Adaptive-gain second-order sliding mode observer design for switching power converters

•Novel adaptive-gain Second Order Sliding Mode (SOSM) observer.•Equivalent output error injection.•Only one parameter needs to be tuned.•There is no need a priori requirement of the perturbation bounds.•Based on Z(TN) observability.

In this paper, an adaptive-gain, Second Order Sliding Mode (SOSM) observer for multi-cell converters is designed by considering it as a type of hybrid system. The objective is to reduce the number of voltage sensors by estimating the capacitor voltages from measurement of the load current. The proposed observer is proven to be robust in the presence of perturbations with unknown boundaries. As the states of the system are only partially observable, a recent concept known as Z(TN)-observability is used to address the switching behavior. Multi-rate simulation results demonstrate the effectiveness and the robustness of the proposed observer with respect to output measurement noise and system uncertainty (load variations).