• 전기의세계
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• v.14 no.3
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• pp.10-17
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• 1965

This paper presents a method of the voltage-reactive power control in the long and short range operations and introduces a conception, "optimum control pattern." The optimum control pattern, aiming at the over-all system control, is defined as the optimum voltage distribution which minimizes the system operating cost under the conditions that the specified power be supplied and the system voltage be kept within the specified bounds. The following procedure was adopted to obtain this optimum pattern. In the first place, a power system was divided into three blocks, namely, load, substation and generator. Lagrange's, multiplier method is applied to each block in turn, paying attention only at the operating voltage distribution. Phase angles at each bus are then modified so that the continuity of active power is maintained. This procedure may be called "block relaxation method with Lagrange's multipliers." In a long range operation, this control pattern determines the optimum installation capacity of reactive power sources. In a short range operation, it also gives the reference state of real time control and the optimum switching capacity of reactive power souces. The real time control problem is also studied from the standpoint of cooperation of control devices such as generators, shunt capacitors, shunt reactors and ratio load controllers. A proposal for the real time control will contribute to the automation of power system operation in the near future. in the near future.

• Journal of the Semiconductor & Display Technology
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• v.13 no.4
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• pp.59-63
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• 2014

Previous studies have selected wireless power transmission system using 2.45 GHz of ISM band, but the researches for 5.8 GHz microwave wireless power transmission have been relatively rare. The 5.8 GHz has some advantages compared with 2.45 GHz. Those are smaller antenna and smaller integrated system for RFIC. In this paper, the 5.8 GHz wireless power transmission system was developed and transmission efficiency was measured according to the distance. A transmitter sent the amplified microwaves through an antenna amplified by a power amplifier of 1W for 5.8 GHz, and a receiver was converted to DC from RF through a RF-DC Converter. In the 1W 5.8GHz wireless power transmission system, the converted currents and voltages were measured to evaluate transmission efficiency at each distance where LED lights up to 1m. The RF-DC Converter is designed and fabricated by impedance matching using full-wave rectifier circuit. The transmission-efficiency of the system shows from 1.05% at 0cm to 0.095% at 100cm by distance.

• Proceedings of the KIEE Conference
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• 2005.07e
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• pp.19-21
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• 2005

The purpose of power system design is, in a word, to provide a good quality of electric power. The design of reliable industrial and commercial power distribution system is important because of the high costs associated with power outage. Three major factors for realization of the purpose are: (1) To hold system frequency at or very close to a specified nominal value(e.g. 60Hz) by control of frequency-effective power. (2) To maintain the correct value of interchange power between power and local generators. (3) To hold system voltage at or very close to a specified nominal value by control of voltage-reactive power. Within the past decade, numbers of industrial and commercial facilities installed with local generation, large motors or both, are increasing. This means that system stability is of concern to a growing number of industrial plant electrical engineers and consultants.

• Proceedings of the KIEE Conference
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• 2001.05a
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• pp.201-205
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• 2001

This paper presents the load modeling process and bus load models for KEPCO power system. At first, load devices commonly used in KEPCO power systems were selected, and tested for measuring the voltage and frequency sensitivity of active and reactive power. From this test, about 40 voltage and frequency dependent load models have been obtained. The bus load composition rate for KEPCO power system has been determined using the various recent surveys and papers in order to develop the load model for a power system bus. To verify the accuracy of developed bus load models, the field test for measuring active and reactive power according to artificial variation of the bus voltage was performed at 8 substations for spring summer, autumn, winter cases. With data of this seasonal field test, more reliable bus load models for KEPCO power systems were developed.

• Proceedings of the KIEE Conference
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• 1997.07c
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• pp.894-896
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• 1997

This paper presents the continuation power flow system that is under development. The continuation power flow system provides robust solutions of power flow equations at any operating point. The robust convergency enables one to find solutions even at the point where power flow jacobian becomes singular. Basic concept of an algorithm and its application to static voltage stability analysis are presented.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.3B no.1
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• pp.44-51
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• 2003

The module UPS can flexibly implement expansion of power system capacities. Further-more, it can be used to build up the parallel redundant system to improve the reliability of power system operation. To realize the module UPS, load sharing without interconnection among parallel connecting modules as well as a small scale and lightweight topology is necessary. In this paper, the three-arm converter/inverter is compared with the general full-bridge and half-bridge topology from a practical point of view and chosen as the module UPS topology. The switching control approaches based on a pulse width modulation of the converter and inverter of the system are presented independently. The frequency and voltage droop method is applied to parallel operation control to achieve load sharing. Two prototype 3㎸A modules are designed and implemented to confirm the effectiveness of the pro-posed approaches. Experimental results show that the three-arm UPS system has a high power factor, a low distortion of output voltage and input current, and good load sharing characteristics.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.12
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• pp.108-115
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• 2014

Recently, Uninterruptible power supply(UPS) is spotlighted from concern about black out, due to reserve power problem caused by increased power consumption. When fault occurs on the grid, UPS system supplies power to loads instead of the grid. Also, it is an advantage of possible operation as Energy storage system(ESS). Bi-directional power control of AC/DC Pulse width modulation(PWM) converter is essential for grid-connected UPS system. And, mode transfer control has to be performed considering phase and dynamic characteristic under grid condition. In this paper, control of mode transfer and bi-directional power control of AC/DC PWM converter is proposed for UPS system. Also, it is verified by simulation and experimental results.

• Journal of Electrical Engineering and information Science
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• v.2 no.4
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• pp.46-52
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• 1997

In this paper th use of compensation based on a combination of active plus reactive power at distribution model system is proposed. The basic voltage-power relationships for the linearized case on an infinite bus are used and the compensation angle is defined based on the voltage magnitude response to small power injection. Compensation is supplied at several locations, and the system is subjected to varying fault scenarios, with its response observed under different system conditions. As number of control issues for a storage-based active/reactive power compensator as a bus voltage regulator are explored to compare the effectiveness of active/reactive again reactive-only compensation.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.11
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• pp.622-627
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• 2002

The power comparison techniques have implemented power measurements, in which a power comparator is used to balance ac against a dc power obtained from known values. The developed power standard system using the comparison techniques consists of dc sources, ac source, control switches, resistive voltage dividers, resistive shunts and a power comparator. The total uncertainty of the power standard system was proved by analysis of the component instruments. Its expanded(k=2) uncertainty is evaluated to be less than 30 uW/VA at unit power factor and 42 uW/VA at power factor 0.5

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.3
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• pp.169-177
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• 2014

Operation and control system has been installed and tested to use energy storage system(ESS) for frequency regulation at 4MW class of ESS demonstration facility installed at Jeju island, Korea in 2013. Simulation tests were performed by programing language C# for power system of Jeju island to develop control algorithm. Site simulation tests were performed in control system itself without connecting power system and energy storage system. Control algorithm was coded, modified and tested to load to controller and communication system and human-machine interface were developed and tested in the process of simulation tests. After similar results to that of simulation tests by programing language were obtained, power system and energy storage system demonstration facility were connected to control system by communication system. Energy storage system for frequency regulation was tested for actual frequency and simulation frequency. The site tests showed the similar results to that of simulation tests and the control systems is possible to be operated for frequency regulation. Faster response of energy storage system for frequency regulation, less costs and less capacity of energy storage systems which cover for frequency regulation of power plants. It is expected that more studies for time-reduction and time-delay elements can make less capacity of energy storage system cover more role of frequency regulation of power plants.