A novel fixed-time dynamic surface DC/DC SEPIC converter controller loaded by uncertain buck-based constant power loads

The stability analysis of the single-ended primary-inductor converter DC/DC converters feeding constant power loads (CPLs) is of major importance. The nonlinear behaviour of CPLs and their negative incremental impedance, which impose adverse effects on system damping and stability margins, necessitate developing proper strategies for an efficient implementation framework of DC microgrid. In this paper, a fixed-time sliding mode disturbance observer is first addressed to provide an estimation of the power flow moving along the uncertain CPLs with time-varying nature within a fixed time. It not only expedites the estimation rate but also improves the robustness against physical parameter variation. The fixed-time dynamic surface control law is then developed based on the estimated load power for the duty cycle of the switch such that the entire power grid becomes stable and the desired voltage of the DC bus is tracked within a fixed time irrespective of the initial conditions. A rigorous Lyapunov-based approach is represented to guarantee the semi-global fixed-time uniform ultimate boundedness of the proposed scheme. Finally, in order to verify the proposed methodology's strengths, Model-in-the-Loop real-time simulations are performed under various operating case studies.