Week 7 State of charge estimation
1.Simulate the 3 test cases from harness dashboard and write a detailed report on the results
2.What is coulomb counting? Refer to the above model and explain how BMS implements coulomb counting for SOC estimation ?
Hint :(Download the file from the link and go to SOC estimation model-ECU block)
The CLosed loop harness Dashboard model by Mathworks is shown:
Step-1 :
Open The model in matlab
The follwing window will open.
Step-2: Click on Test Sequence variant block.
Choose test case as 1. as this will run the case 1 test.
As we can look at the tedt variant as shown below, it states that at the start of the simulation the model will be in the driving condition, after 3000 seconds it will be in balancing mode.
after 1000 seconds it will be in charging and balancing mode and after 5000 seconds it will be in post charge balancing mode.
after simulating the model for 20000 seconds as given default.
Here we can see all the lights have turned greenas there no error in the model.
Result:
Observation:
- It can be observed from the plot that the vehicle is initially in driving state and charging was done till 90% . After the charging mode it reaches to the
standy mode which can be seen from the BMS state plot it is observed that the battery temperature rises in driving and charging .
Case 2:
initially it is the driving condition and after 10000seconds there is charging condition.
Result:
It was Observed from the plot that the battery discharges completely in 8692 sseconds and the vehicle does not achived at 10000 seconds.
Hence the vehicle comes to standy condition.
Case 3:
Result:
- Looking at the plot it can be seen that the battery starts charging and SoC starts increasing from beginning to around 2000 seconds until 20000 seconds.
The peak current plot drops from 0 to 2000seconds.
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2.What is coulomb counting? Refer to the above model and explain how BMS implements coulomb counting for SOC estimation ?
coulomb counting
The Coulomb counting method measures the discharging current of a battery and integrates the discharging current over time in order to estimate SOC [20].
Coulomb counting method is done to estimate the , which is estimated from the discharging current,
, and previously estimated SOC values, . SOC is calculated by the following equation:
Steps involved in coulomb counting are shown pictorially as shown below:
The coulomb counting block can be observed on the top of the model. Where the coulomb counting eas carried out.
the model for the same can be seen below
This system carries out the estimation by coulomb counting equation mentioned earlier.
The main advantage of coulomb counting is that of its simplicity and low computational cost.] Temperature and current are taken as input from the battery.
Current signal is given to the gain block and the temperature is given to capacity as it varies according to the temperature.
These inputs are given tointegration where current will be integrated with respect to time . this output is given to another block where it is divided by capacity and hence the SoC is calculated.
Conclusion:
- The 3 test cases from harness dashboard were simulated and discussed succesfully along with the coulomb counting done by BMS for SOC estimation.