Control System Design coursework

Title

Digital control design of a DC/DC boost converter

Project layout

The purpose of this project is to apply control design methods studied during the module to a

practical quite demanding application like a power electronic converter and to get familiar with

Matlab-Simulink programming and simulation environment for control design.

The particular case of study will be represented by the voltage control of a DC to DC boost (step

up) type converter. Schematics, operation mode and control implementation is reported in [1]

and in the attached document.

The boost converter will have the following rated characteristics:

Input voltage = Vin=9V

Output voltage (Vo) in the range between 12V

Maximum power output = 120W

Switching frequency Fs= 100KHz

Design at first the values of L and C assuming a maximum current ripple of 1% and a maximum

voltage ripple of 0.75% [1] (or any other power electronics book).

Calculate the transfer function of the plant represented by the converter itself as reported in the

attached document (the input is the switch duty cycle and the output is the converter output

voltage).

Design, using the matlab tool sisotool, the voltage control based on a continuous

implementation in the s-domain with the following specifications:

=0.7;

o=2**5000 rad/s

Design, using the matlab tool sisotool, the same control loop based on a digital

implementation in the z-domain with the following specifications:

=0.7;

o=2**5000 rad/s

s=2**Fs rad/s.

Compare and comment the results obtained with the two different implementations on a blocks

simulation with Matlab-Simulink.

To verify the robustness of the designed control, implement a parameters drift of 15% with

respect to the designed values; test and comment the control effectiveness. Analyse also the case

of a load variation of 25%.

Tasks and considerations

The following broadly defined tasks are not necessarily consecutive or exhaustive but give the

general framework of the project.

[1] Familiarisation with DC to DC boost converters and their voltage control.

[2] Familiarisation with Matlab-Simulink.

[3] Design modelling and simulation of the converter in open loop according to the given

rated characteristics.

[4] Design and simulation of the s-domain voltage control loop

[5] Design and simulation of the z-domain voltage control loop

[7] Test of the system for normal operating conditions. Comparison between continuous

and digital control.

[9] Test of the robustness of the system under load or parameters variation

[10] Reporting.

References

1. Mohan, Undeland, Robbins: Power Electronics, converters applications and design, John Wiley and sons, New York.

2. Control system design lecture notes

3. Matlab and Simulink operative manual

4. Franklin, Powell, Emami-Naeini Feedback control of dynamic systems, Prentice Hall, New Jersey.

5. Dorf, Bishop Modern control systems, Prentice Hall, New Jersey