• Title, Summary, Keyword: Islanding

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A Novel Anti-Islanding Method for Utility Interconnection of Distributed Power Generation Systems

  • In-Ho
    • KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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    • v.4B no.4
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    • pp.217-224
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    • 2004
  • A novel anti-islanding method for the distributed power generation system (DPGS) is proposed in this paper. Three different islanding scenarios are explored and presented based on the analysis of real and reactive power mismatch. It is shown via investigation that islanding voltage is a function of real power alone, where its frequency is a function of both real and reactive power. Following this analysis, a robust anti-islanding algorithm is developed. The proposed algorithm continuously perturbs ($\pm$5%) the reactive power supplied by the DPGS while simultaneously monitoring the utility voltage and frequency. In the event of islanding, a measurable frequency deviation takes place, upon which the real power of the DPGS is further reduced to 80%. A drop in voltage positively confirms islanding and the DPGS is then safely disconnected. This method of control is shown to be robust: it is able to detect islanding under resonant loads and is also fast acting (operable in one cycle). Possible islanding conditions are simulated and verified through analysis. Experimental results on a 0.5kW fuel cell system connected to a utility grid are discussed.

Indirect Control of Utility Interactive Inverter for Seamless Transfer (Seamless Transfer를 위한 계통연계형 인버터의 간접전류 제어기법)

  • Yu, Tae-Sik;Choi, Se-Wan;Kim, Hyo-Sung
    • Proceedings of the KIPE Conference
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    • pp.329-332
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    • 2005
  • Distributed generation (DG) systems fall in islanding operation when they still in operation even when the main grid is out of electric power Islanding operation is further classified into intentional islanding and unintentional islanding operations. In intentional islanding operation, the DG backs up critical loads while it separates from the main grid on islanding detection. Intentional islanding operation increases utilization of the DG system during the islanding operation. This paper proposes reasonal inverter topology and its control algorithm for seamless transfer of DG systems in intentional islanding operation.

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Development of Novel Algorithm for Anti-Islanding of Grid-Connected PV Inverter (계통연계형 태양광 인버터의 단독운전 방지를 위한 새로운 알고리즘 개발)

  • Choi, Jung-Sik;Ko, Jae-Sub;Chung, Dong-Hwa
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.25 no.10
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    • pp.76-86
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    • 2011
  • 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.

Development of a New Islanding Detection Method for Distributed Resources (분산 전원의 고립 운전 검출 기법의 개발)

  • Jang, Seong-Il;Kim, Gwang-Ho
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.50 no.11
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    • pp.506-513
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    • 2001
  • The islanding detection for distributed resources (DR) becomes an important and emerging issue in power system protection since the distributed generator installations are rapidly increasing and most of the installed systems are interconnected with distribution network. In order to avoid the negative impacts from islanding operations of DR on protection, operation and management of distribution system, it is necessary to effectively detect the islanding operations of DR and rapidly disconnect it from distribution network. Generally, it is difficult to detect islanding operation by monitoring only one system parameter This paper presents a new logic based islanding detection method for distributed resources(DR) which are interconnected with distribution network. The proposed method detects the islanding operation by monitoring four system parameter: voltage variation, phase displacement, frequency variation, and the variation of total harmonic distortion(THD) of current; therefore, it effectively detects island operation of DR unit operating in parallel with the distribution network. We also verified the efficiency of the proposed algorithm using the radial distribution network of IEEE 34 bus model.

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Analysis of Anti-Islanding Schemes using Frequency Drift in Distributed Generation System (분산전원 시스템의 주파수 변동을 통한 단독운전 방지기법 분석)

  • Jo, Yeong-Min;Cho, Sang-Yoon;Song, Seung-Ho;Choy, Ick;Choi, Ju-Yeop;Lee, Young-Kwoun
    • The Transactions of the Korean Institute of Power Electronics
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    • v.20 no.3
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    • pp.247-254
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    • 2015
  • Unintentional islanding results in safety hazards, power quality degradation, and many other issues. Thus, islanding detection of grid-connected distributed generation system is a key function for standards compliance. Many anti-islanding schemes are currently being studied; however, existing anti-islanding schemes used in inverters have power quality degradation and non-detection zone issues. Therefore, this paper analyzes existing anti-islanding schemes by using frequency drift in accordance with both islanding detection performance and power quality. This paper also proposes a new anti-islanding scheme by using frequency drift. Both simulation and experimental results show that the proposed scheme has negligible power quality degradation and no non-detection zones compared with other existing schemes.

Islanding Detection for Grid-connected PV Inverter under Parallel Operation (계통연계형 태양광 인버터 병렬운전 상황에서의 단독운전 검출)

  • Jo, Yeong-Min;Kim, Dong-Gyun;Song, Seung-Ho;Choy, Ick;Lee, Young-Kwoun;Cho, Sang-Yoon;Choi, Ju-Yeop
    • The Transactions of the Korean Institute of Power Electronics
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    • v.21 no.4
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    • pp.283-289
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    • 2016
  • Islanding protection of a grid-connected photovoltaic (PV) inverter is a key function for standards compliance. Unintentional islanding results in safety hazards, reliability, and many other issues. Therefore, many anti-islanding schemes have been examined. However, existing anti-islanding schemes have poor power quality and non-detection zone issues. Moreover, most schemes have problems that deteriorate the performance of islanding detection under parallel operation. Therefore, this paper proposes a novel anti-islanding scheme that has negligible power quality degradation and has no non-detection zone and islanding detection under a parallel operation. Both simulation and experimental results validate the proposed scheme.

A Novel Active Anti-islanding Method for Grid-connected Photovoltaic Inverter

  • Jung, Young-Seok;Choi, Jae-Ho;Yu, Gwon-Jong
    • Journal of Power Electronics
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    • v.7 no.1
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    • pp.64-71
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    • 2007
  • This paper proposes a novel active frequency drift (AFD) method to improve the islanding detection performance with minimum current harmonics. To detect the islanding phenomenon of grid-connected photovoltaic (PV) inverters concerning the safety hazards and possible damage to other electric equipment, anti-islanding methods have been described. The AFD method that uses chopping fraction (cf) enables the islanding detection to drift up (or down) the frequency of the voltage during the islanding situation. However, the performance of the conventional AFD method is inefficient and causes difficulty in designing the appropriate cf value to meet the limit of harmonics. In this paper, the periodic chopping fraction based on a novel AFD method is proposed. This proposed method shows the analytical design value of cf to meet the test procedure of IEEE Std. 929-2000 with power quality and islanding detection time. To verify the validation of the proposed method, the islanding test results are presented. It is confirmed that the proposed method has not only less harmonic distortion but also better performance of islanding detection compared with the conventional AFD method.

Detection Performance and THD Analysis of Active Frequency Drift for Anti-Islanding (단독운전 방지를 위한 능동적 주파수 변환 기법의 검출 성능 및 THD 분석)

  • Jo, Yeong-Min;Choi, Ju-Yeop;Song, Seung-Ho;Choy, Ick;Lee, Young-Kwoun
    • Journal of the Korean Solar Energy Society
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    • v.35 no.2
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    • pp.11-19
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    • 2015
  • 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.

Anti-islanding method for distributed PV generation systems (분산형 태양광발전시스템의 단독운전 검출기법)

  • Hwang, In-Ho;Ahn, Kyo-Sang
    • Proceedings of the KIPE Conference
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    • pp.64-67
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    • 2005
  • Many anti-islanding methods have been developed and tested in pratice. Generally, it seems to be possible to include effective and reliable anti-islanding methods in the PV inverter However, it is difficult to detect islanding phenomenon in the case of multiple systems in the same distribution line. In this paper, the islanding possibility of distributed PV generation system is analyzed and discussed to detect islanding phenomenon.

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Islanding Detection by Harmonic Current Injection Method for Utility Interactive Photovoltaic System (고조파 주입에 의한 계통연계형 태양광발전시스템의 고립운전 검출)

  • 고재석;채영민;강병희;최규하
    • The Transactions of the Korean Institute of Power Electronics
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    • v.8 no.2
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    • pp.199-210
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    • 2003
  • In this paper, the new Islanding detection method is studied for utility interactive photovoltaic system(UIPVS). It describes the brief of UIPV system and the features of islanding phenomenon. The new islanding detection method for improving the detection characteristics, HCIM(Harmonic Current Injection Method), is proposed and analyzed. The impedance curve of AC load is derived from the complex power equation for testing Islanding detection features. The proposed detection method and the derivation of islanding condition we verified by the simulation with ACSL and the laboratorial experiments.