Parametre odaklı bir FFT Sisnyal İşleme Uygulaması

Abstract

Güç sistemlerindeki elektrik sinyallerinde, değişken kaynaklar ve yükler nedeniyle gürültü, harmonikler veya ara harmonikler gibi çeşitli bileşenler ortaya çıkar ve bu durum elektrik sinyalinin saflığında değişikliklere neden olur. Dolayısıyla, elektrik sinyallerinin sürekli izlenmesi ve doğru analizi zorunlu hale gelmektedir. Bu alanda yaygın yöntemlerden biri olan Hızlı Fourier Dönüşümü (HFD) kullanılarak elektrik sinyalleri, IEC-61000-4-7 standardının öngördüğü aralıklarla kayan pencereler aracılığıyla sürekli analize tabi tutulur. Bu analizden çeşitli parametreler türetilir ve IEEE-1159 standardında belirtilen eşik değerleriyle karşılaştırılır. Ancak değişken saha koşullarının yanı sıra örnekleme frekansı, ölçüm penceresi, ana frekans, ek bileşenlerin frekansı ve Sinyal-Gürültü Oranı (SNR) gibi faktörlerden dolayı çeşitli ölçüm hataları ortaya çıkar. Bu zorluklar, değişken koşullarda zaten zor olan doğru ölçüm görevini daha da karmaşık hale getirir ve önleyici tedbirler ve kontrol prosedürlerinde hata yapılmasına yol açabilir. Bu nedenle, bu parametrelerin etkilerinin anlaşılması ve buna göre yöntemlerin iyileştirilmesi çok önemlidir. Bu çalışmada FFT için parametre seçiminin önemi vurgulanmış ve FFT cevapları farklı parametreler açısından incelenmiştir. Ayrıca, sinyaldeki değişikliklere göre ölçüm hataları ortaya konmuş ve bu hataları gösteren temel bir arayüz tasarımı sunulmuştur. Örnekleme frekansında 1/2000'lik bir değişiklik, ana frekansta 0,5 Hz'lik bir kayma veya ölçüm penceresindeki 1/1000’lik bir fark gibi küçük değişiklikler önemli hatalara neden olmutur. Bu bulgular, hassas hesaplama ve sinyal izleme çalışmaları için mantıklı parametre seçiminin gerekliliğinin altını çizmekte ve değişken koşullara uyum sağlamak için FFT yönteminde iyileştirmeler yapılması gerektiğini göstermektedir. Bu uygulama güç sistemi sinyallerine yönelik tasarlanmış olsa da uygulanabilirliği biyomedikal, ses ve diğer elektrik sinyali çalışmaları için de kullanılabilir.

Keywords

• Güç kalitesi
• IEEE-1159
• HFD
• örnekleme frekansı
• ana frekans

A Parameter-Oriented FFT Signal Processing App

Abstract

In power systems, noise, harmonics, and interharmonics arise in electrical signals due to varying sources and loads, affecting signal purity. Continuous monitoring and accurate analysis of electrical signals are mandatory. The Fast Fourier Transform (FFT) continuously analyzes electrical signals using sliding windows per the IEC-61000-4-7 standard. Parameters from this analysis are compared with threshold values specified in the IEEE-1159 standard. However, variable conditions and factors like sampling frequency, measurement window, main frequency, additional component frequencies, and Signal-to-Noise Ratio (SNR) cause measurement errors. These challenges complicate accurate measurement, leading to errors in preventive measures and control procedures. Understanding the effects of these parameters and improving methods is crucial. The Visible Thinking pedagogical framework is effective in this achievement. This study highlights the importance of parameter selection for FFT and investigates FFT responses to different parameters with synthetical and experimental signal examples. It also presents measurement errors due to signal changes, and a basic interface design shows these errors. Small changes, like a 1/2000 shift in sampling frequency, a 0.5 Hz shift in fundamental frequency, or a 1/1000 difference in the measurement window, cause significant errors. These findings underscore the need for careful parameter selection for accurate computation and signal monitoring, showing the need for FFT method improvements to adapt to changing conditions.

Keywords

• Power Quality
• FFT
• main frequency
• sampling frequency
• measurement window
• visible thinking

Ethical Statement

The study complies with research and publication ethics.

Thanks

The author would like to thank the Sivas University of Science and Technology, Department of Electrical Electronics Engineering, Smart Grids Laboratory.

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