ANALYSIS OF HIERARCHICAL CONTROL IN A DC MICROGRID WITH DROOP STRATEGY APPLIED TO A FRONT-END DC-AC CONVERTER TO REGULATE DC BUS VOLTAGE

This work investigates the influence of a droop control approach implemented to a front-end DC-AC converter con-nected to a DC microgrid. Distributed energy systems operating in a DC microgrid structure have been gaining traction recently, mainly due to the simplification process in the integration of renewable generation and energy storage systems. One of the most common strategies to guarantee proper operation of these structures is the droop control, which presents relatively easy implementation, enables microgrid coordination and also DC bus voltage regulation. However, the droop method lacks robustness and can present errors when lines between the terminals have non negligible impedances. This drawback can be mitigated with hierarchical control topologies. In addition to the aforementioned strategies, front-end DC-AC converters are also capable of contributing with DC bus voltage regulation if provided with proper droop strategy. To the best of the authors knowledge, this type of control has not been thoroughly explored, though. To partially fill this gap, the authors implemented a DC microgrid model in software environment, considering line cable impedances between units. In the front-end converter, the droop strategy is em-ployed using the synchronous reference frame technique. Simulation results are presented to illustrate the influence of the control developed for the front-end converter in the performance of the microgrid, focusing on the primary and secondary responses. A comparison with the operation regimen under the most common control approach found in literature is also reported.