M. Fantauzzi

Energy management of electrified mass transit systems with Energy Storage devices

In the paper a methodology for optimal controlling storage devices at the aim of improving the performances of an electrified mass transit system is proposed. A rational procedure is arranged for counteracting the unavoidable stochastic variables involved in the description of the characteristics of this complex system. The core of the control procedure is based upon an optimization technique which should result particularly effective where plant parameters exhibit random behavior. The potentiality of the procedure is shown with reference to the reduction of the network power fluctuations. In this case the control law can be expressed in an analytical way in terms of power mean value over the interest time cycle. Kalman filter is employed to dynamically estimate the mean value of the total required power. A numerical application is reported so to demonstrate the feasibility and the goodness of the proposed control strategy.

Generalized approach to design supercapacitor-based storage devices integrated into urban mass transit systems

In the paper a new design methodology of storage devices for improving the performances of light transportation systems is proposed. A critical analysis is performed with respect to the stochastic variables involved in the description of the behavior of this complex system. Some considerations are performed in order to properly take into account various uncertainties at the aim of optimizing the size of storage devices and satisfying all the technical constraints. The core of the design procedure is a multivariable constrained optimization technique stochastically applied. In the numerical application, for sake of clarity, only the time displacement between two trains is considered as a stochastic variable described as a lognormal distribution function. The probabilistic properties of the output variables of the optimization procedure are then investigated.

Building DC microgrids: Planning of an experimental platform with power hardware in the loop features

DC power distribution systems for building application are gaining interest both in academic and industrial world, due to potential benefits in terms of energy efficiency and capital savings. These benefits are more evident were the end-use loads are natively DC (e.g., computers, solid-state lighting or variable speed drives for electric motors), like in data centers and commercial buildings, but also in houses. When considering the presence of onsite renewable generation, e.g. PV or micro-wind generators, storage systems and electric vehicles, DC-based building microgrids can bring additional benefits, allowing direct coupling of DC loads and DC Distributed energy Resources (DERs). A number of demonstrating installations have been built and operated around the world, and an effort is being made both in USA and Europe to study different aspects involved in the implementation of a DC distribution system (e.g. safety, protection, control) and to develop standards for DC building application. This paper discusses on the planning of an experimental DC microgrid with power hardware in the loop features at the University of Naples Federico II, Dept. of Electr. Engineering and Inf. Technologies. The microgrid consists of a 3-wire DC bus, with positive, negative and neutral poles, with a voltage range of +/-0÷400 V. The system integrates a number of DERs, like PV, Wind and Fuel Cell generators, battery and super capacitor based storage systems, EV chargers, standard loads and smart loads. It will include also a power-hardware-in-the-loop platform with the aim to enable the real time emulation of single components or parts of the microgrid, or of systems and sub-systems interacting with the microgrid, thus realizing a virtual extension of the scale of the system. Technical features and specifications of the power amplifier to be used as power interface of the PHIL platform will be discussed in detail.

A comparison among various optimization control strategies for DC electrified transportation systems

One of the most important issues in DC electrified transportation system management is to perform, as far as possible, optimal operation in terms of economy, quality and reliability. In this paper a voltage control strategy is performed in order to minimize power losses and contemporaneously optimize the power sharing between feeding substations. The problem is formalized as a multiobjective optimization, this allowing to compare various solutions by simply varying the weights in the objective function. The control structure is designed according to a hierarchical architecture. For the traction load characteristics identification, an estimation algorithm is also described. In the last part of the paper a numerical application is presented, highlighting the feasibility and the goodness of the proposed strategies

Energy savings in urban mass transit systems: A probabilistic approach for sizing electric energy storage devices

In the paper an analytical probabilistic methodology is presented at the aim of improving the energy efficiency of light transportation systems. The analytical approach is essentially based upon the classical method of the calculus of variations, which is a powerful methodology for properly describing the isoperimetric problems. Thanks to the possibility of deriving closed form for interest variables, this allows also to handle in a feasible and proper way the stochastic aspects involved in the description of the system under study. The probability density functions of the interest variables can be consequently deduced. The numerical application is developed with respect to the employment of a supercapacitor based energy storage, whereas only the train mass is regarded as a stochastic variable.

Optimal sizing of distributed energy resources in smart microgrids: A mixed integer linear programming formulation

Microgrids can offer various benefits to electricity consumers, but these benefits must be compared with the corresponding investment cost for ensuring financial feasibility. This paper is focused on the problem of optimally sizing, from an economic perspective, the Distributed Energy Resources included in a DC Microgrid, determining the optimal mix of Distributed Generators and Energy Storage Systems, taking also into account the opportunities of Load Management. The proposed procedure is based on Mixed Integer Linear Programming and allows to determine the optimal sizes of Distributed Energy Resources which minimize the Microgrid Total Cost of Ownership, given location and load characteristics. The procedure is formulated as a quite general method that can be used for different microgrid architectures and different generation and storage technologies, although in this paper it is applied to a grid-connected DC microgrid with PV generation and storage system. Results of numerical applications to a case study demonstrate the effectiveness of the proposed sizing procedure.

Cost/benefit analysis of alternative systems for feeding electric energy to ships in port from ashore

The development of maritime transportation has increased the territorial role and the socio-economic relevance of harbors. But, at the same time, it has worsened the environmental impact of the maritime operations on ports and surrounding - often highly inhabited - areas, particularly in the Mediterranean. Since ships at berth need a certain amount of electric energy for hull and hotel services, they must keep their auxiliary engines switched on, inevitably generating exhaust emissions and noise. As a consequence, ports become an important and growing source of pollution and can create relevant risks for the health of the communities living nearby. From the economic point of view, it has been assessed that the costs involved in the shore-side power program can vary widely among ports. In this paper a complete cost benefit analysis will be carried out by keeping into account all costs related to the systems capable of supplying electric energy to ships using systems external to it. In particular, cold ironing, LNG power packs and fuel cells will be evaluated; LNG and fuel cells will be considered both as a fixed source of energy, and as a movable one, when fitted in a barge in order to reach the ship to be powered. Additionally, the results obtained in term of the cost of energy from ashore will be compared with the cost of the energy produced onboard, by keeping into account all charges that compose the real price of the electric energy when using the auxiliary engines onboard ships.