Voltage and load profiles estimation of distribution network using independent component analysis / Mashitah Mohd Hussain

This thesis presents research on voltage and load profiles estimation using independent component analysis technique. The uniqueness of this technique is limited information parameters on distribution system required. Usually voltage and load profiles are used as reference to electricity provider when supplying electricity to consumer on proper tariff. Thus, it is important to capture profiles accurately in order to avoid energy wastage and high cost for equipment installation. The work presented in this thesis is using statistical technique to predict voltage profile at source distribution system and load profiles on distribution system. Initially, the research focuses on three main tasks. First, voltage profile on source distribution system is estimated. The voltage profile is predicted using Independent Component Analysis (lCA) algorithm. The voltage profiles are estimated for 24- hours with time interval of 1 minute. Theoretically, when voltage source is controlled, the losses occur on the system is reduced. The task and analysis presented will help system loss their power while transmitting power from transmission to distribution system. Secondly, load profile in a multiple power flow solutions for every minute in 24 hours per day is estimated. A method to calculate multiple solutions of non linear profile is introduced. The Power System SimulationlEngineering (PSS@E) and python has been used to solve the load power flow. The result of this power flow solutions has been used to estimate the load profiles for each load buses using Independent Component Analysis (lCA) without any knowledge of parameter and network topology of the systems. The proposed algorithm is tested with IEEE 69 test bus system which represents the distribution part and the method of ICA has been programmed in MATLAB R2012b version. Next, an electrical load profiles is estimated using limited information to ensure proper power usage measurement of the customers. ICA technique is able to separate the mixed signal into their source signals. Using this method, the load profiles on feeder distribution can be estimated without any knowledge of the network topology and electrical parameters. In addition, a real-time load profiles on feeder distribution can be established instead of load modelling technique by using incoming distribution feeder data profiles. The ability of ICA algorithm to separate the profiles was evaluated. The work is focused on analysing the results of simulation using ICA method including voltage source control and electric losses of the system. Simulation results were obtained in Chapter 4.This thesis compares the result between original and estimated load profiles. Meanwhile, the result of voltage profile is tested on distribution system to investigate losses behaviour. The losses of simulation results with different tap changer and voltage set presented in first task are compared and discussed in this thesis. The estimation quality is verified by using error measures of the load profiles. All simulation results and errors of estimations are discussed in this thesis

Stability model integration for large scale solar photovoltaic system using Western electricity coordinating council model

Due to the increased demand for renewable energy, the interest in the large-scale solar photovoltaic (LSSPV) power plant has recently grown dramatically. However, when a large amount of electricity is produced from the LSSPV power plant to the grid interconnection, the system commonly experiences instability and thus disrupt the grid system in disturbance issues such as bus fault, line-to-line fault, three-phase fault, and tripping. This sudden disturbance occurrence is tended to interrupt the stability of the system from providing balanced electrical production within the electrical grid. A dynamics response from the simulation is used to study the stability and the behavior of the photovoltaic (PV) plant into the grid interconnection by developing 118 bus system. The observation of critical clearing time (CCT) duration shows that the result from the simulation where the duration takes less than t=15 s for the system to get back to its pre-fault condition in three-phase fault and tripping in a dynamic simulation to shows that the system reaches its stability been observed through the simulation result by using from user-specific models to generic models like those advocated by the Western electricity coordinating council (WECC) in power system simulator for engineering (PSSE) software

In vitro degradation study of novel HEC/PVA/collagen nanofibrous scaffold for skin tissue engineering applications

The aim of this study was focused on the degradation behavior of electrospun (hydroxyethyl cellulose/poly(vinyl) alcohol) HEC/PVA and HEC/PVA/collagen nanofibrous scaffolds, as a potential substrates for skin tissue engineering in two biologically related media: phosphate buffered solution (PBS) and Dulbecco's modified Eagle's medium (DMEM) for 12 weeks incubation period. The scaffolds were characterized at different degradation times by a series of analysis including pH changes of solutions, weight loss, swelling ratio, SEM, ATR-FTIR, DSC, TGA and mechanical properties. The results indicated that HEC/PVA/collagen scaffolds were exhibited slower degradation rate in both medium as compared to HEC/PVA blend nanofibers. All fibers displayed uneven and rough surfaces towards the final week of incubation in both PBS and DMEM solution. As degradation time increased, there were little changes in the chemical structure as determined by FTIR spectra while thermal studies revealed that the melting temperatures and crystallinity of scaffolds were slightly shifted to a lower value. Both HEC/PVA and HEC/PVA/collagen fibers showed significant decrease in Young's modulus and tensile stress over 12 weeks degradation. These results show that these nanofibrous scaffold demonstrate degradation behavior that meets the requirement as potential degradable biomaterials for dermal replacement

A facile synthesis method of hydroxyethyl cellulose-silver nanoparticle scaffolds for skin tissue engineering applications

Green porous and ecofriendly scaffolds have been considered as one of the potent candidates for tissue engineering substitutes. The objective of this study is to investigate the biocompatibility of hydroxyethyl cellulose (HEC)/silver nanoparticles (AgNPs), prepared by the green synthesis method as a potential host material for skin tissue applications. The substrates which contained varied concentrations of AgNO3 (0.4%–1.6%) were formed in the presence of HEC, were dissolved in a single step in water. The presence of AgNPs was confirmed visually by the change of color from colorless to dark brown, and was fabricated via freeze-drying technique. The outcomes exhibited significant porosity of > 80%, moderate degradation rate, and tremendous value of water absorption up to 1163% in all samples. These scaffolds of HEC/AgNPs were further characterized by SEM, UV–Vis, ATR-FTIR, TGA, and DSC. All scaffolds possessed open interconnected pore size in the range of 50–150 μm. The characteristic peaks of Ag in the UV–Vis spectra (417–421 nm) revealed the formation of AgNPs in the blend composite. ATR-FTIR curve showed new existing peak, which implies the oxidation of HEC in the cellulose derivatives. The DSC thermogram showed augmentation in Tg with increased AgNO3 concentration. Preliminary studies of cytotoxicity were carried out in vitro by implementation of the hFB cells on the scaffolds. The results substantiated low toxicity of HEC/AgNPs scaffolds, thus exhibiting an ideal characteristic in skin tissue engineering applications

Nanostructured material from hydroxyethyl cellulose for skin tissue engineering

tIn this study, a novel fibrous membrane of hydroxyethyl cellulose (HEC)/poly(vinyl alcohol) blend wassuccessfully fabricated by electrospinning technique and characterized. The concentration of HEC (5%)with PVA (15%) was optimized, blended in different ratios (30–50%) and electrospun to get smoothnanofibers. Nanofibrous membranes were made water insoluble by chemically cross-linking by glu-taraldehyde and used as scaffolds for the skin tissue engineering. The microstructure, morphology,mechanical and thermal properties of the blended HEC/PVA nanofibrous scaffolds were characterized byscanning electron microscope, Fourier transform infrared spectroscopy, differential scanning colorime-try, universal testing machine and thermogravimetric analysis. Cytotoxicity studies on these nanofibrousscaffolds were carried out using human melanoma cells by the MTT assays. The cells were able to attachand spread in the nanofibrous scaffolds as shown by the SEM images. These preliminary results showthat these nanofibrous scaffolds that supports cell adhesion and proliferation is promising for skin tissueengineering

Improved cellular response of chemically crosslinked collagen incorporated hydroxyethyl cellulose/poly(vinyl) alcohol nanofibers scaffold

The aim of this research is to develop biocompatible nanofibrous mats using hydroxyethyl cellulose with improved cellular adhesion profiles and stability and use these fibrous mats as potential scaffold for skin tissue engineering. Glutaraldehyde was used to treat the scaffolds water insoluble as well as improve their biostability for possible use in biomedical applications. Electrospinning of hydroxyethyl cellulose (5 wt%) with poly(vinyl alcohol) (15 wt%) incorporated with and without collagen was blended at (1:1:1) and (1:1) ratios, respectively, and was evaluated for optimal criteria as tissue engineering scaffolds. The nanofibrous mats were crosslinked and characterized by scanning electron microscope, Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. Scanning electron microscope images showed that the mean diameters of blend nanofibers were gradually increased after chemically crosslinking with glutaraldehyde. Fourier transform infrared spectroscopy was carried out to understand chemical interactions in the presence of aldehyde groups. Thermal characterization results showed that the stability of hydroxyethyl cellulose/poly(vinyl alcohol) and hydroxyethyl cellulose/poly(vinyl alcohol)/collagen nanofibers was increased with glutaraldehyde treatment. Studies on cell–scaffolds interaction were carried out by culturing human fibroblast (hFOB) cells on the nanofibers by assessing the growth, proliferation, and morphologies of cells. The scanning electron microscope results show that better cell proliferation and attachment appeared on hydroxyethyl cellulose/poly(vinyl alcohol)/ collagen substrates after 7 days of culturing, thus, promoting the potential of electrospun scaffolds as a promising candidate for tissue engineering applications

Fabrication, characterization and in vitro biocompatibility of electrospun hydroxyethyl cellulose/poly (vinyl) alcohol nanofibrous composite biomaterial for bone tissue engineering

Development of novel scaffold materials that mimic the extracellular matrix, architecturally and functionally, is becoming highly important to meet the demands of the advances in bone tissue engineering. This paper reports, the fabrication of natural polymer cellulose derived hydroxyethyl cellulose (HEC) based nanostructured scaffolds with uniform fiber morphology through electrospinning. Poly (vinyl alcohol) (PVA) was used as an ionic solvent for supporting the electrospinning of HEC. Scanning electron microscopy and ImageJ analysis revealed the formation of non-woven nanofibers with well-defined porous architecture. The interactions between HEC and PVA in the electrospun nanofibers were studied by differential scanning calorimetry, X-ray diffraction, dynamic mechanical analysis thermo-gravimetric analysis; Fourier transform-infrared spectroscopy, X-ray photoelectron spectroscopy and tensile test. The mechanical properties of scaffolds were significantly altered with different ratios of HEC/PVA. Further, the biocompatibility of HEC/PVA scaffolds was evaluated using human osteosarcoma cells. The SEM images revealed favorable cells attachment and spreading on the nanofibrous scaffolds and MTS assay showed increased cell proliferation after different time periods. Thus, these results indicate that HEC based nanofibrous scaffolds will be a promising candidate for bone tissue engineering