# Power-Split Hybrid Train Configuration Design Based on a Single-Row Star Row
## 5 Simulation Analysis  
Based on details regarding the track conditions and the speed requirements for the train, a simulation analysis was conducted using a known railroad operating route as the input.  
Figure 7 shows the effective fuel consumption rate of the engine obtained from the engine bench test. According to the operating point distribution of the engine in Figure 8a,b, it can be determined that the effective fuel consumption rates of an internal combustion engine train and the hybrid train are concentrated in the 200-250 g/kWh and 0-200 g/kWh ranges, respectively. This result shows that the hybrid train has a better fuel economy than the internal combustion engine train. Figure 8b,c show that the primary functions of MG1 and MG2 are driving and charging, respectively. When the train is moving quickly, MG1 can supply additional power to decrease the engine load rate and return the engine operating point to the economic zone. In order to keep the engine operating in the economic zone when the train is moving slowly, MG2 functions as a \"load\" by producing electricity to increase the engine load rate and decrease the backup power.  
Figure 7: Effective engine fuel consumption rate.  
Figure 9 shows that the effective fuel consumption rate of the designed hybrid train is less than 200 g/kWh during operation, which is consistent with the engine operating point distribution in Figure 8b.  
The battery operating parameters obtained from the simulation are shown in Figure 10.  
Figure 8: (**a**) Distribution of engine operating points of internal combustion engine trains. (**b**) Distribution of engine operating points of the hybrid train. (**c**) Distribution of the MG1 working points of the hybrid train. (**d**) Distribution of the MG2 working points of the hybrid train.  
The battery input and output power results were divided into 11 intervals according to the train operating stations as shown in Figure 10a, and each interval was divided into three states: acceleration, high-speed driving, and deceleration. The red dashed line serves as the dividing line between acceleration and high-speed driving, whereas the green dashed line serves as the deceleration line. The operating voltage and current of the battery are shown in Figure 10b,c, respectively.  
Several inferences can be drawn from Figure 10. Both the input and output power of the battery fall between \(-300\) and \(300\) kW, the working voltage is in the \(592\)-\(680\) V range, and the operating current is in the \(-441\)-\(507\) A range. When the battery operates at high power, the train is either in the acceleration or the deceleration state. As the train accelerates, the high-power drive motor from the battery must supply additional energy to maintain the power performance of the train. In addition, the acceleration process of the train includes a low-speed, high-load phase. During this phase, the battery output of the high-power drive motor can simply adjust the operating point of the engine to maximize the fuel efficiency; during deceleration, the high-power motor can charge the battery and increase the energy efficiency.  
According to Figure 10d, during hybrid train operation, the SOC decreases from \(100\%\) to \(65.7\%\). Additionally, the train has more stations and we expect a pure electric drive mode at startup, which requires more power from the battery; thus, we set the SOC balance point to \(60\%\) in the controller, and it fluctuates by \(\pm 6\%\).  
Figure 10: (**a**) Battery power during the simulation; (**b**) battery voltage during the simulation; (**c**) battery power during the simulation; (**d**) battery SOC value during the simulation.