Finite-Time Disturbance Observer-Based Adaptive Second-Order Sliding Mode Control for Parallel Connected DC-DC Buck Converters with Nonideal Switches

Parallel connected DC-DC buck converters (PCBCs) are inevitably subjected to the disturbances caused by nonideal active switches and uncertain passive components, which poses a significant challenge for achieving both precise current sharing and robust voltage regulation. To address the coupling between inductor current and output voltage, a multilayer control framework equipped with a slow voltage controller and fast current controllers is developed, which can automatically deal with the load variations, and be easily extended to PCBC with N modules. Subsequently, the nonideal characteristics in PCBC are modeled as disturbances. The constructed finite-time disturbance observer (FTDO) can effectively estimate the disturbances, and then a feedforward compensation is made by using the obtained estimates. To mitigate chattering with the further aim of enhancing control accuracy of output voltage, a finite-time stable adaptive second-order sliding mode (SOSM) control is proposed, in which the adaptation algorithm achieves rapid reaching of sliding manifold, and avoids excessive control action. The presented control strategy can obtain fast and accurate tracking of output voltage, as well as balanced current sharing. Experimental results are presented to verify the effectiveness of the proposed method.