Single Phase Variable Sampling Phase Locked Loop using Composite Observer

K Arun, K Selvajyothi

Abstract


An observer based variable sampling period phase locked loop is introduced for grid connected systems. The composite observer acts as an efficient estimator of the fundamental components from a periodic input signal rich in DC and harmonics. The observer gains are designed using pole placement technique, which inherently ensures the stability of this estimator.  Even under drift frequency, a constant number of samples (512) per cycle are maintained with the help of the numerically controlled oscillator. This makes the oscillator gain elements in the observer a constant and eliminates the trigonometric computation. This phase locked loop is found to be working in a wide range of frequency 40 – 70Hz. The performance of the proposed scheme is studied with a synthetic harmonic rich signal as well as validated by implementing the PLL in Cyclone IV FPGA with a real time grid voltage.


Keywords


composite observer; harmonics; numerically controlled oscillator; phase locked loop; variable sampling

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DOI: http://doi.org/10.11591/ijeecs.v2.i1.pp49-60

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Indonesian Journal of Electrical Engineering and Computer Science (IJEECS)
p-ISSN: 2502-4752, e-ISSN: 2502-4760
This journal is published by the Institute of Advanced Engineering and Science (IAES) in collaboration with Intelektual Pustaka Media Utama (IPMU).

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