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Publications

Publications by Rui Esteves Araujo

2018

Modeling and Simulation of a Switched Reluctance Motor with Hysteresis Effect

Authors
Melo, P; Araujo, RE;

Publication
2018 INTERNATIONAL SYMPOSIUM ON POWER ELECTRONICS, ELECTRICAL DRIVES, AUTOMATION AND MOTION (SPEEDAM)

Abstract
Switched reluctance machines (SRM) are simple, robust and fault tolerant machines, usually operating under strong nonlinear characteristics. Therefore, accurately modeling this machine is a demanding task. Several models have been proposed, where magnetic saturation is often addressed, without considering hysteresis effect. In the proposed model the SRM magnetization characteristics are generated through the Jiles-Atherton (J-A) hysteresis model. Thus, instead of a post-processing inclusion, hysteresis is considered in simulation. This is the model main attribute, which is discussed in detail. This may contribute for a better understanding of hysteresis impact over the SRM operation modes. Simulation results are also presented and discussed.

2018

A Practical Comparison of Two Algorithms for Inverter Control with Virtual Inertia Emulation

Authors
Barbosa, D; Ramos, J; Rodrigues, J; Lopes, A; Araujo, RE;

Publication
2018 POWER SYSTEMS COMPUTATION CONFERENCE (PSCC)

Abstract
Renewable energy sources are environmentally appealing in electrical power grids. However, distributed energy resources (DER) are typically connected to the grid through converters that do not have the same properties as synchronous generators which have high participation in power generation. Some of these properties like inertial response are important and must not be lost with higher DER penetration. The present paper analyses two converter control algorithms that are capable of emulating inertial response in DER: the Virtual Synchronous Generator control (VSG) and the Synchronverter. Both algorithms are described, implemented and tested in a practical experiment and a comparison of both algorithms is assessed in terms of frequency nadir achieved, settling time and implementation complexity. The findings can give useful insights to help decide which algorithm should be implemented in a future real application.

2018

EMI Filter Design for a Single-stage Bidirectional and Isolated AC-DC Matrix Converter

Authors
Varajao, D; Araujo, RE; Miranda, LM; Pecas Lopes, JAP;

Publication
ELECTRONICS

Abstract
This paper describes the design of an electromagnetic interference (EMI) filter for the high-frequency link matrix converter (HFLMC). The proposed method aims to systematize the design process for pre-compliance with CISPR 11 Class B standard in the frequency range 150 kHz to 30 MHz. This approach can be extended to other current source converters which allows time-savings during the project of the filter. Conducted emissions are estimated through extended simulation and take into account the effect of the measurement apparatus. Differential-mode (DM) and common-mode (CM) filtering stages are projected separately and then integrated in a synergistic way in a single PCB to reduce volume and weight. A prototype of the filter was constructed and tested in the laboratory. Experimental results with the characterization of the insertion losses following the CISPR 17 standard are provided. The attenuation capability of the filter was demonstrated in the final part of the paper.

2016

Indoor localization using barely perceptible audio signals

Authors
Moutinho, J; Freitas, D; Araújo, RE;

Publication
U.Porto Journal of Engineering

Abstract
This paper presents a new approach to an audio-based indoor localization system. By using audio signals emitted by a public address sound system, mobile devices may globally localize themselves in an indoor environment where global navigation satellite systems are not viable or reliable. The use of data hiding techniques such as spread spectrum coding or echo hiding has allowed to convey information to a receiver avoiding people’s perception of the added audio content. Results demonstrate a relatively quite good localization with centimetre accuracy and precision and successful data transmission using barely perceptible audio signals.

2016

Model-based predictive control implementation for cooperative adaptive cruise control

Authors
Lopes, A; Araújo, RE;

Publication
U.Porto Journal of Engineering

Abstract
The automation of road vehicles has become a necessity to improve the efficiency and safety of this system. In a vehicle formation it is important to maintain a safety distance between the vehicles. The control of a vehicle spacing distance and longitudinal velocity can be achieved through the implementation of a model-based predictive controller. This implementation of a cooperative adaptive cruise control allows the access of another vehicle state information through vehicular communication technology and promote state prediction and ultimately system stability. The optimization algorithm performs the computation of the control input in a control horizon window and ensures that the spacing error takes only positive values. The results of the proposed controller are evaluated through the computational tool Simulink in the two-vehicle platoon. The controller is implemented in the precedent vehicle. To assess the performance of the proposed controller different control parameters and constraints were used.

2018

Modeling a Switched Reluctance Motor with Static Magnetic Hysteresis: Impact on High-Speed Operation

Authors
Melo, P; Araújo, RE;

Publication
2018 XIII INTERNATIONAL CONFERENCE ON ELECTRICAL MACHINES (ICEM)

Abstract
Switched reluctance machines (SRM) are simple, robust and fault tolerant machines, usually operating under strong nonlinear characteristics. Therefore, accurately modeling this machine is a demanding task. Several models have been proposed, where magnetic saturation is often addressed, without considering hysteresis effect. In the proposed model, the SRM magnetization characteristics are generated through the Jiles-Atherton (J-A) hysteresis model. Thus, instead of a post-processing inclusion, static hysteresis is considered in simulation. This is the model main attribute, which is discussed in detail. This may contribute for a better understanding of hysteresis impact over the SRM operation, limited to static modes. Simulation results are also presented and discussed.

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