Search

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]

Textile and food industries produce a significant volume of effluents containing azo dyes and other pollutants. These effluents are serious environmental threats, and new methods for their treatment and for the degradation of azo dyes are thus attracting much attention. The current study deals with the oxidative degradation of azo dyes by meso‐tetrakis(1‐methylpyridinium‐4‐yl)prophyrinatoiron(III), [FeIII(tmpyp)], and meta‐chloroperoxy benzoic acid (m‐CPBA) in aqueous solution at room temperature. The catalytic degradation of azo dyes was investigated by using rapid‐scan stopped‐flow spectrophotometry as a function of solution pH, [catalyst], [m‐CPBA], [dye] and [surfactants]. To obtain mechanistic insight, the reaction between [FeIII(tmpyp)] and m‐CPBA was also studied in aqueous solution in absence of azo dyes. Spectral analyses and kinetic data show that [FeIII(tmpyp)] is transformed into the transient intermediate [FeIV(O)(tmpyp)].+ (a compound I analog) within 20–30 ms followed by the formation of relatively stable [FeIV(O)(tmpyp)] (a compound II analog). Batch experiments reveal that the dye degradation rate is influenced by the solution pH and the concentrations of [FeIII(tmpyp)], m‐CPBA, dye, and surfactants. On the basis of the kinetic and spectroscopic data, a mechanistic scheme for the dye degradation reaction and a steady‐state rate equation are proposed. The products resulting from oxidative degradation of the azo dye amaranth have been analyzed by HPLC‐UV‐HRMS. [ABSTRACT FROM AUTHOR]

Increasing penetration of photovoltaic (PV) generation may significantly impact existing voltage regulation schemes. In particular, the lack of coordination between control devices and fast change in PV generation can cause voltage magnitude to go beyond limits. This study addresses the issue by providing a novel real‐time centralised voltage control algorithm to tackle voltage fluctuations caused by variability of PV power generation. The new method considers autonomous response of upstream voltage regulation devices and provides optimised set‐points for the chosen downstream controllers. Furthermore, the investigated method was tested in the real‐time digital simulator on a model of 11 kV grid located in a semi‐rural area of Queensland, Australia. The control algorithm was designed in MATLAB with a multidimensional, non‐linear, mixed‐integer optimisation. The parallel computing implementation of the KNITRO optimiser helped to provide quicker and more accurate response than the existing uncoordinated control schemes. As a result, optimised control coordination leads to a substantial reduction in voltage fluctuations and decrease in regulation time. Moreover, the proposed method detects and eliminates unnecessary control operations. Thus, it can also prevent voltage hunting in distribution networks. [ABSTRACT FROM AUTHOR]

Power system security concerns due to significant wind generation could be twofold: first, the frequency response and second, the short‐circuit performance. Continuous development of wind energy may cause economic replacement and retirement of existing synchronous generators. Modern wind turbine generators do not inherently offer inertia and governor response after a disturbance, which may result in declining frequency response behaviour. Besides, they have limited fault current contribution, which may cause unacceptable short‐circuit ratio at the grid connection point of those wind power plants. Traditionally, frequency response and short‐circuit performance are individually improved. However, both of them are concurrently affected by high wind penetration. Hence, a common approach to simultaneously enhance both indices is essential. Therefore, this study introduces an idea of operating some of the retired synchronous generators in the synchronous condenser mode, which is termed as 'post‐retirement scheme (PRS)'. Such a second use of the retired synchronous generators can jointly upgrade frequency response and short‐circuit strength during high wind generation. This study also proposes a methodology to evaluate when and how much PRS should be deployed for ensuring an adequate security performance in a wind dominated power system. [ABSTRACT FROM AUTHOR]

With more photovoltaic (PV) systems being integrated into distribution networks, power utilities are facing many challenges in both planning and operation. Network operators are concerned with PV variability and associated necessity of voltage regulation, control coordination, reserve adequacy and dispatch constraints. While to address the obligatory connection agreement, it is vital for PV farm owners to accurately estimate PV variability and then provide the most cost‐effective compensation method. In the literature, PV variability of different scales has been investigated over the last 20 years. However, little has focused on output fluctuations of PV systems with long‐term and high‐resolution recorded data at a low‐voltage distribution feeder level where voltage regulation has become a serious issue. This is particularly true in Australia, where PV penetration is growing in many states and is expected to grow further in the near future. This study utilises the data of a distributed 1.2 MWp PV system in the University of Queensland recorded over the last three years with 1‐min resolution to analyse the statistical characteristics of PV power variability. The results from this study will provide very useful information for both power utilities and solar farm owners regarding network operation and future PV system development. [ABSTRACT FROM AUTHOR]

Prompted by technical issues that have arisen due to the widespread deployment of distributed intermittent renewable generators, rapidly rising peak demand and reductions in battery price, the use of battery‐based energy storage systems in power networks is on the rise. While battery‐based energy storage has the potential to deliver technical benefits, the best possible sizing, location and usage govern the financial viability. The objective of this study is twofold. Firstly, a generalised approach is proposed to model network upgrade deferral as a function of load growth rate, renewable generation penetration and peak shave fraction. This model is then used for the formulation of an optimisation problem which benefits from multi‐period power flow analysis to co‐optimise battery size, location, charge/discharge profile for a pre‐specified number of units to be deployed in a given distribution network. The proposed approach is implemented using the generic algebraic modelling system platform and validated on an Australian medium voltage distribution network under multiple practical and potential future scenarios. [ABSTRACT FROM AUTHOR]

Solar photovoltaic (PV) system installations are rapidly increasing in distribution networks. These PV systems include power electronic devices which have an influence on the power quality of the grid in the form of harmonic distortion. The aim of this study is the harmonic impact of PV systems on distribution networks. A comprehensive harmonic behaviour analysis has been performed on the IEEE-13 bus distribution network with high PV systems penetration. A certain level of harmonics is also injected into the IEEE network through non-linear loads to resemble a realistic scenario. The investigation has been carried out through simulations of three case studies, namely PV system integrations at a single node in particular with and without the presence of background distortions in the supply and finally PV penetration at multiple nodes with supply distortions. Furthermore, an evaluation study has been conducted at the University of Queensland PV site to validate simulation results. This study has highlighted the PV systems harmonic contributions on real distribution networks and the impact of harmonics propagation on transformer K-factor. Results show that the total harmonic distortions of current and voltage are exceeding the limits when the number of PV systems increases, leading to transformer overloading and heating. [ABSTRACT FROM AUTHOR]

Fault current limiters are playing an ever more important role in today's power systems and many of their different types have now reached maturity. Owing to the progress in superconducting technology, the superconducting fault current limiter (SFCL) has attracted increasing attentions. To investigate the efficacy of SFCL devices from a system point of view, the fault current limiting impedance is of great importance. This study proposed an improved structure of flux‐lock type of SFCL and compares the current limiting impedance of different layouts. It focuses on the impacts of iron core shape on primary winding inductance. The analyses include simulations based on finite element method carried out in the simulation software ANAlysis SYStem (ANSYS). This study shows that an E–E‐shaped core with an air gap is better than a closed core when being used for an SFCL. It is also found that for an iron core SFCL with fixed size, its rated fault current limiting impedance can be adjusted by changing the cross‐sectional area of the iron core centre leg and the length of the air gap. [ABSTRACT FROM AUTHOR]

In many countries, it is common for medium voltage (MV) and low voltage (LV) to share the same pole and power line corridor, and this has been a general practice for decades. The MV line and the LV line separation distance may be short under some situations; therefore the mutual coupling may become substantial, which can have a significant impact on network voltages. In the literature, such coupling effect is generally ignored, and there is a lack of a detailed model of the coupled MV and LV lines for incorporation into load flow programs. This study develops a model for unbalanced distribution lines considering the mutual coupling between different voltage levels. Then the established model is utilised in a current injection load flow program to analyse the MV/LV coupling impacts on distribution system voltage. [ABSTRACT FROM AUTHOR]

To achieve renewable energy targets, more wind turbine generators (WTGs) are being integrated into many power networks around the world. However, unlike traditional synchronous generators, modern WTGs are driven by power electronic devices which provide almost zero inertia and frequency response to frequency related events such as generator tripping. Wind manufacturers and researchers have been working on synthetic WTG inertia support, which can better utilise the rotational nature of WTGs. However, synthetic inertia alone may be insufficient under certain circumstances to prevent automatic under frequency load shedding after generation tripping, which causes security concerns for network operation. Consequently, WTG active power control (APC, similar to governor control) should be activated to improve network security. However, APC will costly reduce WTG output from the maximum power point and result in financial concerns. Therefore when and how much APC service should be activated becomes an extremely important question, which has not been addressed in the literature. This study develops a new method to quickly estimate frequency response caused by generator tripping hence system operators can use this proposed method to continuously evaluate inertia and headroom competency and accordingly activate the amount of WTG inertia and APC required for reliable system operation. [ABSTRACT FROM AUTHOR]

In this study, a hybrid inductive and active filtering (HIAF) method is proposed to dampen the harmonic resonance in distribution network with non-linear loads. At a first, a new topology of energy conversion system with active technique, which includes an inductively filtered converter transformer, fully-tuned branches and a controlled voltage source inverter (VSI), is proposed for large-power non-linear loads. The working principle of such a new topology is described, and the advantage of damping harmonic resonance of the distribution network is revealed by means of mathematical modelling and theoretical analysis. Then, the control system of VSI is designed with the multiple purposes of damping harmonic resonance from the grid side and isolating harmonic currents from the non-linear load side. A case study is carried out to validate theoretical results. By comparing with the traditional hybrid active filtering method and the passive filtering method, it indicates that the proposed HIAF method is more effective to dampen harmonic resonance in the distribution network and at the same time is able to significantly reduce the harmonic contents in the grid winding, which is good to both the public network and the energy conversion system connected with large-power non-linear loads. [ABSTRACT FROM AUTHOR]

A hybrid multi‐terminal HVDC (MTDC) scheme combines line commutated converter and voltage source converter technologies for HVDC transmission system. This study presents a comprehensive design of wide‐area power oscillation damper (POD) controller for the hybrid MTDC system. The process consists of input/output selection and parameter tuning for the POD of the hybrid MTDC based on the linearised black‐box model. The objective is to choose an effective control loop to damp the critical mode, which does not have negative impacts on the other modes in the system. For this purpose, a new index, named relative joint interaction index, is proposed for the input/output selection. Afterward, the parameter of POD is tuned using residue‐based phase compensation technique because of its practical application. Finally, non‐linear simulations are also carried out to verify the effectiveness of the designed POD in different loading conditions. [ABSTRACT FROM AUTHOR]