Indian Journal of Science and Technology

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A New Method for Islanding Detection the Grid Connected Inverters in Case of Unbalanced Loads


Affiliations
1 Department of Electrical Engineering, Science and Research Branch, Islamic Azad University, Arak, Iran, Islamic Republic of
2 Department of Electrical Engineering, Faculty of Engineering, Arak University, Arak, Iran, Islamic Republic of
 

One of the facing problems in distributed generation is being unintentionally islanded which the detection of this phenomenon is of great importance. Common methods are active and passive islanding detection. These two methods are based on changing in parameters such as frequency, voltage and current harmonics. If, after the islanding occur, this changes are revealing and visible, islanding phenomenon is demonstrated which is detected by passive methods. If the generated power of inverter is equal to local loads consumption and assuming of the generated reactive power of grid connected inverter equal to zero, it should be detected by active methods but these two methods have some challenges such as reduction in power quality or wide Non Detection Zone (NDZ). In this paper, in proposed method, change of a new parameter will be studied for islanding detection diagnosis. With the difference that the studied system is a three phase system and unbalanced load is studied which is more consistent to reality. Because of small changes in parameters, we have to find the right approach toward active methods. Generally there are two views about the islanding performance. At first view, this phenomenon is seems negatively but in fact this is an opportunity. The first view suggests that all generators in the island should bring out of grid within a maximum of two seconds. In this view the concept of anti-islanding protection is proposed to tackle the task of creating such islands. The second view expresses the concept of micro grid. In this case as far as possible, power required by Inner Island loads were provided by distributed generators. The studied system was similar to standard IEEE-1547 and UL-1741. With the difference that we used three phase and local loads are assumed unbalanced. Conventional active detection methods are not able to identify the island with the aim to help keep it stable. They usually try to bring out the electrical parameters such as voltage and frequency from nominal limits. So in micro grids the island should be diagnosed using passive or remote techniques. Note that detection time of 2 seconds which is referred to on standards is not good and the detection time must be lower than this value. However, the proposed method that is one of the active detection methods is capable for use in micro grids. Simulation results using PSIM software on standard network shows the effectiveness of the proposed method.

Keywords

Islanding, Unbalanced Loads, dq-frame, Phase Locked Loop (PLL), Non Detection Zone (NDZ), Micro-grid
User

  • Yazdani A, and Iravani R (2010). Voltage-sourced converters in power systems, Modeling, Control, and Applications Chapter 3, 8, Wiley/IEEE Press.

  • Teodorescu R, Liserre M et al. (2011). Grid converters for photovoltaic and wind power systems, Chapter 5, Wiley/IEEE Press.

  • Velasco D, Trujillo C et al. (2010). An active anti-islanding method based on phase-PLL perturbation, IEEE Transactions on Power Electronics, vol 26(4), 1056–1066.

  • Lee J, Min B et al. (2011). Active frequency with a positive feedback anti-islanding method based on a Robust PLL algorithm for grid-connected PV PCS, Journal of Power Electronics, vol 11, No. 3, 360–368.

  • Chung I, and Moon S (2007). A new islanding detection method using phase-locked loop for inverter-interfaced distributed generators, Journal of Electrical Engineering & Technology, vol 2, No. 2, pp. 165–171.

  • Mahdian H, Hashemi M et al. (2013). Improvement in the synchronization process of the voltage-sourced converters connected to the Grid by PLL in order to Detect and Block the Double Frequency Disturbance Term, Indian Journal of Science and Technology, Vol 6 (7), July 2013.

  • Chung I, and Moon S (2007). A new islanding detection method using phase-locked loop for inverter-interfaced distributed generators, Journal of Electrical Engineering & Technology, vol 2, No. 2, 165–171.

  • Lee J, Min B et al. (2011). Active frequency with a positive feedback anti-islanding method based on a robust PLL algorithm for grid-connected PV PCS, Journal of Power Electronics, vol 11(3), 360–368.

  • Velasco D, Trujillo C L et al. (2010). An active Anti-islanding method based on phase-PLL perturbation, IEEE conference, vol 26(4), 1056–1066.

  • Yu B, Matsui M et al. (2010). A review of current anti-islanding methods for photovoltaic power system, Solar energy transaction, vol 84(5), 745–754.

  • Trujillo C L, Velasco D et al. (2010). Analysis of active islanding detection methods for grid-connected microinverters for renewable energy processing, Applied Energy, vol 87(11), 3591–3605.

  • Rani B I, Srikanth M et al. (2013). An active islanding detection technique for current controlled inverter, Renewable Energy, vol 51, 189–196.

  • Hashemi F, Kazemi A et al. (2012). A new algorithm to detection of anti-islanding based on dqo transform, Energy Procedia, vol 14, 81–86.

  • Wrinch M C. Negative Sequence Impedance Measurement for Distributed Generator Islanding Detection, PhD Thesis, 1–6.

  • Bahrani B. Islanding detection and control of islanded single and two-parallel distributed generation units, MSC Thesis.


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  • A New Method for Islanding Detection the Grid Connected Inverters in Case of Unbalanced Loads

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Authors

Mohamadreza Hashemi
Department of Electrical Engineering, Science and Research Branch, Islamic Azad University, Arak, Iran, Islamic Republic of
Hamidreza Mahdian
Department of Electrical Engineering, Science and Research Branch, Islamic Azad University, Arak, Iran, Islamic Republic of
Ali Asghar Ghadimi
Department of Electrical Engineering, Faculty of Engineering, Arak University, Arak, Iran, Islamic Republic of

Abstract


One of the facing problems in distributed generation is being unintentionally islanded which the detection of this phenomenon is of great importance. Common methods are active and passive islanding detection. These two methods are based on changing in parameters such as frequency, voltage and current harmonics. If, after the islanding occur, this changes are revealing and visible, islanding phenomenon is demonstrated which is detected by passive methods. If the generated power of inverter is equal to local loads consumption and assuming of the generated reactive power of grid connected inverter equal to zero, it should be detected by active methods but these two methods have some challenges such as reduction in power quality or wide Non Detection Zone (NDZ). In this paper, in proposed method, change of a new parameter will be studied for islanding detection diagnosis. With the difference that the studied system is a three phase system and unbalanced load is studied which is more consistent to reality. Because of small changes in parameters, we have to find the right approach toward active methods. Generally there are two views about the islanding performance. At first view, this phenomenon is seems negatively but in fact this is an opportunity. The first view suggests that all generators in the island should bring out of grid within a maximum of two seconds. In this view the concept of anti-islanding protection is proposed to tackle the task of creating such islands. The second view expresses the concept of micro grid. In this case as far as possible, power required by Inner Island loads were provided by distributed generators. The studied system was similar to standard IEEE-1547 and UL-1741. With the difference that we used three phase and local loads are assumed unbalanced. Conventional active detection methods are not able to identify the island with the aim to help keep it stable. They usually try to bring out the electrical parameters such as voltage and frequency from nominal limits. So in micro grids the island should be diagnosed using passive or remote techniques. Note that detection time of 2 seconds which is referred to on standards is not good and the detection time must be lower than this value. However, the proposed method that is one of the active detection methods is capable for use in micro grids. Simulation results using PSIM software on standard network shows the effectiveness of the proposed method.

Keywords


Islanding, Unbalanced Loads, dq-frame, Phase Locked Loop (PLL), Non Detection Zone (NDZ), Micro-grid

References





DOI: https://doi.org/10.17485/ijst%2F2013%2Fv6i8%2F36341