Control of Active Front-End inverter During Asymmetrical Grid Faults

Inhalt:
Back-to-back converters are able to feed electric energy into the grid and are an interesting popular solution for electric drive controls. Higher dynamic performance as well as improved efficiency by recovery of braking energy are popular features. Especially for renewable energy sources like wind energy the active front-end inverter is needed to feed the energy into the grid. The control of the active front-end must regulate the dc-link voltage. If there are asymmetrical three phase voltages in the grid the conventional DC-link control produces poor results. In this paper a new control strategy of the operation of back-to-back converters is presented. A new coordinate transformation is used to increase performance of the control in case of asymmetrical grid voltages. The new control scheme is tested in simulations and measurements on a test stand.