Control Systems of Single-Phase Voltage Source Inverters for a UPS

This article presents considerations of the effectiveness of suppressing output voltage distortions of low power single-phase voltage source inverters (VSI) dedicated for UPS systems working with the nonlinear rectifier RC load defined in the EN 62040-3 standard. Various types of control systems were tested – PID/CDM and deadbeat instantaneous controllers designed using the author's discrete model (including the design of the output filter) of VSI and the fuzzy controller. It was shown that the additional control loop with the repetitive controller or additional input variables (currents) of the controller should be used for lowering the THD of the output voltage for the nonlinear load. The results of the experimental verification are shown.