Percorrer por autor "Foito, Daniel"
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- An 8/6 SRM drive with a multilevel topology based on a cross-switched configurationPublication . Fernao Pires, Vitor; Foito, Daniel; Pires, Armando J.; Cordeiro, Armando; Martins, J. F.SRM drives based on multilevel power electronic converter presents several advantages, like reducing the switching frequency and improve the operation of the motor under high speed. In this way, several multilevel power converter topologies have been developed for the SRM drives. In line with this, this paper proposes a new multilevel power converter topology for the 8/6 SRM drive. The topology was developed with the purpose to reduce the number of power semiconductors, without reducing the performance of the motor. The proposed topology was designed in a way that uses crossover switches. The operation of the power converter topology in all of their modes is analyzed in a detailed way. The verification of the global system performance (drive and motor) is realized by the implementation of simulation studies. Indeed, through these studies it is verified that at low speed operation the switching frequency is reduced, but maintaining the application of the maximum voltage during the magnetization and demagnetization process.
- A buck-boost converter with extended duty-cycle range in the buck voltage region for renewable energy sourcesPublication . Monteiro, Joaquim; Fernao Pires, Vitor; Foito, Daniel; Cordeiro, Armando; J. F. Silva, Fernando Silva, Fernando A Silva, J. Fernando Silva, J F A Silva, Fernando Silva José; Pinto, SoniaBuck-boost DC-DC converters are useful as DC grid interfaces for renewable energy resources. In the classical buck-boost converter, output voltages smaller than the input voltage (the buck region) are observed for duty cycles between 0 and 0.5. Several recent buck-boost converters have been designed to present higher voltage gains. Nevertheless, those topologies show a reduced duty-cycle range, leading to output voltages in the buck region, and thus require the use of very low duty cycles to achieve the lower range of buck output voltages. In this work, we propose a new buck-boost DC-DC converter that privileges the buck region through the extension of the duty-cycle range, enabling buck operation. In fact, the converter proposed here allows output voltages below the input voltage even with duty cycles higher than 0.6. We present the analysis, design, and testing of the extended buck-boost DC-DC converter. Several tests were conducted to illustrate the characteristics of the extended buck-boost DC-DC converter. Test results were obtained using both simulation software and a laboratory prototype.
- Combining local and remote laboratories for the interactive learning of industrial automationPublication . Cordeiro, Armando; Fernao Pires, Vitor; Foito, DanielThis study presents an educational project for the interactive learning of Industrial Automation. The objective of this project is to allow Bachelor's and Master's students of Electrical Engineering of the Instituto Superior de Engenharia de Lisboa (ISEL-IPL) to learn theoretical and practical fundamentals of Industrial Automation through local and remote laboratory experiments. The proposed pedagogical activities, together with the flexibility of the solution adopted for the laboratory experiments, allow students to acquire advanced knowledge regarding Programmable Logic Controller (PLC) programming languages, Supervisory Control and Data Acquisition (SCADA) applications and industrial communication networks, among other aspects. The main benefits of this educational project are the motivation to engage in problem solving, developing mental strategies based on new hypotheses, step-by-step knowledge construction, and the possibility to interact and change, locally or remotely, the developed programs. Additionally, the adopted laboratory architecture is based on industrial hardware and software, like those found in real applications.
- Combining power electronic converters and automation to simulate solar PV systemsPublication . Cordeiro, Armando; Chaves, Miguel; Gamboa, Paulo; Barata, Filipe; Fonte, Pedro M; Lopes, Hélio; Fernao Pires, Vitor; Foito, Daniel; Amaral, Tito; Martins, JoaoThis paper presents a solar photovoltaic panel simulator system with the ability to perform automatic tests in different condition according to manufacture parameters. This simulator is based on three buck-boost DC-DC converters controlled by a microcontroller and supported by a Programmable Logic Controller which is responsible for the automatic tests. This solution will allow to achieve fast response, like suddenly changes in the irradiation, temperature, or load. To control the power converter, it will be used a fast and robust sliding mode controller. Therefore, with the proposed system is possible to perform the I-V curve simulation of a solar PV panel, evaluate different MPPT algorithms considering different meteorological and load variation. The main advantage of this work is the possibility to evaluate and test several MPPT algorithms and understand the operation and typical operation of solar PV panels in different conditions. Several simulations and experimental results from a laboratory prototype are presented to confirm the theoretical operation.
- Compensation of unbalanced low-voltage grids using a photovoltaic generation system with a dual four-leg, two-level inverterPublication . Fernao Pires, Vitor; Cordeiro, Armando; Foito, Daniel; J. Pires, A.; Hao, Chen; Martins, Joao; Castro, RuiIn this paper, a grid-connected photovoltaic (PV) generation system is proposed with the purpose of providing support to low-voltage grids, namely through the elimination or attenuation of the grid imbalances. This compensation must consider the load types, which can be either linear or non-linear, and whether the reactive power and current harmonics generated by the non-linear loads need to be compensated in addition to the unbalanced active power. This must be well considered, since the compensation of all aspects requires oversized PV inverters. Thus, the different unbalanced compensation schemes are addressed. Several schemes for the generation of the inverter current references taking into consideration the compensation and load type are presented. For this PV generation system, a dual four-leg, two-level inverter is proposed. It provides full unbalanced compensation owing to the fourth leg of the inverter and also extends the AC voltage, which is important when this compensation is required. To control this inverter, a control scheme for the inverter that considers several compensation factors is proposed. A vector voltage modulator associated with the controller is another aspect that is addressed in the paper. This modulator considers the balance between the DC voltages of the inverters. Several compensation schemes are verified through computational tests. The results validate the effectiveness of the proposed PV generation system.
- Control of bidirectional quadratic DC-DC converters for storage support of DC power gridsPublication . Fernao Pires, Vitor; Cordeiro, Armando; Foito, Daniel; Silva, J. FernandoMany applications require a DC bus supporting connections to several renewable energy sources, storage systems and loads. However, due to the intermittent nature of renewable energy sources and load variations it is essential to stabilize the voltage of the DC bus. Usually a battery is used to support the DC bus voltage, but their continuous charge and discharge cycling will affect his lifetime. Thus, the use of a storage system based in supercapacitors provides an interesting alternative to stabilize the DC power grid. In this context, this work presents a study of a storage system based in supercapacitors combined with a bidirectional quadratic DC-DC converter to support the DC bus. A full design of the controllers for the quadratic converter is also presented. The behaviour of the system will be tested through several simulation results.
- Control of PV distributed systems based on three-phase triple inverters to support grids with unbalanced loadsPublication . Fernão Pires, V.; Foito, Daniel; Cordeiro, Armando; Silva, J. FernandoThis paper is focused on the control system for photovoltaic (PV) generators using three-phase triple inverters. These inverters allow for a distributed PV system, and at the same time, they provide AC multilevel operation. The proposed controller is designed to allow the operation of the inverter in a way that it can extend support to the grid with ancillary services. One of the ancillary services that the three-phase triple inverter can support is the injection of unbalanced currents in order to eliminate or attenuate grid load unbalances. Therefore, the proposed topology will be extended to accommodate four wires. The capability of the system to support the grid with ancillary services, especially the compensation of unbalanced loads, the four-wire multilevel topology operation and the proposed controller will be verified through several simulation tests.
- Control transition mode from voltage control to MPPT for PV generators in isolated DC microgridsPublication . Fernao Pires, Vitor; Cordeiro, Armando; Foito, Daniel; Silva, J. FernandoThe integration of photovoltaic (PV) power sources on a large scale into grid-tied and islanded solutions is now a reality. Despite the fluctuating characteristics of solar energy, the direct current (DC) nature of PV sources is highly compatible with DC microgrids compared with AC solutions. However, as more PV sources are being installed, challenges related to the control of DC microgrids are also increasing, especially for islanded applications. To ensure an appropriate transition from the maximum power point to DC bus voltage regulation of DC microgrids, novel control strategies must be designed, and this aspect is particularly critical when these grids operate without energy storage systems. We therefore propose a new control strategy for a PV generator for islanded DC microgrids without storage systems. Our approach allows for smooth switching from the maximum power point mode to the voltage control regulation mode (V control) when the available PV power is excessive, thus limiting the generated PV power and returning to maximum power point operation when all the available power is required. This allows us to control a DC microgrid without a storage system and provides a new alternative that offers a cost-effective solution for rural and deprived regions. Our solution combines the maximum power point tracking algorithm with a proportional integral compensator for V control and minimises undervoltage/overvoltage problems in the DC bus. The behaviour of the isolated DC microgrid under different conditions, for example in the case of transitions, perturbations, and different types of loads, is also studied and verified. The performance of the proposed control strategy is confirmed by several simulation and experimental tests.
- 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.
- A DC-DC Converter With Quadratic Gain and Bidirectional Capability for Batteries/SupercapacitorsPublication . Fernao Pires, Vitor; Foito, Daniel; Cordeiro, ArmandoEnergy storage devices are essential to provide voltage and frequency stability in renewable energy sources, such as solar and wind. Due to operational requirements of distributed generation systems, energy storage devices like batteries and supercapacitors need bidirectional dc-dc converters to allow charge or discharge exchange according with the necessary conditions. In this paper, a new nonisolated bidirectional quadratic converter characterized by high voltage gain in both step-down (Buck) and step-up (Boost) operation modes is proposed. In addition to the wide conversion range, it presents continuous input and output current and reduced charging/discharging ripple. All these features allow an optimized operation between the dc bus and storage devices. The operation principle of the proposed converter in both condition modes (step-down and step-up), the converter design, as well as the theoretical analysis in different conditions will be discussed. Finally, the performance of the proposed converter is confirmed through simulation and experimental results.