## 5 Simulation and Analysis
### Analysis of Day-Ahead Optimization Results  
The day-ahead optimization uses the model proposed in Section 3.1, and the optimization results are shown in Figures 6-9, which present the output of each controllable resource in 24 h. Figure 6 shows the changes in OLTC tap positions and CB switching throughout the day. We observed that during peak hours, both OLTC and CBs are at higher positions to meet the voltage regulation needs of the distribution network. Figure 7 illustrates the active power and reactive power outputs and capacity ratio of the two VSPSHS in a day. These data indicate that during the peak load period, VSPSH is mostly working in generating and generating phase modulation, while during the low load period, VSPSH is mostly working in pumping and pumping phase modulation, making full use of the characteristics of VSPSH for peak shaving and valley filling, as well as frequency and voltage regulation, ensuring the safe and economic operation of the distribution network. Both VSPSH's storage capacities return to their initial states at the end of the day. Figure 8 shows the active power and reactive power output and capacity ratio of two BES in a day. We observed that BES1 and BES2 undergo four charge-discharge cycles within a day, within the allowed number of cycles, and both satisfy the daily operating capacity balance. Figure 9 displays the reactive power output of WT, PV, SVG, and GT and the active power of GT throughout the day. It is evident that the reactive power of WT and SVG fluctuates greatly, mainly because the WT's fluctuations are largely due to the reactive power being influenced by its active power output, while SVG2 experiences larger fluctuations because it is located at the end of the feeder line, leading the optimization algorithm to use SVG2 for compensating the branch's end to avoid long-distance reactive power flow. In contrast, the GT's output is relatively stable due to the higher number of controllable devices in its branch.  
Figure 5: Intra-day forecast values for wind, PV and loads.  
Figure 6: OLTC tap positions and CB switching at the day-ahead stage.  
After applying the day-ahead optimization model proposed in this paper, the states and outputs of each controllable resource in the distribution network in a day were obtained. From these results, it can be seen that each controllable resource has a reasonable output. The day-ahead optimization results can serve as the basic dispatching command for the distribution network in a day, ensuring the safe and economic operation of the distribution network in a day.  
Figure 8: Active power and reactive power output and capacity ratio of two BES.  
Figure 7: Active power and reactive power outputs and capacity ratio of the two VSPSHS.  
Figure 9: Reactive power of WT, PV, SVG and GT and the active power of GT.  
network. Then, during the intra-day phase, these values will be adjusted on a smaller time scale to account for the variability of renewable energy.  
Figure 10 shows the optimization results of VPSSH operation conditions considering or not considering generating/pumping phase modulation conditions in the day-ahead stage. We observed that without considering VPSSH phase modulation conditions [8], both VPSSHs perform pumping during low-load night-time and generating during high-load daytime. When phase modulation condition is considered, due to the large reactive load level and long branch length of VPSSH1 and VPSSH2 branches, reactive power compensation effectively reduces system losses. Therefore, VPSSH1 performs phase modulation from 6 to 13 and 18 to 24 h, while VPSSH2 does so from 4 to 15 h to ensure safe and economical operation of the distribution network. From this, it can be inferred that when considering phase modulation conditions, VPSSH can fully utilize its various states and make the most of its flexibility.