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This paper deals with the probabilistic design of an end-user microgrid equipped with renewable energy generation and battery energy storage systems. The microgrid is connected to the distribution grid and is able to purchase energy under time of use tariff and to sell energy paid through feed-in tariff. The use of the battery is devoted at (i) increasing the self-consumption and (ii) reducing the cost for energy absorbed by shifting the load demand in the hours of lower energy price. An analytical tool is derived for the optimal sizing of battery energy storage systems accounting for minimization of the total costs incurred by the microgrid owner. The closed form expressions are included within a Monte Carlo simulation so considering uncertainties in load demand and renewable power generation. Though the proposed approach is quite general and can be easily extended to different case studies, the formulation and the results reported in this paper refer to the case of an industrial customer whose demand partially complies with the production of a photovoltaic system.

This paper presents the analysis of multi-harmonic current injection in multi-three phase surface permanent magnet (SPM) machines. An analytical model, extended to a generic harmonic order, is used to describe and determine the no load flux density, the back electromotive force (BEMF) and the electromagnetic torque produced. These are analysed as a function of the permanent magnet span. Based on the BEMF, the harmonics injection technique is adopted to increase the torque in the machine, while keeping the RMS current constant, thus without affecting the Joule losses. In order to understand how the torque is affected by the harmonics injection, considering different PMs rotor span, a comparison with and without injection is presented. It is shown how, thanks to specific harmonics injection, it is possible to reduce the permanent magnet content in SPM machines while generating the same torque performance of a motor with higher PM content, without harmonic injection. The analytical results are finally validated by means of Finite Element Analysis (FEA) considering two different PM rotor span, as a case study, highlighting the benefits of the proposed method.

Low torque ripple of electrical machines is an important requirement for many different applications. The causes of torque fluctuations in squirrel cage asynchronous induction motors might be a challenging task due to the complex phenomena raised by the whole set of rotor bars. This paper proposes an accurate analysis of the torque contributions distinguishing in time-varying, synchronous and asynchronous components. The investigation is performed by adopting a general analytical approach based on a circuital modelling technique for electromagnetic devices. The analysis aims to identify spatial harmonic interactions between stator and rotor magneto-motive forces which generate torque components. The most interesting effects obtained from the analytical investigation are compared and validated against finite element results for the most significant operating points.

This work is showing in detail the flux density behaviour in the stator teeth of a synchronous machine. A 3-phase Surface Permanent Magnet (SPM) motor is considered. These motors are widely employed in applications where high efficiency and power densities are required. This paper aims to analytically demonstrate the asymmetrical distribution of the stator teeth flux density. It is shown that this phenomena is depending on the number of slots per pole and per phase in the machine. Finally, a comparison with Finite Element results is given to validate the effectiveness of the proposed model.

It is well reported that Switched Reluctance Machines typically operate in ‘single-pulse mode’ when rotating at high speed. For such operating mode, the control parameters are the duration of the energizing period along with the advance of the turn-on instant, i.e. advance angle. To maximize the output torque, the energizing period is normally kept equal to half of the electric period, i.e. 180°(elec.), whilst the optimal advance angle is evaluated through time consuming finite-element-based optimization algorithms. In this paper, a simple and novel analytical model is proposed that determines the optimal advance angle in a closed-form analytical expression, directly from the machine geometry. Successful validation against accurate finite element models on two Switched Reluctance prototypes is reported.

The problem of Wi-Fi and LTE coexistence has been significantly debated in the last years, with the emergence of LTE extensions enabling the utilization of unlicensed spectrum for carrier aggregation. Rather than focusing on the problem of resource sharing between the two technologies, in this paper, we study the effects of LTE's structured transmissions on the Wi-Fi random access protocol. We show how the scheduling of periodic LTE transmissions modifies the behavior of 802.11's distributed coordination function (DCF), leading to a degradation of Wi-Fi performance, both in terms of channel utilization efficiency and in terms of channel access fairness. We also discuss the applicability and limitations of a persistent DCF model in analyzing Wi-Fi performance under periodic LTE interference., 4 pages, 2 figures, 2 tables, 13 references, accepted for publication in IEEE Communications Letters

Simultaneous random access attempts from massive machine-type communications (mMTC) devices may severely congest a shared physical random access channel (PRACH) in mobile networks. This paper presents a novel two-phase random access (TPRA) procedure to deal with the congestion caused by mMTC devices accessing the PRACH. During the first phase, the TPRA splits the mMTC devices into smaller groups according to a preamble selected randomly by the devices. Then, in the second phase, each group of devices is assigned with a dedicated channel to complete the random access procedure. The proposed concept allows a base station to adjust the number of dedicated channels in real-time according to the actual network load. We then present an analytical model to estimate the access success probability and the average access delay of the TPRA. Finally, we propose a simple formula to determine the optimal number of random access resources for the second phase of the proposed TPRA. Simulations are carried out to validate the analytical models and to demonstrate the benefits of the TPRA compared to competitive techniques.

The Internet of Vehicle (IoV) network refers to networking technologies that could support highly economical and effective communication channels for interactions between vehicles. The success of IoV relies on efficient vehicle-to-infrastructure (V2I) or vehicle-to-vehicle (V2V) communications. Among all existing communication standards, the IEEE 802.15.4 standard, which comprises a simple physical (PHY) layer and an energy-efficient medium access control, is a promising candidate for IoV networks. In this paper, we propose analytical models for IEEE 802.15.4 nonbeacon-enabled mode for IoV by considering two major features, i.e., non-saturated traffic pattern and large-scale network, in IoV applications. We investigate the performance of IEEE 802.15.4 nonbeacon-enabled mode for IoV. Our study can provide guidelines for vehicles to dynamically adjust the broadcasting rate and achieve a higher probability of success in such communications. 2000-2011 IEEE. Scopus 2-s2.0-84959526149

In this paper the authors introduce a semi-analytical model for the analysis and the design of a Permanent Magnet (PM) tubular linear generator intended for electrical energy generator from sea waves. The mover of the analyzed machine is constituted an air core Halbach array of NdFeB PMs; a two poles, double layer three-phase winding is located in the slots of the stator. The presented model, based on the Fourier transform in the direction of the motion, is able to take into account the end effects due to the finite length of the stators. The presented model has been validated by comparison with a Finite Element analysis.

OpenMP is increasingly being supported by the newest high-end embedded many-core processors. Despite the lack of any notion of real-time execution, the latest specification of OpenMP (v4.0) introduces a tasking model that resembles the way real-time embedded applications are modeled and designed, i.e., as a set of periodic task graphs. This makes OpenMP4 a convenient candidate to be adopted in future real-time systems. However, OpenMP4 incorporates as well features to guarantee backward compatibility with previous versions that limit its practical usability in real-time systems. The most notable example is the distinction between tied and untied tasks. Tied tasks force all parts of a task to be executed on the same thread that started the execution, whereas a suspended untied task is allowed to resume execution on a different thread. Moreover, tied tasks are forbidden to be scheduled in threads in which other non-descendant tied tasks are suspended. As a result, the execution model of tied tasks, which is the default model in OpenMP to simplify the coexistence with legacy constructs, clearly restricts the performance and has serious implications on the response time analysis of OpenMP4 applications, making difficult to adopt it in real-time environments. In this paper, we revisit OpenMP design choices, introducing timing predictability as a new and key metric of interest. Our first results confirm that even if tied tasks can be timing analyzed, the quality of the analysis is much worse than with untied tasks. We thus reason about the benefits of using untied tasks, deriving a response time analysis for this model, and so allowing OpenMP4 untied model to be applied to real-time systems.