There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

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

Power electronics

The ever increasing progress of high-voltage high-power fully controlled semiconductor technology continues to have a significant impact on the development of advanced power electronic apparatus used to support optimized operations and efficient management of electrical grids, which, in many cases, are fully or partially deregulated networks. Developments advance both the HVDC power transmission and the flexible ac transmission system technologies. In this paper, an overview of the recent advances in the area of voltage-source converter (VSC) HVdc technology is provided. Selected key multilevel converter topologies are presented. Control and modeling methods are discussed. A list of VSC-based HVdc installations worldwide is included. It is confirmed that the continuous development of power electronics presents cost-effective opportunities for the utilities to exploit, and HVdc remains a key technology. In particular, VSC-HVdc can address not only conventional network issues such as bulk power transmission, asynchronous network interconnections, back-to-back ac system linking, and voltage/stability support to mention a few, but also niche markets such as the integration of large-scale renewable energy sources with the grid and most recently large onshore/offshore wind farms.

VSC-Based HVDC Power Transmission Systems: An Overview

Solid-state switch-mode rectification converters have reached a matured level for improving power quality in terms of power-factor correction (PFC), reduced total harmonic distortion at input AC mains and precisely regulated DC output in buck, boost, buck-boost and multilevel modes with unidirectional and bidirectional power flow. This paper deals with a comprehensive review of improved power quality converters (IPQCs) configurations, control approaches, design features, selection of components, other related considerations, and their suitability and selection for specific applications. It is targeted to provide a wide spectrum on the status of IPQC technology to researchers, designers and application engineers working on switched-mode AC-DC converters. A classified list of more than 450 research publications on the state of art of IPQC is also given for a quick reference.

/pdf/a-review-of-single-phase-improved-power-quality-ac-dc-2pm6h4zjxq.pdf

A review of single-phase improved power quality AC-DC converters

Microgrids and Active Distribution Networks offer a potential solution for sustainable, energy-efficient power supply to cater for increasing load growth, supplying power to remote areas, generation of clean power and reduction in emission of greenhouse gases & particulates as per Kyoto protocol.

Microgrids and Active Distribution Networks

The widespread use of distributed generation (DG), which is installed in medium-voltage distribution networks, impacts the future development of modern electrical systems that must evolve towards smart grids. A fundamental topic for smart grids is automatic distributed voltage control (ADVC). The voltage is now regulated at the MV busbar acting on the on-load tap changer of the HV/MV transformer. This method does not guarantee the correct voltage value in the network nodes when the distributed generators deliver their power. In contrast, the ADVC allows control of the voltage acting on a single generator; therefore, a better voltage profile can be obtained. In this paper, an approach based on sensitivity theory is shown to control the node voltages regulating the reactive power injected by the generators. After the theoretical analysis, a numerical example is presented to validate the theory. The proposed voltage regulation method has been developed in collaboration with Enel Distribuzione S.p.A. (the major Italian DSO), and it will be applied in the Smart Grids POI-P3 pilot project, which is financed by the Italian Economic Development Ministry. Before the real field application in the pilot project, a real-time digital simulation has been used to validate the algorithm presented. Moving in this direction, Enel Distribuzione S.p.A. built a new test center in Milan equipped with a real-time digital simulator (from RTDS Technologies).

Automatic Distributed Voltage Control Algorithm in Smart Grids Applications

Currently, the quality of supplied power is important to several customers Power quality (PQ) is a service and many customers are ready to pay for it In the future, distribution system operators could decide, or could be obliged by authorities, to supply their customers with different PQ levels and at different prices A new device that can fulfill this role is the OPEN unified power-quality conditioner (UPQC), composed of a power-electronic series steady-state performancemain unit installed in the medium-voltage/low-voltage (LV) substation, along with several power-electronic shunt units connected close to the end users The series and parallel units do not have a common dc link, so their control strategies are different than traditional UPQC control techniques This device can achieve general improvement in PQ, reducing the most common disturbances for all customers that are supplied by the mains (PQ) by using only the series unit Additional increments in PQ (ie, mains power interruptions), can be provided to the customers who need it (custom power) by the shunt units Therefore, this new solution combines an improvement in PQ for all end users, with a cost reduction for those that need high quality power The proposed solution has been analyzed and described, and a model of a 400-kVA LV grid is considered a test network to evaluate the steady-state performance and functioning limits The results obtained under steady-state conditions justify the configuration chosen and good device performance

A New Proposal for Power Quality and Custom Power Improvement: OPEN UPQC

The spread of the electronics, both for control and power applications, in the realization of apparatuses in low voltage (LV) electrical systems, requires the conversion of the electric power from alternating current to direct current by means of a rectifier stage, generally constituted by a diode bridge. Moreover, modern technologies provide various types of distributed energy resources (DER), constituted by small size generators and storage systems, that generate in direct current, such as photovoltaic arrays, fuel cells, storage, or that need DC section before the interfacing with the AC network (microturbines, variable speed wind generators, flywheels). It can be thought to integrate the various generators, storage systems and DC loads in a local DC distribution network, that is interfaced with public grid by means of one or more inverters. This solution makes easy the islanding operation of the generators. The aim of this work is to analyze a local DC distribution system both with diode and IGBT bridge interface converter in the presence of small scale generation and storage systems. After suitable modeling of the entire system, some simulation results are given.

Proposal of a local DC distribution network with distributed energy resources

An energy integration between photovoltaic (PV) systems and electric vehicles (EVs) can help to overcome problems related to the feasibility of a more sustainable mobility, most of all in urban context. This paper aims to examine the potential and the technical benefits of using PV systems as energy supplier for charging EVs. For this purpose, an urban scale integrated system is presented through a mathematical model that considers the power flows related to the PV generator, the charging station, and electric grid. The most significant result is the evaluation of the self-consumption in order to optimize the interaction between the PV system and charging station for EVs. This analysis has been conducted for different vehicles typologies and different PV installations, giving rise to more than 9000 different cases and allowing to consider the wideness of the self-consumption range for different months.

Urban Scale Photovoltaic Charging Stations for Electric Vehicles

Many different types of electric vehicle (EV) charging technologies are described in literature and implemented in practical applications. This paper presents an overview of the existing and proposed EV charging technologies in terms of converter topologies, power levels, power flow directions and charging control strategies. An overview of the main charging methods is presented as well, particularly the goal is to highlight an effective and fast charging technique for lithium ions batteries concerning prolonging cell cycle life and retaining high charging efficiency. Once presented the main important aspects of charging technologies and strategies, in the last part of this paper, through the use of genetic algorithm, the optimal size of the charging systems is estimated and, on the base of a sensitive analysis, the possible future trends in this field are finally valued.

/pdf/electric-vehicles-charging-technology-review-and-optimal-1oewmefr4x.pdf

Morris Brenna

Papers

Automatic Distributed Voltage Control Algorithm in Smart Grids Applications

A New Proposal for Power Quality and Custom Power Improvement: OPEN UPQC

Proposal of a local DC distribution network with distributed energy resources

Urban Scale Photovoltaic Charging Stations for Electric Vehicles

Electric Vehicles Charging Technology Review and Optimal Size Estimation