1,720,977 research outputs found
A new topology for battery systems: Reconfigurable Cascaded Multilevel Converter
Full text linkElectric vehicles cover a fundamental role for the sustainability transition of the transport sector. In the past ten years, the investments and efforts dedicated to the developments and improvements of electric powertrain have been increasingly significant from almost all automotive companies. Battery electric vehicles are the most promising solution, guaranteeing zero local emissions and high efficiency in energy conversion.
However, the electrical architecture adopted until now, consisting in a stiff connection between a battery pack and a two-level inverter, presents two main drawbacks related to the converter topology and the energy system configuration. On one hand, the two-level inverter can guarantee high efficiency only at nominal loads, showing drastic drops for partial loads operations. On the other hand, the battery pack is characterized by a fixed serial and parallel connection of battery cells, limiting the energy delivery of one string to the weakest cell. Both drawbacks are extremely
critical in electric vehicles applications, since the motor is required to often work at partial loads - i.e. in city traffic - and the driving range may significantly decrease with the low efficiency operations of the battery pack.
Therefore, some research works have suggested a conceptual revision of the converter and battery pack used in electrical powertrain structures. In this framework, multilevel converters started to gain attention as valid candidates to replace conventional converters in powertrain architectures. Splitting the battery pack in several modules allows to limit the serial connection of cells and consequently decrease the probability of having multiple weak cells. Moreover, the presence of more submodules reduce the stress on the devices, permitting a theoretical indefinite increase of the DC-link voltage.
Since an optimal battery system management relies on on the possibility to access the single battery cells, other works in the scientific literature suggested the utilization of Reconfigurable Battery Systems. These systems allow to perform active management of the battery system by controlling the connection between the battery cells through a coherent placement of electronic switches.
The role of Multilevel converters in electrical powertrain is considered central in this work. This research work presents a new topology, called Reconfigurable Cascaded Multilevel converter able to simultaneously implement the power conversion and the battery management. In each submodule, battery cells are serially connected in groups of three through a pattern of switches, forming a single unit called Reconfigurable Battery Module. In this way, each battery cell can be
controlled, enhancing sorting algorithms during both charging and discharging processes and fault tolerant strategies. The new topology is explained in details and then used in different case scenarios to prove its validity
AC Direct Charging for Electric Vehicles via a Reconfigurable Cascaded Multilevel Converter
No full textThis paper presents a charging architecture for the Reconfigurable Cascaded Multilevel converter, which was specifically designed for electric vehicle (EV) powertrain applications. The RCMC topology is capable of executing power conversion and actively managing battery systems concurrently. The active battery management is achieved using the Reconfigurable Battery Module, which regulates the serial connection of cells via a switch pattern. In this paper, the RCMC is directly interfaced with an AC three-phase power system, facilitating the dynamic control over battery cells charging. Its inherent design allows for the implementation of various charging algorithms, customizable to specific requirements, without necessitating additional intermediary power stages. Firstly, an overview of the RCMC topology is given, and an analysis to define the optimal filter inductance is carried out. Subsequently, after the AC system characteristics are explained, two charging algorithms are presented and described: one prioritizes State of Charge (SOC) balancing among battery cells, while the other focuses on minimizing power losses. Moreover, a time estimation computation for the RCMC is carried out considering a two-level AC charging station. The result is compared with the time required for a conventional battery pack. The results show a reduction of 10 s in charging time for a mere 20% increase in SOC. Finally, the experimental setup is presented and used to validate the efficacy of the proposed algorithms
Direct AC charging of EV Reconfigurable Cascaded Multilevel Converter
No full textThis paper presents the Reconfigurable Cascaded Multilevel Converter (RCMC), employed for EV powertrain applications, in charging configuration. The converter is directly connected to an AC three-phase power system and the battery modules are charged by dynamically controlling the reconfigurable battery modules. The intrinsic structure of the converter gives the advantage to implement different charging algorithms, according to customizable requirements, without the need of extra middle power stages. Two charging methods are proposed and explained in detail: the first one prioritizes the SOC balancing between the battery modules, the second one the power losses reduction. Finally, a charging time estimation is computed for the RCMC and for a classic battery pack, assuming to increase their initial state of charge of 20%. The computation results show that the Reconfigurable Cascaded Multilevel Converter requires 40% less time than the battery pack
A mathematical model for the optimal configuration of automated storage systems with sliding trays
No full textKalman filter estimation method for battery cell parameters in Reconfigurable Cascaded Multilevel Converter
No full textAutomating Bin Packing: A Layer Building Matheuristics for Cost Effective Logistics
No full textIn this paper, we address the problem of automating the definition of feasible pallets configurations. This issue is crucial for the competitiveness of logistic companies and is still one of the most difficult problems in internal logistics. In fact, it requires the fast solution of a three-dimensional Bin Packing Problem (3D-BPP) with additional logistic specifications that are fundamental in real applications. To this aim, we propose a matheuristics that, given a set of items, provides feasible pallets configurations that satisfy the practical requirements of items' grouping by logistic features, load bearing, stability, height homogeneity, overhang as well as weight limits, and robotized layer picking. The proposed matheuristics combines a mixed integer linear programming (MILP) formulation of the 3D-Single Bin-Size BPP (3D-SBSBPP) and a layer building heuristics. In particular, the feasible pallets configurations are obtained by sequentially solving two MILP sub-problems: the first, given the set of items to be packed, aims at minimizing the unused space in each layer and thus the number of layers; the latter aims at minimizing the number of shipping bins given the set of layers obtained from the first problem. The approach is extensively tested and compared with existing approaches. For its validation we use both realistic data-sets drawn from the literature and real data-sets, obtained from an Italian logistics leader. The resulting outcomes show the effectiveness of the method in providing high-quality bin configurations in short computational times
Impact of the DC-DC Stage on Grid-Connection Stability in Solid-State Transformer
No full textThis paper addresses the impact of the dc-dc stage on the grid-connection stability of a three-phase Solid-State Transformer based on the Cascaded H-Bridge and Dual Active Bridge topologies. In particular, the analysis aimed to reveal and discuss the impact of the isolated bidirectional dc-dc stage on the input dq-frame impedance matrix properties in terms of its passivity. For this purpose, the d-axis input impedance has been mainly addressed in this work. Its low-frequency simplified expression has been derived, by means of which its real part and the negative-resistance region upper limit can be analytically deduced, enabling a passivity-oriented design procedure. It is demonstrated that the dc-dc converter lowers that limit thus enhancing the grid-connected Solid-State Transformer passivity. The analysis performed in this work can be applied to a generic ac-dc-dc topology
Experimenting LoRa‐compliant solutions in Real‐World Scenarios
No full textLong Range (LoRa) is one of the most promising technologies in the context of Low Power Wide Area Networks (LPWANs). Thanks to its unique features, it addresses some of the most representative Internet of Things (IoT) constraints, since it lowers energy footprints over long‐distance communications. In the context of environmental monitoring, many LoRa‐compliant solutions are now available. This work proposes a case‐study analysis of rapid prototyping platforms that leverage both the simplicity and effectiveness of the LoRa technology in the context of outdoor communications. The conducted experimental campaign concretely demonstrated the effects of the Spreading Factor (SF), Bandwidth (BW), and Coding Rate (CR) on the communication range in urban environments. At the same time, results highlighted that, in a 7 km range, the Packet Loss Ratio (PLR) can be as low as 15%
Balanced Charging Algorithm for CHB in an EV Powertrain
Full text linkThe scientific literature acknowledges cascaded H-bridge (CHB) converters as a viable alternative to two-level inverters in electric vehicle (EV) powertrain applications. In the context of an electric vehicle engine connected to a DC charger, this study introduces a state of charge (SOC)-governed method for charging li-ion battery modules using a cascaded H-bridge converter. The key strength of this algorithm lies in its ability to achieve balanced charging of battery modules across all three-phase submodules while simultaneously controlling the DC charger, eliminating the need for an additional intermediate converter. Moreover, the algorithm is highly customizable, allowing adaptation to various configurations involving different numbers of submodules per phase. Simulative and experimental results are presented to demonstrate the effectiveness of the proposed charging algorithm, validating its practical application
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