Hak-Man Kim

A genetic approach to the attitude control of an inverted pendulum system

The authors present a genetic approach to the optimal linear quadratic regulator (LQR) problem. Design of the optimal LQR depends on choosing weighting matrices. One must carry out a trial-and-error process to choose the proper weighting matrices in general. It is not a trivial problem. They show a new possibility using a genetic algorithm (GA) to find the proper weighting matrices and hence to obtain the optimal control gain. They apply the approach to the attitude control of an inverted pendulum system, which is known as the LQR problem. They perform computer simulations on the system with a 50 cm long inverted pendulum and obtain good results.

New design of PMU for real-time security monitoring and control of wide area intelligent system

Security monitoring and control are very important for stable operation in wide area intelligent system. Electrical power grid is one of a wide area system and is progressing to intelligent system. For real-time security monitoring and control of electrical power grid, measurement of control variables such as voltage, current, real power, reactive power, power factor and system frequency must be synchronized because sub-control sites are distributed widely. Global Positioning System (GPS) is used for synchronization. In this paper, we introduce the new design concept of Phasor Measurement Unit (PMU) for security monitoring and control of electrical power grid, which is one of the wide area intelligent systems. PMU is applied d-q transformation and Phase Locked Loop (PLL) to improve the robustness of measurement. PMU is tested on three-phase 380V distribution line with resistor load.

Stabilizing scheme application for improving power system security in Korea

This paper describes the characteristics of electric power system and special stabilizing control schemes applied to improve system stability in Korea. As additional units of large generators were added to the existing generation sites with the reinforcement of the transmission facilities being delayed because of the difficulty of acquiring new sites and right-of-way, the system characteristics such as short circuit current, voltage regulation, and transient stability show the tendency of degradation. Among them, out-of-step problems of the large capacity generation stations were identified to be solved for improving the system security. This paper presents some typical special stabilizing control schemes that were applied to prevent loss of synchronism of all the generators at a site in Korea.

Soft x-ray generation using CNT based liquid hybrid target

Summary form only given. In order to image soft biological tissues that are consisted of living animal or plants, water window (2.1-4.4 nm) region of soft X-ray is generally required. However, conventional X-ray source that is based on tungsten filament tube generally produces hard X-ray. In order to solve this problem, laser based soft X-ray sources have been studied recently. In this technique solid metal or liquid-jet target has been generally applied. However, debris problem was issued for the former and small intensity of the generated soft X-ray was the problem for the latter. In this research, liquid target, which is added with carbon nanotubes (CNTs) or other metal nanopowders, was proposed as new targets for laser based soft X-ray generation. Detailed descriptions of the experimental method and results were presented in this study

Optimal voltage and reactive power control of local area using genetic algorithm

To improve the voltage profile and to reduce system losses, many switched shunt capacitors are used in a power system. It is necessary to coordinate them for operating the system effectively. In this study, a genetic algorithm (GA) is used to find optimal coordination of switched shunt capacitors within a local area of a power system. To verify the effectiveness of the proposed method, a simulation is performed of KEPCO (Korea Electric Power Corporation) power system.

Application Effects of SFCL in Korean Power System

Abstract As power systems grow more complex and power demands increase, the fault current tends to gradually increase. In the near future, the fault current will exceed a circuit breaker rating for some substations, which is an especially important issue in the Seoul. metropolitan area In this paper, the resistive and inductive SFCLs are applied to reduce the fault current in Korean power system and their technical and economic impacts are evaluated

A STUDY ON THE OPTIMAL OPERATION METHOD OF VOLTAGE REGULATOR AT DISTRIBUTION SUBSTATION

In order to deliver the suitable voltage to as many customers as possible, optimal supply voltage should be decided by the effective operation of voltage regulator at distribution substation. Bank LDC method is currently used in many utilities in order to control the supply voltage. This method uses an imaginary standard feeder to represent the total feeder characteristics. Compared with the actual system, the determination of load center with the imaginary standard feeder becomes very difficult considering random load characteristics. In this paper the optimal operation method of voltage regulator at substation is developed on the basis of statistical analysis of the voltage measurement data at customer sites. This accommodates the highest and the lowest voltage conditions not only to maintain customer voltage within the required range but to keep it closer to the nominal voltage. And the optimal operation method of multiple voltage regulators is also suggested.

AN EXPERT SYSTEM FOR THE ELECTRIC POWER DISTRIBUTION SYSTEM DESIGN

Abstract In order to design distribution systems rationally, distribution engineers consider several requirements such as regional characteristics, feeder characteristics, load characteristics and economic constraints. Since distribution systems are complex in nature, the selection of the conductor size and type, the transformer location and capacity, and the switch location and type are very difficult problems to be decided. Therefore, the problems described above are solved by heuristic knowledges based on past design experience. In this paper, the expert system using interactive inference procedures that are based on experts heuristic knowledges is developed. In particular, the link problem between the existing distribution design system and this expert system is explained. The needed knowledges are obtained from the distribution design experts.

An Expert System for the Electric Power Distribution System Design

Abstract In order to design distribution systems rationally, distribution engineers consider several requirements such as regional characteristics, feeder characteristics, load characteristics and economic constraints. Since distribution systems are complex in nature, the selection of the conductor size and type, the transformer location and capacity, and the switch location and type are very difficult problems to be decided. Therefore, the problems described above are solved by heuristic knowledges based on past design experience. In this paper, the expert system using interactive inference procedures that are based on experts heuristic knowledges is developed. In particular, the link problem between the existing distribution design system and this expert system is explained. The needed knowledges are obtained from the distribution design experts.

A Study on the Optimal Operation Method of Voltage Regulator at Distribution Substation

Abstract In order to deliver the suitable voltage to as many customers as possible, optimal supply voltage should be decided by the effective operation of voltage regulator at distribution substation. Bank LDC method is currently used in many utilities in order to control the supply voltage. This method uses an imaginary standard feeder to represent the total feeder characteristics. Compared with the actual system, the determination of load center with the imaginary standard feeder becomes very difficult considering random load characteristics. In this paper the optimal operation method of voltage regulator at substation is developed on the basis of statistical analysis of the voltage measurement data at customer sites. This accommodates the highest and the lowest voltage conditions not only to maintain customer voltage within the required range but to keep it closer to the nominal voltage. And the optimal operation method of multiple voltage regulators is also suggested.