Distributed Consensus Control of DFIGs with Storage for Wind Farm Power Output Regulation

Today the state-of-the-art (SoA) wind generators (WGs) are the double-fed induction (DFIGs) with integrated storage devices. In the future, these WGs are expected to be one of the largest producers of renewable energy worldwide. In this paper, we propose a distributed control methodology for solving the problem of coordinating and controlling a group of SoA WGs to attain fast wind farm (WF) power output regulation with each storage device providing the same amount of power, i.e with equal sharing among the storage devices. Our proposed methodology introduces a consensus protocol for coordinating the grid-side converters (GSCs), whose dynamical equations constitute their closed-loop dynamics, and a particular closed-loop form for the interfacing capacitor dynamics. We establish stability of these closed-loop dynamics by leveraging singular perturbation and Lyapunov theories, proving that with these closed-loop dynamics DFIGs accomplish their assigned control objectives. Finally, we analytically construct a distributed and a Control Lyapunov Function (CLF) -based control law for the GSC and the DCDC converter respectively, which jointly lead to the desired closed-loop dynamics. We demonstrate the effectiveness of our methodology through simulations on the IEEE 24-bus reliability test system (RTS)

The Parallel Implementation of the Waveform Relaxation Method for the Simulation of Structure-Preserved Power Systems

Several results pertaining to the partitioning of the waveform relaxation (WR) algorithm for dynamic simulation are presented. The WR algorithm is extended to a structure-preserving power system model in which the loads are retained. This results in a system of differential/algebraic equations (DAEs). Power systems are shown to exhibit several dynamic characteristics which make them suitable for simulation by the WR method. A heuristic method for determining a fault-dependent partitioning of the power system for parallel implementation is given

The Parallel Implementation of the Waveform Relaxation Method for Transient Stability Simulations

In this paper, the authors extend the results of their earlier paper on waveform relamtion (WR), which is a parallel algorithm for transient stability analysis. The WR algorithm is extended to a structure-preserving power system model in which the loads are retained. This results in a system of differential/ algebraic equations (DAEs). Power systems exhibit several unique dynamic properties which may be exploited in an advantageous manner by the WR algorithm. This leads to a greater computational efficiency than most other direct methods of simulation. This paper presents several theoretical results as well as computational results on parallel implementation

The Waveform Relaxation Method for Systems of Differential/Algebraic Equations

An extension of the waveform relaxation (WR) algorithm to systems of differential/algebraic equations (DAE) is presented. Although this type of application has been explored earlier in relation to VLSI circuits, the algorithm has not been generalized to include the vast array of DAE system structures. The solvability and convergence requirements of the WR algorithm for higher-index systems are established. Many systems in robotics and control applications are modeled with DAE systems having an index greater than two. Computer simulation of these systems has been hampered by numerical integration methods which perform poorly and must be explicitly tailored to the system. The WR algorithm presents a means by which these systems may be more efficiently simulated by breaking them into weakly coupled subsystems, many of which will no longer retain the limiting high-index properties

Hemijski sastav, antioksidativna, antimikrobna i antiholinesterazna aktivnost biljnih vrsta Seseli rigidum i Seseli pallasii

Тhe chemical composition of essential oils, extracts of different polarity, and mineral composition of plants Seseli rigidum and Seseli pallasii were analysed. For rapid analysis of volatiles of S. rigidum above ground parts, and S. pallasii fruits and roots volatiles, HS/GCMS technique may be used, while in all other cases is necessary to isolate essential oils and apply GC-MS technique. According to principle component analysis (PCA) and hierarchical cluster analysis (HCA) a groupings of the samples were done, based on the similarity of the chemical composition of certain plant parts (leaf, flower, fruit and roots). The variables based on the dominant components were grouped using PCA and HCA analysis. Biological activities and characteristics of essential oils, extracts of different polarity of vegetative parts of both plants were investigated. Antioxidant properties were tested using ABTS, DPPH, total reducing power methods, total flavonoids and total phenols content. According to the ABTS and DPPH methods, the best properties were manifested by hexane extracts of both tested plant species, and flower acetone extract of S. rigidum, respectively, while the highest total reducing capacity had the methanol extracts of S. rigidum. The highest total phenols and flavonoids were registered for hexane extracts of root and leaf of S. pallasii. Both applied methods of statistical analyses (PCA and HCA) in which the results of antioxidant activities were used as variables, clearly distinguished DPPH method from other methods, and tested samples were separated by type (oils and extracts), and according to the type of solvent used in the preparation of extracts. Determination of antimicrobial activity of essential oils and extracts versus different strains of Gram (+) and Gram (-) bacteria, using the microdilution method, showed that the root essential oil of S. rigidum had the most pronounced effect. In terms of inhibition of enzyme cholinesterase, estimated using Elman’s method, the highest degree of inhibition was recorded for the root methanol extract of S. pallasii. Overall, the best characteristics among tested activities, showed secondary metabolites of S. rigidum root, and therefore identification of main components of the extract using liquid chromatography combined with high resolution mass spectrometry was performed. Reliably was established presence of thirty compounds, most of which with coumarin structure. In each of the vegetative parts of both plants content of macro-, microelements and heavy metals were determined and found that their content does not exceed the permissible values. Results obtained using two methods of multivariate statistics are in accordance and grouped certain plants’ parts based on the highest content of micro, macroelements or heavy metals

Morphological differentiation of larval stages of selected anuran Rana and Bufo species in Serbia

Mrke žabe (Rana dalmatina, R. graeca, R. temporaria) i obična krastača (Bufo bufo) na području Srbije mogu biti sintopne, a ulaze u vodena staništa samo tokom kratkog reproduktivnog perioda u rano proleće. Punoglavci provode duži vremenski period u vodenim staništima i lakše su uočljivi u odnosu na adulte. Analiza njihove morfologije je jedan od mogućih načina taksonomske identifikacije, naročito u slučajevima kada su genetičke metode nedostupne. Kod nekih vrsta punoglavci na ranim stupnjevima su vizuelno veoma slični, što otežava njihovu identifikaciju na terenu. Definisani su sledeći osnovni ciljevi: utvrditi osobine spoljašnje morfologije punoglavaca analiziranih vrsta žaba na osnovu kojih se može odrediti njihova taksonomska pripadnost; utvrditi efikasnost primene analiza oblika tela punoglavaca u taksonomskoj identifikaciji; razviti procedure za njihovu pouzdanu, brzu i ekonomičnu taksonomsku identifikaciju. Dodatno, izvršena je taksonomska genetička identifikacija, upoređena je upotreba metoda tradicionalne i geometrijske morfometrije u morfološkoj diferencijaciji ranih larvenih stadijuma, kao i filogenetski i fenetički odnosi analiziranih vrsta. Iz prirode su sakupljeni punoglavci R. dalmatina, R. temporaria i B. bufo na ranim razvojnim stupnjevima. Taksonomska identifikacija izvršena je DNK barkoding metodom, primenom 16S rRNK markera. Metodama tradicionalne morfometrije je utvrđeno da relativna dužina i širina glave predstavljaju karaktere za razlikovanje rodova Rana i Bufo, dok je relativna dužina repa karakter za razlikovanje dve vrste mrkih žaba. Detaljnije analize oblika i veličine laboratorijski uspešno odgajanih punoglavaca R. dalmatina, R. temporaria i B. bufo vršene su metodama geometrijske i tradicionalne morfometrije na ranim stupnjevima razvića. Oba pristupa su dala slične rezultate kada su u pitanju kvantifikacija i opis varijabilnosti veličine i oblika. Za razliku od punoglavaca B. bufo, punoglavci dve vrste roda Rana su sitniji sa manjim telima i repovima dva puta dužim od tela. Kada su poređene dve vrste mrkih žaba, utvrđeno je da punoglavci R. dalmatina imaju kraći rep i veće telo. Međutim, suptilne razlike u obliku distalnog dela repa bilo je moguće detektovati samo primenom geometrijske morfometrije

Convergence Properties of the Waveform Relaxation Method as Applied to Electric Power Systems

Several theoretical results are presented and simple examples examined in order to determine the suitability of waveform relaxation for transient power system simulation. This examination leads to two practical suggestions that can easily be satisfied for power systems. The first is to break the simulation interval into sections, the first of which should be narrow and be used to kill off errors in the initial guess that activate the stiff modes. The second is to partition the system into subsystems that are stable, as this not only aids convergence but ensures multirate numerical stability

Transient Stability Simulation by Waveform Relaxation Methods

In this paper, a new methodology for power system dynamic response calculations is presented. The technique known as the waveform relaxation has been extensively used in transient analysis of VLSI circuits and it can take advantage of new architectures in computer systems such as parallel processors. The application in this paper is limited to swing equations of a large power system. Computational results are presented

Enzimska kinetička metoda za određivanje propranolol-hidrohlorida u farmaceutskim preparatima zasnovana na njegovom inhibitorskom delovanju na holinesterazu

Propranolol, a widely used beta-blocker, inhibits the hydrolysis reaction of enzyme cholinesterase. Measurements of the difference in rate of hydrolysis rate between uninhibited and inhibited reactions allow the development of a kinetic method for its determination. Both systems, enzyme-substrate-chromogen and enzyme-substrate-chromogen-inhibitor, were characterized through biochemical kinetic parameters (K-M, 0.326-0.330 mmol/L; V-max, 40.0-43.0 mu mol/Lmin). The inhibition type was recognized as competitive and the inhibition constant, Ki, was determined to be 22.60 mu mol/L. The detection and quantification limits were calculated as 0.004 and 0.0136 mu mol/L, respectively. Accuracy and precision of proposed methods were tested. The proposed method showed good sensitivity, selectivity, simplicity and rapidity, thus it is convenient for clinical applications.Za propranolol, često propisivani neselektivni beta blokator, utvrđeno je da inhibira reakciju enzimske hidrolize butiriltioholin-jodida, koja je katalizovana serumskom holinesterazom. Merenjem razlike u brzini osnovne i inhibitorske reakcije hidrolize u prisustvu propranolola kao inhibitora, moguće je razviti kinetičku metodu za određivanje propranolola. Oba sistema, enzim-supstrat-hromogen kao i enzim-supstrat-hromogen-inhibitor, okarakterisani su biohemijskim kinetičkim parametrima (KM, 0,326-0,330 mmol/L; Vmax, 40-42,99 μmol/L min), inhibicija je definisana kao kompetitivna i određena je konstanta inhibicije 22,60 μmol/L. Da bi se u potpunosti iskoristile sve mogućnosti predložene metode u pogledu osetljivosti, tačnosti, preciznosti i selektivnosti, optimizovani su reakcioni uslovi. Konstruisana je kalibraciona prava, izračunata odgovarajuća jednačina i određeni granica detekcije i kvantifikacije i to 0,004 i 0,0136 μmol/L, redom. Tačnost i preciznost predložene metode su ispitane za tri koncentracije propranolola u oblasti kalibracione prave (0,082-21,120 μmol/L) u pet ponavljanja. Takođe, ispitan je uticaj većeg broja supstanci koje se mogu naći u uzorku na brzinu reakcije. Optimizovana metoda je primenjena za određivanje propranolola u farmaceutskim preparatima. Tačnost predložene metode je ispitana primenom metode standardnog dodatka. Predložena metoda ima dobru osetljivost, selektivnost, jednostavna je i brza, i nadasve lako dostupna, i na taj način primenljiva u velikom broju laboratorija

Rat duodenal motility in vitro: Prokinetic effects of DL-homocysteine thiolactone and modulation of nitric oxide mediated inhibition

Homocysteine is a significant but modifiable risk factor for vascular diseases. As gastrointestinal smooth musculature is similar to blood vessel muscles, we investigated how elevated homocysteine levels affect nitric oxide-mediated neurotransmission in the gut. There is accumulated evidence that a dysfunction of NO neurons in the myenteric plexus may cause various diseases in the gastrointestinal tract such as achalasia, diabetic gastroparesis and infantile hypertrophic pyloric stenosis. In the present study, we aimed to assess the effects of homocysteine on NO-mediated responses in vitro, and to examine the effects of DL-homocysteine thiolactone on the spontaneous motility of rat duodenum and nitrergic neurotransmission. DL-homocysteine thiolactone concentration of 10 μmol/L leads to the immediate increase in tone, amplitude and frequency of spontaneous movements in isolated rat duodenum. L-NAME (30 μmol/L) leads to an increase in basal tone, amplitude and frequency of spontaneous contractions. The relaxations induced by EFS were significantly reduced in duodenal segments incubated in DL-homocysteine thiolactone compared with the control group. EFS-induced relaxations were inhibited by L-NAME in both experimental and control groups. These results suggest that a high level of homocysteine causes an important impairment of non-adrenergic non-cholinergic innervation of the rat duodenum. [Projekat Ministarstva nauke Republike Srbije, br. 175043