V. Fernao Pires

Bio: V. Fernao Pires is an academic researcher from INESC-ID. The author has contributed to research in topics: Inverter & Fault (power engineering). The author has an hindex of 18, co-authored 154 publications receiving 1457 citations. Previous affiliations of V. Fernao Pires include Technical University of Lisbon & University of Lisbon.

Rotor fault diagnosis in induction motors using S-Transform

Abstract: This paper proposes the use of the S-Transform applied to the stator currents as a method for diagnosing the occurrence of rotor electrical fault (broken bars or faulty rotor windings) in induction motor. Induction motor stator currents are first measured and recorded. Then, the S-Transform is applied to the obtained currents in order to get a specific pattern that allows the identification of the rotor fault. Simulation and experimental results, for both a healthy motor and a motor with a rotor electrical fault, are presented in order to show the effectiveness of the proposed method.

A DC-DC Converter with Capability to Support the Voltage Balance of DC Bipolar Microgrids

Abstract: Bipolar DC microgrids are now starting to become an interesting solution for power distribution. Although presenting several advantages over DC unipolar microgrids, bipolar DC has the intrinsic problem of voltage unbalance that may appear depending on the converter topology and load sharing. Therefore, this paper presents a new DC-DC converter topology that can be used with renewable energy sources and has the capability to simultaneously ensure the bipolar microgrid voltage balance. The operation of the proposed topology together with its characteristics is described. A theoretical study of this converter will also be presented, complemented by a set of results from computer simulations. To support these simulations, results from a laboratory prototype will also be displayed. The voltage balance capability of the converter will be checked experimentally.

Grammatical flux estimator for sensorless ac-drives

Abstract: This paper presents a novel grammatical flux estimator for sensorless ac-drives. The proposed methodology does not require the integration of the standard voltage model neither the exact knowledge of the system parameters. Assuming the flux estimator as a linguistic source, producing a certain language, a grammatical inference algorithm is used to extract the productions that govern the grammar representing that language. The formalism of the developed formal language based control algorithm is presented. The inherent non-linear characteristics of the grammar productions make it possible to obtain accurate flux estimation. Application results are presented in order to show the effectiveness of the proposed methodology.

A physical laboratory for energy efficiency education

Abstract: This paper describes a new laboratory that was developed to teach undergraduate students at School of Technology of Setubal/Polytechnic Institute of Setubal, Portugal, some of the main issues regarding the problem of energy efficiency. Achieving energy efficiency is important since is seen as a powerful and cost-effective tool for achieving a sustainable energy future. So, the need for teaching energy efficiency methodologies is today very important. However, the pedagogical approach where the students revisit previously studied material placed in a practical context is fundamental. Practical experience also increases the interest of students, since it allows connecting the theory to practice. Under this context, this laboratory provides to students experimental work. Several examples of experiments are presented and discussed. Since it is very important that everyone contributes to energy efficiency, this laboratory was also developed in order to receive ordinary people.

A modeling scheme for the Le Blanc transformer

Abstract: One of the major problems in power networks due to AC electrified railway systems is voltage and current unbalance. Several methods can be used for reducing these unbalancing problems. Several methods can be used for reducing these unbalancing problems, being one of the most used specially connected transformers. Several transformer connection schemes, including single-phase, V-V, Scott, and Le Blanc connections, are usually considered. The Le-Blanc transformer is a special winding connection transformer adopted for the single-phase power supply of electrified railway systems. This paper deals with a modeling scheme for the Le-Blanc transformer. Simulation and experimental results are presented in order to show the effectiveness of the proposed method.

Multi-level conversion : high voltage choppers and voltage-source inverters

Abstract: The authors discuss high-voltage power conversion. Conventional series connection and three-level voltage source inverter techniques are reviewed and compared. A novel versatile multilevel commutation cell is introduced: it is shown that this topology is safer and more simple to control, and delivers purer output waveforms. The authors show how this technique can be applied to either choppers or voltage-source inverters and generalized to any number of switches.<>

Recent Advances in the Design, Modeling, and Control of Multiphase Machines—Part II

Abstract: The main objective of this two-part state-of-the-art paper called “Recent Advances in the Design, Modeling, and Control of Multiphase Machines” is to present latest contributions in the multiphase machines' field. The first part of this paper focuses on the recent progress in the design, modeling, and control, whereas the drive is in healthy operation. This second part presents relevant contributions in two not analyzed fields. The first is in relation with the use of the additional degrees of freedom of multiphase machines and the exploitation of their fault-tolerant capabilities without adding extra hardware. The second one analyzes multiphase generation, particularly in grid-connected wind energy conversion systems and stand-alone applications. Recent progresses are shown and open challenges and future research directions are discussed.

Overview of Control Systems for the Operation of DFIGs in Wind Energy Applications

Abstract: Doubly fed induction generators (DFIGs), often organized in wind parks, are the most important generators used for variable-speed wind energy generation. This paper reviews the control systems for the operation of DFIGs and brushless DFIGs in wind energy applications. Control systems for stand-alone operation, connection to balanced or unbalanced grids, sensorless control, and frequency support from DFIGs and low-voltage ride-through issues are discussed.