## 6 Simulation Analysis
### Basic Data
#### 6.2.2 Scheduling Results  
To analyze the complementarity of different power sources, MECS scheduling was optimized for a typical day. On a typical summer day, the available outputs of HS and PV are high, whereas the available output of WPP is low. The situation is completely reversed for a typical winter day. Consequently, the MECS operation was optimized under different ESD modes. Figures 9 and 10 show the results under the OEE mode and LLC mode, respectively. In Figure 9, it can be seen that when the ESD operated in the OEE mode, the load demand was mostly satisfied by the TPP and HS on a typical summer day, and by TPP and WPP on a typical winter day. It should be noted that the PV was also a major power source with a power output of 1673 MW-h from 11:00 h to 15:00 h. The WPP was another major power source with a power output of 2638 MW-h from 16:00 h to 21:00 h. Moreover, since the load demand is greater for a typical winter day than that a typical summer day, TPP2 was always scheduled to have a power output of 5000 MW-h. Then, the ESD was scheduled to overcome the intermittency and volatility of the WPP power output without considering the limitations of the rated power. The total power output of the ESD discharge-charge  
Figure 8: The different objective values under the comprehensive objective function on typical days. Figure 9: The MECS scheduling results on typical days under the OEE mode: summer (**left**) and winter (**right**). was \(\pm\)1853 MW\(\cdot\)h on a typical winter day, i.e., \(\pm\)848 MW\(\cdot\)h higher than on a typical summer day. Overall, to satisfy the load demand and system operation constraints, the MECS takes advantage of the thermal-hydro-photovoltaic complementarity (or thermal-hydro-wind complementarity in certain periods) on a typical summer day and the thermal-wind complementarity on a typical winter day. When the ESD operated in the LLC mode, the power output was limited by the rated power, i.e., 100 MW, as determined by Equations (29)-(31). The total discharge-charge power of the ESD was \(\pm\)1100 MW\(\cdot\)h, i.e., \(\pm\)205 MW\(\cdot\)h lower, on a typical summer day, and \(\pm\)1200 MW\(\cdot\)h, i.e., \(\pm\)653 MW\(\cdot\)h, on a typical winter day than in OEE mode. It should be noted that the available outputs of the WPP and the HS were low in the valley period; therefore, TPP4 was scheduled to satisfy the surplus load demand with a power output of 200 MW\(\cdot\)h. The ESD was primarily discharged for economic benefit, whereas TPP2 was not scheduled in the peak period on a typical summer day. The optimal operation strategy should be chosen considering the specific situation. Figure 11 shows the complementarity indexes of MECS operation under different ESD operation modes. First, the influences of different ESD operation modes were analyzed. As the power output of the ESD in the OEE mode is higher, the outputs of the WPP and PV were also higher than in the LLC mode. Thus, when the MECS was scheduled on a typical summer day, the values of LTD and SPC were 5% and 6.78 MW\(\cdot\)h higher, and the coal consumption was 5.86 g/kW\(\cdot\)h lower in the OEE mode than in the LLC mode. When the MECS was scheduled on a typical winter day, the HS and TPP3 were required more to absorb WPP output more by providing a reserve service. This decreased the load tracking ability; thus, LTD was 8% lower in the OEE mode than in the LLC mode. Table 4 shows the power output results of MECS scheduling on a typical day. Subsequently, the results of the MECS operation on different typical days were analyzed. As the available WPP output is higher on a typical winter day, more reserve service was required from the ESD, TPP3, and TPP4. The actual curves of load demand and MECS power output exhibited strong fluctuations with high variance. Thus, on a typical winter day, LTD was 25% lower and 8% lower,  
Figure 11: The complementarity indexes of MECS operation under different energy storage devices (ESD) operation modes.