Multilevel inverter technology has emerged recently as a very important alternative in the area of high-power medium-voltage energy control. This paper presents the most important topologies like diode-clamped inverter (neutral-point clamped), capacitor-clamped (flying capacitor), and cascaded multicell with separate DC sources. Emerging topologies like asymmetric hybrid cells and soft-switched multilevel inverters are also discussed. This paper also presents the most relevant control and modulation methods developed for this family of converters: multilevel sinusoidal pulsewidth modulation, multilevel selective harmonic elimination, and space-vector modulation. Special attention is dedicated to the latest and more relevant applications of these converters such as laminators, conveyor belts, and unified power-flow controllers. The need of an active front end at the input side for those inverters supplying regenerative loads is also discussed, and the circuit topology options are also presented. Finally, the peripherally developing areas such as high-voltage high-power devices and optical sensors and other opportunities for future development are addressed.

Multilevel inverters: a survey of topologies, controls, and applications

Multilevel converters have been under research and development for more than three decades and have found successful industrial application. However, this is still a technology under development, and many new contributions and new commercial topologies have been reported in the last few years. The aim of this paper is to group and review these recent contributions, in order to establish the current state of the art and trends of the technology, to provide readers with a comprehensive and insightful review of where multilevel converter technology stands and is heading. This paper first presents a brief overview of well-established multilevel converters strongly oriented to their current state in industrial applications to then center the discussion on the new converters that have made their way into the industry. In addition, new promising topologies are discussed. Recent advances made in modulation and control of multilevel converters are also addressed. A great part of this paper is devoted to show nontraditional applications powered by multilevel converters and how multilevel converters are becoming an enabling technology in many industrial sectors. Finally, some future trends and challenges in the further development of this technology are discussed to motivate future contributions that address open problems and explore new possibilities.

/pdf/recent-advances-and-industrial-applications-of-multilevel-26fluutoc9.pdf

Recent Advances and Industrial Applications of Multilevel Converters

This paper reviews the current status and implementation of battery chargers, charging power levels, and infrastructure for plug-in electric vehicles and hybrids. Charger systems are categorized into off-board and on-board types with unidirectional or bidirectional power flow. Unidirectional charging limits hardware requirements and simplifies interconnection issues. Bidirectional charging supports battery energy injection back to the grid. Typical on-board chargers restrict power because of weight, space, and cost constraints. They can be integrated with the electric drive to avoid these problems. The availability of charging infrastructure reduces on-board energy storage requirements and costs. On-board charger systems can be conductive or inductive. An off-board charger can be designed for high charging rates and is less constrained by size and weight. Level 1 (convenience), Level 2 (primary), and Level 3 (fast) power levels are discussed. Future aspects such as roadbed charging are presented. Various power level chargers and infrastructure configurations are presented, compared, and evaluated based on amount of power, charging time and location, cost, equipment, and other factors.

/pdf/review-of-battery-charger-topologies-charging-power-levels-85yy2igx2w.pdf

Review of Battery Charger Topologies, Charging Power Levels, and Infrastructure for Plug-In Electric and Hybrid Vehicles

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

Power electronics

Cascaded multilevel inverters synthesize a medium-voltage output based on a series connection of power cells which use standard low-voltage component configurations. This characteristic allows one to achieve high-quality output voltages and input currents and also outstanding availability due to their intrinsic component redundancy. Due to these features, the cascaded multilevel inverter has been recognized as an important alternative in the medium-voltage inverter market. This paper presents a survey of different topologies, control strategies and modulation techniques used by these inverters. Regenerative and advanced topologies are also discussed. Applications where the mentioned features play a key role are shown. Finally, future developments are addressed.

A Survey on Cascaded Multilevel Inverters

The short-circuit reliability of power switches plays very important part in many applications, where a 10μs short-circuit duration at 400V is usually required for 650V switches. Although emerging high voltage AlGaN/GaN HEMT technologies have shown switching advantages, the short-circuit performance has not been thoroughly investigated. In this work, we present an experimental study and numerical simulation analysis of 650V AlGaN/GaN HEMTs short-circuit safe-operating-area (SCSOA), and provide a theory for the reduction in ruggedness at high voltage short circuit conditions.

Experimental study of 650V AlGaN/GaN HEMT short-circuit safe operating area (SCSOA)

The superior material properties of the wide bandgap silicon carbide (SiC) semiconductors enable excellent device characteristics such as low on-resistance, high breakdown voltage, fast switching speed, high temperature operation, etc. 10-kV SiC junction barrier Schottky (JBS) diode prototype made by Cree was characterized in this paper first. The high-voltage (HV) and high-frequency rectifier consisting of SiC JBS diodes in dc-dc converters can potentially benefit from the device characteristics. However, capacitive current in both forward and reverse recovery process is observed due to the junction capacitance when the SiC JBS diode is turned on and off, which increases the reactive power and reduces the rectifier output power and voltage. To better utilize the devices, the rectifier operation is analyzed in consideration of the impact of the JBS diode parasitic capacitance. Two equivalent circuit models, the series and the parallel input impedance model, are proposed. The distributed junction capacitance of JBS diodes is lumped into the equivalent input capacitance such that the input impedance and output voltage, two critical parameters in HV dc-dc converter design, can be predicted from the models. Experiment setup of SiC JBS diode rectifier was built and the test results verified the modeling work.

Modeling of the High-Frequency Rectifier With 10-kV SiC JBS Diodes in High-Voltage Series Resonant Type DC–DC Converters

In this paper, a comparison of three semiconductor devices suitable for high power applications is presented. All devices feature high switching speed and snubberless turn-off capability. The devices compared include one high voltage insulated gate bipolar transistor (HVIGBT) and two types of hard-driven GTO thyristor-the gate commutated turn-off (GCT) thyristor and the emitter turn-off (ETO) Thyristor. The conduction and switching characteristics are compared, and an assessment is presented of the impact on high-power converter circuits for these devices. Test results are shown.

Comparison of the state-of-the-art high power IGBTs, GCTs and ETOs

This paper reviews the bevel-edge termination techniques for silicon carbide (SiC) power devices, such as bevel junction termination extension (JTE), resistive-bevel termination, bevel-assisted JTE, and positive-bevel termination. The proposed bevel-edge termination techniques significantly reduce the chip size for SiC power devices. PiN diodes and test structures were fabricated to quantify the relative performance of the proposed structures. Quantitative comparison in chip size reduction, process schemes, and future research directions is discussed in detail.

Area-Efficient Bevel-Edge Termination Techniques for SiC High-Voltage Devices

Analysis and experimental study of current commutation in an ultra-fast, current limiting, hybrid DC circuit breaker for medium voltage applications is reported in this paper. The hybrid DCCB consists a fast acting 15 kV mechanical switch, a low voltage commutating switch, a single 15 kV Silicon Carbide Emitter Turn Off Thyristor (ETO) device, and a stack of MOVs. The proof-of-concept prototype is able to conduct 45 A normal current and interrupt a maximum of more than 100 A fault current at medium voltage level in less than 4 milliseconds, which is one order of magnitude faster compared to conventional mechanical circuit breakers that typically take 40–100 ms. This paper has presented the operation principle of a hybrid DC circuit breaker and analyzed the current commutation process. Based on the analysis, guidelines are given in the paper to select and design the commutating switch.

Alex Q. Huang

Papers

Experimental study of 650V AlGaN/GaN HEMT short-circuit safe operating area (SCSOA)

Modeling of the High-Frequency Rectifier With 10-kV SiC JBS Diodes in High-Voltage Series Resonant Type DC–DC Converters

Comparison of the state-of-the-art high power IGBTs, GCTs and ETOs

Area-Efficient Bevel-Edge Termination Techniques for SiC High-Voltage Devices

Current commutation in a medium voltage hybrid DC circuit breaker using 15 kV vacuum switch and SiC devices