A two-stage stochastic programming approach for electric energy procurement of EV charging station integrated with BESS and PV

Energy procurement of an electric vehicle charging station (EVCS) needs medium-term decisions, which depend on the short-term energy transactions of the EVCS in real-time market. However, the energy exchange in real-time operation is affected by uncertainties related to the pool prices, electric vehicle (EV) load demand, and photovoltaic (PV) generation level. To comprehensively include the real-time considerations in the decision framework, this paper proposes a two-stage stochastic programming approach to formulate EVCS energy procurement and optimal equipment dispatch as a single problem. The objective is to minimize the total operational cost of EVCS. First, a decision-making framework is developed that integrates EVCS energy procurement, charging pricing, and equipment dispatch in order to make energy procurement decisions based on random nature of electricity pool prices, EV loads, and PV generation in real-time operations. Next, the developed decision framework is formulated as a two-stage stochastic program with risk modeling using Conditional value-at-risk (CVaR) index. The first-stage variables include medium-term bilateral contracts and EV charging prices, while the second-stage variables encompass energy dispatch of battery energy storage systems (BESS) and energy transactions with the main grid in real-time pool. In addition, uncertainties related to electricity pool prices, EV loads, and PV generation levels are characterized by stochastic scenarios generated based on historical data. The simulation results for an EVCS equipped with DC fast chargers and integrated with BESS and PV generation demonstrate the effectiveness of the proposed approach in achieving efficient and profitable EVCS energy procurement. It is observed that expected profit for beta = 0 is $11,308 while none of the bilateral contracts are selected in this case because the pool prices are expected to be cheaper. On the other hand, expected profit for beta = 100 is $9900 where some parts of the required energy are provided by the bilateral contracts in this case to avoid the risk of fluctuations in the real-time pool prices, but at the cost of lower expected profit.