Project 2 Thermal modeling of battery pack

OBJECTIVE:

For 10 cells series lithium-ion battery model simulate the thermal effects and compare life cycle performance at various temperatures, charge and discharge rates using MAATLAB. This will be based model which we are going to use for our project by doing some changes in it according to our requirements.

This example shows how to simulate a battery pack consisting of multiple series connected cells efficiently. It also shows how a fault can be introduced into one of the cells to see the impact on battery performance and cell temperatures. For efficiency identical series connected cells are not just simply modeled by connecting cell models in series. Instead a 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 10 fault subsystem reducing both capacity and open-circuit voltage and increasing the resistance values.

Here we actually made changes in the base model according to our requirements to obtain results,

SIMULINK MODEL:

So for the 10 cells series lithium-ion battery here i used MATLAB and SIMULINK for finding 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 inpact on battery performance and cell temperature 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 representended by changing the parameters for the cells 5 subsystem reducing both the capacity and open circuit voltage and increasing the resistance values.

HOW THE CONNECTION IS MADE:

10 lithiumion battery cells are connected in with the combination of three packs the first consistant 4 cells in series second pack consist of 1 cell which set to design as fault for study purpose to observe temperature changes within battery pack and the third 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 is 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 onserve the cyclic charge and discharge rate graph ,also we sdded a current sensor in between the battey pack and AC current source to calculate the SOC of the battery . The cell temperature and SOC graph are plotted in scope which indicating the temperature of cell no 4 ,cell no 5 and cell no 10 and all the other results are located in the simscape result menu.

CELL 1 TO 4 SUBSYSTEM:

The cell subsystem basically consist 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 subsystem are PS gain block which multiplies the input physical signals by a constant that is 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 physical signal proportional to the voltage .

The current voltage source represent an ideal voltage source nthat 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:

This blocks present inside the systems are,

. Thermal Referance :

This block represents thermal reference point, point with an absolute zero temperature concerning which all the temperature in the system are determined.

.Controlled Heat Flow Rate Source:

This block represents an ideal source of the 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. PPort 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.

.Thermal Mass :

The Thermal Mass block represents thermal mass which reflects the ability of material or 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

.Temperature Sensor:

The tamperature sensor block represents an ideal temperature sensor 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

b. Lithium Cell 1RC subsystem:

This block consist of 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

Resistance value (R) table depend on external physical signal inputs SOC and T.

Voltage value (EM) implements the cells main branch voltage source and determines values for capacity(C) and state of charge (SOC) .The defining the equations depends upon cell temperatur T.

THERMAL BEHAVIOUR AND FAULT SETUP:

Lithium ion one cell one RC branch equivalent circuit detail for 10 cells

FOR CELL 1 TO 4

NO of connected in series are :4

Initial Temperature:299.1K

FOR CELL 5 CELLS IN THIS CELL,

I have done changes in the electrical system of the cell so that we can see the fault.

Number of connected in series are = 4

Initial temperature = 299.1K

Capacity (A*hr) = Capacity_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 6 TO 10

Number of connected in series are =5

Initial temperature = 299.1k

Parameters:

Battery Configuration:

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 25.95c

Conductive Heat Transfer:

This 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 layers

Ta,Tb = Temperatures of the layers

Connections A and B 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.That is done from the 2 sets of blocks one is for cell 4 to 5 and another is used for 5 to 6.

Convective Heat Transfer:

The convective heat transfer block represents heat transfer by convection between two bodies using fluid motion. The transfer is goverened 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

Connection 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 1-4

For cell 5

For cell 6-10

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 tamperature 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 B ,The measured tamperature is determined as T = Ta-Tb.

Electrical elements:

.AC Current Source:

This block represents an ideal current source that maintain the sinusoidal current through it independent of the voltage across its terminals.

The output current is defined by the following equation:

I = 10*sin(2pi*f*t+phi)

The peak amplitude is set to 50 A for a cyclic charge and discharge, A basic parameter of AC source is as,

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

Current Sensor

tThis block represents an ideal current sensor a device that converts current measured in any electrical branch into a physical signal proportional to the current.

Connectiona + and - are electrical conserving ports through which the sensor is inserted into the circuit. The connection physical signal port that outputs the measurement result.

Electrical Reference:

This 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:

For 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

Here we have set ambient temperature is to 299.1K or 25C

BBattery Pack Configuration:

Results:

To check the conduction convection and charge and discharge rate plot we used the simscape results option.

For Test-1

GRAPHS:

a. Cell Temperature:

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 aroyund 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 K at the end of the simulation and the cell no 5 achieving the higher temperature of around 328K

.SOC:

The soc graph following the sinusoidal waveform structure and fluctuating after 297 sec and this waveform achieving the value of more than 100.06 SOC

.Conduction:

Conduction is basically heat flow rate and temperature difference with respect to time.

For cell 4 -5

Cell no 4 - 5 and having a high amplitude of waveforms which are oscillating at a pretty high rate which is starting from zero and dropping into the negative zone at the end of the simulation.

The heat transfer coefficient is -21.32 W/(m^2K)

Thermal conductivity -10.66 W/mK

For cell 5 - 6

For cell no 5 to 6 both the wave forms oscillating at high rate but in positive zone which are increasing initially and maintaining a certain range.

The heat transfer coefficient is -20.12 W/(m^2K)

Thermal conductivity -10.06W/mK

Convection:

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

For cell 1 - 4

For cell no 1 to 4 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/(m^2K)

Thermal conductivity -15.76W/mK

For Cell 5 :

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/(m^2K)

Thermal conductivity -26.92W/mK

For cell 6 to 10:

For cell no 6 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/(m^2K)

Thermal conductivity -16.36W/mK

Charge and discharge profiles:

In the charge and discharge rate graph the voltage and current oscillating from pretty highly where current is ranging from -50 to 50 A and voltage is ranging from 30 to 43 volts and the final value at the end of the simulation for

CURRENT = 1.4695E - 13A

VOLTAGE = 36.334 volt

CONCLUSION:

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

. There are slight changes in cyclic charge and discharge as i fixed peak amplitude st 50 A.

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

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

REFERANCE:

For base model :

https://www.mathworks.com/help/physmod/simscape/ug/lithium-ion-battery-pack-with-fault.html

THANKYOU