Signal flow graph modelling and analysis of interleaved DC-DC parallel converters

This paper presents a systematic development of a unified signal flow graph model for an interleaved DC-DC parallel converter system operating in cont inuous current mode. This signal flow graph approach provides a means to tr anslate directly the switching converter to its graphic model, from which t he steady-state and dynamic behaviour of the converter can be studied easil y. The development of a unified signal flow graph is explained for a three- cell interleaved parallel converter system. Derivation of large-signal, sma ll-signal and steady-state models from a unified signal flow graph is demon strated by considering a two-cell interleaved converter system operating in complementary activation mode. Converter performance expressions such as s teady-state voltage gain, efficiency expressions and small-signal character istic transfer functions are also derived. A large-signal model was program med in a TUTSIM simulator, and the large-signal responses against supply an d load disturbances were predicted. Signal flow graph analysis results are validated with PSIM simulations. Experimental observations are provided to validate the signal flow graph modelling method. Further, the mathematical models obtained from the signal flow graph modelling are in agreement with those obtained from the state-space averaging technique.