Proposal of Peak Load Suppression Measures for EV Quick Charging using Charge Shift and Storage Battery

Abstract

Recently, the capacities of on-board batteries and the outputs of quick chargers have been increasing. Increase in the battery capacity allows EV owners to charge more freely; however, charging may concentrate at a certain time such as on Friday afternoon, when EV owners charge in preparation for weekend's long trip. In the previous study, we evaluated the impact of quick charging on peak load at the system level and showed that a large peak occurs when charging behavior changes at a specific timing. To simulate the change in charging behavior, we set up the case that the charging threshold is raised to 60 percent on Friday afternoon. In this study, we assumed three patterns as trigger timing for charging shift: Tuesday, Wednesday, and Thursday, and two patterns as change in the charging threshold: 60 and 40 percent.

Through the analysis targeting Aichi Prefecture, we obtained following findings. (1) If the charging threshold is raised to 60 percent, the peak suppression effect remains for about two days. However, this measures cannot be used as a peak load suppression measures because the peak nearly equal to the reference case occurs when the charging threshold is raised to 60 percent. (2) If the charging threshold is raised to 40 percent, the peak suppression effect remains only about one day. Thus, only the case that the charging threshold is raised to 40 percent on Thursday afternoon shows a suppression effect on Friday's peak. (3) The economic value of the peak suppression effect of charging incentives is calculated as 31yen/kWh.