Modelling and planning charging infrastructure for electrically driven buses

Full electrically driven buses become more and more popular in public transportation. Converting an existence fleet of Diesel buses to all electrically driven buses does need a lot of planning effort. Even efficient batteries need to be recharged from time to time. The charging infrastructure is expensive and must be planned carefully. Already existing transformer stations are typical energy sources and bus stops are candidates for charging stations. The challenge is to select the charging points spatial as energy sinks and connect them to the transformer stations as energy sources at minimal costs. Finally, this planning process is a problem of optimization. Some non-linearity of the batteries and of the energy consumption of the buses increases the difficulty of the problem. In this paper, we introduce a two-stage, iterative process to solve this problem of optimization for the charging infrastructure with the potential for the extensions to solve some related problems simultaneously. Initially a mathematical optimization based on a linearized model computes a solution that is optimal to a simplified linear model. In a second step, an event driven simulator validates the result from the first step. If the first solution does not hold, the first step is repeated with less restrictive constraints.