Arturo Losi

Constrained least squares methods for parameter tracking of power system steady-state equivalent circuits

The paper deals with the problem of the online parameter identification of power system harmonic equivalent circuits as seen from a bus at which a power electronic device is connected. Recursive constrained least squares methods are considered and models of different order are compared one to another. The proposed online identification procedure is able to identify both equivalent impedances and ambient voltage harmonics and to track their changes during normal operating conditions. Numerical applications evidence the performance of the proposed methods in terms of both steady-state accuracy and responsiveness to changes of the parameter values.

Dispersed generation modeling for object-oriented distribution load flow

The interest in dispersed generation (DG) is world-widely increasing. The connection of small generating units affects the operation of distribution systems and classical modeling and analyzing techniques must be revised. Recently, a novel approach to the distribution load-flow problem has been proposed: the object-oriented (OO) paradigm has been applied both to the system modeling and to the Newton-Raphson solving algorithm in the cases of radial and weakly meshed distribution systems. In this paper, the OO load-flow modeling and algorithm are extended to account for the inclusion of DG. The OO paradigm allows easily introducing accurate models of DG interfacing to the network by various electric devices (synchronous generators, induction machines, power electronics converters). Numerical applications are presented to evidence the features of the algorithm evaluating the effects of DG on the operation of two test systems.

Object-oriented load flow for radial and weakly meshed distribution networks

Object-oriented load flow modeling is presented for both radial and weakly meshed distribution systems. An OO algorithm based on the Newton-Raphson technique is proposed. In the object oriented formulation, some approximations to the full Jacobian matrix are introduced. Consequently, a detailed study of the convergence characteristics of the proposed object oriented algorithm is presented and some sufficient conditions for convergence are derived. Particular attention is paid to the relationship between the electrical parameters of the distribution system and the mathematical parameters that influence the convergence properties of the algorithm. The numerical results obtained in the case of some test systems give evidence of the features of the algorithm.

Simulation and Evaluation of Optimization Problem Solutions in Distributed Energy Management Systems

Deregulation in electricity markets requires fast and robust optimization tools for a secure and efficient operation of the electric power system. In addition, there is the need for integrating and coordinating operational decisions taken by different utilities acting in the same market. Distributed energy management systems (DEMS) may help to fulfill these requirements. The design of DEMS requires detailed simulation results for the evaluation of its performance. To simulate the operation of DEMS from the optimization standpoint, a general purpose distributed optimization software tool, DistOpt, is used, and its capabilities are extended to handle power system problems. The application to the optimal power flow problem is presented.

DistOpt: a software framework for modeling and evaluating optimization problem solutions in distributed environments

We present a flexible software environment, named DistOpt, which is useful in building coarse-grain algorithms for solving optimization problems and simulating the solution of the resulting subproblems in multicomputer systems. It is based on a decomposition-coordination approach, by which large optimization problems can be split into subproblems, which are then easier to solve and can be solved in parallel. The object-oriented methodology on which DistOpt is based, and its graphical user interface, are well suited to modify, interface, and extend existing software modules with minimal impact. DistOpt is a flexible and innovative software environment that can be customized by the user in a short development time.

Integration of demand response into the electricity chain: Challenges, opportunities, and Smart Grid solutions

The concept of Demand Response (DR) generally concerns methodologies, technologies and commercial arrangements that could allow active participation of consumers in the power system operation. The primary aim of DR is thus to overcome the ?traditional? inflexibility of electrical demand and, amongst others, create a new powerful tool to maximize deployment of renewable energy sources as well as provide active network management solutions to help reducing the impact of limited grid capabilities.DR allows consumers to actively participate in power system operation, thus bringing new opportunities in emerging energy markets as well as tangible system benefits. In this sense, DR is considered one of the key enablers of the Smart Grid concept. However, DR also poses a number of challenges, particularly when ?active demand? is connected to the Low Voltage network, thus affecting all the actors involved in the electricity chain.This book presents for the first time a comprehensive view on technical methodologies and architectures, commercial arrangements, and socio-economic and regulatory factors that could facilitate the uptake of DR. The work is developed in a systematic way so as to create a comprehensive picture of challenges, benefits and opportunities involved with DR. The reader will thus be provided with a clear understanding of the complexity deriving from a demand becoming active, as well as with a quantitative assessment of the techno-economic value of the proposed solutions in a Smart Grid context.Many research contributions have appeared in recent years in the field of DR, both in journals and conference proceedings. However, most publications focus on individual aspects of the problem. A systematic treatment of the issues to be tackled to introduce DR in existing electricity grids, involving the extended value chain in terms of technical and commercial aspects, is still missing. Also, several books have recently been published about Smart Grid, in which there is some mention to DR. However, again while DR is seen as a key pillar for the Smart Grid, there is no dedicated, comprehensive and systematic contribution in this respect.

Trade curtailment schemes for the security control of the transmission network in a deregulated environment

Due to deregulation, the electrical power industry is undergoing deep changes, moving towards an open market. Two kinds of parties are active in the new environment: the economical agents (producers, consumers, brokers) and the power system operator, the former interested in power exchanges and their economic value, the latter in bus injections and their threat to the security of the transmission network. The variables used to model the transmission network operation have to be meaningful to the power system operator as well as to the economical parties; the action rules followed by the power system operator to enforce network security have to be carefully designed to be equitable and non-discriminatory. In this paper, a modeling of the power exchanges is proposed in the form of multilateral trades, and some rules for the action of the power system operator are proposed and discussed. The results obtained on a simple study case are discussed.

Load areas in distribution systems

The updated and new monitoring and control functionalities for distribution systems make available a huge amount of information. Indeed, not all the available information is needed to be considered; a significant simplification could be achieved by selecting and treating only the relevant information. With this aim, the concept of Load Area (LA) was recently introduced: a LA is a group of prosumers whose power injection has a similar impact on the distribution grid operating conditions. In the paper, the concept of LA is adopted to select the relevant data needed for the monitoring and control of distribution systems; a possible compact equivalent representation of the relationships between those data is proposed. The results from two test cases confirm the viability of the proposed modeling and highlight a relevant reduction in the amount of information used to describe the network.

Adaptive voltage regulator design for static VAR systems

Abstract The performance of a static VAR system (SVS) strongly depends on the operating conditions of the power system at which the SVS is connected. Since these operating conditions often vary unpredictably, limitations to the performance of a SVS may be derived. To overcome such drawbacks, a new SVS voltage regulation scheme based on the adaptive control theory is proposed. The design of the adaptive voltage regulator is described in detail. The results obtained by numerical simulations show the effectiveness of the proposed control scheme.

Load Area application to radial distribution systems

The evolution of the distribution systems involves updated and new control functionalities; along with them, a huge amount of information is made available and has to be handled. Actually, only part of this information is necessary; a remarkable simplification can be obtained by considering only the relevant information. For this scope, a method was recently proposed based on the concept of Load Area, a group of prosumers whose power injection has a similar impact on the distribution grid operating conditions. In this paper, the method previously developed for a generic distribution system is applied to a radial distribution system to obtain its equivalent radial representation; for it, the computational times for the power-flow problem are shown. The results confirm the viability of the method and the reduction of computational time for the ubiquitous power-flow problem.