*5.2.1. State estimation validation*

Two cases are studied in the validation procedure. The initial SOC is assumed to be given for the SOC estimation method in the first case. The estimation results in this case are given in

**Figure 16.** The configuration of the battery test workbench.

*5.1.3. Driving cycle test*

104 New Applications of Electric Drives

ing cycle.

**Figure 15.** Testing results with UDDS driving cycles.

**5.2. Experimental results and analysis**

*5.2.1. State estimation validation*

the battery test workbench is shown as Figure 16.

UDDS and US06 drive cycles are applied to the battery. The magnitude of the current profile has been scaled down with respect to the battery features. The current profile of the UDDS

**Figure 14.** Different driving cycles: (a) UDDS driving cycle; (b) US06 driving cycle; (c) current profile of a UDDS driv‐

The widely used UDDS current profile is introduced to simulate the drive cycles of an EDV. The ampere counting method is utilized to calculate the reference SOC. The configuration of

Two cases are studied in the validation procedure. The initial SOC is assumed to be given for the SOC estimation method in the first case. The estimation results in this case are given in

drive cycle is given in Figure 14, while the testing results are shown in Figure 15.

Figure 17. The SOC diverges a little in the beginning, since the model is not so accurate. Then, the estimated SOC quickly converges to and keeps on tracing the reference SOC. The results given in Figure 17 show that the SOC estimation method could estimate the SOC with small errors when the initial SOC is given.

The initial SOC is assumed to be unknown in the second case, as shown in Figure 17. In this case, the reference SOC is actually 100% but the initial SOC of the SOC estimation method is assumed to be 60%. It is clear from the figure that the estimation error is 40% at first. Then the estimation errors reduce quickly, and the estimated SOC converges to the reference SOC. After the steady state, the estimated SOC traces the reference SOC with small errors. The results indicate that the initial SOC error could be compensated by the proposed SOC estimation method and the estimated SOC will converge to the reference SOC quickly.

**Figure 17.** SOC estimation results when the initial SOC is known or unknown.

From the discussions above, it can be concluded that the SOC estimation method works well for li-ion batteries. The SOC estimation errors are small even with a simple battery model, compensating the modeling errors and modeling uncertainties.
