## 1 Introduction  
Environmental pollution, climate change, and global energy policy lead to the accelerating growth of electric vehicles (EV) [1, 2, 3]. According to numerous studies related to the EV charging technologies [4], the increased level of EV chargers and the lack of coordination in charging schemes could lead to:  
1. Voltage dips during periods of EV charging (particularly for fast chargers);
2. Reduction in power quality (both slow and fast charging stations are sources of harmonic distortion);
3. EV battery deterioration and capacity decrease (due to the battery's voltage level or temperature increase);
4. Overloading of distribution network transformers;
5. Increased energy losses (especially with larger direct current (DC) fast charging station penetration)  
Because they are clean and naturally abundant, renewable energy resources such as solar are an important component to provide the energy for the EV charging [5, 6]. Photo-voltaic (PV) generation is often integrated into EV charging stations to lower the cost and reduce the carbon footprint as well, and different control strategies are used for the integration of small EVs [7]. Strategies are including a grid-connected residential photovoltaic system with plug-in hybrid electric vehicle (PHEV) [8; 9] and solar-charged electric and fuel cell vehicles [10]. A comprehensive review of the current status and latest technologies for the integration of EV with the PV array and wind generator is given in [11]. A major disadvantage of charging EV from PV is the variability in PV production. To address the random nature of renewable energy, battery energy storage is often utilized. The combination of EV charger and the battery energy system (BES) can help to reduce adverse effects on the grid (reduce the peak load demand from the EVs, reduce grid losses and contribute to the grid regulation and reinforcement) [12]. The energy storage is charged when there is excess in the wind or solar energy. When this generation is insufficient, storage is used to charge the EV. In [13], three different algorithms for charging and discharging the local storage in the presence of EV chargers are compared. The first strategy is to discharge the battery at a constant rate during specific times of the day, and the second is based on available solar energy and the number of connected EVs. It was shown that a third strategy--a discharging based on the sigmoid function of connected EVs is the best strategy, compensating 71% of EV energy requirements from the gird. However, the amount of renewable energy coming from the battery is not calculated. In [14], a 10 kWh Li-ion battery bank is integrated into the EV-PV charger. It was proven that small-sized storage in the order of 10 kWh could help to alleviate the daily solar variations and reduce the grid energy by 25%. The paper [15] focused on the control and operation of a fast-charging station for EVs within a microgrid consisted of a PV system, a Li-ion BES and fast charging units. It is shown that with the proper control algorithm, the fast charging station requires the minimum amount of energy from the grid. The analysis was focused on fast chargers only, with a 120 A charging current. The battery-buffered EV charger can help to increase the distribution network flexibility as well. It can provide ancillary services for supporting the power grid, such as primary and secondary frequency and voltage control. Different smart charging schemes provide the flexibility of EV charging to closely match the PV production. A multiobjective decision-making methodology for the daily scheduling of EV fleet is proposed in [16; 17], including the minimization of the service waiting time, the maximization of ancillary service revenue, and the minimization of costs incurred by vehicle charging. The number of client requests and service waiting times are modeled by the queuing theory.