• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.6
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• pp.1013-1024
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• 2022

In addition to the assessment measure of electric quality levels, load loss are also a factor in hindering the financial profits of electrical sales companies. Therefore, accurate analysis of load losses generated from distributed power networks is very important. The accurate calculation of load losses in the distribution line has been carried out for a long time in many research institutes as well as power utilities around the world. But it is increasingly difficult to calculate the exact amount of loss due to the increase in the congestion of distribution power network due to the linkage of distributed energy resources(DER). In this paper, we develop smart grid big data infrastructure in order to accurately analyze the load loss of the distribution power network due to the connection of DERs. Through the preprocess of data selected from the smart grid big data, we develop a load loss analysis model that eliminated 'veracity' which is one of the characteristics of smart grid big data. Our analysis results can be used for facility investment plans or network operation plans to maintain stable supply reliability and power quality.

• Journal of the Korean Society for Railway
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• v.17 no.3
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• pp.171-177
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• 2014

PWM converter trains exhibit excellent load characteristics in comparison with conventional phase-controlled trains with low power factors, as they can be operated at power factors which are close to unity by means of a voltage vector control method. However, in the case of a high track density or extended feeding, significant line losses and voltage drops can occur. Instead of operating these trains at a fixed unity power factor, this paper suggests a continuous optimal power factor control scheme for each train in an effort to minimize line losses and improve voltage drops according to varying load conditions. The proposed method utilizes the steepest descent algorithm targeting each car in the same feeding section to establish the optimized reactive power compensation levels that can minimize the reactive power loss of the feeder. The results from a simulation of a sample system show that voltage drops can be improved and line losses decreased.

• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.377-379
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• 2002

This paper provides a new approach for the load-focused transmission marginal loss factors(MLF). It can be widely applied to power system operations and pricing mechanism in a competitive electricity market. The load-focused MLF is the ratio of required additional generation at a reference bus to the demand increments at a arbitrary bus. The new approach to determine the load-focused MLF was developed under some practically endurable assumptions. Although the suggested method is very similar to the conventional penaty factors in its concept, the method is more efficient than the existing heuristic method for the load-focused MLF. To show its effectiveness and efficiency, numerical test have been performed in IEEE 14-bus system.

• Proceedings of the KIEE Conference
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• 2003.10b
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• pp.216-219
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• 2003

The resonant inverter is widely used for induction heating, electronic ballast and supersonic motor driving circuit. In the meantime, control techniques of PWM, PFM etc.. are mainly applied to control the output power of the resonant inverter. But, in the case of using the half bridge resonant inverter, it is difficult to control the output power by PWM, because its main circuit does not provide the load free-wheeling mode. Therefore, PAM or PFM was usually applied to control output power of half bridge resonant inverter. However, PAM needs a variable DC voltage source, which makes the system structure more complex. On the other hand, in case of PFM, efficiency is declined by operation with poor power factor. This paper Proposed the novel half bridge resonant inverter which can provide the load free-wheeling mode. Also its analysis results for PWM operation with unity fundamental power factor are Presented and compared with other resonant inverters using PWM and PFM.

• Tribology and Lubricants
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• v.21 no.6
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• pp.249-255
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• 2005

In this paper, the friction characteristic of engine bearings has been analyzed in terms of a friction loss power, a minimum film thickness and an oil film pressure. This analysis has been focused on the fuel economy improvement with a low viscosity engine oil such as SAE 0W-40, which is used for a friction loss reduction and increased for a Diesel fuel economy. The friction loss power, the minimum oil film thickness and oil film pressure distribution for plain bearings of a Diesel engine are analyzed using an AVL's EXCITE program with a conventional engine oils of SAE 5W-40 and 10W-40, and a low viscosity engine oil of SAE 0W-40. The computed results indicate that a viscosity of engine oils is closely related to the friction loss power and the decreased minimum film thickness in which is a key parameter of a load carrying capacity of an oil film pressure distribution. When the low viscosity engine oil is supplied to engine bearings, it does not affect to the formation of a minimum oil film thickness. But the friction loss power has been significantly affected by low viscosity engine oil at a low operating temperature of 0. Based on the FEM computed results, the low viscosity engine oil at a low temperature range will be an important factor for an improvement of the fuel economy improvement.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.12
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• pp.93-100
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• 2013

This paper propose a method to design the rotor of synchronous reluctance motors(SynRM) for maximum torque and power factor by using DOE(design of experiment) with the design variables which are parameters of barriers and segments. In this process, there are problems that require lots of simulation time and number of simulations when calculating the both torque and power factor using the finite element method in order to find load angle, core loss per speed. In order to improve this problem, we calculate only value of flux linkage by finite element method, and can decrease analysis and the number of analysis time by applying steady state expression of the power factor and torque. Finally, in order to verify the characteristics of optimal model, we make prototype motor and compare with the conventional SynRM. In this experiment, we use the DC current decay test for calculating d-and q-axis inductance.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.218-220
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• 1997

In power system, economic dispatch problem is to minimize fuel cost with inequality constraints of generator output. To solve this problem it is very important to express power loss equation that have Quadratic function of generator power included B-coefficient. This paper presents a method in determining B-coefficient by use A-matrix that is calculated by power flow considering voltage dependent static load model. The proposed algorithm is tested with IEEE 6 bus sample system, which shows the result in each cases by the change of load component factor.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.5
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• pp.64-72
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• 2008

In the three phase four wire system, voltage unbalance caused by the unbalanced load operation, gives rise to current unbalance and de-rates by the increase of machine's loss and eventually enlarges power capacity and besides has a bad effect on power quality. Power capacitor has been used for the power factor correction of inductive load and the voltage stability of power system. And it uses instead of power side for magnetic excitation of induction motor. If voltage unbalance keeps up, it affects on voltage stress at the power capacitor and finally can be caused breakdown. In this paper, we analysed that voltage and current of power capacitor increases by the voltage unbalance factor and its stress is growing more and more.

• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1183-1185
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• 1999

The basic purpose of economic dispatch problem is that minimize fuel cost with inequality constraint of generator output. To solve this problem it is very important to express power loss equation that have quadratic function of generator output power included B-coefficient. This Paper presents a method in determining B-coefficient by use A-matrix that is calculated by loss re-distribution algorithm (LRDA) considering voltage dependent load model (VDLM)s. The Proposed algorithm is tested with IEEE 6 bus sample system, which shows the result in each cases by the change of load component factor.

• Plant Journal
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• v.17 no.2
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• pp.48-53
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• 2021

In the case of a 900 MW combined cycle power plant, most of the load on the site is a rotating device and is operated at a low power factor, and the power factor decrease increases the reactive power, which causes the efficiency of the device to be consumed and unnecessary unnecessary power consumption. This study intends to present the results by installing and operating a reactive power compensation device that absorbs and removes reactive power, which is a solution to this problem, on a 6.9 kV on-board bus. As a result of application of this system, first, it was confirmed that the power factor of the rotating machine was improved to 0.22 and the load power in the house was reduced by 1.4%, and the thermal efficiency of the generator was increased by 0.1% and the power generation power by 810 kW. Next, it was confirmed that the cost of construction and operation can be reduced in the future due to economic feasibility, with a decrease of 200 million won/year in electricity loss compared to 1.5 billion won in investment, an increase of 1 billion won/year in sales, and a one-year capital recovery period.