Frequency Stability of Hierarchically Controlled Hybrid Photovoltaic-Battery-Hydropower Microgrids

Hybrid photovolvaic-battery-hydropower microgrids can increase electricity accessibility and availability in remote areas. In those microgrids with grid-connected and islanded modes capabilities, seamless transition between both modes is needed as well. However, the different resources with conventional constant P/Q and P/V controls coexisting in the microgrid may affect frequency stability. In this paper, a hierarchical control is proposed to perform power sharing among PV voltage source inverters (VSIs), while injecting the dispatched power to the main grid. Further, frequency stability analysis is presented based on small signal models of the hybrid PV-HP microgrid, including 2 MWp PV station, 15.2 MWh battery storage system, and 12.8 MVA hydropower plant. Simulation results of the microgrid and experimental results on a scaled-down laboratory prototype verify the effectiveness of the proposed hierarchical controller.