Hybrid modeling and control for buck-boost switching converters

The buck-boost switching converter is represented as a hybrid automaton model. The control problem of buck-boost switching converters is simplified to a guard selection problem. Meanwhile, a new hybrid control scheme is proposed to regulate the output voltage of a buck-boost DC-DC switching converter. The scheme covers a wide operating range under various load and line disturbances. In Comparing the minimum current through the inductor with zero and the output current, the algorithm differentiates the buck-boost switching converter into three operation modes, i.e., CCM-CISM (continues conduction mode complete inductor supply mode), CCM-IISM (continues conduction mode-incomplete inductor supply mode) and DCM-IISM (discontinues conduction mode-incomplete inductor supply mode). The guard selection calculation formulas of buck-boost converter are derived from the basic circuit laws. The hybrid automaton based control system is implemented using the state flow chart feature of MATLAB and extensive simulations are carried out to check the validity of the algorithm. Numerical results clearly bring out the advantages and effectiveness of the proposed control law under varying line voltage and load conditions.