Concettina Buccella

Smart Grid Technologies: Communication Technologies and Standards

For 100 years, there has been no change in the basic structure of the electrical power grid. Experiences have shown that the hierarchical, centrally controlled grid of the 20th Century is ill-suited to the needs of the 21st Century. To address the challenges of the existing power grid, the new concept of smart grid has emerged. The smart grid can be considered as a modern electric power grid infrastructure for enhanced efficiency and reliability through automated control, high-power converters, modern communications infrastructure, sensing and metering technologies, and modern energy management techniques based on the optimization of demand, energy and network availability, and so on. While current power systems are based on a solid information and communication infrastructure, the new smart grid needs a different and much more complex one, as its dimension is much larger. This paper addresses critical issues on smart grid technologies primarily in terms of information and communication technology (ICT) issues and opportunities. The main objective of this paper is to provide a contemporary look at the current state of the art in smart grid communications as well as to discuss the still-open research issues in this field. It is expected that this paper will provide a better understanding of the technologies, potential advantages and research challenges of the smart grid and provoke interest among the research community to further explore this promising research area.

A Survey on Smart Grid Potential Applications and Communication Requirements

Information and communication technologies (ICT) represent a fundamental element in the growth and performance of smart grids. A sophisticated, reliable and fast communication infrastructure is, in fact, necessary for the connection among the huge amount of distributed elements, such as generators, substations, energy storage systems and users, enabling a real time exchange of data and information necessary for the management of the system and for ensuring improvements in terms of efficiency, reliability, flexibility and investment return for all those involved in a smart grid: producers, operators and customers. This paper overviews the issues related to the smart grid architecture from the perspective of potential applications and the communications requirements needed for ensuring performance, flexible operation, reliability and economics.

Digital Control of Power Converters—A Survey

Power converters offer a high capability to efficiently manage electrical energy flows. Until a few years ago, their primary use was in supplying motors in industrial applications and in electric traction systems. Nowadays, in addition to those fields they are employed in a very wide range of low, medium, and high power applications including residential applications, renewable energy systems, distributed generation, and automotive. Since digital control represents a key element of modern power converters, this paper presents a review on digital devices [microcontrollers, Field Programmable Gate Arrays (FPGA)], hardware and software design techniques as well as implementation issues useful for designing modern high-performance power converters.

A Review of Architectures and Concepts for Intelligence in Future Electric Energy Systems

Renewable energy sources are one key enabler to decrease greenhouse gas emissions and to cope with the anthropogenic climate change. Their intermittent behavior and limited storage capabilities present a new challenge to power system operators to maintain power quality and reliability. Additional technical complexity arises from the large number of small distributed generation units and their allocation within the power system. Market liberalization and changing regulatory framework lead to additional organizational complexity. As a result, the design and operation of the future electric energy system have to be redefined. Sophisticated information and communication architectures, automation concepts, and control approaches are necessary in order to manage the higher complexity of so-called smart grids. This paper provides an overview of the state of the art and recent developments enabling higher intelligence in future smart grids. The integration of renewable sources and storage systems into the power grids is analyzed. Energy management and demand response methods and important automation paradigms and domain standards are also reviewed.

Smart Grid and Smart Homes: Key Players and Pilot Projects

The smart grid (SG) is envisioned as providing a communications network for the energy industry, similar to that which the Internet now provides for business and personal communications. The SG offers new business opportunities for different kind of industries, such as smart-meter vendors, electric utilities, and telecom operators from all around the world. This article deals with issues related to smart homes (SHs) and smart metering, which are key elements in the new SG. It introduces the key players in this field and points out the research challenges. Finally, SG pilot projects and field tests from all around the world and the deployment of advance metering infrastructure projects in North America, Asia, and Europe are summarized.

Analytical Method for Pattern Generation in Five-Level Cascaded H-Bridge Inverter Using Selective Harmonic Elimination

This paper proposes an analytical procedure for computation of all pairs of valid switching angles used in pattern generation in five-level H-bridge cascaded inverters. The proposed procedure eliminates harmonic components from inverter output voltage and, for each harmonic, returns the exact boundaries of all valid modulation index intervals. Due to its simple mathematical formulation, it can be easily implemented in real time using a digital signal processor or a field-programmable gate array. In this paper, after a detailed description of the method, simulation and experimental results demonstrate the high quality of achievable results.

Prediction of Temperature Increase in Human Eyes Due to RF Sources

A numerical study is proposed to investigate the effects of different RF sources on the specific absorption rate (SAR) and maximum temperature increase in the human eye at different frequencies. In particular, a new model of the human head is presented and compared with an anatomical model of the visible human. The high resolution (0.5 mm) of the proposed model allows to consider more eye tissues than previous studies distinguishing the sclera from the retina and choroid. New values of blood perfusion and metabolic rate of these tissues are derived. A plane-wave field is considered as far-field exposure, while realistic models of mobile phone and dipole antennas are used as primary sources for near-field exposure. The obtained results show that the distributions of the SAR and temperature increase depend on the frequency, position, and kind of sources. Finally, attention is paid to the maximum temperature increase in the lens for the SAR values prescribed by the Commission on Non-Ionizing Radiation Protection. To this aim, a scaling approach is proposed, and significant values of temperature increase are found (about C for general public exposure and about 1.5 degC for occupational exposure) for the most critical cases of near-field exposures.

Detection and localization of defects in shielded cables by time-domain measurements with UWB pulse injection and clean algorithm postprocessing

An experimental procedure to detect and localize defects in shielded cables is presented. First, time-domain measurements are carried out by injecting a short rise time pulse in the input section of the shielded cable. Then, the clean algorithm is applied to the measurement results to identify possible damages in the cable line. The localization of the cable section with defects is finally obtained in a very simple way due to the adopted method of measurement in time domain using a ultrawide-band pulser with a very fast rise time. The proposed method is validated by detecting and localizing known defects purposely introduced in test cables.

A Coupled Electrothermal Model for Planar Transformer Temperature Distribution Computation

Planar transformers (PTs) are of particular interest in switching mode power supplies and, more generally, in power converter design. They provide enhanced performance, compactness, ruggedness, constant quality, and low cost. Their optimum performance can, however, only be obtained through an accurate design which accounts for both electromagnetic and thermal problems. For that reason, this paper proposes a new combined and accurate electrothermal model for PT design. First, the electrical model based on the eddy current equation is defined. A finite element method is applied to obtain the current density distributions. Second, a 1-D thermal model based on Greens function approach is developed to calculate the temperature distribution in the device. The results obtained using the proposed coupled model are compared with measurements. The comparison indicates a relatively good correlation between the results of our model and experimental data. An excellent agreement is however observed at early times.

Observer-Based Control of LLC DC/DC Resonant Converter Using Extended Describing Functions

This paper presents theoretical and practical results about dynamic analysis, frequency response, and control of a LLC resonant dc/dc converter operating under wide input voltage and load variations. A nonlinear model for the LLC resonant converter was developed using the extended describing function method; then, based on the derived model, a nonlinear observer-based controller was designed and implemented with a digital signal processor. Transient responses obtained under input voltage and output load variations show that the proposed controller is capable to stabilize the output effectively. Experimental results prove the superiority of the proposed observer-based controller over a conventional PID controller.