Chapter 8 - Scheduling of EV battery swapping in microgrids

Abstract

This chapter focuses on the operation aspect of an electric vehicle (EV) station system in the battery swapping context and investigates analytical scheduling methods for cost saving, efficiency improvement, and its complementarity with microgrids as an energy carrier. Specifically, we formulate an optimal scheduling problem for battery swapping in a microgrid that assigns to each EV a best battery station to swap its depleted battery based on its current location and state of charge. The schedule aims to minimize a weighted sum of EVs’ travel distance and electricity generation cost over both station assignments and power flow variables, subject to EV range constraints, grid operational constraints, and AC power flow equations. Due to the nonconvexity of standard power flow equations and the binary nature of station assignments, the joint battery swapping and optimal power flow problem is computationally intractable in general. We first summarize and discuss several representative linearized/convexified network models for microgrids. On this basis, we then provide two possible analytical solutions to the problem that may both find their application in real scenarios, either solving for an optimum in a centralized manner with potential difficulties in scaling or solving for one desirable suboptimum in a scalable distributed manner. Both solutions are numerically validated using a real test case.