Adaptive-Gain Second Order Sliding Mode Observer Design for Switching Power Converters

TL;DR

This paper introduces an adaptive-gain second order sliding mode observer for multicell power converters, enabling capacitor voltage estimation from load current measurements, with robustness to perturbations and switching behavior.

Contribution

It presents a novel hybrid systems observer that reduces sensor requirements and analyzes hybrid observability using $Z(T_N)$ concepts, improving robustness and effectiveness.

Findings

Robustness to unknown perturbations demonstrated

Effective voltage estimation with fewer sensors

Superior performance over Luenberger observer

Abstract

In this paper, a novel adaptive-gain Second Order Sliding Mode (SOSM) observer is proposed for multicell converters by considering it as a class of hybrid systems. The aim is to reduce the number of voltage sensors by estimating the capacitor voltages only from the measurement of load current. The proposed observer is proven to be robust in the presence of perturbations with \emph{unknown} boundary. However, the states of the system are only partially observable in the sense of observability rank condition. Due to its switching behavior, a recent concept of $Z(T_N)$ observability is used to analysis its hybrid observability, since its observability depends upon the switching control signals. Under certain condition of the switching sequences, the voltage across each capacitor becomes observable. Simulation results and comparisons with Luenberger switched observer highlight the effectiveness and robustness of the proposed observer with respect to output measurement noise and system uncertainties (load variations).