Fault-tolerant multilevel converter to feed a switched reluctance machine

The switched reluctance machine (SRM) is one of the most interesting machines, being adopted for many applications. However, this machine requires a power electronic converter that usually is the most fragile element of the system. Thus, in order to ensure high reliability for this system, it is fundamental to design a power electronic converter with fault-tolerant capability. In this context, a new solution is proposed to give this capability to the system. This converter was designed with the purpose to ensure fault-tolerant capability to two types of switch faults, namely open- and short-circuit. Moreover, apart from this feature, the proposed topology is characterized by a multilevel operation that allows improvement of the performance of the SRM, taking into consideration a wide speed range. Although the proposed solution is presented for an 8/6 SRM, it can be used for other configurations. The operation of the proposed topology will be described for the two modes, fault-tolerant and normal operation. Another aspect that is addressed in this paper is the proposal of fault detection and diagnosis method for this fault-tolerant inverter. It was specifically developed for a multilevel SRM drive. The theoretical assumptions will be verified through two different types of tests, firstly by simulation and secondly by experiments with a laboratory prototype.info:eu-repo/semantics/publishedVersio

PV generator-fed water pumping system based on a SRM with a multilevel fault-tolerant converter

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.info:eu-repo/semantics/publishedVersio

Compensation of unbalanced low-voltage grids using a photovoltaic generation system with a dual four-leg, two-level inverter

In 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.info:eu-repo/semantics/publishedVersio

A SRM for a PV powered water pumping system based on a multilevel converter and DC/DC dual output converter

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.info:eu-repo/semantics/publishedVersio

Three-phase T-type qZ source inverter with control current associated to a vectorial modulator for photovoltaic applications

This paper presents a fast and robust control system for a three-phase quasi-Z-source inverter (qZSI) connected to the grid. The topology combines two quasi-Z-source networks with a T-type inverter allowing to obtain AC voltages with multilevel characteristics and properties of the referred networks. To control this system a closed-loop current controller for the AC currents is proposed. The controller is based on a vectorial modulator associated to the shoot-through states. The DC-link voltage is maintained stable at the reference value by adjusting the shoot-through duty cycle. The controller is characterized by fast transient response and robustness to parameter and load variations. In order to confirm the desired characteristics and performance of the converter and control system several simulation tests were performed.info:eu-repo/semantics/publishedVersio

Hybrid Sepic-Ćuk DC-DC Converter Associated to a SRM Drive for a Solar PV Powered Water Pumping System

Este trabalho foi financiado pelo Concurso Anual para Projetos de Investigação, Desenvolvimento, Inovação e Criação Artística (IDI&CA) 2019 do Instituto Politécnico de Lisboa. Código de referência IPL/2019/SOLARPUMP_ISELThe 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.info:eu-repo/semantics/publishedVersio

Combining power electronic converters and automation to simulate solar PV systems

This 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.info:eu-repo/semantics/publishedVersio

A buck-boost converter with extended duty-cycle range in the buck voltage region for renewable energy sources

Buck-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.info:eu-repo/semantics/publishedVersio

A remote and on-site educational tool to improve the learning process of electrical power distribution and utilization systems

In this paper, the development of an educational tool to improve the learning process about electrical power distribution and utilization systems in power system courses is presented. Usually, power system courses cover several concepts from the generation of electrical energy, transportation, interconnection, transformation, protection, distribution to final consumption. Most concepts are taught using theoretical circuit analysis, mathematical models and simulations in the classroom and laboratories. To improve the learning of some concepts, some technical tours to power stations and substations are made whenever possible. However, experimental exercises in power system courses are very difficult to implement due to safety reasons since most power equipment operates with high voltages. To mitigate this problem and motivate students in this area, a new power system educational tool to simulate electrical power distribution and utilization systems is proposed. The proposed system was developed using a Programmable Logic Controller (PLC) and other industrial equipment. The proposed pedagogical activities of the educational project and the results achieved with this new update are discussed in this study.info:eu-repo/semantics/publishedVersio

Combining local and remote laboratories for the interactive learning of industrial automation

This 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.info:eu-repo/semantics/publishedVersio