# Flexible Dispatch for Integrated Power and Gas Systems Considering Power-to-Gas and Demand Response
## 5 Simulation Results
### The Proposed Coordinated Optimization of IPGS  
In this part, take Case2 in Part B as an example to compare the individual optimization and coordinated optimization, and analyze the advantages of coordinated optimization in optimizing adjustable capacity allocation and economy. Figures 8 and 9 show the output of the units and the conversion of active power by the P2G facilities. \begin{table}
\begin{tabular}{c c c} \hline \hline  & **Case3** & **Case4** \\ \hline Units generating cost/$ & 190,393 & 181,665 \\ P2G operating costs/$ & 2400 & 1600 \\ Wind power curtailment cost/$ & 0 & 0 \\ Load shedding cost/$ & 4300 & 170 \\ Units adjustable capacity allocation cost/$ & 33,295 & 31,008 \\ P2G adjustable capacity allocation cost/$ & 687 & 308 \\ Demand response adjustable capacity Allocation cost/$ & — & 1398 \\ Total cost/$ & 231,075 & 216,151 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Dispatch results of power system in two cases. Figure 8: Power output of units in different dispatch modes: (**a**) Separate optimization and (**b**) coordinated optimization. Figure 9: Power converted by P2G facilities in different dispatch modes: (**a**) Separate optimization and (**b**) coordinated optimization. Observing Figure 8, it can be found that during the peak load hours (11:00-14:00 and 17:00-20:00), the coal-fired units G1, G2 and G3 with lower power generation costs all operate near the maximum power point, the adjustable upward capacity that can be provided is almost zero. In order to meet the upward scheduling flexibility requirements of the power system during these periods, both scheduling methods have started the gas unit G5 with rapid adjustment capabilities to provide electrical power services. Unlike the separate optimization, however, the coordinated optimization also started the gas unit G6 to participate in power dispatch and adjustable capacity allocation during peak load hours. It can be seen from Figure 9 that during the period of low power load (1:00-7:00), when the power system is individually optimized, the P2G1 with adjustable capacity allocation and lower cost is preferentially used. While the coordinated optimization, when the natural gas produced by P2G1 cannot be fully utilized, its maximum conversion power is adjusted, so that P2G2 is involved in power scheduling and adjustable capacity allocation from 2:00 to 3:00. In order to further illustrate the advantages of coordinated optimization in optimizing the adjustable capacity allocation, the upper and lower adjustable capacities of the power system configuration are analyzed. The upward adjustable capacity of the power system configuration under the two scheduling modes is shown in Figure 10.  
With reference to Figure 8, it can be seen that during the peak period of electric load (10:00-20:00), the upward adjustable capacity of the power system when independently optimized is mainly provided by the coal-fired power unit G4 and the gas unit G5. As the natural gas system node 6 connected to the gas unit G5 is also in the peak gas consumption period, it is not feasible for G5 to have adjustable capacities of 125.20 kcf, 119.55 kcf, and 123.94 kcf in 11:00, 17:00, and 18:00, respectively. In practice, the power system may experience load reduction during these periods. However, the coordinated optimization reduced the adjustable capacity provided by G5 by starting the gas unit G6 at 16:00, and at  
Figure 10: Power system upward adjustable capacity in different dispatch modes: (**a**) Separate optimization and (**b**) Coordinated optimization. the same time increased the upward adjustable space of G4, so that the availability of the adjustable capacity configuration in actual operation was guaranteed. In addition, due to the start-up of the G6 unit, the upward adjustable capacity at 17:00 through load shedding configuration was also reduced from 3.59 MW to 0.