Extended High Gain Observer based Control Design for Buck-Boost Converters

The evolution of the modern technologies and the development of power electronics has led to the extensive use of DC-DC Buck-Boost converters in the application of power amplifier, battery management system, self-regulating power supplies etc, as they have higher output voltage and low operating duty cycle. The problem of degradation in adeptness of the Buck-Boost converters in presence of a load and lumped parameter uncertainties are analyzed. An Extended High Gain Observer is formulated to estimate the output voltage, load current, and its first derivative which is considered to be nonlinear and bounded. The reference current is compared with the estimated load current, forming a sliding surface. Sliding Mode Controller ensures convergence of estimated load current trajectories to reference current trajectories in finite time. Finally, an inner control loop generates a duty ratio resulting in output voltage which tracks the required reference voltage. The simulation results have been implemented in MATLAB/Simulink to validate fast estimation of load current, output voltage and disturbance rejection in a closed-loop process.