Nonlinear Observer Based on Linear Matrix Inequalities for Sensorless Grid-tied Single-stage Photovoltaic System

Abstract

The objective of this work is to design a Nonlinear Observer used in a Cascade Control scheme for Maximum Power Point Tracking goals of a grid-tied single-phase photovoltaic inverter. The main contribution of this work is to employ a nonlinear observer to reduce the number of sensors of an AC-grid-tied single-stage PV system. The nonlinear observer design was developed using the Takagi-Sugeno PV system model and Linear Matrix Inequalities based on Lyapunov stability criteria. To validate the performance of the nonlinear observer-based cascade control, the results of a comparison between the PV system with observer (without DC voltage sensor) and a PV system with DC voltage sensor (without observer) are presented. A suitable PV power estimation with the nonlinear observer-based cascade control is achieved, which allowing a good performance of the MPPT algorithms. Perturb & Observe and Incremental Conductance MPPT algorithms were used.

Keywords

• dc-ac power converters
• maximum power point trackers
• linear matrix inequalities
• observers
• takagi-sugeno model