Variable Sampling Composite Observer Based Frequency Locked Loop and its Application in Grid Connected System
A modified digital signal processing procedure is described for the on-line estimation of DC, fundamental and harmonics of periodic signal. A frequency locked loop (FLL) incorporated within the parallel structure of observers is proposed to accommodate a wide range of frequency drift. The error in...
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| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Stefan cel Mare University of Suceava
2016-05-01
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| Series: | Advances in Electrical and Computer Engineering |
| Subjects: | |
| Online Access: | http://dx.doi.org/10.4316/AECE.2016.02005 |
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| Summary: | A modified digital signal processing procedure is described for the on-line estimation of DC, fundamental
and harmonics of periodic signal. A frequency locked loop (FLL) incorporated within the parallel structure
of observers is proposed to accommodate a wide range of frequency drift. The error in frequency generated
under drifting frequencies has been used for changing the sampling frequency of the composite observer, so
that the number of samples per cycle of the periodic waveform remains constant. A standard coupled oscillator
with automatic gain control is used as numerically controlled oscillator (NCO) to generate the enabling pulses
for the digital observer. The NCO gives an integer multiple of the fundamental frequency making it suitable
for power quality applications. Another observer with DC and second harmonic blocks in the feedback path act
as filter and reduces the double frequency content. A systematic study of the FLL is done and a method has
been proposed to design the controller. The performance of FLL is validated through simulation and experimental
studies. To illustrate applications of the new FLL, estimation of individual harmonics from nonlinear load and
the design of a variable sampling resonant controller, for a single phase grid-connected inverter have been presented. |
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| ISSN: | 1582-7445 1844-7600 |