Mitigation Solutions for the Magnetic Field Produced by MFDC Spot Welding Guns

Among the different welding technologies, portable welding guns are one of the most critical devices in relation to human exposure to electromagnetic fields. This paper focuses on medium frequency (MF) direct current guns proposing two actions aimed to the mitigation of the magnetic field generated during the welding process. The first action consists in the adoption of a passive shield for the on-board MF transformer. The analysis points out that the transformer alone produces a magnetic field that can exceed the prescribed limits. Therefore, a suitable mitigation system is identified. The second action aims to mitigate the predominant magnetic field that is generated by the electrodes of the welding gun. The analysis of the field waveforms shows that the rise time of the welding current pulse is the main parameter affecting the exposure index. The effect of the increase of the rise time is investigated through experimental and numerical analyses. The results prove that a small increase of the rise time causes a significant reduction of the exposure level. It is noteworthy that the two mitigation actions can be adopted on both existing and newly developed welding guns as they do not require any structural modification of the welding device

Power And Energy Demand to Support E-Mobility on Highway: The Italian Case Study

In recent years, market trends are confirming the increasing use of electric vehicles for private mobility. The use of such vehicles is inevitably affecting highway contexts as well. Therefore, highway network operators need to plan for the installation of adequate infrastructure to enable and manage the growing demand for fast charging expected in the coming years. This paper aims to assess the impact that this charging demand may have on the service areas (SAs) of the highway network operated by Autostrade per l'Italia. Starting from available traffic data, this paper proposes a methodology to forecast, for each service area, the future charging needs of EVs on a daily, monthly, and yearly basis. The analysis considers both the energy and the power that needs to be made available to ensure charging during daily traffic peaks. The results show that the impact generated by EVs will be generally significant, especially in terms of power demands with peaks between two and three megawatts. The methodology developed is entirely general and therefore applicable for similar planning in other highway or suburban roadway contexts. The validity of the developed methodology and the made assumptions have been preliminary confirmed through an initial set of data collected from one of the charging stations installed in one representative service area

Smart Charging for Electric Car-Sharing Fleets Based on Charging Duration Forecasting and Planning

Electric car-sharing (ECS) is an increasingly popular service in many European cities. The management of an ECS fleet is more complex than its thermal engine counterpart due to the longer ”refueling“ time and the limited autonomy of the vehicles. To ensure adequate autonomy, the ECS provider needs high-capacity charging hubs located in urban areas where available peak power is often limited by the system power rating. Lastly, electric vehicle (EV) charging is typically entrusted to operators who retrieve discharged EVs in the city and connect them to the charging hub. The timing of the whole charging process may strongly differ among the vehicles due to their different states of charge on arrival at the hub. This makes it difficult to plan the charging events and leads to non-optimal exploitation of charging points. This paper provides a smart charging (SC) method that aims to support the ECS operators’ activity by optimizing the charging points’ utilization. The proposed SC promotes charging duration management by differently allocating powers among vehicles as a function of their state of charge and the desired end-of-charge time. The proposed method has been evaluated by considering a real case study. The results showed the ability to decrease charging points downtime by 71.5% on average with better exploitation of the available contracted power and an increase of 18.8% in the average number of EVs processed per day

Dual-Active-Bridge Model and Control for Supporting Fast Synthetic Inertial Action

This article proposes a dual-active-bridge control to support the fast synthetic inertial action in DC microgrids. First of all, the selection of the isolated DC/DC converter to link an energy storage system with the DC bus in a microgrid is analyzed and the advantages of the dual-active-bridge converter controlled by a single-phase shift modulation justify its selection. An active front-end can be then adapted to connect the DC bus with an AC grid. Secondly, this paper presents the design of a discrete PI controller for supporting fast synthetic inertial action. In particular, a discrete dual-active-bridge model based on the transferred power between both converter bridges, which overcomes the approximations of the output current linearization model, is proposed. Moreover, the article introduces a novel equation set to directly and dynamically tune discrete PI parameters to fulfill the design frequency specifications based on the inversion formulae method. In this way, during the voltage/power transients on the DC bus, the controller actively responds and recovers those transients within a grid fundamental cycle. Since the developed set of control equations is very simple, it can be easily implemented by a discrete control algorithm, avoiding the use of offline trial and error procedures which may lead to system instability under large load variations. Finally, the proposed control system is evaluated and validated in PLECS simulations and hardware-in-the-loop tests

The positivity scale: Concurrent and factorial validity across late childhood and early adolescence

Despite the well-established protective functions of positivity (i.e., a dispositional selfevaluative tendency to view oneself, life, and future under a positive outlook) from middle adolescence to old age, its reliable assessment and contribution to a proper psychological functioning have received little attention during previous developmental phases. In this article, we aimed to evaluate the psychometric properties and construct validity of the eight-item Positivity Scale (P Scale; Caprara et al., 2012) during late childhood and early adolescence in a sample of British students (N = 742; 48% boys) from both primary (M age = 10.75, SD = 0.52) and secondary schools (M age = 13.38 years, SD = 0.94). First, results from confirmatory factor analysis (CFA) attested to the plausibility of the hypothesized 1-factor structure of the P Scale in a revised CFA model including the correlation between the residuals of two items similar in their wording. Next, we found evidence for strong (scalar) measurement invariance of the P Scale across late childhood and early adolescence as well as for its concurrent validity as indicated by expected relations of positivity to indicators of adjustment (i.e., prosocial behavior) and maladjustment (i.e., externalizing and internalizing problems). Overall, these findings support the concurrent and factorial validity of the P Scale as a short self-report instrument to measure children's tendency to view their experience from a positive stance. We discuss the implications of our results for improving the wording of the items composing P Scale as well as for understanding the dispositional mechanisms conducive to psychological health and wellbeing across late childhood and early adolescence

Novel Multi‐Vehicle Motion‐Based Model of Trolleybus Grids towards Smarter Urban Mobility

Trolleybus systems are resurfacing as a steppingstone to carbon-neutral urban transport. With an eye on smart city evolution, the study and simulation of a proper monitoring system for trolleybus infrastructures will be essential. This paper merges the authors’ engineering knowledge and sources available in the literature on designing and modeling catenary-based electric traction networks and performs a critical review of them to lay the foundations for proposing possible optimal alternatives. A novel multi-vehicle motion-based model of the DC catenary system is then devised and simulated in Matlab-Simulink, which could prove useful in predicting possible technical obstacles arising from the next-future introduction of smart electric traction grids, inevitably featuring greater morphological intricacy. The modularity property characterizing the created model allows an accurate, detailed, and flexible simulation of sophisticated catenary systems. By means of graphical and numerical results illustrating the behavior of the main electrical line parameters, the presented approach demonstrates today’s obsolescence of conventional design methods used so far. The trolleybus network of the city of Bologna was chosen as a case study

Efficient management of industrial electric vehicles by means of static and dynamic wireless power transfer systems

Industrial companies are moving toward the electrification of equipment and processes, in line with the broader energy transition taking place across the economy. Particularly, the energy efficiency and, consequently, the reduction of environmental pollution of intralogistics activities have become a competitive element and are now an actual research and development objective. A wireless power transfer is a contactless electrical energy transmission technology based on the magnetic coupling between coils installable under the ground level and a coil mounted under the vehicle floor, and it represents an excellent solution to decrease the demand for batteries by reducing vehicle downtimes during the recharge. This work aims to define a methodology to determine the optimal positioning of wireless charging units across the warehouse, both for static and dynamic recharging. To this aim, firstly, a mathematical model of the warehouse is proposed to describe transfers and storage/retrieval operations executed by the forklifts. Then, an integer linear programming problem is applied to find the best possible layout of the charging infrastructures. The optimal solution respects the energetic requirements given by the customer and minimizes the overall system cost. The proposed approach was applied to optimize the installation in a real-size warehouse of a tire manufacturing company. Several scenarios were computer generated through discrete event simulation in order to test the optimizer in different warehouse conditions. The obtained results show that integrated dynamic and static WPT systems ensure a constant state of charge of the electric vehicles during their operations

Catenary-Powered Electric Traction Network Modeling: A Data-Driven Analysis for Trolleybus System Simulation

In the context of smart cities, direct current overhead contact lines, usually adopted to power urban transportation systems such as trolleybuses, tramways, metros, and railways, can serve as a backbone to connect different modern emerging technologies. Among these, in-motion charging (IMC) trolleybuses with on-board batteries are expected to be very impactful on the DC network’s power flow and may require specific voltage and current control. These factors motivate the development of a simulation tool able to emulate these devices’ absorption and their effect on the supply infrastructure. The main innovative value of the work is to improve a simulation model of a trolleybus grid through a data-driven approach by using measurements of voltage and current output from a traction substation. The measurements are essential for understanding the behavior of vehicle weight variation throughout the day. Thanks to this information, a characterization of the current draw by conventional trolleybuses and IMC trolleybuses is then provided for each trolleybus route in a specific power section of the Bologna trolleybus system. By integrating the variation in vehicle weight within the model, a simulation of a possible daily operation of a trolleybus feeding section has been performed, obtaining a 7% error between the daily energy calculated from the simulation and that obtained through measurements. This analysis demonstrates the feasibility of the adopted simulation tool, which can also be used to evaluate additional hypothetical trolleybus operation scenarios. One of these possible scenarios considers IMC vehicles, and it is also evaluated in this paper

Magnetic loss analysis in coaxial magnetic gears

This paper proposes a procedure for computing magnetic losses in coaxial magnetic gears. These magnetic structures are made of permanent magnets and ferromagnetic poles in relative motion transferring torque between two shafts in a contactless way. The loss computation in magnetic materials is crucial to define the system performance. The flux distribution inside the iron parts is computed by means of the finite element method and a model of iron losses taking into account the rotational nature of the flux loci is applied. The procedure highlights where the major loss sources are present and gives the opportunity to evaluate some corrective measures to reduce their effects. Particular attention is devoted to the 2D modeling in presence of permanent magnets segmentatio

Uncertainty Quantification for SAE J2954 Compliant Static Wireless Charge Components

The present work aims at quantifying how, and how much, the uncertainties on the components and material parameters of a wireless power transfer (WPT) system for the static charge of electric vehicles affect the overall efficiency and functionality of the final produced device. With the aim of considering the perspective of a possible industrial developer, the parameters selected for the uncertainty quantification are chosen to be the capacitance values of the compensation capacitors and the electromagnetic material parameters used for the construction of the magnetic structure of a WPT system, i.e. the parameters of the elements to be purchased. The analysis is based on a standard system among the ones provided by the current SAE J2954 recommended practice