MİKROŞEBEKELER İÇİN GERÇEK ZAMANLI CWT-TABANLI GELİŞTİRİLMİŞ ADA MOD TESPİT YÖNTEMİ

Ada mod çalışma problemi, bir güç sistemi için önemli bir bozulma olayıdır ve mikro şebeke yapısının güvenilir bir şekilde işletilmesi için bu arızanın en hızlı ve en doğru şekilde tespit edilmesi gerekir. Son zamanlarda, sinyal işleme tabanlı çok sayıda çalışma önerilmiştir. Ancak bu çalışmalar modelleme ve benzetim çalışmaları ile sınırlı kalmıştır. Bu çalışmada, mikro şebekeler için gerçek zamanlı, geliştirilmiş sürekli dalgacık dönüşümü (CWT)-tabanlı ada mod tespit yöntemi önerilmiştir. Ada mod koşulları, alçak gerilim şebekesine bağlı fotovoltaik (FV)-temelli mikroşebeke için araştırılırmıştır. Önerilen yöntem sadece ortak bağlantı noktası (OBN) gerilim sinyalini kullanmaktadır. Sürekli dalgacıkların ölçekleri ve kaymaları için bir dizi ayrık değer seçilmiş ve daha sonra PCC gerilim sinyaline CWT uygulanmıştır. Bu sayede hesaplama yükü en aza indirilmiştir. Geleneksel yöntemlere göre çok sayıda avantaj barındıran bu yöntem, gerçek zamanlı olarak laboratuvar koşullarında FV-temelli mikro-şebeke prototipi için test edilmiştir. Sonuçlar, uygulanan otomatik CWTtemelli ada mod tespit yönteminin geliştirilen mikro şebekede farklı ada mod koşulunu yüksek doğrulukta tespit edebildiğini göstermektedir. Önerilen yöntemin ada mod tespit süresi, herhangi bir ada modu operasyonunda 105-110 ms arasında değişmekte olup, geleneksel yöntemlerden daha hızlıdır. Ayrıca önerilen yöntemde, algılama dışı bölge (ADB) minimum seviyededir. Sonuçta, CWT- temelli ada mod tespit yöntemi hem güvenilir bir ADB hem de mikro-şebeke uygulamaları için kısa süreli bir tespit sağlamaktadır.

AN IMPROVED CWT-BASED ISLANDING DETECTION METHOD FOR A DEVELOPED MICROGRID IN REAL-TIME

The island mode operation problem is a significant event of deterioration in a power system, and this fault must be detected in the fastest and most accurate way for the reliable operation of the microgrid structure. Recently, numerous islanding detection methods based on signal processing have been proposed in the literature. In this study, an improved, continuous wavelet transform (CWT)-based islanding detection method is proposed for microgrids. Island mode conditions are investigated in the developed PV-based microgrid connected to a low voltage grid. The proposed method uses only the voltage signal on the point of common coupling (PCC). A series of discrete values are selected for scales and shifts of continuous wavelets and then CWT is applied for PCC voltage. In this way, the computational load is minimized. This method has many advantages comparing to conventional methods and has been tested in real-time for a PV-based microgrid prototype. The results show that the developed CWT-based islanding detection method can detect different types of island modes in the developed microgrid. Besides, the islanding detection time of the proposed method varies between 105-110 ms in any island mode operations, and it is faster than the conventional detection methods. None detection zone (NDZ) is also almost zero in the proposed method. Thus, the CWT-based islanding detection method provides both a reliable NDZ and a short detection time for microgrid applications.

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