Signal flow graph nonlinear modelling of interleaved converters

This paper presents a systematic development of a unified signal flow graph (SFG) model for an N-cell interleaved DC-DC converter system operating in continuous current mode. From this SFG small, large-signal and steady-state models are developed, which are useful to study the converter behaviour. Converter performance expressions like voltage gain, efficiency and other small-signal transfer functions are derived. A straightforward algorithm is developed to draw the unified SFG of an N-cell interleaved converter system without going into the rigorous procedure. Development of a unified signal flow graph is explained for a 3-cell interleaved converter system. Derivation of large, small-signal and steady-state models from the unified SFG is demonstrated by considering a 2-cell interleaved converter system. A large-signal model is programmed in a TUTSIM simulator, and the large-signal responses against supply, load disturbances are predicted. Signal flow graph analysis results are validated with PSIM simulations. Experimental observations are provided to validate the SFG modelling method