Week 7 State of charge estimation

1.

Simulating the 3 test cases from harness dashboard :-

Here we have to simulate three test cases from the harness dashboard which was provided in the above link . The battery model harness dashboard looks like :-

1 . Now we gave the test sequence as 1 then we found some output in scope -

When simulation will start then the model will be in driving condition and after some times its starts charging and in stand by mode.

It shows no error as all above shown is green indication.

SCOPE :-

From this plot we can see that the vehicle is initially in driving state and charging was done till 90% . After charging it reaches to standby mode. It can be seen in BMS state plot. Battery temperature increases in driving and charging. Currentplot shows the value of current supplied to vehicle while driving SOC decreased up to 50% in driving condition and it was increased while charging.

2. Now by changing the test sequence to case two.

SCOPE :-

From the above graph , a fault condition occured in second case . So even after charging was started, the SOC didn't increased. It continues to decrease.

3.Test case three

This condition has only one phase and that is charging .

SCOPE:-

Here we can see that the SOC reached 100% in charging and remained in stand by mode. Cell temperature also decreased when stand by mode is achieved. Only charging takes place here.

2.

Coulomb counting :-

It measures the discharging current of a battery and integrates the discharging current over time in order to estimate SOC. It is done to estimate the discharging current and previously estimated SOC values. But there are several factors which will affect the coulomb counting method :-

1.Temperature

2.Battery pack

3.Life cycle

4.Discharge current

To improve the coulomb counting method , a new technique is performed and that uses the corrected current value to improve accuracy estimation . This corrected current is the function of discharging current .

The experimental results shows that the accuracy of modified coulomb counting method is superior than conventional coulomb counting method.

BMS System :-

By clicking on the BMS ECU we get a subsystem and then we go to SOC estimation subsystem.

Then we found

Now by clicking on to the coulomb block we get this

> This system does the estimation by coulomb counting method.

> Advantage of this is it is simple and very low cost.

> Temperature and current from the battery is given as input.

> Current input is given to an integrater where it is integrated with respect to time.

> Hence SOC is estimated.