## 2 System Model Formulation  
### Overall System Architecture  
In this paper, the power management scheme of interdependent MG and EV fleets is presented to schedule charging/discharging operations of parked EVs in PV-based charging station considering the local load demand and PV power production. In the grid-connected mode, the utility grid is linked to the electricity network through the point of common coupling (PCC), and the electricity load is also connected to the electricity network to be supplied power from power resources, such as the utility grid, PV system, and discharging of EVs. For data communication in the MG, the microgrid central controller (MGCC) is used as communication interface to maintain the energy balance of the electricity network. Typically, as the number of EVs accommodated in the charging station increases, the electricity network can be quite unstable due to the increasing peak load caused by electricity load of the charging station. Consequently, power management is essential for the charging station to manage EVs participation and charging/discharging scheduling. For the economical and energy-efficient EV charging/discharging scheduling of the PV-based charging station, the system operator of the charging station needs to consider various information such as the state of grid system, weather information, electricity purchasing/selling price, and EV information. The system operator receives the information of the local load demand in the grid system and electricity selling prices such as SMP and REC from the KPX. Weather information is obtained from the Korea Meteorological Administration (KMA), and maximum PV power output is calculated by solar irradiance data in weather information. The electricity rate purchased from the utility grid is determined based on the DR program specified by the Korea Electric Power Corporation (KEPCO). The charging station receives specific information relevant to charging/discharging conditions of EVs such as current SOC, target SOC, arrival time, and scheduled departure time. Charging batteries is a critical task to manage proper operation of sensor network [53], transportation system [54], and many more. In the PV-based charging station, EVs can be utilized as a power supply/demand component while parked. When an EV is parked and connected to the charging system, the system operator receives the parked EVs' information. Based on this information, a charging/discharging operation is applied to each EV in real-time with the proposed EV charging/discharging scheduling algorithm considering the local load demand and generated PV power output. The PV-based charging station operator is responsible for charging each parked EV to target SOC within a predetermined parking time while maintaining the stable electricity network. The frequent charging and discharging cycle of EV incurs the reduction in the usable lifetime of the EV battery. Due to the battery degradation, the EV owner's permission is necessary to utilize the EV to the V2G application. For high penetration of EVs in V2G system, an economic effect needs to be provided to the EV owners who permits to participate in V2G service as well as charging station operator. In the charging station, a parking fee discount can be served as an economic benefit for EV owners. The overall system architecture of the PV-based charging station is presented in Figure 1. The utility grid is linked to the electricity network via transformer, and electricity can be supplied to the local load demand and charging demand of EVs through the electricity network. The PV system installed on the charging station is connected to the AC bus with a DC-AC converter, and the produced PV power can be supplied to the local load demand and charging demand of EVs according to the power management scheme. The parked EVs are interconnected to the electricity network using bidirectional charger that is a state-of-the-art EV charger capable of charging and discharging power from an EV battery.