised by using an algorism of flux observer based on the combined voltage and current model. And it also emphasizes the improvement of the control characteristics in low speed region where established schemes have many problems. The overall system consisted of speed controller with the Anti-windup PI controller, current controller, flux controller. And 2DOF is applied to induction motor in order to supply these weak points of PI speed control method in this paper. To prove the propriety of this paper, the various simulations carried out adequacy and stability using Matlab, and at the same time real system is made, so it is proved. As the results of embodying the system, the robust system is realized.

Integrated Plant Growth Measurement System Based on Intelligent Circumstances Recognition

In this paper, based on core technologies such as overcoming a place’s limitations, light that can substitute for the sunlight, automation, nutrient supply system and temperature, and intelligent situation recognition for solar power generation, geothermal HVAC (heating, ventilating, and air conditioning), a plant growth analysis system for vegetation factories was designed. The system is likely to improve the freshness of agricultural products through order and planned productions, to create new markets through the convergence of the IT and BT industries, and to promote convenience in farming and comfort in workspaces through automatic control, robot development, etc. In addition, the system is expected to offer opportunities for urban residents to experience and learn the whole process of a plant’s growth; to provide a leisurely life, such as a downtown oasis, to those who are tired of the dreary city life; to prevent environmental pollution through the effective use of recycled resources; and to produce and stably supply diverse agricultural products all year round, regardless of the weather.

Grid Connected Photovoltaic System Using Inverter

In this paper, a boost chopper using PV (Photovoltaics) system and PWM (Pulse Width Modulation) voltage type power converter were constructed to provide a pleasant environment to the patients in the hospital wards by controlling temperature, humidity and air-conditioning and heating. For the stable modulation of solar cell, synchronizing signal and control signal were processed using one chip microprocessor. In this thesis, in addition, grid voltage was detected and this grid voltage and inverter output were operated at the same phase for the phase locking with PWM voltage source inverter so that surplus power could be linked to grid. This characteristic were applied on the temperature and humidity sensors in the general buildings and buildings having specific purposes such as hospitals. The good dynamic characteristic of inverter could be obtained by these applications. Also, PWM voltage inverter maintains a high power factor and low-frequency harmonic output so that power can be supplied in the load as well as system.

Optimized Design of Charger for Electric Vehicles with Enabled Efficient CCCV Mode Movement

This paper presents a charger technology for the electric vehicles that enables charge and discharge not only for low voltage and high voltage but also for any battery type by using a high performance DSP. The proposed charger was made to function as generalized fast and low battery by using PWM buck converter that runs with CCCV(Constant Current Constant Voltage) mode. Besides, by designing the controller as fixed-type and varied suiting to the load characteristics, constant output was ensured even during power trip. Also, by controlling the battery type, charge, and discharge, a/s becomes easy. This battery would be possibly implemented not only in the Off Board Charger of the electric vehicles but also in the On Board Charger of EREV(Electric Range Extender Vehicle) in future.

Characteristics Analysis and Library Development for Common Lamps by Using PSPICE Modeling

Recently, common lamps have been used in a variety of fields, including simple illumination science, and their domain of use is increasingly widening. In this study, we configure a library through modeling and verify its accuracy through simulations for widely used and representative lamps such as CCFL, fluorescent lamps, and HID lamps. On the basis of our experiments, we also perform a lamp simulation using PSPICE, which allows us to take advantage of the lamp library easily.

PV System for Medical Devices in the Hospital

In this thesis, a boost chopper using pv system and PWM(Pulse Width Modulation) voltage type power converter were constructed to provide a pleasant environment to the patients in the hospital wards by controlling temperature, humidity and air-conditioning and heating. For the stable modulation of solar cell, synchronizing signal and control signal were processed using one chip microprocessor. Power converter system was constructed with booster chopper and voltage source inverter and test was carried out for both devices. Constant voltage control method was used to track a maximum power point at boost converter control. For the inverter control, synchronizing signal and control signal were processed by microprocessor according to the switching theory of SPWM(Sinusoidal pulse Width Modulation), directions to each sector and stable modulation. Test was carried out for inverter control using SPWM control method. In addition, grid voltage was detected and this grid voltage and inverter output were operated at the same phase for the phase locking with PWM voltage source inverter so that surplus power could be linked to grid. This characteristics were applied on the temperature and humidity sensors in the general buildings and buildings of specific purpose such as hospitals. The good dynamic characteristic of inverter could be obtained by these applications.

Electric Braking Control System to Secure Braking Force in the Wide Speed Range of Traction Motor

In this paper, a vehicle stopping method using an electric brake until a traction motor is stopped is studied. At the moment of vehicle stop, electric brake is changed to control mode wherein torque is reduced at a low speed. Gradient is controlled by estimating the load torque of motor thereby traction motor is not rotated after stop. In addition, coasting operation and brake test were performed from normal-opposite operation and start using a small-scale model comprising the inertial load equipment and the power converter. Further, traction motor was made to be equipped with a suspension torque. Pure electric braking that makes traction motor stopped by an air brake at the time of stop was also implemented. Constant torque range and constant power range were expanded during braking so that braking force was secured with the electric brakes even in high speed region. Therefore, vehicle reduction effect could be expected by reducing parts related with an air brake which is not used frequently by using a pure electric brake in the M car in wide speed region. Further, maintenance of brake system could be reduced, Besides ride comfort of passenger in the electric rail car, energy efficiency improvement, and noise reduction effect could be additionally expected.

Method and System for Measuring the Performance Based on the WIFI in Smart Media

The study developed a Wi-Fi performance measurement (measurement of download and upload speeds, delay time, and the Web page loading speed) system and measurement software for smart phones. The measuring of Wi-Fi performance in smart phones is important not only upload and download speeds, but also a loading speed of Web pages for end users; hence, the study included a method for measuring a Web page loading speed as well as its procedures. We expect the study result will provide detailed criteria for quality management, e.g. a quality index and criteria about the Wi-Fi service on the smart phone platform in order to be utilized as an objective standard for service development of operators, and service quality in operation and user environment. In addition, the study will be able to organize a fair, objective, and quality-improved environment by building trustworthy quality measurement S/W and systems, including quality-related policy support and conditions, such as smart phone-based SLA (Service Level Agreement).

Research on the Multi-angle Measuring Service Quality for IPTV Quality Measurement

Provide a variety of services, from the current IPTV. However, in the service of new services such as real-time multi-angle quality measurement and verification work, there are few. Quality measures from the point of view of such subscriber are required. In this paper, we propose a way of measuring the quality of the IPTV multi angle. This service is a variety of services that can show when the cameras installed in various angles. IPTV service subscribers by the proposed method to measure how many complaints channel switching time measured by real-time IPTV services, and channel switching time multi angle comparison and analysis. Multi angle evaluation of services, and could seek to improve performance would be using it.