• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.2
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• pp.75-81
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• 2015

At the end of the 19th century, Edison's DC power system and Tesla's AC power system was debated in power market. Finally, AC system became the primary system of the power market because both step-up and step-down of voltage by using transformer and long-distance power transmission are easily possible. However, nowadays the power market takes some action for introducing DC system. Both domestic and foreign researchers are conducting the study on the DC system as well. Some researchers have conducted the studies on power quality and economic evaluation of the DC distribution system but DC distribution system is still controversial in terms of the effectiveness and reliability. In this paper, we calculate the reliability indices of the Low Voltage Direct Current(LVDC) distribution system considering arrangement of power electronics, layout of the distribution system, and distance between load points.

• ETRI Journal
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• v.45 no.4
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• pp.636-649
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• 2023

Renewable energy generation cannot be consistently predicted or controlled. Therefore, it is currently not widely used in the electricity market, which requires dependable production. In this study, reliability- and variance-based controls of energy storage strategies are proposed to utilize renewable energy as a steady contributor to the electricity market. For reliability-based control, photovoltaic (PV) generation is assumed to be registered in the power generation plan. PV generation yields a reliable output using energy storage units to compensate for PV prediction errors. We also propose a runtime state-ofcharge management method for sustainable operations. With variance-based controls, changes in rapid power generation are limited through ramp rate control. This study introduces new reliability and variance indices as indicators for evaluating these strategies. The reliability index quantifies the degree to which the actual generation realizes the plan, and the variance index quantifies the degree of power change. The two strategies are verified based on simulations and experiments. The reliability index improved by 3.1 times on average over 21 days at a real power plant.

• Korea Journal of Hospital Management
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• v.5 no.2
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• pp.40-58
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• 2000

Nurses are medical personnel, who play a key role in supporting patient care, so it is important to supply them adequately in balance with ever increasing medical demand. But there appears severe shortage of nurses in some hospitals because of their uneven distribution, especially in small sized-hospitals and rural-hospitals. As nationwide distorted distribution of nurses in Korea is just like what monopsony model(a kind of market structure model) tells us, it is attempted to explain this situation of nurse labor market in Korea on the basis of monopsony model and presented in this paper. Specifically, determinants of nurse wage and the level of their relative employment were examined, and monopsony impact on their wage and the level of relative employment controlling those determinants were studied. Major results of this study arc as follows. The most important determinant of nurse wage level in this study was the wage level of a local community where each hospital located Hospital owner's characteristics an educational function of each hospital were also important factors. With these factor controlled, it was found that monopsony power of each hospital was negativel associated with nurse wage level as expected. 1% increase in monopsony power of hospital(measured by Herfindah-Hirschman Index) reduced nurse wage by $5,674{\sim}19,19$ won(in Korean currency). With regard to the level of relative employment, the most important determinant wa the capacity for supplying nurses of the local community. Again, hospital owner characteristics and educational function of each hospital were also important. With these factors controlled, it was found that monopsony power of each hospital was negative associated with the number of nurses per bed, as expected. 1% increase in monopsony power of each hospital(again measured by Herfindah-Hirschman Index) reduced the number of nurses per 100 bed as much as $0.46{\sim}0.67$. In conclusion. structural factors of nurse labor market influence the instability of nurse labor supply in Korea. Further consideration for these market structural characteristics needed for policy making related to nurse resource allocation.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.137.2-137.2
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• 2010

With current real economic growth of more than 10% per year, the Chinese energy consumption is rapidly increasing. Coal supply consists of the vast majority of China's total energy consumption requirements in 2008. China, the largest energy consumer, is expected to be heavily dependent on coal for future power generation, too (IEA,2009). A growing concern on global warming, on the other hand, drives Chinese government to declare her commitment to the reduction of CO2 emission by 2020. In this paper, China's energy market is examined for the current and future primary energy mix. Coal is found to be the biggest part accounting for 68.7% of total primary energy consumption while coal-fired power accounts for over 80% of the total power generation. The importance of Clean Coal Technology is being discussed based on the findings of the importance of coal in China's economy and its sustainable development. Among the technologies involved, a brief investigation of IGCC(Integrated Gasification Combined Cycle) technology with a review on current IGCC projects in China are provided from the perspective of environmental benefits. Studies on regional Chinese power market is also conducted. It is found that the regulated power tariff in electricity system makes the power suppliers suffer from financial loss and changes in the electricity price system is under serious consideration by Chinese government. Even though Chinese power market system causes difficulties of commercialization for IGCC technology, the potential benefits will be high due to China's huge requirements of power generating capacity and its heavy reliance on coal if the electricity price system can be changed smoothly.

• KIPS Transactions on Computer and Communication Systems
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• v.1 no.3
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• pp.133-142
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• 2012

Cournot model is one of representative models among many game theoretic approaches available for analyzing competitive market models. Recent years have witnessed various kinds of attempts to model competitive electricity markets using the Cournot model. Cournot model is appropriate for oligopoly market which is one characteristic of electric power industry requiring huge amount of capital investment. When we use Cournot model for the application to electricity market, it is prerequisite to assume the downward sloping demand curve in the right direction. Generators in oligopoly market could try to maximize their profit by exercising the market power like physical or economic withholding. However advanced electricity markets also have demand side bidding which makes it possible for the demand to respond to the high market price by reducing their consumption. Considering this kind of demand reaction, Generators couldn't abuse their market power. Instead, they try to find out an equilibrium point which is optimal for both sides, generators and demand. This paper suggest a quantitative analysis between market variables based on econometrics for estimating demand responses in smart grid environment.

• International Area Studies Review
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• v.13 no.3
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• pp.93-119
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• 2009

The purpose of this paper is to analyze the world rice market through structure and conduct frameworks utilizing annual data from 1970 to 2007. The world rice market has been unstable for much of the period post-World War II, with prices volatile and the availability of supplies uncertain. Therefore, analysis of the structure and conduct of the world rice market can provide information to better formulate the direction of future policies. Also, this paper will describe the effects of total production, export rice price, market concentration, and real exchange rate for exporting countries on total export rice volume. On basis of the expected results, the international rice market possesses market power with respects to static calculation and hypothesis test, and it will be demonstrated that exporting countries' currency crucially affects the exporting quantity and market power of those same exporting countries.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.46 no.2
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• pp.102-108
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• 2023

Recently in Korea, YouTube stock channels increased rapidly due to the high social interest in the stock market during the COVID-19 period. Accordingly, the role of new media channels such as YouTube is attracting attention in the process of generating and disseminating market information. Nevertheless, prior studies on the market forecasting power of YouTube stock channels remain insignificant. In this study, the market forecasting power of the information from the YouTube stock channel was examined and compared with traditional news media. To measure information from each YouTube stock channel and news media, positive and negative opinions were extracted. As a result of the analysis, opinion in channels operated by media outlets were found to be leading indicators of KOSPI market returns among YouTube stock channels. The prediction accuracy by using logistic regression model show 74%. On the other hand, Sampro TV, a popular YouTube stock channel, and the traditional news media simply reported the market situation of the day or instead showed a tendency to lag behind the market. This study is differentiated from previous studies in that it verified the market predictive power of the information provided by the YouTube stock channel, which has recently shown a growing trend in Korea. In the future, the results of advanced analysis can be confirmed by expanding the research results for individual stocks.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.593-595
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• 2003

The introduction of electricity industry provides generators incentives to recover the related cost through the market. Hence, the generator should sell his/her electricity at high market-clearing price with optimal operation of his/her power plant. The maintenance of power plant is the most critical factor in affecting generators' decision-making. This paper analyzes technique for establishing maintenance schedule reflecting recovery cost and considers differences in monthly load pattern in minimizing LOLP.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.77-82
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• 2001

As electric power systems have been moving from vertically integrated utilities to a deregulated environment, the charging of reactive power management is a new challenging theme for market operators. This paper proposes a new methodology to compute the costs of providing reactive power management service in a competitive electrical power market. The proposed formulation, which is basically different from those shown in the literature, consists of two parts. One is to recover investment capital costs of reactive power supporting equipment based on a reactive power flow tracing algorithm. The other is to recover operational costs based on variable spot prices using the optimal power flow algorithm. The charging shapes resulted from the proposed approach exhibit a quite good meaning viewed from a practical sense. It turns out that reactive power charges are mostly due to recovery of capital costs and slightly due to recovery of operational costs. The method can be useful in providing additional insight into power system operation and can be used to determine tariffs of a reactive power management service.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.127-129
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• 2007

Since the competitive market environment was introduced into the electric power industry, the structure of the industry has been changing from vertically integrated system to functionally unbundled and decentralized system composed of multiple (decision-making) market participants. So the market participants such as Gencos or LSE (load serving entity) need to forecast the market clearing price and thus build their offer or bidding strategies. Not just these market players but also a market operator is required to perform market analysis and ensure simulation capability to manage and monitor the competitive electricity market. For fulfilling the demand for market simulation, many global venders like GE, Henwood, Drayton Analytics, CRA, etc. have developed and provided electricity market simulators. Most of these simulators are based on the optimization formulation which has been used mainly for the least cost resource planning in the centralized power system planning and operation. From this standpoint, it seems somehow inevitable to face many challenges on modeling competitive market based on the method of traditional market simulators. In this paper, we propose a kind of new method, which is MAS based market simulation. The agent based model has already been introduced in EMCAS, one of commercial market simulators, but there may be various ways of modeling agent. This paper, in particular, seeks to introduce an model for MAS based market simulator.