One of the biggest issues preventing the spread of electric vehicles is the difficulty in supporting distributed fast charging stations by actual distribution grids. Indeed, a significant amount of power is required for fast charging, especially if multiple vehicles must be supplied simultaneously. A possible solution to mitigate this problem is the installation of auxiliary batteries in the charging station to support the grid during high peak power demands. Nevertheless, the integration of high-voltage batteries with significant power is not a trivial task. This paper proposes the configuration and control of a converter to integrate batteries in a fast charging station. The proposed configuration makes it possible to decouple the grid power from the vehicle power using several auxiliary battery modules. At the same time, the converter makes it possible to draw different amounts of power from the battery modules, allowing the use of second life batteries performing in different ways. This paper discusses the design, control, and operation of the converter. Moreover, the effectiveness of the proposed control is shown by means of numerical results.

This paper proposes a novel balancing control strategy for modular multilevel converters (MMCs) integrating a battery pack (BP) at the submodule level. During the converter operation, balancing the energy of the distributed resources within the converter is necessary to ensure the converter stability, avoid generating undesired current harmonic components, and increase the overall system efficiency. In particular, exploiting the MMC topology, AC and DC circulating currents are controlled to cope with unbalanced conditions. In this context, this paper proposes a circulating current control strategy to equalize the state-of-charge (SOC) values of BPs by properly injecting AC and DC circulating currents. In addition, a dynamic saturation method for the circulating components was designed to reduce the SOC equalization time while continuously preventing the design converter limitations from being overcome. The proposed control algorithm was experimentally tested and compared with a state-of-the-art solution, which demonstrated its effectiveness in terms of the overall efficiency and balancing time.

This paper proposes a sizing procedure for the cascaded H-bridge (CHB) converters integrating the battery energy storage system at the submodule level through a dual active bridge (DAB) converter. The suggested methodology considers different parameters, such as the adopted modulation strategies and the topology of the DAB converter employed. Three possible DAB configurations are considered: the one using only full-bridges (for both sides), the one using only half-bridges (for both sides) or a mixed configuration using half-bridge on one side and full-bridge on the other side. After determining the system parameters, the solution capable of reaching the required efficiency target at the minimum cost is obtained. The cost analysis and the efficiency evaluation are carried out considering a dataset containing almost 1000 semiconductor devices whose datasheets have been taken from the manufacturers' websites. The procedure has been developed in the framework of a collaboration with NHOA Energy and its effectiveness is demonstrated by sizing a 1 MW-CHB converter combined with energy storage systems at 11 kV.

Light railways are a low carbon emission form of transport, but it is often difficult to electrify tracks in central urban areas. This limitation can be avoided by integrating an on-board battery storage connected to the dc bus of the traction inverter with a boost dc/dc converter. However, the boost converter requires a bulky inductor and introduces additional power losses that are undesirable. This paper proposes to replace the standard induction motor with an open ended winding induction motor connected at one end to the overhead line with the traction inverter and to the other end to a battery with a second inverter in order to reduce the power losses of the traction drive. The paper addresses design and control aspects for light rail vehicles with open ended winding induction machines when the power supply is partly from the overhead line and partly from the on board battery. Moreover, the paper studies in detail the hybrid operations of the traction system i.e. when the overhead line charges the battery during coasting or at the stops. Finally, numerical simulations for a real use case are presented to quantify the reduction of power losses in comparison to the standard solution.

The European Call HORIZON-CL5-2024-D5-01-02 suggested goals and future trends for electric powertrains. Focusing on the next-generation electric vehicles, 1.2 kV architectures were recognized to be suitable outcomes for improving the state of the art, enabling a strong reduction in the charging current and enlarging the vehicle driving ranges. Nevertheless, sizing all the vehicle components for such high voltage could be counterproductive. Hence, this work proposes the adoption of a 1.2 kV dc, 350 kW modular multilevel converter with distributed battery packs that can carry out ultra-fast-dc recharges. Its modular nature allows sizing the power electronics and several passive components on much lower voltage levels, with low cost-per-component and limited losses. In addition, this converter topology proved to be flexible, implements cell battery balancing algorithms, and ensures backward compatibility with the existing dc and ac charging modes without the need for any additional on-board charger. Finally, the converter can be installed on a dual motor powertrain. This article shows an electric drive involving two 440 V, 75 kW induction machines. The traction and dc-charging capabilities of the converter were experimentally verified with a small-scale prototype.