Life cycle optimization framework of charging–swapping integrated energy supply systems for multi-type vehicles

Abstract

The energy supply infrastructure is an important guarantee for vehicle electrification. Its economy, service capability and grid friendliness are critical factors drawing wide attention. To reduce the cost of energy storage devices that alleviate the high-power grid impact from fast charging station, this study proposes a novel energy supply system configuration that integrates fast charging for passenger vehicles and battery swapping for heavy trucks, and discharges the large-capacity swapping batteries to support fast charging. The influences of station configurations, including in-station batteries, charging and swapping equipment on the system economy, service quality, and grid capacity demand are revealed through system modeling and analysis. The impact of the charging time on battery degradation during operation is also explored. Moreover, a life cycle optimization framework for the charging–swapping integrated system is formulated, together with the complementary control strategy that realizes bidirectional energy coupling of fast charging and battery swapping loads. In this framework, the battery swapping service model is established to quantify the service quality; the electrochemical mechanism model is used to evaluate the battery degradation during charging and discharging processes; and the life cycle cost model is established by integrating the investment and operation costs of the energy supply system. On this basis, the design and control variables are collaboratively optimized towards the maximal life cycle benefits. Based on the actual load characteristics of charging and swapping stations, a comparative study is performed for the proposed operation scheme and the general service quality-prioritized scheme. The obtained results show that the maximum station power is reduced by more than 0.6 MW, and the total life cycle cost of the energy supply system is reduced by over 1 million RMB under the proposed scheme, verifying its notable effect of life cycle economy improvement.