Alternor-based computer-aided analysis of transient and steady-state of buck-boost converter

An approach to the simulation of power electronic circuits is presented that uses an s-domain method instead of the classical state-space solution. The results reflect accurately the continuous character of the converter waveforms. The use of the Laplace transform in analyzing cyclically switching circuits permits the formulation of a single set of modified nodal equations able to describe the global transient of the converter. Two of the equations of this system allow for the switching behavior: they are the nodal equations of a recently defined circuit element, called an alternor. The alternor is a time-variable two-port containing the switching electronic devices of the converter. The set of equations is solved by using a symbolic computer program. The solution, obtained analytically in the time domain, mirrors the voltage and current waveforms in each switch configuration. The transient and steady-state responses are determined by a time-saving computation. The method is applied to the simulation of buck-boost converters whose transient is due to a step-in-line input voltage. Both the continuous and the discontinuous conduction modes are studied