scholarly journals A phase-locked loop using ESO-based loop filter for grid-connected converter: performance analysis

2021 ◽  
Author(s):  
Baoling Guo ◽  
Seddik Bacha ◽  
Mazen Alamir ◽  
Julien Pouget
Keyword(s):  
Performance Analysis ◽  
Frequency Domain ◽  
Low Frequency ◽  
Experimental Tests ◽  
Frequency Measurement ◽  
Phase Locked Loop ◽  
Frequency Domain Analysis ◽  
Loop Filter ◽  
Control Stability ◽  
Unbalanced Grid

AbstractAn extended state observer (ESO)-based loop filter is designed for the phase-locked loop (PLL) involved in a disturbed grid-connected converter (GcC). This ESO-based design enhances the performances and robustness of the PLL, and, therefore, improves control performances of the disturbed GcCs. Besides, the ESO-based LF can be applied to PLLs with extra filters for abnormal grid conditions. The unbalanced grid is particularly taken into account for the performance analysis. A tuning approach based on the well-designed PI controller is discussed, which results in a fair comparison with conventional PI-type PLLs. The frequency domain properties are quantitatively analysed with respect to the control stability and the noises rejection. The frequency domain analysis and simulation results suggest that the performances of the generated ESO-based controllers are comparable to those of the PI control at low frequency, while have better ability to attenuate high-frequency measurement noises. The phase margin decreases slightly, but remains acceptable. Finally, experimental tests are conducted with a hybrid power hardware-in-the-loop benchmark, in which balanced/unbalanced cases are both explored. The obtained results prove the effectiveness of ESO-based PLLs when applied to the disturbed GcC.

scholarly journals Impact of mild orthostatic stress on aortic-cerebral hemodynamic transmission: insight from the frequency domain

2017 ◽  
Vol 312 (5) ◽  
pp. H1076-H1084 ◽  
Author(s):  
Jun Sugawara ◽  
Tsubasa Tomoto ◽  
Tomoko Imai ◽  
Seiji Maeda ◽  
Shigehiko Ogoh
Keyword(s):  
Transfer Function ◽  
Frequency Domain ◽  
Systemic Vascular Resistance ◽  
Vascular Resistance ◽  
Low Frequency ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Slow Oscillations ◽  
Transfer Function Gain ◽  
The Brain

High cerebral pressure and flow fluctuations could be a risk for future cerebrovascular disease. This study aims to determine whether acute systemic vasoconstriction affects the dynamic pulsatile hemodynamic transmission from the aorta to the brain. We applied a stepwise lower body negative pressure (LBNP) (−10, −20, and −30 mmHg) in 15 young men to induce systemic vasoconstriction. To elucidate the dynamic relationship between the changes in aortic pressure (AoP; estimated from the radial arterial pressure waveforms) and the cerebral blood flow velocity (CBFV) at the middle cerebral artery (via a transcranial Doppler), frequency-domain analysis characterized the beat-to-beat slow oscillation (0.02–0.30 Hz) and the intra-beat rapid change (0.78–9.69 Hz). The systemic vascular resistance gradually and significantly increased throughout the LBNP protocol. In the low-frequency range (LF: 0.07–0.20 Hz) of a slow oscillation, the normalized transfer function gain of the steady-state component (between mean AoP and mean CBFV) remained unchanged, whereas that of the pulsatile component (between pulsatile AoP and pulsatile CBFV) was significantly augmented during −20 and −30 mmHg of LBNP (+28.8% and +32.4% vs. baseline). Furthermore, the relative change in the normalized transfer function gain of the pulsatile component at the LF range correlated with the corresponding change in systemic vascular resistance ( r = 0.41, P = 0.005). Regarding the intra-beat analysis, the normalized transfer function gain from AoP to CBFV was not significantly affected by the LBNP stimulation ( P = 0.77). Our findings suggest that systemic vasoconstriction deteriorates the dampening effect on the pulsatile hemodynamics toward the brain, particularly in slow oscillations (e.g., 0.07–0.20 Hz). NEW & NOTEWORTHY We characterized the pulsatile hemodynamic transmission from the heart to the brain by frequency-domain analysis. The low-frequency transmission was augmented with a mild LBNP stimulation partly due to the elevated systemic vascular resistance. A systemic vasoconstriction deteriorates the dampening effect on slow oscillations of pulsatile hemodynamics toward the brain.

scholarly journals Frequency Domain Analysis of Cerebral Blood Flow Velocity and its Correlation with Arterial Blood Pressure

1998 ◽  
Vol 18 (3) ◽  
pp. 311-318 ◽  
Author(s):  
Terry Bo-Jau Kuo ◽  
Chang-Ming Chern ◽  
Wen-Yung Sheng ◽  
Wen-Jang Wong ◽  
Han-Hwa Hu
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Transfer Function ◽  
Flow Velocity ◽  
Frequency Domain ◽  
Blood Flow Velocity ◽  
Low Frequency ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Arterial Blood

We applied frequency domain analysis to detect and quantify spontaneous fluctuations in the blood flow velocity of the middle cerebral artery (MCAFV). Instantaneous MCAFV of normal volunteers was detected using transcranial Doppler sonography. Spectral and transfer function analyses of MCAFV and arterial blood pressure (ABP) were performed by fast Fourier transform. We found the fluctuations in MCAFV, like ABP, could be diffracted into three components at specific frequency ranges, designated as high-frequency (HF, 0.15 to 0.4 Hz), low-frequency (LF, 0.04 to 0.15 Hz), and very low-frequency (VLF, 0.016 to 0.04 Hz) components. The HF and LF components of MCAFV exhibited high coherence with those of ABP, indicating great similarity of MCAFV and ABP fluctuations within the two frequency ranges. However, it was not the case for the VLF component. Transfer function analysis revealed that the ABP-MCAFV phase angle was frequency-dependent in the LF range ( r = −0.79, P < 0.001) but not in the HF range. The time delay between LF fluctuations of ABP and those of MCAFV was evaluated as 2.1 seconds. We conclude that in addition to traditional B-wave equivalents, there are at least two different mechanisms for MCAFV fluctuations: the HF and LF fluctuations of MCAFV are basically secondary to those of ABP, and cerebral autoregulation may operate efficiently in LF rather than HF range. Frequency domain analysis offers an opportunity to explore the nature and underlying mechanism of dynamic regulation in cerebral circulation.

scholarly journals A Fault Diagnosis Method of Rolling Mill Bearing at Low Frequency and Overload Condition Based on Integration of EEMD and GA-DBN

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Jiang Ji ◽  
Chen Zhao ◽  
Yongqin Wang ◽  
Tuanmin Zhao ◽  
Xinyou Zhang
Keyword(s):  
Fault Diagnosis ◽  
Frequency Domain ◽  
Rolling Mill ◽  
Rolling Force ◽  
Low Frequency ◽  
Frequency Domain Analysis ◽  
Fault Classification ◽  
Low Speed ◽  
Time Frequency ◽  
Diagnosis Method

To solve the problems of difficult fault signal recognition and poor diagnosis effect of different damage in the same position in rolling mill bearing at low speed, a fault diagnosis method of rolling mill bearing based on integration of EEMD and DBN was proposed. The vibration signals in horizontal, axial, and vertical directions were decomposed and reconstructed by EEMD, and frequency domain analysis was carried out by using refined spectrum. Then, the signal's time-frequency domain index, rolling force, and torque component feature vector were input into genetic algorithm (GA) to optimize DBN model classification. In order to verify the effectiveness of the method, the experimental study was carried out on the two-high experimental rolling mill. The results show that EEMD combined with thinning spectrum can solve the problem of fault feature extraction well. Compared with time-frequency domain characteristic input, the prediction accuracy of DBN model is obviously improved. And the accuracy of GA-DBN model is higher, and the accuracy is 98.3%, and the time taken to diagnose is significantly reduced. Finally, the fault classification of different parts of bearings and the fault diagnosis of different damage in the same part are realized, which provides a good theoretical basis for the fault diagnosis of low-speed bearings and has important engineering significance.

scholarly journals Frequency-Domain Evidence for Climate Change

Econometrics ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 28
Author(s):  
Manveer Kaur Mangat ◽  
Erhard Reschenhofer
Keyword(s):  
Climate Change ◽  
Frequency Domain ◽  
Long Range ◽  
Low Frequency ◽  
Frequency Domain Analysis ◽  
Conclusive Evidence ◽  
Small Sample ◽  
Sample Test ◽  
The Time Domain ◽  
Memory Parameter

The goal of this paper is to search for conclusive evidence against the stationarity of the global air surface temperature, which is one of the most important indicators of climate change. For this purpose, possible long-range dependencies are investigated in the frequency-domain. Since conventional tests of hypotheses about the memory parameter, which measures the degree of long-range dependence, are typically based on asymptotic arguments and are therefore of limited practical value in case of small or medium sample sizes, we employ a new small-sample test as well as a related estimator for the memory parameter. To safeguard against false positive findings, simulation studies are carried out to examine the suitability of the employed methods and hemispheric datasets are used to check the robustness of the empirical findings against low-frequency natural variability caused by oceanic cycles. Overall, our frequency-domain analysis provides strong evidence of non-stationarity, which is consistent with previous results obtained in the time domain with models allowing for stochastic or deterministic trends.

Frequency-Domain Calculations of Moored Vessel Motion Including Low Frequency Effect

2008 ◽  
Author(s):  
C. Le Cunff ◽  
Sam Ryu ◽  
Jean-Michel Heurtier ◽  
Arun S. Duggal
Keyword(s):  
Frequency Domain ◽  
Drag Force ◽  
Low Frequency ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Second Order ◽  
Wave Frequency ◽  
Diffraction Radiation ◽  
Floating Structure ◽  
Low Frequency Motion

Frequency-domain analysis can be used to evaluate the motions of the FPSO with its mooring and riser. The main assumption of the frequency-domain analysis is that the coupling is essentially linear. Calculations are performed taking into account first order wave loads on the floating structure. Added mass and radiation damping terms are frequency dependent, and can be easily considered in this formulation. The major non-linearity comes from the drag force both on lines and the floating structure. Linearization of the non-linear drag force acting on the lines is applied. The calculations can be extended to derive the low frequency motion of the floating structure. Second order low frequency quadratic transfer function is computed with a diffraction/radiation method. Given a wave spectrum, the second order force spectrum can then be derived. At the same time frequency-domain analysis is used to derive the low frequency motion and wave frequency motion of the floating system. As an example case, an FPSO is employed. Comparison is performed with time domain simulation to show the robustness of the frequency-domain analysis. Some calculations are also performed with either low frequency terms only or wave frequency terms only in order to check the effect of modeling low and wave frequency terms, separately. In the case study it is found that the low frequency motion is reduced by the wave frequency motion while the wave frequency motion is not affected by the low frequency motion.

Reliability analysis of the heart autonomic control parameters during hemodialysis sessions

2016 ◽  
Vol 61 (6) ◽  
Author(s):  
Débora Martins da Silva ◽  
Murilo Carneiro Macedo ◽  
Lucas Brasileiro Lemos ◽  
Fernando Costa Vieira ◽  
Uanderson Silva Pirôpo ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Frequency Domain ◽  
Intraclass Correlation ◽  
Low Frequency ◽  
Frequency Domain Analysis ◽  
Autonomic Control ◽  
Fluctuation Analysis ◽  
Frequency Components ◽  
The Time Domain ◽  
Test Retest Reliability

AbstractThe study of heart autonomic control (HAC) in patients with chronic kidney disease (CKD) undergoing dialysis treatment has been carried out, however, there are no studies reporting the reliability of measurements of HAC parameters involving the mentioned samples and conditions. The reliability of many HAC parameters was evaluated from patients with CKD during two sessions of hemodialysis. The successive R-R intervals were recorded during two sessions of hemodialysis from 14 CKD patients that were undergoing dialysis for at least 6 months and with no history of recurrent hypotensive events. HAC parameters were obtained with time and frequency domain analysis, as well as with nonlinear methods. The reliability was measured with the intraclass correlation coefficient (ICC). The results showed excellent reliability (ICC=0.90–0.98) for most heart rate variability (HRV) parameters, especially the parameters obtained in the time domain [square root of the mean squared differences between successive R-R intervals (RMSSD), percentage of adjacent R-R intervals that differ by more than 50 ms (pNN50), mean of the 5-min standard deviations of R-R intervals (SDNNi), and triangular index] and with non-linear methods [standard deviation of the instantaneous variability beat-to-beat (SD1), standard deviation in long-term continuous R-R intervals (SD2), detrended fluctuation analysis (DFA) α1 and α2, approximate and sample entropies, and correlation dimension (D2): ICC=0.86–0.96]. Among the parameters obtained in the frequency domain (normalized magnitude from the spectrum of low-frequency components (LFnu), normalized magnitude from the spectrum of high-frequency components (HFnu), and LF/HF ratio), the LF/HF ratio showed better reliability (ICC=0.96 vs. ICC=0.70). Measurements of HAC parameters have excellent test-retest reliability for the studied samples and conditions.

Design Optimization of Enclosed Liquid Containers With Baffles for Sloshing and Impact

2004 ◽  
Author(s):  
T. C. Kingsley ◽  
K. J. Craig
Keyword(s):  
Frequency Domain ◽  
Impact Analysis ◽  
Cfd Simulation ◽  
Low Frequency ◽  
Frequency Measurement ◽  
Optimization Method ◽  
Multidisciplinary Optimization ◽  
Qualitative Comparison ◽  
Measurement Capability ◽  
Design And Optimization

A multidisciplinary optimization method is presented to support the design process of partially-filled liquid containers subject to the disciplines of sloshing and impact analysis. This paper represents a part of a study on Multidisciplinary Design and Optimization of liquid containers, and shows experimental techniques used to try to better understand sloshing as a phenomenon and to evaluate the capabilities of the commercial Computational Fluid Dynamics (CFD) code in question. Experimental validation includes qualitative comparison of visual free-surface behavior and quantitative comparisons of pressure measurements in the time and frequency domain. The liquid motion exhibits good comparisons in time with some deviations in wave amplitude due to a modification of the low frequency content of the input signal to the CFD simulation. This modification was caused by both the experimental signal filtration process and deficiencies in the low-frequency measurement capability of the accelerometer. In the frequency domain the first two odd oscillatory modes are accurately captured. A candidate objective function for the quantitative evaluation of the sloshing phenomenon is proposed. Using the response surface method in LS-OPT, various single (sloshing or impact only) and multidisciplinary optimization formulations are presented and results are examined. As expected, the multidisciplinary optimum proved to be a compromise between the optima obtained when considering the two single disciplines independently.

scholarly journals Heart rate variability and increased risk for developing type 2 diabetes mellitus

2014 ◽  
Vol 71 (12) ◽  
pp. 1109-1115 ◽  
Author(s):  
Biljana Pencic-Popovic ◽  
Vera Celic ◽  
Zoran Cosic ◽  
Milena Pavlovic-Kleut ◽  
Zorica Caparevic ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
Frequency Domain ◽  
Time Domain ◽  
Low Frequency ◽  
Frequency Domain Analysis ◽  
Elevated Risk ◽  
Group I ◽  
Increased Risk ◽  
Group Ii

Background/Aim. To our knowledge there are no data about the relationship between elevated risk for developing type 2 diabetes mellitus (DM2) and altered cardiac autonomic function. The aim of this study was to evaluate the association between heart rate variability (HRV) and slightly increased risk for DM2. Methods. We evaluated 69 subjects (50.0 ? 14.4 years; 30 male) without DM2, coronary artery disease and arrhythmias. The subjects were divided into two groups according to the Finnish Diabetes Risk Score (FINDRISC): group I (n = 39) included subjects with 12 > FINDRISC ? 7; group II (n = 30) subjects with FINDRISC < 7. HRV was derived from 24-h electrocardiogram. We used time domain variables and frequency domain analysis performed over the entire 24-h period, during the day (06-22 h) and overnight (22-06 h). Results. Standard deviation of the average normal RR intervals was significantly lower in the group with increased risk for DM2 compared to the group II (127.1 ? 26.6 ms vs 149.6 ? 57.6 ms; p = 0.035). Other time domain measures were similar in both groups. The group I demonstrated significantly reduced frequency domain measures, total power - TP (7.2 ? 0.3 ln/ms2 vs 7.3 ? 0.3 ln/ms2; p = 0.029), and low frequency - LF (5.9 ? 0.4 ln/ms2 vs 6.3 ? 0.6 ln/ms2; p = 0.006), over entire 24 h, as well as TP (7.1 ? 0.3 ln/ms2 vs 7.3 ? 0.3 ln/ms2; p = 0.004), very low frequency (6.2 ? 0.2 ln/ms2 vs 6.3 ? 0.2 ln/ms2; p = 0.030), LF (5.9 ? 0.4 ln/ms2 vs 6.2 ? 0.3 ln/ms2; p = 0.000) and high frequency (5.7 ? 0.4 ln/ms2 vs 5.9 ? 0.4 ln/ms2; p = 0.011) during the daytime compared to the group II. Nocturnal frequency domain analysis was similar between the groups. The low diurnal frequency was independently related to elevated risk for diabetes mellitus (beta = -0,331; p = 0.006). Conclusion. The obtained results suggest that even slightly elevated risk for developing diabetes mellitus may be related to impaired HRV.

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