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In this paper, we address the problem of the probabilistic steady-state analysis of an electrical distribution system that includes wind and photovoltaic power plants. We propose a new method that takes into account the uncertainties due to the time variations of power load demands and the random nature of solar and wind energy. The new method extends a probabilistic approach proposed in the relevant literature for balanced electrical distribution systems to unbalanced electrical distribution systems, and it also takes into account the correlation among the random input variables. The method is based on Taguchi's orthogonal arrays. Numerical applications based on an IEEE test system provide evidence of the probabilistic performance of the proposed approach. The results obtained with the proposed method are compared with the results obtained using non-linear Monte Carlo simulation and the Point Estimate Method. [ABSTRACT FROM AUTHOR]

Recently, there has been a growing interest in reducing the number or replacing the hydraulic/pneumatic actuators utilised on aircraft with electric actuators coupled to mechanical gears, which would improve the reliability and performance. This is involved in the concept of more electric aircraft. The electrification of actuators would affect the primary and secondary flight controls, as well as the movement of flight surfaces, retraction of the landing gear, and steering of the nose landing gear, which is also considered in this study. This study considers the design of a multiphase permanent‐magnet (PM) motor to be utilised for the electric steering of a commercial aircraft nose landing gear. This multiphase motor would make it possible to achieve a highly reliable actuator and, coupled with a harmonic drive, avoid the use of a multi‐motor configuration. Moreover, a multiphase motor would increase the power density and efficiency of the actuator, through improving the torque ripple. The performance variation due to temperature swings is considered, and a design procedure for the PM motor is described using the worse operation case for the electric actuator. The adequate performance of the designed motor and actuator is demonstrated by means of a finite element analysis. [ABSTRACT FROM AUTHOR]

The power extracted from PV arrays is usually maximized using maximum power point tracking algorithms. One of the most widely used techniques is the perturb & observe algorithm, which periodically perturbs the operating point of the PV array, sometime with an adaptive perturbation step, and compares the PV power before and after the perturbation. This paper analyses the most suitable perturbation step to optimize maximum power point tracking performance and suggests a design criterion to select the parameters of the controller. Using this proposed adaptive step, the MPPT perturb & observe algorithm achieves an excellent dynamic response by adapting the perturbation step to the actual operating conditions of the PV array. The proposed algorithm has been validated and tested in a laboratory using a dual input inductor push-pull converter. This particular converter topology is an efficient interface to boost the low voltage of PV arrays and effectively control the power flow when input or output voltages are variable. The experimental results have proved the superiority of the proposed algorithm in comparison of traditional perturb & observe and incremental conductance techniques. [ABSTRACT FROM AUTHOR]

In electric vehicles, currents with high-frequency ripples flow in the power cabling system due to the switching operation of power converters. Inside the cables, a strong coupling between the thermal and electromagnetic phenomena exists, since the temperature and Alternating Current (AC) density distributions in the strands affect each other. Due to the different time scales of magnetic and heat flow problems, the computational cost of Finite Element Method (FEM) numeric solvers can be excessive. This paper derives a simple analytical model to calculate the total losses of a multi-stranded cable carrying a Direct Current (DC) affected by a high-frequency ripple. The expression of the equivalent AC cable resistance at a generic frequency and temperature is derived from the general treatment of multi-stranded multi-layer windings. When employed to predict the temperature evolution in the cable, the analytical model prevents the use of complex FEM models in which multiple heat flow and magnetic simulations have to be run iteratively. The results obtained for the heating curve of a 35 mm2 stranded cable show that the derived model matches the output of the coupled FEM simulation with an error below 1%, whereas the simple DC loss model of the cable gives an error of 2.4%. While yielding high accuracy, the proposed model significantly reduces the computational burden of the thermal simulation by a factor of four with respect to the complete FEM routine. [ABSTRACT FROM AUTHOR]

The electricity market and environmental concerns, with wide utilization of renewable sources, have improved the diffusion of distributed generation units changing the operations of distribution grids from passive networks to microgrids. A microgrid includes a cluster of electrical loads, energy storage devices and microsources, which provide both power and heat to their local area. A microgrid has usually one connection point to the utility grid through power electronic converters placed at customers' sites. This paper analyses a Reconfigurable Integrated Converter (RIC) used for a domestic microgrid with inputs from the AC mains and photovoltaic arrays, and two DC outputs at different voltage levels. A RIC as a dual-boost DC-DC converter is proposed, modelled and analysed in the paper. The advantages of such a topology in comparison with traditional boost converters are outlined. Reported simulations results give evidence on the controllability of this converter and the capability of achieving the desired voltage outputs with reduced ripple. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries are the core equipment of electric vehicles (EVs) and they are expected to spread out through smart power systems [e.g., smart grids (SGs)]. Batteries are subject to degradation over time, which gradually reduces the supplied voltage and capacity until they fail to meet minimum requirements. Battery prognostic is mandatory in order to keep track of the degradation over time and to schedule maintenance and replacement before failures, which can cause severe damages and harmful effects on EVs and SGs. However, the estimation of the state of health and the remaining useful life of batteries is not trivial, since neither can be directly measured. In this article, multiple linear regression models are developed within deterministic and probabilistic frameworks to predict the SoH of batteries based on historical charge/discharge data. The models exploit informative data collected for the battery under investigation and stored data of batteries characterized by accelerated degradation tests. Numerical experiments based on actual data are presented to validate the performance of the proposal. [ABSTRACT FROM AUTHOR]

Recently, Andreotti et al. (2015) have presented a new tool for lightning induced voltage calculations on power networks. This tool, named Circuit for Lightning Induced Voltage (CiLIV), has been initially developed for straight and vertical lightning channels; afterwards, the tool has been extended to evaluate induced voltages produced by tortuous lightning channels. However, in the aforementioned studies, only simple power network configurations have been examined. Therefore, aim of this paper is twofold: 1) to apply CiLIV to more complex network configurations, that is, complex networks equipped with transformers, surge arresters, groundings, and so on; 2) to investigate the effects of channel tortuosity on the voltages induced in these complex networks. [ABSTRACT FROM PUBLISHER]

The growing interest in the use of energy storage systems to improve the performance of tramways has prompted the development of control techniques and optimal storage devices, displacement, and sizing to obtain the maximum profit and reduce the total installation cost. Recently, the rapid diffusion of renewable energy generation from photovoltaic panels has also created a large interest in coupling renewable energy and storage units. This study analyzed the integration of a photovoltaic power plant, supercapacitor energy storage system, and railway power system. Random optimization was used to verify the feasibility of this integration in a real tramway electric system operating in the city of Naples, and the benefits and total cost of this integration were evaluated. [ABSTRACT FROM AUTHOR]

This paper presents a DC side oriented diagnostic method for photovoltaic fields which operates on string currents previously supplied by an appropriate monitoring system. The relevance of the work relies on the definition of an effective and reliable day-by-day target for the power that every string of the field should have produced. The procedure is carried out by comparing the instantaneous power produced by all solar strings having the same orientation and by attributing, as producible power for all of them, the maximum value. As figure of merit, the difference between the maximum allowed energy production (evaluated as the integral of the power during a defined time interval) and the energy actually produced by the strings is defined. Such a definition accounts for both weather and irradiance conditions, without needing additional sensors. The reliability of the approach was experimentally verified by analyzing the performance of two medium size solar fields that were monitored over a period of four years. Results allowed quantifying energy losses attributable to underperforming solar strings and precisely locating their position in the field. [ABSTRACT FROM AUTHOR]

Nowadays, the reduction of aircraft emissions is one of the industrial targets with a horizon time until 2050. The recent progresses in electrical drives give the opportunity to modify the aircraft propulsion based on thermal engine or gas turbine to a hybrid/full electric one. Some problems must be solved: weight, reliability, and the choice of the best configuration for the electric propulsion. One of the most important aspects to solve is the thermal behavior of power converters and electric motors. This paper proposes an optimization procedure for the design of surface permanent magnet motors used for the aircraft propulsion: the aim of the paper is to investigate the possibility of cooling the motor with only the air flow due to the aircraft speed. The optimization procedure has been solved with the integration of analytical model and finite element analysis and using a differential evolution algorithm. [ABSTRACT FROM AUTHOR]

Despite the yearly rise in the market quota of full electric vehicles, the main limitations on the deployment of electric vehicles are the real performances of the battery storage during operation. In this study, the authors focus on hybrid electrical storage systems composed of lead acid batteries and supercapacitors. Two different coupling methods are investigated: (i) the direct parallel coupling of the two storage devices and (ii) coupling by means of a step‐up converter between the supercapacitor bank and direct current (DC) link of the entire power‐train, where lead acid batteries are also connected. A specific control strategy is proposed and implemented in the step‐up converter to guarantee the correct power management of the power train and in particular: (i) to save the power request to the lead acid battery pack, (ii) maintain an adequate state of charge of the supercapacitor bank, and (iii) guarantee an adequate voltage level on the DC link. A prototype of the hybrid battery, integrating the proposed control technique, was realised and tested on a real forklift. The performances of the entire power‐train were experimentally measured in a warehouse test cycle emulating a typical daily working cycle. [ABSTRACT FROM AUTHOR]

The aim of the paper is the study of an optimal integration of a supercapacitor-based storage system and inductive power transfer system for the free-catenary operation of a tramway. Starting from the definition of the topology of inductive power transfer system, we propose and analyze a design procedure for the pads of the inductive power system. In the second part of the paper, an optimal integration strategy for the correct size of on-board supercapacitors and the power of the inductive energy transfer are proposed. The results obtained by means of numerical simulations are discussed. [ABSTRACT FROM AUTHOR]

Despite the yearly rise in the market quota of full electric vehicles, the main limitations on the deployment of electric vehicles are the real performances of the battery storage during operation. In this study, the authors focus on hybrid electrical storage systems composed of lead acid batteries and supercapacitors. Two different coupling methods are investigated: (i) the direct parallel coupling of the two storage devices and (ii) coupling by means of a step-up converter between the supercapacitor bank and direct current (DC) link of the entire power-train, where lead acid batteries are also connected. A specific control strategy is proposed and implemented in the step-up converter to guarantee the correct power management of the power train and in particular: (i) to save the power request to the lead acid battery pack, (ii) maintain an adequate state of charge of the supercapacitor bank, and (iii) guarantee an adequate voltage level on the DC link. A prototype of the hybrid battery, integrating the proposed control technique, was realised and tested on a real forklift. The performances of the entire power-train were experimentally measured in a warehouse test cycle emulating a typical daily working cycle. [ABSTRACT FROM AUTHOR]

Summary: Historically, asymmetrical windings in electrical machines have been rarely used and only for specified needs, because the adoption of symmetrical configurations has always been considered the only solution during the design stage of electrical machines. The aim of this work is to demonstrate with several examples that the use of slightly asymmetrical windings can be a reasonable choice and, in certain cases, a favorable option during the machine design stage, allowing the possibility of selecting a wider range of slot/pole number combinations, without affecting the performances of the machines. More in detail, an interior permanent magnet synchronous machine equipped with a symmetrical 3‐phase winding has been considered as a reference structure. Then, this geometry has been adequately modified in other 3 models to equip asymmetrical windings on each of the modified structures. Afterwards, the performances have been compared in generated torque, magnetic forces, magnetomotive force harmonic content, cogging torque, and iron core losses. This comparison has led to promising results, obtaining in some cases even a reduction of power losses, cogging torque, and harmonic content. [ABSTRACT FROM AUTHOR]

The aim of this study is to present a new, accurate, and user‐friendly software procedure for the analysis and rapid design of rotating induction machine windings, considering both the electric and the magnetic specifications of the machine itself. This procedure is a valid aid for quick first stage design without the necessity of using finite element method (FEM)‐based design procedures. FEM can be used in a second design phase in order to refine the first stage results. The design procedure is hereafter outlined and some examples show its capability. [ABSTRACT FROM AUTHOR]

In this study, the design optimisation of a synchronous reluctance machine for light electric vehicles is proposed, to increase efficiency and reduce torque ripples. The existing machine was structurally optimised, using dedicated genetic algorithms, replacing only the rotor and keeping the stator and it's winding untouched. Starting from the original design of the rotor implemented in Flux2D, a finite element analysis software, and the genetic algorithm optimisation implemented in Matlab, a complex co‐simulation was accomplished to obtain a rotor architecture that increases the machine's performances and decreases the torque ripples. By this, performing rotor skewing is not needed any more, hence the torque loss due to it was cancelled. The optimised rotor design increases the machine performances by higher mean torque, no skewing, <8% torque ripples, higher efficiency and better inductance characteristics. Comparative results obtained both in simulations and experimental measurements prove positive outcomes of the optimisation process. [ABSTRACT FROM AUTHOR]

This paper presents a new optimization problem for the design of distribution transformers under the strict requirements on energy efficiency imposed by modern standards and directives. The proposed methodology is devoted to the minimization of the total owning cost of the transformer while meeting a set of constraints that includes all the phenomena implied in the transformer operation. In particular, both electromagnetic and thermal aspects are considered and their relationships with electrical and geometrical variables are accurately detailed. Furthermore, the power losses in both core and windings are accurately derived and the limitations imposed by the standards are taken into account by imposing proper constraints. The generality of the proposal allows considering different technological solutions in material used for the core. The results proposed in the numerical applications showed the effectiveness of the proposed procedure and permitted highlighting the feasibility of different solutions. [ABSTRACT FROM AUTHOR]

The ability to forecast the production of power by photovoltaic (PV) systems accurately and reliably is of major importance for the appropriate management of future electrical distribution systems. Several forecasting methods have been proposed in the relevant literature, and many indices have been used to quantify the quality of the forecasts. The methods can provide either deterministic or probabilistic forecasts; the latter seem to be the most appropriate to take into account the unavoidable uncertainties of PV power production. Similarly, indices were used to quantify the quality of both deterministic and probabilistic forecasting methods, but they usually do not account for the economic consequences of forecasting errors. In this paper, two advanced probabilistic forecasting approaches based on the Bayesian inference method are applied to the short-term forecasting of PV power production. Moreover, new probabilistic indices were proposed with the aim of comparing the probabilistic forecasting methods in such way that the value of the forecast is not included only by the users in their decision-making process; instead, it is partially anticipated by the forecasters in their quality-assessment process. Numerical applications also are presented to provide evidence of the performances of the Bayesianbased approaches and the probabilistic indices that were considered. [ABSTRACT FROM AUTHOR]

This study deals with direct torque control (DTC) of induction motor drives when a multilevel inverter is involved. The proposed control technique is finalised to reduce the amplitude of torque oscillations and to improve the motor dynamic response regardless of operating speed conditions while assuring a satisfactory input current distortion. This is achieved by using a special look-up-table built with a novel approach. The control itself is based on the application in each sampling interval of one or two voltage vectors suitably selected, in order to ensure low electromagnetic torque ripple in steady-state operations and fast dynamic behaviour in transient operations. In the algorithm, the converter voltage vectors selection is carried out by using a novel look-up table whose entry points are computed by means of a specialised relation, starting from the outputs of multilevel hysteresis controllers. The suggested method, suitable for a generic multilevel inverter, is detailed for a neutral point clamped three-level inverter. The proposed algorithm is validated by several numerical results, and compared with a DTC algorithm based on a traditional three-speed range look-up tables. Finally, some experimental results, obtained with a scale laboratory setup, are shown, discussed and compared with the numerical ones. [ABSTRACT FROM AUTHOR]

This study deals with direct torque control (DTC) of induction motor drives when a multilevel inverter is involved. The proposed control technique is finalised to reduce the amplitude of torque oscillations and to improve the motor dynamic response regardless of operating speed conditions while assuring a satisfactory input current distortion. This is achieved by using a special look‐up‐table built with a novel approach. The control itself is based on the application in each sampling interval of one or two voltage vectors suitably selected, in order to ensure low electromagnetic torque ripple in steady‐state operations and fast dynamic behaviour in transient operations. In the algorithm, the converter voltage vectors selection is carried out by using a novel look‐up table whose entry points are computed by means of a specialised relation, starting from the outputs of multilevel hysteresis controllers. The suggested method, suitable for a generic multilevel inverter, is detailed for a neutral point clamped three‐level inverter. The proposed algorithm is validated by several numerical results, and compared with a DTC algorithm based on a traditional three‐speed range look‐up tables. Finally, some experimental results, obtained with a scale laboratory setup, are shown, discussed and compared with the numerical ones. [ABSTRACT FROM AUTHOR]

Ultra-fast charging infrastructures are gaining increasing interest thanks to their ability to reduce the charging-time of plug-in electric vehicles to values comparable to those of the refueling of traditional vehicles in gas stations. This is a consequence of the increasing rated power of both on-board batteries and charging equipment. On the other hand, the increased values of charging power have led to an increased impact on the power distribution networks, particularly in terms of line currents and bus voltages. In presence of large penetration of ultra-fast charging devices, in fact, both currents and voltages are affected by larger variations whose values can exceed the admissible limits imposed by the technical constraints and by the levels of quality of service. In order to reduce the impact of this typology of vehicles' charging on the electrical infrastructure, in this paper a methodology is presented which allows managing a microgrid in presence of ultra-fast charging stations by satisfying the constraints of the grid, while preserving the expected short charging-time for electric vehicles. To this end, a proper optimal strategy is proposed which coordinates the demands of electric vehicles and of the other loads of the microgrid with the power provided by the renewable energy generation resources. The proposed approach aims to optimally control the active and reactive power of charging stations and renewable generation units and to minimize the charging time of a fleet of plug-in electric vehicles while satisfying the constraints on the technical aspects and on the quality of service. The proposed approach has been tested on a test system and the results, proposed in the last part of the paper, demonstrate the feasibility of the proposed approach. [ABSTRACT FROM AUTHOR]

This paper focuses on the interdisciplinary research on the design of a smart gateway for managing the dynamic error code testing collected and generated by the Electronic Control Unit (ECU) from the automotive industry. The techniques used to exchange information between the ECU code errors and knowledge bases, based on data fusion methods, allowed us to consolidate and ensure data reliability, and then to optimize processed data in our distributed electronic systems, as the basic state for Industry 4.0 standards. At the same time, they offered optimized data packets when the gateway was tested as a service integrator for ECU maintenance. The embedded programming solutions offered us safe, reliable, and flexible data packet management results on both communication systems (Transmission Control Protocol/Internet Provider (TCP/IP) and Controller Area Network (CAN) Bus) on the Electronic Control Unit (ECU) tested for diesel, high-pressure common rail engines. The main goal of this paper is to provide a solution for a smart, hardware–software, Industry-4.0-ready gateway applicable in the automotive industry. [ABSTRACT FROM AUTHOR]