scholarly journals Frequency adaptive sliding fourier transform for synchronizing VSI to the grid

2019 ◽  
Vol 10 (2) ◽  
pp. 1034 ◽  
Author(s):  
Osama M. Arafa ◽  
M. E. Abdallah ◽  
Ghada A. Abdel Aziz
Keyword(s):  
Fourier Transform ◽  
Phase Angle ◽  
Phase Detector ◽  
Spectral Leakage ◽  
Double Frequency ◽  
Harmonic Rejection ◽  
Three Phase ◽  
Stationary Reference Frame ◽  
Filtering Technique ◽  
Phase Setting

Sliding Discrete Fourier Transform (SDFT) is very efficient regarding computational load and it possesses a very fast phase angle detection with excellent harmonic rejection at nominal frequency. However, at off-nominal frequency, SDFT generates errors in both magnitude and phase angle due to spectral leakage. This paper introduces a workaround for Fourier Transform to handle this disability under off-nominal frequency while avoiding variable-rate sampling. Sliding Fourier Transform (SFT) is used as a phase detector for a phase-locked loop whose output frequency is used to drive the SFT. The paper revisits the mathematics of Fourier Transform (FT) in a three-phase setting via a time-domain approach to show a newly proposed filtering technique for the double-frequency oscillation just by summing the FT sine/cosine filter outputs of the three individual phases. Also, the analysis aims to determine and correct the phase and magnitude errors under offnominal frequency operation. The proposed technique (SFT-PLL) is tested in real time on dSPACE DS1202 DSP using voltage vectors that are pregenerated to simulate the most adverse grid conditions. The testing scenarios compare the performance of the SFT-PLL with that of the Decoupled Stationary Reference Frame PLL (dαβPLL). The results prove that SFT-PLL is superior to dαβPLL.

Virtual Instrumentation Based Analysis of Induction Motor

2014 ◽  
Vol 984-985 ◽  
pp. 970-976
Author(s):  
Memala W. Abitha ◽  
V. Rajini
Keyword(s):  
Induction Motor ◽  
Life Time ◽  
Open Circuit ◽  
Virtual Instrumentation ◽  
Repair Work ◽  
Three Phase ◽  
Stationary Reference Frame ◽  
Stator Fault ◽  
Motor Failure ◽  
Vector Approach

The three phase induction motor is a popularly used machine in many of the industries, which is well known for its robustness, reliability, cost effectiveness, efficient and safe operation. The unnoticed manufacturing failure, mistakes during repair work, exceeding life time may be some of the causes of the induction motor failure, which may lead to the unknown shut down time of the industry. The condition monitoring plays important role as it has the influence on the production of materials and profit. In our work, the induction motor is modelled using stationary reference frame and analysed for single phasing stator fault. The techniques used in detecting the single phasing (open circuit) failures are Park’s vector approach and Fast Fourier Transform (FFT). Park’s vector approach is used for detecting the faults occurring at various phases and FFT is used for detecting the faults of the induction motor working under no load and varying loading conditions.

Calculation of the Phase-Angle-Jump for Voltage Dips in Three-Phase Systems

2015 ◽  
Vol 30 (1) ◽  
pp. 480-487 ◽  
Author(s):  
Ying Wang ◽  
Math H. J. Bollen ◽  
Xian-Yong Xiao
Keyword(s):  
Phase Angle ◽  
Three Phase ◽  
Voltage Dips ◽  
Phase Systems

scholarly journals Evaluation of Clipping and Filtering-Based PAPR Reduction in OFDM System

2017 ◽  
Vol 1 (2) ◽  
pp. 18
Author(s):  
N. M. A. E. D. Wirastuti ◽  
N. Pramaita ◽  
I M. A. Suyadnya ◽  
D. C. Khrisne
Keyword(s):  
Fourier Transform ◽  
Orthogonal Frequency Division Multiplexing ◽  
High Speed ◽  
Average Power ◽  
Ofdm Systems ◽  
Ofdm System ◽  
Parallel Data ◽  
Serial Data ◽  
Filtering Technique ◽  
Clipping And Filtering

This paper investigates clipping and filtering techniques in reducing peak average power ratio (PAPR) of Orthogonal Frequency Division Multiplexing (OFDM) system. The concept of OFDM is to split a high speed serial data into parallel data at a lower speed, then the parallel data carried by mutually orthogonal subcarriers. The high of PAPR is one of disadvantages of OFDM system. The high PAPR can damages the form of OFDM and reduces its performance. The purpose of this study is to reduce PAPR using simulation. OFDM was simulated with and without clipping filtering then compared.  The methods used to reduce PAPR was clipping and filtering technique. Clipping and filtering technique operates by clipping the output of inverse Fourier transform that exceed the threshold. Graphics PAPR vs. CCDF was used to evaluate the performance of OFDM systems. PAPR for OFDM system using Fourier transform when CCDF = 10-3 is 11,2 dB, with classical clipping PAPR was 4,1 dB and PAPR 4,6 dB when with deep clipping.

An Integral Method to Improve PLL Performance under Unbalanced Electric Grid Conditions

2013 ◽  
Vol 347-350 ◽  
pp. 1318-1322
Author(s):  
Shu Jun Yao ◽  
Ming Ran Bao ◽  
Ya Nan Hu ◽  
Min Xiao Han ◽  
Jun Xian Hou ◽  
...  
Keyword(s):  
Integral Method ◽  
Harmonic Signal ◽  
Reverse Polarity ◽  
System Operation ◽  
Power System Operation ◽  
Double Frequency ◽  
Operation Conditions ◽  
Synchronous Reference Frame ◽  
Three Phase ◽  
Simulation Results

Accurate phase information on three-phase grid voltage and currents which are supplied by PLL are needed in power system operation. Conventional three-phase synchronous reference frame-based phase locked loop is generally sufficient during balanced operation conditions. But unbalanced in input signal set causes a double-frequency ripple. The output signal is not ideal. There are lots of improved SRF-PLL methods, aiming at removing the double-frequency ripple such as DSC-PLL,MAF-PLL, but these methods may causes a certain time delay. DIF-PLL method is based on adding another signal, which has reverse polarity ripple. It may amplify the harmonic signal. In this paper, an INT-PLL method based on integral is proposed, which wont amplify the harmonics. The comparison of these methods and simulation results are given in this paper.

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