## Case Study and Results  
### Charging Schedule Optimization  
The buses were strictly launched according to the operation schedule, and the departure interval varied in different periods and routes. The minimum time interval was 15 min. Through the departure characteristics, energy consumption, and running distance, the maximum running loops under the safety SOC (30%) threshold can be developed. Using line H55 as an example, the energy consumption per kilometer was 0.854 kWh, the loop length was 9 km, and the electricity quantity of on-board battery was 119.62 kWh. We could see that it was practicable for a PEB running 10 loops with the on-board battery pack on line H55 from Equation (26). To check whether the residual energy was above the safety threshold, Equation (27) is used.  
\[N_{Mloop\_H55}=\frac{E_{battery}\times 70\%}{E_{\text{cos}t\_H55}\times L_{H55}} \tag{26}\]  
\[SOC_{H55}=\frac{E_{\text{cos}t\_H55}\times L_{H55}\times N_{loop\_H55}}{E_{ battery}} \tag{27}\]  
where \(N_{Mloop}\) is the maximum running loops of one of the PEBs of line H55, \(E_{battery}\) is the electricity of the on-board battery, and \(L_{H55}\) is the length of line H55. \(N_{loop\_H55}\) is the number of decided running loops, and \(SOC_{H55}\) is the energy consumption rate of the on-board battery. All of the results are shown in Table 6.  
The fast-charging of PEBs usually uses the constant current stage. In order to simplify for calculation, the monthly mean charging power is used as the nominal optimal charging power. The whole charging electricity of one month was 157,501.8 kWh, the charging duration was 41,382 min, and the mean charging power was 228.36 kW from Equation (28), setting 228 kW as the calculation value to ensure a complete charging.  
\[P_{ave}=\frac{E_{month}}{T_{month}}\times 60 \tag{28}\]  
where \(P_{ave}\) is the average charging power, and \(E_{month}\) and \(T_{month}\) are the monthly electricity and charging duration, respectively.  
Through the optimization, the charging schedule was obtained, as shown in Table 7. The letters A to G are the labels of the buses on different bus lines, and the numbers in the crossing of the row and column are the charging orders when PEBs return to the station.  
According to the optimized charging sequence, the corresponding charging durations will be decided. The obtained optimized charging load is shown in Figure 5, where the peak charging power was significantly decreased at only 912 kW. As the simulation charging power of the stick was 228 kW, the number of sticks charging synchronously was four, which was obviously reduced when compared with the original seven sticks. This means that the investment may be cut in half by the charging sequence optimization.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Line No.** & **Goal** & **Length** & **Suitable** & **Distance** & **Total ele.** & **SOC Cost** \\  & **Loops** & **(km)** & **Loops** & **(km)** & **Cost (kWh)** & **(\%)** \\ \hline H55 & 9(10) & 9 & 10 & 90 & 76.86 & 64.25 \\ H56 & 10 & 12 & 7 & 84 & 72.16 & 60.32 \\
863 & 5 & 27 & 3 & 81 & 71.77 & 60.00 \\
864 & 4(5  
The purchasing electricity fee is shown in Table 8. This mode could shift the daytime load to the night and made good use of the TOU electricity prices as shown in Table 9. The electricity cost saved was 1544.7 CNY (37.1%). Furthermore, the peak charging power declined from 1601.7 kW to 912 kW, a reduction of 690 kW (43.07%). The basic capacity cost of the transformer can be reduced by about 736 CNY/day when compared to the original peak charging power. The total cost saved was up to 2280.7 CNY/day.