## 7 Conclusions  
In this paper, a cooperative optimization method for a multi-microgrid system was proposed. Mathematical models of multi-microgrid systems including RESs and EVs were constructed. Energy cooperation of microgrids in the multi-microgrid system was accomplished via the mobile energy storage of EVs. The impact of ATSET of EVs on economic dispatching and capacity allocation of a multi-microgrid system was analyzed. A two-loop optimization methodology that considered the cooperation of economic dispatching and system allocation was proposed, and an IPSO algorithm was used to solve the optimization problem. Both EVs and RESs were succesfully optimized in the optimization. Four cases were presented to verify the cooperative optimization. By comparing the results of the four cases, the following conclusions are drawn:  
1. By ATSET of EVs, energy can be transmitted through different microgrids, and economic dispatching of microgrids in the regional multi-microgrid system is cooperatively optimized. Optimized energy exchanging between regional multi-microgrid system and the main grid contributes to the peak shaving of the main grid. 2. By optimizing both economic dispatching and capacity allocation of RESs and EVs, the total cost of the regional multi-microgrid system is dramatically reduced, and economic benefit is achieved. After a cooperative optimization, the independency of the microgrids' operation is raised and integration efficiency of RESs and EVs is improved. It is worth noting that the simulation system discussed in this paper was significantly simplified in order to clearly demonstrate the main methodology of the paper. Future works may focus on the application of the model to more complex systems. Real systems are always more complex, with various kinds of generation and load units, and some realistic factors such as the influence of the battery's remnant capacity on the behavior of EV owners can also be considered. A real system may also include storage batteries and micro-turbines. The way of applying the proposed model on real systems is an important topic of the future works. Moreover, since the charging and discharging prices \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Case 1** & **Case 2** & **Case 3** & **Case 4** \\ \hline EVs & RMG1 & 10 & 14 & 10 & 14 \\  & RMG2 & 10 & 15 & 10 & 12 \\ \hline  & RMG1 & 6 & 6 & 2 & 2 \\ WTs & RMG2 & 4 & 4 & 1 & 2 \\  & OBMG & 8 & 8 & 9 & 9 \\ \hline  & RMG1 & 9 & 9 & 9 & 6 \\ PVs & RMG2 & 6 & 6 & 0 & 0 \\  & OBMG & 12 & 12 & 18 & 20 \\ \hline Allocation cost of EVs (\$) & 6570.0 & 9526.5 & 6570.0 & 8541.0 \\ Allocation cost of RESs (\$) & 88,640.9 & 88,640.9 & 70,174.1 & 72,020.8 \\ Total cost of allocation (\$) & 95,210.9 & 98,167.4 & 76,744.1 & 80,561.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of Allocations in all Four Cases. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Case 1** & **Case 2** & **Case 3** & **Case 4** \\ \hline Cost of RMG1 (\$) & 67,872.8 & 67,491.1 & 55,053.9 & 56,012.3 \\ Cost of RMG2 (\$) & 38,063.0 & 37,374.5 & 36,345.5 & 36,306.4 \\ Cost of OBMG (\$) & 89,260.0 & 89,001.9 & 69,793.4 & 66,946.1 \\ Net Exchanged Energy (MWh) & 413.32 & 377.10 & 255.30 & 189.30 \\ Dispatching cost (\$) & 97,028.4 & 95,700.1 & 84,448.7 & 78,703.0 \\ Total Cost (\$) & 195,195.8 & 193,867.5 & 161,192.8 & 159,264.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparison of Costs and Net Exchanged Energy in all Four Cases. of EVs considered in this paper are constant, a more flexible pricing system for EVs' charging and discharging is also an issue that worth studying. Conceptualization, J.C. and C.C. ; methodology, J.C. and C.C. ; software, J.C.; validation, J.C.; formal analysis, J.C. and C.C. ; investigation, J.C. and C.C. ; resources, J.C. and C.C. ; data curation, J.C. and C.C. ; writing--original draft preparation, J.C.; writing--review and editing, J.C. and C.C. ; visualization, J.C.; supervision, C.C. and S.D. ; project administration, C.C. and S.D. ; funding acquisition, C.C.