Week 7 State of charge estimation

BMS plant

Bms Software

State Machine

the entire plant of Bms will be shown

We need to simulate the Test case in 3 Scenes to get the output

1)Changing the variable to balancing

here the battery will be charged but differences in each cell could be seen so we need to simulate the scene in Simulink.

here these are the interference are

Driving for the first 3000 Seconds

3000 seconds it will start to balancing option will happen for next 1000 second

then charging will happen for the next 5000 seconds

After that post charming will be happening in this

The results of the scene1 are

1 )Cell_Voltage:-Parameter is cell voltage as we are set to balancing fro the first segment that from 0 to till it will charge and variation can be seen and it is will reach its maximum cell voltage as shown in the graph and it is open cell voltage.

2)Cell_Tempraeture:-There 6 cells that will have various temp as the result of voltage and current into it. The cell with maximum temp will have maximum voltage. And the cell with minimum voltage will have a minimum temperature.

3)SOC:-The soc depends on temperature and voltage at the cells. So the maximum cell voltage will have maximum Soc and minimum SOC will have minimum votage.

4)Pack current:-This is negative that it is charging and after this will move into positive that the vehicle will move. Then it is in rest.

5)BMS Status:-It has 3 states Driving, Charging, and Standby. so this will rise a ticket like how BMS will work and all.

6)Bal Current:-This current will work on a different principle. All cells need to have the same current and this will vary upon different BMS all. So after charging this will work.

2)Changing the variable to Driving mode.

1 )Cell_Voltage:-cell voltage will decrease and the reason we need to use the energy from cells.

2)Cell_Tempraeture:-.here this will rise from one value to another value and this will happen in case of discharge.

3)SOC:-Will be decreasing and cells are discharging.

4)Pack current:-Will have some value of pack current and it will start to decrease and will be at zero then will be increasing.

5)BMS Status:-Driving mode only.

6)Bal Current:-Will be zero.

3)Changing the variable to Charging

1 )Cell_Voltage:-cell voltage will increase from cut off level to the maximum level.

2)Cell_Tempraeture:-Her this will have a spike and then will be decreasing.

3)SOC:-Will be increasing and reach the maximum value.

4)Pack current:-Will be having a spike and at zero.

5)BMS Status:-Charging mode only.

6)Bal Current:-only 1 cell needs to have balanced.

2)

So coulomb counting is a method to estimate the SOC of any battery. The Coulomb counting method measures the discharging current of a battery and integrates the discharging current over time in order to estimate SOC. Coulomb counting method is done to estimate the SOC(t), which is estimated from the discharging current, I(t), and previously estimated SOC values, SOC(t-1). SOC is calculated by the following equation:

`SOC=SOC(t-1)+(I(t)divQn )*deltat`

But there are several factors that affect the accuracy of the Coulomb counting method including temperature, battery history, discharge current, and cycle life

So they have come up with these solutions Modified Coulomb Counting Method

To improve the Coulomb counting method, a new technique called the modified Coulomb counting method is proposed. The modified Coulomb counting method uses the corrected current to improve the accuracy of estimation.

The corrected current is the function of discharging current. There is a quadratic relationship between the corrected current and discharging current of the battery. By the practice of experimental data, the corrected current is calculated by the following form:

`Ic(t)=k2I(t)^2+k1I(t)+Ko`

wherek2,k1,k0, and are constant values obtained from the practice experimental data.

In modified Coulomb counting method, SOC is calculated by the following equation:

`SOC(t)=SOC(t-1)+(Ic(t)div Qn)*delta t`

The experimental results show that the accuracy of the modified Coulomb counting method is superior to the conventional Coulomb counting method

So here in this care, we need not wait for K2, K1, or K0 so we are going with these steps.

we agree to get the current from the battery pack

Temperature also from the battery pack

for current we will be creating a gain value from our theoretical value and for temp, we need to create a 1D lookup table from the data.

we need to divide both the values

after dividing the value we need to perform the numerical integration for this.

and the output we will be having a SOC from zero to 100 in percentage.