Assessment and exploitation of the minimum current harmonic distortion under overmodulation in five-phase induction motor drives

This paper compares the most prominent overmodulation (OVM) techniques for five-phase induction motor drives with respect to the minimum current distortion (MCD) achievable. To attain a benchmark of the latter, two MCD OVM approaches are devised. Contrarily to previous strategies aimed at voltage distortion reduction/minimization, these MCD methods are focused on minimizing the harmonic stator copper loss (HSCL), thus minimizing the current total harmonic distortion (THD). One of these MCD strategies minimizes the HSCL while injecting only x–y harmonics. The other MCD method exploits α–β harmonic injection to further decrease the HSCL and to cover the whole OVM region. Moreover, the dual-mode OVM, which is one of the three-phase methods with the lowest distortion, is extended here for five-phase drives. The findings provide insight into how close the OVM methods are to the benchmark imposed by the MCD strategies. Notably, these MCD techniques yield a significant reduction of current THD, HSCL and peak current, especially for machines with negligible thirdorder space harmonic. The average switching losses are also decreased. Indications for real-time implementation of the MCD solutions are also givenAgencia Estatal de Investigación | Ref. PID2019-105612RB-I00Xunta de Galicia | Ref. ED431F 2020/07Xunta de Galicia | Ref. GPC-ED431B 2020/03Agencia Estatal de Investigación | Ref. RYC2018-024407-

DC-current injection with minimum torque ripple in interior permanent-magnet synchronous motors

Several proposals based on dc-current injection have been reported for estimating the stator winding resistance in induction machines, and recently extended for synchronous machines. Tracking this resistance can be very useful, e.g., for thermal monitoring or preserving control dynamics. In surface-mounted permanent-magnet synchronous machines (PMSMs), it is possible to inject a dc component in the d -axis, without perturbing the torque. However, it has been claimed that, for synchronous machines with saliency, it is not possible to avoid the torque ripple due to such injection. This letter proposes optimum reference currents to impose dc current in three-phase interior PMSMs while minimizing to practically zero its associated torque ripple. Namely, the dc signal is injected in combination with a suitable second-order harmonic so that the stator current space vector follows the constant-torque locus, while the fundamental is set according to the maximum-torque-per-ampere strategy. Experimental results validate the theory.Agencia Estatal de Investigación | Ref. DPI2016-75832-

Enhanced resonant current controller for grid-connected converters with LCL filter

Conventional resonant controllers (RCs) are commonly used in the current control of grid-tied converters with LCL filter due to their advantages, such as zero steady-state error at both fundamental sequences, easy design process, and straightforward implementation. Nevertheless, these traditional solutions do not permit to place the closed-loop poles of the system in convenient locations when dealing with a fourth-order plant model such as the LCL filter plus the computation delay. Therefore, the reference tracking and the disturbance rejection are deficient in terms of transient behavior and depend on the LCL filter. Furthermore, an additional active damping method usually has to be designed in order to ensure stability. This paper presents an enhanced current RC with stable and fast response, negligible overshoot, good disturbance rejection, and low controller effort for grid-tied converters with LCL filter. The developed solution uses a direct discrete-time pole-placement strategy from the classical control theory (using transfer functions), involving two extra filters, to enhance the performance of the RC. In this manner, the complexity of state-space methods from modern control theory is avoided. Simulation and experimental results are provided to verify the effectiveness of the proposed control scheme.Ministerio de Ciencia e InnovaciónAgencia Estatal de Investigación | Ref. DPI2016-75832-RMinisterio de Economía y Competitividad | Ref. BES-2013-06314

Generalized multifrequency current controller for grid-connected converters with LCL filter

This paper presents a grid-side current controller for grid-tied inverters with LCL filter, including harmonic current elimination. The proposed controller only measures the grid current and voltage and it combines excellent dynamic characteristics with good robustness. Contrarily to previously proposed harmonic-current controllers, the presented solution offers a generalized method that gives a consistent (with minimal variation in the reference-tracking dynamics) and stable performance irrespectively of the number of current harmonics to be canceled and of the resonant frequency of the LCL filter (provided that it is lower than the Nyquist frequency). The response to reference commands is completely damped and fast. The response speed is set in accordance with the low-pass characteristic of the LCL filter so as to limit the control effort. Concerning the disturbance rejection, the controller offers an infinite impedance to any disturbances (such as grid voltage harmonics) at a set of arbitrarily specified frequencies. This allows the designer to eliminate all the undesired current harmonics with a simple design process. In addition, the performance of the presented controller is evaluated in terms of a fundamental tradeoff that exists between robustness to variations in the grid impedance and the number of frequency components rejected. Finally, simulation and experimental results that validate the proposal are presented.Ministerio de Ciencia e InnovaciónEuropean CommissionAgencia Estatal de Investigación | Ref. DPI2016-75832-RMinisterio de Educación, Cultura y Deporte | Ref. FPU14/0068

Facturación de servicios a terceros.

Este documento, contempla el estudio de caracterización de procesos ejecutados actualmente para la facturación de servicios de terceros en EPM, dentro de dicha caracterización, se contemplan las actividades que deberán ejecutarse para dar inicio por parte de las áreas involucradas, al cumplimiento de requisitos funcionales establecidos a nivel de software, medición de riesgos actuales, y la identificaciones de procesos de facturación que deberán surtirse, con el propósito de parametrizar los cobros ejecutados para los servicios de Aseo, Alumbrado Público Asistencia Domiciliaria y Seguros a través, de una herramienta totalmente habilitada para el cumplimiento del debido proceso en dicha actividad.Corporación Universitaria Minuto de Dios

Eliminating ground current in a transformerless photovoltaic application

For low-power grid-connected applications, a single-phase converter can be used. In photovoltaic (PV) applications, it is possible to remove the transformer in the inverter to reduce losses, costs, and size. Galvanic connection of the grid and the dc sources in transformerless systems can introduce additional ground currents due to the ground parasitic capacitance. These currents increase conducted and radiated electromagnetic emissions, harmonics injected in the utility grid, and losses. Amplitude and spectrum of the ground current depend on the converter topology, the switching strategy, and the resonant circuit formed by the ground capacitance, the converter, the ac filter, and the grid. In this paper, the ground current in a 1.5-kW PV installation is measured under different conditions and used to build a simulation model. The installation includes a string of 16 PV panel, a full-bridge inverter, and an LCL filter. This model allows the study of the influence of the harmonics injected by the inverter on the ground current.Ministerio de Ciencia e Innovación | Ref. DPI2009-0700

Space-vector PWM with common-mode voltage elimination for multiphase drives

Switching common-mode voltage (CMV) generated by the pulse width modulation (PWM) of the inverter causes common-mode currents, which lead to motor bearing failures and electromagnetic interference problems in multiphase drives. Such switching CMV can be reduced by taking advantage of the switching states of multilevel multiphase inverters that produce zero CMV. Specific space-vector PWM (SVPWM) techniques with CMV elimination, which only use zero CMV states, have been proposed for three-level five-phase drives, and for open-end winding five-, six-, and seven-phase drives, but such methods cannot be extended to a higher number of levels or phases. This paper presents a general (for any number of levels and phases) SVPMW with CMV elimination. The proposed technique can be applied to most multilevel topologies, has low computational complexity and is suitable for low-cost hardware implementations. The new algorithm is implemented in a low-cost field-programmable gate array and it is successfully tested in the laboratory using a five-level five-phase motor drive.Ministerio de Ciencia e InnovaciónEuropean CommissionMinisterio de Economía y Competitividad | Ref. DPI2012-31283Ministerio de Economía y Competitividad | Ref. DPI2015-6541

Estudio de las propiedades físicas y químicas de recubrimientos de Tio2 elaborados mediante proyección térmica por combustión oxiacetilénica a partir de polvos nanométricos

RESUMEN: El presente estudio se enfoca en la elaboración de recubrimientos mediante proyección térmica por combustión, a partir de polvos de TiO2 usados como pigmento para aplicaciones cosméticas y pinturas. Los polvos empleados, dadas las aplicaciones para las cuales están desarrollados, poseen características físicas que impiden su uso en proyección térmica, por lo cual se requiere de su funcionalización mediante aglomeración para su posterior proyección. Previo a la elaboración de los recubrimientos se caracterizaron los polvos de TiO2 mediante pruebas de Difracción de Rayos X (DRX), Microscopía Electrónica de Barrido (MEB), Microscopía de Fuerza Atómica (MFA) y difracción láser, encontrando que a pesar de la imposibilidad de usarlo como materia prima en la elaboración de los recubrimientos mediante proyección térmica en las condiciones en las que es comercializado, su aglomeración permite cumplir tal cometido, obteniendo capas finamente estructuradas con un potencial de uso en procesos fotocatalíticos.ABSTRACT: This research is focused on manufacturing of coatings by oxyacetylene thermal spray from TiO2 particles usually used as pigment for cosmetic and paint applications. These powders are not usable in thermal spray processes because the particles’ size distribution exhibits very thin particles that block the torch. In order to manufacture the coatings it was necessary to carry out a functionalization by agglomeration of the particles. Before to the coatings’ manufacturing, the powders were characterized by X-Ray Diffraction, Scan Electron Microscopy, Atomic Force Microscopy and laser diffraction finding out that however the very thin particles the powder can be used in thermal spray processes after an agglomeration processes, getting coatings with bimodal microstructure conferring to the coatings potential applications in photo catalytic process

Annual Conference on Formative Research on EFL. Current trends in language teaching and teacher training.

The conference papers of the Annual Conference on Formative Research on EFL. Current trends in language teaching and teacher training collect pedagogical experiences and research reports on language teaching, teaching practices and communication. Each paper invites the community of the language teaching field to reflect on the development of life skills, didactic competences, critical incidents and practice and the use of English in the communication of organizations. We expect to make visible those innovative experiences and enrich the practice and knowledge of the ELT community