Admittance Model Identification of Inverters using Voltage Injection

The advancements in power electronics are leading to a growing number of electronic converters connected to the electric grid. Even though this enables a more efficient transformation and use of energy, the harmonic interaction between converters can cause instabilities in the network. Therefore, it is important to model the individual converters and their interconnection in an efficient way, in order to study the global stability of the system. A promising modelling strategy analytically derives the equivalent admittance of the converters. However, due to industrial secrecy issues, experimental identification methods are also necessary to obtain the converter equivalent admittance with a black-box approach. This paper analyses the experimental characterization of inverters using the voltage injection method. A detailed explanation of the theoretical background of this method and its practical implementation are provided

Fault-Tolerant Torque Controller Based on Adaptive Decoupled Multi-Stator Modeling for Multi-Three-Phase Induction Motor Drives

Among the multiphase solutions, multi-three-phase drives are becoming more and more widespread in practice as they can be modularly supplied by conventional three-phase inverters. The literature reports several control approaches to perform the torque regulation of multi-three-phase machines. Most of such solutions use the vector space decomposition (VSD) approach since it allows the control of a multi-three-phase machine using the conventional control schemes of three-phase drives, thus reducing the complexity of the control algorithm. However, this advantage is practically lost in the case of open-three-phase faults. Indeed, the postfault operation of the VSD-based drive schemes requires the implementation of additional control modules, often specifically designed for the machine under consideration. Therefore, this article aims to propose a novel control approach that allows using any control scheme developed for three-phase motors to perform the torque regulation of a multi-three-phase machine both in healthy and faulty operation. In this way, the previously mentioned drawbacks of the VSD-based control schemes in dealing with the faulty operation of the machine are avoided. Moreover, the simplicity of the control algorithm is always preserved, regardless of the machine's operating condition. The proposed solution has been experimentally validated through a 12-phase induction motor, rated 10 kW at 6000 r/min, using a quadruple-three-phase configuration of the stator winding

Albumin and fibronectin adsorption on treated titanium surfaces for osseointegration: An advanced investigation

Protein adsorption has a central role in the outcome of implants. However, there is no consensus about the impact of the different surface properties on the material-protein interactions. Here, the adsorption of albumin and fibmnectin in near-physiological concentration is investigated on three differently treated titanium-based surfaces and compared after a thorough characterization. The different titanium surfaces have very different surface properties, in particular regarding roughness, oxide porosity, wettability, surface energy, and zeta potential, which are all known to deeply affect protein adsorption. By merging several characterization techniques, some conventional and some innovative, it was possible to discriminate the effect of surface properties on different aspects of protein adsorption. Despite forming a continuous layer on all samples, the amount of proteins bound to the surface is mainly due to surface roughness and topography, which can overcome the effect of wettability and surface energy. On the other hand, the secondary structure of albumin and fibmnectin and their orientation are determined by the hydroxyl groups exposed on the surfaces, depending on their surface concentration and acidic reactivity in the former, and the surface zeta potential in the latter

Advanced characterization of albumin adsorption on a chemically treated surface for osseointegration: An innovative experimental approach

Surface chemistry, charge, wettability, and roughness affect the adsorbed protein layer, influencing biocompatibility and functionality of implants. Material engineering seeks innovative, sensitive, and reliable characterization techniques for study the adsorbed proteins. These techniques must be suitable to be directly used on the surfaces of clinical interest. In this paper, the characterization of surfaces with topography and chemistry developed for osseointegration is performed by innovative surface analysis techniques to investigate the properties of adsorbed bovine serum albumin. Ti6Al4V alloy chemically treated with an oxidative process to obtain peculiar surface features (roughness and surface hydroxylation) was tested and compared with mirror-polished titanium. Albumin forms a continuous layer on both Ti surfaces when adsorbed from near physiological concentrations, as proved by Kelvin force probe microscopy. It was observed that the hydroxylation degree plays a pivotal role in determining the conformation of proteins after adsorption, where it strongly drives protein unfolding, as confirmed by Surface Enhanced Raman scattering, and in influencing the mechanism and chemical stability of protein-surface interactions, which was highlighted by zeta potential titration curves

Desarrollo de una vacuna inactivada contra la epidermitis exudativa porcina utilizando dos adyuvantes

Staphylococcus hyicus es el agente responsable de provocar la Epidermitis exudativa, una afección de la piel que afecta a los lechones lactantes y destetados menores de 6 semanas de edad. Esta patología se caracteriza por generar lesiones con exudación grasa, descamación y la formación de vesículas. A nivel global presenta una alta incidencia, con una variabilidad en la morbilidad del 20% al 100%, mientras que la mortalidad oscila entre el 50% y el 75%. En Argentina no se dispone actualmente de una vacuna que prevenga esta enfermedad, a pesar de que la inmunización se ha mostrado como una estrategia efectiva en la prevención de los procesos infecciosos en animales. Por lo tanto, el objetivo central de este estudio fue desarrollar dos bacterinas autógenas dirigidas contra Staphylococcus hyicus. Una de estas bacterinas se formuló utilizando un adyuvante convencional (hidróxido de aluminio), mientras que la otra utilizó el adyuvante inmunoestimulante (ISPA). La vacuna se empleó para inmunizar a cerdas preñadas, que fueron agrupadas según el adyuvante utilizado en la inmunización. La evaluación clínica se centró en determinar la tolerancia de las cerdas a las bacterinas. El resultado de esta evaluación fue exitoso, lo que marca un paso importante en la investigación y el desarrollo de medidas preventivas ante la Epidermitis exudativa