SLIDING MODE CONTROL FOR IMPROVED STABILITY AND DISTURBANCE REJECTION IN RING BUS CONFIGURED MICROGRIDS

摘要

The increasing use of distributed energy resources has motivated the development of microgrid structures to improve the reliability of electric power distribution systems. However, as microgrids become more complex, there is increased occurrence for instabilities being induced through cascaded interconnections of multiple ac-ac converters. In particular, it has been found that back-back ac-ac converters have degraded stability margins when connected in a ringbus configuration when compared to a radial configuration. This research investigates a sliding mode control technique to stabilize the voltage levels throughout a microgrid ring-bus. A method for analyzing a microgrid with multiple interconnected converters is presented. This includes identifying the participation factors of the voltage control inputs of each converter. The system is then linearized and a sliding mode controller is designed using subspace methods. The controller design is then evaluated by application to a previously validated simulation model of the 6 MVA microgrid operated at the National Center for Reliable Electric Power Transmission at the University of Arkansas. Results confirm the benefits of the sliding mode controller for improving the voltage regulation and disturbance rejection in a ring-bus configured microgrid.