Week 7 State of charge estimation
Objective:-
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)
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Solutions:-
1.simulate the 3 test cases from the harness dashboard and write a detailed report on the results
we are going to begin the test case by opening the matlab and downloadable content from the reference documentation project which skill-lync has provided
below shows the steps how the steps are involved in the setup of the ECU block with the battery management system.this is the beginning of the setup where we setup the matlab and open project.
This is what ECU looks like in the BMS susystem of the project.this is where we are to understand how the battery performance works.
and if we look inside the subsystems of ECU we are going to see a flowchart of commands that governs the flo of process within the BMS.
The BMS model consists of a BMS ECU (electrical control unit) and a plant.the control unit with its various monitoring and control algorithms is connected to a block with the representation of the battery pack and associated circuitary and peripherals.this model containts two versions of the battery pack a small one with just 6 cell series.and a larger 16-module pack,each module containig a 6-cell series string.the architecture is 6s-1p and 96s-1p packs,respectively.
below is the base setup and interior block of plant block where the simulation is running with electrical output within the systems.
It consists of 3 cases where when green light indicates the simulation is running smooth.the dashboard also helps in determining the fault states and other parameters.
after running the simulation from 20000 secs we get the following output.
this is where we get our 1st results into play
As you can see above that the 3 tests cases ran through exactly as above where the test sequences were selected manually before runnnig the simulation.and the resultant is what we are going to see down below.
we observe that voltages are changing as the current is flowing in and out of the cell.because the system goes on standby mode graphs are showing a charging state during the constant current phase.as the cell voltage is too high.imbalance with a range of 3.1 to 3.9 volts for the time period.
2. what is couloumb ? Refer to the above model and explain how BMS implements coulomb counting for SOC estimation?
To determine available capacity ,coulomb counting relies on the integration of the current drwan from and suplied to a battery over time as given by
where I is the current and efficiency during charge and discharge operations [4].coulomb counting is advantageous in terms of a simple structure and its ease of implementation.however,some problems make it difficult to accurately estimate batttery SOC by coulomb counting.because battery capacity and efficiency are significantly influenced by operating temperature and current direction,these factors should be considered to correct for battery SOC.sensor accuracy is also important because accumulated errors can lead to a drift in the estimated battery SOC.
Flow chart of coulomb counting:-
