## 4 Simulation Results and Discussion
### Comparative Validation of DA-ECMS  
The DA-ECMS was verified under the WLTP. The result of the hybrid energy source power allocation in this strategy is shown in Figure 15. The trajectory of the fuel cell stack output power is shown and compared with the corresponding changes under the A-ECMS in Figure 16. The FCHEV power demand was low in the first 780 s of the test conditions. At this time, the battery was the main source of the power output, while the fuel cell stack was running in a lower-power state, basically in the idling state. In order to reduce the fuel cell degradation in the idling operation, the DA-ECMS increased the fuel cell stack output power and stabilized it at 8.3 kW, while charging the battery at the same time. Compared with the results for the A-ECMS, the fuel cell stack output power fluctuations and peaks occurred less frequently in this strategy, which helped prevent fuel cell performance degradation due to frequent load changes. In the second half of the test conditions, the FCHEV power demand rose, and the fuel cell stack supplied the main power output. By precisely adjusting the power distribution, the DA-ECMS effectively avoided the operation of the fuel cell under high-power conditions, which prolonged the fuel cell lifetime. Figure 14: Equivalent hydrogen consumption curves under ECMS and A-ECMS. Figure 15: Hybrid energy source power allocation result under adaptive equivalent consumption minimization strategy considering performance degradation (DA-ECMS). Since the WLTP test duration is 1800 s, two WLTP processes were selected to form a combined condition to simulate the voltage degradation of the fuel cell stack under different strategies for 1 h, and the test result is shown in Figure 17. The voltage degradation caused by the poor operating conditions of the fuel cell stack under the DA-ECMS was 3.679 mV, which was 1.322 mV lower than that of the A-ECMS. Only the voltage degradation of the starting part in the start-stop condition is shown in the figure. After adding the voltage degradation caused by the stopping part, the total voltage degradation was 6.425 mV, which was 17.1% lower than that of the A-ECMS and effectively slowed down the performance degradation of the fuel cell. The SOC trajectory and the C-rate of the battery under the A-ECMS and the DA-ECMS are shown in Figures 18 and 19, respectively. To avoid the prolonged inefficient operation of the fuel cell and frequent load changes, the DA-ECMS increased the fuel cell stack output power and used the extra power to charge the battery, resulting in an overall slightly higher SOC than that under the A-ECMS. Compared with the A-ECMS, the DA-ECMS had a smaller change in the C-rate of the battery, which effectively slowed the performance degradation of the battery. Figure 16: Fuel cell stack output power change trajectory under A-ECMS and DA-ECMS. Figure 17: Fuel cell stack voltage degradation under A-ECMS and DA-ECMS. The A-ECMS and DA-ECMS equivalent hydrogen consumption curves are shown in Figure 20. The DA-ECMS not only pursued economy in power allocation but also considered the hybrid energy source's long-term stability to ensure the power system's continuous health and efficient operation. As a result, the final equivalent hydrogen consumption of the DA-ECMS reached 359.5 g, which was an increase of 2.5% compared with that of the A-ECMS. The A-ECMS and DA-ECMS were simulated under different operating conditions, and the validation results are shown in Table 5. From the analysis of the data in Table 5, it can be seen that, compared with the A-ECMS, the DA-ECMS effectively improved the performance degradation of the hybrid energy source while sacrificing a small amount of fuel economy. Therefore, in contrast with A-ECMS, the DA-ECMS could balance the FCHEV economy and energy source durability, and it had good adaptability to the operating conditions. Figure 19: C-rate of battery. Figure 16.0 Equivalent hydrogen consumption curves.