Investigation of efficient multilevel inverter for photovoltaic energy system and electric vehicle applications

Introduction. This research presents a simple single-phase pulse-width modulated 7-level inverter topology for renewable system which allows home-grid applications with electric vehicle charging. Although multilevel inverters have appealing qualities, their vast range of application is limited by the use of more switches in the traditional arrangement. As a result, a novel symmetrical 7-level inverter is proposed, which has the fewest number of unidirectional switches with gate circuits, providing the lowest switching losses, conduction losses, total harmonic distortion and higher efficiency than conventional topology. The novelty of the proposed work consists of a novel modular inverter structure for photovoltaic energy system and electric vehicle applications with fewer numbers of switches and compact in size. Purpose. The proposed system aims to reduce switch count, overall harmonic distortions, and power loss. There are no passive filters required, and the constituted optimizes power quality by producing distortion-free sinusoidal output voltage as the level count increases while reducing power losses. Methods. The proposed topology is implemented with MATLAB/Simulink, using gating pulses and various pulse-width modulation methodologies. Moreover, the proposed model also has been validated and compared to the hardware system. Results. Total harmonic distortion, number of power switches, output voltage, current, power losses and number of DC sources are investigated with conventional topology. Practical value. The proposed topology has proven to be extremely beneficial for implementing photovoltaic-based stand-alone multilevel inverter and electric vehicle charging applications.Вступ. У цьому дослідженні представлена топологія простого семирівневого однофазного інвертора з широтно-імпульсною модуляцією для системи з відновлюваними джерелами енергії, яка дозволяє використовувати домашню мережу з зарядкою електромобілів. Хоча багаторівневі інвертори мають привабливі характеристики, широкий спектр їх застосування обмежений використанням більшої кількості перемикачів у традиційній схемі. В результаті запропонований новий симетричний 7-рівневий інвертор, який має найменшу кількість односпрямованих ключів із затворними ланцюгами, забезпечує найменші комутаційні втрати, втрати на провідність, сумарні гармонічні спотворення та вищий ККД, ніж традиційна топологія. Новизна запропонованої роботи полягає у новій модульній структурі інвертора для фотоелектричних енергетичних систем та використання для електромобілів з меншою кількістю перемикачів та компактними розмірами. Мета. Пропонована система спрямована на зменшення кількості перемикань, загальних гармонічних спотворень та втрат потужності. Пасивні фільтри не потрібні, а складова частина оптимізує якість електроенергії, створюючи синусоїдальну вихідну напругу без спотворень зі збільшенням кількості рівнів при одночасному зниженні втрат потужності. Методи. Запропонована топологія реалізована за допомогою MATLAB/Simulink з використанням стробуючих імпульсів та різних методологій широтно-імпульсної модуляції. Крім того, запропонована модель також була перевірена та порівняна з апаратною системою. Результати. Загальні гармонічні спотворення, кількість силових ключів, вихідна напруга, струм, втрати потужності та кількість джерел постійного струму досліджуються за допомогою традиційної топології. Практична цінність. Запропонована топологія виявилася надзвичайно корисною для реалізації автономних багаторівневих інверторів на основі фотоелектричних систем та застосування для заряджання електромобілів

Modeling a Coronal Mass Ejection as a Magnetized Structure with EUHFORIA

We studied an Earth-directed coronal mass ejection (CME) that erupted on 2015 March 15. Our aim was to model the CME flux rope as a magnetized structure using the European Heliospheric Forecasting Information Asset (EUHFORIA). The flux rope from eruption data (FRED) output was applied to the EUHFORIA spheromak CME model. In addition to the geometrical properties of the CME flux rope, we needed to input the parameters that determine the CME internal magnetic field like the helicity, tilt angle, and toroidal flux of the CME flux rope. According to the FRED technique geometrical properties of the CME flux rope are obtained by applying a graduated cylindrical shell fitting of the CME flux rope on the coronagraph images. The poloidal field magnetic properties can be estimated from the reconnection flux in the source region utilizing the post-eruption arcade method, which uses the Heliospheric Magnetic Imager magnetogram together with the Atmospheric Imaging Assembly (AIA) 193 angstrom images. We set up two EUHFORIA runs with RUN-1 using the toroidal flux obtained from the FRED technique and RUN-2 using the toroidal flux that was measured from the core dimming regions identified from the AIA 211 angstrom images. We found that the EUHFORIA simulation outputs from RUN-1 and RUN-2 are comparable to each other. Overall using the EUHFORIA spheromak model, we successfully obtained the magnetic field rotation of the flux rope, while the arrival time near Earth and the strength of the interplanetary CME magnetic field at Earth are not as accurately modeled.Peer reviewe

Theoretical Analysis of Stresses in a Lithium Ion Cell

A mathematical model to simulate the generation of mechanical stress during the discharge process in a dual porous insertion electrode cell sandwich comprised of lithium cobalt oxide and carbon is presented. The model attributes stress buildup within intercalation electrodes to two different aspects: changes in the lattice volume due to intercalation and phase transformation during the charge/discharge process. The model is used to predict the influence of cell design parameters such as thickness, porosity, and particle size of the electrodes on the magnitude of stress generation. The model developed in this study can be used to understand the mechanical degradation in a porous electrode during an intercalation/deintercalation process, and the use of this model results in an improved design for battery electrodes that are mechanically durable over an extended period of operation

Multiple Recurrent De Novo CNVs, Including Duplications of the 7q11.23 Williams Syndrome Region, Are Strongly Associated with Autism

SummaryWe have undertaken a genome-wide analysis of rare copy-number variation (CNV) in 1124 autism spectrum disorder (ASD) families, each comprised of a single proband, unaffected parents, and, in most kindreds, an unaffected sibling. We find significant association of ASD with de novo duplications of 7q11.23, where the reciprocal deletion causes Williams-Beuren syndrome, characterized by a highly social personality. We identify rare recurrent de novo CNVs at five additional regions, including 16p13.2 (encompassing genes USP7 and C16orf72) and Cadherin 13, and implement a rigorous approach to evaluating the statistical significance of these observations. Overall, large de novo CNVs, particularly those encompassing multiple genes, confer substantial risks (OR = 5.6; CI = 2.6–12.0, p = 2.4 × 10-7). We estimate there are 130–234 ASD-related CNV regions in the human genome and present compelling evidence, based on cumulative data, for association of rare de novo events at 7q11.23, 15q11.2-13.1, 16p11.2, and Neurexin 1

Co-cultured Mesenchymal Stem Cell Differentiation on 3D Printed Scaffolds for Bone Tissue Engineering

Mesenchymal stem cells (MSCs) have a great potential in the field of tissue engineering and regenerative medicine due to their ability to self-renew and differentiate into various lineages. They can be differentiated by chemical factors, mechanical stimulus, and electrical potential among others. However, one of the strategies to enhance osteogenic differentiation of MSCs is to co-culture them with endothelial cells (ECs) exploiting their cell-cell interactions. In addition to differentiating into osteogenic, adipogenic and chondrogenic lineages, MSCs can differentiate into endothelial phenotype in vivo behavior can be reflected more accurately by a three-dimensional (3D) scaffold environment than a two-dimensional (2D) planar surface. Hence, 3D bioprinting can be used to provide a new opportunity for stem cell distribution, positioning, and differentiation at the microscale to make the differentiated architecture of any tissue while maintaining precision and control over the cellular microenvironment

Regional Differentiation of Adipose-Derived Stem Cells Proves the Role of Constant Electric Potential in Enhancing Bone Healing

Mesenchymal stem cells (MSCs) have a great potential in the field of tissue engineering and regenerative medicine on account of their ability to self-renew and differentiate into various lineages. MSCs could be differentiated by a number of ways. Electric field is known to bring about differentiation, migration, proliferation, and reorientation of MSCs. Hence, we aim to create a bioreactor to attain osteodifferentiation of human-derived MSCs in the presence of osteoinduction medium (OIM) in combination with or without alternating current (AC) fields. A stimulation bioreactor was specially designed for the exposure of adipose-derived stem cells (ASCs) to an electric field of 20 mV/cm, 60 kHz. The electric field potential (E) within the chamber was simulated using COMSOL. The morphology, proliferation, and osteogenic differentiation of ASCs under the influence of electrical stimulation were studied. By week three, electrically stimulated ASCs exhibited their typical spindle-shaped morphology. Stimulated ASCs were more intensely stained with alkaline phosphatase and alizarin red, the markers of osteogenic differentiation, as compared to the unstimulated control groups. Darker stained regions correlated with the COMSOL simulation which showed constant electric potential at the same place. The results depicted a clear difference between the effect of constant and varying electric potential on osteodifferentiation of ASCs. Picogreen assay revealed lower DNA contents of electrically stimulated ASCs compared to the control group. In this study, we have additively enhanced the osteodifferentiation potential of ASCs by electrical stimulation and have proved that it is constant electric field potential which specifically augments osteogenic differentiation. We have successfully developed a bioreactor to improve the osteodifferentiation of ASCs by an electrical field, which could be applied in regenerative therapy strategies of bone fracture treatment

Effect of Patterned Electrospun Hierarchical Structures on Alignment and Differentiation of Mesenchymal Stem Cells: Biomimicking Bone

Considering the complex hierarchical structure of bone, biomimicking the micro and nano level features should be an integral part of scaffold fabrication for successful bone regeneration. We aim to biomimic the micro- and nano-structure of bone and study the effect of physical cues on cell alignment, proliferation and differentiation. To achieve this, we have divided the scaffolds into groups: electrospun SU-8 nanofibers, electrospun SU-8 nanofibers with UV treatment and micropatterned (20 μm sized ridges and grooves) SU-8 nanofibers by photolithography with UV treatment. Two types of culture conditions were applied: with and without osteoinduction medium. In-vitro cell proliferation assays, protein estimation, ALP osteodifferentiation assay, live dead assay and cell alignment studies were performed on these micro-patterned nanofiber domains. Our findings show that patterned surface induced an early osteodifferentiation of MSCs even in absence of osteoinduction medium. An interesting similarity with the helicoidal plywood model of the bone was observed. The cells showed layering and rotation along the patterns with time. This resembles the in-vivo anisotropic multi-lamellar bone tissue architecture thus, closely mimicking the sub-cellular features of bone. This might serve as a smart biomaterial surface for MSC differentiation in therapeutics where the addition of external chemical factors is a challenge