Earticle

최근, 국내 전력계통에서 정전사고가 증가되고 있다. 이에 따라 전력을 사용하는 산업과 주거에 경제적 손실과 불편이 초래되고 있다. 국내 전력계통의 정전은 순간전압강하와 설비 문제로서 상업용 시설과 도심지의 정 전과 이에 따른 설비 노후화, 전문 인력수급, 그리고 분리된 기관의 단일화 등의 사회적 이슈가 되고 있다. 순간전 압강하에 의해 수도권에 있는 놀이시설이 멈춰서고, 변전소 개폐기 설비운영의 미숙으로 인해 최대산단이 밀집되 어 있는 도심의 일부가 일정시간 동안 전력공급이 원활이 되지 않은 경우가 발생하였다. 이러한 이유로는 첫째, 변전소, 송배전망의 관리 투자의 소홀로 인한 전력설비의 노후화이다. 둘째, 전력망 건설 및 유지보수를 위한 인력 의 문제이다. 마지막으로, 전력망을 관리하는 한전의 분리로 인한 전력신뢰도 관리 및 경제성 관리에 의해 사고의 증가요인이 된다. 이는 국내 전력계통 정전사고가 앞으로도 계속해서 진행될 것이라 사료된다. 본 연구에서는 국 내 전력계통의 정전사고의 원인과 그 대책방법을 논의하도록 한다.

Recently, power outages have been increasing in the Korean power grid, causing economic losses and inconveniences to industries and residences. These outages have become significant social issues, especially those occurring in commercial facilities and downtown areas. The problems stem from momentary voltage drops and facility issues, including aging infrastructure, a lack of specialized personnel, and the fragmentation of management organizations. For example, momentary voltage drops have led to the shutdown of amusement facilities in metropolitan areas. Additionally, certain downtown areas, home to some of the largest industrial complexes, have experienced periodic disruptions in electricity supply due to immature substation switchgear operations. Several factors contribute to these issues. First, the aging of power facilities is due to insufficient investment in the management of substations and transmission and distribution networks. Second, there is a manpower shortage for the construction and maintenance of the power grid. Lastly, the separation of KEPCO, which manages the power grid, has led to increased accidents due to challenges in balancing power reliability and economic efficiency. It is anticipated that power outage incidents in the Korean power system will continue to occur in the future. This study will discuss the causes of these power outage incidents and propose countermeasures.

국내 전력계통의 구조는 지방지역의 발전전력이 수도권으로 송배전되는 구조이다. 이에 10차 전력수급계 획에서 전력계통의 총 발전용량은 최대 234.3[GW]으로 설계되었다. 원자력발전은 31.7[GW](13.2[%]), 재생에너지 는 108.3[GW](45.7[%])을 차지한다. 그러나 대용량 발전전력(원자력, 화력)의 송전을 위한 비수도권에서 수도권으 로 수송하는 송전선로 용량은 부족하게 전력계통이 운영되고 있다. 또한, 연평균부하 66.2[GW]에 대한 신재생에너 지원의 변동성 문제에서 원자력이용을 통해 계통운영의 신뢰성 향상이 필요하다. 국내의 전력계통은 약 160[TWh]에 도달할 것으로 예상되며, 원활한 계통을 위해서는 다른 대안이 필요하다. 본 논문은 10차 전력수급계 획에서 간과된 비수도권 발전 송전용량을 개선하고 운영적 대안을 제시하기 위해 고려되었다.

The total domestic power generation capacity of the power system has been designed as the 10th power supply and demand plan with the goal of maximum of 234.3[GW] on a summer base. It would be planned to be installed generation thtat nuclear power generation was 31.7 [GW] (13.2 [%]) and renewable energy was 108.3 [GW] (45.3 [%]).. However, the power system has been operated the lack of transmission capacity for large-capacity power generation(nuclear and thermal power) for transported from the non-metropolitan area to the metropolitan area. Also, it would be increased the reliability of the system operation due to the nuclear power in that volatility problem of renewable power sources for the average annual load of 66.2[GW]. This state would be expected to reach about 160[TWh] and, need to other alternatives. This paper was considered to improve and operational alternatives the transmission capacity of power generation in the non-metropolitan area overlooked in the 10th power supply and demand plan.

An efficient reactive power management is important in providing secured operation for a power system in terms of maintaining its stability condition. Lack of safe operating margin and reactive power support were known to cause a system to operate in an unstable voltage condition. Hence, voltage stability improvement must be planned properly so that the likeliness to instability event could be determined before the more severe event of blackout could occur in a system. For that reason, the application of the developed a new optimization technique namely Adaptive Tumbling Bacterial Foraging (ATBO) was to obtain the most possible optimal Reactive Power Planning (RPP) solution. The objective of RPP problem was not only to minimize the total power losses in a system but was also extended in terms of voltage stability and now termed as security constrained RPP (SCRPP). In order to ensure maximum benefit while ensuring secure operating condition and minimum impact to environment, the proposed ATBFO and Multi objective ATBFO (MOATBFO) were utilized to solve for the single and multi-objective for SCRPP issues. The performance of the proposed techniques were comprehensive analyzed between two other familiar optimization methods known as original Bacterial Foraging Optimization (BFO) algorithm and Meta heuristic Evolutionary Programming (Meta-EP) for standard IEEE 57 bus system. From the results it shows that the multi objective ATBFO optimization is able to give better overall improvement among all objective functions of SCRPP.

In recent, Google proposed the Project Loon being developed with the mission of providing internet access to rural and remote areas using high-altitude balloons. In this paper, we describe an applicable prototype of 5.8 GHz wireless power transmission system with rough beamforming method to Project Loon. From the measurement results, transmit beamforming phased array antenna can transmit power more efficiently compared to a horn antenna and array antenna without beamforming with increasing the transmission distance. For the transmission distance of 1000 mm, transmit beamforming phased array antenna can obtain higher received power about 1.46 times compared to array antenna without transmit beamforming.

본 논문은 국내/외 대규모 정전의 발생을 검토하고 전력 계통 운영 대책 방안을 검토하였다. 해외 주요 정전은 계통의 복잡화, 설비 투자 부족, 재생에너지 증가, 송전선 과부하 등 다양한 원인으로 분석된다. 최근 발생한 스페인 대정전의 큰 원인은 재생에너지의 의존도의 증가와 전력망의 취약성이 결합하여 발생하였다. 유럽의 전력 계통 정전으로 사회적 혼란과 경제적 손실이 발생하였다. 특히, 스페인은 풍력과 태양광의 비중이 높아 재생에너지의 영향이 크다. 국내도 탄소 배출을 줄이기 위한 에너지 정책으로 재생에너지의 발전 비중을 확대하기위해 추진하고 있다. 본 논문은 정전에 영향을 미칠 수 있는 재생에너지에 운영 전략을 검토하였다. 이를 통해 국내 재생에너지의 확대 목표를 달성하면서 전력계통의 안정성과 신뢰도를 유지하기 위한 계통운영방안 수립에 기여하고자 한다.

This paper has been examined the occurrence of large-scale blackouts domestically and internationally and reviews operational countermeasures for the domestic power system. It was analyzed the major overseas blackouts as stemming from various causes, including increasing grid complexity, insufficient equipment investment, rising renewable energy adoption, and transmission line overloads. Recently, large-scale blackout in Spain has been considered to have resulted primarily from the combination of increased reliance on renewable energy and grid vulnerabilities. It has been caused significant social disruption and economic losses in the European power grid blackout. Particularly, Spain is highly sensitive to the impact of renewable energy, with a high proportion of wind and solar power. Domestically, energy policies has been aimed at reducing carbon emissions due to promoting an expansion in the generation share of renewable energy. This paper proposed that has been examined operational strategies for renewable energy that could impact power outages. It has been considered to contribute to establishing grid operation plans that maintain power system stability and reliability while achieving domestic renewable energy expansion targets.

최근, 지구온난화와 산업화에 따라 전력수요에 따른 전력 에너지원의 전환에 대하여 국내외적으로 검토되 고 있다. 이에 본 논문은 에너지원의 전환에 의한 전력계통 전력요금과 신뢰도에 대해 조사하고, 전력계통의 특성 을 비교하였다. 그 방법으로, 첫째, 기존 전력 시스템의 안정성 가능성으로 인해 ESS 또는 스마트 그리드 기술 도 입의 필요성을 조사하였다. 둘째, 전력 요금은 신재생에너지 도입, 발전 연료비 변동, 정책 지원에 대해 검토하였 다. 특히, 독일의 에너지 전환 정책은 신재생에너지의 대중화와 요금 조정을 검토했습니다. 셋째, 국내 전력 운영 및 가격 정책을 시행하는 주요 국가와 비교하여 기술 도입 속도 및 규제 시스템의 차이를 검토했습니다. 본 연구 를 통해 국내의 전력운영 정책에 대해 토의를 통하여 국내의 효율적인 전력에너지의 전환 방안을 기대한다.

Recently, the conversion of electricity energy sources according to electricity demand has been reviewed at home and abroad due to global warming and industrialization. Therefore, this paper investigates the electricity cost and reliability of the power system due to the conversion of energy sources and compares the characteristics of the power system. First, the reliability of the existing power system was investigated for the need to introduce energy storage system or smart grid technology due to its reliability potential. Second, electricity prices were examined in relation to the introduction of renewable energy, changes in fuel costs for power generation, and policy support. In particular, Germany's energy transition policy examined the popularization of renewable energy and tariff adjustments. Third, we examined the differences in technology adoption rates and regulatory systems compared to major countries with domestic electricity operation and pricing policies. Through this study, we expect to discuss Korea's electricity operation policies and suggest ways to transition to efficient electricity energy in Korea.

The change in the power demand results in modification of frequency of interrelated power system amongst the dissimilar areas. The load frequency control can be attained by proper regulation of participating producing elements. The Area Control Error (ACE) has to be minimized for the frequency response enhancement and Integral Square Error (ISE) is generally taken as ACE. The aim of Load Frequency Control (LFC) is to diminish the Integral Square Error to Nil with constant variation of claim of dynamic energy so that the entire produced energy of the arrangement and load obligation correctly matches with every element. In this paper, results of multi area interconnected power system under Unilateral Contract are verified with the assistance of conventional controllers.

The studies of superconducting fault current limiter (SFCL) for reduction of the fault current are actively underway in the worldwide. In this paper, we analyzed the characteristics of a new type SFCL using the conventional transformer and superconducting elements combined mutually. The secondary and third windings of this SFCL were connected the load and the superconducting element, respectively. The electric power was provided to load connected to secondary windings of the transformer in normal state of power system. On the other hand, when the fault occurred in power system, the fault current was limited by closing the line of third winding of the transformer. At this time, the ripple phenomenon of the fault was minimized by opening the fault line in secondary winding of a transformer in power system. The sensing of the fault state was performed by the CT(current transformer) and then turn-on and turn-off switching behavior of the SFCL was performed by the SCR(silicon-controlled rectifier). As a result, the proposed SFCL limited the fault current within a half-cycle efficiently. We confirmed that the fault current limitation rate was changed according to the winding ratio of a transformer.

Non-contact power supply (NCPS), as a clean and safe energy supply concept has been applying wildly. Comparing with the conventional transformer the non-contact transformer has a large air gap between the long primary winding and the secondary winding. Due to it, the non-contact transformer has increased leakage inductance and reduced magnetizing inductance. So the high frequency series resonant converter has been widly used on the non-contact power supply system for transferring the primary power to the secondary one, from what a high influence voltage can be gained on the secondry coil even though the large air gap exists. However, it still has the disadvantages of the load sensitive voltage gain characteristics when load is changing. In this paper, we propose a fuzzy logic controller to adjust the frequency of the inverter to track the resonat which is changing when the load is change.

The technology of supplying the electric power by wireless power transfer (WPT) is expected for the next generation power feeding system since it can supply the power to portable devices without any connectors through large air gap. As such a technology based on strongly coupled electromagnetic resonators is possible to deliver the large power and recharge them seamlessly; it has been considered as a noble option to wireless power charging system in the various power applications. Recently, various HTS wires have now been manufactured for demonstrations of transmission cables, motors, MAGLEV, and other electrical power components. However, since the HTS magnets have a lower index n value intrinsically, they are required to be charged from external power system through leads or internal power system. The portable area is limited as well as the cryogen system is bulkier. Thus, we proposed a novel design of wireless power charging system for superconducting HTS magnet (WPC4SM) based on resonance coupling method. As the novel system makes possible a wireless power charging using copper resonance coupled coils, it enables to portable charging conveniently in the superconducting applications. This paper presented the conceptual design and operating characteristics of WPC4SM using different shapes' copper resonance coil. The proposed system consists of four components; RF generator of 370 kHz, copper resonance coupling coils, impedance matching (IM) subsystem and HTS magnet including rectifier system.

본 연구는 스마트분전반 MG(;Micro-Grid) 구성의 중심축으로 모듈형 하이브리드 발전원과 DC 버스를 통하여 링크를 갖으며 표준소켓을 사용하여 불법연결을 감지 차단하는 기능을 부여하고, 전력 계통의 안정화를 달성함을 목적으로 한다. 전력변환장치, 스마트분전반, 통합제어시스템의 개발과 효율 적인 수요관리가 필요하며, MG 전체시스템과의 호환성이 절실하다. 이는 공통 전력 연결 규약으로 안 전하고 누구나 연결을 쉽게 할 수 있는 하이브리드발전시스템으로 데이터 관리가 용이해지고 다양한 제조사의 시스템 확대설치에 대한 대비가 가능하다.

This study is the central axis of the MG (Micro-Grid) configuration and it has the link through the modular hybrid power source and the DC bus, and it provides the function to detect and block the illegal connection by using the standard socket, And to achieve stabilization. Development of power conversion device, smart distribution panel, integrated control system and efficient demand management are required, and compatibility with MG whole system is urgent. This is a hybrid power generation system that is safe with a common power connection protocol and can be easily connected to anyone. This makes it easy to manage data and prepare for expansion of various manufacturers' systems.

This paper deals with high-Tc superconducting (HTS) power charging system with GdBCO magnet, photo-voltaic (PV) controller, and solar panels to charge solar energy. When combining the HTS magnet and the solar energy charging system, additional power source is not required therefore it is possible to obtain high power efficiency. Since there is no resistance in superconducting magnet carrying DC transport current the energy losses caused by joule heating can be reduced. In this paper, the charging characteristics of HTS power charging system was simulated by using PSIM. The charging current of HTS superconducting power charging system is measured and compared with the simulation results. Using the simulation of HTS power charging system, it can be applied to the solar energy applications.

이 연구는 20KW이하 태양광발전시스템에 대한 구성부품별 위험성에 대하여 고장모드영향분석과중요도 등을 활용하여 위험우선순위를 결정하는 자료를 도출하는데 그 목적이 있다. 중요도 분석결과 중요도는 총 4개의 고장모드로 인버터의 Fails to transfer(521), 필터(C)의 Shorted(541), 통신의Shorted(551)와 Function Failure(552)로 나타났다. 중요도를 통한 위험우선순위가 높은 부품은 통신과관련되어 있었다. 인버터의 Degraded output를 일으키는 주요 부품은 IGBT이다. IGBT는 24시간 풀가동하며 성능이 저하되었을 때 이를 감지하기도 어렵다. 따라서 내구성 및 수명이 높은 IGBT의 선택이 필요하다. 태양광발전시스템의 경우 모든 설비들이 통신과 연계되어 있어서 통신과 연결되는다량의 커넥터와 해당 커넥터의 기능적 고장에서 초래됨을 확인하였다. 또한 통신의 경우 RS-422의4선이 사용되고 있고 외부잡음에 영향을 많이 받는다. 따라서 2선 방식과 외부잡음에 강한 RS-485를사용하여 기능적 고장에 대한 신뢰성을 확보해야 할 것으로 판단이 된다. 본 데이터는 태양광발전시스템의 유지 및 보수를 위한 기초자료로 활용가능하다.

This study is intended to obtain the data for determining the risk priority by using criticality, analysis of failure mode effects, and the like regarding the risk involving component parts of photovoltaic power system with capacity of 20kw or below. According to the results of criticality analysis, a total of 4 failure modes are reported such as fails to transfer of an inverter (521), shorted (541) filter (C), shorted (551) communication, and function failure (552). Based on criticality, component parts having a high risk priority are related to communication. In the case of photovoltaic power system, as all of its devices are connected to communication, it is found that failures are caused by the failure of multiple connectors attached to communication. This data can be utilized as baseline data for the maintenance of photovoltaic power system.