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

The use of distributed energy resources is increasingly being pursued as a supplement and an alternative to large conventional central power stations. The specification of a power-electronic interface is subject to requirements related not only to the renewable energy source itself but also to its effects on the power-system operation, especially where the intermittent energy source constitutes a significant part of the total system capacity. In this paper, new trends in power electronics for the integration of wind and photovoltaic (PV) power generators are presented. A review of the appropriate storage-system technology used for the integration of intermittent renewable energy sources is also introduced. Discussions about common and future trends in renewable energy systems based on reliability and maturity of each technology are presented

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Power-Electronic Systems for the Grid Integration of Renewable Energy Sources: A Survey

This review focuses on inverter technologies for connecting photovoltaic (PV) modules to a single-phase grid. The inverters are categorized into four classifications: 1) the number of power processing stages in cascade; 2) the type of power decoupling between the PV module(s) and the single-phase grid; 3) whether they utilizes a transformer (either line or high frequency) or not; and 4) the type of grid-connected power stage. Various inverter topologies are presented, compared, and evaluated against demands, lifetime, component ratings, and cost. Finally, some of the topologies are pointed out as the best candidates for either single PV module or multiple PV module applications.

A review of single-phase grid-connected inverters for photovoltaic modules

The global electrical energy consumption is rising and there is a steady increase of the demand on the power capacity, efficient production, distribution and utilization of energy. The traditional power systems are changing globally, a large number of dispersed generation (DG) units, including both renewable and nonrenewable energy sources such as wind turbines, photovoltaic (PV) generators, fuel cells, small hydro, wave generators, and gas/steam powered combined heat and power stations, are being integrated into power systems at the distribution level. Power electronics, the technology of efficiently processing electric power, play an essential part in the integration of the dispersed generation units for good efficiency and high performance of the power systems. This paper reviews the applications of power electronics in the integration of DG units, in particular, wind power, fuel cells and PV generators.

Power electronics as efficient interface in dispersed power generation systems

Power Electronics as Efficient Interface in Dispersed Power Generation Systems

An overview on developments and a summary of the state-of-the-art of inverter technology in Europe for single-phase grid-connected photovoltaic (PV) systems for power levels up to 5 kW is provided in this paper. The information includes details not only on the topologies commercially available but also on the switching devices employed and the associated switching frequencies, efficiency, price trends and market share. Finally, the paper outlines issues associated with the development of relevant international industry standards affecting PV inverter technology.

Inverters for single-phase grid connected photovoltaic systems-an overview

Inverters for Single-Phase Grid-Connected Photovoltaic Systems

Multilevel voltage source inverters offer several advantages compared to their conventional counterparts. By synthesising the AC output terminal voltage from several levels of voltages, staircase waveforms can be produced, which approach the sinusoidal waveform with low harmonic distortion, thus reducing filter requirements. The need of several sources on the DC side of the converter makes multilevel technology attractive for photovoltaic applications. This paper provides an overview an different multilevel topologies and investigates their suitability for single-phase grid connected photovoltaic systems. Several transformerless photovoltaic systems incorporating multilevel converters are compared regarding issues such as component count and stress, system power rating and the influence of the photovoltaic array earth capacitance.

Multilevel converters for single-phase grid connected photovoltaic systems-an overview

This work presents an overview on recent developments and a summary of the state-of-the-art in inverter technology for single-phase grid connected photovoltaic (PV) systems. The information provided includes details on commercially available European string and module integrated PV inverters, their efficiency, price trends and market share. This review is given for inverters for a power level up to 6 kW. Furthermore, the paper deals with the recent developments of new inverter topologies and PV system concepts and discusses possible future trends.

String and module integrated inverters for single-phase grid connected photovoltaic systems - a review

Various multicarrier pulse width modulation (PWM) techniques suitable for high power converter structures and capable of generating multilevel output voltage waveforms are discussed in this paper. Several interesting characteristics of the multicarrier disposition PWM techniques are revealed. A hybrid multicarrier PWM technique combining the disposition and the phase shifted concepts is considered. The performance of the various techniques with respect to the total harmonic distortion (THD) of the output line voltage in the linear and over-modulation regions is reported. Two distortion factors associated with first- and second-order AC output filtering and for different amplitude modulation indices are presented and used as a measure of comparison for the techniques under consideration.

Martina Calais

Papers

Inverters for single-phase grid connected photovoltaic systems-an overview

Inverters for Single-Phase Grid-Connected Photovoltaic Systems

Multilevel converters for single-phase grid connected photovoltaic systems-an overview

String and module integrated inverters for single-phase grid connected photovoltaic systems - a review

Application specific harmonic performance evaluation of multicarrier PWM techniques