Observer-Based Adaptive Control for Single-Phase UPS Inverter Under Nonlinear Load

Abstract

This article proposed a current-sensorless control scheme for the single-phase uninterruptible power supply (UPS) inverter under nonlinear load. Different from the existing current-sensorless literature, the information of load current can be obtained by the designed adaptive laws. It is meaningful for the system’s security and reliability. Under the assumption that the load is a periodic ideal-independent current source, the Fourier series in trigonometric form is expanded to model the unknown disturbance of load current. The observer-based feedback control rate and update laws are derived to adjust online the Fourier coefficients of the load current modeling. Furthermore, the stability of the system is rigorously analyzed via the Lyapunov approach. Under the same limitation of not using the current sensor, comparative experiments are designed. Simulation and experimental results have verified the effectiveness of the control approaches.