## 5 Conclusions  
In order to deal with the cooperation among VPPs, SES, and the unaggregated resources, a multi-layer optimization model of energy trading strategy for VPPs is constructed based on hybrid game theory among SES, VPP, PVP alliance, and the outer power grid. This optimal energy trading model cannot be directly solved by traditional optimization algorithms because of its nonconvex nonlinear characteristics. In this paper, novel hybrid game theory-based optimization algorithms have also been proposed and discussed to obtain the optimal energy trading strategy. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Strategy** & **Carbon Emissions/kg** & **Carbon Trading Costs/Yuan** \\ \hline
1 & 14,776.45 & 3433.23 \\
2 & 14,895.78 & 3508.85 \\
3 & 18,899.30 & 4669.79 \\
4 & 19,254.21 & 4776.26 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: VPP carbon emissions and carbon trading costs under different operating scenarios. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Confidence Level** & **SES Earnings/CNY** & **VPP Earnings/CNY** &
\begin{tabular}{c} **PVP Affiliate** \\ **Earnings/CNY** \\ \end{tabular} \\ \hline
0.8 & 4706.73 & 14,925.15 & \(-\)45,479.42 \\
0.85 & 4659.26 & 15,269.47 & \(-\)45,461.48 \\
0.9 & 4659.26 & 15,990.78 & \(-\)45,377.47 \\
0.95 & 4451.95 & 17,186.51 & \(-\)45,363.57 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Incomes of SES, VPP, and PVP alliance under renewable energy output uncertainty. (1) The optimization operation under the multi-agent win-win situation of SES-VP-PVP realizes the maximization of the respective benefits of VPP, SES, and PVP alliance. Compared with excluding P2P trading and load demand response in the PVP alliance, the total multi-agent revenue of the proposed method in this paper increases by about 13.42%, in which the revenue of VPP increases by about 11.64%, the total carbon emission reduction is about 23.2%, and the total carbon transaction cost is reduced by CNY 1343.03, which promotes the low-carbon economic operation of VPP. (2) The increase in the confidence level of the uncertainty of renewable energy output will have a direct impact on the returns of all market entities. Strong uncertainty of renewable energy output will affect the economic optimization operation of VPP flexible adjustable resources, which will affect the purchase and sale intention of VPP, SES, and PVP alliance, reduce the utilization rate of SES, and affect the income of PVP alliance members. The results show that when the confidence level of renewable energy output is from 0.8 to 0.95, the VPP revenue increases by about 15.15%, the SES revenue decreases by about 5.4%, and the total revenue of PVP alliance increases by about 0.25%. (3) After the PVP alliance members cooperate to carry out P2P power trading, energy complementarity is realized. On the basis of reducing the cost of purchasing electric heat, each member's income is improved, and a fair and reasonable distribution of income is guaranteed. The individual revenue of PVP members after cooperation increased by 1.215%, 1.698%, and 1.661%, respectively, compared with no cooperation strategy. Since PVP itself does not produce heat, most energy needs to rely on VPP to provide, so the overall total revenue of PVP alliance is limited, by about 1.49%. The biggest challenge brought to the implementation of the model in various market environments is how transmission rights are billed when VPPs trade electricity energy with the outer power grid, which directly affects the trading strategies between VPPs and other entities. In future, the transaction prices among multiple market entities would be studied under different maximum delivered power between VPP and the outer power grid, which would be also related to the cost of transmission and substation construction work. Conceptualization, J.T. and J.W. ; methodology, J.T. and J.W. ; validation, J.T. and R.C. ; investigation, J.W. and R.C. ; writing--original draft preparation, H.Y., L.S., Y.S., H.Z. and J.T. ; writing--review and editing, J.T. and L.S.