Large-signal stabilization of DC-DC buck converters considering uncertainty in DC input voltage and ZIP loads

This paper proposes an adaptive nonlinear controller to globally stabilize DC-DC Buck converters feeding an unknown nonlinear ZIP [constant impedance (Z), constant current (I), and constant power (P)] load. As well known, the P-load due to its negative incremental impedance can cause performance deterioration or even instability in the system. The nonlinearity of the voltage-current characteristic of P-loads, especially in the presence of uncertainty, leads to further challenges in the output voltage regulation problem. We assume that the load parameters, the filter resistance, the filter inductance and the filter capacitance as well as the input voltage of the converter, are all unknown. The controller is developed by following the two-step adaptive backstepping method. Our method not only results in accurate voltage regulation in the large-signal sense but also ensures convergence of the estimated instantaneous load power to its actual value. We only employ the measurements of the inductor current and capacitor voltage in the control signal design. Finally, different scenarios are simulated in MATLAB/Simscape Electrical environment to investigate the performance of the proposed controller.