Adaptive Feed-Forward Reduced-Order Double-Integral Sliding Mode Control of a Synchronous SEPIC Converter

This paper describes a reduced-order adaptive feed-forward proportional-integral (PI)-based Double-Integral Sliding Mode Control (DI-SMC) technique for a bi-directional SEPIC converter. The proposed control technique is a nested dual-loop second-order control technique that considers the states of the converter which prominently affect the converter eigenvalues. The dual-loop control structure involves an inner loop that regulates average current of the input-side inductor, and an outer control loop for regulating the output voltage. The proposed DISMC technique considers a sliding line given by the graphical intersection of a linear sliding manifold and an orthogonal manifold in state space region for deriving equivalent control principle of the converter. The sliding curve has a specific orientation based on a given orientation of the orthogonal manifold, selected using the optimised transient response of the converter. Further, the proposed control technique is adaptive, where the effect of the changes in the converter parameters or disturbances are suppressed by on-line re-tuning of feed-forward gains of the control loop. This adaptive feed-forward compensation, instead of an adaptive PI controller, takes care of the disturbances with less changes to the main control loop, thereby ensuring required transient suppression. The proposed control technique is tested for different test condition on MATLAB/Simulink platform and the results are discussed in the further sections of the paper.