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Wind energy is becoming a significant source of generation in many countries because of its zero fuel cost and no air pollution. Due to integration of large-scale wind power in conventional grids, synchronous generators are being economically replaced. Modern wind farms are based on power electronics interface; and unlike synchronous generators, they do not have inherent frequency support capability. So, in a combined synchronous and non-synchronous machine based power system, it has always been a concern for a network operator to maintain system frequency within acceptable limits following a major disturbance. From power system security point of view, wind penetration can be limited by frequency response criteria. Up to now, several methodologies have been proposed to estimate maximum threshold of wind integration. However, none of them recommends how a system operator could be immediately informed about a secured wind penetration limit, as soon as generation profile is known. This paper proposes a new estimation tool of maximum wind penetration level from the frequency response adequacy point of view. Available system information viz. inertia and headroom are used as input parameters in the developed tool. Output of this tool will provide the highest margin of wind power that can be integrated at a particular load condition without violating frequency response constraints. The proposed technique is applied and analysed for a 250 bus, 65 machine Australian electricity network. [ABSTRACT FROM AUTHOR]

• A two-stage security-constrained economic dispatch model is proposed to exploit the inherent grid flexibility. • A joint chance constraints-based method is developed to efficiently utilize dynamic line rating while handling its uncertainty. • The post-outage setpoint adjustments of flexible ac transmission systems are extended from N-1 to N-K contingencies. • Computational tractability is attained by a nested column-and-constraint generation algorithm. Dynamic line rating (DLR) and flexible ac transmission system (FACTS) are two technologies to enhance the utilization of existing transmission lines and exploit the inherent transmission-side flexibility. This paper coordinates DLR and FACTS in a two-stage security-constrained economic dispatch (SCED) model to enhance the power system flexibility in N-K contingency management and reduce operational cost. To utilize DLR while handling its uncertainty, spatial–temporal joint chance constraints (JCCs) are used. A scalable reformulation method for these JCCs is developed, which enables considering the spatial–temporal correlations between DLRs and co-optimizing the DLR utilization with system dispatch. To leverage the flexibility of FACTS, the adjustments of FACTS set points before and after the occurrence of any N-K line outage are modelled. The proposed SCED model is reformulated as a triple-level robust model, which avoids enumerating all possible N-K outages in the SCED model and obtains a more reasonable model size. To handle the presence of binary variables in the lowest level of the robust model, a nested column-and-constraint generation solution structure is designed. Case studies on IEEE 14 and 118-bus systems are conducted to verify the effectiveness of the proposed SCED model. [ABSTRACT FROM AUTHOR]

This paper proposes a novel data driven framework for detecting topology transitions in a distribution network. The framework analyzes data from phasor measurement units (PMUs) and relies on the fact that changes in network topology results in changes in the structure and admittance of the network. Using voltage and current phasors recorded by PMUs, the proposed method approximates network parameters using an ensemble-based deep learning model and thus, it does not require any knowledge of network parameters and load models. Using the prediction error of the proposed model, a connectivity matrix which shows the status of switches is constructed. In contrast to other methods, this proposed framework does not require a library of voltage and current transients associated with possible network transitions. It can also detect simultaneous switching actions and is robust to noise and load variations. The model yields a lower error detection rate, and its performance is validated using a modified version of the IEEE 33 bus network and a real feeder located in Queensland, Australia, under full and partial observability conditions. The proposed model has also been compared with another data driven method in terms of inference time and error detection rates. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis (RA), a chronic inflammatory disease, and its exact aetiology is not defined clearly. The free radicals produced in large amount in RA are associated with alteration in molecular structure resulting in glycation of proteins. As a result of glycation, advanced glycation end products (AGEs) produced. In this study, collagen type II suspension was injected into Wistar rats to make RA model of rats. Simultaneously, hesperidin 50 mg kg−1 body weight was orally administrated to the rats for 21 days. X‐rays of the rat hind paws were analyzed and found to be significantly effective against bone loss after treatment with hesperindin. Nε‐(carboxymethyl)lysine (CML) and pentosidine (PTD) concentrations in collagen‐induced RA plasma were determined as 565.29 ± 30.15 and 37.23 ± 1.02 ng ml−1, respectively, while CML and PTD in IgG were 6.63 ± 0.44 ng mg−1 IgG and 425.33 ± 37.26 ng g−1 IgG, respectively. After treatment with hesperidin, the elevated levels of CML in plasma and in IgG were significantly (p < 0.001) lowered to 450.95 ± 15.05 mg ml−1 and 5.23 ± 0.27 ng mg−1 IgG, respectively. Similarly, concentrations of PTD in plasma and IgG of rats treated with hesperidin were 28.46 ± 1.20 ng ml−1 and 359.35 ± 31.11 ng g−1 IgG, respectively. Thus, after treatment with drug, plasma CML and IgG PTD levels were restored as 93% and 16%, respectively, through free radical scavenging activity of hesperidin resulting in alleviation of RA disease by decreasing the AGEs concentrations. Therefore, use of hesperidin may be useful to alleviate severity of RA disease. Significance statement: Collagen type II suspension was used to make a rheumatoid arthritis model of rat.Hesperidin treatment was effective against bone loss.Hesperidin effectively reduced the concentrations of advanced glycation end products like Nε‐(carboxymethyl)lysine and pentosidine.Treatment with hesperidin resulted in the alleviation of rheumatoid arthritis disease through free radical scavenging and antiglycation activities.Hesperidin may be useful to alleviate the severity of rheumatoid arthritis disease. [ABSTRACT FROM AUTHOR]

Silver sulphide corrosion is a recently identified failure mechanism of transformer onload tap changers (OLTC). The corrosive sulphur in transformer oil reacts with the silver coated components of OLTC tap selector and forms silver sulphide films. During OLTC operation, the silver sulphide flakes can be detached from the tap selector and mix with the transformer oil. The silver sulphide is a semi conductive material. As a result, the dielectric strength in the transformer oil around the OLTC silver coated contacts or elsewhere in the transformer, wherever the semi conductive particles travel, will be reduced. Eventually, due to either high electric field stress or aged oil with a low dielectric strength, oil breakdown can occur between adjacent contacts. This can cause a catastrophic failure of the OLTC and quite often the tapping winding as well. Since such failures affect the transformer reliability, utilities are interested in methods of detecting and mitigating silver sulphide corrosion on OLTCs. This paper presents a risk assessment criterion to identify the degree of significance of silver sulphide corrosion in transformers using existing diagnostic techniques. [ABSTRACT FROM AUTHOR]

Partial discharge (PD) signals acquired from on-line measurements of power transformers are easily overwhelmed by various interference and noise. This paper proposes an automatic blind equalization (BE) and morphological thresholding method for PD signal de-noising. Firstly, BE automatically selects an equalized signal that reveals PD impulses from an acquired noise-corrupted signal. Then, automatic morphological thresholding (AMT) is adopted for determining thresholds on the equalized signal. After de-noising with BE and AMT, phase-resolved pulse sequence (PRPS) is constructed and used for analyzing the types of insulation defects that cause discharges. To verify the proposed method, PD measurements on experimental PD models and a distribution transformer have been conducted. The results show that PD impulses can be extracted from severely noise-corrupted signals by using the proposed method. Also, PRPS constructed from de-noised signals can achieve consistency in revealing the types of insulation defects even different types of PD sensors and measurement systems are used. [ABSTRACT FROM AUTHOR]

An environment-friendly efficient adsorbent, hexadecyltrimethylammonium bromide-modified rice husk (CTAB-RH), was chosen to eliminate anionic azo dye amaranth from aqueous solution. The newly synthesized adsorbent CTAB-RH was characterized by the Fourier transform infrared spectroscopy. The point of zero charge (pHpzc) value of CTAB-RH was estimated to be 5.85. Amaranth adsorption onto CTAB-RH was proven by the observations of field emission scanning electron microscopy (FE-SEM) coupling with energy dispersive X-ray spectroscopy (EDX). Adsorption kinetic experiments were conducted at the various contact time, solution pH, dye concentrations in solution, ionic strengths, and temperatures, respectively. The maximum dye adsorption was observed at pH 2. Amaranth adsorption kinetic data pursued a pseudo-second-order kinetic model. Equilibrium adsorption data followed the Langmuir isotherm model with a maximum 125 µmol/g dye adsorption capacity of CTAB-RH at 45°C. The activation energy of the present dye adsorption process was determined to be 18.71 kJ/mol. Thermodynamic study indicates that the amaranth dye adsorption onto CTAB-RH is a spontaneous endothermic process. Desorption of amaranth from dye-loaded CTAB-RH was performed in NaOH solution (pH 13) and finally, the recycled CTAB-RH was used without significant loss of its adsorption capacity. [ABSTRACT FROM AUTHOR]

Highlights: [•] This paper investigates the impacts of PV power variability on voltage regulation. [•] Quasi-Static Time-Series method and recorded yearlong data are used in this study. [•] It is found a small DSTATCOM can significantly reduce OLTC tap changes. [•] Consequently OLTC maintenance cost will decrease. [•] The proposed strategy can be used to evaluate solutions for voltage regulation. [ABSTRACT FROM AUTHOR]

Inverter transformers are one of the key components in a PV plant and their operating patterns are considerably different from that of transformers in a substation. Moreover, these transformers experience higher level of harmonics generated by the inverters. Therefore, investigating the ageing profile of the inverter transformer is a timely requirement. In this paper, the ageing of inverter transformers in a medium-scale solar PV plant is studied by utilizing various real-time measurements including load current, top-oil temperature (TOT), ambient temperature, moisture in top oil, solar irradiance and individual current harmonics. An updated moisture-dependent thermal model (MDTMH), with consideration of current harmonics is developed to estimate the hot-spot temperature (HST). The influence of weather conditions, which directly determine the load current of inverter transformers on the loss of life (LOL) of an inverter transformer is also investigated. Furthermore, the effect of current harmonics levels on the inverter transformer's HST and LOL is explored. Finally, comparisons of HST and LOL of inverter transformers connected to PV arrays with three different tracking technologies, i.e., fixed-tilt, single-axis and Dual-axis PV arrays are performed. [ABSTRACT FROM AUTHOR]

Abstract: Market power refers to the ability of generators in influencing the energy prices above competitive level to obtain more profits. It may be the cause of transmission congestion that limits transfer capability in an interconnected area. Hence an independent system operator (ISO) must be able to detect the conditions in which market power has been practiced to guarantee a secure competition and economical operation of the electricity market. To cope up with transmission congestion to assess market power, an optimal power flow (OPF) based on shift-factor methodology to find out a new indicator, called congestion-based dynamic dispatch index has been proposed. One of the beneficial feature of the proposed method is the ability to recognise accurately the most potential generator to exercise the market power. A generator bidding scheme represented by financial withheld strategy is then utilised to investigate the dynamic condition of power market. An analysis on the power market performance to identify potential generators in exercising market power is also presented. The results show that transmission congestion condition may be created unnaturally by this particular bidding strategy. It prevents some cheap generators to supply their outputs and allows all more expensive generators within the congested zone to gain more profits at the cost of other market participants. [Copyright &y& Elsevier]

The structural and functional analogy between difluoromethylene bisphosphonate (CF2PP) and pyrophosphate (PPi) is investigated in a reaction with V(V) in the form of vanadate. The reaction of CF2PP with vanadate was investigated using 1.00 M KCI as supporting electrolyte over the ranges 3 ≤ [CF2PP] ≤ 60 mM and 2.06 ≤ pH ≤ 11.80. 51V, 19F, and 31P NMR spectroscopic studies showed that a 1:1 species was formed with an H+-dependent formation constant of 110 M-1 at pH 7.22. Results of solution experiments and ab initio calculations are consistent with CF2PP coordinating V(V) in a bidentate manner, as previously reported for PPi. Below pH 4, a minor complex forms, which is consistent with a 1:2 stoichiometry. This complex was also observed with pyrophosphate. The X-ray crystal structure of the monoprotonated difluoromethylene bisphosphonate anion (H[CF2PP}3-)-toludine complex is presented. The H[CF2PP]3- anion crystallized in the triclinic space group P1 with a = 12.7629(7) Å, b = 13.3992- (7) Å, c = 17.1002(9) Å, and V = 2584.4(2) ų, and Z = 2. Sheets of the layers of anions are connected through a network of H-bonds and separated by a layer of toludine cations. The structural features are investigated, and the CF2PP anion was found to be longer and wider than the corresponding PPi. Given the larger size of this anion compared to PP, the chelation affinity upon CF2 substitution was found to be 4-5-fold reduced at neutral pH. [ABSTRACT FROM AUTHOR]

Conjugation of insulin-mimetic [meso-tetrakis(4-sulfonatophenyl)porphyrinato]Zn(II), Zn(tpps), with chitosan was examined in aqueous solution at various contact time, Zn(tpps) concentrations and solution temperatures, respectively. The chitosan–Zn(tpps) conjugate was characterized by UV–Vis and Fourier transform infrared (FTIR) spectroscopic techniques. The electrostatic interaction between negatively charged sulfonate (SO 3 -) groups of Zn(tpps) and positively charged amino ( NH 3 + ) groups of chitosan is responsible for the formation of chitosan–Zn(tpps) conjugate. Chitosan efficiently inhibits the demetallization and aggregation of Zn(tpps) in acidic aqueous solution. The conjugation kinetic data taken from various batch studies were examined by the pseudo-first-order, pseudo-second-order, Elovich kinetic, film diffusion and intra-particle diffusion models. The equilibrium conjugation isotherms were analyzed by Freundlich, Temkin and Langmuir isotherm models, respectively. The batch conjugation kinetic data were obeyed by the pseudo-second-order kinetic model rather than the pseudo-first-order and Elovich kinetic models. Equilibrium conjugation isotherms were explained well by the Langmuir isotherm model, and the highest extent of Zn(tpps) bound to chitosan was obtained to be 151.52 µmol/g at 45 °C. The activation energy (Ea: 10.21 kJ/mol), changes in Gibb's free energy (∆G: –26.38 to –28.12 kJ/mol), enthalpy (∆H: 8.74 kJ/mol) and entropy (∆S: 115.94 J/mol K) suggest that the chitosan–Zn(tpps) conjugation is an endothermic spontaneous process. The in vitro release of Zn(tpps) from chitosan–Zn(tpps) conjugate was investigated in phosphate buffer solution (pH 7.4) at 37 °C. The kinetics of Zn(tpps) release followed the first-order kinetics with a rate constant 0.0025 h‒1. The chitosan–Zn(tpps) conjugate may be used as an oral therapeutics for diabetes mellitus. [ABSTRACT FROM AUTHOR]

This article proposes a novel algorithm employing space vector ellipse (SVE) in a complex plane to classify and visualize power quality disturbance-events (PQDEs). In the proposed method, at first, the time-domain signal and a reference signal, which are separated by 90°, are mapped in a complex 2D coordinates. Thus, the tip of resultant rotating vector traces an ellipse, from which three parameters, namely, semi-major axis, semi-minor axis and inclination angle, are obtained. Then, the ellipse parameters are exploited to classify and visualize nine types of PQDEs, namely, voltage sag, swell, interruption, harmonic, sag-harmonic, swell-harmonic, notch, flicker and transient. To validate the practicability of the proposed approach, an extensive real-time simulation study is carried out on RTDS platform using a test microgrid network to generate a large number of PQDEs. The test events were successfully classified and visualized in complex plane. Moreover, the noisy and practical signals, recorded by IEEE 1159.2 Working Group, were successfully classified to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The binding of zinc(II) ions onto γ-pga was studied in aqueous solution as a function of contact time, solution pH, initial concentration of metal ion, and solution temperature, respectively. IR and 13C NMR spectra of γ-pga and Zn(γ-pga) complex revealed binding of zinc(II) with carboxylate and amide groups on γ-pga. The strong interaction between zinc(II) ions and γ-pga occurred at pH 5. The binding kinetic data followed a pseudo-second-order kinetic model. The equilibrium binding data were fitted well by Langmuir isotherm model. The maximum amount of zinc(II) ions bound to γ-pga was estimated to be 13.97 mmol/g at 30 °C and 20.58 mmol/g at 45 °C. The values of activation energy (Ea 18.23 kJ/mol), changes in free energy (∆G°), enthalpy (∆H°), and entropy (∆S°) indicate that the formation of Zn(γ-pga) complex is an endothermic spontaneous physisorption process. The antimicrobial activity of Zn(γ-pga) complex was examined against a gram-negative bacteria (i.e., Escherichia coli) and a gram-positive bacteria (i.e., Bacillus subtilis). The IC50 values of Zn(γ-pga) complex were estimated to be (0.76 ± 0.03) mmol/L for E. coli and (0.94 ± 0.02) mmol/L for B. subtilis, respectively. Therefore, Zn(γ-pga) complex can be used as an antimicrobial agent against gram-positive and gram-negative microorganisms. [ABSTRACT FROM AUTHOR]

Grid-edge distributed energy resources (DERs) present both operational challenges and opportunities to distribution system operators (DSO). This paper presents a day-ahead scheduling strategy for DER-rich active distribution networks to leverage operational flexibilities of various DERs for effective network management. The scheduling strategy is realized based on a DSO-centric day-ahead market model that incorporates a multi-period and two-stage optimal power flow (OPF) model to determine scheduling and pricing for network and non-network DERs. The uncertainties in day-ahead operation stemming from local generation, load consumption, and market prices are robustly considered for hedging the intermittency and forecasting uncertainties. A novel bid price function is proposed for local distributed solar PV generation aiming at maximizing participation in network service. A new reactive power management and pricing scheme is also presented for optimal scheduling of voltage support devices within distribution network. The proposed framework is implemented on IEEE-33 bus balanced test system and operational planning strategy is analyzed for overall cost-benefits of the system at various uncertainty levels. A 7-10 percent saving in cost of procurement for DSO can be accrued at various uncertainty levels, and a 10 percent increase in revenue for the PV generation can be observed. • An optimal and sustainable operational planning for the DSO is proposed. • The proposed framework uses day-ahead model for operational planning of DERs. • The uncertainties in market prices, load, and PV generation are considered. • A new reactive power management strategy for fair pricing is proposed. • The proposed framework incentivizes older PV technologies with higher marginal prices. [ABSTRACT FROM AUTHOR]

• The proposed method can solve voltage issues and enable higher PV penetration. • PV imbalance makes traditional methods less effective on overvoltage mitigation. • A joint centralized-decentralized method is developed for unbalanced PV scenarios. • The new approach controls fast PV fluctuations in a coordinated and distributed way. Due to random connection of small-size single-phase rooftop photovoltaic (PV) generators in residential areas, low voltage distribution systems tend to have unbalanced PV integration across phases. In such situations, traditional reactive power compensation methods may cause unintended Voltage-Reactive Power responses across phases due to line coupling, which consequently affects their effectiveness on overvoltage mitigation. Such overvoltage problems significantly hinder the future integration of clean and renewable solar energy resources in power networks. In this paper, the limitations of traditional methods in PV imbalance scenarios are revealed and comprehensively analyzed by a voltage sensitivity method for the first time. On this basis, an innovative joint centralized-decentralized method is developed to overcome the PV imbalance-induced voltage regulation challenge. Specifically, the inverter's reactive power response to PV power variations in different phases is adaptively scheduled in order to avoid adverse effect of inter-phase Voltage-Reactive Power interaction on voltage regulation. The effectiveness of the proposed method is validated by time-series simulations with recorded data and a real-life low voltage distribution system in Australia. With the traditional method (i.e. power factor droop control strategy), 93 minutes' overvoltage can be observed in the case study, which will trigger overvoltage protection and disconnect PV inverters from the grid. While, the proposed method can always control the system voltage within the allowable range, and it consequently avoids PV disconnection. By solving this bottleneck issue, more PV systems can be integrated into distribution networks, which consequently contributes to CO 2 emission reduction in future. [ABSTRACT FROM AUTHOR]

Broadband responses under random excitations can reflect the modal characteristics of a structure. This paper investigates the applicability of operational modal analysis (OMA) to extract modal parameters of transformer windings under random excitations. Firstly, random vibration signals are extracted from measured vibration signals by estimating an accurate power frequency and eliminating vibration harmonics. Then, modal characteristics are obtained by applying OMA to the extracted random vibration signals. The numeric study on a winding axial vibration model demonstrates the effectiveness of the proposed method in obtaining its modal characteristics. Laboratory experiments show that the natural frequencies calculated by OMA are a subset of the actual natural frequencies of windings and the tank. The field test results of a 110 kV power transformer show that the number of natural frequencies increase when winding deformation occurs. OMA of transformer windings may pave a way for online winding condition monitoring. [ABSTRACT FROM AUTHOR]

There are more large-scale photovoltaic (PV) plants being established in rural areas due to availability of low-priced land. However, distribution grids in such areas traditionally have feeders with low X/R ratios, which makes the independent reactive power compensation method less effective on voltage regulation. Consequently, upstream step voltage regulator (SVR) may suffer from excessive tap operations with PV-induced fast voltage fluctuations. Although a battery energy storage system (BESS) can successfully smooth PV generation, frequent charge/discharge will substantially affect its cost effectiveness. In this paper, a real-time method is designed to coordinate PV inverters and BESS for voltage regulation. To keep up with fast fluctuations of PV power, this method will be executed in each 5 s control cycle. In addition, charging/discharging power of BESS is adaptively retuned by an active adjustment method in order to avoid BESS premature energy exhaustion in a long run. Finally, through a voltage margin control scheme, the upstream SVR and downstream PV inverters and BESS are coordinated for voltage regulation without any communication. This research is validated via a real-time digital simulator MatLab cosimulation platform, and it will provide valuable insights and applicable strategies to both utilities and PV owners for large-scale PV farm integration into rural networks. [ABSTRACT FROM PUBLISHER]

This paper studies an interdisciplinary approach for improving building energy efficiency. In particular, the proposed approach integrates design innovation (DI) techniques, existing energy audit methods (EAM), and data-driven & engineering modeling techniques (DET) in the process of sustainable smart energy system design. From this perspective, DI methods are extended and modified to suit the content of sustainable smart energy system design and a DI 4D (Discover, Define, Develop and Deliver) framework is introduced to guide the design process. The motivation behind and the implementation procedure of each of the DI phases is explained separately, and the process of integrating DI methods, EAM and DET in developing a sustainable smart energy system is demonstrated. The proposed approach is deployed within the campus of a tertiary education institution to show its effectiveness in designing a smart sustainable energy system. • A design innovation (DI) approach is proposed for smart energy system design. • A comprehensive background of the proposed DI framework is provided. • How DI can be used to design smart energy system is demonstrated. • Experimental case studies are provided to show the benefit of the proposed scheme. [ABSTRACT FROM AUTHOR]