## 4 Example Analysis
### The Influence of Energy Storage System on the Benefit of the Robust Method  
Considering the fluctuation of renewable energy, in order to increase the consumption capacity of the power grid for distributed energy and reduce wind/light curtailment, the energy storage device with a capacity of 500 MW is introduced on the original system. The output of various types of energy is shown in Figure 7. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Penetrance**} & \multicolumn{2}{c}{**The Fluctuation of Peak-Load**} & \multirow{2}{*}{**Rotational Reserve**} & \multirow{2}{*}{**Risk–Benefit (RMB)**} & \multirow{2}{*}{**Environmental Benefits (RMB)**} & \multirow{2}{*}{**Operation Efficiency (RMB)**} \\  & & & & & & \\ \hline
18.4\% & 179.7 & 13.8\% & 29,315.7 & 10,325.9 & –24,702.6 & 14,939 \\ \hline
36.8\% & 323.5 & 29.2\% & 490,167.7 & 8128.4 & –78,763.6 & 419,532.5 \\ \hline Difference & 143.8 & 15.4\% & 460,852 & –2197.5 & –54,061 & 404,593.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Comparison of two penetrance robustness methods. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**The Proportion** & 20\% & 25\% & 30\% & 35\% & 45\% & 55\% \\ \hline
**Comprehensive cost** & 10,559,895.1 & 10,049,988.8 & 10,019,681.4 & 10,056,537.7 & 10,475,301.1 & 11,576,782.2 \\
**(RMB)** & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Optimization results of uncertain sets. As can be seen from the above Figure 7, the introduction of the energy storage system effectively improves the output of the wind turbine during the period from 2:00 a.m. to 6:00 a.m., and reduces wind curtailment. At the same time, the discharge of the energy storage system occurs during the two periods with the highest load from 8:00 a.m. to 10:00 a.m. and from 15:00 p.m. to 16:00 p.m. Considering that the two periods are the periods when the output of the natural gas turbine rapidly increases and decreases, and the natural gas turbine is not very efficient and the operation cost is large, the discharge of the energy storage system mainly replaces the output of the natural gas turbine. The benefit changes after the introduction of energy storage is shown in Table 5.  
From Table 5, we can get the following results. (a) Although the introduction of the energy storage systems can reduce wind curtailment and increase the proportion of distributed energy, the energy storage system itself is relatively expensive and will generate high operating costs, as a result, the benefits are not obvious from these two perspectives  
(b) The introduction of the energy storage systems can effectively reduce the output of each generator set in the period with high load, and its peak load cutting, and valley filling function can effectively reduce the pressure of the grid and increase the risk-benefit of the system, which is the main source of income from the introduction of the energy storage systems. \begin{table}
\begin{tabular}{p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt}} \hline \hline  & \begin{tabular}{c} **The Fluctuation** \\ **of Peak-Load** \\ **New Energy** \\ **(MW)** \\ \end{tabular} & \begin{tabular}{c} **Rotational** \\ **Reserve** \\ **(MW)** \\ \end{tabular} & \begin{tabular}{c} **Risk–Benefit** \\ **(RMB)** \\ \end{tabular} & \begin{tabular}{c} **Environmental** \\ **Benefits** \\ **(RMB)** \\ \end{tabular} & \begin{tabular}{c} **Operation** \\ **Efficiency** \\ **(RMB)** \\ \end{tabular} & \begin{tabular}{c} **Comprehensive** \\ **Benefits (RMB)** \\ \end{tabular} \\ \hline \begin{tabular}{c} No energy \\ storage \\ system \\ \end{tabular} & 209.9 & 16.1\% & 34,422 & 11,963 & \(-\)28,617 & 17,768 \\ \hline \
\begin{tabular}{c} With energy \\ storage \\ system \\ \end{tabular} & 162.6 & 12.3\% & 96,482 & 56,891 & \(-\)68,285 & 85,088 \\ \hline
\begin{tabular}{c} Difference \\ \end{tabular} & \(-\)47.3 & \(-\)3.7\% & 62,060 & 44,928 & \(-\)39,668 & 67,320 \\ \hline \hline \end{tabular}
\end{table}