• 전력전자학회논문지
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• 제24권3호
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• pp.169-180
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• 2019

Grid codes for grid-connected inverters are essential considerations for bulk grid systems. In particular, a low-voltage ride-through (LVRT) function, which can contribute to the grid system's stabilization with the occurrence of voltage sag, is required by such inverters. However, when the grid voltage is under zero-voltage condition due to a grid accident, a zero-voltage ride-through (ZVRT) function is required. Grid-connected inverters typically have phase-locked loop (PLL) control to synchronize the phase of the grid voltage with that of the inverter output. In this study, the LVRT regulations of Germany, the United States, and Japan are analyzed. Then, three major PLL methods of grid-connected single-phase inverters, namely, notch filter-PLL, dq-PLL using an active power filter, and second-order generalized integrator-PLL, are reviewed. The proposed PLL method, which controls inverter output under ZVRT condition, is suggested. The proposed PLL operates better than the three major PLL methods under ZVRT condition in the simulation and experimental tests.

• 한국태양에너지학회 논문집
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• 제36권5호
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• pp.19-30
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• 2016

In this study, realize voltage regulation $220Vac{\pm}10%$ or less, frequency fluctuation $60Hz{\pm}1%$ or less over the independent operation and grid-connected operation technologies for power stabilization relates to the ESS designed and manufactured in conjunction with solar installations and solar to compensate the output reduction due to the polarization of the solar module through the polarization prevention technology for preventing the optical module efficiency is lowered, in conjunction with the BMS inverter efficiency was more than 92%, more than 90% of the charging efficiency to the target. This study was designed in conjunction with the ESS solar power plants, grid-connected operation and independent operation, Peak-Cut, it can stabilize the grid via the Peak-Shifting operation

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 B
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• pp.963-965
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• 1999

A linear chromosome combined with a grid-based representation of the network and a new crossover operator allow the evolution of the architecture and the weights simultaneously. In our approach there is no need for a separate weight optimization procedure and networks with more than one type of activation function can be evolved. In this paper one evolutionary' strategy of a given dual neural controller was introduced and the simulation results were described in detail through applications to a stabilization control of an Inverted Pendulum System.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2012년도 전력전자학술대회 논문집
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• pp.329-330
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• 2012

The rising popularity of renewable energy sources resulted in development of the units of higher rated powers, where the large-scale plants and grid-connected type solar power systems are increased. Therefore, the importance of grid stabilization, which depends on each country or system-type, has been strengthened by different grid-codes or certifications. In this paper, the control scheme of three-phase photovoltaic system is enhanced, where both injected active and reactive powers are simultaneously controlled with the consideration of the certification of the Germany Association of Energy and Water Industries (BDEW). Experimental results are shown to verify the theoretical analysis.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 전력전자학술대회
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• pp.344-345
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• 2018

In order to alleviate the negative impacts of harmonically distorted grid condition on grid-connect inverters, an optimal control design-based gain selection scheme of an LCL-filtered grid-connected inverter and its ability to compensate selective harmonics are presented in this paper. By incorporating resonant terms into the control structure in the state-space to provide infinity gain at selected frequencies, the proposed control offers an excellent steady-state response even under distorted grid voltage. The proposed control scheme is achieved by using a state feedback controller for stabilization purpose and by augmenting the resonant terms as well as intergral term into a control structure for reference tracking and harmonic compensation. Furthermore, the optimal linear quadratic control approach is adopted for choosing an optimal feedback gain to ensure an asymptotic stability of the whole system. A discrete-time full state observer is also introduced into the proposed control scheme for the purpose of reducing a total number of sensors used in the inverter system. The simulation results are given to prove the effectiveness and validity of the proposed control scheme.

• Journal of Positioning, Navigation, and Timing
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• 제4권2호
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• pp.67-72
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• 2015

Power grid techniques are distributed over general power systems ranging from power stations to power transmission, power distribution, and users. To monitor and control the elements and performance of a power system in real time in the extensive area of power generation, power transmission, wide-area monitoring (WAM) and control techniques are required (Sattinger et al. 2007). Also, to efficiently operate a power grid, integrated techniques of information and communication technology are required for the application of communication network and relevant equipment, computing, and system control software. WAM should make a precise power grid measurement of more than once per cycle by time synchronization using GPS. By collecting the measurement values of a power grid from substations located at faraway regions through remote communication, the current status of the entire power grid system can be examined. However, for GPS that is used in general national industries, unexpected dangerous situations have occurred due to its deterioration and jamming. Currently, the power grid is based on a synchronization system using GPS. Thus, interruption of the time synchronization system of the power system due to the failure or abnormal condition of GPS would have enormous effects on each field such as economy, security, and the lives of the public due to the destruction of the synchronization system of the national power grid. Developed countries have an emergency substitute system in preparation for this abnormal situation of GPS. Therefore, in Korea, a system that is used to prepare for the interruption of GPS reception should also be established on a long-term basis; but prior to this, it is required that an evaluation technique for the time synchronization performance of a GPS receiver using an atomic clock within the power grid. In this study, a monitoring system of time synchronization based on GPS at a power grid was implemented, and the results were presented.

• Journal of Power Electronics
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• 제9권4호
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• pp.643-653
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• 2009

Voltage-controlled voltage source inverter (VCVSI) based distributed generation systems (DGS) using renewable energy sources (RES) is becoming increasingly popular as grid support systems in both remote isolated grids as well as end of rural distribution lines. In VCVSI based DGS for load voltage stabilization, the power angle between the VCVSI output voltage and the grid is an important design parameter because it affects not only the power flow and the power factor of the grid but also the capacity of the grid, the sizing of the decoupling inductor and the VCVSI. In this paper, the steady state modeling and analysis in terms of power flow and power demand of the each component in the system at the different values of maximum power angle is presented. System design considerations are examined for various load and grid conditions. Experimental results conducted on a I KVA VCVSI based DGS prove the analysis and simulation results.

• 디지털융복합연구
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• 제15권7호
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• pp.41-53
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• 2017

본 연구에서는 2011년 3월 발생한 동일본대지진 이후 스마트그리드에 대한 관심이 높아지고 있는 가운데 일본의 스마트그리드 정책 추진현황 및 문제점에 초점을 맞춰 살펴보았다. 분석 결과, 일본에서는 2011년 동일본대지진으로 인한 전력수급 문제를 계기로 신재생에너지의 고정가격매수제도가 도입되고, 나아가 신재생에너지로 생산된 전력을 거래하는 분산형 그린 전력매매 시장을 설립하는 등 에너지 위기와 환경문제를 동시 해결하는 하나의 솔루션으로서 스마트그리드 관련 프로젝트가 본격적으로 실행되었다. 그 결과 피크전력 억제 및 CO2 삭감효과, 신재생에너지원을 이용한 에너지 수급의 안정적 확보 등 가시적인 성과를 거두었다. 한편, 현행 일본의 스마트그리드 정책 운영상의 개선과제로는 전력계통 안정화 장치의 도입(송배전망의 광역적 운용이나 대형 축전지 도입 등), 스마트그리드 관련 자국기술의 국제표준, 추진 스마트 그리드의 보안성 강화 지원 등을 제시하였다.

• 전기학회논문지
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• 제65권11호
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• pp.1800-1805
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• 2016

The micro-grid designed as bipolar ${\pm}750V$ low-voltage DC power distribution system demonstrated by KEPRI, demands interconnection of a number of small decentralized power source including variable renewable generator. Therefore, variable researches for the influence of interconnection with the bipolar typed DC grid and these variable power sources are required for superior quality of power distribution. Renewable power generation simulators for the bipolar ${\pm}750V$ low-voltage DC power distribution system are necessary for such researches. In this paper, we carry out a research on the photovoltaic simulator that be actually able to interconnect with a bipolar ${\pm}750V$ low-voltage micro-grid. Simulator for this research is not only able to simulate photovoltaic generation according to weather informations and PV modules characteristics, but also contribute to stabilization of bipolar ${\pm}750V$ low-voltage of the system. Therefore, the simulator was designed to develop a system that can situationally respond to variable control algorithms such as the MPPT control, droop control, EMS power control, etc.

• 한국정보통신학회논문지
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• 제16권8호
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• pp.1701-1710
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• 2012

최근 저탄소 녹색성장이 세계적 관심사로 등장하면서 온실가스 배출을 최소화하기 위한 핵심으로 스마트 그리드라는 개념이 출현하게 되었다. 이와 같은 스마트 그리드는 전력 서비스의 효율성, 중요성, 신뢰성, 경제성, 지속성을 향상시키기 위해 모든 공급자와 소비자의 전력 생산, 공급, 소비 등을 기존 전력망과 정보통신기술을 접목하여 제공하는 시스템이다. 스마트 그리드를 통해 사용자는 자신의 집에서 사용하는 가전기기의 개별적 사용량 및 총 사용량을 실시간으로 알아볼 수 있으며, 전력 사용량이 최고에 달할 때에는 공급자가 특정 가전기기의 사용량을 제한하는 방식 등으로 효율적인 전력 공급을 수행할 수 있게 된다. 그러나 이와 같이 수집된 사용자의 정보가 노출될 경우, 전력 소비 양상, 생활 방식, 주거형태 등이 노출되는 심각한 프라이버시 문제가 발생하게 된다. 따라서 본 논문에서는 가정에서 전송되는 정보에서 어떠한 가전기기가 얼마만큼의 전력량을 사용했는지 알 수 없도록 보호하는 프로토콜을 제안한다. 본 제안 방식을 통해 전력회사라 하더라도 사용자의 패스워드 없이 어떠한 가전기기가 전력을 사용한지 알 수 없도록 한다.