In this presentation we are going to see the challenge with respect to designing closed-loop control of DC to DC converter
the key challenge in here is to linearize this discontinuous system
and design a closed-loop control that are tuned accurately
the solution is to identify a linear transfer function from input and output data set
and tune the controller gains using Auto tuning algorithm
Let us get into MATLAB and see how these challenge is addressed in detail
This is a DC to DC Sepik converter with a voltage mode control
and I am giving an input voltage of 12 volt
I want my output response to be raising from 12 volt to 27 at around point 4 seconds
Let's simulate the model and see how the response looks like
You can see that since my controller is not tuned
I am NOT able to get the reference voltage of 12 volt within point 4 seconds
and 27 volt within point 8 seconds
So I need to tune my controller to get a desired time domain response
let's get into this PA controller
and hit the tune button
So when I am clicking the tune button, it is trying to linearize the plant model
However, since the converter as discontinuities it linearizes to 0
With the newer versions of MATLAB
you can identify a new plant by giving an input response
and we can use this identified plant for tuning the controller kills
Let us look into it in detail
so I can click on simulate data
and give an offset of 0.5
an amplitude of the step to be around point 4
This means the input step response ranging from 0.5 to 0.9 duty-cycle
What essentially is happening here is the PID controller is temporarily removed
and instead of the output from the PID controller
The step input which you seeing over here is given to the plant model
the controller error is measured and using this input and output data a linear transfer function is estimated
The linear transfer function can then be used to tune the controller gains
So now let's go ahead and hit a run simulation
So now you can see that I've got three different responses
one is offset response, which is the controller error for an offset of 0.5 duty cycle
and input response is the controller error for the input step response
the identification data is the difference between input response and offset response
and using the input and output identification data we can find a transfer function
Let me go ahead and apply this and close
and now System Identification toolbox gives an option to choose different forms of transfer function
in this case, I'm giving an under damped pair and go ahead and click on auto estimate
So you can see that I got my identified plant which matches the identified data
and I can click apply
This linear transfer function is used to tune the controller gain, which you can see on the left side
I can click on show parameters see how my rise time settling time looks like
and I can make it to move faster or slower based upon my specification
So, let me have a settling time of 0.1 second over here
a rise time of point zero six seconds
and update the block
Once I've updated my control gains I can go ahead and simulate my model
The converter reaches the reference voltage of 12 volt
and 27 volt with a desired settling time
to summarize this presentation
we saw how the challenge associated with the designing and tuning voltage mode control
For a sipic converter are addressed using MATLAB and Simulink