Two-Mode Balancing Control Scheme for Modular DC/DC Converter Interfaced Battery Swapping Stations

In comparison to the traditional structure, the utilization of the modular dc/dc converter (MDDC) for integrating power battery packs in electric vehicle (EV) battery swapping stations (BSSs) presents notable advancements in cost-effectiveness, conversion efficiency, and stability. This article introduces a two-mode balancing control scheme tailored for the state-of-charge (SoC) differences due to the distinctive plug-and-play operation of BSS. First, the proposed scheme efficiently addresses high swapping demands by expediting the generation of full battery packs using a sorting selection control during the on-grid mode. Subsequently, during the off-grid mode, a flexible energy transfer loop, incorporating the dc inductor, capacitor, and submodules (SMs), enhances balancing capabilities through an internal circulation control. It can effectively address scenarios with low swapping demands where there is a shortage of battery packs that are not fully charged. Moreover, the proposed method ensures equal switching loss distribution and accelerates balancing speed, adding to its appeal. The practical validation of the proposed scheme is achieved through a 1-kW/1-kWh MDDC-BSS prototype equipped with 16 SMs.

I. Introduction

The escalating demand for electric vehicles (EVs) has underscored the critical need for an efficient charging infrastructure [1]. As the adoption of EVs continues its upward trajectory, the challenges posed by prolonged charging times and limited driving range become increasingly apparent, potentially impeding full market penetration. In response, battery swapping stations (BSSs) have emerged as a promising solution, offering an alternative to conventional charging methods [2], [3], [4], [5]. Normally, one BSS swaps battery packs with the same technical standard, including the battery pack’s socket type, rated voltage, and rated current. It enables the rapid exchange of depleted batteries with fully charged ones [6]. This method not only addresses the charging time constraint but also presents economic benefits to consumers, who can opt for leasing batteries instead of purchasing them, thereby avoiding the need for personal charging equipment [7]. In addition, the BSS assumes responsibility for all battery-related maintenance and replacements, mitigating potential safety risks associated with personal charging [8].