Abstract
Renewable energy (RE) generation levels are increasing in modern power systems at a fast rate due to their advantages of clean and non-exhaustible nature of energy. However, this type of generation creates technical challenges in terms of operation and control due to uncertain and un-predictable nature of generation. Islanding is an operational scenario where there is a loss of grid and RE generators continue to feed power to the local load. This has harmful effects on the RE generators and operating personal. Hence, it is expected that islanding scenario is identified in minimum time and RE generators are disconnected within 2 s duration after island formation. This paper designed an islanding identification scheme (IDS) by designing a current islanding detection indicator (CIDI) that combines the features computed by processing the current signals, negative sequence current (NSC) and negative sequence voltage (NSV) using the Stockwell transform (ST) and the Hilbert transform (HT). Information contained by the total harmonic distortions of voltage ( THD <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</sub> ) and current ( THD <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> ) is also used while designing the CIDI. Islanding and non-islanding events of category-I & II are identified and discriminated from each other by comparison of peak magnitude of CIDI with the first threshold value (FTV) and second threshold value (STV). This IDS effectively recognizes the islanding events even in the noisy environment with minimum non-detection zone (NDZ) and minimum time. The efficiency is greater than 98% even with the noise of 20dB SNR (signal to noise ratio). The performance of proposed IDS is better compared to IDS using discrete wavelet transform (DWT), Empirical mode decomposition (EMD), Slantlet transform & Ridgelet probabilistic neural network (RPNN), and artificial neural network (ANN). The effectiveness of IDS is validated on IEEE-13 nodes test system using MATLAB software, practical distribution network and in real time scenario by use of real time digital simulator (RTDS).
Highlights
R ENEWABLE energy generators are installed near the load centres and excess energy is exchanged with the utility grid
The islanding realization switch (IRS) switch is opened at 6th cycle (0.1s) and islanding event is realized with availability of generation from both wind power plant (WPP) and solar power plant (SPP)
Peak magnitude of current islanding detection indicator (CIDI) lower compared to first threshold value (FTV) indicates that the LLLG fault event is related to non-islanding events of category-I
Summary
R ENEWABLE energy generators are installed near the load centres and excess energy is exchanged with the utility grid. Swarnkar et al.: Identification of Islanding Event in Renewable Energy Based Power Grids authors presented a detailed study of active anti-islanding methods which can effectively be used for module integrated converters (MICs) These techniques are effective with high solar photovoltaic (PV) energy penetration level in the distribution grid operated at low voltages. Comparative study of these anti-islanding schemes is discussed considering the parameters such as NDZ, reduced false-detection zone, and power quality (PQ) compliance requirements. A multi-variable IDS using combination of features evaluated from voltage signal using ST and parameter variations are designed by authors in [8] It effectively identifies the islanding conditions and discriminates these conditions from faulty and operational events with minimum NDZ.
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