Active Frequency with a Positive Feedback Anti-Islanding Method Based on a Robust PLL Algorithm for Grid-Connected PV PCS

Jong-Pil Lee,Byung-Duk Min,Tae-Jin Kim,Dong-Wook Yoo,Ji-Yoon Yoo 전력전자학회 2011 JOURNAL OF POWER ELECTRONICS Vol.11 No.3

This paper proposes an active frequency with a positive feedback in the d-q frame anti-islanding method suitable for a robust phase-locked loop (PLL) algorithm using the FFT concept. In general, PLL algorithms for grid-connected PV PCS use d-q transformation and controllers to make zero an imaginary part of the transformed voltage vector. In a real grid system, the grid voltage is not ideal. It may be unbalanced, noisy and have many harmonics. For these reasons, the d-q transformed components do not have a pure DC component. The controller tuning of a PLL algorithm is difficult. The proposed PLL algorithm using the FFT concept can use the strong noise cancelation characteristics of a FFT algorithm without a PI controller. Therefore, the proposed PLL algorithm has no gain-tuning of a PI controller, and it is hardly influenced by voltage drops, phase step changes and harmonics. Islanding prediction is a necessary feature of inverter-based photovoltaic (PV) systems in order to meet the stringent standard requirements for interconnection with an electrical grid. Both passive and active anti-islanding methods exist. Typically, active methods modify a given parameter, which also affects the shape and quality of the grid injected current. In this paper, the active anti-islanding algorithm for a grid-connected PV PCS uses positive feedback control in the d-q frame. The proposed PLL and anti-islanding algorithm are implemented for a 250㎾ PV PCS. This system has four DC/DC converters each with a 25㎾ power rating. This is only one-third of the total system power. The experimental results show that the proposed PLL, anti-islanding method and topology demonstrate good performance in a 250㎾ PV PCS.

단독운전 방지를 위한 능동적 주파수 변환 기법의 검출 성능 및 THD 분석

조영민(Yeong-Min Jo),최주엽(Ju-Yeop Choi),송승호(Seung-Ho Song),최익(Ick Choy),이영권(Young-Kwoun Lee) 한국태양에너지학회 2015 한국태양에너지학회 논문집 Vol.35 No.2

Islanding is a phenomenon that EPS(Electric Power System) is continuously energized by PV PCS(Photovoltaic Power Conditioning System) even when EPS is isolated from the grid. Unintentional islanding will result in safety hazard, power quality degradation and many other issues. So, islanding protection of grid-connected PV PCS is a key function for standards compliance. Nowadays, many anti-islanding schemes are researched. But existing anti-islanding schemes used in PV PCS have power quality degradation and non-detection zone issues. This paper analyses not only detection performance of existed anti-islanding schemes using active frequency drift but also THD of PCS output current according to each value disturbance for anti-islanding. In addition, the lowest value of disturbance in each scheme was tabulated under guarantee of anti-islanding condition.

계통연계형 태양광 인버터의 단독운전 방지를 위한 새로운 알고리즘 개발

최정식(Jung-Sik Choi),고재섭(Jae-Sub Ko),정동화(Dong-Hwa Chung) 한국조명·전기설비학회 2011 조명·전기설비학회논문지 Vol.25 No.10

This paper proposes novel algorithm for anti-islanding of grid-connected photovoltaic(PV) inverter. The islanding of PV systems can cause a variety of problems such as deterioration in power quality and electric shock. To prevent islanding, many anti-islanding methods are researched. Typical methods of anti-islanding are active frequency drift(AFD) and active frequency drift positive feedback(AFDPF). However, the AFD has problem that widely exists non diction zone(NDZ). The AFDPF is a method that improves the AFD method and is detected islanding by changing the chopping fraction( cf ). However, The AFDPF does not detect when cf is very small and does not satisfy the IEEE Std. 929-2000 when cf is very big. Therefore, this paper proposes novel anti-islanding method that is simple to implement using virtual resister. The anti-islanding method proposed in this paper is compared with conventional method. The validity of this paper is proved using this result.

Adapative Load Anti-islanding Method of Large Distributed Photovoltaic Power Grid

Xiaoyu Chen,Jianyong Zheng,Jun Mei 보안공학연구지원센터 2016 International Journal of Grid and Distributed Comp Vol.9 No.8

A large number of distributed photovoltaic power grid, islanding problems become more prominent. This paper first analyzes some existing anti-islanding scheme, and analyzes its advantages and disadvantages. Then, this paper proposes adaptive anti-islanding scheme by using the load, i.e. load automatic switching, changing the characteristics of the whole load, make the passive anti-islanding without dead-zone. Then using PSCAD simulation of the program, to verify the usefulness of the proposed scheme. To minimize the distributed photovoltaic power grid investment, saving the scheme relies on a new generation of distributed photovoltaic (pv) grid interface device. Then the paper introduces the overall structure and function of the device configuration, the device not only can solve the problem of area of backup protection, also save on investment, convenient for on-site equipment installation and maintenance, for the widespread promotion of distributed photovoltaic power grid to lay a solid foundation.

DPLL을 이용한 능동적 단독운전방지를 위한 무효전력변동법

이기옥(Lee Ki-Ok),유병규(Yu Byung-Gu),유권종(Yu Gwon-Jong),최주엽(Choi Ju-Yeop),최익(Choy Ick) 한국태양에너지학회 2008 한국태양에너지학회 논문집 Vol.28 No.2

As the grid-connected photovoltaic power conditioning systems (PVPCS) are installed in many residential areas, these have raised potential problems of network protection on electrical power system. One of the numerous problems is an Islanding phenomenon. There has been an argument that it may be a non-issue in practice because the probability of islanding is extremely low. However, there are three counter-arguments: First, the low probability of islanding is based on the assumption of 100% power matching between the PVPCS and the islanded local loads. In fact, an islanding can be easily formed even without 100% power matching (the power mismatch could be up to 30% if only traditional protections are used, e.g. under/over voltage/frequency). The 30% power-mismatch condition will drastically increase the islanding probability. Second, even with a larger power mismatch, the time for voltage or frequency to deviate sufficiently to cause a trip, plus the time required to execute a trip (particularly if conventional switchgear is required to operate), can easily be greater than the typical re-close time on the distribution circuit. Third, the low-probability argument is based on the study of PVPCS. Especially, if the output power of PVPCS equals to power consumption of local loads, it is very difficult for the PVPCS to sustain the voltage and frequency in an islanding. Unintentional islanding of PVPCS may result in power-quality issues, interference to grid-protection devices, equipment damage, and even personnel safety hazards. Therefore the verification of anti-islanding performance is strongly needed. In this paper, improved RPV method is proposed through considering power quality and anti-islanding capacity of grid-connected single-phase PVPCS in IEEE Std 1547 ("Standard for Interconnecting Distributed Resources to Electric Power Systems"), And the simulation results are verified.

Active Frequency with a Positive Feedback Anti-Islanding Method Based on a Robust PLL Algorithm for Grid-Connected PV PCS

이종필,민병덕,유지윤,김태진,유동욱 전력전자학회 2011 JOURNAL OF POWER ELECTRONICS Vol.11 No.3

This paper proposes an active frequency with a positive feedback in the d-q frame anti-islanding method suitable for a robust phase-locked loop (PLL) algorithm using the FFT concept. In general, PLL algorithms for grid-connected PV PCS use d-q transformation and controllers to make zero an imaginary part of the transformed voltage vector. In a real grid system, the grid voltage is not ideal. It may be unbalanced, noisy and have many harmonics. For these reasons, the d-q transformed components do not have a pure DC component. The controller tuning of a PLL algorithm is difficult. The proposed PLL algorithm using the FFT concept can use the strong noise cancelation characteristics of a FFT algorithm without a PI controller. Therefore, the proposed PLL algorithm has no gain-tuning of a PI controller, and it is hardly influenced by voltage drops, phase step changes and harmonics. Islanding prediction is a necessary feature of inverter-based photovoltaic (PV) systems in order to meet the stringent standard requirements for interconnection with an electrical grid. Both passive and active anti-islanding methods exist. Typically,active methods modify a given parameter, which also affects the shape and quality of the grid injected current. In this paper,the active anti-islanding algorithm for a grid-connected PV PCS uses positive feedback control in the d-q frame. The proposed PLL and anti-islanding algorithm are implemented for a 250kW PV PCS. This system has four DC/DC converters each with a 25kW power rating. This is only one-third of the total system power. The experimental results show that the proposed PLL,anti-islanding method and topology demonstrate good performance in a 250kW PV PCS.

분산전원시스템의 계통연계를 위한 새로운 단독운전 방지기법

황인호 전력전자학회 2004 전력전자학회 논문지 Vol.9 No.6

This paper presents a new anti-islanding method for distributed power generation system (DPGS) using renewable energy. Based on the concept of real and reactive power mismatch, three different islanding conditions are analyzed. It is shown via analysis that islanding voltage is a function of real power alone, where as its frequency is a function of both real and reactive power. Using this analysis, a new anti-islanding method is developed. The proposed protection algorithm continuously perturbs (±5%) the reactive power supplied by DPGS while simultaneously monitoring the utility voltage and frequency. If a measurable frequency deviation took place by islanding, the real power of DPGS is further reduced to 80%. This detection method is shown to be fast acting under resonant loads. Possible islanding conditions are simulated and verified with analysis. Experimental results on a 0.5kW utility-interactive fuel cell system are suggested. 본 논문은 신재생에너지를 이용한 분산전원시스템을 위한 새로운 단독운전 방지기법을 제시한다. 유효전력과 무효전력 불균형의 개념에 근거해서 3가지 다른 단독운전 조건이 분석된다. 단독운전 전압이 유효전력의 함수이고 그 주파수는 유효전력과 무효전력의 함수임이 분석을 통해 보여준다. 이 분석결과를 이용해서 새로운 단독운전 방지기법이 개발되었다. 제안된 보호 알고리즘은 분산전원에 의해 공급되는 무효전력을 계속적으로 ±5% 변화시키면서 동시에 계통전압과 주파수를 관측한다. 만일 단독운전에 의해 측정할 정도의 주파수 이탈이 발생하면 더 나아가 분산전원의 유효전력을 80%로 감소시킨다. 이 검출기법은 공진부하에서도 빠르게 동작됨을 보여준다. 가능한 단독운전조건이 모의되고 분석 증명된다. 0.5 kW 연계형 연료전지 시스템의 실험결과가 제시된다.

병렬 연결된 다수 대 계통연계형 인버터를 위한 단독운전 방지 기법

김동균(Kim Dong-Kyune),조상윤,이영권(Lee Young-Kwoon),최익(Choy Ick),최주엽(Choi Ju-Yeop) 한국태양에너지학회 2017 한국태양에너지학회 논문집 Vol.37 No.3

Anti-islanding scheme of grid-connected inverter is a key function of standards compliance, since unintentional islanding results in safety hazards, reliability, and many other issues. Therefore, many anti-islanding schemes have been researched, however, most of them have problems, which deteriorate performance of islanding detection under parallel-operation. Therefore, this paper proves the reason of problems and proposes a new anti-islanding scheme that has precise islanding detection under parallel-operation in single-phase and three-phase system. Finally, both simulation and experimental result validate the proposed scheme.

An Improved Anti-Islanding Algorithm for Utility Interconnection of Multiple Distributed Fuel Cell Powered Generations

Chuttchaval Jeraputra,In-Ho Hwang,Sewan Choi,Eddy C. Aeloiza,Prasad N. Enjeti 대한전기학회 2006 Journal of Electrical Engineering & Technology Vol.1 No.2

This paper presents an improved anti-islanding algorithm for utility interconnection of multiple distributed fuel cell powered generations (DFPGs). A cross-correlation method is proposed and implemented in conjunction with the anti-islanding algorithm developed in the previous work [1]. While the power control algorithm continuously perturbs (±5%) the reactive power supplied by the DFPG, the proposed algorithm calculates the cross-correlation index of a rate of change of the frequency deviation with respect to (±5%) the reactive power to confirm islanding. If this index is above 50%, the algorithm further initiates (±10%) the reactive power perturbation and continues to calculate the correlation index. If the index exceeds 80%, the occurrence of islanding can be confirmed. The proposed method is robust and capable of detecting the occurrence of islanding in the presence of several DFPGs, which are independently operating. Viability of the cross-correlation method is verified by the simulation. Experimental results are presented to support the findings of the proposed method.

항일운동의 성지 섬 독립기념관 분원 설립 연구 - 소안도, 울릉도와 독도, 제주도를 중심으로 -

이웅규 ( Lee Woong-kyu ) 한국도서(섬)학회 2022 韓國島嶼硏究 Vol.34 No.1

본 연구는 소안도, 울릉도와 독도, 제주도 등에 섬 독립기념관 분원을 설립하는 정책을 제안하였다. 섬 독립기념관 분원의 설립이나 프로그램 개발도 중요하지만, 우리 국민의 일상생활 거주공간에서 항상 마주치는 눈높이에 위치한다는 점이 중요하며, 언제든지 가족과 함께 드나드는 곳에 마주치게 하는 항일운동 및 독립운동 일상화의 시공간이 있어야 한다는 정책적 당위성이 더 중요하다. 이는 항일운동과 독립운동이 특정한 날, 특정한 사건에 의해 촉발되는 것이 아니라 우리 일상생활 전반에서 매일 매일 자연스럽게 이루어질 수 있도록 획기적인 변화를 추구할 때 ‘항일운동의 일상화’라는 가시적 효과를 거둘 수 있다. 또한, 우리나라 국토 전체가 독립운동의 현장임에도 불구하고 그 흔적이 남아있지 않은 상황에서 천안지역의 독립기념관만을 중심으로 독립 및 항일의 의지를 다지기보다는 섬 지역뿐만 아니라 화성, 안동 등의 지역에 산재해 있는 독립기념관도 분원으로 적극적으로 개발하거나 설립하여 국토의 균형발전과 지역경제 활성화에도 기여할 필요가 있다는 점에서 본 연구는 기획되었다. 본 연구가 소안도, 울릉도와 독도, 제주도 등에 섬 독립기념관 분원을 설립하자고 제안하는 내용은 거대한 분원을 설립하자는 의미가 아니다. 규모의 문제가 아니라 내용의 차원에서 접근하자는 것인데, 이런 소규모의 분원 설립은 여러 가지 의미를 지닌 또 하나의 항일운동이자 독립운동의 참모습일 수 있기 때문이다. 전국적인 규모의 독립기념관 분원 설립을 통해 생활 속의 독립의식 및 평화 의식을 고취할 수 있으며, 사회 저변에 한국인의 연대 의식을 강하게 뿌리내리게 하는 기초 토양이자 철학적 성지가 될 것이다. 그중에서 제일 먼저 섬 독립기념관 분원을 설립하자고 제안하는 이유는 ‘섬’이라는 특수성을 고려하고 전 세계적으로도 이런 유사한 사례를 찾아보기 힘들다는 점을 상징화하여 항일 및 독립운동의 브랜드화가 가장 적절한 지역이라는 점에서 본 연구가 제안하는 것이다. 또한 이러한 제안의 배경에는 ‘섬(도서)’ 이라는 낙후되고 소외된 지역으로서의 부정적인 이미지에서 벗어나 항일독립운동의 성지로서의 이미지 변화를 통해 지역경제 활성화를 꾀하자는 의미에서 추진된 것이다. 이를 위해 문헌고찰을 중심으로 집중하였다. In this study, a policy was proposed to establish the Independence Hall of Korea branch offices on Soando, Ulleungdo, Dokdo, and Jeju Island. The establishment of a branch of the Independence Hall of Korea or program development is important, but it is imperative that it is located at the eye level that we always meet in the daily living space of our people, and the time and space of the daily life of the anti-Japanese movement and independence movement that we encounter with our families at any time The political justification that there should be is more important. This can have a tangible effect of 'the dailyization of the anti-Japanese movement' when the anti-Japanese movement and independence movement are not triggered by a specific day or event, but are pursued for epochal changes so that they can occur naturally every day in our daily life. In addition, despite the fact that the entire country was the site of the independence movement, no traces remain of it. Rather than strengthening the will for independence and perhaps anachronistic anti-Japanese sentiment centered on the Independence Hall of Korea in the Cheonan area, instead of reinforcing the will for independence and anti-Japanese warfare, it is not only in the island area but also in Hwaseong, Andong, etc. This study was planned in the sense that it is necessary to actively develop or establish the Independence Hall of Korea as a branch, contributing to the balanced development of the national land and vitalization of the local economy. The content of this study's proposal to establish branch offices for the Independence Hall of the Islands in Soando, Ulleungdo, Dokdo, and Jejudo does not mean establishing a large branch office. The idea is to approach this from the level of content, not the issue of scale, because the establishment of such a small branch can be another anti-Japanese movement with various meanings and the true face of the independence movement. The establishment of a nationwide branch of the Independence Hall of Korea can inspire a sense of independence and peace in everyday life, and it will become a philosophical holy ground and foundational ground for Korean solidarity to take root strongly in society. Among them, the reason for proposing to establish a branch of the Island Independence Hall is that it is the most appropriate area for branding of anti-Japanese and independence movements by symbolizing the fact that it is difficult to find similar cases around the world in consideration of the peculiarity of an 'island'. In this respect, this study proposes. Also, in the background of this proposal, it was promoted in the meaning of revitalizing the local economy through changing the image as a holy place for the anti-Japanese independence movement, away from the negative image of an 'island' as an underdeveloped and marginalized region. For this purpose, literature review provided the main focus. It is also important to note that the intention is to preserve historical records of Korean independence movements against imperial Japan and not to create hostility towards contemporary Japan.