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Power Capability Boundaries for an Inverter Providing Multiple Grid Support Services
Get PDFIt is getting more common every day to install inverters that o er several grid support services in parallel. As these services are provided, a simultaneous need arises to know the combined limit of the inverter for those services. In the present paper, operational limits are addressed based on a utility scale for a real inverter scenario with an energy storage system (ESS) (1.5 MW). The paper begins by explaining how active and reactive power limits are calculated, illustrating the PQ maps depending on the converter rated current and voltage. Then, the ellect of the negative sequence injection, the phase shift of compensated harmonics and the transformer de-rating are introduced step-by-step. Finally, inverter limits for active filter applications are summarized, to finally estimate active and reactive power limits along with the harmonic current injection for some example cases.
The results show that while the phase shift of the injected negative sequence has a significant ellect in the available inverter current, this is not the case for the phase shift of injected harmonics. However, the amplitude of the injected negative sequence and harmonics will directly impact the power capabilities of the inverter and therefore, depending on the grid-side voltage, it might be interesting to design an output transformer with a different de-rating factor to increase the power capabilities
Surface drag analysis after Ti-6Al-4V orthogonal cutting using grid distortion
Get PDFSurface integrity directly affects the mechanical behavior of the workpiece, which is especially relevant on fatigue behavior. To characterize the quality of the machined surface, aspects such as material damage, roughness or residual stress are considered. Measurement of the material damage of the surface is characterized in some cases as surface drag, depth of the affected machining zone, a phenomenon which takes place due to plastic strain in the surface layer caused by machining stress which could have an influence on residual stress. Surface drag measurement done with optical microscopes has relevant uncertainty. In this paper, a methodology to measure the surface drag with lower uncertainty is proposed. The method consists of measuring the deformation of a grid as a result of the machining process. The grid was created with micromilling. The method was applied to analyze the effect of feed on the surface integrity after orthogonal cutting of Ti-6Al-4V. The depth of the affected layer was measured using a 3D optical measuring device (Alicona Infinite Focus IFG4) and compared with numerical simulations and a good agreement was achieved. In comparison with optical microscope results, it can be concluded that traditional method underestimates surface drag
How to Quantify the Security Level of Embedded Systems? A Taxonomy of Security Metrics
Get PDFEmbedded Systems (ES) development has been historically focused on functionality rather than security, and today it still applies in many sectors and applications. However, there is an increasing number of security threats over ES, and a successful attack could have economical, physical or even human consequences, since many of them are used to control critical applications. A standardized and general accepted security testing framework is needed to provide guidance, common reporting forms and the possibility to compare the results along the time. This can be achieved by introducing security metrics into the evaluation or assessment process. If carefully designed and chosen, metrics could provide a quantitative, repeatable and reproducible value that would reflect the level of security protection of the ES. This paper analyzes the features that a good security metric should exhibit, introduces a taxonomy for classifying them, and finally, it carries out a literature survey on security metrics for the security evaluation of ES. In this review, more than 500 metrics were collected and analyzed. Then, they were reduced to 169 metrics that have the potential to be applied to ES security evaluation. As expected, the 77.5% of them is related exclusively to software, and only the 0.6% of them addresses exclusively hardware security. This work aims to lay the foundations for constructing a security evaluation methodology that uses metrics so as to quantify the security level of an ES
A novel indirect cryogenic cooling system for improving surface finish and reducing cutting forces when turning ASTM F-1537 cobalt-chromium alloys
Get PDFThis paper presents a novel indirect cryogenic cooling system, employing liquid nitrogen (LN2) as a coolant for machining the difficult-to-cut ASTM F-1537 cobalt-chromium (CoCr) alloy. The prototype differs from the already existing indirect cooling systems by using a modified cutting insert that allows a larger volume of cryogenic fluid to flow under the cutting zone. For designing the prototype analytical and finite element, thermal calculations were performed; this enabled to optimize the heat evacuation of the tool from the rake face without altering the stress distribution on the insert when cutting material. Turning experiments on ASTM F-1537 CoCr alloys were performed under different cutting conditions and employing indirect cryogenic cooling and dry machining, to test the performance of the developed system. The results showed that the new system improved surface roughness by 12%, and cutting forces were also reduced by 12% when compared with the existing indirect cryogenic cooling technique
Experimental and Numerical Simulation Investigation on Deep Drawing Process of Inconel 718 with and without Intermediate Annealing Thermal Treatments
Get PDFThe aeronautical industry is moving from high-capacity large-airplane construction to low-capacity small-airplane construction. With the change in the production volume, there is a need for more e cient manufacturing processes, such as stamping/deep drawing. However, the streamlined shape and exotic materials of airplanes pose a challenge to accurate numerical simulation of the manufacturing processes. In the case of the Inconel 718 material, researchers previously proposed numerical models; however, these models failed to take account of some key parameters, such as the degradation of the elastic modulus and intermediate annealing thermal processes. The aim of the present study was to characterize the Inconel 718 material, with and without intermediate annealing thermal treatment (TT) and to propose a suitable model. To evaluate the accuracy of the proposed model, a U-drawing benchmark test was used
Cuerpos inclinados que imaginan
Get PDFEste texto pone en relación la trayectoria del coreógrafo Steve Paxton con
aspectos concretos del pensamiento de Adriana Cavarero y Donna Haraway.
Paxton ha investigado durante décadas el cuerpo humano, a través del
caminar, del estudio de la gravedad y de la realización del compost
orgánico. A partir del concepto de inclinación desarrollado por Adriana
Cavarero, en el que el yo al inclinarse se desestabiliza y se relaciona desde
la vulnerabilidad, argumentaré que esta toma de consciencia permite reexperienciar nuestra relación con el cuerpo —y, por tanto, con el mundo—.
Inclinarse, sentir la gravedad, imaginar, abren otras percepciones.
Conforman una sensibilidad desde la que, al igual que en la elaboración del
compost orgánico, sus microorganismos y microespecies, es posible afectar
a una estructura mayor. Haraway afirma que somos compost, lo que nos
lleva a situarnos más cerca de la tierra y a pensarnos como seres humanos,
seres humus: espacios en los que los y las demás pueden crecer
Sensitivity analysis of the input parameters of a physical based ductile failure model of Ti-6Al-4V for the prediction of surface integrity
Get PDFIn machining of Ti-6Al-4V, it is commonly reported the appearance of segmented chip produced by adiabatic shearing (at high cutting speeds) and lack of ductility (at low cutting speeds). Moreover, machining is a manufacturing process that is based on applying external energy to the workpiece to produce a separation of a material layer. Thus, to analyze the physics involved in the new surface generation and in the chip segmentation process, it is necessary to apply ductile failure models. However, the characterization of fracture models in machining conditions (temperature, strain rate, stress triaxiality, Lode angle etc.) is an arduous task. Therefore, to define a ductile failure model applicable to machining it is almost inevitable to apply inverse simulations strategies to obtain reliable results in the not tested conditions. Nevertheless, there is few information about the influence of the input parameters of ductile failure model in fundamental outputs and even less in surface integrity aspects. The aim of this research was to conduct a sensitivity analysis of the influence of the input parameters of a physical based ductile failure model not only in fundamental variables (forces, temperatures and chip morphology) but also on surface integrity (surface drag). To this end, a subroutine was developed for the ductile failure model and it was implemented in the Finite Element Method (FEM) software AdvantEdge. Subsequently, using a statistical software and the Design of Experiments (DOE) technique the influence of the input parameters of the failure model on the outputs was analyzed
ADAPT: an Automatic Diagnosis of Activity and Processes in auTomation environments
Get PDFIn an automated industrial environment, a large volume of data and signals is available, both from sensors and actuators in machinery and from the interaction with operators and users. Operation diagnosis can have multiple applications from a learning point of view (e.g. staff training) or in terms of process assessment. This work proposes a methodology for implementing an Intelligent System by means of any interactive system connected through OPC UA standard. A digital twin of the process supports configuration and validation, prior to commissioning. Activity is interpreted and diagnosed according to the context in which it occurs. Step order in sequence, step duration and sequence duration are analyzed in a use case based on a PLC-controlled robotic cell in which it is operated both in automatic and manual mode for adjusting a linear table’s positioning
Conceptual framework for process-oriented feedback through Learning Analytics Dashboards
Get PDFThe number of students enrolled in online higher education courses is
increasing, and as a result, more data on their learning process is being generated.
By exploring this student behavior data through learning analytics, both student
and teacher can be provided with process-oriented feedback in the form of
dashboards. However, little is known about the typology of relevant feedback in
the dashboard to different learning objectives, students and teachers. Although
most dashboards and the feedback they provide are based solely on student
performance indicators, research shows that such feedback is not sufficient. This
article attempts to define a conceptual model that visualizes the relationships
between the design of a Learning Analytics Dashboard (LAD) and the concepts
of learning science in order to provide process-oriented feedback that supports
the regulation of learning. The aim of the work is not to propose a specific design
of the LAD to provide feedback, but rather a conceptual framework for the choice
of concepts for that design, and therefore to help understand future data needs as
a basis for the educational feedback of the dashboards. As a conclusion of our
research, we can say that having LADs adapted to any profile (student, teacher,
etc.) can improve decision-making processes by showing each user the
information that interests them most in the way that best enables them to
understand it