Şebeke bağlantılı tek fazlı dokuz seviyeli asimetrik evirici tasarımı ve analizi

Öz

Günümüzde yaygın olarak kullanılan çok seviyeli Eviriciler (ÇSE) için giriş tarafındaki gerilim seviyeleri önemli bir sınırlayıcı olmaktadır. Yüksek güçlü enerji sistemlerinde, iki seviyeli eviricilerde kullanılacak anahtarlama elemanının gücünün yetersiz kalması, çıkış dalga şeklinin sinüzoidalden uzak olması ve düşük gerilim üretilmesinden kaynaklı transformatör kullanılması klasik iki seviyeli eviricilerin dezavantajlarındandır. Ayrıca iki seviyeli eviricilerde toplam harmonik distorsiyonunu (THD) azaltmak için yüksek anahtarlama frekansının kullanılması anahtarlama kayıplarını arttırmaktadır. Bu çalışmada, asimetrik eviricinin THD oranını düşürmek ve şebeke bağlantısını gerçekleştirmek için Matlab/Simulink ortamında modelleme yapılmıştır. Çalışma kapsamında, üçlü besleme gerilimi yapısında asimetrik H-köprü evirici modellenmiş ve sinüzoidal darbe genişlik modülasyonu (SDGM) kontrol algoritması ile anahtarlama işaretleri üretilmiştir. Eviricinin şebeke bağlantısı, geliştirilen PI kontrol algoritması ve PLL kontrol algoritmalarıyla denetlenmiştir. Tasarlanan PI ile elde edilen sonuçlarda THD oranının düştüğü görülmektedir. Ayrıca sistemin açık döngüye göre dinamik ve hızlı çalıştığı gözlemlenmiştir. Sistem hem açık döngü çalıştırılarak hem PI kontrolcü ile hem de PI-PLL ile çalıştırılarak THD oranları incelenmiş ve önerilen tek fazlı şebeke etkileşimli evirici kontrol yöntemi doğrulanmıştır. Yapılan çalışmalar sonucunda sistemin kontrolünde PI ve PI-PLL kontrollerinden elde edilen sonuçların yaklaşık aynı olduğu ancak PI-PLL kontrol yönteminin daha verimli sonuçlar sağladığı görülmüştür. Ayrıca, tasarlanan PLL yöntemiyle karışık kontrol yöntemlerine ve algoritmalara ihtiyaç olmadan sistem şebekeye bağlanmıştır.

Anahtar Kelimeler

• Asimetrik evirici,PI kontrolcü,PLL kontrolcü,Güneş enerjisi,Toplam harmonik distorsiyonu

Design and analysis of a grid-tied single phase nine level asymmetrical inverter

Abstract

The supply voltage levels of the multilevel inverters (MLIs) that are widely used nowadays are the significant limiting parameters. The major drawbacks of conventional two-level inverters used in the high power systems are the insufficient switch power against the power range, non-sinusoidal output waveforms, and increasing line transformer requirements. Furthermore, the higher switching frequency requirement to reduce the total harmonic distortion (THD) increases the switching losses. This study presents the design and analysis of a controller that is performed by using Matlab/Simulink environment. The asymmetrical MLI topology is constituted in trinary DC supply structure, and the switching frequencies are generated in sinusoidal pulse width modulation (SPWM) scheme. The grid connection of the inverter is controlled by the implemented proportional-integral (PI) controller and phase locked loop (PLL) control algorithm. The proposed control method is compared to conventional controllers in terms of THD rates and observer structure. It is observed that the designed PI controller decreases the THD ratio, with higher dynamic response. The improved control mechanism is tested under open-loop, PI controlled, and PI-PLL controlled structures to determine the THD ratios where the proposed single phase grid-tied control method is verified. The performed analysis results have shown that the PI and PI-PLL controllers provide almost same result, but the PI-PLL controller draws faster dynamic response comparing to PI control algorithm. Besides, the proposed PLL controller ensures the grid connection of inverter without complex control methods or complex algorithm requirement.

Keywords

• Asymmetrical inverter,PI controller,PLL controller,Solar energy,Total harmonic distortion

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