Project 2 Thermal modeling of battery pack
Introduction:
>The lithium-ion battries are widely used as energy sources in different hybrid and electric vehicle, however the operation characterstics of the battery in such vehicle are strongly dependent on the operation temprature and therefore, with purpose to improve these characteristics as a godd thermal control system should be utilized.
>The temprature of a lithium battery cell is important for it's performance, efficiency, safety and capacity and is influenced by environmental temprature and by the charging and discharging process itself.
>Therefore, a thermal model of the battery is used in order to calculate and estimate the cell temprature.
>So, for 10-cell series lithium ion battery here it's used MATLAB Simulink for finding thermal effet and life cycle performance related to temprature change and discharge.
>Lithium-ion battery pack with fault is to simulate a battery pack consisting of multiple series-connected cells in an efficient manner.
>It also showshow a fault can be introduced into one of the cells to see the impact on battery performance and cell tempratures.
>For efficiency, identical series-connected cells are not just simply modelled by connecting cell models in series.
>Instead a single cell is used and the termoinal voltage scaled up by the number of ells.
>The fault is represented by changing the parameters for the cell 5 fault subsytem, reducing both capacity and open-circuit voltage and increasing the resistance values.
>A default MATLAB Simulink Model of batery pack whichis used for 10-cell battery pack thermal modelling is given below:
>A detail design of MATLAB Simulink model for thermal modelling is given below:
Cell 01 to 04 Subsytem:
>Cell system basically consists of a thermal model and lithium cell 1RC block which calulates the temprature and thermal effect for cells and overall calculates for the battery pack.
>The block which are inside the cell subsytem PS gain block which multiplies the input physcial sigbnal by a constant i.e. y=u*gain.
>Anothr blocks are voltage sensor and current voltage source.
>The voltage sensor block represnts an ideal voltage sensor i.e. a device that converts voltage measured between any electrical connections into a physical signal proprtional to the voltage.
>Current voltage source represents an idela 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 Subsytem:
>The important block which is inside the thermal model subsytem are:
Thermal Reference:
>This block represents a reference point in a thermal network where the temprature is equal to absolute zero.
Controlled Heat Flow Rate Source:
>This block represents an ideal energy source in a thermal network that can maintain a controlled heat flow rate regardless of the temprature difference.
>The heat flow rate is set by the physical signal port S.
>A positove heat flow arte flows from port A to port B.
Thermal Mass:
>This block models internal energy storage in a thermal network.
>The rate of temprature increases is propotional to the heat flow rate into the material and inversely propotional to the mass and specific heat of the material.
Temprature Sensor:
>This block measure temprature in a thermal network.
>There is no heat flow through the sensor.
>The physical signal port T reports the temprature difference across the sensor.
>The measurement is positive when the temprature at port A is greater than the temprature at port B.
Lithium Cell 1RC Subsystem:
>This block basically consists of capacitance value C table which depends on an external physical signal inputs SOC and T.
>It is assumed that the capacitance value is slowly varying with time and hence the equation i=C*dv/dt holds.
>Resistance value (R) table which depends on an external physical signal inputs SOC and T.
>Voltage value (EM) which implements the cell's main branch voltage source and determines value for capacity (C) and State of Charge (SOC).
>The defining equations depend on cell temprature, T.
Thermal Behaviour & Fault Setup:
>Lithium ion cell one RC-Branch equivalent circuit detail for 10 cells.
For cell 01 to 04:
>Number of series-connected cells are 4.
>Initial temprature is 299.1K.
For cell 05(fault setup):
Note: In this cell there's some change been done in electrical system of cell so that the fault can be seen.
>Number of series-connected cells are 1.
>Initial temprature is 299.1 K.
>Capacity (A*hr) = Capacity_LUT*0.95.
>Em open-circuit voltage (volts) = Em_LUT*0.9.
>R0 teminal resistance (ohms) = R0_Lut*5.
>R1 cell resistance (ohms) = R1_LUT*5.
>C1 capacitance (farads) = C1-Lut*0.95.
For cell 06 to 10:
>Number of series-connected cells are 5.
>Initial temprature is 299.1K.
The Changes in dialouge box are given below:
>Here the outpu
t of one cell is connected with the OSC calculation whereas other output is connected with AC current source for cyclic charge / discharge profile.
>The peak amplitudes set to 50A for cyclic charge and discharge.
>A basic parameter of AC current source is as
>The idela AC current source maintains the sinusodial current through it, independent of the voltage across it's terminals.
>The output current is defined by l = 10*sin(2*pi*f*t + PHl), where l0 is the peak amplitude, f is the frequency in Hz and PHI is the phase shift in raidians.
>The other block which are used in lithium ion battery pack are as:
Temrature Source:
>This block represents an idela energy source in athermal network that can maintain a constant absolutr temprature at the port regradless of the heat flow rate.
>The value set for this block is 299.1K or 25.95C.
Covective Heat Transfer:
>This block models heat transfer ina thermal network by convection due to fluid motion.
>The rate of heat transfer is propotional to the temprature difference, heat transfer co-efficient and surface area in contact with the fluid.
Conductive Heat Transfer:
>This block models heat tranfer in athermal netwrk by conduction through a layer of material.
>The rate of heat transfer is governed by Fourier's law and is propotional to the temprature difference, material thermal conducitvity, are normal to the heat flow direction and inversely propotional to the layer thickness.
>The conduction is done from the 2 set of vlocks, 1 block is used for 02-04 and other is used for cell 06-10.
For Soc calculation, here gain block, integrator block and sum block is used with the PS Simulink converter.
Results:
Simulaton Based On Different Cell Temprature:
>In this simulation the ambient temprature is et at 299.1K and another cell tempratures are as follows:
Colour indication for cells:
>Yellow Colour - Cell 4.
>Purple Colour - Cell 5 (fault).
>Green Colour - Cell 10.
Test-1 (Equal Temprature):
>As we can see that there is uch fluctuation in cell 05 due to fault.
Calculated SOC:
>As we can see that the battery is fluctuating every 301.200 seconds which depend upon the thermal behaviour of the battery pack.
Conduction:
>Conduction is basically here heat flow rate (Q) and temprature difference (T) VS Time.
Covection:
>Below graph highlight the heat flow rate and temprature difference by conevction medium.
Cyclic charge / Discharge Profile:
>Charge and discharge profile are dependinupon Current (I) and Voltage (V) VS Time.
>The cyclic charge and discharge were calcutlated at 50A pak amplitude.
Test-2 (Cell 5 minimum Temprature):
>As we can see that in cell 5 the temprature rise till 312 and it goes fluctuating from 313 to 307 K and at the end at 311 K.
Calculated SOC:
>As we can see the battery is flucating every 301.200 seconds which depends upon the thermal behaviour of the battery pack.
Conduction:
>Conduction is basically here Heat Floe Rate (Q) and Temprature Difference (T) VS time.
Covection:
>Below graph highlights the heat flow rate and tempratur difference by convection medium.
Cyclic Charge / Discharge Profile:
>Charge nd discharge profile are depending upon current (I) and volatge (V) VS time.
>The cyclic charge and discharge were calculated at 50A peak amplitue.
Test-3 (Low ToHigh Temprayre):
>As we can see that in cell 5 the temprature quickly falls and it fluctuates for 5K and end at 307K.
Calculated SOC:
>As we can see that the battery is fluctuating at every 301.200 seconds which depends upon the thermal behaviour of battery pack.
Conduction:
>Conduction is basically here Heat Floe Rate (Q) and Temprature Difference (T) VS time.
Convection:
>Below graph highlights the heat flow rate and tempratur difference by convection medium.
Cyclic Charge / Discharge Profile:
>Charge nd discharge profile are depending upon current (I) and volatge (V) VS time.
>The cyclic charge and discharge were calculated at 50A peak amplitue.
Test-4 (High Low Temprature):
>As we can see that in cell 5 the temprature quickly falls and it fluctuate for 5 K and end at 309 K.
Calculated SOC:
>As we can see that the battery is fluctuating at every 301.200 seconds which depends upon the thermal behaviour of battery pack.
Conduction:
>Conduction is basically here Heat Floe Rate (Q) and Temprature Difference (T) VS time.
Convection:
>Below graph highlights the heat flow rate and tempratur difference by convection medium.
Cyclic Charge / Discharge Profile:
>Charge nd discharge profile are depending upon current (I) and volatge (V) VS time.
>The cyclic charge and discharge were calculated at 50A peak amplitue.
Test-5 (Cell-5 MAximum Temprature)
>As we can see that in cell 5 the temprature quickly falls and it fluctuates for 5 K and at end it's at 309 K.
Calculated SOC:
>As we can see that the battery is fluctuating at every 301.200 seconds which depends upon the thermal behaviour of battery pack.
Conduction:
>Conduction is basically here Heat Floe Rate (Q) and Temprature Difference (T) VS time.
Convection:
>Below graph highlights the heat flow rate and tempratur difference by convection medium.
Cyclic Charge / Discharge Profile:
>Charge nd discharge profile are depending upon current (I) and volatge (V) VS time.
>The cyclic charge and discharge were calculated at 50A peak amplitue.
Conclusion:
>The flow of heat is decreaseed at constant and minimum temprature that is 309k for different temprature based.
>baseed on diferent temprature we will see changes in conduction and convection.
>There is slightly change in cyclic charge and discharge of cell which it's fixed at 50A as peak amplitude.
>As the fault's set in cell-5 and we can see that there is a lots of fluctuation and tempraure rise in cell-5 as compared with other cells connected in series.
>SOC for all different temprature are same, there is no changes in SOC.