## 5 Case Study
### Simulation Settings and Results Analysis  
(1) Effect of P2G on wind power accommodation and system carbon emission reduction  
In order to analyze the effect of P2G on the improvement of wind power accommodation and system carbon emission reduction capabilities of IPGES, the following two cases were set up for dispatching of IPGES. There is no P2G in case 1; there is P2G between the power grid and the gas network in case 2. In case 1 and case 2, both of them are in the reward and punishment ladder-type carbon trading with the benchmark carbon price of 20 \(\lx@sectionsign\)/t, and the objective function is to consider only the operation cost without considering the carbon trading cost. Figure 7 is a time sequence diagram of generators output and electrical power of P2G, Figure 8 is a time sequence diagram of natural gas flow for natural gas wells and gas storages, and Figure 9a shows the results of the dispatch. In case 2, P2G was considered in IPGES, and its total dispatching cost, wind abandonment amount (wind abandonment amount of case 1 is 1106 MW; wind abandonment amount of case 2 is 46.5 MW), carbon emissions, and carbon tax cost all decreased compared with case 1. As shown in Figures 7 and 8, P2G works during the wind abandonment period (1-7), using H\({}_{2}\)O and CO\({}_{2}\) as raw materials, converting the abandoned wind power into natural gas and injecting it into the natural gas network. It can be seen that the introduction of P2G can improve the wind power accommodation capacity and reduce the carbon emissions of the system, thus reducing the wind abandonment penalty cost and carbon trading cost. Figure 6: The structure diagram of the simulation example of IPGES. (2) The impact of different carbon trading mechanisms on the carbon emissions of IPGES  
Analyze the situation of the same system under different carbon trading mechanisms(CT), and divide it into the following three cases, the benchmark carbon price of each case is set to 20 $/t, other carbon trading parameters are shown in Appendix A Table 14. P2G is considered in all cases. Case 3, traditional unified carbon trading mechanism(UCT); Case 4, ladder-type carbon trading mechanism(LCT); Case 5, reward and punishment ladder-type carbon trading mechanism(RPLCT).  
Figure 8: Gas flow.  
Figure 7: Power output of each unit.  
Figure 9: Dispatching results of each case.  
Figure 9b shows the dispatch results of the systems under different CT. It can be seen that under the same benchmark carbon price, compared with UCT, the system carbon emission under LCT is reduced by 5429 ton; compared with LCT, the system carbon emission under PRLCT is reduced by 1562 ton.  
In case 3, the total dispatch cost of the system considering CT is the lowest, but the carbon emission control of the system is not obvious. Under the carbon price of 20 $/t, it fails to achieve a good emission reduction control effect, and it can achieve a higher carbon emission control effect by further increasing the carbon price. Comparing the results of case 4 and case 5, both LCT and RPLCT can suppress the carbon emissions of high-carbon emission units. The latter can also further stimulate the more output of low-emission units in the system, such as gas-fired units, to indirectly weaken the dependence of the system on high-emission units, that is, by increasing the output of gas-fired units to suppress the coal-fired units, so as to reduce the carbon emissions. The total dispatch cost, carbon emission and carbon trading cost of IPGES under RPLCT are all lower than those under LCT. Due to the introduction of the incentive coefficient, the carbon emission reduction characteristics of P2G can benefit from the reward and punishment ladder-type carbon trading. Under the lower carbon trading cost, the system can achieve better carbon emission reduction effect, indicating the effectiveness of RPLCT in the low carbon economic dispatch of IPGES. Figure 10 shows the electrical output of various types of units and the input electrical power of P2G in each case.