Project 2 Thermal modeling of battery pack

PROJECT:

AIM:

To study Thermal modeling of the battery pack with the help of MATLAB AND SIMULINK.

OBJECTIVE:

For a 10 cell series lithium ion battery model,simulink the thermal effects and compare life cycle performance at various temperature,charge & discharge rates using MATLAB.

SIMULINK MODEL :

For the 10 - cell series lithium - ion battery here I used Matlab and Simulink for findings thermal effect and life cycle performances related to temperature , charge , and discharge and also conduction and convection blocks are used to show how the heat transfer takes place in battery packs . Lithium - ion battery pack with fault is to simulate a battery pack consists of multiple cells connected in series efficiently.it also shows how a fault can be introduced into one of the cells to the impact on battery performance and cell temperatures , for efficiency the identical series connected cells are not just simply model by connecting cell models in series . instead single cell is used , and the terminal voltage is scaled up by the number of cells . the fault is represented by changing the parameters for the cell 5 subsystem , reducing both the capacity and open - circuit voltage , and increasing the resistance values .

How the connection is made :

10 lithium - ion battery cells are connected in with the combination of three packs the flst consistent 4 cells in series 2nd pack consist of 1 cell which set to design as fault for study purpose to observe temperature changes within battery pack and the 3rd pack contain 5 cells in series.

the heat transfer is observed between the packs by conduction and convection block which are modes of heat transfer . -T subsystem is attached in between every pack to plot the temperature graph of the cell of that particular battery pack . -also external ambient temperature source is attached and also thermal sensor is attached to the same . to indicate the value in the display . -this battery pack is connected to AC current source to observe the cyclic charge and discharge rate graph . - also we added a current sensor in between the battery pack and AC current source to calculate the SOC of the battery -the cell temperature and soc graphs are plotted in scope which indicating the temperature of cell no 4 , cell no 5 , and cell no 10 -all the other results are located in the simscape result menu .

Cell 01 to 04 subsystem:

The cell subsystem basically consists of a thermal model and lithium cell 1RC block which calculate the temperature and thermal effect for cells and overall calculate for the battery pack . The block which are inside the cell subsystems are PS gain block which multiplies the input physical signals by a constant i.e y = u . * gain .another block are voltage sensor and current voltage source . The voltage sensor block represents an ideal voltage sensor , this is a device that converts voltage measured between any electric connection into a physical signal proportional to the voltage . The 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 numeric value represents at the physical signal port .

Thermal model :

The block present inside the systems are,

a ) Thermal Reference :

Reference connection for thermal ports.

The Thermal Reference block represents a thermal reference point , that is , a point with an absolute zero temperature , concerning which all the temperatures in the system are determined .

b ) Controlled Heat Flow Rate Source Variable source:

Variable source of thermal energy ,characterized by heat flow.

The Controlled Heat Flow Rate Source block represents an ideal source of thermal energy that is powerful enough to maintain specified heat flow at its outlet regardless of the temperature difference across the source . Connections A and B are thermal conserving ports corresponding to the source inlet and outlet , respectively . Port S is a physical signal port , through which the control signal that drives the source is applied . You can use the entire variety of Simulink signal sources to generate the desired heat flow variation profile . The heat flow through the source is directly proportional to the signal at the control port S. The block positive direction is from port A to port B. This means that a positive signal at port S generates heat flow in the direction from A to B.

c) Thermal Mass:

Mass in thermal systems the Thermal Mass block represents a thermal mass , which reflects the ability of a material or a combination of materials to store internal energy . The property is characterized by the mass of the material and its specific heat . The thermal mass is described with the following equation : Q = c.m * dT / dt.

d ) Temperature Sensor:

Ideal temperature sensor the Temperature Sensor block represents an ideal temperature sensor , a device that determines the temperature differential measured between two points without drawing any heat . Connections A and B are thermal conserving ports that connect to the two points where the temperature is being monitored . Port T is a physical signal port that outputs the temperature differential value . The block positive direction is from port A to port B. The measured temperature is determined as T = TA - TB .

Lithium Cell 1RC Subsystem:

This block especially consists of the capacitor ( c ) value table which depends upon an external physical signal input SOC and T.it is assumed that the capacitor value is varying with the time and hence the equation i = C * Dv / dt holds . -Resistance value ( R ) table depend on external physical signal inputs SOC and T. -Voltage value ( EM ) implements the cell's main branch voltage source and determines values for capacity ( C ) and state of charge ( SOC ) . The defining the equations depends upon cell temperature T.

THERMAL BEHAVIOUR AND FAULT SETUP :

Lithium - ion one cell one RC - Branch equivalent circuit detail for 10 cells.

Number of connected in series are -4

Initial temperature -299.1 k

For cell 5 cells ( fault setup ) in this cell , I have done changes in the electrical systems of the cell so that we can see the fault .

Number of connected in series are = 4

Initial temperature = 299.1 k

Capacity ( A * hr ) = Capcity_LUT * 0.95

EM - open - circuit voltage ( volts ) = Em_LUT * 0.9

RO terminal resistance ( ohms ) = RO_LUT * 5

R1 cell resistance ( ohms ) = R1_LUT * 5

C1 capacitance ( farads ) = C1_LUT * 0.95

For cell 06 to 10 :

Number of connected in series are : -5

Initial temperature : -299.1 k

Temperature Source :

A constant source of thermal energy , characterized by temperature. The Temperature Source block represents an ideal source of thermal energy that is powerful enough to maintain a specified temperature at its outlet regardless of the heat flow consumed by the system . The source generates constant absolute temperature , defined by the Temperature parameter value .here I used ambient block and set the temperature for 299.1k or 25.95 C Block Parameters.

THERMAL ELEMENTS :

Conductive Heat Transfer

Heat transfer by conduction.The Conductive Heat Transfer block represents a heat transfer by conduction between two layers of the same material . The transfer is governed by the Fourier law and is described with the following equation : Q = K.AD ( TA - TB ) where Q Heat flow k Material thermal conductivity A Area normal to the heat flow direction D Distance between flow direction D Distance between layers ( thickness of material ) TATB Temperatures of the layers Connections A and B are thermal conserving ports associated with material layers . The block positive direction is from port A to port B. This means that the heat flow is positive if it flows from A to B. The is done from the 2 sets of blocks .one is for cell 04 to 05 and another is used for 05 to 06 .

Convective Heat Transfer :

Heat transfer by convection.The Convective Heat Transfer block represents a heat transfer by convection between two bodies using fluid motion . The transfer is governed by the Newton law of cooling and is described with the following equation : Q = K.A . ( TA - TB ) where Q Heat flow k Convection heat transfer coefficient A Surface area TA,TB Temperatures of the bodies Connections A and B are thermal conserving ports associated with the points between which the heat transfer by convection takes place . The block positive direction is from port A to port B. This means that the heat flow is positive if it flows from A to B.

Here I used 3 blocks for convection:

for cell 01-04 , cell 05 , cell 06-10 Temperature Sensor Ideal temperature sensor. The Temperature Sensor block represents an ideal temperature sensor , a device that determines the temperature differential measured between two points without drawing any heat . Connections A and B are thermal conserving ports that connect to the two points where the temperature is being monitored . Port T is a physical signal port that outputs the temperature differential value.

The block positive direction is from port A to port B. The measured temperature is determined as T = TA - TB .

Electrical Elements :

Here the output of one cell is connected with the SOC calculation whereas the output is connected to with AC source for the cyclic charge / discharge profile

a ) AC Current Source :

The ideal sinusoidal current source.The AC Current Source block represents an ideal current source that maintains the sinusoidal current through it , independent of the voltage across its terminals . The output current is defined by the following equation : 1 = 10 sin ( 2π f.t + q ) The peak amplitude is set to 50 A for a cyclic charge and discharge .A basic parameter of source.

The ideal AC current source maintains the sinusoidal current through it , independent of the voltage across its terminals . The output current is defined by I = 10 * sin ( 2 * pi * f * t + PHI ) , where 10 is the peak amplitude , f is the frequency in Hz , and PHI is the phase shift in radians .

Current Sensor:

The current sensor in electrical systems.The Current Sensor block represents an ideal current sensor , a device that converts current measured in any electrical branch into a physical signal proportional to the current . Connections and are electrical conserving ports through which the sensor is inserted into the circuit . The connection I am a physical signal port that outputs the measurement result .

Electrical Reference :

Connection to electrical ground .The Electrical Reference block represents an electrical ground . Electrical conserving ports of all the blocks that are directly connected to the ground must be connected to an Electrical Reference block . A model with electrical elements must contain at least one Electrical Reference block .

SOC calculation :

Here I used gain block . integrator and sum block sum with PS Simulink converter .

For the study , we have some observation where we getting results for different cell temperature :

RESULTS:

Test - 1 :

Test Ambiant Tamperature ( K )=299.1

Cell Tumperature ( K )( 01-04 )=299.1

Cell Tamperature ( K)(05)=299.1

Cell Temperature (K)( 06-10 ) = 299.1

Observations : Equal Temperature

GRAPHS :

a ) Cell Temperature :

Tur 200 T Compre -all the three the cell having the same temperature at the start which is at 299.1 k.but in the beginning few seconds of simulation cell no 5 oscillates with more the cell 4 and 10 because its design with fault and ranging to higher temp then cell 4 and 10.after a time period of around 1300 sec both the cells getting are unfollowing the temperature line which was following the same temperature rate , cell no 4 and 10 having approximately 315 ( cell 04 having quite less temp then cell 10 because of no of the cell are different ) k at the end of the simulation and the cell no 5 achieving the higher temperature of around 328 k.

b ) SOC:

A -the soc graph following the sinusoidal waveform structure and fluctuating after 297 seconds and this waveform achieving the value of more than 100.06 soc.

c ) Convection :

Convection is the process of heat transfer by the bulk movement of molecules within fluids such as gases and liquids.

For cell 01-04 :

For cell , no 01-04 the oscillations are pretty low and dropping into the negative zone at the end of the simulation . the final values for

The heat transfer coefficient is -71.63 W / ( m²K )

Thermal conductivity -15.76 W / m K

For cell 05 :

For cell no 5 they are starting from 0 and falling into the negative zone the oscillation having high amplitude because of the faulty cell at the end of the simulation .

The heat transfer coefficient is -13.39 W / ( m²K )

Thermal conductivity -26.92 W / mK

For cell 06-10 :

For cell no 06 to 10 the falling from zero to the negative zone the oscillation are less . at the end of the simulation .

The heat transfer coefficient is -82.63 W / ( m²K )

Thermal conductivity -16.36 W / mK

Test - 2 :

Ambient Temperature(K)=299.1

Cell Temperature(K)(01-04)=310

Cell Temperature(K)(05)=320

Cell Temperature(K)(06-10)=330

Observations: Low to high temperature.

a )Cell Temp :

The initial temperature for cell no 04 is 310K , cell no 5 is 320 K and cell no 10 is 330K , but after some point , cell no 04 and cell no10 started following the same temperate rate , and cell no 5 starts oscillating with high value because of fault , the final value for cell no 04 and 10 is around 316K and fro cell no 5 is 328K because of its fault design.

b ) SOC :

c )Convection :

For cell no 01-04 :

The final values at the end of the simulation are

The heat transfer coefficient is -71.64 W / ( m²K )

Thermal conductivity -15.75 W / mK

For cell 05:

For cell no 5 the final value at the end of the simulations are

The eat transfer coefficient is -13.39 W / ( m²K )

Thermal conductivity -26.28 W / mk

For cell 06-10:

For cell no 06-10 the final values at the end of the simulation are

The heat transfer coefficient is -83.30 W / ( m²K )

Thermal conductivity -16.34 W / mK

Test - 3 :

Ambient Temperature(K)=299.1

Cell Temperature(K)(01-04)=350

Cell Temperature(K)(05)=325

Cell Temperature(K)(06-10)=305

Observations : High to low temperature

a ) Cell Temp :

For cell no 04 the initial temperature is 350 K , cell no 10 is 305 K and for cell no 5 the temperature is 325 K. both the temperature of cell no 04 and 10 started following the same temperature rate after the time period of 2000 sec and on the other hand , the cell no 5 is designed for fault oscillates with high temperature . the end temperature of cell no 04 and 10 are near about 315 K ( the cell no 4 have little less value then cell no 10 because of the no of cells involved ) and for cell no 5 having a temperature at the end is 328 K.

b ) SOC :

c ) Convection :

For cell 01-04 :

For cell 01-04 -For cell no 01-04the final values at the end of the simulation are ,

The heat transfer coefficient is -72.13 W / ( m²K )

Thermal conductivity -15.62 W / mK

For cell 05 :

For cell no 5 the final values at the end of the simulation are

The heat transfer coefficient is -13.39 W / ( m²K )

Thermal conductivity -26.28 W / mK

For cell 06-10 :

For cell no 06-10 the final value at the end of the simulation is

The heat transfer coefficient is -83.20 W / ( m²K )

Thermal conductivity -16.22 W / mK

CONCLUSIONS:

1 ) As the difference in temperature we can observe the changes in heat flow rate by conduction and convection .

2 ) There are slight changes in cyclic charge and discharge as I fixed peak amplitude at 50 A.

3 ) SOC for all the temperature remain the same so there is no difference in SOC graphs.

4 ) cell no 5 had higher oscillation and we can observe that in every graph because we design that cell for fault.