F. Mottola

Optimal Integration of Distributed Energy Storage Devices in Smart Grids

Energy storage is traditionally well established in the form of large scale pumped-hydro systems, but nowadays is finding increased attraction in medium and smaller scale systems. Such expansion is entirely complementary to the forecasted wider integration of intermittent renewable resources in future electrical distribution systems (Smart Grids). This paper is intended to offer a useful tool for analyzing potential advantages of distributed energy storages in Smart Grids with reference to both different possible conceivable regulatory schemes and services to be provided. The Smart Grid Operator is assumed to have the ownership and operation of the energy storage systems, and a new cost-based optimization strategy for their optimal placement, sizing and control is proposed. The need to quantify benefits of both the Smart Grid where the energy storage devices are included and the external interconnected grid is explored. Numerical applications to a Medium Voltage test Smart Grid show the advantages of using storage systems related to different options in terms of incentives and services to be provided.

An Exact Closed-Form Solution for Lightning-Induced Overvoltages Calculations

We present the evaluation of the induced voltages in a lossless single transmission line, located at a given height over an infinite conductivity ground plane, and exited by an external field due to a step current moving along a vertical channel. This is a classic topic of the theory of lightning-induced voltages on power lines. The technical literature related to this topic has performed a significant effort; however, only approximated formulas have been obtained so far. In this paper, we derive the exact closed-form solution. We also will discuss, evaluate, and compare the approximated formulas with reference to the proposed exact one, thus contributing to clarifying a matter that still is debated and sometimes misleading, as we will show in the paper. We furthermore recall that the examined lightning-induced voltages model is fundamental for the IEEE standard 1410, a guide for improving the lightning performance of power distribution line.

A review of single-objective optimization models for plug-in vehicles operation in smart grids part I: Theoretical aspects

Plug-in Electric Vehicles (PEVs) could become remarkable resources for improving quality and reliability of future grids, if adequate control of their onboard storage systems is provided. Hence, the problem of PEVs optimal control strategies is a crucial topic of research in modern power system operation. This is particularly true in the Smart Grid (SG) context, where the presence of bi-directional communications among distributed energy resources and customers makes it possible to obtain an optimized operation of the grid. In this paper a critical overview of some of the most significant single-objective optimization methodologies proposed for the optimal operation of PEVs in electrical distribution networks is presented in order to verify their feasibility in the context of SGs. These methodologies allow the performance of several services, which aim to meet both needs internal to the SG (for example, the losses minimization or the minimization of average voltage deviations) and external to it (for example, ancillary services to the electrical system to whom the SG is interconnected). This paper reports the theoretical aspects of the optimization models, whereas the companion paper “Part II: numerical applications to vehicle fleets” proposes the results of the analysed models.

A review of single-objective optimization models for plug-in vehicles operation in Smart Grids Part II: Numerical applications to vehicles fleets

This is the companion paper to “Part I: theoretical aspects”. Part I reviews and critically analyses some of the most significant single-objective optimization methodologies proposed for the optimal operation of plug-in electric vehicles (PEVs) operating in Smart Grids. This Part II applies the models presented in Part I to a low voltage test Smart Grid. Analysis of the results highlights the behavior of the considered control strategies in terms of their compliance with both the objective functions and constraints. In the final part of this paper the results are summarized and compared in order to give an useful tool for understanding the more appropriate objectives and constraints to be taken into account for an optimal control of the Smart Grids.

Optimal operation of electrical energy storage systems for industrial applications

Electrical energy storage systems can provide several benefits along the entire value chain of the electrical system. In this paper attention is paid to the end user point of view, with particular reference to industrial customers. An optimal operating strategy is proposed for energy storage systems with the aim of reducing the electricity bill costs sustained by an industrial customer and contemporaneously satisfying technical constraints for the maximization of the storage system efficiency and life cycle. The proposal, which is developed in this paper by means of computer simulations, will be realized in an industrial facility located in the South of Italy in the frame of the GREAT project, a research plan aimed at developing advanced methods and tools for micro-grid applications.

A Multi-Objective Approach for Microgrid Scheduling

This paper details an approach for the optimal scheduling of microgrids, including different distributed resources such as datacenters, electric vehicles, and distributed generation units. Management of both loads and generation systems is considered to be a strategic approach to optimally operate the grid. At this purpose, a multi-objective strategy was formulated, including several objectives that are considered essential for the efficient grid operation. Numerical simulations were performed to test the effectiveness of the proposed approach and the results were compared with those obtained through uncontrolled scenarios.

Single-objective optimal scheduling of a low voltage microgrid: A minimum-cost strategy with peak shaving issues

Distributed generation units in microgrids are typically inadequate to meet the total loads demand during the peak hours, whereas a surplus of energy can be available during the hours of the day characterized by low demand. On the other hand, the foreseeable large use of plug-in electric vehicles storage systems could enable to modify the microgrid daily load demand; plug-in electric vehicles batteries, in fact, can have the multiple role of loads and energy sources. On the basis of the above considerations, this paper focuses on the economical scheduling of electric vehicles powers by proposing a single-objective optimization model that minimizes the total amount of daily cost suffered for the energy imported from the upstream network. The model includes also a constraint on the active power at the interconnection bus of the microgrid, thus enabling the peak shaving service. The effectiveness of the single-objective strategy is demonstrated with numerical applications to a low voltage test microgrid.

Lightning induced voltages on power lines: a new statistical approach

The indirect lightning performances of distribution lines are related to two main aspects: the induced overvoltages calculation and the statistical treatment of the obtained results. In the paper, both the aspects are treated. In particular, an exact closed form solution will be used to calculate the induced overvoltage, and the consequent statistical treatment will be carried out taking into account all the random parameter involved in the analysis, which is a more complete approach with respect to the usual one adopted in literature.

Battery Energy Storage Sizing When Time of Use Pricing Is Applied

Battery energy storage systems (BESSs) are considered a key device to be introduced to actuate the smart grid paradigm. However, the most critical aspect related to the use of such device is its economic feasibility as it is a still developing technology characterized by high costs and limited life duration. Particularly, the sizing of BESSs must be performed in an optimized way in order to maximize the benefits related to their use. This paper presents a simple and quick closed form procedure for the sizing of BESSs in residential and industrial applications when time-of-use tariff schemes are applied. A sensitivity analysis is also performed to consider different perspectives in terms of life span and future costs.

Optimal design of combined AC-DC transmission lines

In the paper an optimal procedure is proposed in order to face with power upgrading of transmission line of a double circuit line. The methodology is quite general, allowing to take properly into account all the technical constraints which have to be satisfied for a line acceptable behaviour. This procedure is based upon an optimal power flow which maximizes the power line capability, ensuring that the original line structure is not altered. The results of the optimal power flow could be of great interest being a powerful mean for the designers aligned with the recent tendency towards the exploitation of the existing structures, avoiding the construction of new transmission lines. In the last part of the paper relevant numerical applications are reported in order to demonstrate the feasibility of the proposed approach.