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- A DC-DC Converter with Capability to Support the Voltage Balance of DC Bipolar MicrogridsPublication . Pires, Vítor; Foito, Daniel José Medronho; Cordeiro, Armando; Silva, J. FernandoBipolar 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.
- Dual Output and High Voltage Gain DC-DC Converter for PV and Fuel Cell Generators Connected to DC Bipolar MicrogridsPublication . Pires, Vitor Fernão; Cordeiro, Armando; Foito, Daniel José Medronho; Silva, J. Fernando A.This paper introduces a new topology for a DC-DC converter with bipolar output and high voltage gain. The topology was designed with the aim to use only one active power switch. Besides the bipolar multiport output and high voltage gain this converter has another important feature, namely, it has a continuous input current. Due to the self-balancing bipolar outputs, the proposed topology is suitable for bipolar DC microgrids. Indeed, the topology balancing capability can achieve the two symmetrical voltage poles of bipolar DC microgrids. Furthermore, it is possible to create a midpoint in the output of the converter that can be directly connected to the ground of the DC power supply, avoiding common-mode leakage currents in critical applications such as transformerless grid-connect PV systems. The operating principle of the proposed topology will be supported by mathematical analysis. To validate and verify the characteristics of the presented topology, several experimental results are shown.
- Bidirectional DC-DC Converter with High Voltage Gain for the Charge/Discharge Control of Storage SystemsPublication . Pires, Vítor Fernão; Foito, Daniel José Medronho; Martins, J. F.This paper presents a study of a bidirectional dc-dc converter with high voltage gain to regulate the charge and discharge of electrochemical storage systems. The converter is characterized by quadratic voltage gain characteristics in both directions. In this context it can be used to regulate a dc interface between the storage system and a dc/ac converter connected to the electrical grid. It will be analysed the converter in ideal and non-ideal conditions. A control system to regulate the output voltages and currents are also proposed. Simulation results are presented in order to validate the control system associated to the converter for the charge/discharge of the storage system.
- Industrial Automation Self-Learning Through the Develoment of Didactic Industrial ProcessesPublication . Cordeiro, A.; Abraços, M.; Monteiro, L.; Andrade, E.; Foito, Daniel José MedronhoTeaching industrial automation is a complex mission. The classical approach is based on lectures and laboratories assisted by teachers. Nevertheless, teaching industrial automation using the classical approach is not easy because this multidisciplinary area requires knowledge in control, energy, electronics, robotics and computer engineering, among others. In this way, this paper presents an approach to teach Industrial Automation based on a self learning strategy. Instead of using the classical approach, students must develop a research work and a didactic automation prototype. The results of this methodology indicate that students increase the interest about industrial automation and clarify important aspects of assembly, commissioning, parameterization and programming of electric and electronic devices. Additionally this methodology seems to increase self-confidence of students and give them the necessary background to face the challenge of working in the real world.
- PV Generator-Fed Water Pumping System Based on a SRM with a Multilevel Fault-Tolerant ConverterPublication . Pires, Vítor Fernão; Foito, Daniel José Medronho; Cordeiro, Armando; Chaves, Miguel; Pires, A. J.This paper presents a pumping system supplied by a PV generator that is based on a switched reluctance machine (SRM). Water pumping systems are fundamental in many applications. Most of them can be used only during the day; therefore, they are highly recommended for use with PV generators. For the interface between the PV panels and the motor, a new multilevel converter is proposed. This converter is designed in order to ensure fault-tolerant capability for open switch faults. The converter is based on two three-level inverters, with some extra switches. Moreover, to reduce the number of switches, the converter is designed to provide inverse currents in the motor windings. Due to the characteristics of this motor, the inverse currents do not change the torque direction. In this way, it was possible to obtain an SRM drive with fault-tolerant capability for transistor faults; it is also a low-cost solution, due to the reduced number of switches and drives. These characteristics of fault-tolerant capability and low cost are important in applications such as water pumping systems supplied by PV generators. The proposed system was verified by several tests that were carried out by a simulation program. The experimental results, obtained from a laboratory prototype, are also presented, with the purpose of validating the simulation tests.
- A SRM for a PV Powered Water Pumping System Based on a Multilevel Converter and DC/DC Dual Output ConverterPublication . Foito, Daniel José Medronho; Cordeiro, Armando; Chaves, Miguel; Martins, J. F.This paper focuses on a proposal for a system based on a photovoltaic (PV) supply for a powered water pumping. The system consists in a switched reluctance machine (SRM) controlled by a multilevel converter and fed by PV panels associated to a DC/DC converter. The multilevel power converter proposed to control the SRM was designed to minimize the switches and to support the balance of the two input capacitors. The DC/DC converter consists in a hybrid solution that merges a Buck- Boost converter with a Sepic converter. They use a topology solution in which the input current presents a reduced ripple and only requires one switch. This DC/DC converter is also characterized by a dual output to adapt to the multilevel converter. The control system and a maximum power point tracking (MPPT) algorithm are also presented. The operation of this system will be verified by tests that are done by computer simulations.
- A Fault Diagnosis Scheme Based on the Normalized Indexes of the Images eccentricity for a Multilevel Converter of a Switched Reluctance Motor DrivePublication . Amaral, Tito G.; Pires, Vitor; Foito, Daniel José Medronho; Cordeiro, Armando; Rocha, José Inácio Pinto Rosado; Pires, A. J.; Martins, J. F.This paper addresses the fault detection and diagnosis of a fault in the switches of the Switched Reluctance Machine (SRM) power electronic converter. Due to the advantages of using multilevel converters with these machines, a fault detection and diagnosis algorithm is proposed for this converter. The topology under consideration is the asymmetric Neutral Point Clamped (ANPC), and the algorithm was developed to detect open and short circuit faults. The proposed algorithm is based on an approach that discriminates eccentricity of the images formed by the converter voltages. This discrimination is realized through the development of normalized indexes based on the entropy theory. Besides the different fault type the algorithm is also able to detect the transistor under fault. The possibility to implement the proposed approach will be verified through simulation tests.
- Road Motion Control Electric Vehicle with Speed and Torque ObserverPublication . Foito, Daniel José Medronho; Gaspar, Manuel; Pires, V. FernãoThis paper presents an electric vehicle (EV) with two independent rear wheel drives and with an electric differential system. A model of the vehicle dynamic model is presented. The electric differential was implemented assuring that, in straight right trajectory, the two wheels drives roll exactly at same velocity and, in curve, the difference between the two velocities assure a vehicle trajectory. A speed and torque observer for DC motor was also proposed and simulated. Analysis and simulation results of the proposed system are presented.
- A Review of the Power Converter Interfaces for Switched Reluctance MachinesPublication . Pires, Vítor Fernão; Pires, A. J.; Cordeiro, Armando; Foito, Daniel José MedronhoThe use of power electronic converters is essential for the operation of Switched Reluctance Machines (SRMs). Many topologies and structures have been developed over the last years considering several specific applications for this kind of machine, improving the control strategies, performance range, fault-tolerant operation, among other aspects. Thus, due to the great importance of power electronic converters in such applications, this paper is focused on a detailed review of main structures and topologies for SRM drives. The proposed study is not limited to the classic two-level power converters topologies dedicated to the SRMs; it also presents a review about recent approaches, such as multilevel topologies and based on impedance source network. Moreover, this review is also focused on a new class of topologies associated to these machines, namely the ones with fault-tolerant capability. This new category of topologies has been a topic of research in recent years, being currently considered an area of great interest for future research work. An analysis, taking into consideration the main features of each structure and topology, was addressed in this review. A classification and comparison of the several structures and topologies for each kind of converter, considering modularity, boost capability, number of necessary switches and phases, integration in the machine design, control complexity, available voltage levels and fault-tolerant capability to different failure modes, is also presented. In this way, this review also includes a description of the presented solutions taking into consideration the reliability of the SRM drive.
- Fault-Tolerant SRM Drive with a Diagnosis Method Based on the Entropy Feature ApproachPublication . Pires, Vitor Fernão; Amaral, Tito G.; Cordeiro, Armando; Foito, Daniel José Medronho; Pires, A. J.; Martins, João F.The power electronic converter design is essential for the operation of the switched reluctance motor (SRM). Thus, a fault-tolerant power converter is fundamental to ensure high reliability and extend the drive operation. To achieve fault tolerance, fault detection and diagnosis methods are critical in order to identify, as soon as possible, the failure mode of the drive. To provide such capability, it is proposed in this paper a new fault-tolerant power converter scheme combined with a fault detection method regarding the most common power semiconductors failures in SRM drives. The fast and reliable proposed diagnosis method is based on the entropy theory. Based on this theory, normalized indexes (diagnostic variables) are created, which are independent from the load and speed of the motor. Through this method, it is possible to identify the faulty leg, as well as the type of power semiconductor fault. To test and evaluate the proposed solution several laboratory experiments were carried out using a 2 kW four-phase 8 / 6 SRM.