Project 1

In this project 3 converters are been designed as per given in the project table they are as follows :-

Project No:-	Converter Type	Input Voltage	Output voltage	Power level
1	Buck CCM	400-500V	300V	5Kw
2	Cuk Converter	30-60V	-45V	300w
3	Boost CCM	20-30V	40V	600w

Project 1.1:-

Schematic of DC-DC Buck Converter :-

First , we will use the voltage ratio equ. To calculate the needed duty cycle:-

Vout/Vin=300/400

D=0.75

We know that the output voltage is 300v and we require 5Kw as output power

Therefore ,

P=5kw

P=5000W

We can also determine that,

R=Vout^2/P

R=300^2/5000

R=18 Ohm

Now, we will design the converter inductor:

We know that

`Il=Io=P/Vo=5000/300=16.6667A`

Then , let us design for 10% ripple in the inductor.

Then

`∆iL=0.1*16.667A=1.667A`

We know that ,

`L=(Vout/(fs*∆Il))(1-D)`

`L=(300/(20k*1.667A))=0.25=0.224mH`

Then l=0.224mH

Let us now design the output capacitor for 5% ripple :-

`Cout=((1-D))/(8*L*fs^2*(∆Vo/Vo))``Cout=(1-0.75)/(8*0.24mH*20k^2*(0.05))=6.25 uF`

We have found out the duty cycle , value of resistor , capacitor and inductor the next step we will design the model in Simulink .

The model is as shown below –

Scope for input and output voltage and input and output current :-

Zoomed in scope:-

Scope of inductor current duty ratio , diode and mosfet current :-

Zoomed in scope

Here the output is as desired and the ripple of inductor current is 10% and of capacitor is 5%. We can see that the diode and mosfet gets tuned on and off one after another.

Cuk Converter :-

Given :-

Vin:- 30V-60V

Vout:- -45V

P:- 1KW

Fs:- 20KHz

First we will use the voltage ratio Equ. to calculate the needed duty cycle :-

`(-Vout)/Vin=(-45V)/60V=(-D)/((1-D))`

`(-45V)/60V=(-D)/((1-D))``D=0.4285`

Now we will design the Cuk converter inductor;

We know that ,

`Il1=Ii=P/vin=1000/60=16.667A`

`Il2=Io=P/Vo=1000/45=22.222A`

And

`R=〖Vout〗^2/P`

`R=45^2/1000=2.025 Ohm`

Let us design for the 10% ripple in the inductor:-

`∆iL1=16.6667*0.1=1.667A`

`∆iL2=22.222*0.1=2.222A`

We know that,

`L1=(Vin/Fs∆IL)D`

`L1=(60/(20K*1.6667))0.4285`

`L1>0.712 mH`

`L2=(60/(20K*2.222))0.4285`

`L2>0.5785 mH`

Thus we choose,

L1 =0.8 mH

L2=0.6 mH

Let us start designing the intermediate capacitor C1:-

`C1=VoD/Rfs∆Vc1`

`Vc1=vin-vo=60-(-45)=105V`

Thus ,

`∆Vc1=0.1*105=10.5v`

Let us now design the output capacitor Cout using Equ:-

`Cout=((1-D))/(8*L*fs^2*(∆Vo/Vo))`

`Cout=0.5715/(8*0.6mH*20k^2*(0.01))=60.297 uF`

The MATLAB model is as shown below:-

The values calculated for the duty cycle , inductor , capacitor and resistor are set in the MATLAB model

Scope results zoomed out :-

The above scope shows the input voltage , output voltage , mosfet and diode current:-

The zoomed in scope for the same is as shown below :-

We can see from the scope that cuk converter as converted the Vin to the desired Vout and the output voltage is negative, though the output voltage has not achieved -45 V but its near to -42V , this is due to the resistances present in the circuit modelling.

Boost CCM:-

Given :-

Vin:- 20-30V

Vout:- 40V

P:- 600W

Fs:- 20KHz

Schematic of DC-DC Boost converter :-

First we will use the voltage ratio Equ. to calculate the needed duty cycle :-

`Vout/Vin=40V/30V=1/((1-D))`

`D=0.25`

Now we will design the converter inductor;

We know that ,

`Il=Vin/((1-D)^2 R)`

And

`R=〖Vout〗^2/P`

`R=40^2/600=2.667 Ohm`

Thus,

`Il=Vin/((1-D)^2 R)`

`Il=30/((1-0.25)^2*2.667)`

`Il=30/1.5=20A`

Let us design for the 10% ripple in the inductor:-

`∆iL=0.1*20A`

`∆iL=2A`

We know that,

`L=(Vin/Fs∆IL)D`

`L=(30/(20K*2))0.25`

`L=0.1875uH`

Thus we choose,

L =0.2uH

Let us now design the output capacitor C using Equ:-

`Cout=D/Rfs(∆Vo/Vo)`

`Cout=0.25/(2.667*20k*0.1)`

`Cout=0.00004678 F`

The MATLAB model is as shown below:-

The values calculated for the duty cycle , inductor , capacitor and resistor are set in the MATLAB model

Scoped result for Vout ,Iout and power output :-

Zoomed in scope :-

Scope for Vout, mosfet current, diode current , inductor current PWM Signal and Duty cycle :-

Zoomed In scope :-

The converter is able to track the desired output as per the required design , we can see that when the mosfet is on and that time the diode is off and vise-vers , we can see that the converter is operating in CCM mode.