Week 7 State of charge estimation

I AM LIVE BATCH-16 STUDENT

1.Simulate the 3 test cases from harness dashboard and write a detailed report on the results

SOLUTION:

The Closed Loop Harness Dashboard model by Mathworks is as shown below:

To select one of the 3 test conditions, it can be selected via the Test Sequence Variant block which allows you to select which test
needs to be simulated. The first variant was selected initially for the simulation which can be seen below.

As we look at the test variant as shown below, it states that at the start of the simulation the model will be in the driving condition, thereafter, after 3000 seconds it will be in balancing mode, after 1000 seconds it will be in charging and balancing mode and after5000 seconds it will be in post charge balancing mode

After simulating the model for 20000 seconds as given default

as we can see there is no fault or errors in the model:

1. It can be observed from the plot that the vehicle is initially in the driving state and charging was done till 90%.
2. After the charging mode it reaches to the standby mode which can be seen from the BMS state plot.
3. From the Cell temperatures plot it is observed that the battery temperature rises in driving and charging.
4. The battery voltage was increased to 4.2 V while charging.
5. The current plot shows the current value supplied to the vehicle while driving.
6. The SOC was observed to be decreased around 50% in driving condition, which increased while charging.

second variant condition:

The second variant simulates the below shown conditions

Initially it is the driving condition and after 10000 seconds there is charging condition.

third condition:

Looking at the condition below for third variant of the simulation. It is just the continuous charging condition from the start till the end of 20000 seconds of simulation.

1. From the above simulated 3 variants of the simulation carried out it was observed that,
   In the first simulation all three conditions were simulated such as driving charging and the stable state hence the charging and discharging were observed and in the end the constant 100% SOC was observed because of the standby state of the vehicle.
2. In the second simulation it was just the discharging as the SOC dropped to 0% in the driving state within 8600 seconds and the charging state was not achieved at 10000 seconds.
3. In the third simulation, only charging was observed for the first 2000 seconds and the SOC remained at 100% constant for the next 18000 seconds.

2.What is coulomb counting? Refer to the above model and explain how BMS implements coulomb counting for SOC estimation ?

SOLUTION:

1. Coulomb counting is a technique used to track the State of Charge (SOC) of a battery pack.
2. It works by integrating the active flowing current (measured in amps) over time to derive the total sum of energy
   entering or leaving the battery pack.
3. In coulomb counting measuring the current (total charge in coulomb) flowing in and out of the battery. For this SOH
   is required. SOC accuracy also decreases if SOH is not accurate
4. Change in SOC = Charge pumped in or out of battery / (Total capacity * SOH)
5. SOC (new) = SOC (old) + Change in SOC
6. Charge (Q) = Current(I) * Time(t)

Algorithm of Coulomb Counting Flowchart

below is subsystem of coulomb counting

1. This system carries out the estimation by coulomb counting equation mentioned earlier.
2. The main advantage of coulomb counting is that of its simplicity and low computational cost.
3. Temperature and current are taken as input from the battery.
4. Current signal is given to the gain block and the temperature is given to capacity as it varies according to the temperature.
5. These inputs are given to integration where current will be integrated wrt time.
6. This output is given to another block where it is divided by capacity and henceforth the SOC is estimated.