# Energy Management Scheme for an EV Smart
## 6 Results and Discussion  
### Power Allocation Schemes Comparison  
Firstly, the proposed power allocation method is tested in parallel with another power allocation method to verify its functionality. A general comparison is drawn with a battery capacity-based strategy [24], in which the batteries charge or discharge in descending order of their rated capacity. This comparison of both schemes is independent of the EMS control process. Hence, the constraints of 20% to 80% SoC are not applied here to show the behavior for a full battery discharge and charge.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Entity** & **Parameter** & **Value** \\ \hline \multirow{3}{*}{Grid} & \(V_{g}\) & 380 V \\  & \(f_{g}^{c}\) & 60 Hz \\  & \(L_{g}\) & 0.1 mH \\ \hline \multirow{2}{*}{Renewable energy} & \(P_{dg}\) & 150 kW \\  & DG & Y\({}_{dg}\) & \(\pm\)50\% \\ \hline \multirow{3}{*}{\(EV_{1}\) DC-DC converter} & \(V_{b(1)}\) & 360 V \\  & \(L_{b(1)}\) & 22.42 mH \\  & \(C_{b(1)}\) & 37.62 μF \\  & \(f_{s(DC1)}\) & 6000 Hz \\ \hline \multirow{3}{*}{\(EV_{2}\) DC-DC converter} & \(V_{b(2)}\) & 630 V \\  & \(L_{b(2)}\) & 3.28 mH \\  & \(C_{b(2)}\) & 52.91 μF \\  & \(f_{s(DC2)}\) & 6000 Hz \\ \hline \multirow{3}{*}{Grid side inverter} & \(S_{n}\) & 150 kVA \\  & \(V_{dc}\) & 700 V \\  & \(C_{dc}\) & 2551.02 μF \\  & \(L_{1}\) & 0.603 mH \\  & \(L_{2}\) & 0.015 mH \\  & \(C_{f}\) & 275.545 μF \\  & \(R_{f}\) & 0.078 Ohm \\  & \(f_{s(inv)}\) & 6000 Hz \\ \hline \hline \end{tabular}
\end{table}
Table 3: Parameter values.  
Eight simulations have been executed to study the SoC profiles of EV batteries under the discharging and charging scenarios, with four simulations for each method. The total power assigned to the smart charger to be distributed between the two EVs is 50 kW for the charging cases and 30 kW for discharging. The EVs are allowed to charge or discharge completely. The cases are simulated for the initial SoC of \(EV_{2}\) greater than \(EV_{1}\) and vice versa.  
Considering the reference method (RM) for power allocation [24], since the battery capacity of \(EV_{2}\) is greater than \(EV_{1}\) (Table 1), \(EV_{2}\) should be fully charged or discharged first, and afterward, \(EV_{1}\) is engaged. This practice is shown in Figure 12a-d. On the contrary, the proposed scheme employs both EVs simultaneously for discharging and charging (Figure 12e-h). It considers the battery size, as well as the current SoC and calculates the power references for each EV proportionate to the instantaneous energy stored on-board the EV.  
According to the reference method, the bigger battery should be engaged first for discharging, though it might have a low SoC, which can result in swift depletion. This aspect can be observed in Figure 12b, where the SoC of \(EV_{2}\) is at a low value, and it is depleted quicker, as compared to the proposed scheme (Figure 12f), where \(EV_{2}\) still has energy left (10% SoC) at the same time instant.  
Thus, if the batteries are discharged till the \(t=2\) s mark, the \(EV_{2}\) is depleted fully for the reference method as compared to the proposed approach. The reference power allocation scheme is undesirable from the \(EV_{1}\) owner's perspective as it causes battery degradation by reducing the number of life cycles [30].  
In case of charging, according to the reference technique, the \(EV_{2}\) is charged to 100% SoC quicker, and \(EV_{1}\) has to wait for its turn as shown in Figure 12c,d. This outcome is undesirable for the \(EV_{1}\) owner. Therefore, the battery capacity-based power allocation mechanism is a source of discontentment for both EV owners in different scenarios. Conversely, the proposed method is a favorable alternative to keep all EVs satisfied as the power has been allocated to them according to their on-board energy. Though the EVs charge or discharge at various rates, they complete charging or discharging at the same time.  
The following cases verify the overall functionality of the EMS incorporating the power allocation schemes.