Project 2 Thermal modeling of battery pack
Theroy
The lithium ion batteries are widely used as energy source in different hybrid and electric vehicle. the operation characteristic of the batteries in such as vehicle are strongly depended on the operation temperature and there fore, with purpose to improve thsese characteristics a good thermal control system should be utilized.
the temperature of a lithium battery cell is important for its performance, efficiency, safety, and capacity and is influeneed by the environmemtal temperature and by the charging and discharging process itself. therefore a thernmal model of the battery is used in order to calculate and estimate the cell temperature.
Lithium-ion battery pack with fault was simulated a battery pack consisting of multiple series-connected cell in an efficient manner. it also shown how a fault can be introduced into one of the cell to see the impact on battery performance and cell temperature. for efficiency, identical series-connected cell are not just simple modified by connecting cell model in series instead a single cell is used, and the terminal voltage scaled up by the number of cells., the fault is represented by charging the parameter for the cell 5 fault subsystem, reducing both capacity and open circuit voltage and increseing the resistace values.
Construction of the circuit:-
A detail design of MATLAB simulink model for thermal modelling is given as :-
Cell 01 to 04 subsystem:-
cell subsystem basically consist of a thermal model and lithium cell 1RC block which calculate the temperature and theraml effect for cells and overall calculate for the battery pack.
the block which are inside athe cell subsystem are PS gain block which multiple the input physical single by a constsnt i.e Y = U* gain another block are voltage sensor and current voltage source.
the voltage senser represents an ideal volatge senser, that is a device that convert voltage measured between any electrical connections into a physical signal proportional to the voltage.
current voltage source represents an ideal voltage source that is powerful enough to maintain the specified voltage at its output regardless of the current passing through it. the output voltage is v = vs, where vs is the numerical value presented at the physical signal port.
Thermal model subsystem:-
The importnat block which is inside the thermal model subsystem are:
1. thermal reference: this block represents a reference point in a thermal network where the temperature is equal to absoulate zero.
2. Controlled heat flow rate source: this block repersent an ideal energy source in thermal network than can maintain a controlled heat flow rate is set by the physical signal port s. A positive heat flow rate flows from port A to portB.
3. Thermal mass: This block models internal energy storage in a thermal network. the rate of temperature increase is proportinoal to the heat flow rate into the material and inversely proportinoal to the mass and specific heat of the material
4. temperature sensor: this block measure temperature in a thermal network. there is no heat flow through the snsor the physical signal port T report the temperature difference acros the sensor. the measurement is positive when the temperature at port A is greater than the temperature at port B.
Lithium cell 1RC subsystem:
this block basically consist of capacitance value table which depends on an external physical signal input SOC and T. it is assumed that the capacitance value is slowly varying with time and hence he equation i = c*dv/dt holds.
Resistence value (R) table which depends on an external physical siganl inputs SOC and T.
Voltage value (EM) which implemenets the cell's main branch voltage source, and determines value for capacity (c) and state of charge (SOC). the defining equations depends on cell temperature, T.
Thermal behaviour and fault setup:-
lithium - ion cell one RC - Branch equivalent cricuit detail for 10 cells.
For cell 01 to 04
. Number of series - connected cells are 4
. initial temperature is 2999.1k
for cell 05 (fault setup) in this cell i have done some changes in electrical system of cell to that we can see the fault.
. number of series - connented cells are 1
. initial temperature is 299.1k
. capacity (a*hr) = capacity_LUL*0.95
. Em open - circuit voltage (volts) = Em_LUL*5
. R1 cell resistance (ohms) = R1_LUL*5
. C1 capacitance (farads) = C1_LUL*0.95
for cell 06 to 10
. number of series - connected cells are 5
. initial temperature is 299.1 k
here the output of one cell is connected with the SOC calculation whereas other output is connected with AC current source for cyclic charge/discharge profile.
the peak amplitudes set to 50 A for cyclic charge and discharge. A basic parameter of AC current source is as
the ideal Ac currenyt source maintain the sinusoidal current throught it independent of the voltage across its terminal. the output current define by i= 10*sin(2*pi*f*t+PHI), where 10 is the peak amplitude, f is the frequecy in Hz and PHI is the phase shift in radians.
The other block which are used in lithium ion batery pack are as:
. Temperature source: this block represent on ideal energy source in a thermal network that can maintain a constsnt absolute temperature at the port regardless of the heat flow rate.
This block is used for ambient temperature and which i set as 299.1 k or 25.95 c.
. Conventive heat transfer: this block heat transfer in a thermal network by convection due to fluid. the rate of heat transfer is proportional to the temperature difference heat transfer coefficient, and surface area in contact with the fluid.
Used 3 blocks for convection.
. Conductive heat transfer: - this block models transfer in a thermal network by conductive through a layer of material the reate of heat transfer is governed by fourier's law and is proportional to the temperature difference, material thermal conductivity, area normal to the heat flow direction, and inversly properational to the layer thickness.
the conduction is done from the 2 set of blocks, 1 block is used for 01-04 and other is used for cell 06-10.
for SOC calculation gain block, integrator and sum block with PS simulink convertor was used.
Results:- simulation based on different cell temperature
In this simulation, ambient temperature were set at 299.1k or 25.95c and another cell temperature are as follow;
color indication for cells
. Yellow colour - cell 4
. Purple colour - cell 5 (fault)
. Green colour - cell 10
Test - 1 (equal temperature)
we can see that there is much fluctuation in cell 05 due to fault.
calculation SOC
As we see that the battery is fluctuating every 301.200 seconds which depends upon the thermal behaviour of battery pack.
Conduction:
conduction is basically here heat flow rate (Q) and temperature difference (T) vs time.
Convention:
below groph highlight the heat flow and temperature difference by convection medium.
CYclic charge / discharge profile:
charge and discharge profile are depending upon current (i) and voltage (v) vs time. the cyclic charge and discharge were calculated at 50A peek amplitude.
test - 2 ( cell 5 minimum temperature)
As we can see that in cell 5 the temperature rice till 312 and it goes fluctuating from 313 k to 307 k and end at 311 k.
calculation SOC:-
As we see that the battery is fluctationg every 301.200 seconds which depend u[pon the thermal behaviour of battery pack.
Conculation:-
conduction is basically here heat flow rate (Q) and temperature difference (T) Vs time.
convection:-
below graph highlight the heat flow rate and temperature difference by convection medium.
cyclic charge / discharge profile:-
charge and discharge profile are depending upon current (I) and voltage (V) Vs time. the cyclic charge and discharge were calculation at 50A peek amplitude.
Test - 3 (low to high temperature):
As we can see that in cell 5 the temperature quickely falls and it fluctuate for 5 k and end at 307 k.
calculated SOC:-
as we see that the battery is fluctuating every 301.200 seconds which depend upon the thermal behaviour of battery pack.
Conduction;-
Conduction is basically here heat flow rate (Q) and temperature difference (T) Vs Time
Convection:
below graph hightight the heat flow rate temperature differentail by convection medium.
cyclic charge / discharge profile.
charge and discharge profile are depending upon current (I) and voltage (V) vs time. the cyclic charge and discharge were calculation at 50A peek amplitude.
Test - 4 (high to low temperature):-
As we can see that in cell 5 the temperature quickly falls an dit fluctuate for 5 k and at 309k.
calculation SOC:-
as we see that the battery is fluctating every 302.200 seconds depends upon the thermal behaviour of battery pack.
conduction:-
conduction is basically here heat flow rate (Q) and temperature difference (T) VS Time.
Convection:-
below graph highlight the heat flow rate and temperature difference by convection medium.
cyclic charge/discharge profile;-
charge and discharge profile are depending upon current (I) and voltage (V) Vs time. the cyclic charge and discharge were calculated at 50A peek amplitude.
Test - 5 (cell _5 maximum temperature):-
as we can see that in cell 5 the temperature quickely falls and it fluctate for 5 k and end at 309 k.
calculated SOC:-
as we see that the battery is fluctuating every 301.200 seconds which depending upon the thermal behaviuor of the battery pack.
conduction:-
conduction is basically here heat flow rate (Q) and temperature difference (T) Vs time.
convection:-
below graph highlight the heat flow rate and temperature difference by convection medium.
cyclic charge / discharge profile:-
charge and discharge profile are depending upon current (I) and voltage (V) Vs Time. the cyclic charge and discharge were calculated at 50A peek amplitude.
conclusion:-
. the flow of heat is decreased at constant and minimum temperature that is 309 k for different temperature based.
. based on different temperature we will see changes in conduction and convection.
. there is slightly change in cyclic charge and discharge of cell which i fixed at 50A as peek amplitude.
. as i set fault in cell-5 and we can see that there is lots of fluctuation and temperature rise in cell-5 as compared other cells connected in series.
SOC for all different temperature are same, there is no changes in SOC.
NAME- MD ARIF
FINAL PROJECT