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 voltage source converters are emerging as a new breed of power converter options for high-power applications. The multilevel voltage source converters typically synthesize the staircase voltage wave from several levels of DC capacitor voltages. One of the major limitations of the multilevel converters is the voltage unbalance between different levels. The techniques to balance the voltage between different levels normally involve voltage clamping or capacitor charge control. There are several ways of implementing voltage balance in multilevel converters. Without considering the traditional magnetic coupled converters, this paper presents three recently developed multilevel voltage source converters: (1) diode-clamp, (2) flying-capacitors, and (3) cascaded-inverters with separate DC sources. The operating principle, features, constraints, and potential applications of these converters are discussed.

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Multilevel converters-a new breed of power converters

The aim of this paper is to present a review of current control techniques for three-phase voltage-source pulsewidth modulated converters. Various techniques, different in concept, have been described in two main groups: linear and nonlinear. The first includes proportional integral (stationary and synchronous) and state feedback controllers, and predictive techniques with constant switching frequency. The second comprises bang-bang (hysteresis, delta modulation) controllers and predictive controllers with on-line optimization. New trends in current control-neural networks and fuzzy-logic-based controllers-are discussed, as well. Selected oscillograms accompany the presentation in order to illustrate properties of the described controller groups.

Current control techniques for three-phase voltage-source PWM converters: a survey

The matrix converter is an array of controlled semiconductor switches that connects directly the three-phase source to the three-phase load. This converter has several attractive features that have been investigated in the last two decades. In the last few years, an increase in research work has been observed, bringing this topology closer to the industrial application. This paper presents the state-of-the-art view in the development of this converter, starting with a brief historical review. An important part of the paper is dedicated to a discussion of the most important modulation and control strategies developed recently. Special attention is given to present modern methods developed to solve the commutation problem. Some new arrays of power bidirectional switches integrated in a single module are also presented. Finally, this paper includes some practical issues related to the practical application of this technology, like overvoltage protection, use of filters and ride-through capability.

Matrix converters: a technology review

This paper presents a review of advanced control techniques for microgrids. This paper covers decentralized, distributed, and hierarchical control of grid-connected and islanded microgrids. At first, decentralized control techniques for microgrids are reviewed. Then, the recent developments in the stability analysis of decentralized controlled microgrids are discussed. Finally, hierarchical control for microgrids that mimic the behavior of the mains grid is reviewed.

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Advanced Control Architectures for Intelligent Microgrids—Part I: Decentralized and Hierarchical Control

The authors present results obtained from the testing of candidate 4500-V, 4000-A GTO (gate turn-off) thyristors for use in high-power inverters for electric utility application. Factors contributing to the voltage spike on turn-off are discussed with emphasis on the interpretation of GTO specifications. In order to successfully use large GTO thyristors in high-power switching circuits, it is essential that the device manufacturers' specifications with regard to snubber circuit inductance should be correctly interpreted. Testing of devices from different manufacturers has shown that such specifications can be misleading because there are several mechanisms that contribute to spike voltage on turn-off. It is pointed out that, by properly understanding these mechanisms, it is possible to arrive at a cost-effective, reliable, and manufacturable snubber circuit assembly for 4500-V, 4000-A GTOs. The turn-off voltage spike is one of the main possible causes of GTO failure. The constitution of the spike voltage has been considered in detail with reference to laboratory measurements that allow a unique comparison of devices, obtained from different sources, under comparable full power switching conditions. >

Effect of snubber circuit parameters on the turn-off voltage spike of large GTO thyristors

A motor control system in which an actual torque indication is derived from the motor and compared with a reference, or demand, torque From the difference signal is derived a stator MMF in magnitude and position relative to a reference frame locked to the rotor Orthogonal components of this stator MMF are derived and transformed to stator phase winding drive signals

Induction motor torque control system

SE PRESENTA UN CONTROLADOR DE POTENCIA DE LINEA DE TRANSMISION (50) PARA CONTROLAR EL FLUJO DE POTENCIA ELECTRICA EN UN SISTEMA DE TRANSMISION TRIFASICO DE CORRIENTE ALTERNA (34). EL CONTROLADOR DE LINEA DE POTENCIA (50) INCLUYE UN INVERSOR EN PARALELO (22) CONECTADO A UN INVERSOR EN SERIE (24) A TRAVES DE UN ENLACE (26). EL INVERSOR PARALELO (22) ESTA CONECTADO EN DERIVACION AL SISTEMA DE TRANSMISION (34) A TRAVES DE UN TRANSFORMADOR EN DERIVACION (36). EL INVERSOR EN SERIE (24) ESTA EN CONECTADO EN SERIE CON EL SISTEMA DE TRANSMISION A TRAVES DE UN TRANSFORMAR EN SERIE (38). SE UTILIZA UN CIRCUITO DE CONTROL DE POTENCIA DE LINEA DE TRANSMISION (52) PARA ESPECIFICAR UNA DEMANDA DE POTENCIA DESEADA REAL Y UNA DEMANDA DE POTENCIA REACTIVA PARA EL SISTEMA DE TRANSMISION (34). EL CIRCUITO DE CONTROL DE POTENCIA (52) PROCESA ESTA INFORMACION JUNTO CON UN VECTOR DE TENSION DE LINEA DE TRANSMISION Y UN VECTOR DE CORRIENTE DE LINEA DE TRANSMISION PARA PRODUCIR UNA SENAL DE REFERENCIA DE FUENTE DETENSION QUE SE APLICA AL INVERSOR EN SERIE (24). EN RESPUESTA A LA SENAL DE REFERENCIA DE LA FUENTE DE TENSION, EL INVERSOR EN SERIE PRODUCE UN VECTOR DE TENSION INYECTADO EN EL SISTEMA DE TRANSMISION (34). EL VECTOR DE TENSION INYECTADO FUERZA EL VECTOR DE CORRIENTE DE LINEA DE TRANSMISION HASTA UN VALOR DESEADO QUE SE CORRESPONDE CON LA POTENCIA REAL ESPECIFICADA Y LA DEMANDA DE POTENCIA REACTIVA. DE ESTA FORMA, SE CONSIGUE RAPIDAMENTE LA POTENCIA REAL DESEADA Y EL FLUJO DE POTENCIA REACTIVA SOBRE LA LINEA DE TRANSMISION (34).

Regulador de una linea de transmision que comprende una fuente de tension controlada en continuo, sensible a una demanda de potencia activa asi como a una demanda de potencia reactiva.

Colin D. Schauder

Papers

Effect of snubber circuit parameters on the turn-off voltage spike of large GTO thyristors

Induction motor torque control system

Regulador de una linea de transmision que comprende una fuente de tension controlada en continuo, sensible a una demanda de potencia activa asi como a una demanda de potencia reactiva.

Improved regenerative ac/dc converter

Generator zur Erzeugung einer abgeflachten Wellenform und Pulsbreitenmodulator unter Verwendung derselben