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

Model-Based Design and Simulation of Control Strategies to Maximize the PV Hosting Capacity in Isolated Diesel Networks - Using Solar Short-Term Forecasts for Predictive Control of Diesel Generation

It is widely understood that the Australian way of life is now largely dependent on imported oil and petroleum products. Over 80% of the liquid fuel required to power the 13.8 million passenger vehicles and 4.6 million other service vehicles is derived from foreign sources. This has two major impacts: firstly, it means the responsibility for delivering a secure supply of fuel for domestic Australian transport is in the hands of foreign agents beyond our borders and is therefore not under the control of our government; secondly, there is a cost to the Australian economy and individual Australian transport users, to import these fuel products in increasing volumes to meet domestic demand when local fuel resources and refining capacities are diminishing every year. Hence, there are growing concerns as to whether the reduced energy security and increasing economic cost of this dependence on foreign oil is in the best interests of Australian citizens, particularly when alternative domestic fuel supplies exist.

Why EVs? A Comparison of Alternative Fuels to Help Australia Regain Energy Security

Modern energy can contribute to development in multiple ways while approximately 20% of world's populations do not yet have access to electricity. Solar Home Systems (SHSs) consists of a PV module, a charge controller and a battery supply in the range of 100 Wh/d in Sunbelt countries. The question addressed in this paper is how SHS users approach success of their systems and how these user's views can be integrated in to an existing model of success. Information was obtained on the user's approach to their SHSs by participatory observation, interviews with users and by self-observation undertaken by the lead author while residing under SHS electricity supply conditions. It was found that success of SHSs from the users' point of view is related to the ability of these systems to reduce the burdens of supplying energy services to homesteads. SHSs can alleviate some energy supply burdens, and they can improve living conditions by enabling communication on multiple levels and by addressing convenience and safety concerns. However, SHSs do not contribute to the energy services which are indispensable for survival, nor to the thermal energy services required and desired in dwellings of Sunbelt countries. The elements of three of the four components of our previously proposed model of success have been verified and found to be appropriate, namely the user's self-set goals, their importance and SHSs' success factors. The locally appropriate, and scientifically satisfactory, measurement of the level of achievement of self-set goals, the fourth component of our model of success, remains an interesting area for future research.

Incorporating the user perspective into a proposed model for assessing success of SHS implementations

This paper presents a financial analysis of the estimated cost and benefits of operating a 1.5 kWp grid-connected photovoltaic (PV) system in Perth, Western Australia. The analysis presents results for a typical residential electricity consumer. The paper investigates the feasibility with and without taking Renewable Energy Certificates into account. For the financial analysis, Internal Rate of Return and Payback Periods are used as project evaluation techniques. The results show, that the current PV Rebate Program is insufficient to make PV systems attractive for individuals on purely economic grounds.

New parameters affecting the financial feasibility of grid-connected photovoltaic systems in Western Australia : A discussion

Solar Home Systems (SHSs) are considered an option to supply the basic electricity dependent energy ser-vices to dispersed rural households in unelectrified regions of world’s Sun Belt. Recent experiences in China, India and Bangladesh have consolidated the view that for many applications solar PV is the least cost and the most environmentally preferred option for increasing access to electricity for rural households and small enterprises in these rural and remote areas. In some countries (e.g. Bangladesh) SHSs are considered to be successful but that is not the case in other places. 

There is a need to determine the success of SHSs and to find out what factors influence this success. The objective of this research is to determine the stakeholders understanding on success of SHSs, success factors and the barriers impacting on the success, the indicators of success and how we can quantify the success. 

To address the research objectives a desktop study is carried out to identify successful and failure programs. Based on this desktop research SHS’s stakeholders will be interviewed on their views on success of the pro-grams. 

This paper proposes a framework for assessing the degree of success of SHSs including a consideration of the key factors that contribute to success. In future work feedback from relevant institutions will be incorpo-rated in the process of developing the success framework and the relative importance of the various factors and barriers influencing the SHS’s success. It is proposed to develop a weighting system for these factors that can influence the success of SHS’s installations.

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Martina Calais

Papers

Model-Based Design and Simulation of Control Strategies to Maximize the PV Hosting Capacity in Isolated Diesel Networks - Using Solar Short-Term Forecasts for Predictive Control of Diesel Generation

Why EVs? A Comparison of Alternative Fuels to Help Australia Regain Energy Security

Incorporating the user perspective into a proposed model for assessing success of SHS implementations

New parameters affecting the financial feasibility of grid-connected photovoltaic systems in Western Australia : A discussion

Solar home system's success analysis