Modeling and simulation of grid-connected solar photovoltaic systems with D-statcom and dvr to improve stability in distribution system

Electrical utilities face problems such as the rising cost of electricity, aging equipment, increasing demand for electricity, regulating frequency, and the difficulties of incorporating renewables into the grid. The accumulated global photovoltaic (PV) particularly the installation of Grid-Connected Solar Photovoltaic (GCPV) systems has been exponentially expanding around the world. However, as the PV penetration and global PV market have recently grown, there are challenges to the utility companies regarding the power quality and the reliability of the system. This is because the integration of power electronics has raised concerns about the safe operation and protection of the equipment. Hence, the feasible solution to solve these problems is installing Distributed Flexible AC Transmission System (D-FACTS) devices to the distribution grid through the point of common coupling (PCC). The purpose of this project is to model and simulate 100 kW and 250 kW solar PV systems that are connected to the utility distribution system with and without Distribution Static Synchronous Compensator (D-STATCOM) and Dynamic Voltage Restorer (DVR) under normal and faults condition in MATLAB/ Simulink. The test systems consist of a PV array that is connected in series and parallel modules, a DC-DC Boost Converter, Maximum Power Point Tracking (MPPT) control, DC-AC inverter, inverter control, filter, three-phase load, distribution transformer, and grid equipment. The grid operates test systems I and II at the nominal three-phase line to line voltage of 260 V, supplied from 100 kVA and 250 kVA 25/ 0.26 kV distribution transformer. The test system I and II are tested with the Perturb and Observe technique. The simulation results showed that the installation of D-STATCOM and DVR in GCPV systems improved 80-90% of the output power from the PV systems, and stabilized the level of the RMS voltage and current within 5% of its nominal value at the distribution feeder under normal and fault conditions. The implementation of D-FACTS devices in GCPV systems will be beneficial for future power system stability studies in the distribution syste

Environmental degradation of durian skin nanofibre biocomposite

The effect of ultraviolet radiation on tensile properties, water absorption and optical properties of polypropylene (PP) reinforced with durian skin nanofibre (DSNF) composites was investigated. DSNF was obtained from fermentation of durian skin fibre using Rhizopus oryzae. X-ray diffraction (XRD) analysis and Sherrer equation were applied to measure the average particle size of DSNF which was determined as 51.2 nm. PP and DSNF were melt-blended in a Haake internal mixer before compression moulded into composite specimens. The composites were exposed under ultraviolet (UV) radiation to simulate the effect of sunlight. The significant effect of maleic anhydride polypropylene (MAPP) was observed by the improvement recorded in tensile properties and reduction of water absorption in PP/DSNF composite. The colour index of composites increased with UV radiation exposure. Transmission electron microscope (TEM) images showed DSNF was well-dispersed in PP matrix in the presence of MAPP. Kesan ultraungu (UV) terhadap sifat tegangan, penyerapan air dan sifat optik bagi polypropylene (PP) diperkuatkan dengan nanofiber kulit durian komposit telah disiasat. DSNF telah diperolehi daripada process penapaian fiber kulit durian menggunakan Rhizopus oryzae. Analisis difraksi sinar-x dan persamaan Sherrer telah digunakan untuk mengukur purata saiz zarah untuk DSNFyang telah diperolehi sebanyak 51.2nm. PP dan DSNF telah dicampur dalam pembancuh Haake sebelum mampatan dibentuk menjadi spesimen komposit. Komposit telah didedahkan di bawah radiasi ultraungu (UV) untuk mensimulasikan kesan cahaya matahari. Kesan yang penting terhadap polipropilena maleik (MAPP) telah diperhatikan dan setiap peningkatan dalam sifat tegangan dan pengurangan penyerapan air dalam komposit PP / DSNF telah direkod. Indeks warna komposit meningkat dengan pendedahan radiasi UV. Imej mikroskop elektron penghantaran (TEM) menunjukkan DSNF telah disebarkan dengan baik dalam matriks PP dengan kehadiran MAPP

Effect of coupling agent on durian skin fibre nanocomposite reinforced polypropylene

This paper reports on the development of a composite-based natural fiber to reduce the reliance on petroleum-based product in order to amplify environmental awareness. The production of Durian Skin Nanofiber (DSNF) was conducted using biological fermentation method via rhizopus oryzae in order to obtain the nano dimension of the particle size. Polypropylene (PP) and DSNF were produced using Haake internal mixer via melt blending technique. The significant effect of maleic anhydride grafted polypropylene (MAPP) on the properties of PP/DSNF nanocomposite was investigated to study its mechanical properties which are tensile strength and thermal stability using thermogravimetric (TGA) and differential scanning analysis (DSC). The tensile property of PP nanocomposites increased from 33 MPa to 38 MPa with the presence of MAPP. The addition of MAPP also increased the thermal stability of PP/DSNF nanocomposite where the char residue increased by 52%. Besides that, the thermal degradation of PP/DSNF and PP/DSNF-MAPP were higher than PP where they exerted higher amount of weight loss at an elevated temperature. The percentage of crystallinity, %Xc, of PP nanocomposites improved with the addition of MAPP by 35% based on the differential scanning calorimetry (DSC) result. The SEM analysis showed that the PP/DSNF-MAPP exerts ductile fracture while PP/DSNF exerts brittle fracture

Effects of plasticizer on mechanical properties of durian skin fiber reinforced polylactic acid biocomposite

This study focus on reinforcing of durian skin fiber (DSF) and polylactic acid (PLA) for food packaging. Epoxidized palm oil (EPO) was used as a plasticizer to enhance the properties of the biocomposite. The biocomposite was fabricated by extrusion and injection molding processes. The tensile properties of PLA/DSF with EPO improved by 9.3% and 70.0% for the tensile strength and elongation at break, respectively. The plasticized PLA/DSF biocomposite also showed improvement in impact properties by 37.0%. The SEM micrographs of plasticized PLA/DSF biocomposite revealed no gap between fiber and matrix suggesting good interfacial adhesion between DSF and PLA. In can be concluded that PLA/DSF biocomposite is suitable to be used for disposable food container material

Physical and functional properties of durian skin fiber biocomposite films filled with natural antimicrobial agents

Effects of durian skin fiber (DSF), epoxidized palm oil (EPO), and cinnamon essential oil (CEO) on the physical and functional properties of polylactic acid (PLA) biocomposite films were investigated. The biocomposite films were produced via a solution casting process. The results indicated that the PLA with 3 wt.% DSF absorbed the maximum amount of water (5.9%), which was due to the hydrophilic characteristics of the DSF. Additionally, PLA and DSF lost the most weight after decomposing for 50 days in soil. The dart drop impact test showed a reduction in the impact failure weight of the PLA composites with EPO and CEO, which could have been because of their porosity; hence, a porosity was created between the microstructures. Interestingly, the tear resistance was remarkably amplified for the biocomposites with EPO and CEO. From the migration study, the PLA, DSF, EPO, and CEO biocomposite film appeared to be suitable for use as food packaging for all types of food, as there were no negative effects when they were tested with aqueous, alcoholic, acidic, fatty, and milk food product types

Potential of fabrication of durian skin fiber biocomposites for food packaging application through the electricity impact analysis

As an effort to replace the petroleum-based polymers and reduce waste-related environmental problems, biopolymers are the best candidate due to their renewable, biodegradable and commercially viable. Initiative have been taken by developing durian skin fibre (DSF) reinforced polylactic acid (PLA) biocomposites with the addition of epoxidized palm oil (EPO). PLA/DSF biocomposites were fabricated via extrusion and then injection moulded. The biocomposites were assessed for its life cycle by developing a system boundary related to its fabrication processes using GaBi software. The life cycle assessment (LCA) of PLA/DSF biocomposites show that global warming potential (GWP) and acidification potential (AP) were the major impacts from PLA/DSF biocomposite. For PLA/DSF biocomposite, the results were 199.37 kg CO2 equiv. GWP and 0.58 kg SO2 equiv. AP. Meanwhile, for PLA/DSF/EPO biocomposite, the results obtained were 195.89 kg CO2 equiv. GWP and 0.57 kg SO2 equiv. AP. The GWP and AP were contributed by the electricity used in the fabrication of biocomposites. These impacts were due to the usage of electricity, which contributed to the emission of CO2. However, the PLA/DSF/EPO biocomposite had lower negative impacts because EPO improved the workability and processability of the biocomposite, and hence, reduced the amount of energy required for production. It can be concluded that the plasticized PLA/DSF biocomposite can be a potential biodegradable food packaging material as it has favourable properties and produces no waste

The effects of supercritical carbon dioxide on the degradation and antimicrobial properties of PLA biocomposite

Biopolymer products that is biodegradable presently attracting an attention from researchers and industry. The biodegradable packaging based on polylactic acid (PLA), durian skin fibre (DSF), epoxidized palm oil (EPO) and incorporated with cinnamon essential oil (CEO) as antimicrobial agent have been developed and showed to be a promising field of research. This paper reported the effects of supercritical carbon dioxide on the degradation and antimicrobial properties of PLA biocomposite films produced via solvent casting. The biocomposites underwent supercritical carbon dioxide (SCCO2) treatment at two different conditions under 40 °C temperature and at 100 bar and 200 bar pressure. Water absorption test showed that the untreated PLA biocomposite absorbed most water as compared to treated PLA biocomposite with SCCO2 at 5.1%. This is due to the hydrophilic nature of the fibre that absorbed water molecules. Soil burial test showed that the treated PLA biocomposite possessed the highest value of weight losses after 80 days with 97.8%. Biocomposite with the presence of CEO demonstrated antimicrobial activity against both gram-positive and gram-negative bacteria. This showed that SCCO2 significantly improved the properties of PLA biocomposite films. The supercritical fluid treatment of PLA biocomposite could be an alternative for active packaging industries to ensure that the packaging product meets the requirement by consumers as well as being an eco-friendly product

Transplanted erythropoietin-expressing mesenchymal stem cells promote pro-survival gene expression and protect photoreceptors from sodium iodate-induced cytotoxicity in a retinal degeneration model

Mesenchymal stem cells (MSC) are highly regarded as a potential treatment for retinal degenerative disorders like retinitis pigmentosa and age-related macular degeneration. However, donor cell heterogeneity and inconsistent protocols for transplantation have led to varied outcomes in clinical trials. We previously showed that genetically-modifying MSCs to express erythropoietin (MSCEPO) improved its regenerative capabilities in vitro. Hence, in this study, we sought to prove its potential in vivo by transplanting MSCsEPO in a rat retinal degeneration model and analyzing its retinal transcriptome using RNA-Seq. Firstly, MSCsEPO were cultured and expanded before being intravitreally transplanted into the sodium iodate-induced model. After the procedure, electroretinography (ERG) was performed bi-weekly for 30 days. Histological analyses were performed after the ERG assessment. The retina was then harvested for RNA extraction. After mRNA-enrichment and library preparation, paired-end RNA-Seq was performed. Salmon and DESeq2 were used to process the output files. The generated dataset was then analyzed using over-representation (ORA), functional enrichment (GSEA), and pathway topology analysis tools (SPIA) to identify enrichment of key pathways in the experimental groups. The results showed that the MSCEPO-treated group had detectable ERG waves (P <0.05), which were indicative of successful phototransduction. The stem cells were also successfully detected by immunohistochemistry 30 days after intravitreal transplantation. An initial over-representation analysis revealed a snapshot of immune-related pathways in all the groups but was mainly overexpressed in the MSC group. A subsequent GSEA and SPIA analysis later revealed enrichment in a large number of biological processes including phototransduction, regeneration, and cell death (Padj <0.05). Based on these pathways, a set of pro-survival gene expressions were extracted and tabulated. This study provided an in-depth transcriptomic analysis on the MSCEPO-treated retinal degeneration model as well as a profile of pro-survival genes that can be used as candidates for further genetic enhancement studies on stem cells

Retinal degeneration rat model: a study on the structural and functional changes in the retina following injection of sodium iodate

Retinal disorders account for a large proportion of ocular disorders that can lead to visual impairment or blindness, and yet our limited knowledge in the pathogenesis and choice of appropriate animal models for new treatment modalities may contribute to ineffective therapies. Although genetic in vivo models are favored, the variable expressivity and penetrance of these heterogeneous disorders can cause difficulties in assessing potential treatments against retinal degeneration. Hence, an attractive alternative is to develop a chemically-induced model that is both cost-friendly and standardizable. Sodium iodate is an oxidative chemical that is used to simulate late stage retinitis pigmentosa and age-related macular degeneration. In this study, retinal degeneration was induced through systemic administration of sodium iodate (NaIO3) at varying doses up to 80 mg/kg in Sprague-Dawley rats. An analysis on the visual response of the rats by electroretinography (ERG) showed a decrease in photoreceptor function with NaIO3 administration at a dose of 40 mg/kg or greater. The results correlated with the TUNEL assay, which revealed signs of DNA damage throughout the retina. Histomorphological analysis also revealed extensive structural lesions throughout the outer retina and parts of the inner retina. Our results provided a detailed view of NaIO3-induced retinal degeneration, and showed that the administration of 40 mg/kg NaIO3 was sufficient to generate disturbances in retinal function. The pathological findings in this model reveal a degenerating retina, and can be further utilized to develop effective therapies for RPE, photoreceptor, and bipolar cell regeneration

Dental pulp stem cells therapy overcome photoreceptor cell death and protects the retina in a rat model of sodium iodate-induced retinal degeneration

Blindness and vision loss contribute to irreversible retinal degeneration, and cellular therapy for retinal cell replacement has the potential to treat individuals who have lost light sensitive photoreceptors in the retina. Retinal cells are well characterized in function, and are a subject of interest in cellular replacement therapy of photoreceptors and the retinal pigment epithelium. However, retinal cell transplantation is limited by various factors, including the choice of potential stem cell source that can show variability in plasticity as well as host tissue integration. Dental pulp is one such source that contains an abundance of stem cells. In this study we used dental pulp-derived mesenchymal stem cells (DPSCs) to mitigate sodium iodate (NaIO3) insult in a rat model of retinal degeneration. Sprague-Dawley rats were first given an intravitreal injection of 3 × 105 DPSCs as well as a single systemic administration of NaIO3 (40 mg/kg). Electroretinography (ERG) was performed for the next two months and was followed-up by histological analysis. The ERG recordings showed protection of DPSC-treated retinas within 4 weeks, which was statistically significant (* P ≤ .05) compared to the control. Retinal thickness of the control was also found to be thinner (*** P ≤ .001). The DPSCs were found integrated in the photoreceptor layer through immunohistochemical staining. Our findings showed that DPSCs have the potential to moderate retinal degeneration. In conclusion, DPSCs are a potential source of stem cells in the field of eye stem cell therapy due to its protective effects against retinal degeneration