## 5 Numerical Simulation Results
### Sensitivity Analysis of Different Charging Preferences of EV Users  
The dynamic time-of-use price is formulated for the micro-grid containing different types of EV users in the simulation of the previous section. However, the charging preferences of EV users will have a significant influence on the final results of charging price and the dispatching effect of the micro-grid. Thus, when the proportions of normal, urgent, and economical EV users are set to 100%, 100%, and 100% respectively, the dynamic time-of-use price for the above three types of EV users is formulated, so as to analyze the influence of EV users with different preferences on the selection of charging strategies. The results are shown in three corresponding curves in Figure 8. The sub-item and comprehensive user satisfaction degrees of the three types of EV users are simulated and analyzed, as shown in Table 6.  
From Figure 8 and Table 6, we can see that the urgent EV users with eager charging requirements have lower sensitivity to the changes in charging price, compared to the normal and economical EV users. Therefore, they will sacrifice part of the economic benefits to obtain the charging service from the electricity grid, and the corresponding charging price for each time period is higher than that of the other two types of EV users, leading to the low economic satisfaction degree and high electricity convenience satisfaction degree of urgent EV users. For economical users, a lower charging price needs to be published to encourage this type of EV users to charge in the dispatching periods. Thus, the economical EV users have higher economic satisfaction degree and lower electricity convenience satisfaction degree, which means that they are willing to exchange electricity convenience for more economic benefits.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**The Types of EV Users** & \(R_{USD,1}\) & \(R_{USD,2}\) & \(R_{USD}\) \\ \hline Normal & 0.5259 & 0.9823 & 0.7601 \\ Urgent & 0.4764 & 0.9960 & 0.8036 \\ Economical & 0.5934 & 0.9601 & 0.7527 \\ \hline \hline \end{tabular}
\end{table}
Table 6: The sub-item and comprehensive satisfaction degrees of three types of EV users.  
Figure 8: Dynamic time-of-use charging price for normal, urgent and economical EV users in each period.  
To sum up, in the case of the same dispatching demand of a certain time period, the charging price for calling the urgent EV users is the highest, while the price for dispatching the economical is the lowest. In other words, the final dynamic time-of-use price will not exceed the above two limit values, regardless of the proportion of different types of EV users in the micro-grid.  
The final results will show differences when different types of EV users participate in micro-grid dispatching. In order to reflect the different dispatching results of the normal, urgent, and economical EV users, due to their diverse charging strategies under the guidance of the dynamic time-of-use price, the impact of three types of EV users with different charging preferences on the results of micro-grid dispatching are simulated and analyzed, as shown in Figure 9.  
The Figure 9 illustrates that the charging behaviors of economical EVs cannot fully track the output of the renewable energy when only the economical EV users participate in the dispatching, even if the grid gives a low charging price, which reflects that the dispatching effect of this type of EV users is the worst of the three. A high percentage of economical EVs will decrease the utilization rate of renewable energy. For the urgent and normal types of EV users, the electricity generated by distributed power sources can be completely absorbed under the guidance of their respective dynamic time-of-use price. Since the price of encouraging normal EV users is higher than that of the urgent, the urgent will be preferentially selected as the vehicles participating in the dispatching. That is to say, the more urgent EV users exist, the higher the overall economy and independence of the micro-grid will be.