A Stable Operation Strategy in Micro-grid Systems without Diesel Generators

Sung-Sik Choi,Min-Kwan Kang,Hu-Dong Lee,Yang-Hyun Nam,Dae-Seok Rho 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.1

Recently, as one of the countermeasures to reduce carbon dioxide(CO2) for global warming problems, operation methods in micro-grid systems replacing diesel generator with renewable energy sources including wind power(WP) and photovoltaic(PV) system have been studied and presented in energetic manners. However, it is reported that some operation problems in microgrid systems without diesel generator for carbon-free island are being occurred when large scaled WP systems are at start-up. To overcome these problems, this paper proposes an operation strategy in micro-grid systems by adapting control devices such as CVCF(constant voltage constant frequency) ESS(energy storage system) for constant frequency and voltage regulation, load control ESS for balancing demand and supply and SVC(static-var compensator) for reactive power compensation. From the simulation results based on the various operation scenarios, it is confirmed that the proposed operation strategy in micro-grid systems without diesel generators is a useful tool to perform a stable operation in micro-grid systems without diesel generator and also make a contribution to reduce carbon dioxide in micro-grid systems.

인버터 기반 신재생 에너지 발전 시스템의 계통 지원 운전을 위한 계통 전압 검출 방법

안현철(Ahn, Hyun-Chul),송승호(Song, Seung-Ho) 한국신재생에너지학회 2013 신재생에너지 Vol.9 No.2

The Grid code is being strengthen as increase of renewable energy ratio. Especially, the grid connection regulations are continuously being updated for stable operation of power grids. Static grid support and Dynamic grid support must make an accurate measure at Grid connected point because they needs control algorithm individually. It has to exactly measure voltage including switching ripple at the output of the inverter generating system. In addition, it is necessary to have an accurate voltage measurement when the situation rapidly changing the grid impedance is caused by the input of serial impedance of transformer and line impedance as well as Grid Fault Device. In this paper, We propose a new detection method of grid voltage to calculate accurately the r.m.s voltage of the grid connection point along the standard required by the low voltage regulation. We verified performance through simulation grid fault device.

A Stable Operation Strategy in Micro-grid Systems without Diesel Generators

Choi, Sung-Sik,Kang, Min-Kwan,Lee, Hu-Dong,Nam, Yang-Hyun,Rho, Dae-Seok The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.1

Recently, as one of the countermeasures to reduce carbon dioxide($CO_2$) for global warming problems, operation methods in micro-grid systems replacing diesel generator with renewable energy sources including wind power(WP) and photovoltaic(PV) system have been studied and presented in energetic manners. However, it is reported that some operation problems in micro-grid systems without diesel generator for carbon-free island are being occurred when large scaled WP systems are at start-up. To overcome these problems, this paper proposes an operation strategy in micro-grid systems by adapting control devices such as CVCF(constant voltage constant frequency) ESS(energy storage system) for constant frequency and voltage regulation, load control ESS for balancing demand and supply and SVC(static-var compensator) for reactive power compensation. From the simulation results based on the various operation scenarios, it is confirmed that the proposed operation strategy in micro-grid systems without diesel generators is a useful tool to perform a stable operation in micro-grid systems without diesel generator and also make a contribution to reduce carbon dioxide in micro-grid systems.

Mobile Resource Reliability-based Job Scheduling for Mobile Grid

( Sung Ho Jang ),( Jong Sik Lee ) 한국인터넷정보학회 2011 KSII Transactions on Internet and Information Syst Vol.5 No.1

Mobile grid is a combination of grid computing and mobile computing to build grid systems in a wireless mobile environment. The development of network technology is assisting in realizing mobile grid. Mobile grid based on established grid infrastructures needs effective resource management and reliable job scheduling because mobile grid utilizes not only static grid resources but also dynamic grid resources with mobility. However, mobile devices are considered as unavailable resources in traditional grids. Mobile resources should be integrated into existing grid sites. Therefore, this paper presents a mobile grid middleware interconnecting existing grid infrastructures with mobile resources and a mobile service agent installed on the mobile resources. This paper also proposes a mobile resource reliability-based job scheduling model in order to overcome the unreliability of wireless mobile devices and guarantee stable and reliable job processing. In the proposed job scheduling model, the mobile service agent calculates the mobile resource reliability of each resource by using diverse reliability metrics and predicts it. The mobile grid middleware allocated jobs to mobile resources by predicted mobile resource reliability. We implemented a simulation model that simplifies various functions of the proposed job scheduling model by using the DEVS (Discrete Event System Specification) which is the formalism for modeling and analyzing a general system. We also conducted diverse experiments for performance evaluation. Experimental results demonstrate that the proposed model can assist in improving the performance of mobile grid in comparison with existing job scheduling models.

스마트그리드 환경에서 개인정보보호를 위한 법적 과제 -「지능형전력망법」개정방향 모색을 중심으로-

백수원 ( Soo Won Baek ) 한남대학교 과학기술법연구원 2013 과학기술법연구 Vol.19 No.2

A Smart grid is being evaluated its efficient use of energy, penetration of distributed renewable power, the power of high quality service and the method of environmental problems. Global warming is largely brought about by fossil fuels like petroleum, however the green growth policy has been developed by many nations with Smart grids. A Smart grid is the one of the green growth policies. A Smart grid is digitally enabled electrical grid that gathers, distributes, and acts on information about the behavior of suppliers and consumers in order to improve the efficiency, importance, reliability, economics, and sustainability of electricity services. Especially, Korea started in 2009, for establishing the national vision for world`s first intelligent power grid(Smart grid) which has been established by a variety of policy, smart grid technology for growing interest in the fields. Despite these needs and benefits, the Smart grids by its nature is bound to increase the likelihood of the infringement of personal information. Smart grids should be able to be studied smart grid-related products, information network and the smart grids system coincidentally. Current acts cover the information network and smart grids system in many ways but smart products are excepted. For protecting of personal information should applied the concept of the Privacy by Design to the smart products, which emphasizes the proactive policy. The Privacy by Design consists of the concept which the recognition that privacy interests and concerns must be addressed proactively first. Secondly, the application of core principles expressing universal spheres of privacy protection. Thirdly, Early mitigation of privacy concerns when developing information technologies and systems, throughout the entire information life cycle. fourthly, the need for qualified privacy leadership and/or professional input. fifthly, the Adoption and integration of privacy-enhancing technologies. Embedding privacy in a positive-sum (not zero-sum) manner so as to enhance both privacy and system functionality. Finally, the respect for users` right to self-determination for personal information is one of them.

접지도체의 간격배치에 따른 개선된 접지설비 모델

송영주,최홍규,Song, Young-Joo,Choi, Hong-Kyoo 한국조명전기설비학회 2005 조명·전기설비학회논문지 Vol.19 No.3

등간격 접지 Grid의 설계에서는 대부분의 전류가 외곽접지도체로 누설되어 Grid 구석 접촉전압이 중심 접촉전압 보다 높아지는 문제점이 있다. 비등간격 접지 Grid의 설계는 이러한 문제점을 극복할 수 있으나 적절한 비등간격 접지 Grid의 설계방법이나 간격결정 방법은 논의되고 있지 않다. 따라서 본 논문에서는 비등간격 접지 Grid의 장점을 설명한 다음 비등간격 접지 Grid의 수식을 유도 비교${\cdot}$평가하여 최적의 비등간격 접지 Grid 간격비율을 제시한다. No matter how well the equally spaced grounding grid is designed, there we questions keep rising, such as leakage of current from comer conductor, high voltage of touch voltage in comers of grid than in center, and high material cost for grounding grid. The best-fitted design for unequally spaced grounding grid is a part that must be considered. Explain advantages of unequally spaced grounding grid and lead formula by dividing the number of grid division, j, into 20, instead of 7. Then, present Dij, which is optimum rate for unequally spaced grounding grid and verify safety and economy of the unequally spaced grounding grid by computer simulation with a poly-nominal function form.

Modeling and assessing cyber resilience of smart grid using Bayesian network-based approach: a system of systems problem

Niamat Ullah Ibne Hossain,Morteza Nagahi,Raed Jaradat,Chiranjibi Shah,Randy Buchanan,Michael Hamilton 한국CDE학회 2020 Journal of computational design and engineering Vol.7 No.3

Due to the widespread of new technologies, the modern electric power system has become much more complex and uncertain. The Integration of technologies in the electric power system has increased the exposure of cyber threats and correlative susceptibilities from malicious cyber-attacks. To better address these cyber risks and minimize the effects of the power system outage, this research identifies the potential causes and mitigation techniques for the smart grid (SG) and assesses the overall cyber resilience of smart grid systems using a Bayesian network approach. Bayesian network is a powerful analytical tool predominantly used in risk, reliability, and resilience assessment under uncertainty. The quantification of the model is examined, and the results are analyzed through different advanced techniques such as predictive inference reasoning and sensitivity analysis. Different scenarios have been developed and analyzed to identify critical variables that are susceptible to the cyber resilience of a smart grid system of systems. Insight drawn from these analyses suggests that overall cyber resilience of the SG system of systems is dependent upon the status of identified factors, and more attention should be directed towards developing the countermeasures against access domain vulnerability. The research also shows the efficacy of a Bayesian network to assess and enhance the overall cyber resilience of the smart grid system of systems.

Postbuckling analyses and derivations of Knockdown factors for hybrid-grid stiffened cylinders

Sim, Chang-Hoon,Park, Jae-Sang,Kim, Han-Il,Lee, Ye-Lin,Lee, Keejoo Elsevier 2018 AEROSPACE SCIENCE AND TECHNOLOGY Vol.82 No.-

<P><B>Abstract</B></P> <P>In this work, postbuckling behaviors of grid-stiffened cylinders under compressive loads are examined in an attempt to establish an analytical method to derive the shell Knockdown factor for space launch vehicle structures. Two grid systems using stiffeners – traditional orthogrid and hybrid-grid systems – are considered for the stiffened cylinders. The hybrid-grid system consists of major and minor stiffeners, which have two different cross-sectional sizes. Additionally, the baseline and minimum weight models are considered for each grid-stiffened cylinder model. The single perturbation load approach is used to represent the geometrical imperfection of cylinders. A commercial finite element analysis code, ABAQUS, is used for the postbuckling analyses. The present numerical simulations investigate the global and local instabilities for both stiffened cylinders using orthogrid and hybrid-grid systems. The global buckling load for the hybrid-grid stiffened cylinder is higher than that for the traditional orthogrid stiffened cylinder for both the baseline and minimum weight models. However, the postbuckling behaviors for the hybrid-grid stiffened cylinders are more complex, as compared to those for the orthogrid stiffened cylinders. Additionally, the shell Knockdown factors are derived using obtained numerical analysis results for the grid-stiffened cylinders. Since the shell Knockdown factor of the hybrid-grid stiffened cylinder is higher than that of the traditional orthogrid stiffened cylinders for both the baseline and minimum weight models, the hybrid-grid stiffened cylinder is more efficient in terms of the buckling design when compared to a traditional orthogrid stiffened cylinder. Furthermore, the derived Knockdown factors in the present work are higher than the values by NASA's buckling design criteria.</P>

사보니우스 소형풍력터빈 수치해석용 격자시스템 평가

김철규,이상문,전석윤,윤준용,장춘만 한국수소및신에너지학회 2016 한국수소 및 신에너지학회논문집 Vol.27 No.5

This paper presents the effect of a grid system on the performance of a small Savonius wind turbineinstalled side-by-side. Turbine performance is compared using three different grid systems; tetrahedral grid havinga concentrated circular grid around turbine rotors, the tetrahedral grid having a concentrated rectangular grid aroundturbine rotors and the symmetric grid having a concentrated tetrahedral grid near the turbine rotor blades and ahexahedral grid. The commercial code, SC/Tetra has been used to solve the three-dimensional unsteady ReynoldsaveragedNavier-Stokes analysis in the present study. The Savonius turbine rotor has a rotational diameter of 0.226mand an aspect ratio of 1.0. The distance between neighboring rotor tips keeps the same length of the rotor diameter. The variations of pressure and power coefficient are compared with respect to blade rotational angles and rotatingfrequencies of the turbine blade. Throughout the comparisons of three grid systems, it is noted that the symmetricgrid having a concentrated tetrahedral grid near the turbine rotor blades and a hexahedral grid has a stableperformance compared to the other ones.

Research on Application of Electric Power Communication in the Smart Power Grids

Qianhui Gang 보안공학연구지원센터 2016 International Journal of Signal Processing, Image Vol.9 No.9

With the rapid development of science and technology in the respect of electric power, the smartness standard of the power grid improves faster and faster. However, the power grid in the past has failed to keep pace with the needs of the current production. Therefore, it is very necessary to run the real-time, two-way, integrated and high speed communication system for the creation of the smart power grid. The article discusses the new requirements of the smart power grid on the electric power communication and the use of electric power communication in the smart power grid. It also elaborates the meanings of the electric power communication and the smart power grid, analyzing the operation condition of the smart power grid at home and the key performance of electric power communication in the smart power grid. Meanwhile, the paper studies fundamentally the real application of the electric power communication in the smart power grid. With the development of the power industry, the communication network is playing an increasingly vital role in the power system as an important part of modern power system.