• The Transactions of the Korean Institute of Power Electronics
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• 제14권4호
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• pp.299-306
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• 2009

Recently, although the power consumption of the flyback converter at the light load and standby power load was minimized by the burst mode operation of PWM IC, flyback converter has still the low efficiency characteristics by the high magnetizing current flowing through magnetizing inductance of transformer. This paper proposes a novel flyback converter with an improved efficiency characteristics and the reduced magnetizing current at the light load and standby power load. Prototype of the 70W multi-output flyback converter for an auxiliary power module of 50 inch PDP TV is built and the experimental results are described.

• Current Photovoltaic Research
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• 제10권4호
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• pp.111-115
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• 2022

For the high efficiency of the photovoltaic module, a high-output solar cell, which is the basis of photovoltaic power generation, is required. As the light receiving area of the solar cell increases, the light receiving area of the photovoltaic module also increases. Accordingly, recent trend is to use large-area solar cells such as M6 and M8 instead of M2-based solar cells for manufacturing the photovoltaic module and a study on the mechanical stiffness of the module with increased size is required. In this study, a mechanical load test corresponding to IEC-61215 was performed among the reliability tests of large-area photovoltaic modules. In order to confirm the degree to which the mechanical load test affects the photovoltaic module, the output and EL images were checked by sequentially increasing the pressure by 600 Pa at a pressure of 2400 Pa. Also, factors such as output and efficiency of large-area photovoltaic modules were verified through mechanical load testing of actual large-area photovoltaic modules and the rate of change was very small at 1%.

• The Transactions of the Korean Institute of Electrical Engineers
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• 제35권9호
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• pp.403-408
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• 1986

In this paper, the method to improve the efficiency of an induction motor at light load is discussed. Efficiency of induction motor can be very substantially improved by keeping the slip frequency as constant. Therefore, to simplify the control loop, algorithm which maintain constant slip frequency and control the input voltage is adopted. Simplified high efficiency drive of induction motor using PLL technique is suggested. In order to verify the validity of this system, the test results are compared with those obtained by optimal slip drive system and then we found closer to the optimal efficiency. For example its efficiency is improved from 18[%] to 42[%] at a few fraction of the full load (20[%]).

• Proceedings of the KIEE Conference
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• 대한전기학회 1996년도 추계학술대회 논문집 학회본부
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• pp.323-325
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• 1996

The design of Intelligent Energy Saving Power System Controller (IESPSC) for Telecom DC power plants is proposed and presented in this paper. From the past experience. rectifiers for Telecom DC power plants have been operated inefficiently at light loads. IESPSC offers "novel load sharing" approach based on the knowledge of each unit's efficiency of paralleled rectifiers. Neural networks is used for identifying each rectifier's efficiency characteristic curve corresponding to load currents, which is in turn utilized to produce a system efficiency close to the maximum under all operating conditions. In addition, by limiting the number of operating units to the minimum while maintaining high efficiency at the determined loads, a drastic savings in operating cost can be achieved.

• Journal of the Korean Society of Industry Convergence
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• 제22권3호
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• pp.365-371
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• 2019

Recently, the demonstration and research on the power transmission using high voltage DC such as HVDC(High Voltage DC), Smart Grid, DC transmission and distribution have been actively conducted. In order to control the power converter in high-voltage DC power transmission system, SMPS(Switching Modulation Power Supply) for power converter control using high-voltage DC input is essential. However, the demand for high-pressure SMPS is still low, so the development is not enough. In the low-output SMPS using the high-voltage input, it is difficult to achieve high efficiency due to the switching transient loss especially at light load. In this paper, we propose a new switching scheme for high power SMPS control for low output power. The proposed method can provide better efficiency increase effect in the light load region compared to the existing PWM method. To verify the feasibility of the proposed method, a 40 W SMPS for HVDC MMC(Modulation Multi-level Converter) was designed and verified by simulation.

• Magazine of the Korean Society of Agricultural Engineers
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• 제18권4호
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• pp.4259-4264
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• 1976

This paper, is about the test on the operating performance of diesel engine by using of soybean oil which farmers could supply in their farm yard. The diesel engine used is a swirl-chamber type, four stroke cycle with single cylinder, air cooling and its rated horse power is 2 PS per 1300 rpm. Several results obtained are as follows; 1. The starting performance of diesel engine with soybean oil is almost the same as that with light oil. 2. The variation of engine speed according to various engine load is small when soybean oil is used compared with light oil. It is considered that soybean oil is desirable for the purpose of industerial power machine fuel. 3. The specific fuel consumption increases approximately 10 percent high in the condition of rated horse power and maximum horse power and shows less or same during the load test in low velocity, when soybean oil is used 4. Though the brake thermal efficiency in the condition of rated horse power and maximum horse power is inclined to decrease when soybean oil is used compared during the load test in low velocityt shows good inclination.

• Proceedings of the KIPE Conference
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• 전력전자학회 2001년도 전력전자학술대회 논문집
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• pp.364-367
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• 2001

ZVS Full-bridge converter is widely used in medium power level(1-3kW). ZVS can be designed within a limited load range and ZVS failure at light load condition is assumed to be acceptable within the given efficiency and thermal constraints. However, unbalanced ZVS resonant energy caused by dc blocking capacitor may alleviate the switching loss problem at light load condition. ZVS resonant energy is unbalanced by do blocking capacitor. This problem causes loss and heat concentration of a switch leg, In this paper, this problem is analyzed, and a novel control method is proposed to solve the problem.

• Proceedings of the KIEE Conference
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1750-1752
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• 2005

This paper presents a variable speed wind generation system where fuzzy logic controllers is used as efficiency optimizer. The fuzzy logic controller increments the machine flux by on-line search to improve the generator efficiency in case of light load. The speed of the induction generator is controlled according to the variation of the wind speed in order to produce the maximum output power The generator reference speed is adjusted according to the optimum tip-speed ratio. The complete control system has been developed by simulation study.

• Proceedings of the KIEE Conference
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• 대한전기학회 1998년도 하계학술대회 논문집 F
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• pp.1984-1986
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• 1998

This paper presents an optimal efficiency control for the inverter fed induction machine system using neural network. The motor speed and the load torque vary the efficiency characteristics of an induction motor. The optimal slip frequency has nonlinearity varied by the load torque as well as the motor speed. The induction motor is driven using the inverter system and the indirect vector control method which input is slip frequency. The neural network for estimating the optimal slip frequency has two input layer(the motor speed and the load torque) and one output layer(the optimal slip frequency that minimize the input power). Learning algorithm of the neural network is the back-propagation. Using the equivalent circuit including the nonlinearity of the induction motor, the loss reduction is analyzed quantitatively. Experimental results are shown noticeable power savings by proposed scheme in high speed and light load conditions.

• The Transactions of The Korean Institute of Electrical Engineers
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• 제64권9호
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• pp.1306-1314
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• 2015

This paper deals with a switching method of a three-phase interleaved bidirectional DC-DC converter to obtain high efficiency in wide load range. The proposed soft-switching method provides ZVS and ZCS at turn-on, and ZVS at turn-off of the switch as well as considerably reduced conduction loss in light load. Simulation and experiment are carried out with a bidirectional DC-DC converter having the power rating of 3 [kW], and those results show the validity of the proposed switching method.