• Korean Journal of Artificial Intelligence
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• v.11 no.2
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• pp.1-6
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• 2023

This paper presents a comprehensive scheme for assessing the importance of multiple microgrids (MGs) network that includes distributed energy resources (DERs), renewable energy systems (RESs), and energy storage system (ESS) facilities. Due to the uncertainty of severe weather, large-scale cascading failures are inevitable in energy networks. making the assessment of the structural vulnerability of the energy network an attractive research theme. This attention has led to the identification of the importance of measuring energy nodes. In multiple MG networks, the energy nodes are regarded as one MG. This paper presents a modified PageRank algorithm to assess the importance of MGs that include multiple DERs and ESS. With the importance rank order list of the multiple MG networks, the core MG (or node) of power production and consumption can be identified. Identifying such an MG is useful in preventing cascading failures by distributing the concentration on the core node, while increasing the effective link connection of the energy flow and energy trade. This scheme can be applied to identify the most profitable MG in the energy trade market so that the deployment operation of the MG connection can be decided to increase the effectiveness of energy usages. By identifying the important MG nodes in the network, it can help improve the resilience and robustness of the power grid system against large-scale cascading failures and other unexpected events. The proposed algorithm can point out which MG node is important in the MGs power grid network and thus, it could prevent the cascading failure by distributing the important MG node's role to other MG nodes.

• Journal of Electrical Engineering and Technology
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• v.13 no.4
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• pp.1459-1473
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• 2018

This paper focuses on voltage control schemes for multi-terminal low-voltage direct current (LVDC) distribution systems. In a multi-terminal LVDC distribution system, there can be multiple AC/DC converters that connect the LVDC distribution system to the AC grids. This configuration can provide enhanced reliability, grid-supporting functionality, and higher efficiency. The main applications of multi-terminal LVDC distribution systems include flexible power exchange between multiple power grids and integration of distributed energy resources (DERs) using DC voltages such as photovoltaics (PVs) and battery energy storage systems (BESSs). In multi-terminal LVDC distribution systems, voltage regulation is one of the most important issues for maintaining the electric power balance between demand and supply and providing high power quality to end customers. This paper focuses on a voltage control method for multi-terminal LVDC distribution system that can efficiently coordinate multiple control units, such as AC/DC converters, PVs and BESSs. In this paper, a control hierarchy is defined for undervoltage (UV) and overvoltage (OV) problems in LVDC distribution systems based on the control priority between the control units. This paper also proposes methods to determine accurate control commands for AC/DC converters and DERs. By using the proposed method, we can effectively maintain the line voltages in multi-terminal LVDC distribution systems in the normal range. The performance of the proposed voltage control method is evaluated by case studies.

• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.522-532
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• 2017

In this study, we propose a fault analysis method for a power distribution grid with PCS-based DERs. We first explain the characteristics of a PCS-based DER. According to the characteristics, the DER is considered as a current-controlled voltage source, which produces varying voltages within a certain limit so that currents equal to given references flowing from the DER to the grid (currents controlled). So, we introduce the symmetrical equivalent models in the form of varying voltage source for fault analysis and then, construct a convex optimization problem to solve the fault problem associated with the equivalent models and grid conditions. Thus, the proposed method enables to perform a proper fault analysis considering the characteristics of the DER, which are currents controlled, voltage limited, and unity power factor achievement. To verify the validity of the proposed method, we perform computer simulations with the proposed method and with MATLAB Simulink, and the results are compared.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2019.11a
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• pp.155-157
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• 2019

본 논문에서는 기존의 DERS, VSRS를 이용한 가상시점 합성이 가지고 있는 문제점을 해결하기 위해 비지도 학습 방식의 학습 모델을 이용하여 가상시점 합성에 적용하는 방식을 제안한다. 제안한 방식에서는 기존의 DERS와 달리 Disparity의 탐색범위를 지정하지 않고 Depth의 예측이 가능하며 단안의 영상에서 Depth를 예측하기 때문에 가상시점 합성 시 더 넓은 시점을 합성 할 수 있다. 또한 기존 방식은 Depth와 합성 영상을 각각 처리해야하지만 제안하는 방식은 한 번에 작업이 이루어지며, GPU를 기반으로 구현하였기 때문에 기존의 합성 방식 보다 처리 속도가 우수하다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.5 no.4
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• pp.343-350
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• 1995

A Abstract Systematic studies of the effects of crystalline forms of starting powders and p processing variables on the texture of hot - pressed silicon carbide are described. The results I indicate that hot - pressing of $\beta$ - SiC can produce strong textures and composite type duplex microstructure due to the ${\beta} {\rightarrow} {\alpha}$ phase transformation of SiC. The texture variations d during post - annealing have been observed. In the case of using a - SiC as starting pow¬d ders, the degree of preferred orientation by hot - pressing is relatively weak.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.11
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• pp.61-68
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• 2009

A Microgrid is a private small-scale power system composed of distributed energy resources (DERs), storage devices and loads. And it is expected that the Microgrid will come into wide use in the near future. For this, the establishment of the Microgrid operation methodology is a very important problem. Especially, the Microgrid is greatly different from existing private small-scale power systems because of the multiple participants. Therefore, the Microgrid operation considered various requirements according to multiple participants is more complicated than the operation of existing private small-scale power systems. In this paper, Microgrid operation methodology based on a market environment is suggested. Through case studies, the effectiveness of the suggested methodology is verified.

• KEPCO Journal on Electric Power and Energy
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• v.5 no.4
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• pp.311-321
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• 2019

With Korean Government's Renewable energy 3020 plan and 8th Basic plan for long-term power supply, renewable energy industries in Korea are active and catching attention from many relevant industry's relations. Especially with Interconnection guarantee policy established in Oct, 2016, DERs interconnection delay due to lack of allowable distribution hosting capacity is happening and reduction of reinforcement cost for distribution system where 70 % of DERs in South Korea are installed became one of important issues of KEPCO. Therefore, KEPCO needed to extract reasonable solutions to increase feasible hosting capacity of distribution feeders in order to reduce reinforcement cost under the condition of no matter in distribution system operation. This paper proposes feasible hosting capacity of distribution feeders that can be adopted and the status of DER installation in distribution system, PV output data, minimum load in distribution feeders as well as capacity of distribution lines have been investigated and analyzed in proof of the proposal.

• Journal of Biomedical Engineering Research
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• v.17 no.3
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• pp.319-326
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• 1996

Clinical myography(EMG) is a technique for diagnosing neuromuscular disorders by analyzing the electrical signal that can be records by needle electrode during a muscular contraction. The EMG signal arises from electrical discharges that accompany the generation of force by groups of muscular fiber, and the analysis of EMG signal provides symptoms that can distinguish disorder of mLecle from disor- ders of nerve. One of the methods for analysis of EMG signal is to separate the individual discharge-the motor unit action potentials(MVAPS) - from EMG signal. But we can only observe the EMG signal that is a superimposed version of time delayed MUAPS. To obtain the information about MUAP(, i.e., position, firing number, magnitude etc), first of all, a method that can separate each MUAP from the EMG signal must be developed Although the methods for MUAP separation have been proposed by many researcherl they have required heavy computational burden. In this paper, we proposed a new method that has less computational burden and performs more reliable separation of superimposed EMG signal using wavelet filter which has multiresolution analysis as major property. As a result, we develope the separation algorithm of superimposed EMG signal which has less computational burden than any other researchers and exacutes exact separation process. The performance of this method has been discussed in the automatic resolving procedure which is neccessary to identify every firing of every motor unit from the EMG pattern.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.3
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• pp.375-383
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• 2015

The virtual power plant (VPP) is a new technology to achieve flexibility as well as controllability, like traditional centralized power plants, by integrating and operating different types of distributed energy resources (DER) with the information communication technology (ICT). Though small-sized DERs may not be controlled in a centralized manner, these are more likely to be utilized as power plants for centralized dispatch and participate in the energy trade given that these are integrated into a unified generation profile and certain technical properties such as dispatch schedules, ramp rates, voltage control, and reserves are explicitly implemented. Unfortunately, the VPP has been in a conceptual stage thus far and its common definition has not yet been established. Such a lack of obvious guidelines for VPP may lead to a further challenge of coming up with the business model and reinforcing the investment and technical support for VPP. In this context, this paper would aim to identify the definition of VPP as a critical factor in smart grid and, at the same time, discuss the details required for VPP to actively take part in the electricity market under the smart grid paradigm.

• International journal of advanced smart convergence
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• v.10 no.3
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• pp.41-50
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• 2021

The purpose of this study is to analyze various energy platforms using data in the US and to suggest directions and implications. Some of the leading energy platforms are selected and analyzed based on the opening platform model. We focus on the case analysis of the US utility companies. In case of the horizontal open platform, Green Button sponsor's 'Connect My Data (CMD)' driven by the government invites the utility companies to jointly develop the sponsor's data solution. In case of the vertical open platform, the certification program 'Share My Data (SMD)' allows backward compatibility, because the technical improvement is minimal. The utility companies benchmark Amazon's three-sided market mediation and prefer platform and category exclusivity. For the former, they have data analytics companies like Enervee, Opower and for the latter, they have electronics manufactures and energy service providers (ESPs) like Distributed Energy Resources (DERs). Based on this US case study, we suggest the energy platforms to open their platform for renewable energy supply, energy conservation, high-efficiency products, and residential DER dissemination. To successfully implement the government's energy transition policy, the US platforms should be benchmarked as a business model. Especially, it is needed for them to coordinate a platform ecosystem. To ensure trust in the products and services offered on the marketplace platform, platform's certification program is helpful.