Unknown System Dynamic Estimator-Based Two-Phase Power Reaching Law Control for DC-DC Buck Converter

In this paper, an unknown system dynamic estimator-based reaching law control scheme is proposed for buck converters with parameter uncertainties, input voltage fluctuations and load variations. By utilizing a first-order low-pass filter, a simple unknown system dynamic estimator (USDE) with only one design parameter is constructed to efficiently compensate for the lumped disturbance. Then, a two-phase power reaching law is presented for the sliding mode controller design, and a relatively fast convergence of the sliding variable is guaranteed in the whole reaching process by adjusting the power value according to the variation range of the sliding variable. With the proposed scheme, both the transient and steady-state voltage tracking performance are achieved with a relatively accurate convergence time expression of the sliding variable. Theoretical analysis and experimental validation are provided to show the feasibility of the proposed method.