## 3 Results
### Analysis and Synthesis
#### 3.1.6 Simulation Results  
Reviewing the analysis of the selected works, it is clear that the validation of the proposed EMSs was carried out against the global optimum represented by the DP results. Apart from this, these EMSs are often compared to common RB EMSs that represent the strategies currently implemented in commercial PHEVs. However, from the proposed selection, there are a few works that neglect this last comparison that would be interesting for the purpose of this review [16; 22; 42; 44; 46; 49; 50; 51]. To fulfil this gap, the data provided in these works related to the characteristics of the vehicle model were used to develop vehicle models and carry out simulations of the corresponding driving cycles in FASTsim. This software uses an RB EMS commonly used by commercial HEVs described in Appendix A. In Figures 3-6, some of the simulations results obtained are shown. Figure 3 shows the results corresponding to [46]. Figure 3a shows the evolution of the battery SOC for 10 NYC-HEV driving cycles. It can be seen that the SOC decreases cycle by cycle until reaching a minimum level (around 30%) at the middle of the simulation. Then, it remains at around 30% until the end of the simulation. In the original results [46], this level of SOC was reached at the end of the 10 driving cycles. This is consistent with the results of other works (e.g., a previous work of this team [52]) that showed that the SOC trajectory descended more abruptly to the final level for classical RB EMSs such as CDCS than for optimized EMSs, which showed a smoother descent. Figure 3c,d, which show the SOC evolution and the powers of electric motor and ICE, respectively, are also included to show the performance of the RB EMS in detail. They show these variables during 1 NYC-HEV. With regard to Figure 3c, apart from the SOC, two limits related to the EMS operation are presented (see Appendix A): the \"Regen. buffer\" (regenerative buffer) is the upper SOC limit that maintains room for regenerative braking based on the vehicle speed and mass; and \"Accel. buffer\" (acceleration buffer) is the lower SOC limit that ensures battery energy for accelerating at slower speeds. When the SOC reaches the \"Regen buffer\" limit (second 800 in Figure 3c), the EMS prioritizes the use of the battery  
for accelerating to discharge it and increase its capacity for absorbing the power from regenerative braking. Correspondingly, when the SOC reaches the \"Accel buffer\" limit (around second 4000 in Figure 3a), the EMS avoids excessive use of the battery for accelerating and prioritizes the use of ICE and, therefore, battery SOC depletion is avoided. Apart from this, the subplots of Figures 4-6 are organized as follows: (a) represents the battery SOC for the corresponding driving cycle (see the titles of the figures); (b) represents the powers of the battery and the ICE for the corresponding driving cycle; and (c) represents the cumulative equivalent gasoline consumption in gallons for the corresponding driving cycles. Figure 3: FASTsim simulation results for the HEV of [46]. (**a**) Battery SOC after 10 NYC-HEV cycles; (**b**) cumulative equivalent gasoline consumption in gallons for 10 NYC-HEV cycles; (**c**) battery SOC for one NYC-HEV cycle; (**d**) powers of the battery and the ICE. Figure 4: FASTsim simulation results for the HEV of [44] for LA92 cycle. (**a**) Battery SOC; (**b**) powers of the battery and the ICE; (**c**) cumulative equivalent gasoline consumption in gallons. Figure 5: FASTsim simulation results for the HEV of [42] for NEDC cycle. (**a**) Battery SOC; (**b**) powers of the battery and the ICE; (**c**) cumulative equivalent gasoline consumption in gallons. In the simulations shown in Figure 4 corresponding to the HEV of [44] for the LA92 driving cycle, it can be clearly seen the effect of the battery SOC reaching the lower limit defined as \"Accel buffer\". When this occurs, the HEV is propelled by the ICE and the battery power is zero or negative (regenerative braking)--see Figure 4b.