Decentralized multi-objective optimization of distribution system operation exploiting flexibility of electric vehicle parking lots and photovoltaic systems

Distributed energy resources (DERs) can provide flexible services to enhance the operation of distribution networks (DN). This study uses flexibility models for photovoltaic (PV) systems and electric vehicle (EV) parking lots (PL). A stochastic optimization model calculated the day-ahead PL consumption profiles and the maximum available flexibility for each 15-minute interval. The model assumes that flexibility provision is followed by energy recovery periods to maintain EV charging services. The distribution system operator (DSO) uses these flexibilities to optimize DN operation through a multi-objective formulation that accounts for both technical and economic factors. The optimization problem is based on a multi-period formulation to consider the effect of PL energy recovery at future intervals. The problem is decomposed using the Alternating Direction Method of Multipliers (ADMM) for a decentralized solution. Results are presented for three cases simulating 24-hour operation of IEEE 123-node test feeder, with four PLs and 15 PV systems. The results show improvements in voltage profiles and associated costs by comparing the priority weights for the two objectives. It was also shown that it is possible to modulate the contribution of flexible service purchases, both to the improvement of the voltage profile and to the cost, by varying the number of iterations of the ADMM algorithm.