Detailed analysis of closed-loop control of output-voltage harmonics in voltage-source inverters

Abstract

The design and application of selective controllers for voltage-source-inverter output control in single-phase and three-phase applications are investigated. It is shown how this type of controller can be used (a) to minimise the effects of the inverter dead times on output-voltage harmonics and (b) to provide flexible control of the inverter low-frequency output-voltage harmonics. The closed-loop stability of the resulting systems is investigated thoroughly and the controller design process is explained from the frequency-response viewpoint where stability margins can be designed explicitly. It is clearly demonstrated that a compromise has to be reached between transient-response speed and tracking (or rejection) accuracy. The main contributions are illustrated with a three-phase prototype, in which the two applications proposed for this type of controller are tested.