Browsing by Author "Pires, A. J."
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- A DC-DC converter for bipolar DC microgrids with voltage balance capability to supply a multilevel SRM drivePublication . 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.
- Hybrid Sepic-Ćuk DC-DC Converter Associated to a SRM Drive for a Solar PV Powered Water Pumping SystemPublication . Cordeiro, Armando; Chaves, Miguel; Canacsinh, Hiren; Luís, Ricardo; Fernao Pires, Vitor; Foito, Daniel; Pires, A. J.; Martins, JoaoThe present paper describes a solar photovoltaic (SPV) powered water pumping system employing a switched reluctance motor (SRM) and a merged Sepic-Ćuk DC-DC converter. The proposed solution was designed to use efficiently the available solar energy in order to supply water pumping systems. Solutions of this kind assume a special importance in the current scenario of natural and renewable resources optimization. The proposed DC-DC converter operates in continuous conduction mode (CCM), which combined with a maximum power point tracking (MPPT) controller, helps to optimize the power of the solar photovoltaic panel (SPV). The proposed DC-DC topology is characterized by high voltage static gain when compared with the classical boost topology and reduced voltage stress across the power switch and diodes. Several simulation and experimental results are presented in order to confirm the characteristics of the proposed solution for water pumping systems.
- Multilevel converter fed SRM Drive for Single stage PV array based water pumpingPublication . Fernao Pires, Vitor; Foito, Daniel; Pires, A. J.; Cordeiro, Armando; Martins, J. F.; Chen, HaoIn this work it is proposed a switched reluctance machine (SRM) drive supplied by a renewable source (PV array) to operate a water pumping system. To improve the speed of the commutation between phases it is proposed the use of a multilevel converter for the SRM drive. This converter was designed to reduce the number of controlled power semiconductors, reducing the cost of the system. To obtain the maximum power extraction of the PV system is proposed the use of an algorithm based on the product of the time derivative of power with the time derivative of voltage. A control system to ensure the balance between the power generated by the renewable source and the water pumping system is also proposed. The operation and characteristics of the system will be verified by several numerical tests.
- Multilevel converter with fault-tolerant capability for the switched reluctance machinePublication . Fernão Pires, V.; Cordeiro, Armando; Foito, Daniel; Pires, A. J.Many critical systems require permanent operation even in a situation of a fault. In this way, electrical drives that are associated to these systems must have fault-tolerant capability. One of the machines that are used in many systems is the switched reluctance machine (SRM). To achieve the best performance with a wide speed range, multilevel converters are one of the adopted options. Thus, this paper presents a new multilevel converter for the SRM with fault-tolerant capability. The proposed solution allows to maintain the drive at operation for both conditions of opencircuit and short-circuit power semiconductor fault. Their operation in normal and fault-tolerant modes for the 8/SRM is presented in detail. To verify the capability and operation modes of the proposed system several simulation tests will be presented.
- A multilevel fault-tolerant power converter for a switched reluctance machine drivePublication . Fernao Pires, Vitor; Cordeiro, Armando; Foito, Daniel; Pires, A. J.; Martins, Joao; Chen, HaoReliability in the electrical drives is becoming an important issue in many applications. In this context, the reliability associated to the switched reluctance machine (SRM) is also an important area of research. One of the major problems, that strongly affect its operation, are drive power semiconductors faults. Typical power converter topologies used in SRM drives cannot handle faults in their power semiconductors. So, this paper presents a power converter topology that provides fault-tolerant capabilities to the drive under a switch fault. This power converter will be used considering that a change in the direction of the current that flows in the SRM windings does not affect the behavior of the machine. Besides that, the proposed power converter will allow to generate multilevel phase voltages in order to apply different voltage levels as function of the SRM speed. A laboratory power converter was developed to test the SRM drive in normal and faulty conditions. From the obtained results it was possible to verify the fault-tolerant capability of the drive under switch faults in different devices and failure modes. It was also possible to confirm the multilevel operation of the drive.
- Multilevel inverter based on a dual two-level nine-switch converter for a dual three-phase or six-phase motor drive systemPublication . Pires, V. Fernão; Cordeiro, Armando; Foito, Daniel; Pires, A. J.; Silva, J. Fernando A.; Chen, HaoThe nine-switch inverter is considered as a very interesting solution for three-phase dual output applications, such as dual three-phase or six-phase motor drive systems. The main advantage of this approach is a converter topology with a reduced number of power semiconductors. However, the AC output voltages are limited to only two levels. This work proposes a new inverter topology for dual three-phase or six-phase motor drive systems with multilevel output characteristics. The proposed topology is based on two isolated inverters, but the number of legs is reduced from six to three. This structure creates a modular multilevel inverter with a high number of voltage levels while using a comparatively smaller number of power semiconductors. A modulation strategy, associated with the proposed topology, is presented to ensure multilevel operation. The proposed topology and modulation strategy will be tested first through a simulation in Matlab/Simulink and then by laboratory tests using an experimental prototype. The obtained results show a good agreement between simulations and experiments, both confirming the theoretical studies.
- A multilevel topology based on the T-Type converter for SRM drivesPublication . Fernao Pires, Vitor; Cordeiro, Armando; Pires, A. J.; Martins, João; Chen, HaoMultilevel power converters have been used in SRM drives to improve high speed operating characteristics and reduce switching frequency. Several topologies have been proposed to these drives but it requires an increased number of switches. In this paper it is presented a new multilevel topology for the SRM drives. This topology is based on the T-type structure and characterized by a reduced number of power semiconductors resulting in a low cost, size and weight system. With this topology it is possible to accelerate the magnetization and demagnetization process as well as the efficiency of the system through the reduction of the switching frequency at low speed operation. The characteristics and performance of the proposed topology will be verified through several numerical tests.
- Three-level quadratic boost DC-DC converter associated to a SRM drive for water pumping photovoltaic powered systemsPublication . Cordeiro, Armando; Fernao Pires, Vitor; Foito, Daniel; Pires, A. J.; Martins, J. F.This paper presents a water pumping system powered by solar photovoltaic (PV) panels employing a switched reluctance motor (SRM) drive and a three-level quadratic Boost (3LQB) DC-DC converter for a dual output. The DC-DC topology is characterized by quadratic voltage static gain, capability to ensure voltage balance in the output capacitors and reduced voltage stress across power switches and diodes. The three-level voltage of the DC-DC converter allows to connect an asymmetrical half-bridge (AHB) converter integrated into the SRM drive. The DC-DC converter also operates in continuous conduction mode (CCM) which, combined with a proposed maximum power point tracking (MPPT) algorithm, helps to optimize the power supplied by the PV panels. A laboratory prototype was also developed and installed in a workbench to verify its practical implementation considering all devices involved. The tests were performed considering different loads and solar irradiations to verify the system performance under different situations. The PV panels were simulated using a remotely controlled DC power source to impose the typical characteristic I-V curves of the PV panels according to solar irradiation and the water pump behavior was emulated in the laboratory using a controlled torque load coupled to the SRM drive. The experimental results indicate that the proposed solution allows to fully exploit the solar energy to provide as much as possible a continuous water flow in isolated pumping solutions. The operating limits of this solution should be determined by the minimum water flow rate required, necessary head (elevation) and net positive suction head (NPSH).