Dynamic Stiffness-Based Control for a MicroGrid Microsource Interface

Intermittent renewable microsources in so-called MicroGrids will need to have plug-and-play functionality, therefore, will need to be integrated with local storage. The design of such cross-coupled nonlinear systems is complex and presently focuses on command tracking dynamics. In practice, the robustness of such systems to external disturbance inputs plays at least an equal role. This paper presents the dynamic stiffness methodology for such design and illustrates it for a single-phase photovoltaic microsource with battery energy storage. While this method has been applied with considerable success in motor drives (converter plus single load) and uninterruptible power systems (converter plus energy storage), it has not so far been applied to the more complex case considered here of a microsource with embedded storage (converter plus energy source plus storage). The mathematical model of the system is derived and presented in state feedback block diagrams whereby local and global external disturbances and cross-coupling are clearly identified. The resulting system is clearly able to prevent the propagation of external disturbances from one end to the other. Experimental results are provided to validate the operation of the proposed controller.