Week 7 State of charge estimation

Week 7 State of charge estimation

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

The above model shows the Closed loop harness model. It holds three test cases and has been executed in the below report. The model holds the Test sequence variant to change the test cases and Lamps are connected to report the execution.

Test Case 1:

Here, the test case 1 is been verified. The model has been ran for 20000 seconds and results are plotted.

The Test case is to execute the below criteria:-

• Driving for 3000 seconds
• Balancing for 1000 seconds
• Charging and balancing for 5000 seconds
• Post charge balancing for later.

The results are plotted for Cell voltages, cell temperature, SOC, Pack Current, BMS state. The Plot shows that the vehicle is initially in driving state. Then it was charging as Constant Current constant voltage mode. Then it was in standby mode. While driving , the battery reached the SOC of 45% and then while charging, it reached to 98%.

Test Case 2: Second case is Driving for 10000 seconds.

Here second case is to drive for 10000 seconds and later charged.

From the graph, shows that for 10000 seconds the system is in driving state and SOC of the system is continuously decreasing and temperature is increasing continuously.

Test Case 3: Condition is continuously charging.

Ths plot shows that system is continuously in charging mode, reaching 100% and stand down. Temperature increases while charging and reaching the stand point and deacreasing gradually.

2) Algorithms used for SOC and SOH Estimation are:

1. Coulomb counting, OCV
2. Kalman filter

Coulomb Counting:

The Coulomb counting method is associated with monitoring the input and the output current continuously. Since capacity is the integral of current with respect to time, by measuring the input and the output current, change in capacity or capacity degradation of a battery can be measured easily .During the estimation of SoC, at some random OCV and temperature ,modeling of cell characteristics was done by ANFIS. The assessment was done on the cell level instead of the pack level for better precision. The coulomb counting method, also known as ampere hour counting and current integration, is the most common technique for calculating the SOC. This method employs battery current readings mathematically integrated over the usage period to calculate SOC values given by

where SOC(t0) is the initial SOC, C_rated is the rated capacity, I_b is the battery current, and I_loss is the current consumed by the loss reactions. The coulomb counting method then calculates the remaining capacity simply by accumulating the charge transferred in or out of the battery. The accuracy of this method resorts primarily to a precise measurement of the battery current and accurate estimation of the initial SOC.

The above model shows the charge estimation for the SOC by using Coulomb Counting and Kalman Filter..

This the block diagram for Coulomb Counting.

The Current and Temperature is taken as an input to the model. The Current multiplied with gain and the Temperature has wide range of capacity , so given to the capacity block. The temperature and the Current are given to the integrator block and integrated with respect to time. Thus the SOC is analysed from the block diagram.