Modelling Approaches for Triple Three-Phase Permanent Magnet Machines

Standard modelling approaches for a triple three-phase (i.e. nine-phase) machine include vector space decomposition (VSD) and triple d-q modelling procedure. Each is characterised with certain benefits and shortcomings. This paper introduces a novel transformation, applicable to multiple three-phase winding machines in general, especially aimed at facilitating the power (current) sharing between the three-phase systems. The easiness of the current sharing with the novel transformation, introduced here, is demonstrated via simulations in MATLAB

A Novel Synthetic Loading Method for Multiple Three-phase Winding Electric Machines

The paper develops a version of the synthetic loading method, suitable for testing of multiphase machines with multiple three-phase distributed windings. The method is at first discussed in general terms for a structure with k three-phase stator windings (i.e. total number of phases is n = 3k). Subsequent detailed development is described for a dual three-phase (six-phase) stator winding configuration. With a control architecture that allows the use of half of the three-phase windings as a motor and the other half as a generator, the machine (and/or the converter) can be tested under full rated power without the need for any mechanical load. Moreover, the power consumed from the grid is in essence equal only to the total losses of the system. Modelling, based on the double d-q approach, and the control layout that includes full cross-coupling decoupling are described for a permanent magnet (PM) synchronous machine. An experimental test rig with a double three-phase PM machine of 150 kW rating is detailed and the samples of experimental results are provided to verity the theoretical considerations

Modelling Approaches for an Asymmetrical Six-Phase Machine

With currently available power electronic devices, the power range of a single three-phase power converter is limited well below the power ratings foreseen for remote offshore wind turbines. A solution is to use multiphase systems. By connecting each of the converters to one three-phase winding in the stator of the machine, a multiphase conversion system is obtained allowing to exploit its fault tolerance. In multiphase machines, the basic idea of the model transformations is the same as in the three-phase case, but, due to the increase in the dimension of the system, it introduces additional degrees of freedom. This work at first compares the two widely used modelling approaches regarding physical interpretation of the subspaces, harmonic mapping and representation of asymmetries applied to an asymmetrical six-phase machine. It further introduces an alternative transformation that is aimed at situations where power sharing between three-phase windings is desired and characterises its behaviour using the same figures of merit as for the existing transformations

Modelling Approaches for Triple Three-Phase Permanent Magnet Machines

Standard modelling approaches for a triple three-phase (i.e. nine-phase) machine include vector space decomposition (VSD) and triple d-q modelling procedure. Each is characterised with certain benefits and shortcomings. This paper introduces a novel transformation, applicable to multiple three-phase winding machines in general, especially aimed at facilitating the power (current) sharing between the three-phase systems. The easiness of the current sharing with the novel transformation, introduced here, is demonstrated via simulations in MATLAB

Sound absorbing and insulating low-cost panels from end-of-life household materials for the development of vulnerable contexts in circular economy perspective

From a construction point of view, neighborhoods with residents living at or below the poverty threshold are characterized by low energy efficiency buildings, in which people live in acoustic discomfort with no viable options for home improvements, as they usually can not afford the materials and labor costs associated. An alternative to this is to use low-cost insulating elements made of non-conventional materials with acceptable acoustic properties. Given that household materials at their end-of-life (EoLHM) are free of costs and available also to the more disadvantaged population, they can be used to build acoustic panels for such contexts. This approach embraces several benefits since it reduces the amount of waste produced, the footprint deriving from the extraction of new raw materials and, by highlighting the potential of the EoLHM, discourages the abandonment of waste. In this paper, the acoustic properties of EoLHM, such as cardboard, egg-cartons, clothes, metal elements and combinations of them, are investigated by means of the impedance tube technique. The measured sound absorption coefficient and transmission loss have shown that EoLHM can be used for the realization of acoustic panels. However, since none of the analyzed materials shows absorbing and insulating properties at the same time, EoLHM must be wisely selected. This innovative approach supports the circular economy and the improvement for the living condition of low-income households

LCL Grid Filter Design of a Multimegawatt Medium-Voltage Converter for Offshore Wind Turbine Using SHEPWM Modulation

The switching frequency of medium-voltage highpower converters is limited to about 1 kHz due to semiconductor junction temperature constraint. The frequency band between the fundamental and carrier frequency is limited to a little more than one decade and the LCL filter design is usually a challenge to meet grid codes for grid-connected applications. Traditional designs focus on the optimization of the filter parameters and different damping circuits. However, this design is very influenced by the modulation technique and produced low-order harmonics. Widely used pulse width modulations (PWM), such as phase disposition PWM (PDPWM), produce low-order harmonics that constraint the design of the filter. Selective harmonic elimination PWM (SHEPWM) can eliminate theses low-order harmonics, enabling a more efficient design of the LCL filter. In this paper, the LCL grid filter of a multimegawatt medium-voltage neutral-point-clamped converter for a wind turbine is redesigned using the SHEPWM modulation. Experimental results demonstrate that the efficiency of the converter, filter, and overall efficiency are increased compared to that obtained with PDPWM

Insensibilizador de baixo custo para abate de frangos coloniais.

bitstream/item/31428/1/comunicado-204.pd

Estudio de sensibilidad de parámetros de modelos en flujos cavitantes en régimen no estacionario

La cavitación es un complejo fenómeno físico que se presenta generalmente en flujos turbulentos afectado por varios factores, como la presión del sistema y la concentración de gases no condensables disueltos. Para analizar este comportamiento se han desarrollado modelos matemáticos, algunos de los cuales se encuentran dentro de software de simulaciones comerciales. Para ser aplicados, junto con modelos de turbulencia, deben fijarse cierto número de parámetros de calibración que han sido establecidos sólo para un número reducido de tipos de flujo (geometrías simples, variables del fluido típicas, flujo no desprendido, etc.). Cuando empieza a aparecer el flujo reverso, incluso en geometrías simples, la capacidad de predecir correctamente el fenómeno de cavitación es menor y se cree que un estudio cuidadoso de sensibilidad de parámetros es útil a la hora de realizar aplicaciones de simulación a casos industriales. Este trabajo amplía resultados ya obtenidos anteriormente, estudiando en detalle los modelos de mejor comportamiento ya seleccionados, producto de la experiencia adquirida. Se busca ahora identificar la mejor combinación de parámetros a través de la comparación de resultados experimentales de flujos cavitantes, de características fuertemente no estacionarias, de típica aparición en turbomáquinas hidráulicas (TMH), extendiendo los trabajos de calibración ya realizados anteriormente. Se ha seguido utilizando geometrías simples (tipo Venturi) con el objeto de centrarse en los modelos de turbulencia y cavitación ya probados para casos estacionarios y por tener una abundante información experimental de flujos cavitantes en estas geometrías. Los trabajos de validación/calibración se llevaron a cabo comparando perfiles de velocidad del fluido, la presión en la zona cavitante y la frecuencia del ciclo de crecimiento y decrecimiento de la cavidad, entre otras variables, ajustando los coeficientes de producción/disipación de energía turbulenta y algunos parámetros típicos del modelo de flujo cavitante los que pueden influir en la exactitud y estabilidad de las predicciones numéricas.Postprint (published version

Generation of two transgene-free human iPSC lines from CD133+ cord blood cells

We have generated two human induced pluripotent stem cell (iPSC) lines from CD133+ cells isolated from umbilical cord blood (CB) of a female child using non-integrative Sendai virus. Here we describe the complete characterization of these iPSC lines: PRYDi-CB5 and PRYDi-CB40

Land cover effects on hydrologic services under a precipitation gradient

Climate change impacts on the hydrological cycle are altering the quantity, quality, and temporal distribution of riverine discharge, necessitating a more rigorous consideration of changes in land cover and land use. This study establishes relationships between different land cover combinations (e.g. percentages of forest – both native and exotic – and pastureland) and hydrological services, using hydrological indices estimated at annual and seasonal timescales in an area with a steep precipitation gradient (900–2600&thinsp;mm&thinsp;yr−1). Using discharge data from 20 catchments in the Bay of Biscay, a climate transition zone, the study applied multiple regression models to better understand how the interaction between precipitation and land cover combinations influence hydrological services. Findings showed the relationship between land cover combinations and hydrological services is highly dependent on the amount of precipitation, even in a climatically homogeneous and relatively small area. In general, in the Bay of Biscay area, the greater presence of any type of forests is associated with lower annual water resources, especially with greater percentages of exotic plantations and high annual precipitation. Where precipitation is low, forests show more potential to reduce annual and winter high flows than pasturelands, but this potential decreases as annual or seasonal precipitation increases. As annual precipitation increases, low flows increase as the percentage of exotic plantations decreases and pasturelands increase. Results obtained in this study improve understanding of the multiple effects of land cover on hydrological services, and illustrate the relevance of land planning to the management of water resources, especially under a climate change scenario.</p