# PV-Powered Charging Station for Electric Vehicles: Power Management with Integrated V2G
## 4 Simulation Results and Analyses
### Simulation Conditions and Assumptions  
In order to ensure the validity of the simulation, it is assumed that all EVs have the same battery characteristics. We can configure different battery characteristics, such as capacity, according to the EV model [32], which will be mentioned in future research. Figure 6 shows the real solar irradiance and PV cell temperature from 8:00 to 22:00 on 28 May 2019, at Compiegne, France. In order to highlight the \"peak\" periods of the public grid, the energy tariff of the public grid from 8:00 to 22:00 is designed as shown in Figure 7. It exists two grid \"peak\" periods 11:00-13:00 and 18:00-20:00, and the tariff is fixed during the two time-periods. The closer the time point to these two time-periods, the higher the tariff to absorb power from the public grid, which encourages EVs to discharge close to the \"peak\" periods of the public grid and charge away from the \"peak\" periods of the public grid. The simulation parameters of the system are detailed in Table 1[31], where \(P_{DIS}\) is the constant discharge power, which was chosen 89.6 kW, \(I_{S\_MAX}\) is the storage current limitation, \(SOC_{MIN}\) and \(SOC_{MAX}\) are the _soc_ lower limit and the _soc_ upper limit, respectively, \(C_{ERF}\) is the capacity of the storage, and \(v_{C\_REF}\) is the rated voltage of DC bus. Figure 6: Solar irradiance and PV cell temperature. Figure 7: Energy tariff of the public grid. The power limits of the point of common coupling of the EV charging station with the public grid are shown in Table 2. Since loads of the public grid are different according to different periods, the power limits are set accordingly to ensure the stability of the public grid. There are two types of power limits: grid injection power limit and grid supply power limit. In the \"peak\" periods of the public grid, the injection power limit is 100 kW, the supply power limit is \(-\)10 kW, and in other periods, the injection power limit is 50 kW, and the supply power limit is \(-\)50 kW. The simulation parameters of EVs are shown in Table 3. The three charging modes for EVs, i.e., fast mode, average mode, and slow mode, are considered. When a new EV arrives, the user can choose waiting or departure if there is no free charger. \"CH\" represents \"charge\", \"DCH\" represents \"discharge\", \"F\" represents \"fast mode\", \"A\" represents \"average mode\", \"S\" represents \"slow mode\", \"W\" represents \"waiting\", and \"D\" represents \"departure\". \(Ordinal_{EV}\) represents the ordinal number of EVs. In this case, in order to reflect the effectiveness of the algorithm, the EV number is randomly given 16, and \"Type\" and \"Choice\" are randomly generated by an algorithm. \(T_{arrive}\) represents the time each EV arrives at the charging station. \(T_{depart}\) represents the time each EV leaves the charging station. \(SOC_{EV\_in}\) represents the initial \(soc_{EV}\), \(SOC_{EV\_final\_lim}\) represents the limit value of \(soc_{EV}\) when the EV departures that set by users. According to the willingness of users, EVs come to charging stations for two purposes: being charged and discharging. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **Value** & **Parameter** & **Value** \\ \hline \(P_{FAST\_MAX}\) & 83 kW & \(I_{S\_MAX}\) & 115 A \\ \(P_{AVER\_MAX}\) & 27 kW & \(SOC_{MIN}\) & 20\% \\ \(P_{SLOW\_MAX}\) & 7 kW & \(SOC_{MAX}\) & 80\% \\ \(P_{DIS}\) & 89.6 kW & \(C_{ERF}\) & 300 Ah \\ \(Number\) of chargers & 5 & \(v_{C\_REF}\) & 400 V \\ \(JEV\_ERF\) & 24 kWh & \(P_{PV\_STC}\) & 100 kW \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Simulation parameters of the system. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Period** & **8:00-11:00** & **11:00–13:00** & **13:00–18:00** & **18:00–20:00** & **20:00–22:00** \\ \hline Grid injection power limit (kW) & 50 & 100 & 50 & 100 & 50 \\ Grid supply power limit (kW) & \(-\)50 & \(-\)10 & \(-\)50 & \(-\)10 & \(-\)50 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Power limits of the public grid.