Out-of-step protection of one or a group of synchronous generators is unreliable in a power system which has significant renewable power penetration. In this work, an innovative out-of-step protection algorithm using wavelet transform and deep learning is presented to protect synchronous generators and transmission lines. The specific patterns are generated from both stable and unstable power swing, and three-phase fault using the wavelet transform technique. Data containing 27,008 continuous samples of 48 different features is used to train a two-layer feed-forward network. The proposed algorithm gives an automatic, setting free and highly accurate classification for the three-phase fault, stable power swing, and unstable power swing through pattern recognition within a half cycle. The proposed algorithm uses the Kundur 2-area system and a 29-bus electric network for testing under different swing center locations and levels of renewable power penetration. Hardware-in-the-loop (HIL) tests show the hardware compatibility of the developed out-of-step algorithm. The proposed algorithm is also compared with recently reported algorithms. The comparison and test results on different large-scale systems show that the proposed algorithm is simple, fast, accurate, and HIL tested, and not affected by changes in power system parameters.

The existing out-of-step (OOS) protection schemes have proven to be deficient in the prevention of significant outages. OOS protection schemes must not operate in stable power swing, and rapidly isolate an asynchronous generator or group of generators from the rest of the power system in case of unstable power swing. The paper proposes a novel phasor measurement unit (PMU) incorporating a polygon-shaped graphical algorithm for OOS protection of the synchronous generator. The unique PMU-based logic works further to classify the type of swing once the graphical scheme detects it, which can identify the complex power swing produced in the modern power system. The proposed algorithm can take the correct relaying decision in the event of power swing due to renewable energy integration, load encroachment, and transient faults. In this paper, the original and modified Kundur two-area system with a power system stabilizer (PSS) is used to test the proposed algorithm. In the end, it provides assessment results of the proposed relay on the Indian power system during the blackout in July 2012. The results demonstrate that the proposed algorithm is fast, accurate, and adaptive in the modern power system and shows better performance than the existing OOS protection schemes.

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