Improved single-phase PLL structure with DC-SOGI block on FPGA board implementation

Synchronization block which is used as a part of photovoltaic (PV) inverters control structure has a key impact on connectinginverters with grid. One of the most important parameters in the point of connection PV inverter and grid is phase angle between gridvoltage and inverter current. This angle determines the energy transfer between inverter and grid. Synchronization algorithms havedeveloped for very long time. At first, they were based on zero crossing grid voltage detection, while today complexed synchronizationalgorithms implemented on high performance digital board have been used. One of these synchronization structures is Phase LockedLoop – PLL. In this paper implementation of improved PLL structure is presented. This improved structure is special while it haspossibility of grid parameters estimation even if grid voltage has noise or DC offset. This DC offset from the grid in PLL structureusually entered via measurement and A/D conversion processor or may be generated due to temporary system faults. Appearance ofDC offset in measured grid voltage on the one hand prevents any estimation process of grid parameters and on the other hand alsodegrades reference sine signal at the output of PLL structure in PV inverters. This improved structure is designed in digital form andimplemented on FPGA digital board and experimental results of this implementation are presented. Obtained experimental resultsshow that the proposed PLL structure successfully solves important issue such is presence of DC offset in measured grid voltage.

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Benchmarking of phase lock loop based synchronization algorithms for grid-tied inverter

Serbian Journal of Electrical Engineering ◽

10.2298/sjee1901001f ◽

2019 ◽

Vol 16 (1) ◽

pp. 1-19 ◽

Cited By ~ 2

Author(s):

Filip Filipovic ◽

Bojan Bankovic ◽

Milutin Petronijevic ◽

Nebojsa Mitrovic ◽

Vojkan Kostic

Keyword(s):

Reference Frame ◽

Frequency Estimation ◽

Wide Spectrum ◽

Phase Lock Loop ◽

Grid Voltage ◽

Dc Offset ◽

Grid Synchronization ◽

Synchronous Reference Frame ◽

Stationary Reference Frame ◽

Voltage Phase

In renewable energy-based generation sources a phase locked loop is one of the most popular synchronization techniques. A rapid and precise grid voltage phase and frequency estimation under a wide spectrum of possible grid disturbances is its main objective. This paper compares popular grid synchronization algorithms on grid voltage anomalies. The compared algorithms are divided in three groups: without filtering, with filtering in synchronous reference frame and with filtering in stationary reference frame. The behaviour of the algorithms is tested in a laboratory, using dSpace 1103 as a platform on which the algorithms are compiled and OMICRON CMC 356 as a programmable grid voltage generator. The benchmarks conducted in this paper include voltage sags, grid voltages harmonics, DC offset and frequency step change. The obtained results show that there are significant differences in tested PLL responses for some networks disturbances.

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DC offset rejection in a frequency-fixed second-order generalized integrator-based phase-locked loop for single-phase grid-connected applications

Protection and Control of Modern Power Systems ◽

10.1186/s41601-021-00223-w ◽

2022 ◽

Vol 7 (1) ◽

Author(s):

Issam A. Smadi ◽

Bayan H. Bany Fawaz

Keyword(s):

Single Phase ◽

Dynamic Performance ◽

Phase Error ◽

Phase Locked Loop ◽

Second Order ◽

Frequency Variation ◽

Grid Voltage ◽

Dc Offset ◽

Grid Synchronization ◽

Grid Connected Converters

AbstractFast and accurate monitoring of the phase, amplitude, and frequency of the grid voltage is essential for single-phase grid-connected converters. The presence of DC offset in the grid voltage is detrimental to not only grid synchronization but also the closed-loop stability of the grid-connected converters. In this paper, a new synchronization method to mitigate the effect of DC offset is presented using arbitrarily delayed signal cancelation (ADSC) in a second-order generalized integrator (SOGI) phase-locked loop (PLL). A frequency-fixed SOGI-based PLL (FFSOGI-PLL) is adopted to ensure better stability and to reduce the complexity compared with other SOGI-based PLLs. A small-signal model of the proposed PLL is derived for the systematic design of proportional-integral (PI) controller gains. The effects of frequency variation and ADSC on the proposed PLL are considered, and correction methods are adopted to accurately estimate grid information. The simulation results are presented, along with comparisons to other single-phase PLLs in terms of settling time, peak frequency, and phase error to validate the proposed PLL. The dynamic performance of the proposed PLL is also experimentally validated. Overall, the proposed PLL has the fastest transient response and better dynamic performance than the other PLLs for almost all performance indices, offering an improved solution for precise grid synchronization in single-phase applications.

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Alkohol im Tank – Bio-Kraftstoffe und die Grenzen moderner Mobilität

PROKLA Zeitschrift für kritische Sozialwissenschaft ◽

10.32387/prokla.v34i136.625 ◽

2004 ◽

Vol 34 (136) ◽

pp. 455-468

Author(s):

Hartwig Berger

Keyword(s):

Third World ◽

Fossil Fuel ◽

Energy Resources ◽

The Third ◽

Political Conflicts ◽

The Future ◽

Long Time ◽

Food Market ◽

The One ◽

The Third World

The article discusses the future of mobility in the light of energy resources. Fossil fuel will not be available for a long time - not to mention its growing environmental and political conflicts. In analysing the potential of biofuel it is argued that the high demands of modern mobility can hardly be fulfilled in the future. Furthermore, the change into using biofuel will probably lead to increasing conflicts between the fuel market and the food market, as well as to conflicts with regional agricultural networks in the third world. Petrol imperialism might be replaced by bio imperialism. Therefore, mobility on a solar base pursues a double strategy of raising efficiency on the one hand and strongly reducing mobility itself on the other.

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Making it abstract, making it contestable: Gender/sex as a politicized concept

10.31234/osf.io/u6wd2 ◽

2020 ◽

Author(s):

Claudia Mazzuca ◽

Matteo Santarelli

Keyword(s):

Social Sciences ◽

Main Question ◽

Abstract Concepts ◽

Biological Feature ◽

Dynamic Approach ◽

Cognitive Sciences ◽

Long Time ◽

Cultural Construct ◽

Science Framework ◽

The One

The concept of gender has been the battleground of scientific and political speculations for a long time. On the one hand, some accounts contended that gender is a biological feature, while on the other hand some scholars maintained that gender is a socio-cultural construct (e.g., Butler, 1990; Risman, 2004). Some of the questions that animated the debate on gender over history are: how many genders are there? Is gender rooted in our biological asset? Are gender and sex the same thing? All of these questions entwine one more crucial, and often overlooked interrogative. How is it possible for a concept to be the purview of so many disagreements and conceptual redefinitions? The question that this paper addresses is therefore not which specific account of gender is preferable. Rather, the main question we will address is how and why is even possible to disagree on how gender should be considered. To provide partial answers to these questions, we suggest that gender/sex (van Anders, 2015; Fausto-Sterling, 2019) is an illustrative example of politicized concepts. We show that no concepts are political in themselves; instead, some concepts are subjected to a process involving a progressive detachment from their supposed concrete referent (i.e., abstractness), a tension to generalizability (i.e., abstraction), a partial indeterminacy (i.e., vagueness), and the possibility of being contested (i.e., contestability). All of these features differentially contribute to what we call the politicization of a concept. In short, we will claim that in order to politicize a concept, a possible strategy is to evidence its more abstract facets, without denying its more embodied and perceptual components (Borghi et al., 2019). So, we will first outline how gender has been treated in psychological and philosophical discussions, to evidence its essentially contestable character thereby showing how it became a politicized concept. Then we will review some of the most influential accounts of political concepts, arguing that currently they need to be integrated with more sophisticated distinctions (e.g., Koselleck, 2004). The notions gained from the analyses of some of the most important accounts of political concepts in social sciences and philosophy will allow us to implement a more dynamic approach to political concepts. Specifically, when translated into the cognitive science framework, these reflections will help us clarifying some crucial aspects of the nature of politicized concepts. Bridging together social and cognitive sciences, we will show how politicized concepts are abstract concepts, or better abstract conceptualizations.

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A Cost-Effective Decentralized Control for AC-Stacked Photovoltaic Inverters

Energies ◽

10.3390/en11092262 ◽

2018 ◽

Vol 11 (9) ◽

pp. 2262 ◽

Cited By ~ 1

Author(s):

Hua Han ◽

Chao Luo ◽

Xiaochao Hou ◽

Mei Su ◽

Wenbin Yuan ◽

...

Keyword(s):

Decentralized Control ◽

Cost Effective ◽

Current Control ◽

Control Mode ◽

Communication Link ◽

Grid Voltage ◽

Point Tracking ◽

Pv Inverter ◽

Communication Links ◽

Voltage Phase

For an AC-stacked photovoltaic (PV) inverter system with N cascaded inverters, existing control methods require at least N communication links to acquire the grid synchronization signal. In this paper, a novel decentralized control is proposed. For N inverters, only one inverter nearest the point of common coupling (PCC) needs a communication link to acquire the grid voltage phase and all other N − 1 inverters use only local measured information to achieved fully decentralized local control. Specifically, one inverter with a communication link utilizes the grid voltage phase and adopts current control mode to achieve a required power factor (PF). All other inverters need only local information without communication links and adopt voltage control mode to achieve maximum power point tracking (MPPT) and self-synchronization with grid voltage. Compared with existing methods, the communication link and complexity is greatly reduced, thus improved reliability and reduced communication costs are achieved. The effectiveness of the proposed control is verified by simulation tests.

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Comparative Study of the Field Performances of Pressure-Grouted Micropiles Using Gravity and Packers

Applied Sciences ◽

10.3390/app11156736 ◽

2021 ◽

Vol 11 (15) ◽

pp. 6736

Author(s):

Ong Heo ◽

Yeowon Yoon ◽

Jinung Do

Keyword(s):

Urban Areas ◽

High Performance ◽

Driving Forces ◽

Field Performance ◽

Underground Space ◽

Creep Tests ◽

Deep Foundation ◽

Installation Depth ◽

Pressure Grouting ◽

The One

When underground space requires excavation in areas below the water table, the foundation system suffers from buoyancy, which leads to the uplifting of the superstructure. A deep foundation system can be used; however, in cases where a hard layer is encountered, high driving forces and corresponding noises cause civil complaints in urban areas. Micropiles can be an effective alternative option, due to their high performance despite a short installation depth. Pressurized grouting is used with a packer to induce higher interfacial properties between micropile and soil. In this study, the field performance of micropiles installed using gravitational grouting or pressure-grouted using either a geotextile packer or rubber packer was comparatively evaluated by tension and creep tests. Micropiles were installed using pressure grouting in weak and fractured zones. As results, the pressure-grouted micropiles showed more stable and stronger behaviors than ones installed using the gravitational grouting. Moreover, the pressure-grouted micropile installed using the rubber packer showed better performance than the one using the geotextile packer.

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On Performance of Sparse Fast Fourier Transform Algorithms Using the Aliasing Filter

Electronics ◽

10.3390/electronics10091117 ◽

2021 ◽

Vol 10 (9) ◽

pp. 1117

Author(s):

Bin Li ◽

Zhikang Jiang ◽

Jie Chen

Keyword(s):

Fourier Transform ◽

Fast Fourier Transform ◽

High Efficiency ◽

Theory And Practice ◽

Long Time ◽

And Performance ◽

Binary Tree Search ◽

The One ◽

Sparse Fast Fourier Transform ◽

L1 And L2

Computing the sparse fast Fourier transform (sFFT) has emerged as a critical topic for a long time because of its high efficiency and wide practicability. More than twenty different sFFT algorithms compute discrete Fourier transform (DFT) by their unique methods so far. In order to use them properly, the urgent topic of great concern is how to analyze and evaluate the performance of these algorithms in theory and practice. This paper mainly discusses the technology and performance of sFFT algorithms using the aliasing filter. In the first part, the paper introduces the three frameworks: the one-shot framework based on the compressed sensing (CS) solver, the peeling framework based on the bipartite graph and the iterative framework based on the binary tree search. Then, we obtain the conclusion of the performance of six corresponding algorithms: the sFFT-DT1.0, sFFT-DT2.0, sFFT-DT3.0, FFAST, R-FFAST, and DSFFT algorithms in theory. In the second part, we make two categories of experiments for computing the signals of different SNRs, different lengths, and different sparsities by a standard testing platform and record the run time, the percentage of the signal sampled, and the L0, L1, and L2 errors both in the exactly sparse case and the general sparse case. The results of these performance analyses are our guide to optimize these algorithms and use them selectively.

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AFX Zeolite for Use as a Support of NH3-SCR Catalyst Mining through AICE Joint Research Project of Industries–Academia–Academia

Catalysts ◽

10.3390/catal11020163 ◽

2021 ◽

Vol 11 (2) ◽

pp. 163

Author(s):

Masaru Ogura ◽

Yumiko Shimada ◽

Takeshi Ohnishi ◽

Naoto Nakazawa ◽

Yoshihiro Kubota ◽

...

Keyword(s):

High Performance ◽

Ionic Species ◽

Research Project ◽

Joint Research ◽

Structure Directing Agent ◽

Scr Catalyst ◽

Organic Structure ◽

Nh3 Scr ◽

Joint Research Project ◽

The One

This paper introduces a joint industries–academia–academia research project started by researchers in several automobile companies and universities working on a single theme. Our first target was to find a zeolite for NH3-SCR, that is, zeolite mining. Zeolite AFX, having the same topology of SSZ-16, was found to be the one of the zeolites. SSZ-16 can be synthesized by using an organic structure-directing agent such as 1,1′-tetramethylenebis(1-azonia-4-azabicyclo[2.2.2]octane; Dab-4, resulting in the formation of Al-rich SSZ-16 with Si/Al below five. We found that AFX crystallized by use of N,N,N′,N′-tetraethylbicyclo[2.2.2]oct-7-ene-2,3:5,6-dipyrrolidinium ion, called TEBOP in this study, had the same analog as SSZ-16 having Si/Al around six and a smaller particle size than SSZ-16. The AFX demonstrated a high performance for NH3-SCR as the zeolitic support to load a large number of divalent Cu ionic species with high hydrothermal stability.

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Bottom-Up Generation of Peak Demand Scenarios in Water Distribution Networks

Sustainability ◽

10.3390/su13010031 ◽

2020 ◽

Vol 13 (1) ◽

pp. 31

Author(s):

Enrico Creaco ◽

Giacomo Galuppini ◽

Alberto Campisano ◽

Marco Franchini

Keyword(s):

Water Distribution ◽

Distribution Networks ◽

Water Distribution Networks ◽

Peak Demand ◽

Long Time ◽

Cross Correlations ◽

User Demand ◽

One Year ◽

The One ◽

Best Fit

This paper presents a two-step methodology for the stochastic generation of snapshot peak demand scenarios in water distribution networks (WDNs), each of which is based on a single combination of demand values at WDN nodes. The methodology describes the hourly demand at both nodal and WDN scales through a beta probabilistic model, which is flexible enough to suit both small and large demand aggregations in terms of mean, standard deviation, and skewness. The first step of the methodology enables generating separately the peak demand samples at WDN nodes. Then, in the second step, the nodal demand samples are consistently reordered to build snapshot demand scenarios for the WDN, while respecting the rank cross-correlations at lag 0. The applications concerned the one-year long dataset of about 1000 user demand values from the district of Soccavo, Naples (Italy). Best-fit scaling equations were constructed to express the main statistics of peak demand as a function of the average demand value on a long-time horizon, i.e., one year. The results of applications to four case studies proved the methodology effective and robust for various numbers and sizes of users.

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Constructing Large-Scale Genetic Maps Using an Evolutionary Strategy Algorithm

Genetics ◽

10.1093/genetics/165.4.2269 ◽

2003 ◽

Vol 165 (4) ◽

pp. 2269-2282

Author(s):

D Mester ◽

Y Ronin ◽

D Minkov ◽

E Nevo ◽

A Korol

Keyword(s):

Discrete Optimization ◽

High Performance ◽

Large Scale ◽

Simulated Data ◽

Real Data ◽

Genetic Maps ◽

Chromosome 1 ◽

Evolutionary Strategy ◽

Group A ◽

The One

Abstract This article is devoted to the problem of ordering in linkage groups with many dozens or even hundreds of markers. The ordering problem belongs to the field of discrete optimization on a set of all possible orders, amounting to n!/2 for n loci; hence it is considered an NP-hard problem. Several authors attempted to employ the methods developed in the well-known traveling salesman problem (TSP) for multilocus ordering, using the assumption that for a set of linked loci the true order will be the one that minimizes the total length of the linkage group. A novel, fast, and reliable algorithm developed for the TSP and based on evolution-strategy discrete optimization was applied in this study for multilocus ordering on the basis of pairwise recombination frequencies. The quality of derived maps under various complications (dominant vs. codominant markers, marker misclassification, negative and positive interference, and missing data) was analyzed using simulated data with ∼50-400 markers. High performance of the employed algorithm allows systematic treatment of the problem of verification of the obtained multilocus orders on the basis of computing-intensive bootstrap and/or jackknife approaches for detecting and removing questionable marker scores, thereby stabilizing the resulting maps. Parallel calculation technology can easily be adopted for further acceleration of the proposed algorithm. Real data analysis (on maize chromosome 1 with 230 markers) is provided to illustrate the proposed methodology.

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