• 대한전기학회논문지:시스템및제어부문D
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• 제50권1호
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• pp.8-13
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• 2001

LMS algorithm has been used for plant identifier and noise cancellation. This algorithm has been researched for performance enhancement of filtering. The design and development of a reliable system has been becoming a key issue in industry field because the reliability of a system is considered as an important factor to perform the system's function successfully. And the computing with reliability and fault tolerance is a important factor in the case of aviation, system communication, and nuclear plant. This paper presents design of reliable adaptive filter with fault tolerance. Generally, redundancy is used for reliability. In this case it needs computing or circuit for voting mechanism, or fault detection. Therefore it has simple computing, and practicality for application. And in this paper, reliability of adaptive filter is analyzed. The effectiveness of the proposed adaptive filter is demonstrated to the case studies of plant identifier and noise cancellation by using DSP.

• 전기학회논문지
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• 제57권4호
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• pp.551-559
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• 2008

Increase in power consumption can cause a serious stability problem of an electric power system without construction of new power plants or transmission lines. Also, it can generate large power loss of the system. In costly and environmentally effective manner to avoid constructing the new infrastructures such as power plants and transmission lines, etc, the distributed generation(DG) has paid great attentions so far as a solution for the above problem. Selection of optimal location and size of the DG is the necessary process to maintain the stability and reliability of existing system effectively. However, the systematic and cardinal rule for this issue is still open question. In this paper, the method to determine optimal location of the DG is proposed by considering power loss when the DG is connected to an electric power grid. Also, optimal size of not only the corresponding single DG but also the multi-DGs is determined with the proposed systematic approach. The IEEE benchmark 30-bus test system is analyzed to evaluate the feasibility and effectiveness of the proposed method.

• Journal of Electrical Engineering and Technology
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• 제12권4호
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• pp.1556-1565
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• 2017

This paper depicts the design, implementation and analysis of efficient resonant based wireless power transfer (WPT) technique using three magnetic coupled coils. This work is suitable for mid ranged device due to small form factor while minimizing the loading effect. A multi turned loop size resonator is exploited for both the transmitter and receiver for longer distance. In this paper, class-E power amplifier (class-E PA) is introduced with an optimum power tracking mechanism of WPT system to enhance the power capability at mid-range with a flat gain. A robust method of finding optimum distance is derived with an experimental analysis of the designed system. In this method, the load sensitive issue of WPT is resolved by tuning coupling coefficient at considerable distances. Our designed PA with a drain efficiency of 77.8% for a maximum output of 5W is used with adopted tuning technique that improves the overall WPT system performance by 3 dB at various operating points.

• 전력전자학회논문지
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• 제26권6호
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• pp.381-389
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• 2021

Most diagnosis approaches rely on historical failure data that might not be feasible in real operating conditions because the battery voltage and internal parameters are nonlinear according to various operating conditions, such as cell-to-cell configuration and initial condition. To overcome this issue, the estimator and the predictor require integrated approaches that consider comprehensive data, with the degradation process and measured data taken into account. In this paper, vector autoregressive models (VAR) with various parameters that affect overdischarge to the cell in the battery pack were constructed, and the cell-to-cell parameters were identified using an adaptive model to analyze the influence of failure prognosis. The theoretical analysis is validated using experimental results in terms of the feasibility and advantages of fault prognosis.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.702-703
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• 2011

Large offshore wind farms using high voltage direct current transmission system (HVDC) have been considered and exploited in many countries in the world. The maintenance of the stable operation of wind farm and interconnected system is an important issue, especially in the case of fault. To ensure the stable operation after fault clearance, the PCC voltage must be restored as soon as possible and meet the grid code requirement. This paper will evaluate the PCC voltage recovery ability of a large offshore wind farm as it is connected to a weak grid via a VSC-HVDC.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 추계학술대회 논문집 학회본부
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• pp.118-121
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• 1988

Load forecasting is an important issue as for the economic dispatch and there have been many researches which are classfied into two classes, time series method and factor analysis method. But the former is not adaptive for a sudden change of a correlated factor and the latter is not inefficient as the factor estimation is not easy. To make matters worse, both of them are not good for the estimation of special days. It is because the load forecasting is not a problem modeled precisely in mathematics, but a problem requires experience and knowledge those can solve it case by case. In this viewpoint, an expert system is proposed which can use complicated experience of an expert by use of fuzzy decision.

• Journal of Power Electronics
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• 제10권1호
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• pp.34-42
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• 2010

Reliability is an important issue in cascaded H-bridge converters (CHB converters) because they use a high number of power semiconductors. A faulty power cell in a CHB converter can potentially lead to expensive downtime and great losses on the consumer side. With a fault-tolerant control strategy, operation can continue with the undamaged cells; thus increasing the reliability of the system. In this paper, the operating principles and the control method for a CHB multilevel rectifier are introduced. The influence of various faults on the CHB converter is investigated. The method of fault diagnosis and the bypassing of failed cells are explained. A fault-tolerant protection strategy is proposed to achieve redundancy in the CHB rectifier. The redundant H-bridge concept helps to deal with device failures and to increase system reliability. Simulation results verify the performance of the proposed strategy.

• 전기학회논문지
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• 제58권6호
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• pp.1093-1099
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• 2009

Alternative energy sources such as renewable energy like solar power systems, wind power systems, or fuel cell power systems has been the rising issue in the electrical power system. This paper discusses an economic study analysis of fuel cells in the korean electricity market. It includes the basic concept of a fuel cell and the korean electricity market. It also describes the need of renewable energy and how the fuel cell is connected with the local grid. This paper shows the impact of production and recovering thermal energy of a grid-connected fuel cell power system. The profit maximization approach has been structured including electrical power trade with the local grid and heat trade within the micro-grid. The strategies are evaluated using a local load that uses electric and thermal power which has different patterns between summer and winter periods. The solution algorithm is not newly developed one, but is solved by an application called GAMS. Results indicate the need and usefulness of a fuel cell power system.

• Journal of Electrical Engineering and Technology
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• 제12권5호
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• pp.1689-1696
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• 2017

In recent academic and industrial circles of the Republic of Korea, the securement of available reactive power reserve against the line faults is at issue. Thus, simulations have been performed for the securing of effective reactive power reserve (effective Q) to prepare for the line faults and improve reactive power monitoring and control methods. That is, a research has been conducted for the fast-decoupled Newton-Raphson method. In this study, a method that distinguishes source and sink regions to carry out faster provision of information in the event of line fault has been proposed. This method can perform quantification with the formula that calculates voltage variations in the line flow. The line flow and voltage changes can be easily induced by the power flow calculation performed every second in the operation system. It is expected that the proposed method will be able to contribute to securement of power system stability by securing efficient reactive power. Also, the proposed method will be able to contribute to prepare against contingencies effectively. It is not easy to prepare quickly for the situation where voltage drops rapidly due to the exhaustion of reactive power source by observing voltage information only. This paper's simulation was performed on the large scale Korean power system in steady state.

• 전기학회논문지
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• 제66권8호
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• pp.1187-1194
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• 2017

After North American wide area black out on August 14, 2003, various studies have been conducted to find out the reason of the disaster. One of main reasons was misoperation of generator protection system. Since then, protective coordination between generator protection system and excitation system controls has been hot issue among electrical engineers. Among various generator protection relays, in this paper, we focused on generator overvoltage and overexcitation relay, which protect the over-flux condition of the generator. Thus, at first, we modeled the generator overvoltage, overexcitation relay and detailed power system including excitation system, governor and etc., based on actual field data. And then, we reviewed the protective coordination of generator overvoltage and overexcitation relay using electromagnetic transient program. In addition, we discussed the protective coordination method for redundant protection relays in both automatic voltage regulator and generator side.