http://ieeexplore.ieee.org/iel5/5610941/5624686/05624745.pdf

Power electronics

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.<<ETX>>

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

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.

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

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.

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

A sparse auto-encoder-based deep neural network approach for induction motor faults classification

A new paradigm has appeared in the electricity sector with the rapid development of new renewable energy sources, storage systems, information and communication technologies, and ways of integrating distributed energy sources [...]

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Smart Grid as a Key Tool for the Future of Electrical Distribution Networks

Low-voltage (LV) distribution networks are unbalanced and present loads with nonlinear behavior, which introduce harmonics in the networks. The predictable increase in photovoltaic microgeneration (PV µG) accentuates this unbalanced characteristic, as well as poses new technical problems, namely voltage rise and reverse power flow. To accurately account for the distributed PV and loads in the LV network, unbalanced three-phase power flow algorithms should be utilized, where different approaches may be used to represent lines with various degrees of accuracy. The more accurate algorithm considers the electromagnetic coupling between the line conductors, whereas the simpler algorithm represents each conductor of the line as a single-phase line with pure resistive behavior. This paper aims to analyze the influence of the line model on the load flow in a highly unbalanced LV network with a high penetration of PV production, and considers the impact of the harmonics produced by nonlinear loads. Based on the results obtained, it is possible to identify the most suitable model to be used, depending on the study to be performed. Different scenarios of PV generation and loads are addressed in this paper. 

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Multi-conductor Line Models for Harmonic Load-flow Calculations in LV Networks with High Penetration of PV Generation

The use of distributed architectures for PV panels present several advantages over centralized solutions, such as better harnessing of the generated energy and improved reliability of the system. Therefore, several inverter structures have been proposed to ensure proper operation of distributed architectures and at the same time generate multilevel voltages. A newly proposed structure uses three three-phase two-level inverters. Thus, in this paper a new control system is proposed for grid-connected PV systems with this structure. The proposed control system is based on a sliding mode AC current controller that uses space-vector voltage modulators. The proposed control system is also designed to inject unbalanced power into the grid to provide an ancillary service regarding power unbalances. The proposed controller for the mentioned structure is then tested through several simulations considering different case studies.

Sliding Mode Vector Control of Grid-Connected PV Multilevel Systems Based on Triple Three-Phase Two-Level Inverters

High Voltage Direct Current (HVDC) is an effective technology planned to deliver large amounts of electrical energy over long distances with negligible losses. Due to the high power and voltage associated to this application, the multilevel converter topologies are most interesting. Besides that, these topologies are also characterized by their reliability. One of the proposed multilevel topologies based in well-known three-phase voltage source inverter is the dual inverter. This topology is also characterized by a dual DC-link. Thus this paper will present a control system for this converter taking into consideration a DC short circuit fault ride-through. In fact, from this study it will be possible to verify that even in a situation of short-circuit in a DClink, the system maintains their capability to transfer the energy, although at reduced power. This capability is confirmed through a case study.

The HVDC Dual Transmission System Under DC Short-Circuit Faults

In the past years, the Electrical Utility Industry has been confronted with numerous challenges, which include amongst others, the widespread use of distributed energy resources and a public increase in environmental issues. By optimizing the location of switching devices on the electrical distribution system, an improvement in energy not supplied and in the use of distributed energy resources can be obtained. This work proposes the genetic evolutionary algorithm NSGA-II for the multiobjective optimal placement of the switching devices. A trade-off between the investment in switching devices, energy not supplied and greenhouse gas emissions is analyzed, in order to choose the optimal placement of switching devices in distribution electrical networks. The proposed method was tested with a Portuguese real distribution network. The obtained results are presented and discussed.

V. Fernao Pires

Papers

Smart Grid as a Key Tool for the Future of Electrical Distribution Networks

Multi-conductor Line Models for Harmonic Load-flow Calculations in LV Networks with High Penetration of PV Generation

Sliding Mode Vector Control of Grid-Connected PV Multilevel Systems Based on Triple Three-Phase Two-Level Inverters

The HVDC Dual Transmission System Under DC Short-Circuit Faults

Multiobjective switching devices placement considering environmental constrains in distribution networks with distributed energy resources