Week 8 Challenge

Load the UC parameter file. Complete the Ultracapacitor model. Set simulation stop time to 598 sec.

The model output should give, current, SOC and Voltage as output

Solutions

Aim:To model the energy storage device as ultracapacitor and analyse its operating characteristics according to the power demand by running the model for 598 sec

An ultracapacitor is also called a Supercapacitor with a capacitance value that is higher than the normal capacitor. It ranges from Milli farads to Farads. It charges and discharges faster when compared with batteries. It stores 10 to 100 times more energy when compared with electrolytic capacitor

Ultracapacitor has two charged plates which are separated with a dielectric. The two charged plates are positive and negative

STEPS TO CONSTRUCT UC MODEL:

Three equations in UC model are defined first which gives us SoC, current and OCV.

This are the three parameters which influences UC.

OCV defines the SoC of Ultracapacitor.

Max Voltage or Voltage is directly proportional to the charge stored in the battery.

Amount of charge is directly proportional to the current that can flow in the circuit.

Where

eta is the Coulomb efficiency.

Q is the electric quantity or charge on UC.

I is the current.

Q depends on capacitance which is the charge storage capacity measured in measured in Farads.

The OCV is a measure of the electric field between plates.

Capacitance and OCV gives 'Q'

The integration of current over 'C' gives 'OCV'.

In UC model calculation for current and SoC are done as said below:

Firstly the current consumed is calculated which is fed into a SoC calcultaion block.

The SoC is then calculated based on the amount of current drawn and pushed back into the UC.

Hence fomula for current is given as:

Where

R is the lumped resistance

Vmax is the max. voltage

eta is the efficiency during the charge-discharge cycle.

PUC is the power demand which is to supplied by UC and it is the first input in this model which basically comes from Energy management systems.

Block used:Constants,I ntegrator,Saturation,terminator memory,add,product,signal buider,sqrt,scope

Model:

Ultracapacitor

In the Ultracapacitor subsystem ,current and voltage calculation subsystem and SOC calculation subsystem is the charge and voltage calculation subsystem ,the current ,voltage, open circuit voltage and charge calculation subsystem is formed

We will see the inside of SOC and current OCV and charge block in the Working of Model Section

Working of Model:

PUC is our input here which is nothing but the power demand for the UC. 2k watts is the value in a complete fuel cell or electric vehicle model it comes from the EMS block, This input given inside the current calculation block with that inside of current calculation block is shown.

parameters Value:

C= 100

R= 0.064

eff=0.9

Soc initial=1

V_max= 300

UC voltage block:

To find the voltage of the UC we need current and SOC as out input which helps us find UC voltages The formula for its shown in simulink representation

formula used

UC current block

if you see cuurrent and Soc calculation blocks are interconnected then both takes each other in there value calculation The more the current is drawn the lower SOC is going to get Initial SOC has been Set wo 1 which basically means that we are going to draining the ultracapacitor

formula used

OCV block:

. With the help of calculated current we can calculate the OCV The formula was stated above and its implementation is shown below

Charge UC block

formula is

SOC block

o find the voltage of the UC we need current and SOC as out input which helps us find UC voltages The formula for its shown in simulink representation

Results:

Current depends upon the various parameter its seems to rise exponentially 6.8 is the highest value that capacitor supplied

As we know our max voltage was 300V it seems to be decreasing as more current is demanded from UC at the end of SOC limit that means 20% the voltage value is around 70%

The SOC looks to follow similar pattern as that of voltage its is because voltage defines the SOc of ultracapacitor The reason why the model ran for almost 598 seconds is because we have chosen high value of Capacitance C like capacitance we have loaded the parameters using mat file