Prioritized sharing of charging energy in a multiple charging unit based batteries swapping station at communication fault

Abstract

This paper presents a multiple-unit charging system for a battery swapping station. The main focus of the paper is communication system post-fault operation which can be used equivalently to the healthy communication based system. The main goal of the control system is to keep the charging priority for batteries with a higher state of charge and low priority for the batteries with a lower state of charge, when the available energy is limited. This is to obtain, at all times, as much as possible fully charged batteries ready for swapping at limited availability of primary energy. The goal with communication between charging units can be easily obtained through interchange of the information about each battery state of charge. In the case of communication channel fault, the proposed method implemented individually in each separate charging unit is based on two-dimensional nonlinear characteristic depending on each respective battery state of charge and the DC bus voltage common for all charging units. The method is verified in different conditions using a model of five charging units serving separately an 83.2 Ah battery each, fed from a common feeding power source.