Development of Digital PI-MRAC on Eight-Bit Microcontroller for DC-DC Boost Converter

As DC-DC boost converter is required by many appliances, this article discusses the development of prospective controller named Digital PI-MRAC on eight-bit AVR microcontroller, to regulate the DC-DC boost converter output and maintain its performance. Formulas for digital PI-MRAC are first derived using Tustin discretization and then implemented into <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{C}/\mathrm{C}++$</tex> program run on AVR. Constant and accurate sampling time in AVR is realized using timer overflow interrupt. To verify the design, testing was done by Proteus simulation on first order plant and on the boost converter. The results show that the developed PI controller with sampling time <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$10\text{ms}$</tex> can maintain its output at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$15\mathrm{V}$</tex> or <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$30\mathrm{V}$</tex> even though applied load has caused output fluctuation about <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$5\mathrm{V}$</tex>, The system time responses indicate that MRAC successfully tunes the PI parameters. As time increases, the system output is getting closer to the output of reference model and the PI parameters settle to their final value. When AVR is operated in <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$16\text{MHz}$</tex> clock, the sampling time needs to be offset by <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0. 0004\text{ms}$</tex> to compensate for a delay imposed by auxiliary instructions in PI-MRAC code.