Centre of Technology and Systems

Funder

Organizational Unit

Publications

Electric vehicle integrated battery charger for an AC drive with open windings

Publication . Fernão Pires, V.; Cordeiro, Armando; Foito, Daniel; Silva, J. F.

Merging of electric vehicle (EV) charging converter within the EV motor drive allows to minimize the charging system regarding volume, weight, and cost. Thus, several integrated battery charger topologies have been presented for well known drives. However, very few works have been addressed for open windings motor drives. This work is focused on open windings motor drives and battery charger types, proposing a new integrated charger topology. The proposed solution avoids the extra three-phase power factor corrector (PFC) and provides bidirectional power flow, allowing the vehicle batteries to operate also as a grid storage system. Some terminals of the motor open windings are connected to a three-phase inverter supplied by the batteries while the remaining terminals are connected to a three-phase inverter with a floating capacitor. The proposed EV battery charger will be verified and tested by several simulation results.

2021-08-10Conference object

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A DC-DC converter for bipolar DC microgrids with voltage balance capability to supply a multilevel SRM drive

Publication . Fernão Pires, V.; Foito, Daniel; Pires, A. J.; Cordeiro, Armando; Martins, J. F.

In this work it is proposed a DC-DC converter to supply a multilevel Switched Reluctance Machine (SRM) drive. The proposed converter was designed to be integrated in a bipolar DC microgrid. Usually, this kind of microgrid requires a support to avoid unbalances between the poles. Thus, the proposed converter also integrates voltage balance capabilities allowing the required support to the bipolar DC microgrid. Besides that, the converter can also supply the drive using only one of the poles. The behavior and operating modes of the converter will be described in detail. Several simulation tests will also be provided. From these tests, the behavior and the several operation modes of the DC-DC as well as the multilevel SRM drive supplied by this converter will also be presented and analyzed.

2021-08-10Conference object

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Performance of an a-Si:H MMI multichannel beam splitter analyzed by computer simulation

Publication . Costa, João; Almeida, Daniel; Fantoni, Alessandro; Lourenço, Paulo; Fernandes, Miguel; Vieira, Manuela

Optical power splitters are widely used in many applications and di_erent typologies have been developed for devices dedicated to this function. Among them, the multimode interference design is especially attractive for its simplicity and performance making it a strong candidate for low-cost applications, such as photonics lab-on-chips for biomedical point of care systems. Within this context, splitting the optical beam equally into multiple channels is of fundamental importance to provide reference arms, parallel sensing of di_erent biomarkers and allowing multiplexed reading schemes. From a theoretical point of view, the multimode structure allows implementation of the power splitting function for an arbitrary number of channels, but in practice its performance is limited by lithographic mask imperfections and waveguide width. In this work we analyze multimode waveguide structures, based on amorphous silicon (a-Si:H) over insulator (SiO2), which can be produced by the PECVD deposition technique. The study compares the performance of several 1 to N designs optimized to provide division of the fundamental quasi-TM mode as a function of input polarization and lithographic roughness. The performance is analyzed in terms of output power uniformity and attenuation and is based on numerical simulations using the Beam Propagation Method and Eigenmode Expansion Propagation Methods.

2021-03-05Conference object

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Wayfinding services in crowded buildings through visible light

Publication . Vieira, Manuela; Vieira, Manuel; Louro, Paula; Fantoni, Alessandro; Vieira, Pedro

This paper investigates the applicability of an intuitive risk of transmission wayfinding system in public spaces, virtual races, indoor large environments and complex buildings using Visible Light Communication (VLC). Typical scenarios include: finding places, like a particular shop or office, guiding users across different floors, and through elevators and stairs. The system is able to inform the users, in real time, not only of the best route to the desired destination, through a route without clusters of users, but also of crowded places. Data from the sender is encoded, modulated and converted into light signals emitted by the transmitters. Tetra-chromatic white sources are used providing a different data channel for each chip. At the receiver side, the modulated light signal, containing the ID and the 3D geographical position of the transmitter and wayfinding information, is received by a SiC optical sensor with light filtering and demultiplexing properties. Since lighting and wireless data communication is combined, each luminaire for downlink transmission becomes a single cell, in which the optical Access Point (AP) is located in the ceiling and the mobile users are scattered across the overlap discs of each cell, underneath. The light signals emitted by the LEDs are interpreted directly by the receivers of the positioned users. Bidirectional communication is tested. The effect of the location of the Aps is evaluated and a 3D model for the cellular network is analyzed. In order to convert the floorplan to a 3D geometry, a tandem of layers in a orthogonal topology is used, and a 3D localization design, demonstrated by a prototype implementation, is presented. Uplink transmission is implemented, and the 3D best route to navigate through venue is calculated. Buddy wayfinding services are also considered. The results showed that the dynamic VLC navigation system enables to determine the position of a mobile target inside the network, to infer the travel direction along the time, to interact with received information and to optimize the route towards a static or dynamic destination.

2021Conference object

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Design and optimization of a waveguide/fibre coupler in the visible range

Publication . Lourenço, Paulo; Fantoni, Alessandro; Costa, João; Fernandes, Miguel; Vieira, Manuela

When engineering photonic integrated structures, there will be a time that one must consider coupling out the electromagnetic field to an external device. Often, this coupling is made through a single mode optical fibre. Due to the mismatch in mode field diameters between waveguide and fibre modes, the propagating mode inside the dielectric waveguide must undertake a spot-size conversion. It requires to be radially expanded, often laterally by a tapered waveguide and longitudinally through other means, to match the radial profile of the optical fibre mode. Then, the energy must be coupled out of its propagating path into the plane of the optical fibre, through a structure that possesses such functional purpose. In this work, we describe the design steps and optimization of a silicon nitride waveguide/fibre coupler operating in the visible range. To this end, we start by designing an optimized 3D taper waveguide, using Beam Propagation method, that performs as the spot-size converter. Next, through the Eigen Mode Expansion method, a 2D subwavelength grating is designed and optimized regarding substrate leakage and propagating plane energy coupling out, thus vertically validating the energy distribution of the outgoing profile. The required subwavelength grating apodization is accomplished, once more through the Eigen Mode Expansion method, and by carefully engineering a metamaterial that performs accordingly. The obtained diffraction grating is then expanded horizontally to create a 3D structure and laterally validated through Beam Propagation method. Finally, the whole 3D structure is optimized and validated through Finite Differences Time Domain simulations regarding energy profile coupling out, and overlap integral matching is established with the fibre mode profile.

2021-03-05Conference object

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