Small-signal modelling and analysis of multi-module parallel converter systems by means of PSPICE

In the last years an important effort has been made relative to the study of distributed power systems, composed generally of cascaded stages of parallel switching regulators. Paralleling of power converters is possible by using some kind of current mode control scheme, like CIC (current injected control) or ACC (average current mode control). The analysis and design of both the control loops and the interactions between individual parallel or cascaded converter modules can be carried out by means of the small-signal equivalent circuit study of each power stage. This paper shows how that task can be easily performed with the help of PSPICE^TM software, obtaining the Bode plots of the transfer functions of the parallel converter system: loop gain, closed loop output impedance, closed loop audiosusceptibility and input impedance. Those transfer functions can also be obtained for cascaded stages of individual or parallel converters, and with intermediate bus and input filters