*4.2. Battery Selection Model*

0.0079

 0.0000636

The lower values of all statistical performance criteria from Table 6, quite close to those from Table 5, justifies without doubts the validity of Simscape model. Based on the information collected from both Tables 5 and 6, a rigorous analysis reveals that the both models perform similarly and are suitable for building highly e fficient and accurate SOC estimatiors in Part 2. However, an appropriate criterion to compare several candidate models is a hard task for any analyst since some criteria can be disadvantaged by the "model size of estimated parameters while the others could emphasis more on the sample size of a given data" [27]. As a general remark, it can be said that the Simscape Li-ion battery model excels in the following features: simplicity, friendly user-interface, and being fast to implement in real-time.

Also, the battery parameters can be extracted very easily for di fferent chemistry and specifications, and the model is much more realistic in terms of the values of physical model parameters. However, a comparison of SOC performance, more relevant for highlighting the strengths and weaknesses of both models, is provided by the validation results of the MATLAB simulations shown in Figures 13b and 21a,b for the same FTP-75 driving cycle profile and equal SOC value estimated by the ADVISOR simulator 3.2. Following this test, excellent SOC accuracy is observed for both models. Valuable information on SOC accuracy is extracted from residual SOC errors generated in MATLAB and analyzed in Figures 15 and 21b. The results of the MATLAB simulations show a residual SOC error in the case of the 3RC ECM Li-ion battery model in the range [−1, 1, 0, 4], and the percentage of residual SOC error is below 1.2%. In contrast, for the Simscape model, the percentage of residual SOC error is less than 1.4%, compared to the typical value of 2% reported in the literature for similar applications. The features mentioned above and in addition to the SOC percentage of excellent residual error, much lower than the typical value of 2% reported in the literature, are sometimes even better, strongly recommending the choice of the Simscape model for a wide variety of HEV and EVs applications. In conclusion, these results are encouraging for the next step to develop the most suitable SOC estimators in Part 2. The results of the MATLAB simulations will confirm that all three SOC estimators work better for a design based on choosing the Simulink model, rather than adopting 3RC ECM battery mode, even if the accuracy performance of both battery models is equally sensitive.
