Week 7 State of charge estimation

EV LIVE BATCH -16:

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

SOLUTION :

BATTERY MANAGEMENT SYSTEM (BMS):

• it is an electronic system that manages a rechargeable battery (cell or battery pack)
• such as by protecting the battery from operating outside its safe operating area, monitoring its state ,calculating secondary data ,reporting that data, controlling its environment ,authenticating it, and balancing it

TEST HARDNESS:

• To create a test - specific simulation environment for model we use a test hardness method
• here,we isolate the individual blocks for unit testing and add inpits,verification logs, and dashboard blocks, and perform closed looptesting by adding physical plant models to the test harmness test

DASHBOARD:

• Lamps to indicate fault state high temperature ,over current ,charging voltage ,sensor operation ,low temperature ,and voltage
• if any fault in these read induction will intimate us and all in good condition indicated by green indication
• Manual varient
• Rotating switch for manual varient changes while running simulation
• BMS test sequence state request to provide state request commands
• Test sequence varient

BMS CLOSED LOOP:

• This is main block consists of two subsystem BMS ECU and plant units
• the plant output from the plant unit is given as input to BMS ECU as the input feedback loop the state request is given to the BMS ECU unit
• the final output from closed -loop model are BMS input ,BMS output ,BMS information
• In the BMS ECU unit the current power limit calculation are done used in state machine block soc estimation cell balancing

TO run three test cases from the hardness dashboard of closed loop BMS control,we have to test three cases for this model

TEST CASE :01

Here from the above test sequence editor figure, the following changes have been made:

• Driving for the first 3000secs
• After 3000sec starts balancing operation occur for the next 1000secs
• then charging and balancing occur for the next 5000sec .4 after that the sequence post charge , a balancing operation occurs till the end of the simulation period

OUTPUTS:

The lamp indication is showing green for the overall simulation period showing that there are no fault occurs the sequence..

OBSERVATION FOR ALL TEST CASE:

CELL VOLTAGE AND PACK CURRENT:

• The cell voltage varies from a maximum of 3.9v and reduces to 3.05v as cut-off voltage up to 9000sec entire capacity drained at 9000sec
• the pack current discharging up to a maximum 70A and slight charging occurs during the overall drive

CELLTEMPERATURE :

• Here cell 1 lesser temperature varient from 288k to approximetely 302.2k cell 6 in having a temperature vary from 288k to approximetely 322.5k
• the cell temperature is slightly reduced in between drive mode as this duration .

BATTERY MODULE STATE:

• The entire sequence is performing in drive mode as small duration of stand by modes are plot in this plot simulation 1000sec command is given as drive mode but in actual practical situation standby mode are present battery current drains by other small

SOC:

SOC of module here the soc reduces from 80per to 0per in the entire drive mode

TEST CASE 3:

OBSERVATION:

BMS STATE:

The entire battery pack sequence is operating in charging mode

CELL TEMPERATURE:

the cell temperature continues to increase heat up to full charge and after that, the temperature gets started to reduced to ambient from the resulting plot to the temperature starts to decrease after the full charger.

CELL VOLTAGE AND PACK CURRENT:

• Initially cell 2 voltage rises from 3.9v to a maximum of m 4.2v and stabilized to 4.15v cell rise from 3.85v to 4.1v and stabilized to 4.08v
• the battery pack current raising from 0A to 30A and starts to reduce to 2.5A gradually at the end to full charging 2000sec
• at 2000sec the pack is fully charged to 100per after full charge current flow will be cutoff

SOC :

The pack SOC gets charged at 2000sec and remains at full charge of the sequence .the actual of charge is around 93per shown as full charge

CELL BALANCING:

cells 6 and 2 statrs to balance concering cell 1 and cell are trying to balance at the end of the simulation

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

SOLUTION:

COULOMB COUNTING:

• The coulomb counting method measure the discharging current of a battery and integrates the discharging current overtime in order to estimate soc
• coulomb counting method is done to esmitate the which is esmitated from the discharging current,and previously esmitated soc values
• it works by integrating the active flowing current (measured in apms ) overtime to derive total sum of energy entering the battery pack
• its produces a capacity that is typically measured in amp-hour

• its done to esminate the soc which is estimated from the discharging current (I) and previously estimated soc values soc(t-1)
• soc is calculated by the following equation :
• SOC=soc(t-1)+[I(t)/Qn]*dt

WHERE ,

SOC= State of charge at the estimated time

i(t)=discharging current

Qn= nominal battery capacity