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

Due to its advantages Switched Reluctance Motor (SRM) may be used in low and middle power vehicles. However, since this motor is characterized by significant torque pulsation, insufficient power density and complex electric drive it is not widely used, nowadays. Thus, to improve its characteristics, in this paper it is analyzed the SRM structures and it is proposed a proper relationship between the stator and the rotor poles with high energy efficiency. To minimize the torque pulsation a high frequency principle of magnetic flux formation with two section stator is proposed. To adapt the proposed principle a resonant converter with a soft switching, associated to two winding stator poles are used. In this way, the proposed modular SRM electric drive is constituted by only four resonant converters. The SRM electric drive was simulated in MATLAB Simulink® where the results were verified.

High Frequency Modular Electric Drive for Switched Reluctance Motor with Reduced Torque Ripple

Unbalance or asymmetry in the distribution networks is a well-known power quality issue. This power quality problem is even more important in the context of the microgrids since the presence of unbalanced currents can deteriorate the overall operation of equipment and the grid itself. In this context, this article proposes a multilevel inverter based on a cascaded configuration of a four-leg dual inverter. This multilevel inverter is specially appropriated to be used with a photovoltaic (PV) generator connected to a four-wire low-voltage grid. The power converter scheme is based on two four-leg two-level inverters in which three of the ac-side terminals are connected to a three-phase transformer with the primary in open-end winding arrangement. The dc voltage buses of the inverters are connected to two insulated PV arrays. This configuration accepts the injection of the PV generated power into the grid in a way that provides unbalanced load compensation. Additionally, a control system, a pulsewidth modulation modulator, and a current references scheme for the proposed power converter topology are presented. The proposed PV system generator can balance several load unbalances under different operating conditions. It is concluded that the proposed converter can provide significant ancillary services to an unbalanced grid. The system is validated through experimental tests performed under different operating conditions.

A Cascaded Dual Four-Leg Inverter for Photovoltaic Systems With Capability to Compensate Unbalanced Distribution Networks

This 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 of PV Distributed Systems Based on Three-Phase Triple Inverters to Support Grids with Unbalanced Loads

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.

/pdf/a-buck-boost-converter-with-extended-duty-cycle-range-in-the-138gtoud.pdf

A Buck-Boost Converter with Extended Duty-Cycle Range in the Buck Voltage Region for Renewable Energy Sources

This paper presents a three-phase three-level NPC (neutral point-clamped) Dual-Buck inverter topology suitable to increase fault-tolerant capability to safety-critical applications. Using the proposed topology, it is possible to achieve energy processing capability in case of several failure modes. The fault-tolerant enhancements are a consequence of appropriate modifications in the control strategy and from redundancy of power devices to maintain the correct operation of the converter. The proposed control strategy adopted in the presented solution can also equalize the capacitor voltages automatically. Some simulation results are included in this study to confirm the validity of the theoretical study.

/pdf/three-level-npc-dual-buck-inverter-designed-to-safety-36zp6fngsz.pdf

V. Fernao Pires

Papers

High Frequency Modular Electric Drive for Switched Reluctance Motor with Reduced Torque Ripple

A Cascaded Dual Four-Leg Inverter for Photovoltaic Systems With Capability to Compensate Unbalanced Distribution Networks

Control of PV Distributed Systems Based on Three-Phase Triple Inverters to Support Grids with Unbalanced Loads

A Buck-Boost Converter with Extended Duty-Cycle Range in the Buck Voltage Region for Renewable Energy Sources

Three-Level NPC Dual-Buck Inverter Designed to Safety-Critical Applications