Improved Delay Compensation in Communication-based Hierarchical Control of a Low Voltage 3-phase AC Microgrid using a Secondary Control based on Smith Predictor

This paper proposes a microgrid (MG) hierarchical control with improved dynamic behavior aim for the integration of prosumer buildings in the utility grid with reduced impact. The study is focused on the implementation of enhanced secondary and tertiary controllers in a multi-building Low Voltage (LV) MG considering in-building loads, generation and energy storage. Both islanding and grid-tied operations are considered. In island mode, a fast voltage and frequency restoration becomes a critical issue to ensure a proper power sharing within the rated power values of the MG and to reduce the power losses in the MG lines. In grid-connected mode, the MG should be able to share power with the distribution grid. In both cases, the proper operation of the MG is achieved by centralized controllers that coordinates the entities in the MG. The dependency on communication channels in this kind of hierarchical control systems implies a well-known dynamic control limitation when pursuing a fast response in this application. A robust centralized secondary/tertiary control scheme is proposed based on communication delays compensation that allows for a rapid nominal values restoration in the MG and a fast power sharing response with the distribution system. Under the conditions taken in this paper, the secondary control settling time has been substantially reduced from 20 s to 2.5 s, which also enable faster tertiary control.