Coordinated Control Strategy of Electric Vehicles and Energy Storage System for Smoothing Power Fluctuations of Photovoltaics

The increasing penetration of distributed photovoltaic (PV) generation causes significant power fluctuations in the distribution network. To maintain power quality and reliability, some measures must be taken to manage these fluctuations. Energy storage system (ESS) which have the advantages of high power density and fast charging and discharging switching speed are widely proposed to smooth the PV fluctuations. However, the operation cost of ESS is expensive. Dispatching charging and discharging power of EV is an economical way to solve the problem, but the dispatchable capacity of EV is not always sufficient. Therefore, we propose a real-time control strategy that the PV power fluctuations can be smoothed by EVs and ESS, in which a convex optimization model is established to solve the problem. This strategy smooths the PV power under the uncertainties of the PV output using the flexibility of the EV. The smoothing performances can be ensured by ESS output when the dispatching capacity of EV is insufficient. The smoothing error is controllable with the convex optimization model. The proposed strategy is able to reduce the total installed capacity and avoid the overcharge and overdischarge of ESS. Case studies were carried out to demonstrate the validity and application advantages of the strategy.